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Fate of mercury from artisanal and small-scale gold mining in tropical rivers: Hydrological and biogeochemical controls. A critical review Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2019-07-07 Mónica Moreno-Brush; David S. McLagan; Harald Biester
Despite numerous existing publications, the fate of mercury (Hg) in ASGM-affected tropical aquatic systems remains uncertain. This is driven by an incomplete understanding of the factors controlling Hg distribution and transport in tropical ecosystems. The review of existing Hg research into ASGM indicated that hydrology exerts major control on the final sink of Hg in tropical rivers. Total Hg concentrations in river water increase during high discharge events due to increased erosion and Hg export from soils. Geochemical composition and grain-size distribution strongly control Hg concentrations and distribution in sediment and soils. This review highlights the absence of standardized protocols for investigating ASGM-related Hg pollution, and that the applied research methodologies are often unsuitable for adequately assessing the processes involved. We underline the need to consider an extensive suite of biogeochemical, physical and hydrological information when investigating the final sink and risks of ASGM-related Hg. Standardized and accurate research methodologies, applicable to the challenges presented by these tropical environments, would greatly ease not only data comparability and synthesis between studies, but also help to differentiate between anthropogenic and natural Hg. Establishing background values in tropical regions is also imperative for accurate quantifications of Hg enrichment levels in ASGM-affected sites.
A critical review on remediation of bisphenol S (BPS) contaminated water: Efficacy and mechanisms Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2019-06-26 Zheng Fang; Yurong Gao; Xiaolian Wu; Xiaoya Xu; Ajit K. Sarmah; Nanthi Bolan; Bin Gao; Sabry M. Shaheen; Jörg Rinklebe; Yong Sik Ok; Song Xu; Hailong Wang
Bisphenols have drawn increasing attention from regulatory agencies and scientific communities due to their widespread occurrences, distribution and endocrine disrupting effects, and severe toxicity. As one of the bisphenol A (BPA) substitutes, bisphenol S (BPS) is most frequently detected in the environment. Although numerous studies have shown its occurrence, distribution, and toxicity to certain aquatic species, investigation on BPS removal from aqueous environments is lacking. Thus, in this review, we summarize the state-of-art about BPS removal approaches including biodegradation, sorption, and advanced oxidation processes. Particular attention has been paid to the BPS sorption mechanisms, active species for BPS biodegradation, and the corresponding degradation pathways. The primary degradation intermediates formed during BPS oxidation (e.g. p-hydroxybenzenesulfonic acid) are discussed. The effects of solution chemistry (pH, ionic strength, anion, and surfactants) on BPS decontamination are also emphasized. In addition, knowledge gaps, current challenges, and future research needs of BPS decontamination in real environments have been discussed briefly. Through this review we demonstrate the overarching scientific opportunities for a comprehensive understanding of the efficiency and mechanisms of the bio-and chemical remediation approaches of BPS contaminated water. Highlights Microplastics may become a new source of bisphenol S (BPS) in aquatic environment. BPS is biodegradable but it may take a long time. Major mechanisms for BPS sorption are summarized and discussed. BPS degradation mechanisms and pathways are summarized.
Heterogeneous photocatalytic decomposition of per- and poly-fluoroalkyl substances: A review Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2019-06-28 Qingbo Sun; Chunyan Zhao; Terry J. Frankcombe; Hong Liu; Yun Liu
Per- and poly-fluoroalkyl substances (PFASs) as emergent contaminants are generating serious environmental and health issues. An imminent task is thus to develop effective technologies to completely remove and ideally decompose PFASs through physical and/or chemical routes. Heterogeneous photocatalysis, which directly utilizes sunlight to drive the chemical decomposition of many organic compounds, is a promising solution to remediating PFASs-contaminated environment. In this review, the current progress of heterogeneous photocatalytic technology for decomposing PFASs is systematically summarized. The significance of environmental factors during heterogeneous photocatalysis is discussed from three aspects including anaerobic vs aerobic, acidic vs alkaline, and light use vs light loss. The associated reaction mechanisms and reaction routes are analyzed based on the stepwise change of PFASs molecular structures. Some further issues regarding PFASs heterogeneous photocatalysis are briefly pointed out along with the potential industrial applications of this technology.
