Winter-time particulate nitrosamines and nitramines in the atmosphere at seoul, South Korea
Introduction
Most studies on nitrogen species in airborne particles have focused on inorganic species such as NO3−, NO2−, and NH4+ (Elser et al., 2016; Jung et al., 2019; Sun et al., 2012) and little is known about organic nitrogen (ON) species. Recent studies have shown that organic N exists in gas, particle, and dissolved phases and comprises a large fraction (ca. 30%) of total airborne nitrogen (Cape et al., 2011), and Cornell showed that the fraction of the organic N to the total N is 11–42%. However, the speciation and sources of particulate ON compounds remain largely uncertainty.
Nitrosamines and nitramines are important classes of ON containing nitroso (N-NO) and nitro (N-NO2) functional groups, respectively. Nitrosamines can be emitted from the emission sources such as vehicular exhaust, plastic and rubber combustion, tobacco smoke, cooking, and landfill release (Ge et al., 2011; Nielsen et al., 2012a; NTP, 2016). Recently emissions of nitrosamines and nitramines from carbon capture and storage (CCS) procedures have been highlighted (Chen et al., 2018; Nielsen et al., 2012b) although CCS is not considered as a possible primary emission source in this study since it has been not processed yet in South Korea. Emission sources of nitramines except CCS procedure have not been identified, but it is presumed to have similar emission sources of nitrosamines since they have similar chemical structures.
Nitrosamines and nitramines can be also generated from gaseous reactions of amino radical produced from the reaction of the amines and OH radical with NO and NO2. For example, the gaseous and aqueous phase reactions producing nitrosodi-methylamine (NDMA) and dimethylnitramine (DMN), typical nitrosamine and nitramines compounds, respectively, in the atmosphere are suggested in Fig. 1. Atmospheric gaseous dimethylamine can be oxidized by the OH radical and produce the dimethyl amino radical (Nielsen et al., 2012a). The dimethyl amino radical can react with NO and NO2 and form gaseous NDMA and DMN, respectively (Ge et al., 2011; Hutchings et al., 2010; Nielsen et al., 2012a). NDMA and DMN can be removed in the atmosphere by oxidation and NDMA can be also removed via the photolysis. (Nielsen et al., 2012a, 2012b).
In the aqueous phase, dimethylamines can react with N2O3, N2O4, HONO, and NO2−, producing NDMA (Herrmann and Weller, 2011; Karl et al., 2012). Furthermore, the reaction of dimethylamines with N2O4 forms DMN (Herrmann and Weller, 2011; Karl et al., 2012). Gaseous and aqueous NDMA and DMN can be also removed by photolysis (NDMA) and oxidation (NDMA and DMN), but the removal rates of aqueous phase NDMA and DMN are slower than those in the gaseous phase (Herrmann and Weller, 2011; Karl et al., 2012). Nielsen et al. (2011) also reported that NDMA can be produced from the heterogenous reactions of dimethylamine with HONO and NO, therefore, the investigation on the characteristics of the heterogenous reactions of dimethylamine producing NDMA should be further understood. In this study, only the gaseous reactions of dimethyl amino radical with NO and NO2 and aqueous reaction of dimethylamine with HONO are considered due to the lack of the information on the heterogeneous reactions of dimethylamine producing NDMA.
It is well known that nitrosamines and nitramines have detrimental health effects. Most nitrosamines are included in the International Agency of Research on Cancer (IARC) carcinogenic group 2A (probably carcinogenic to humans) to 2B (possibly carcinogenic to humans) materials. Therefore, many organizations regulate nitrosamines concentrations or recommend guidelines for nitrosamine concentrations in various matrices. For example, the World Health Organization (WHO) suggests guidelines of NDMA for drinking water quality (100 ng/L) (WHO, 2008). The US Environmental Protection Agency (EPA) enforces and/or recommends nitrosamines concentrations in drinking water, wastewater, and commerce (US EPA, 1972, US EPA, 1976a, US EPA, 1976b, US EPA, 1980). The US Food and Drug Administration (FDA) (US FDA, 1984), European Commission (EC) (EC, 1993) and the Korean Ministry of Food and Drug Safety (MFDS) (MFDS, 2013) suggest recommended nitrosamines concentration in rubber products. The Norwegian Institute of Public Health (NIPH) recommends that total concentrations of NDMA do not exceed 0.3 ng/m3 (Låg et al., 1984). Nitramines also exhibit acute toxicity (TD50 for rat: 0.174 mg/kg∙day (DMN); 17.4 (NMN)) although the toxicities are lower than those of nitrosamines (TD50 for rat: 0.0959 mg/kg∙day (NDMA); 0.0536 (NDEA)) (Selin, 2011). However, the policy regulation on nitramines are only for nitramine explosives such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and octahydro-1,3,5,7,-tetranitro-1,3,5,7-tetrazocine) (Selin, 2011). As an example, New Jersey in the US sets quality standard of 0.3 μg/L for RDX in groundwater (New Jersey, 2008), but regulations on aliphatic nitramines have not been established yet.
