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  • Long-term observations of black carbon aerosol over a rural location in southern peninsular India: Role of dynamics and meteorology
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-15
    V. Ravi Kiran, S. Talukdar, M. Venkat Ratnam, A. Jayaraman

    Ten years (2008–2017) of Black Carbon (BC) observations obtained using Aethalometer (AE-37) are analyzed to investigate the seasonal trends and temporal variabilities over a tropical site Gadanki (13.5oN, 79.2oE) located in south-east India. Diurnal variations of BC have two peak structures one in the morning (∼08 IST) in all seasons and second in the evening (∼20 IST) only during the pre-monsoon (March–May). Intra-annual variation in BC indicated February and March months as the bio-mass burning with highest BC mass concentration (3000–5000 ng/m3). About 46% of air parcel back trajectories found passing across the in-land regions of southern peninsular India brining transported aerosol to the source location during pre-monsoon. The lowest BC (∼1500 ng/m3) is noticed during the monsoon months (June–September). The average BC (2200 ng/m3) represents observational site as a typical rural site. The inter-annual variability of BC did not show any significant trend. However, trends in the maximum (March) and minimum (July) BC values show statistically significant decreasing trend suggesting reduction in bio-mass burning sources during March supported by the decrease in the fire counts. Diurnal variation in the absorption angstrom exponent indicates that the morning and evening peaks are contributed by the bio-mass combustion with values above threshold of 1. However, angstrom exponent values are found below 1 during noon time of monsoon season suggesting fossil fuel contribution. Strong coupling is found between aerosol concentration and tropospheric dynamics, meteorology in addition to the sources. The present study is expected to provide valuable input to the modelers and observational physicists as BC is climate sensitive variable.

    更新日期:2018-06-15
  • Role of dynamics on the formation and maintenance of the elevated aerosol layer during monsoon season over south-east peninsular India
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-15
    M. Venkat Ratnam, P. Prasad, M. Roja Raman, V. Ravikiran, S. Vijaya Bhaskara Rao, B.V. Krishna Murthy, A. Jayaraman

    The existence of elevated aerosol layer is common over India during monsoon season. Though its sources are well explained through long-range transport, its formation and maintenance is not explained to date. The formation and maintenances of an elevated aerosol layer, starting from ∼2 km and extending up to ∼5.5 km noticed is explained using two nearby lidars located in peninsular India. Existence of a cleaner environment with low aerosol loading below 2 km is attributed to the wet scavenging and existence of no strong local source. The low level jet (LLJ) from Arabian Sea persisting between 2 and 3 km is the main mechanism suggesting strong role of dynamics in the formation of these elevated layers. Persistent strong shears existing between LLJ and tropical easterly jet during this season restrict the up-liftment of aerosols to the higher altitudes. Observed features are explained in the light of dynamics, meteorology and long-range transport.

    更新日期:2018-06-15
  • Reactive uptake of ammonia by secondary organic aerosols: Implications for air quality
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-15
    Jeremy R. Horne, Shupeng Zhu, Julia Montoya-Aguilera, Mallory L. Hinks, Lisa M. Wingen, Sergey A. Nizkorodov, Donald Dabdub

    Reactions between ammonia (NH3) and organic compounds containing carbonyl functional groups in aerosol particles can form organic products that are less basic than NH3 and are thus unable to neutralize efficiently nitric and sulfuric acids. In this exploratory study, the University of California, Irvine - California Institute of Technology (UCI-CIT) model is used to investigate the potential air quality impacts of including of the chemical uptake of NH3 by secondary organic aerosols (SOA) in a regional airshed model. A surface reaction of NH3 with SOA is implemented into the model to determine the impact of this process on NH3 and PM2.5 concentrations in the South Coast Air Basin of California (SoCAB). Air quality simulations are conducted using uptake coefficients ranging from 10−5 to 10−2 to explore the sensitivity of changes in NH3 and PM2.5 concentrations to the magnitude of the uptake coefficient. Results indicate that the chemical uptake of NH3 by SOA can potentially deplete gaseous NH3 concentrations, causing indirect reductions in the amount of ammonium nitrate and ammonium sulfate in particulate matter. The magnitude of the impact on NH3 and PM2.5 concentrations exhibits a strong but non-linear dependence on the value of the uptake coefficient, with evidence for small but notable impacts on air quality even with the lowest assumed uptake coefficient of 10−5.

    更新日期:2018-06-15
  • Nighttime particle growth observed during spring in New Delhi: Evidence for the aqueous phase oxidation of SO2
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-13
    Bighnaraj Sarangi, Shankar G. Aggarwal, Bhagawati Kunwar, Sudhanshu Kumar, Ravleen Kaur, Deepak Sinha, Suresh Tiwari, Kimitaka Kawamura

    Aerosol size distributions were measured using a scanning mobility particle sizer (SMPS), and also PM1 (particulate matter ≤ 1 μm in aerodynamic diameter) samples were collected in parallel at a representative site in New Delhi during spring in 2013 and 2014. Based on the temporal variation of particle count mean diameter (CMD), sampling periods are characterized as growth events and non-growth events. Particle size distribution measurements suggest that some consecutive nights experienced unique nighttime subsequent growth of particles, which sustained for a longer period. Average particle growth rate measured during growth events was 5.64 ± 3.03 nm h−1. Atmospheric trace gas concentrations and meteorological data show that these growth events (nighttime) are influenced by higher concentrations of gases, e.g., NO2 (56.5 ± 29.7 μg m−3), SO2 (9.34 ± 1.14 μg m−3) and RH (45.7 ± 9.5%) than those of non-growth events (daytime) (37.9 ± 18.6 μg m−3, 7.19 ± 2.08 μg m−3 and 37.7 ± 6.9%, respectively). Further, analysis of PM1 samples collected during the study period shows that the particulate water-soluble organic carbon (WSOC) (12.7 ± 4.1 μg m−3), NH4+ (9.4 ± 3.2 μg m−3), SO42− (2.03 ± 0.70 μg m−3), K+(1.06 ± 0.40 μg m−3), and NO2− + NO3− (0.59 ± 0.36 μg m−3) are the major contributor of particulate mass, wherein NH4+, SO42−, K+, NO2− + NO3− mass concentrations were higher during growth events. Correlation study shows that nighttime aerosol composition during growth (in sub-micron range) events are more enriched by inorganic species (i.e., NH4NO3, (NH4)2SO4 and H2SO4 vapors) as compared to organics (i.e., WSOC, does not show much difference in growth events and non events). Our results suggest that nighttime sulfate formation at the site is mostly mediated by high NO2 and NH3 at elevated RH. For the formation of sulfate and other inorganic species, a nighttime atmospheric chemistry is proposed, which is linked to particle growth. Growth events observed typically in nighttime have both biomass burning and anthropogenic influences as indicated by high concentrations of WSOC, K+ and black carbon in PM1 and carbon monoxide in gas phase.

    更新日期:2018-06-14
  • Impact of particulate matter on basmati rice varieties grown in Indo-Gangetic Plains of India: Growth, biochemical, physiological and yield attributes
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-13
    U. Mina, T.K. Chandrashekara, S. Naresh Kumar, M.C. Meena, S. Yadav, S. Tiwari, Deepak Singh, Pranav Kumar, Ram Kumar
    更新日期:2018-06-14
  • Oxidative potential of ambient particulate matter in Beirut during Saharan and Arabian dust events
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-13
    Christopher Lovett, Mohammad H. Sowlat, Najat A. Saliba, Alan L. Shihadeh, Constantinos Sioutas

    In this study, we examine the oxidative potential of airborne particulate matter (PM) in Beirut, Lebanon, as influenced by dust events originating in the Sahara and Arabian deserts. Segregated fine (<2.5 μm) and coarse (2.5–10 μm) PM samples collected during dust events, as well as during non-dust periods, were analyzed for chemical composition, and an in vitro alveolar macrophage (AM) assay was performed to determine the oxidative potential of both types of samples. We performed Spearman rank-order correlation analysis between individual chemical components and the oxidative potential of PM to examine the impact of the changes in PM chemical composition due to the occurrence of dust events on overall PM oxidative potential. Our findings revealed that the oxidative potential of Beirut's urban PM during non-dust periods was much higher than during dust episodes for fine PM. Our findings also indicated that tracers of tailpipe emissions (i.e., elemental (EC) and organic carbon (OC)), non-tailpipe emissions (i.e., heavy metals including Cu, Zn, As, Cd, and Pb), and secondary organic aerosols (SOA) (i.e., water-soluble organic carbon, WSOC) are significantly associated with the oxidative potential of PM during dust days and non-dust periods. However, the contribution of desert dust aerosols to Beirut's indigenous PM composition did not exacerbate its oxidative potential, as indicated by the negative correlations between the oxidative potential of PM and the concentrations of crustal elements that were enriched during the dust days. This suggests that aerosols generated during Saharan and Arabian dust events pose no additional health risk to the population due to PM-triggered reactive oxygen species formation. These results significantly contribute to our understanding of the effects of desert dust aerosols on the composition and oxidative potential of PM in several countries throughout the entire Middle East region that are impacted by dust events in the Sahara and Arabian deserts.

