A new multimedia contaminant fate model for China: how important are environmental parameters in influencing chemical persistence and long-range transport potential?

The occurrence and sources of PAHs, oxygenated PAHs (OPAHs), and nitrated PAHs (NPAHs) in soil and vegetation from the Antarctic, Arctic, and Tibetan Plateau

Although the fate of PAHs in the three polar regions (Antarctic, Arctic, and Tibetan Plateau) has been investigated, the occurrence and contamination profiles of PAH derivatives such as oxygenated PAHs (OPAHs) and nitrated PAHs (NPAHs) remain unclear. Some of them are more toxic and can be transformed from PAHs in environment. This study explored and compared the concentrations composition profiles and potential sources of PAHs, OPAHs, and NPAHs in soil and vegetation samples from the three polar regions. The total PAH, OPAH, and NPAH concentrations were 3.55-519, n.d.-101, and n.d.-1.10 ng/g dry weight (dw), respectively. The compounds were dominated by three-ring PAHs, and the most abundant individual PAH and OPAH were phenanthrene (PHE) and 9-fluorenone (9-FO), respectively. The sources of PAHs and their derivatives were qualitatively analyzed by the diagnostic ratios and quantified using the positive matrix factorization (PMF) model. The ratios of PAH derivatives to parent PAHs (9-FO/fluorene and 9,10-anthraquinone/anthracene) were significantly higher in the Antarctic samples than in the Arctic and TP samples, implying a higher occurrence of secondary OPAH and NPAH formation in the Antarctic region. To our knowledge, this is the first comparative study that simultaneously investigated the contamination profiles of PAHs and their derivatives in the three polar regions. The findings of this study provide a scientific basis for the development of risk assessment and pollution control strategies in these fragile regions.

Indirect Emissions from Organophosphite Antioxidants Result in Significant Organophosphate Ester Contamination in China

Organophosphite antioxidants (OPAs) have been seriously neglected as potential sources of organophosphate esters (OPEs) in environments. This study utilizes a modeling approach to quantify for the first time national emissions and multimedia distributions of triphenyl phosphate (TPHP)─a well-known flame retardant─and three novel OPEs: tris(2,4-ditert-butylphenyl) phosphate (AO168═O), bis(2,4-ditert-butylphenyl) pentaerythritol diphosphate (AO626═O2), and trisnonylphenol phosphate (TNPP). Emphasis is on the quantitative assessment of OPA source in China. TPHP has 1.1-9.7 times higher emission (300 Mg/year in 2019 with half from OPA sources) than AO168═O (278 Mg/year), AO626═O2 (53 Mg/year), and TNPP (32 Mg/year), but AO168═O is predominant in environments (63-79%) except freshwaters. About 72-99% of the studied OPEs are emitted via air, with 88-99% ultimately distributed into soils as the major sink. OPA-source emissions contribute 9.5-57% and 4.7-56% of TPHP masses and concentrations (except in sediments) in different media, respectively. Both AO168═O and AO626═O2 exhibit high overall persistence ranging between 2 and 11 years. Source emissions and environmental concentrations are elevated in economically developed areas, while persistence is higher in northern areas, where precipitation and temperature are lower. This study shows the significance of the sources of OPA to OPE contamination, which supports chemical management of these substances.

Indoor exposure to selected flame retardants and quantifying importance of environmental, human behavioral and physiological parameters

Indoor exposure to organic flame retardants (FRs) has raised extensive concern due to associated adverse health effects. Indoor-exposure induced daily intakes of six widely used FRs individually ranged 0.002-611 ng/day and 0.02-463 ng/day, respectively, for adults and 2-6-year-old children; and resulting internal exposure levels ranged 0.1-159 and 2.1-4500 ng/g lipid, respectively. A proportion of 0.001-5.9% and 0.006-10.3% of individual FRs emitted into indoor air ultimately entered bodies of adults and children respectively. Tris(2-chloroisopropyl)phosphate dominated in emissions, whilst 2-ethylhexyl-2,3,4,5-tetrabromobenzoate dominated in human bodies. Hand-to-mouth contact was the most important exposure pathway for less volatile FRs including most brominated FRs, whilst inhalation was the predominant intake pathway of tris(2-chloroisopropyl)phosphate. Relative importance of 29 environmental, behavioral and physiological parameters was ranked to explore key drivers influencing exposure and accumulation of FRs in humans. Results suggested that frequent bathing and handwashing can reduce exposure effectively, especially for children. Bodyweight and lipid fraction were only positively related to internal accumulation and body-weight-normalized concentrations of compounds with low metabolic rates (half-lives ≥10³ h) in humans. Our findings help control indoor exposure to FRs and are supportive of human exposome studies in the future.