Research progress, problems and prospects of mine water treatment technology and resource utilization in China Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2019-07-04 Siyu Zhang; Hao Wang; Xuwen He; Shaoqing Guo; Yu Xia; Yuexi Zhou; Kai Liu; Shipeng Yang
The National Development and Reform Commission and the Energy Bureau jointly issued the ‘Plant Water Utilization Development Plan’ on January 29, 2013, which requires that China should gradually establish a more complete legal system, macro management and technical support system for mine water in 2015. But so far, due to the influence of geological conditions and other factors, the impurity composition and content of mine water is very different. Based on the comprehensive summary of the theory, method, application technology, practical engineering and processing technology of mine water disaster and its reutilization in China. This article systematically analyzed the latest research progress and achievements, which include basic theory, hydrogeology (supplement) exploration, advanced detection and monitoring as well as early warning. These can further promote application of current technology, develop new technology and methods, point out the challenges and the existing problems of the mine water field, the gaps with requirements of fast, intensive, and large-scale development of the coal industry in China. Finally, the development trends, future important scientific innovation and key technology were discussed. The prospects of the industry and technology were also forecast.
Production technologies, current role, and future prospects of biofuels feedstocks: A state-of-the-art review Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2019-06-25 Arianna Callegari; Silvia Bolognesi; Daniele Cecconet; Andrea G. Capodaglio
Fossil fuel continued overuse and carbon emissions issues have prompted increased research efforts on sustainable and renewable energy sources as alternative to fossil fuels. Biofuels include products derived from biomasses or their residues, such as: biogas, biodiesel, bioethanol, biomethanol, synthetic biofuels, biohydrogen and vegetable oil. Due to their properties, all of these may be used in conventional engines as produced, or blended with fossil fuels. First and second generation biofuels may be produced from a large variety of feedstocks, including food crops such as sugar beet, sugar cane, sorghum, energy-crops, such as lignocellulosic masses, and waste, like the organic fraction of municipal solid waste, or landfill leachate. In the last decade, a third generation of biofuels has emerged, i.e. those derived from microalgae. Even though their yield is higher, and their greenhouse gas footprint lower than previous generations’, they still need large amounts of water and nutrients for production. In this paper, the most common biofuels (biogas, syngas, biodiesel, bioethanol and biobutanol) are reviewed and analyzed with particular attention on their carbon and water footprints and economic sustainability perspective.
Knowledge Mapping for Climate Change and Food- and Waterborne Diseases. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2012-02-01 Jan C Semenza,Christoph Höuser,Susanne Herbst,Andrea Rechenburg,Jonathan E Suk,Tobias Frechen,Thomas Kistemann
The authors extracted from the PubMed and ScienceDirect bibliographic databases all articles published between 1998 and 2009 that were relevant to climate change and food- and waterborne diseases. Any material within each article that provided information about a relevant pathogen and its relationship with climate and climate change was summarized as a key fact, entered into a relational knowledge base, and tagged with the terminology (predefined terms) used in the field. These terms were organized, quantified, and mapped according to predefined hierarchical categories. For noncholera Vibrio sp. and Cryptosporidium sp., data on climatic and environmental influences (52% and 49% of the total number of key facts, respectively) pertained to specific weather phenomena (as opposed to climate change phenomena) and environmental determinants, whereas information on the potential effects of food-related determinants that might be related to climate or climate change were virtually absent. This proportion was lower for the other pathogens studied (Campylobacter sp. 40%, Salmonella sp. 27%, Norovirus 25%, Listeria sp. 8%), but they all displayed a distinct concentration of information on general food-and water-related determinants or effects, albeit with little detail. Almost no information was available concerning the potential effects of changes in climatic variables on the pathogens evaluated, such as changes in air or water temperature, precipitation, humidity, UV radiation, wind, cloud coverage, sunshine hours, or seasonality. Frequency profiles revealed an abundance of data on weather and food-specific determinants, but also exposed extensive data deficiencies, particularly with regard to the potential effects of climate change on the pathogens evaluated. A reprioritization of public health research is warranted to ensure that funding is dedicated to explicitly studying the effects of changes in climate variables on food- and waterborne diseases.