    更新日期:2018-06-13
  • Aerosol Optical Depth variability over the Arabian Peninsula as inferred from satellite measurements
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-08
    K. Ravi Kumar, Raju Attada, Hari Prasad Dasari, Ramesh K. Vellore, Sabique Langdon, Yasser O. Abualnaja, Ibrahim Hoteit

    Aerosol abundance from widespread deserts over the Arabian Peninsula (AP) plays an important role in the regional climate and air quality. This study investigates the spatio-temporal variability of Aerosol Optical Depth (AOD) ranging from seasonal to inter-annual time scales during the period 2003–2016 using satellite retrievals from MISR and MODIS, together with ground-based observations from the Aerosol Robotic Network (AERONET) available during the period 2003–2012 over the AP. The MODIS AOD (MISR AOD) observations exhibit 0.81 and 0.85 (0.71 and 0.76) correlations with ground-based observations during the wet and dry seasons, respectively. The correlations were also found to be significant with respect to the surface monitoring station at Solar village in Saudi Arabia. Our observational analysis reveals higher (lower) concentrations of AOD during dry (wet) seasons over the AP. The observed AODs indicate similar spatial distributions over annual and seasonal time scales, with high AODs over the Southern Red sea (SR), and the Northeast AP, and lower AODs over the central and southern end of the AP. It is also observed that the AOD exhibits year-to-year variations over different sub-regions of the AP. Analyses of the inter-annual variability over the AP reveals a significant relationship between the AOD and El Niño-Southern Oscillation (ENSO) during the summertime. Furthermore, positive AOD anomalies over the AP can be closely linked with the intensification of the westerly jet at the Tokar Gap during La Niña phases. Enhanced monsoon associated heat low over the AP during La Niña phases further favors greater uplift and saltation of dust from desert regions.

    更新日期:2018-06-08
  • Time effects of high particulate events on the critical conversion point of ground-level ozone
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-06
    Norrimi Rosaida Awang, Nor Azam Ramli, Syabiha Shith, Noor Faizah Fitri Md Yusof, Nazatul Syadia Zainordin, Nurulilyana Sansuddin, Nurul Adyani Ghazali

    Particulate matter (PM), especially those with an aerodynamic particle size of less than 10 μm (PM10), is typically emitted from transboundary forest fires. A large-scale forest fire may contribute to a haze condition known as a high particulate event (HPE), which has affected Southeast Asia, particularly Peninsular Malaysia, for a long time. Such event can alter the photochemical reactions of secondary pollutants. This work investigates the influence of PM on ground-level ozone (O3) formation during HPE. Five continuous air quality monitoring stations from different site categories (i.e., industrial, urban and background) located across Peninsular Malaysia were selected in this study during the HPEs in 2013 and 2014. Result clearly indicated that O3 concentrations were significantly higher during HPE than during non-HPE in all the sites. The O3 diurnal variation in each site exhibited a similar pattern, whereas the magnitudes of variation during HPE and non-HPE differed. Light scattering and atmospheric attenuation were proven to be associated with HPE, which possibly affected O3 photochemical reactions during HPE. Critical conversion time was used as the main determining factor when comparing HPE and non-HPE conditions. A possible screening effect that resulted in the shifting of the critical transformation point caused a delay of approximately of 15–30 min. The shifting was possibly influenced by the attenuation of sunlight in the morning during HPE. A negative correlation between O3 and PM10 was observed during the HPE in Klang in 2013 and 2014, with −0.87. Essentially, HPE with a high PM concentration altered ground-level O3 formation.

    更新日期:2018-06-07
  • SOA and gas phase organic acid yields from the sequential photooxidation of seven monoterpenes
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-06
    Beth Friedman, Delphine K. Farmer

    We investigate secondary organic aerosol (SOA) and gas phase organic acid yields from the sequential photooxidation of seven monoterpene isomers (α-pinene, β-pinene, limonene, sabinene, terpinolene, α-terpinene, and γ-terpinene) using an Oxidative Flow Reactor under dry conditions. SOA yields were highest for terpinolene (33% at 5.7 days of aging), followed by sabinene, β-pinene, α-pinene, limonene, γ-terpinene, and α-terpinene. Isomers with exocyclic double bonds (i.e. immediately adjacent to a ring) had higher SOA yields than those with endocyclic double bonds, or with double bonds that are unattached to a ring structure. SOA yields increased with OH exposure, highlighting the limitation of using single values for SOA yield in modeling studies, and the need for isomer-specific SOA parameterizations. SOA yields were adequately fit by a one-product model and in broad agreement with previous studies. SOA yields linearly increased with organic aerosol mass concentration, possibly the result of high OH loading and short residence times in the flow reactor. Gas phase yields of formic, acetic, butyric, and methacrylic acid (or their isomers) followed very different patterns as a function of OH exposure from SOA yields, and were poorly correlated with OH rate constants. These observations suggest that higher volatility (fragmentation) products of monoterpene photooxidation were produced and lost on different timescales from the production and condensation of lower-volatility (functionalization) products. Formic acid yields ranged from 0.06 to 9.3% across all OH exposures. Formic acid yields from γ-terpinene (0.36–3%) monotonically increased with OH exposure, unlike the other monoterpene isomers, which exhibited initial increases in formic acid yields with OH exposure, followed by decreases at higher OH concentrations. This difference in organic acid yield trends is consistent with the distribution of carbon-containing species identified by chemical ionization mass spectrometry.

    更新日期:2018-06-07
  • Iron dissolution and speciation in atmospheric mineral dust: Metal-metal synergistic and antagonistic effects
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-06
    Eshani Hettiarachchi, Richard L. Reynolds, Harland L. Goldstein, Bruce Moskowitz, Gayan Rubasinghege
    更新日期:2018-06-06
  • Urban residential indoor volatile organic compounds in summer, Beijing: profile, concentration and source characterization
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-05
    Lihui Huang, Hui Qian, Shunxi Deng, Jifeng Guo, Yanpeng Li, Weiping Zhao, Yang Yue

    Residential indoor exposure to volatile organic compounds (VOCs) is a major public health concern. However, the relevant pollution sources have not been well characterized in China. In this study, the 24-h integrated concentrations of 55 VOC species in 27 urban residences, Beijing were measured in the summer. The sources were characterized with positive matrix factorization (PMF) and general linear model (GLM). The most abundant species in terms of geometric mean concentration were formaldehyde (55.1 μg/m3), acetaldehyde (18.7 μg/m3), acetone (14.8 μg/m3), toluene (14.1 μg/m3), hexanal (13.8 μg/m3), n-hexadecane (8.9 μg/m3) and n-pentadecane (8.5 μg/m3). PMF generated 7 factors associated with VOC sources, including aldehydes from ozone-initiated secondary reactions, butyraldehyde from hydrolysis of building materials and furniture, wood flooring emission, wooden furniture emission, wall coverings emission, mobile emission and halogenated hydrocarbons of miscellaneous outdoor origin. GLM identified leather sofa as another source of indoor terpenes and formaldehyde. GLM also found composite wood flooring had stronger emission of VOCs than solid wood flooring, except 1,4-dichlorobenzene. A comparison with multiple studies across the world suggested that: (1) more intensive ozone-initiated secondary reactions resulted in the significantly higher indoor carbonyl concentrations in Beijing than in Japan and USA in the summer; (2) the indoor concentrations of benzene and C12-C17 alkanes were much higher in Beijing, due to the traffic conditions and prevalent use of wood flooring varnishing.

    更新日期:2018-06-06
  • Heterogeneous reaction of Cl2 and NO2 on γ-Al2O3: A potential formation pathway of secondary aerosols
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-05
    Siqun Tang, Lingling Ma, Min Luo, Zhaohui Zhang, Xingzhong Cao, Zhenling Huang, Rui Xia, Ye Qiu, Shuo Feng, Peng Zhang, Chuanqin Xia, Yongdong Jin, Diandou Xu
    更新日期:2018-06-05
  • 更新日期:2018-06-05
  • Winter air pollution by and inhalation exposure to nitrated and oxygenated PAHs in rural Shanxi, north China
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-04
    Wei Du, Yuanchen Chen, Guofeng Shen, Wei Wang, Shaojie Zhuo, Ye Huang, Xuelian Pan, Shu Tao
    更新日期:2018-06-05
  • Large methane emissions from natural gas vehicles in Chinese cities
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-04
    Ning Hu, Shoudong Liu, Yunqiu Gao, Jiaping Xu, Xue Zhang, Zhen Zhang, Xuhui Lee

    In recent years, cities in developing countries have become more and more reliant on natural gas as a clean energy source for transportation to reduce air pollution. In this study, we used street-level measurement of atmospheric CH4 and CO2 concentrations to quantify CH4 emissions from natural gas vehicles (NGVs) in China. These measurements were made in eight cities (Chengdu, Urumqi, Jinan, Nanjing, Lanzhou, Harbin, Guangzhou) with varying sizes of NGV fleet. A traffic CH4:CO2 emission ratio (TER) was determined via linear regression of CH4 versus CO2 concentration data obtained from each street transect. The TER value was combined with the ratio of NGVs in the street traffic in a mathematical model to obtain the CH4 emission factor for NGVs. Results show that the TER increases with increasing NGV ratio and decreases with increasing traffic speed. Overall, the NGV CH4 emission factor in these cities is 0.022 ± 0.0033 kg m−3, about 8 times the Intergovernmental Panel on Climate Change (IPCC) default factor for NGVs and is more than 100% higher than the mean NGV tailpipe emission factor found in the published literature. That the overall emission factor is much larger than the tailpipe emission factor indicates that on-road vehicle gas leakage is a widespread problem. A business-as-usual scenario suggests that NGVs may emit 1.23 Tg CH4 yr−1 in 2030, or about 3% of China's current total anthropogenic emission. Our study suggest that curbing the emissions from this sector should be a high priority for global climate mitigation efforts.