An improved method to predict polycyclic aromatic hydrocarbons in surface freshwater by reducing the input parameters

Predicting the concentration of polycyclic aromatic hydrocarbons (PAHs) in surface freshwater are critical for understanding their spatio-temporal distribution, regulation effectiveness, and the subsequent health risks. In this study, by exploring the correlation of PAHs concentrations in surface freshwater (C_PAHs) in China reported in the past twenty years with their emission (E_PAHs), a novel relationship of C_PAHs with E_PAHs and PAHs properties (i.e., logK_ow and S_w) was established. For PAHs individual, percent sample deviation between the measured concentrations and the calculated concentrations are in the range of 18% to 48%, suggesting that the calculated concentrations of PAHs are well consistent with the measured PAHs concentration in surface freshwater. Moreover, spatial distribution of predicted PAHs concentrations in surface freshwater of China is also matched well with measured ones. Compared with other environmental models, the established relationships in this work can reduce the number of model parameters from dozens to three, as well as decrease percent sample deviation from several orders of magnitude to less than 50%. The established relationship of PAHs concentrations in surface freshwater with E_PAHs, S_w, and logK_ow of PAHs, are valuable to facilitate the prediction of PAHs concentrations in surface freshwater by reducing monitoring costs.

Forests effects on the environmental fates of organic pollutants in a tropical watershed

Poly-brominated diphenyl ethers (PBDEs), dioxins, furans and current-use pesticides (CUPs) are common organic pollutants that have received global scrutiny due to their association with adverse environmental and health impacts. However, there is limited previous work assessing their environmental fates in the context of tropical multi-use watersheds. The aim of this study was to estimate the effect of forests on long-term environmental fate for some PBDEs, dioxins, furans and CUPs for a case study watershed of a tropical developing country (the Rio Cobre River drainage basin, Jamaica). Specifically, a dynamic, 16-compartment environmental multimedia model, RioShed, was developed and applied to calculate compartmental concentrations, as well as some long-term environmental fate metrics. Results indicate that the presence of tropical forests, especially those that are evergreen, reduced the atmospheric concentrations, atmospheric long-range transport potential, and the overall persistence of the study pollutants. Reductions in atmospheric concentrations by tropical forests were most enhanced for the more polar CUPs. Forest parameters that notably influenced soil concentration and/or overall persistence included the canopy drip parameter, the leaf area index and the wax erosion rate. The results of this research are expected to inform land-use and environmental management of the study area and similar tropical regions.

A regional numerical environmental multimedia modeling approach to assess spatial Eco-Environmental exposure risk of perfluorooctane sulfonate (PFOS) in the Pearl river basin

This paper presents a novel numerical environmental multimedia modeling system (RNEMM) for assessing the environmental fate of emerging organic contaminants and their relative health risk at a regional scale. The RNEMM is developed based on an integrated numerical algorithm that comprises four sub-models: a river network simulation module, a gaseous phase simulation module, a mass balance based simulation module for soil compartment, and a food web analysis module. This RNEMM has been applied to simulate the spatial distribution of PFOS and assess the consequent health risks for a central water basin region of the Pearl River in China. The study region includes the urban areas of Guangzhou, Foshan, and Dongguan Cities with emission sources of PFOS, which was detected in local water, sediments, and air environment. The spatial concentration distributions of PFOS in water, sediment, air, soil, and various fish species are examined based on RNEMM and compared with the measured data. With a focus on water environment, it shows that the simulated results essentially agree well with measured concentrations. Comparing the simulated results and the measured data collected in 2013, the relative errors are mostly less than 40 % in the surface water and sediment zones for this regional scale field study. Whereas the relative error in the atmosphere zone is less than 5%. In addition, the health risk assessment for children and adults is conducted based on the RNEMM approach. The hazard quotient (HQ) values for the 95th percentile in most subareas of the study region are higher than 0.1, showing a low-risk level for the study period. The results indicate that the RNEMM is a useful modeling tool to manage the environmental and health risks associated with emerging contaminants on regional air, water, soil, and ecosystem at an adequate spatial-temporal resolution.