Phytoextraction of Cd-Contaminated Soils: Current Status and Future Challenges. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2013-01-22 Jin-Tian Li,Alan J M Baker,Zhi-Hong Ye,Hong-Bin Wang,Wen-Sheng Shu
Cadmium (Cd) is one of the most toxic and widely distributed pollutants in the environment. Cadmium contamination of soils has posed a serious threat to safe food production in many parts of the world. The authors present a comprehensive review of present status of phytoextraction technology for cleaning up Cd-contaminated soils, based primarily on the data resulting from both laboratory and field-scale studies that have been conducted to assess or improve the Cd phytoextraction potential of various plant species in the past decade. The encouraging results of field-scale studies have provided a fundamental basis to usher phytoextraction technology into practical use to remediate slightly to moderately Cd-contaminated soils in Europe and Asia, although this technology is not yet ready for widespread application. Chelators and microorganisms tested so far seem not to contribute to the applicability of Cd phytoextraction. The major challenges for the large-scale application of Cd phytoextraction are (a) how to further improve the efficiency of Cd phytoextraction, (b) how to cut the overall costs of Cd phytoextraction, and (c) how to get greater stakeholders' acceptance of Cd phytoextraction as a reliable option.
Climate Change Impact Assessment of Food- and Waterborne Diseases. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2012-04-01 Jan C Semenza,Susanne Herbst,Andrea Rechenburg,Jonathan E Suk,Christoph Höser,Christiane Schreiber,Thomas Kistemann
The PubMed and ScienceDirect bibliographic databases were searched for the period of 1998-2009 to evaluate the impact of climatic and environmental determinants on food- and waterborne diseases. The authors assessed 1,642 short and concise sentences (key facts), which were extracted from 722 relevant articles and stored in a climate change knowledge base. Key facts pertaining to temperature, precipitation, water, and food for 6 selected pathogens were scrutinized, evaluated, and compiled according to exposure pathways. These key facts (corresponding to approximately 50,000 words) were mapped to 275 terminology terms identified in the literature, which generated 6,341 connections. These relationships were plotted on semantic network maps to examine the interconnections between variables. The risk of campylobacteriosis is associated with mean weekly temperatures, although this link is shown more strongly in the literature relating to salmonellosis. Irregular and severe rain events are associated with Cryptosporidium sp. outbreaks, while noncholera Vibrio sp. displays increased growth rates in coastal waters during hot summers. In contrast, for Norovirus and Listeria sp. the association with climatic variables was relatively weak, but much stronger for food determinants. Electronic data mining to assess the impact of climate change on food- and waterborne diseases assured a methodical appraisal of the field. This climate change knowledge base can support national climate change vulnerability, impact, and adaptation assessments and facilitate the management of future threats from infectious diseases. In the light of diminishing resources for public health this approach can help balance different climate change adaptation options.