    更新日期:2018-06-05
  • Evaluation of mineral dust aerosol optical depth and related components from the CHIMERE-DUST model using satellite remote sensing and ground-based observations
    Atmos. Environ. (IF 3.629) Pub Date : 2018-03-30
    Yiwen Xu

    Dust aerosol optical depth (AOD) simulated by the CHIMERE-DUST model over North Africa during 2006–2008 was evaluated by the SeaWiFS Deep Blue satellite data and AERONET ground based remote sensing measurements. The simulations were conducted using two meteorological inputs, ECMWF and CFSR forecast data, downscaled by the WRF model. The two simulations generated similar AODs and PM10 surface concentrations, which are highly correlated to dust emissions. The comparison of the simulated daily value of AOD with the satellite data showed good correlations (0.6–0.8) between them. A slightly better correlation was achieved using WRF-CFSR data. The regression coefficients fluctuated around 1.0 in cold months and decreased in summer, with minimums in August. The biases had similar seasonal cycles. This is consistent with the comparison against AERONET hourly AOD data that the model underestimated AODs in warm months at most stations. The comparison of PM10 surface concentration and dry deposition also showed negative biases in warm months at stations in the Sahel. The significant underestimation of wet deposition was found in monsoon season due to the unrealistic simulation of mesoscale convective system. It indicates that the low dust emission in August is partly associated with cold pools generated by the convective precipitation. Frequent overestimations of AOD were found in the northwest mostly because of the high dust emission produced by the overestimated winds near the Atlas Mountains. The dust emissions resulted from the two simulations were similar in terms of intra annual variations but differed in terms of annul dust emission. The estimated annual emission using WRF-CFSR data could be about 200 Tg more than the estimation using WRF-ECMWF data.

    更新日期:2018-06-03
  • Spatially varying parameter estimation for dust emissions using reduced-tangent-linearization 4DVar
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-02
    Jianbing Jin, Hai Xiang Lin, Arnold Heemink, Arjo Segers

    In previous studies, a number of model-based dust forecasts and early warning systems have been developed for the prevention of environmental impacts due to dusts. However, the accuracy of the model is limited by imperfect identification of dust emissions, in particular by the friction velocity threshold parameterization in the emission process. In this study, an integrated dust storm forecast system - LOTOS-EUROS/Dust coupled with reduced-tangent-linearization 4DVar data assimilation has been developed. In order to overcome the inflexibility and inaccuracy of the existing friction velocity threshold parameterization in large-scale models, a spatially varying multiplicative factor for the threshold is introduced. This parameter is estimated by assimilating measurements from a field station network developed by China Ministry of Environmental Protection. The data assimilation algorithm is adjoint-free, and its computational complexity increases with the number of uncertain parameters. Two model reducing techniques, sensitivity-based parameter filters and proper orthogonal decomposition, are sequentially implemented after each other, which lead to a reduction of parameter dimension from initially O(104) O ( 10 4 ) to O(102) O ( 10 2 ) . Twin experiments are conducted to evaluate the impact of assimilation settings on the dust forecast accuracy. In addition, experiments with real observations are conducted. However, these observations also reflect the aerosol concentration from local emissions. To effectively use these observations as representative for dust concentrations, an observation bias correction and a variable representation error are designed. Improvements on the dust storm forecast with our system are demonstrated.

    更新日期:2018-06-02
  • 更新日期:2018-06-02
  • Seasonal light absorption properties of water-soluble brown carbon in atmospheric fine particles in Nanjing, China
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-02
    Yanfang Chen, Xinlei Ge, Hui Chen, Xinchun Xie, Yuntao Chen, Junfeng Wang, Zhaolian Ye, Mengying Bao, Yanlin Zhang, Mindong Chen
    更新日期:2018-06-02
  • Impact of heterogeneous uptake of nitrogen dioxide on the conversion of acetaldehyde on gamma-alumina in the absence and presence of simulated solar irradiation
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-01
    Chengtian Du, Lingdong Kong, Assiya Zhanzakova, Songying Tong, Xin Yang, Lin Wang, Hongbo Fu, Tiantao Cheng, Jianmin Chen, Shicheng Zhang
    更新日期:2018-06-01
  • DMPSA and DMPP equally reduce N2O emissions from a maize-ryegrass forage rotation under Atlantic climate conditions
    Atmos. Environ. (IF 3.629) Pub Date : 2018-06-01
    Ximena Huérfano, José María Estavillo, Teresa Fuertes-Mendizábal, Fernando Torralbo, Carmen González-Murua, Sergio Menéndez
    更新日期:2018-06-01
  • Submicron ammonium sulfate particles deposited on leaf surfaces of a leafy vegetable (Komatsuna, Brassica rapa L. var. perviridis) are taken up by leaf and enhance nocturnal leaf conductance
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-30
    Akira Motai, Marina Yamazaki, Nana Muramatsu, Makoto Watanabe, Takeshi Izuta

    Ammonium sulfate (AS) particles of submicron size are a major component of inorganic aerosol, and are regarded as a long-range transboundary air pollutant in Asia. However, only a few studies have focused on the effects of submicron AS particles on plants. In the present study, we investigated the amount of submicron AS particles deposited on the leaf surface of komatsuna plants (Brassica rapa L. var. perviridis), and their effects on nocturnal leaf (gnight) and cuticular (gcut) conductance. The plants were grown for 23 days after sowing in a naturally lit phytotron at air temperature of 25.0 ± 1.0 °C/18.0 ± 1.0 °C (6:00–18:00/18:00–6:00) and relative air humidity of 70 ± 5%, and were artificially exposed to submicron AS particles at the 21st day after sowing. The exposure to submicron AS particles resulted in average daily atmospheric concentration of SO42− in PM2.5 inside the phytotron of 16.5 μg m−3. After the end of exposure, the plants were kept under light or dark conditions for 48 h in the phytotron. The amount of SO42− deposited on the leaf surface reduced over time, but did not significantly differ between the plants kept under light and dark conditions at 0, 6, 12, 18, 30, and 48 h after the end of exposure. An exposure to submicron AS particles with average daily atmospheric concentration of SO42− in PM2.5 inside the phytotron of 24.7 μg m−3 did not significantly affect the gcut of the plants. At 1.5 and 5 h after the end of exposure, the gnight was significantly higher in the submicron AS particle-exposed plants than in the non-exposed control plants. These results indicate that submicron AS particles deposited on the leaf surface enhance the nocturnal water consumption of komatsuna plants.

    更新日期:2018-05-31
  • Atmospheric stability characterization using the Pasquill method: A critical evaluation
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-30
    Jonathan D.W. Kahl, Hillary L. Chapman
    更新日期:2018-05-31
  • Short-term effect of tropospheric ozone on daily mortality in Spain
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-30
    Julio Díaz, Cristina Ortiz, Isabel Falcón, Coral Salvador, Cristina Linares

    Background Studies that seek to link the impact of ozone with mortality display a number of uncertainties. This study sought to ascertain the functional relationship between ozone and mortality, and analyse its short-term impact on daily natural-, respiratory- and circulatory-cause mortality in Spain. Methods We analysed data on daily natural- (ICD 10: A00-R99), respiratory- (ICD 10: J00-J99) and circulatory-cause mortality (ICD 10: I00-I99) for each of Spain's 52 provinces across the period 2000–2009. We calculated the impact of ozone on mortality by reference to relative risks (RRs) using generalised linear models, and performed an overall meta-analysis. Attributable mortality was calculated on the basis of RRs. Results A quadratic relationship was observed and the existence of a threshold value identified in 33 of the 46 monitoring stations judged to be valid for ozone data, this threshold value was located above the 80th percentile. The overall RRs for 10 μg/m3 increases in concentrations of the O3 threshold value were as follows: 1.033 (95%CI: 1.023–1.044) for natural causes; 1.089 (95%CI: 1.058–1.120) for respiratory causes; and 1.025 (95%CI: 1.018–1.033) for mortality circulatory causes. The annual total of natural-cause ozone-attributable deaths was 499 (95%CI: 277–717), 126 of which (95%CI: 54–194) were due to respiratory causes and 167 (95%CI: 39–293) to circulatory causes. Conclusions High ozone concentrations display a quadratic relationship with daily mortality. While this effect is more pronounced in respiratory causes, there is also a short-term effect on natural- and circulatory-cause mortality.