Spatially resolved environmental fate models: A review

Spatially resolved environmental models are important tools to introduce and highlight the spatial variability of the real world into modeling. Although various spatial models have been developed so far, yet the development and evaluation of these models remain a challenging task due to several difficulties related to model setup, computational cost, and obtaining high-resolution input data (e.g., monitoring and emission data). For example, atmospheric transport models can be used when high resolution predicted concentrations in atmospheric compartments are required, while spatial multimedia fate models may be preferred for regulatory risk assessment, life cycle impact assessment of chemicals, or when the partitioning of chemical substances in a multimedia environment is considered. The goal of this paper is to review and compare different spatially resolved environmental models, according to their spatial, temporal and chemical domains, with a closer insight into spatial multimedia fate models, to achieve a better understanding of their strengths and limitations. This review also points out several requirements for further improvement of existing models as well as for their integration.

Distribution and Potential Sources of OCPs and PAHs in Waters from the Danshui River Basin in Yichang, China

To investigate the concentrations, spatial distribution, potential sources and mass fluxes of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in waters from the Danshui River Basin, a total of 20 water samples were collected and analyzed from a karstic river in Western Hubei of Central China. The average concentrations of total OCPs and PAHs in the river water were 4719 pg·L^-1 and 26.2 ng·L^-1, respectively. The characteristic ratios of different isomers and the composition analysis of individual OCPs and PAHs revealed that HCHs originated from a mixed input of technical HCHs and Lindane, DDTs were mainly from technical DDTs, and PAHs mainly originated from biomass and coal combustion. The mass flux analysis showed that PAHs had a higher emission and heavier burden than OCPs in the Danshui River Basin. OCPs and PAHs emitted from agricultural or other human activities could enter the groundwater and then be transported to the surface/river water in the karst area. The adsorption of OCPs and PAHs by particles and the sedimentation of particles could be the primary processes to intercept these pollutants in the water of the karstic river system.

Evaluation of PAHs in edible parts of vegetables and their human health risks in Jinzhong City, Shanxi Province, China: A multimedia modeling approach

Knowledge of the origins of polycyclic aromatic hydrocarbon (PAH) in vegetables is essential to reduce human health risks induced by dietary exposure. The current study developed a vegetation-advanced multimedia model, SESAMe-Veg, to identify the major uptake pathway of 15 priority PAHs in vegetables and assess the PAHs in edible parts of cabbages and carrots in Jinzhong City, Shanxi Province, China. The model was well evaluated against site- and plant-specific measurements. Edible parts exhibited lower PAH concentrations than the other parts for both vegetables. The estimated concentrations of ΣPAH15 were 79 ng/g in cabbage shoots and 83 ng/g in carrot roots. Higher concentrations were estimated in shoots of the leafy vegetable than in roots of the root vegetable for most PAHs. Although air-shoot is the major transport pathway, 98% was deposition of particles, which was attached outside and could be removed relatively easily by washing. Soils might be the origin of PAHs inside vegetables, especially for lighter PAHs. PYR was more likely to be stored in roots than other congeners. The translocation of PAHs inside vegetables was negligible. Adulthood dietary exposure to local vegetables probably caused a high health risk; however, contributions from consuming cabbages and especially carrots were low. Females generally exhibited slightly higher risks than males of exposure to PAHs in local vegetables. Considering the dominant role of particle deposition, carefully vegetable washing before ingestion could reduce this risk. This study has provided a functional tool to evaluate vegetable contamination by PAHs. CAPSULE: A vegetation-advanced multimedia model of PAHs in different parts of vegetables and other environmental media was developed to evaluate the potential health risk to local populations of different sexes and ages via vegetable ingestion.