Concentrations of nitrosamines in the atmosphere have been reported in a few studies. Study on the nitrosamine concentration in North Kensington, U. K., where agricultural activities have been conducted (Farren et al., 2015) and Akyüz and Ata (2013) measured the concentrations of nitrosamines in an industrial area, where the primary emission sources are located not the urban atmosphere. Choi et al., (2018) and Hong et al., (2017) reported nitrosamine concentrations in the mixed residential and commercial areas and the road side at Seoul, South Korea. However, in these two studies, there was no information of the nitramines concentrations and clarification of the characteristics of the atmospheric behavior of the particulate nitrosamines. Hutchings et al., (2010) showed NDMA concentrations in fog samples and compared the measurement and estimation results using a model, but the NDMA concentration in the aerosol and other nitrosamine concentrations were also limited. Especially, these studies only suggested the concentrations of the nitrosamines and not reported the nitramines concentration in the atmosphere, although the atmospheric behaviors of the nitrosamines and nitramines might be related.
Nevertheless, the investigation on the ambient concentration of nitrosamines and nitramines has been insufficient. Especially, Nitramines concentrations have not been reported in the ambient air although chamber studies on the fate of nitramines have been conducted (Nielsen et al., 2012a, Nielsen et al., 2012b; Karl et al., 2012). The investigation on the characteristics of the atmospheric behavior of the particulate nitrosamines and nitramines should be carried out, since the emission sources and the characteristics of the atmospheric reactions producing the particulate nitrosamines and nitramines in the ambient have been remained to be unclear.
The goals of this study are to report ambient levels of nitosamines and nitramines and to determine the relative importance of primary emissions and secondary reactions in the air for ambient particulate nitrosamines and nitramines concentrations. To do so, (1) 7 particulate nitrosamines (nitroso dimethylamine, nitroso diethylamine, nitroso dipropylamine, nitroso dibutylamine, nitroso morpholine, nitroso piperidine, and nitroso pyrrolidine) and 3 nitramines (methylnitramine, dimethylnitramine, and diethylnitramine) (shown in Table 1) were quantified in the ambient atmosphere at Seoul in winter 2018 using a gas chromatograph and tandem mass spectrometer (GC/MS-MS) in the electron ionization (EI) mode coupled with solvent extraction (SE) and (2) statistical analyses such as correlation and orthogonal partial least square-discrimination analysis (OPLS-DA) to determine the markers affecting the production of nitrosamines and nitramines in the ambient atmosphere at Seoul were carried out for the ambient trace species which were either simultaneously measured or estimated by the modeling during the sampling period.
Section snippets
Sampling
Twenty-six daily PM2.5 samples were collected from January to February 2018 using a high-volume air sampler (6070V-2.5, TISCH, US) which was operated for 23 h daily at the constant flow rate of 1.06 0.03 m3/min. The sampling site was the Seoul Metropolitan Area (SMA) intensive monitoring center of air pollution in Seoul, South Korea (37.6 °N; 126.9 °E). This monitoring center is a supersite managed by the National Institute of Environment Research (NIER) of the Korea Ministry of Environment
Ambient concentration
The daily mean concentrations of total 7 nitrosamines and 3 nitramines observed during winter 2018 were 9.75 17.77 ng/m3 (0.06–54.72 ng/m3) and 0.68 0.56 ng/m3 (0.08–2.40 ng/m3), respectively (Fig. 3). The average concentrations of the target nitrosamines and nitramines are shown in Table 3.
Among the nitrosamines and nitramines, NDMA comprised the largest fraction among the target nitrosamines, as shown in Table 3. Although the mean concentration of NMN was highest among the target
Conclusions
Seven nitrosamines and three nitramines in the particulate phase in the ambient atmosphere at Seoul, South Korea, were analyzed using GC/MS-MS for 26 samples collected in winter 2018. The daily average concentrations of 7 nitrosamines and 3 nitramines were 9.75 17.77 ng/m3 (0.06–54.72 ng/m3) and 0.68 0.56 ng/m3 (0.08–2.40 ng/m3), respectively. Among the nitrosamines and nitramines, NDMA and DMN showed the largest portion, and fractions of NDMA and DMN in PM2.5 increased with the PM2.5
CRediT authorship contribution statement
Na Rae Choi: Conceptualization, Writing - original draft. Yun Gyong Ahn: Validation. Ji Yi Lee: Investigation. Eunhye Kim: Software. Soontae Kim: Software. Seung Myung Park: Resources, Validation. In Ho Song: Resources, Validation. Yong Pyo Kim: Writing - review & editing, Supervision, Project administration.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
This work was supported by Technology Development Program to Solve Climate Changes through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT (NRF-2019M1A2A2103953). This work was also supported by NRF funded by the Ministry of Education (NRF-2019R1A6A3A13090585) and a Korea Basic Science Institute grant (C070200). One of the authors (N. R. Choi) is grateful for being awarded the Solvay Scholarship.
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