    更新日期:2018-05-31
  • High-resolution air quality modeling: Sensitivity tests to horizontal resolution and urban canopy with WRF-CHIMERE
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-31
    Serena Falasca, Gabriele Curci

    The European Directive (2008/50/EC) encourages the use of models in the assessment and forecasting of air quality, and assigns them a supporting or replacing role with respect to fixed ground-based measurements. A thorough knowledge of performance of the modeling tools over urban areas is therefore required. In this study, we analyze sensitivity tests with the WRF-CHIMERE modeling system in order to investigate the effect of (1) the horizontal model grid size, (2) the resolution of the anthropogenic emission inventory, and (3) the introduction of urban canopy models. The work focuses on L'Aquila and Milan, two Italian cities widely differing for the number of inhabitants, the extension and the geographical location. We found a clear advantage in increasing the model resolution up to ∼4 km, but a further increase at ∼1 km resolution does not seem to be justified. Moreover, we found that the ozone simulation is generally degraded at higher resolution. The introduction of a more detailed treatment of the urban canopy and of the anthropogenic emissions suggests the potential for further improvement, but this requires a fine tuning on the area of application. For example, the Building Environment Parameterization corrects the surface wind speed daily cycle, but it also increases the planetary boundary layer height, resulting in excessive dilution of primary pollutants. The anthropogenic emissions should be refined proportionally to the increase in dynamic model resolution, possibly through new bottom-up inventories, rather than through a downscaling of a coarser inventory. We suggest that future work should primarily focus on intensive campaign periods, where a comprehensive observational characterization of the three dimensional structure and evolution of the planetary boundary layer is available.

    更新日期:2018-05-31
  • Investigation of ambient aerosol effective density with and without using a catalytic stripper
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-29
    Yue Lin, Roya Bahreini, Stephen Zimmerman, Emmanuel A. Fofie, Akua Asa-Awuku, Kihong Park, Seung-Bok Lee, Gwi-Nam Bae, Heejung S. Jung

    Size-resolved effective densities of ambient aerosols in Riverside, CA were determined over 4 periods during 2015–2016. A DMA-CPMA-CPC technique was used to measure effective density for particles with selected diameters of 50, 70, 101 and 152 nm. A catalytic stripper (CS) was used alternately to remove the volatile fraction of aerosol before density measurements. Aerosol non-refractory composition measurement was conducted in June 2016 campaign to understand the effect of chemical composition on particle density. The average densities for particles over all the measurement campaigns over BP mode (i.e. bypassing the CS) were 1.17 g/cm3 at 50 nm and 1.25–1.28 g/cm3 at 70, 101 and 152 nm. The average density after CS conditioning (CS mode) showed a decreasing trend from 1.22 g/cm3 to 1.04 g/cm3, with increase in the selected size, and a mass fractal dimension (Df) of 2.85. Both the BP and CS mode particles showed the lowest effective density at 6–9 am and highest density at 11 am-3 pm. The diurnal variation of density for both modes became more intensive as particle size increased. The variation was also more intense for the CS mode compared to the BP mode. Organic aerosol and ammonium nitrate mass in the size range of density measurements correlated well positively (R2 = 0.78) and negatively (R2 = 0.62), respectively with BP mode effective density. The study provides an update to the aerosol density profiles of a well-known receptor site (Riverside, CA) and investigates the transformation of particles in different seasons. The effective density profiles will be used in a follow-up study to better estimate the respiratory-deposited ambient aerosol mass.

    更新日期:2018-05-30
  • The impact of NOx emissions from lightning on the production of aviation-induced ozone
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-28
    Arezoo Khodayari, Francis Vitt, Daniel Phoenix, Donald J. Wuebbles

    Due to the non-linear nature of ozone production in the troposphere, ozone production as a function of aviation nitrogen oxide (NOx = NO + NO2) emissions varies based on the background NOx levels. Of the several different sources of background NOx in the atmosphere, NOx from lightning (LNOx) contributes a substantial amount of NOx to the upper troposphere and has an effect on the ozone production efficiency, even though the LNOx source still has significant uncertainty. In this study, CAM5, the atmospheric component of the Community Earth System Model (CESM), was used to study the effect of uncertainties in NOx emissions from lightning on the production of aviation-induced ozone. Three sensitivity studies were analyzed with varying LNOx values of 3.7, 5, and 7.4 TgN/yr, representing the best current range estimates for LNOx. Results show a decrease in the aviation-induced ozone production rate and radiative forcing (RF) as LNOx increases. This is tied to the decreased ozone production under NOx saturated conditions. The ozone production per unit of NOx emission from lightning ranges from 2.38 TgO3/TgN for the case with 3.7 TgN from lightning to 0.97 TgO3/TgN for the case with 7.4 TgN from lightning. Similarly, the O3 RF decreases from 43.9 mW/m2 for the 3.7 TgN/yr case to 34.3 mW/m2 for 7.4 TgN/yr case. Understanding the current sensitivity of aviation-induced ozone production to the LNOx strength is important for reducing the uncertainty in ozone production from aviation NOx emissions.

    更新日期:2018-05-29
  • Oxidative potential of size-segregated PM in a urban and an industrial area of Italy
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-28
    Giulia Simonetti, Elena Conte, Cinzia Perrino, Silvia Canepari

    This work is focused on the relationship between the size distribution of some source tracers of atmospheric particulate matter (PM) and the oxidative potential (OP) of each PM size fraction. Size-segregated PM samples were collected by a multistage impactor (cut-sizes: 0.18, 0.32, 0.56, 1.0, 1.8, 3.2, 5.6, 10 and 18 μm) in two geographical areas of Italy (Rome and Ferrara), characterized by different strength of the main PM sources. The samples were analysed by three different acellular OP methods: dithiothreitol (DTT), dichlorofluorescein diacetate (DCFH) and ascorbate (AA) assay. Elemental (Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Nb, Mo, Cd, Sn, Sb, Te, Cs, Ba, La, Ce, W, Tl, Pb, Bi and U) and ionic (Cl−, NO3−, SO42-, Na+, NH4+, K+, Mg2+, Ca2+) composition of the same samples was also determined, in order to trace the contribution of the main PM sources. The size distribution of the OP values was compared to the size distribution of some PM source tracers, with the aim of identifying the PM sources that mostly influence the oxidative properties of atmospheric dust. AA assay resulted to be more sensitive towards coarse particles and OPAA showed a size distribution very similar to that of brake dust tracers. DTT and DCFH assays resulted instead more sensitive towards fine particles. OPDTT and OPDCFH values were comparable at the two sites; sources whose strength was very different in the two monitored areas (secondary contribution and, to a less extent, industrial sources) did not then contribute significantly to the measured OP values. The dimensional behaviour of OPDTT and OPDCFH was consistent with the contribution of biomass burning.

    更新日期:2018-05-29
  • Annual emissions of air toxics emitted from crop residue open burning in Southeast Asia over the period of 2010–2015
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-28
    Nguyen Thi Kim Oanh, Didin Agustian Permadi, Philip Hopke, Kirk Smith, Nguyen Phan Dong, Anh Nguyet Dang

    Southeast Asia (SEA) has large agricultural crop production and huge amounts of crop residues generated annually are commonly burned in the field to quickly clear land for the next crop planting. This study developed annual emission inventory for crop residue open burning (CROB) covering 17 emission species/groups for 10 SEA countries during 2010–2015, illustrated with relative contributions by country and by crop type. The fractions of crop residue subjected to open burning (OB), a large source of uncertainty in the activity data, compiled from surveys in SEA were significantly higher than those suggested in international databases. Emission factors for rice and maize residue OB were obtained from field experiments conducted in Thailand. The best estimates of the annual emissions averaged over 6 years, of air toxics were: 32 Gg of polycyclic aromatic hydrocarbons, 0.03 Gg organo-chlorinated pesticides, 292 Gg total chlorines, and 94 g I-TEQ dioxins. Emissions of PM2.5, BC and OC, in Tg yr−1, were respectively 1.8, 0.08 and 0.8. The coefficients of variation of annual emissions during the period were relatively small (2.6–8.6% depending on species) but still showed an increasing trend that reflected the changes in production of major crops during the period. Regionally, CROB shared 10–43% of the total biomass open burning emissions but varying with country: by far dominant in Vietnam and Philippines, and much less dominant in Indonesia, Myanmar, and Thailand. Rice straw open burning was the most dominant (19–97%) in the total CROB emissions of the 8 considered crops. The spatial distributions of annual emissions (0.1° x 0.1°) showed higher emission intensity over the areas cultivated with rice and sugarcane, while higher monthly emissions coincided with major harvesting periods in the dry season. The obtained EI data can be further used for air quality modeling to assess effects of CROB emission and to promote non-OB alternatives in the region.

    更新日期:2018-05-29
  • Temporal variations in the distribution and sea-to-air flux of marine isoprene in the East China Sea
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-28
    Jian–Long Li, Xing Zhai, Hong–Hai Zhang, Gui–Peng Yang

    Marine isoprene concentrations in the East China Sea were measured during two oceanographic cruises: one from October 10, 2013 to November 21, 2013 and another from May 16, 2014 to June 13, 2014. Mean (range) isoprene concentrations in the surface water in the study area were 32.85 (16.31–108.2) pmol L−1 in late spring and 26.83 (11.22–42.13) pmol L−1 in autumn. The isoprene concentrations showed seasonal variation and were higher in late spring, which could be attributable to terrigenous diluted water and seasonal variations of phytoplankton structure. Isoprene and chlorophyll a (Chl-a) concentrations were significantly correlated in late spring and autumn even under complex hydrographic conditions. Isoprene and Chl-a concentrations also exhibited similar variations during a 25 h period and remained high during daytime. Analysis of depth profiles indicated that isoprene concentrations in the water column peaked at the surface layer and gradually decreased with increasing depth. The atmospheric concentration of isoprene (average: 53.4 ppt; range: 14.8–141 ppt) was high in the onshore area but low in the offshore area in late spring. The mean sea-to-air fluxes of isoprene in the East China Sea were 36.12 (late spring) and 48.34 (autumn) nmol m−2 d−1. Results revealed the substantial isoprene emission from surface seawater, which was also a net source of atmospheric isoprene during the study period.