Estimating the microbiological risks associated with inland flood events: Bridging theory and models of pathogen transport. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2016-01-01 Philip A Collender,Olivia C Cooke,Lee D Bryant,Thomas R Kjeldsen,Justin V Remais
Flooding is known to facilitate infectious disease transmission, yet quantitative research on microbiological risks associated with floods has been limited. Pathogen fate and transport models provide a framework to examine interactions between landscape characteristics, hydrology, and waterborne disease risks, but have not been widely developed for flood conditions. We critically examine capabilities of current hydrological models to represent unusual flow paths, non-uniform flow depths, and unsteady flow velocities that accompany flooding. We investigate the theoretical linkages between hydrodynamic processes and spatio-temporally variable suspension and deposition of pathogens from soils and sediments; pathogen dispersion in flow; and concentrations of constituents influencing pathogen transport and persistence. Identifying gaps in knowledge and modeling practice, we propose a research agenda to strengthen microbial fate and transport modeling applied to inland floods: 1) development of models incorporating pathogen discharges from flooded sources (e.g., latrines), effects of transported constituents on pathogen persistence, and supply-limited pathogen transport; 2) studies assessing parameter identifiability and comparing model performance under varying degrees of process representation, in a range of settings; 3) development of remotely sensed datasets to support modeling of vulnerable, data-poor regions; and 4) collaboration between modelers and field-based researchers to expand the collection of useful data in situ.
Nonoxidative removal of organics in the activated sludge process. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2016-07-28 Oskar Modin,Frank Persson,Britt-Marie Wilén,Malte Hermansson
The activated sludge process is commonly used to treat wastewater by aerobic oxidation of organic pollutants into carbon dioxide and water. However, several nonoxidative mechanisms can also contribute to removal of organics. Sorption onto activated sludge can remove a large fraction of the colloidal and particulate wastewater organics. Intracellular storage of, e.g., polyhydroxyalkanoates (PHA), triacylglycerides (TAG), or wax esters can convert wastewater organics into precursors for high-value products. Recently, several environmental, economic, and technological drivers have stimulated research on nonoxidative removal of organics for wastewater treatment. In this paper, we review these nonoxidative removal mechanisms as well as the existing and emerging process configurations that make use of them for wastewater treatment. Better utilization of nonoxidative processes in activated sludge could reduce the wasteful aerobic oxidation of organic compounds and lead to more resource-efficient wastewater treatment plants.
Radioiodine Biogeochemistry and Prevalence in Groundwater. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2014-09-30 D I Kaplan,M E Denham,S Zhang,C Yeager,C Xu,K A Schwehr,H P Li,Y F Ho,D Wellman,P H Santschi
129I is commonly either the top or among the top risk drivers, along with 99Tc, at radiological waste disposal sites and contaminated groundwater sites where nuclear material fabrication or reprocessing has occurred. The risk stems largely from 129I having a high toxicity, a high bioaccumulation factor (90% of all the body's iodine concentrates in the thyroid), a high inventory at source terms (due to its high fission yield), an extremely long half-life (16M years), and rapid mobility in the subsurface environment. Another important reason that 129I is a key risk driver is that there is uncertainty regarding its biogeochemical fate and transport in the environment. We typically can define 129I mass balance and flux at sites, but cannot predict accurately its response to changes in the environment. As a consequence of some of these characteristics, 129I has a very low drinking water standard, which is set at 1 pCi/L, the lowest of all radionuclides in the Federal Register. Recently, significant advancements have been made in detecting iodine species at ambient groundwater concentrations, defining the nature of the organic matter and iodine bond, and quantifying the role of naturally occurring sediment microbes to promote iodine oxidation and reduction. These recent studies have led to a more mechanistic understanding of radioiodine biogeochemistry. The objective of this review is to describe these advances and to provide a state of the science of radioiodine biogeochemistry relevant to its fate and transport in the terrestrial environment and provide information useful for making decisions regarding the stewardship and remediation of 129I contaminated sites. As part of this review, knowledge gaps were identified that would significantly advance the goals of basic and applied research programs for accelerating 129I environmental remediation and reducing uncertainty associated with disposal of 129I waste. Together the information gained from addressing these knowledge gaps will not alter the observation that 129I is primarily mobile, but it will likely permit demonstration that the entire 129I pool in the source term is not moving at the same rate and some may be tightly bound to the sediment, thereby smearing the modeled 129I peak and reducing maximum calculated risk.