Inter-regional multimedia fate analysis of PAHs and potential risk assessment by integrating deep learning and climate change scenarios

Polycyclic aromatic hydrocarbons (PAHs) are hazardous compounds associated with respiratory disease and lung cancer. Increasing fossil fuel consumption, which causes climate change, has accelerated the emissions of PAHs. However, potential risks by PAHs have not been predicted for Korea, and appropriate PAH regulations under climate change have yet to be developed. This study assesses the potential risks posed by PAHs using climate change scenarios based on deep learning, and a multimedia fugacity model was employed to describe the future fate of PAHs. The multimedia fugacity model describes the dynamics of sixteen PAHs by reflecting inter-regional meteorological transportation. A deep neural network predicts future environmental and economic conditions, and the potential risks posed by PAHs, in the year 2050, using a prediction model and climate change scenarios. The assessment indicates that cancer risks would increase by more than 50%, exceeding the lower risk threshold in the southern and western regions. A mix of strategies for developing PAH regulatory policies highlighted the necessity of increasing PAHs monitoring stations and controlling fossil fuel usage based on the domestic and global conditions under climate change scenarios.

Cross-interface transfer of polycyclic aromatic hydrocarbons (PAHs) in a shallow urban lake in Shanghai, China based on the fugacity model

Shallow urban lakes are important urban ecosystems; however, these systems are subject to severe polycyclic aromatic hydrocarbons (PAHs) contamination. An understanding of the distribution and dynamics of PAHs in lakes is required to restore the functions of lake ecosystems and to ensure the ecological security of urban water sources. The Quantitative Water Air Sediment Interaction (QWASI) model and partition coefficient and fugacity fraction methods were applied to estimate the multimedia transfers of PAHs in Dianshan Lake, a typical shallow lake in Shanghai, China. In addition, some new concepts and methods related to PAH transfers were introduced. The results showed that while the gas-solid partition in the area remained in non-equilibrium, the influence of pollution sources tended to weaken. Atmospheric advection was the main source of PAHs to the lake, and a portion of the net loss of advection was transformed into total flux of cross-interface transfers, in which transport fluxes from air to water and from water to sediment were dominant, with a significant correlation between the two types of transfer. The large resuspension of high molecular weight (HMW)-PAHs occurred, possibly related to frequent hydrodynamic disturbances. Furthermore, this study explored the distribution of PAHs among different compartments and the seasonal variation of multimedia transfers. Sensitivity analysis showed that the model is remarkably sensitive to four parameters including temperature and advection. Monte Carlo uncertainty analysis verified that the simulation results were stable and reliable. The results can provide a theoretical basis for the monitoring and control of shallow lake pollution.

Partition and Fate of Phthalate Acid Esters (PAEs) in a Full-Scale Horizontal Subsurface Flow Constructed Wetland Treating Polluted River Water

When used as highly produced chemicals and widely used plasticizers, Phthalate acid esters (PAEs) have potential risks to human life and the environment. In this study, to assess the distribution and fate of PAEs, specifically inside a full-scale horizontal subsurface flow constructed wetland, four PAEs including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), and bis (2-ethylhexyl) phthalate (DEHP) were investigated. In effluent, PAEs concentration decreased 19.32% (DMP), 19.18% (DEP), 19.40% (DBP), and 48.56% (DEHP), respectively. Within the wetland, PAEs partitioned in water (0.18–1.12 μg/L, 35.38–64.92%), soil (0.44–5.08 μg/g, 1.02–31.33%), plant (0.68–48.6 μg/g, 0.85–36.54%), air and biological transformation (2.72–33.21%). The results indicated that soil and plant adsorption contributed to the majority of PAE removal, digesting DMP (19.32%), DEP (19.18%), DBP (19.40%), and DEHP (48.56%) in constructed wetlands. Moreover, the adsorption was affected by both octanol/water partition coefficient (Kow) and transpiration stream concentration factors (TSCF). This work, for the first time, revealed the partition and fate of PAEs in constructed wetlands to the best of our knowledge.