    更新日期:2018-05-29
  • A novel regression imputation framework for Tehran air pollution monitoring network using outputs from WRF and CAMx models
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-28
    Hossein Shahbazi, Sajjad Karimi, Vahid Hosseini, Daniel Yazgi, Sara Torbatian

    Missing or incomplete data in short or long intervals is a common problem in measuring air pollution. Severe issues may arise when dealing with missing data for time-series prediction schemes or mean analysis. This study aimed to develop a new regression imputation framework to impute missing values in the hourly air quality data set of Tehran and enhance the applicability of Tehran Air Pollution Forecasting System (TAPFS). The proposed framework was designed based on three types of features including measurements of other stations, WRF and CAMx physical models. In this framework, elastic net and neuro-fuzzy networks were efficiently combined in a two-layer structure. The framework was applied on Tehran's air pollution monitoring network. The hourly imputing results of the suggested method were seen to be superior to existing methods according to statistical criteria such as RMSE, MAE and R-values. Average R-values of 0.88, 0.73, 0.76 and 0.81 were obtained for O3, NO, PM2.5 and PM10, respectively. The measurements of other stations had the main predictive power with a modest increase for the two physical models. The benefit of the models was somewhat higher for stations on boundaries of monitoring network. In addition, the central stations had better performance than the boundary stations and an approximately 0.05 increase was obtained in average R-value.

    更新日期:2018-05-29
  • PM2.5 source allocation in European cities: A SHERPA modelling study
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-29
    P. Thunis, B. Degraeuwe, E. Pisoni, M. Trombetti, E. Peduzzi, C.A. Belis, J. Wilson, A. Clappier, E. Vignati

    Many European cities suffer from poor air quality and still exceed the European standards prescribed by the Air Quality Directive, and the guidelines recommended by the World Health Organization (WHO). This is especially the case for PM2.5, focus of this work. While international, national and local level actions to reduce air pollution have undoubtedly resulted in an overall improvement of the air quality over the years, there are still problems, which are localised in specific regions and many cities. A key issue is to determine at which scale to act in order to abate these remaining air pollution problems most effectively. Central to this, for cities, is a quantitative assessment of the different origins of air pollution (urban, regional, national and transboundary) to support the design of efficient, effective air quality plans, which are a legal obligation for countries and regions whenever exceedances occur. The “Screening for High Emission Reduction Potentials for Air quality” tool (SHERPA) is used in this work to quantify the origins of air pollution in cities and regions, both from a spatial (urban, country…) and sectoral (transport, residential, agriculture…) perspectives. For PM2.5 we conclude that (1) for many cities, local actions at the city scale are an effective means of improving air quality in that city; (2) the target sectors and scales to abate air pollution are city specific, even for cities that are located in the same country. Consequently, it is important to take into account these city-specific circumstances when designing air quality plans and (3) for many cities, sectoral measures addressing agriculture at country or EU scale would have a clear benefit on urban air quality.

    更新日期:2018-05-29
  • Ammonia emissions from biomass burning in the continental United States
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-29
    Casey D. Bray, William Battye, Viney P. Aneja, Daniel Q. Tong, Pius Lee, Youhua Tang

    This study quantifies ammonia (NH3) emissions from biomass burning from 2005 to 2015 across the continental US (CONUS) and compares emissions from biomass burning with the US Environmental Protection Agency (EPA) National Emissions Inventory (NEI), the Fire Inventory from the National Center for Atmospheric Research (FINN) and the Global Fire Emissions Database (GFED). A statistical regression model was developed in order to predict NH3 emissions from biomass burning using a combination of fire properties and meteorological data. Satellite data were used to evaluate the annual fire strength and frequency as well as to calculate the total NH3 emissions across the CONUS. The results of this study showed the total fire number has decreased, while the total yearly burn area and the average fire radiative power has increased. The average annual NH3 emissions from biomass burning from this study, on a national scale, were approximately 5.4e8 ± 3.3e8 kg year−1. When comparing the results of this study with other emission inventories, it was found that ammonia emissions estimated by the NEI were approximately a factor of 1.3 lower than what was calculated in this study and a factor of 1.1 lower than what was modeled using the statistical regression model for 2010–2014. The calculated NH3 emissions from biomass burning were a factor of 5.9 and a factor of 13.1 higher than the emissions from FINN and the GFED, respectively. The modeled NH3 emissions from biomass burning were a factor of 5.0 and a factor of 11.1 higher than the emissions from FINN and the GFED, respectively. As the climate continues to change, the pattern (frequency, intensity and magnitude) of fires across the US will also change, leading to changes in NH3 emissions. The statistical regression model developed in this study will allow prediction of NH3 emissions associated with climate change.

    更新日期:2018-05-29
  • Numerical analysis of pollutant dispersion around elongated buildings: An embedded large eddy simulation approach
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-29
    H. Foroutan, W. Tang, D.K. Heist, S.G. Perry, L.H. Brouwer, E.M. Monbureau

    High fidelity, scale-resolving numerical simulations of flow and pollutant dispersion around several elongated isolated buildings are presented in this paper. The embedded large eddy simulation (ELES) is used to model flow and concentration fields for six test cases with various source-building geometries. Specifically, the influence of building aspect ratio, wind direction, and source location is examined with these cases. Results obtained from the present ELES model are evaluated using available wind tunnel measurements, including those of streamwise and spanwise velocities, turbulent kinetic energy, and streamwise, lateral, and spanwise pollutant concentrations. Comparisons indicate that the ELES provides realistic representations of the flow and concentration fields observed in wind tunnel experiments, and captures several complex phenomena including the lateral shift and enhanced descent of the plume for rotated/elongated buildings. Furthermore, the ELES provides a means to study the advective and turbulent concentration fluxes, plume shapes, and geometry of vortical structures that is used to examine turbulent transport of pollutants around buildings. We investigate the enhancement of vertical and lateral plume spread as the building aspect ratio is increased. In addition, through the study of advective and turbulent concentration fluxes, we shed light on the physics behind higher ground-level concentrations observed for rotated buildings.

    更新日期:2018-05-29
  • Impact on air quality of cruise ship emissions in Naples, Italy
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-29
    F. Murena, L. Mocerino, F. Quaranta, D. Toscano
    更新日期:2018-05-29
  • Air pollutant sinks on noise barriers: Where do they perform the best?
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-25
    Amitosh Dash, Gerrit E. Elsinga
    更新日期:2018-05-27
  • Parameterization of dust flux emitted by convective turbulent dust emission (CTDE) over the Horqin Sandy Land area
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-25
    Tingting Ju, Xiaolan Li, Hongsheng Zhang, Xuhui Cai, Yu Song

    A new convective turbulent dust emission (CTDE) empirical parameterization scheme was developed and validated using the observational data of dust concentrations and meteorological parameters over the Horqin Sandy Land area. Moreover, different CTDE schemes were compared and discussed. The statistical results from the observations in 2016 showed that the proportion of dust emission fluxes emitted by CTDE is 27% for all dust emission which indicates that the significance of CTDE events for the contribution of atmospheric dust aerosols. In addition, dust emission fluxes emitted by CTDE constituted up to 78% of the total dust emission due to direct aerodynamic entrainment, which verified that CTDE is indeed the most important and major form of aerodynamic entrainment dust emission. A new CTDE empirical parameterization scheme ( View the MathML source F m o d = 2.93 × w ∗ 1.5 , where w∗ w ∗ is the convective velocity scale), was established and validated based on nine typical CTDE events observed at the Horqin site in 2016, and the model predictions of the new CTDE scheme were in a good agreement with the observations both in magnitude and variation. The results of the model predictions using the MK14 scheme and Li scheme were also good, but their schemes exaggerated the impact of shear-driven turbulence, which caused discrepancies between the new empirical parameterization scheme and the MK14 scheme. Moreover, effects of soil moisture on CTDE were investigated in this study, and the results showed that there was no obvious relationship between soil moisture content and Fobs F o b s during CTDE events. This finding was likely because only dust particles in the upper few millimeters of the soil surface, where soil moisture content was relatively low in semi-arid region, can be emitted into the atmosphere during CTDE events due to weak wind speeds. In addition, compared with the saltation-bombardment and/or aggregation-disintegration dust emission (SADE) event, the process of a CTDE event may be aerodynamic lift limitation, not supply limitation.