Factors and Trends Affecting the Identification of a Reliable Biomarker for Diesel Exhaust Exposure. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2014-08-30 David A Morgott
The monitoring of human exposures to diesel exhaust continues to be a vexing problem for specialists seeking information on the potential health effects of this ubiquitous combustion product. Exposure biomarkers have yielded a potential solution to this problem by providing a direct measure of an individual's contact with key components in the exhaust stream. Spurred by the advent of new, highly sensitive, analytical methods capable of detecting substances at very low levels, there have been numerous attempts at identifying a stable and specific biomarker. Despite these new techniques, there is currently no foolproof method for unambiguously separating diesel exhaust exposures from those arising from other combustion sources. Diesel exhaust is a highly complex mixture of solid, liquid, and gaseous components whose exact composition can be affected by many variables, including engine technology, fuel composition, operating conditions, and photochemical aging. These factors together with those related to exposure methodology, epidemiological necessity, and regulatory reform can have a decided impact on the success or failure of future research aimed at identifying a suitable biomarker of exposure. The objective of this review is to examine existing information on exposure biomarkers for diesel exhaust and to identify those factors and trends that have had an impact on the successful identification of metrics for both occupational and community settings. The information will provide interested parties with a template for more thoroughly understanding those factors affecting diesel exhaust emissions and for identifying those substances and research approaches holding the greatest promise for future success.
Environmental Safety of the Use of Major Surfactant Classes in North America. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2014-08-30 Christina Cowan-Ellsberry,Scott Belanger,Philip Dorn,Scott Dyer,Drew McAvoy,Hans Sanderson,Donald Versteeg,Darci Ferrer,Kathleen Stanton
This paper brings together over 250 published and unpublished studies on the environmental properties, fate, and toxicity of the four major, high-volume surfactant classes and relevant feedstocks. The surfactants and feedstocks covered include alcohol sulfate or alcohol sulfate (AS), alcohol ethoxysulfate (AES), linear alkylbenzene sulfonate (LAS), alcohol ethoxylate (AE), and long-chain alcohol (LCOH). These chemicals are used in a wide range of personal care and cleaning products. To date, this is the most comprehensive report on these substance's chemical structures, use, and volume information, physical/chemical properties, environmental fate properties such as biodegradation and sorption, monitoring studies through sewers, wastewater treatment plants and eventual release to the environment, aquatic and sediment toxicity, and bioaccumulation information. These data are used to illustrate the process for conducting both prospective and retrospective risk assessments for large-volume chemicals and categories of chemicals with wide dispersive use. Prospective risk assessments of AS, AES, AE, LAS, and LCOH demonstrate that these substances, although used in very high volume and widely released to the aquatic environment, have no adverse impact on the aquatic or sediment environments at current levels of use. The retrospective risk assessments of these same substances have clearly demonstrated that the conclusions of the prospective risk assessments are valid and confirm that these substances do not pose a risk to the aquatic or sediment environments. This paper also highlights the many years of research that the surfactant and cleaning products industry has supported, as part of their environmental sustainability commitment, to improve environmental tools, approaches, and develop innovative methods appropriate to address environmental properties of personal care and cleaning product chemicals, many of which have become approved international standard methods.