A review of multimedia transport and fate models for chemicals: Principles, features and applicability

The frequent use of chemicals has caused ecosystems and humans to be threatened due to their discharge into the environment. Multimedia environmental fate models could provide a comprehensive picture of transport behaviour and fate for organic chemicals in multiple environmental media. They have been designed and widely used for chemical risk assessment, chemical ranking and management support, and determination of chemical bioaccumulation. This study reviewed the principles, features and applicability of recent commonly used multimedia fate models from peer-reviewed literature. Fugacity-based and concentration-based models are now widely adopted for use in chemical fate evaluation, while they are more appropriate for volatile and semi-volatile chemicals. Or the fugacity-based models can use aquivalence equilibrium criterion to cations, anions and involatile chemicals. The MAMI and SESAMe models based on activity approach are applicable to neutral and ionizable molecules. However, interactions of ionic species with other water solutes are not taken into account in these models. Additionally, they could not directionally simulate how chemicals transported form one grid to another. Future attention should be focused on the reliability of transfer behaviour and fate of ionizable chemicals, as integrating the advantages of these two kinds of models into a reconstructed one may be a better choice. In a word, environmental multimedia models have been beneficial tools for chemical control and management, risk and effect estimation, and decision supporting.

A multimedia fugacity model to estimate the fate and transport of polycyclic aromatic hydrocarbons (PAHs) in a largely urbanized area, Shanghai, China

Increasing PAHs pollution is creating more complex urban pollution system. However, the availability of sufficient monitoring activities for PAHs in multicompartment and corresponding multi-interface migration processes is still not well understood. In this study, a Level III steady state fugacity model was validated to evaluate the detailed local variations, and mass fluxes of PAHs in various environmental compartments (i.e., air, soil, sediment, water, vegetation and organic film). This model was applied to a region of Shanghai in 2012 based on a large number of measured data and brings model predictions in 2020. The model results indicate that most of the simulated concentrations agreed with the observed values within one order of magnitude with a tendency of underestimation for vegetation. Direct emission is the main input pathway of PAHs entering the atmosphere, whereas advection is the main outward flow from Shanghai. Organic film was achieved the highest concentration of PAHs compared to other compartments up to 58.17 g/m³. The soil and sediment served as the greatest sinks of PAHs and have the longest retention time (2421.95-78642.09 h). Importantly, a decreasing trend of PAHs was observed in multimedia from 2012 to 2020 and the transfer flux from the air to vegetation to soil was the dominant pathways of BaP intermedia circulation processes. A sensitivity analysis showed that temperature was the most influential parameter, especially for Phe. A Monte Carlo simulation emphasized heavier PAHs were overpredicted in film and sediment, but lighter PAHs in air and water were generally underestimated.

Multimedia modeling of the PAH concentration and distribution in the Yangtze River Delta and human health risk assessment

Emissions of polycyclic aromatic hydrocarbons (PAHs) in China remain at a high level compared to those in developed countries. The Yangtze River Delta (YRD) is an economic and industrial center in China with an extremely large population. The potentially high emissions and excess cancer risk from human exposure in this region cannot be neglected. This study applied a multimedia model to estimate the concentrations of 16 US EPA priority PAHs in the environment in the YRD with a well-developed PAH-emission inventory for 2014. The model predicted that the average concentrations of ΣPAHs were 274 ng/m³ in the air, 255 ng/g in the soil, 15 ng/g in vegetation, 147 ng/L in freshwater and 144 ng/g in sediment, as well as 99 ng/L and 80 ng/g in seawater and sediment, respectively. Soil is the PAH sink in this region, and the net flux of the total PAHs is always from air to soil for each isomer. A deterministic assessment observed that the ELCR (excess lifetime cancer risk) ranged from 2.5 × 10^-6 to 3.0 × 10^-5 for exposure by air inhalation and from 3.5 × 10^-7 to 7.9 × 10^-6 for exposure by soil ingestion. The probabilistic results did not find any probability of ELCR >10^-4 by exposure via soil ingestion in the YRD. The probabilistic ELCR induced by inhalation exposure varied from 8.1 × 10^-7 to 3.1 × 10^-4 in the YRD. This study provided a comprehensive overview of PAHs occurrence in natural environments and of the relevant human health risks. The information presented in this study could help authorities to enact a strategy regarding emission reduction and pollution control relevant to PAHs.