    更新日期:2018-05-27
  • Monitoring of greenhouse gases and pollutants across an urban area using a light-rail public transit platform
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-25
    Logan E. Mitchell, Erik T. Crosman, Alexander A. Jacques, Benjamin Fasoli, Luke Leclair-Marzolf, John Horel, David R. Bowling, James R. Ehleringer, John C. Lin
    更新日期:2018-05-27
  • Impact of 3DVAR assimilation of surface PM2.5 observations on PM2.5 forecasts over China during wintertime
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-26
    Shuzhuang Feng, Fei Jiang, Ziqiang Jiang, Hengmao Wang, Zhe Cai, Lin Zhang

    Data assimilation is one of the effective ways to improve model predictions. In this study, surface fine particulate matter (PM2.5) observations during 16 December 2015 to 15 January 2016 over China are assimilated in a regional air quality forecasting system using the three-dimensional variational (3DVAR) method. Two parallel experiments with and without data assimilation (DA) are conducted. The results show that 3DVAR can significantly reduce the uncertainties of the initial PM2.5 fields and improve the subsequent PM2.5 forecasts at a certain extent. The influences of DA on both analysis and forecast fields are different in different areas. Overall, the root-mean-square error of analysis field could be reduced by at least 50%, and the correlation coefficient could be improved to more than 0.9. Less improvement appears in the North China Plain. For forecast field, similar with previous studies, the DA is effective only within a certain forecast time. On average, the benefits of DA could last more than 48 h over China. Much longer benefits (>24 h) are found in Sichuan basin, Xinjiang, southern China and part of northern China. In the first 24 h, there are more than half of Chinese cities with their daily mean PM2.5 hit rates increasing greater than 10%. The duration of DA benefits are mainly affected by weather condition and emission intensity. The areas with longer DA benefits generally have more stable weather condition and/or weaker emission intensity. The absence of heterogeneous reactions in chemical transport models may also has negative effects on the durations. In addition, we found that the assimilated observation information could transport along with the air masses, and the downwind areas generally have better DA benefits, indicating that when doing air quality forecasting using nested domains, we should conduct the DA in the largest domain rather than the innermost one.

    更新日期:2018-05-27
  • Quantifying the impact of sulfate geoengineering on mortality from air quality and UV-B exposure
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-25
    Sebastian D. Eastham, Debra K. Weisenstein, David W. Keith, Steven R.H. Barrett

    Sulfate geoengineering is a proposed method to partially counteract the global radiative forcing from accumulated greenhouse gases, potentially mitigating some impacts of climate change. While likely to be effective in slowing increases in average temperatures and extreme precipitation, there are known side-effects and potential unintended consequences which have not been quantified. One such consequence is the direct human health impact. Given the significant uncertainties, we take a sensitivity approach to explore the mechanisms and range of potential impacts. Using a chemistry-transport model, we quantify the steady-state response of three public health risks to 1 °C global mean surface cooling. We separate impacts into those which are “radiative forcing-driven”, associated with climate change “reversal” through modification of global radiative forcing, and those “direct impacts” associated uniquely with using sulfate geoengineering to achieve this. We find that the direct (non-radiative forcing driven) impact is a decrease in global mortality of ∼13,000 annually. Here the benefits of reduced ozone exposure exceed increases in mortality due to UV and particulate matter, as each unit of injected sulfur incurs 1/25th the particulate matter exposure of a unit of sulfur emitted from surface sources. This reduction is exceeded by radiative forcing-driven health impacts resulting from using sulfate geoengineering to offset 1 °C of surface temperature rise. Increased particulate matter formation at these lower temperatures results in ∼39,000 mortalities which would have been avoided at higher temperatures. As such we estimate that sulfate geoengineering in 2040 would cause ∼26,000 (95% interval: −30,000 to +79,000) early deaths annually relative to the same year without geoengineering, largely due to the loss of health benefits associated with CO2-induced warming. These results account only for impacts due to changes in air quality and UV-B flux. They do not account for non-mortality impacts or changes in atmospheric dynamics, and must be considered in the wider context of other climate change impacts such as heatwave frequency and sea level rise.

    更新日期:2018-05-25
  • Variability of zinc speciation in fine particulate matter emitted from a boiler and a combustor using residual oils
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-24
    Sidhartha Pattanaik, Frank E. Huggins, Gerald P. Huffman

    Zinc emission into the atmosphere from residual oil combustion is of significant concern due to its higher concentration, solubility and bioavailability. Exposure to zinc laden residual oil fly ash fine particulate matter with aerodynamic diameter ≤2.5 μm (ROFA PM2.5) induces pulmonary and cardiac effects. These effects are closely linked to the concentration and bonding environment of zinc in ROFA PM2.5. Four ROFA PM2.5 samples were prepared in a 732 kW practical fire tube boiler (FTB) by burning one No. 5 and three No. 6 residual oil(s) of varying sulfur and ash contents. For comparison, one ROFA PM2.5 sample was prepared in a 82 kW small refractory line combustor (RLC) by burning one of the No. 6 oils. The X-ray absorption spectroscopy data of FTB PM2.5 samples reveal that zinc sulfate hydrate (ZnSO4.7H2O) is the dominant zinc form, with the remainder Zn in zinc phosphate hydrate (Zn3(PO4)2.4H2O) form. Following dissolution of zinc sulfate from FTB PM2.5, a minor Zn-sorbed ferrihydrite form was detected in the residue. In the RLC PM2.5, zinc phosphate hydrate is predominant. The study shows that zinc solubility is dependent on its speciation, grade and composition of oils, combustion condition, and mode of Zn incorporation into particle's carbonaceous matrix. Speciation data provide valuable input to source attribution and health effect studies, and establish a link between the two.

    更新日期:2018-05-25
  • A review of factors impacting exposure to PM2.5, ultrafine particles and black carbon in Asian transport microenvironments
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-24
    Prashant Kumar, Allison P. Patton, John L. Durant, H. Christopher Frey
    更新日期:2018-05-24
  • 更新日期:2018-05-24
  • Observational evidence of cloud processes contributing to daytime elevated nitrate in an urban atmosphere
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-23
    Jun Tao, Zhisheng Zhang, Haobo Tan, Leiming Zhang, Yunfei Wu, Jiaren Sun, Huizhen Che, Junji Cao, Peng Cheng, Laiguo Chen, Renjian Zhang
    更新日期:2018-05-24
  • Determination of black carbon, PM2.5, particle number and NOx emission factors from roadside measurements and their implications for emission inventory development
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-23
    Patricia Krecl, Admir Créso Targino, Thiago Pereira Landi, Matthias Ketzel

    The road transportation sector contributes largely to air pollution in urban areas, why the knowledge of accurate vehicle emission factors (EF) is crucial to prepare reliable emission inventories, which, in turn, are strategic tools for air quality management. Curbside and rooftop concentrations of several traffic-related species were measured within a busy street canyon in Londrina (Brazil). EF for NOx, black carbon (BC), fine particles (PM2.5) and particle number (PN) were calculated based on these measurements and on inverse modeling using the Operational Street Pollution Model (OSPM). We highlight the importance of this work in quantifying BC, PM2.5, NOx and PN emissions from vehicles driven in an urban area under real conditions in a continent-sized country where there is a lack of EF studies. In the case of EFPN, we report the first value in the entire South America. Our EF were consistent with results from other on-road studies, but much higher than laboratory measurements conducted in Brazil and Europe, especially for particles (quantified as mass and number). This finding suggests that the EF derived from laboratory tests should be revised for all vehicle categories, since inaccurate values can have major implications on the compilation of official national inventories for the road transportation sector and on the assessment of their health and climate (in the case of BC) impacts. Incorporating certification procedures that more closely resemble real driving conditions is highly recommended. Limitations of the EF determined in this research for application in other studies are also discussed.

    更新日期:2018-05-24
  • 更新日期:2018-05-24
  • Erratum to ‘Isoprene emission response to drought and the impact on global atmospheric chemistry’ [Atmos. Environ. 183 (2018) 69–83]
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-24
    Xiaoyan Jiang, Alex Guenther, Mark Potosnak, Chris Geron, Roger Seco, Thomas Karl, Saewung Kim, Lianhong Gu, Stephen Pallardy
    更新日期:2018-05-24
  • 更新日期:2018-05-23
  • Effects of precipitation exclusion on N2O emissions in a savanna ecosystem in SW China
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-19
    Jing Li, Yanqiang Jin, Yuntong Liu, Yiping Zhang, John Grace, Qinghai Song, Liqing Sha, Youxing Lin, Aiguo Chen, Peiguang Li, Xuehai Fei

    Savanna ecosystems play a crucial role in global N2O emissions. However, our understanding of N2O emissions under limiting precipitation conditions is lacking. This study evaluates the effects of precipitation reduction on soil N2O fluxes from a woody savanna ecosystem in Yunnan Province, Southwest China. Precipitation exclusion shelters were installed above the tree canopy, and four total treatments were established as follows: a control (CK) and precipitation exclusions of 30% (PE3), 50% (PE5), and 70% (PE7). Two years (2015–2016) of N2O fluxes, soil temperature and soil water content data were collected. The N2O fluxes were generally low, ranging from 0.039 to 0.245 mg N m−2 d−1, and they were strongly linked to precipitation events. Additionally, the N2O fluxes during the rainy season were significantly greater than those during the dry season. The maximum N2O flux was observed in August, and the minimum flux occurred in December. Precipitation exclusion had a significant negative influence on the N2O fluxes. The N2O emissions of CK, PE3, PE5, and PE7 were 0.20, 0.17, 0.13, and 0.12 kg N ha−1 yr−1, respectively. With the exacerbation of precipitation exclusion, the decrease rate of precipitation exclusion on the N2O emissions increased over the entire year (eventually reaching 41.8% in PE7), but the decrease rate of precipitation exclusion on the soil N2O emission during the dry season was stronger than that during the rainy season. Additionally, the proportion of dry season N2O emissions to total annual emissions decreased (from 45% to 41%), and that of rainy season N2O emissions to total annual emissions increased (from 55% to 59%) over the year, whereas they exhibited a stable trend from PE5. The data show that the Yuanjiang savanna is a net source of N2O; precipitation reduction decreases the N2O emissions in the savanna regions, indicating that precipitation reduction can only slow the increase in the N2O concentration in the atmosphere and can therefore slow global warming. In addition, the N2O emissions during the dry season may play a significant role in total N2O emissions and be more sensitive to precipitation reduction than those during rainy season. These possibilities should be considered in future studies, especially in those ecosystems that experience substantial inter-annual climatic fluctuations.