The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2015-08-08 C Rose,A Parker,B Jefferson,E Cartmell
The safe disposal of human excreta is of paramount importance for the health and welfare of populations living in low income countries as well as the prevention of pollution to the surrounding environment. On-site sanitation (OSS) systems are the most numerous means of treating excreta in low income countries, these facilities aim at treating human waste at source and can provide a hygienic and affordable method of waste disposal. However, current OSS systems need improvement and require further research and development. Development of OSS facilities that treat excreta at, or close to, its source require knowledge of the waste stream entering the system. Data regarding the generation rate and the chemical and physical composition of fresh feces and urine was collected from the medical literature as well as the treatability sector. The data were summarized and statistical analysis was used to quantify the major factors that were a significant cause of variability. The impact of this data on biological processes, thermal processes, physical separators, and chemical processes was then assessed. Results showed that the median fecal wet mass production was 128 g/cap/day, with a median dry mass of 29 g/cap/day. Fecal output in healthy individuals was 1.20 defecations per 24 hr period and the main factor affecting fecal mass was the fiber intake of the population. Fecal wet mass values were increased by a factor of 2 in low income countries (high fiber intakes) in comparison to values found in high income countries (low fiber intakes). Feces had a median pH of 6.64 and were composed of 74.6% water. Bacterial biomass is the major component (25-54% of dry solids) of the organic fraction of the feces. Undigested carbohydrate, fiber, protein, and fat comprise the remainder and the amounts depend on diet and diarrhea prevalence in the population. The inorganic component of the feces is primarily undigested dietary elements that also depend on dietary supply. Median urine generation rates were 1.42 L/cap/day with a dry solids content of 59 g/cap/day. Variation in the volume and composition of urine is caused by differences in physical exertion, environmental conditions, as well as water, salt, and high protein intakes. Urine has a pH 6.2 and contains the largest fractions of nitrogen, phosphorus, and potassium released from the body. The urinary excretion of nitrogen was significant (10.98 g/cap/day) with urea the most predominant constituent making up over 50% of total organic solids. The dietary intake of food and fluid is the major cause of variation in both the fecal and urine composition and these variables should always be considered if the generation rate, physical, and chemical composition of feces and urine is to be accurately predicted.
Prediction of the Fate of Organic Compounds in the Environment From Their Molecular Properties: A Review. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2015-04-14 Laure Mamy,Dominique Patureau,Enrique Barriuso,Carole Bedos,Fabienne Bessac,Xavier Louchart,Fabrice Martin-Laurent,Cecile Miege,Pierre Benoit
A comprehensive review of quantitative structure-activity relationships (QSAR) allowing the prediction of the fate of organic compounds in the environment from their molecular properties was done. The considered processes were water dissolution, dissociation, volatilization, retention on soils and sediments (mainly adsorption and desorption), degradation (biotic and abiotic), and absorption by plants. A total of 790 equations involving 686 structural molecular descriptors are reported to estimate 90 environmental parameters related to these processes. A significant number of equations was found for dissociation process (pKa), water dissolution or hydrophobic behavior (especially through the KOW parameter), adsorption to soils and biodegradation. A lack of QSAR was observed to estimate desorption or potential of transfer to water. Among the 686 molecular descriptors, five were found to be dominant in the 790 collected equations and the most generic ones: four quantum-chemical descriptors, the energy of the highest occupied molecular orbital (EHOMO) and the energy of the lowest unoccupied molecular orbital (ELUMO), polarizability (α) and dipole moment (μ), and one constitutional descriptor, the molecular weight. Keeping in mind that the combination of descriptors belonging to different categories (constitutional, topological, quantum-chemical) led to improve QSAR performances, these descriptors should be considered for the development of new QSAR, for further predictions of environmental parameters. This review also allows finding of the relevant QSAR equations to predict the fate of a wide diversity of compounds in the environment.
Coagulant Recovery from Water Treatment Residuals: A Review of Applicable Technologies. Crit. Rev. Environ. Sci. Technol. (IF 5.980) Pub Date : 2015-06-13 J Keeley,P Jarvis,S J Judd
Conventional water treatment consumes large quantities of coagulant and produces even greater volumes of sludge. Coagulant recovery (CR) presents an opportunity to reduce both the sludge quantities and the costs they incur, by regenerating and purifying coagulant before reuse. Recovery and purification must satisfy stringent potable regulations for harmful contaminants, while remaining competitive with commercial coagulants. These challenges have restricted uptake and lead research towards lower-gain, lower-risk alternatives. This review documents the context in which CR must be considered, before comparing the relative efficacies and bottlenecks of potential technologies, expediting identification of the major knowledge gaps and future research requirements.