CAPSULE

Multimedia modeling predicted distributions and compositions of PAHs in different environmental compartments, and deterministic and probabilistic ELCRs induced by air inhalation and soil ingestion were also provided.

Drivers of contaminant levels in surface water of China during 2000-2030: Relative importance for illustrative home and personal care product chemicals

Water pollution are among the most critical problems in China and emerging contaminants in surface water have attracted rising attentions in recent years. There is great interest in China's future environmental quality as the national government has committed to a major action plan to improve surface water quality. This study presents methodologies to rank the importance of socioeconomic and environmental drivers to the chemical concentration in surface water during 2000-2030. A case study is conducted on triclosan, a home and personal care product (HPCP) ingredient. Different economic and discharge flow scenarios are considered. Urbanization and wastewater treatment connection rates in rural and urban areas are collected or projected for 2000-2030 for counties across China. The estimated usage increases from ca. 86 to 340 t. However, emissions decreases from 76 to 52 t during 2000-2030 under a modelled Organisation for Economic Co-operation (OECD) economic scenario because of the urbanization, migration and development of wastewater treatment plants/facilities (WWTPs). The estimated national median concentration of triclosan ranges 1.5-8.2 ng/L during 2000-2030 for different scenarios. It peaks in 2009 under the OECD and three of the Intergovernmental Panel on Climate Change (IPCC), A2, B1 and B2 economic scenarios, but in 2025 under A1 economic scenario. Population distribution and surface water discharge flow rates are ranked as the top two drivers to triclosan levels in surface water over the 30 years. The development of urban WWTPs was the most important driver during 2000-2010 and the development of rural works is projected to be the most important in 2011-2030. Projections suggest discharges of ingredients in HPCPs - controlled by economic growth - should be balanced by the major expenditure programme on wastewater treatment in China.

Environmental fate and exposure models: advances and challenges in 21st century chemical risk assessment

Environmental fate and exposure models are a powerful means to integrate information on chemicals, their partitioning and degradation behaviour, the environmental scenario and the emissions in order to compile a picture of chemical distribution and fluxes in the multimedia environment. A 1995 pioneering book, resulting from a series of workshops among model developers and users, reported the main advantages and identified needs for research in the field of multimedia fate models. Considerable efforts were devoted to their improvement in the past 25 years and many aspects were refined; notably the inclusion of nanomaterials among the modelled substances, the development of models at different spatial and temporal scales, the estimation of chemical properties and emission data, the incorporation of additional environmental media and processes, the integration of sensitivity and uncertainty analysis in the simulations. However, some challenging issues remain and require research efforts and attention: the need of methods to estimate partition coefficients for polar and ionizable chemical in the environment, a better description of bioavailability in different environments as well as the requirement of injecting more ecological realism in exposure predictions to account for the diversity of ecosystem structures and functions in risk assessment. Finally, to transfer new scientific developments into the realm of regulatory risk assessment, we propose the formation of expert groups that compare, discuss and recommend model modifications and updates and help develop practical tools for risk assessment.

DGT Passive Sampling for Quantitative in Situ Measurements of Compounds from Household and Personal Care Products in Waters