    更新日期:2018-05-19
  • Inter-comparison of the Regional Atmospheric Chemistry Mechanism (RACM2) and Master Chemical Mechanism (MCM) on the simulation of acetaldehyde
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-10
    Ruihan Zong, Likun Xue, Tao Wang, Wenxing Wang

    Acetaldehyde (CH3CHO) is a key player of atmospheric chemistry, an important air pollutant, and hence a major target of air quality modeling and management. The Regional Atmospheric Chemistry Mechanism (RACM) is a highly lumped gas-phase chemical mechanism that has been widely applied in atmospheric chemistry modeling studies. A significant update of the latest version of RACM (RACM2) is the addition of CH3CHO as an explicit aldehyde species, facilitating the direct simulation of CH3CHO. In this study, we compared the performances of RACM2 and Master Chemical Mechanism (MCM; v3.3.1) on the simulation of CH3CHO. Zero-dimensional chemical box models based on these two independent mechanisms were prescribed to a polluted scenario to simulate the evolution of ozone (O3), hydroxyl radical (OH), C2H5O2 (ETHP) and CH3CHO, as well as their detailed chemical budgets. Overall, both mechanisms agreed with the simulation of O3 and OH, but the RACM2 model simulated significantly higher levels of ETHP and CH3CHO than the MCM model. The difference in the chemical kinetic data in both mechanisms is not the reason for this discrepancy. The oversimplification of the lumped peroxy acyl radicals (RCO3) and ≥C3 aldehydes chemistry of RACM2 should be responsible for its higher simulated ETHP and CH3CHO. We caution the use of RACM2 or any other highly aggregated chemical mechanism for the simulation of C2H5O2 and CH3CHO. Better methods are needed to represent the chemistry of peroxy acyl radicals and ≥C3 aldehydes for aggregated chemical mechanisms. More experiments are required to directly validate and further improve the current chemistry mechanisms.

    更新日期:2018-05-17
  • Characteristics of airborne particle number size distributions in a coastal-urban environment
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-17
    Doreena Dominick, Stephen R. Wilson, Clare Paton-Walsh, Ruhi Humphries, Elise-Andree Guérette, Melita Keywood, Dagmar Kubistin, Ben Marwick

    Particle number size distributions are among the most important parameters in trying to understand the characteristics of particle population. Atmospheric particles were measured in an interaction of mixed environments in the Southeastern coastal city of Wollongong, Australia, during a comprehensive field campaign known as Measurements of Urban, Marine and Biogenic Air (MUMBA). MUMBA ran in summer season between 21st December 2012 and 15th February 2013. Particle number concentrations measured during this campaign were indicative of the interplay between marine environments and urban air which met the objective of this campaign. Particle number size distributions ranging from 14 nm to 660 nm in diameter, as measured by Scanning Mobility Particle Sizer (SMPS) in this study, were grouped using Principal Component Analysis. Based on strong component loadings (value ≥ 0.75), three different factors were identified (i) Small Factor (NS): 15 nm < Dp < 50 nm, (ii) Medium Factor (NM): 60 nm < Dp < 150 nm and (iii) Large Factor (NL): 210 nm < Dp < 450 nm. The three factors describe 89% of the dataset cumulative variance. Particles in this region are dependent upon the interaction between the sources, and cannot be viewed as a simple mixture of biogenic and anthropogenic sources associated with various mechanical processes. The particles observed in the morning were found to be influenced by combustion emissions, presumably primarily from traffic, which is most obvious in NL. The particle population during the day was found to be influenced by a mixture of marine sources and secondary aerosols production initiated by photochemical oxidation. The local steel works and the urban environment were the major contributors of particles at night. Secondary organic aerosols were identified in this study by the mass ratio of organic carbon to elemental carbon (OC/EC). Biogenic sources influenced secondary organic aerosols formation as a moderate correlation (R2 = 0.6) was observed between secondary organic aerosols mass and biogenic isoprene. The processes described in this paper are likely repeated at other coastal urban environments worldwide.

    更新日期:2018-05-17
  • Number size distribution of atmospheric particles in a suburban Beijing in the summer and winter of 2015
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-15
    Peng Du, Huaqiao Gui, Jiaoshi Zhang, Jianguo Liu, Tongzhu Yu, Jie Wang, Yin Cheng, Zongbo Shi
    更新日期:2018-05-15
  • Comparison of aerosol optical depth between observation and simulation from MIROC-SPRINTARS: Effects of temporal inhomogeneous sampling
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-15
    Sang Seo Park, Toshihiko Takemura, Sang-Woo Kim

    The global distribution of aerosol optical depth (AOD) is simulated using an aerosol transport model coupled to an atmospheric general circulation model with high spatial and temporal resolution. Daily representative AOD from model simulation is estimated after consideration of observation sampling in daytime (ground-based) and overpass time (satellite) after cloud masking. Large deviations in AOD are found after considering temporally inhomogeneous sampling, with positive differences over desert regions and negative differences over anthropogenic pollution and biomass burning regions. Mean difference in daily AOD of 5.33% (standard deviation of 8.02%), because of temporal inhomogeneous sampling, is identified based on observation time information from the Moderate-Resolution Imaging Spectroradiometer (MODIS). Relative differences in AOD of >50% and >30% were found in 7.9% and 22.8% of the data, respectively. Based on the observation time information from the AERONET, relative root mean square error (rRMSE) of AOD due to temporal inhomogeneous sampling is estimated to be 4.30–18.66%. After correcting for temporal sampling inhomogeneity, the simulated global AOD was compared with AODs from MODIS and AERONET. The simulated AOD becomes lower than MODIS AOD because of emission and transport discrepancies related to dust, a limited accounting of nitrate processes, and limitation errors from MODIS AOD retrieval. A regional positive bias in SPRINTARS AOD was found in biomass burning regions, which is due to transport pattern errors related to the initial injection height of emissions. A weak correlation is found over the regions with multiple aerosol sources because of complex interactions of individual aerosol types.

    更新日期:2018-05-15
  • Bioaccessibility and health risk of trace elements in fine particulate matter in different simulated body fluids
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-14
    Dongyang Nie, Yun Wu, Mindong Chen, Huiling Liu, Kai Zhang, Pengxiang Ge, Yue Yuan, Xinlei Ge

    Health risk assessment of trace elements (TrElems) in fine particulate matter (PM2.5) has been studied based on the total element concentrations or more recently on the phosphate buffered saline (PBS)-soluble concentrations. However, behaviors of the TrElems released from PM2.5 change considerably as the interacting media change. In this study, the bioaccessibility of particulate-bound TrElems (V, Mn, Co, Ni, Cu, As, Cd and Pb) were investigated using three kinds of simulated body fluids, artificial lung fluid (ALF), artificial sweat (AS), and artificial gastric juice (AGJ), comparing with the commonly used PBS. Many TrElems, especially Pb, showed lower solubility in PBS than that in other fluids. Cu, Mn, V and As were observed to be the most soluble TrElems in all simulated body fluids. Carcinogenic and non-carcinogenic effects were evaluated using ALF, AS and AGJ-soluble fractions (representing the corresponding exposure routes: inhalation, dermal contact and ingestion) according to the United States Environmental Protection Agency (USEPA) human health risk assessment model. The carcinogenic risks of As and Pb were higher than 1 × 10−6 (the acceptable level) for both adults and children. High hazard quotient (HQ) values for As and Pb were also observed for children, indicating a potential non-carcinogenic risk posed by these toxic elements. Our results demonstrated that the health risks of particulate-bound TrElems might be misjudged if using the PBS-soluble or total element contents alone.

    更新日期:2018-05-15
  • A critical assessment of passive air samplers for per- and polyfluoroalkyl substances
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-14
    Pavlína Karásková, Garry Codling, Lisa Melymuk, Jana Klánová

    Since their inclusion in the Stockholm Convention, there has been a need for global monitoring of perfluorooctane sulfonate (PFOS), its salts and perfluorooctanesulfonyl fluoride (PFOSF), along with other non-listed highly fluorinated compounds. Passive air samplers (PAS) are ideal for geographic coverage of atmospheric monitoring. The most common type of PAS, using polyurethane foam (PUF) as a sorbent, was primarily developed for non-polar semivolatile organic compounds (SVOCs) and are not well-validated for polar substances such as the per- and polyfluoroalkyl substances (PFASs), however, they have been used for some PFASs, particularly PFOS. To evaluate their applicability, PAS were deployed for measurement of PFASs in outdoor and indoor air. Outdoors, two types of PAS, one consisting of PUF and one of XAD-2 resin, were deployed in an 18-week calibration study in parallel with a low-volume active air sampler (LV-AAS) in a suburban area. Indoors, PUF-PAS were similarly deployed over 12 weeks to evaluate their applicability for indoor monitoring. Samples were analysed for perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonates (PFSAs), perfluorooctane sulfonamides (FOSAs), and perfluorooctane sulfonamidoethanols (FOSEs). In outdoor air, 17 out of the 21 PFAS were detected in more than 50% of samples, with a median ∑17PFASs of 18.0 pg m−3 while 20 compounds were detected in indoor air with a median concentration ∑20PFASs of 76.6 pg m−3 using AAS samplers. PFOS was the most common PFAS in the outdoor air while PFBA was most common indoors. Variability between PAS and AAS was observed and comparing gas-phase and particle phase separately or combined did not identify the variation observed. PUF-PAS may still have a valuable use in PFAS monitoring but more work is needed to identify the applicability of passive samplers for ionic PFAS.

    更新日期:2018-05-15
  • Personal exposure of PM2.5 emitted from solid fuels combustion for household heating and cooking in rural Guanzhong Plain, northwestern China
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-11
    Hongmei Xu, Yaqi Li, Benjamin Guinot, Jinhui Wang, Kailai He, Kin Fai Ho, Junji Cao, Zhenxing Shen, Jian Sun, Yali Lei, Xuesong Gong, Ting Zhang

    Household solid fuel combustion for heating and cooking in rural areas is an important source of fine particulate matter (PM2.5) in northwestern China, which largely contributes to PM2.5 personal exposure concentrations during the cold winter. There is a general lack of understanding about the personal exposure to PM2.5 and to its chemical components emitted from domestic solid fuel combustion in northwestern Chinese rural populations. In this work, personal exposure to PM2.5 was sampled using a portative device together with fixed indoor and outdoor fixed samplings in Guanzhong Plain in December 2016 for the purpose of characterizing personal exposure to PM2.5 as a function of different solid fuels used in rural households. The average housewife's personal exposure to PM2.5 concentration was 263.4 ± 105.8 μg m−3 (1σ, n = 30), which was about 40% higher than the values found indoors (186.5 ± 79.5 μg m−3, 1σ, n = 30) and outdoors (191.0 ± 85.3 μg m−3, 1σ, n = 30). High personal exposure PM2.5 levels were mainly related to the ignition of solid fuels for heating and cooking. Correlations among personal exposure, indoor and outdoor PM2.5 levels and their mutual ratios were computed to investigate how personal exposure to fine aerosols can be related to microenvironmental PM2.5 levels and to individual activities. The results showed that households using electric power for heating and cooking were characterized by an average personal exposure PM2.5 value of 156.8 ± 36.6 μg m−3 (1σ, n = 6) while personal exposure to PM2.5 in households using solid fuels was twice higher (310.8 ± 90.4 μg m−3, 1σ, n = 24). Solid fuel combustion products and related secondary formed species dominated PM2.5 mass in personal exposure, indoor and outdoor samples. Motor vehicle emission and various dust sources were two other main contributors identified. Our results demonstrated that the use of clean energy could be an effective measure to reduce personal exposure levels of PM2.5 emitted from domestic solid fuels combustion in winter in rural areas, which implied that the government should speed up the upgrade of the heating and cooking equipment fleet to protect the health of rural residents in northwestern China.

    更新日期:2018-05-11
  • Behavior of sulfate on the sea surface during its transport from Eastern China to South Korea
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-11
    Wonbae Jeon, Yunsoo Choi, Jeonghyeok Mun, Soon-Hwan Lee, Hyun-Jeong Choi, Jung-Woo Yoo, Hyo-Jung Lee, Hwa Woon Lee
    更新日期:2018-05-11
  • N2O and CH4 emissions from N-fertilized rice paddy soil can be mitigated by wood vinegar application at an appropriate rate
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-10
    Haijun Sun, Yanfang Feng, Yang Ji, Weiming Shi, Linzhang Yang, Baoshan Xing

    To understand the impacts of wood vinegar (WV), a by-product of biochar production, on N2O and CH4 emissions and their total global warming potential (GWPt) from N-fertilized rice paddy soil, a soil column experiment was conducted using three treatments: 240 kg urea-N ha−1 accompanied with 0, 5, and 10 t WV ha−1, respectively. Results showed that N2O and CH4 emission flux patterns were dominated by water regime of rice growth cycle, which was independent with WV application. The total N2O, CH4 emission loads and GWPt over rice season of three N received treatments were 6.41–8.85 kg ha−1, 127.7–405.0 kg ha−1, and 5.24–12.03 t CO2-e ha−1, respectively. Rice seasonal N2O and CH4 emissions were synchronously mitigated by 22.4% and 36.4%, respectively, when WV was applied at 5 t ha−1. Consequently, 5 t ha−1 WV treatment reduced 31.5% of GWPt compared with the urea treatment. In addition, 10 t ha−1 WV treatment exerted a more positive effect on suppressing N2O with 27.6% reduction. However, it increased GWPt by 57.2% because its CH4 emission load was increased by 101.8%. In conclusion, WV amendment applied at an appropriate rate (5 t ha−1) or combination with other CH4 control technologies were suggested to reduce both N2O and CH4 emissions and thereby the GWPt in N-fertilized rice paddy soil.

    更新日期:2018-05-10
  • Dispersion simulations using HYSPLIT for the Sagebrush Tracer Experiment
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-09
    Fong Ngan, Ariel Stein, Dennis Finn, Richard Eckman

    The Sagebrush experiment, led by NOAA's Field Research Division of the Air Resources Laboratory, consisted of five releases (intensive observation periods, or IOPs) of a chemically inert trace gas on five days in October 2013. All releases occurred in the afternoon under either near neutral stability conditions with high wind speeds or unstable conditions with low wind speeds. The sampling network for the tracer concentrations covered distances 200 m–3200 m from the release location and samples were obtained in 10-min averages. HYSPLIT, NOAA's transport and dispersion model, was used to simulate the spatial and temporal distribution of the tracer. The dispersion simulations were driven by WRF meteorological data with 27-km to 333-m grid spacing and using the inline and offline approaches as well as different planetary boundary layer schemes and a large-eddy simulation parameterization. Comparisons with measured wind speeds showed that none of the WRF PBL schemes or the large-eddy simulation parameterization was able to reproduce the rapid increase in high wind speeds observed during IOP3. The dispersion results were compared with the tracer measurements obtained during the experiment. The HYSPLIT dispersion simulations for IOP3, driven by the WRF data generated with various PBL schemes, showed greater concentration variability than the simulations performed for IOP5. The comparison between the inline and offline HYSPLIT simulations showed that the inline approach statistically outperformed the offline approach in three out of four IOPs because the tight coupling between the advection and dispersion processes implemented in the inline approach produced higher simulated concentrations close to the release location.

    更新日期:2018-05-09
  • Stable carbon isotopes and levoglucosan for PM2.5 elemental carbon source apportionments in the largest city of Northwest China
    Atmos. Environ. (IF 3.629) Pub Date : 2018-05-09
    Zhuzi Zhao, Junji Cao, Ting Zhang, Zhenxing Shen, Haiyan Ni, Jie Tian, Qiyuan Wang, Suixin Liu, Jiamao Zhou, Jian Gu, Ganzhou Shen

    Stable carbon isotopes provide information on aerosol sources, but no extensive long-term studies of these isotopes have been conducted in China, and they have mainly been used for qualitative rather than quantitative purposes. Here, 24 h PM2.5 samples (n = 58) were collected from July 2008 to June 2009 at Xi'an, China. The concentrations of organic and elemental carbon (OC and EC), water-soluble OC, and the stable carbon isotope abundances of OC and EC were determined. In spring, summer, autumn and winter, the mean stable carbon isotope in OC (δ13COC) were -26.4 ± 0.6, -25.8 ± 0.7, -25.0 ± 0.6 and -24.4 ± 0.8‰, respectively, and the corresponding δ13CEC values were -25.5 ± 0.4, -25.5 ± 0.8, -25.2 ± 0.7 and -23.7 ± 0.6‰. Large δ13CEC and δ13COC values in winter can be linked to the burning coal for residential heating. Less biomass is burned during spring and summer than winter or fall (manifested in the levels of levoglucosan, i.e., 178, 85, 370, 935 ng m−3 in spring, summer, autumn, and winter), and the more negative δ13COC in the warmer months can be explained by the formation of secondary organic aerosols. A levoglucosan tracer method combined with an isotope mass balance analysis indicated that biomass burning accounted for 1.6–29.0% of the EC, and the mean value in winter (14.9 ± 7.5%) was 7 times higher than summer (2.1 ± 0.4%), with intermediate values of 6.1 ± 5.6 and 4.5 ± 2.4% in autumn and spring. Coal combustion accounted for 45.9 ± 23.1% of the EC overall, and the percentages were 63.0, 37.2, 36.7, and 33.7% in winter, autumn, summer and spring respectively. Motor vehicles accounted for 46.6 ± 26.5% of the annual EC, and these contributed over half (56.7–61.8%) of the EC in all seasons except winter. Correlations between motor vehicle-EC and coal combustion-EC with established source indicators (B(ghi)P and As) support the source apportionment results. This paper describes a simple and accurate method for apportioning the sources of EC, and the results may be beneficial for developing model simulations as well as controlling strategies in future.

    更新日期:2018-05-09
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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