Widespread use of organic chemicals in household and personal care products (HPCPs) and their discharge into aquatic systems means reliable, robust techniques to monitor environmental concentrations are needed. The passive sampling approach of diffusive gradients in thin-films (DGT) is developed here and demonstrated to provide in situ quantitative and time-weighted average (TWA) measurement of these chemicals in waters. The novel technique is developed for HPCPs, including preservatives, antioxidants and disinfectants, by evaluating the performance of different binding agents. Ultrasonic extraction of binding gels in acetonitrile gave good and consistent recoveries for all test chemicals. Uptake by DGT with HLB (hydrophilic-lipophilic-balanced) as the binding agent was relatively independent of pH (3.5-9.5), ionic strength (0.001-0.1 M) and dissolved organic matter (0-20 mg L^-1), making it suitable for applications across a wide range of environments. Deployment time and diffusion layer thickness dependence experiments confirmed DGT accumulated chemicals masses are consistent with theoretical predictions. The technique was further tested and applied in the influent and effluent of a wastewater treatment plant. Results were compared with conventional grab-sampling and 24-h-composited samples from autosamplers. DGT provided TWA concentrations over up to 18 days deployment, with minimal effects from biofouling or the diffusive boundary layer. The field application demonstrated advantages of the DGT technique: it gives in situ analyte preconcentration in a simple matrix, with more quantitative measurement of the HPCP analytes.

Application of a spatially resolved model to contextualise monitoring data for risk assessment of down-the-drain chemicals over large scales

Many regulatory screening level exposure assessments are based on simple large scale conceptual scenarios. However, exposure, and therefore risks associated with chemicals, are characterised by high spatial variability. The Scenario assembly tool (ScenAT) is a global screening level model to enable spatially resolved local predictions of environmental concentrations of home and personal care chemicals. It uses the European Union Technical Guidance Document (TGD) equation to predict local scale freshwater concentrations (predicted environmental concentrations - PECs) of chemicals discharged via wastewater. ScenAT uses Geographic Information System (GIS) layers for the underlying socio-economic (population) and environmental parameters (per capita water use, sewage treatment plant connectivity, dilution factor). Using a probabilistic approach, we incorporate sources of uncertainty in the input data (tonnage estimation, removal in sewage treatment plants and seasonal variability in dilution factors) for two case-study chemicals: the antimicrobial triclosan (TCS) and the anionic surfactant linear alkylbenzene sulphonate (LAS). We then compare model estimates of wastewater and freshwater concentrations of TCS and LAS to UK monitoring data. Comparison showed that modeled PECs were on average higher than mean measured data for TCS and LAS by a factor 1.8 and 1.4, respectively. Considering the uncertainty associated with both model and monitoring data, the use of a probabilistic approach using the ScenAT model for screening assessment is reasonable. The combination of modelled and monitoring data enables the contextualisation of monitoring data. Spatial PECs can be used to identify areas of elevated concentration for further refined assessment.

Occurrence of nitro- and oxy-PAHs in agricultural soils in eastern China and excess lifetime cancer risks from human exposure through soil ingestion

The quality of agricultural soil is vital to human health, however soil contamination is a severe problem in China. Polycyclic aromatic hydrocarbons (PAHs) have been found to be among the major soil contaminants in China. PAH derivatives could be more toxic but their measurements in soils are extremely limited. This study reports levels, spatial distributions and compositions of 11 nitrated (nPAHs) and 4 oxygenated PAHs (oPAHs) in agricultural soils covering 26 provinces in eastern China to fill the data gap. The excess lifetime cancer risk (ELCR) from the exposure to them in addition to 21 parent PAHs (pPAHs) via soil ingestion has been estimated. The mean concentration of ∑nPAHs and ∑oPAHs in agricultural soils is 50±45μg/kg and 9±8μg/kg respectively. Both ∑nPAHs and ∑oPAHs follow a similar spatial distribution pattern with elevated concentrations found in Liaoning, Shanxi, Henan and Guizhou. However if taking account of pPAHs, the high ELCR by soil ingestion is estimated for Shanxi, Zhejiang, Liaoning, Jiangsu and Hubei. The maximum ELCR is estimated at ca.10^-5 by both deterministic and probabilistic studies with moderate toxic equivalent factors (TEFs). If maximum TEFs available are applied, there is a 0.2% probability that the ELCR will exceed 10^-4 in the areas covered. There is a great chance to underestimate the ELCR via soil ingestion for some regions if only the 16 priority PAHs in agricultural soils are considered. The early life exposure and burden are considered extremely important to ELCR. Emission sources are qualitatively predicted and for areas with higher ELCR such as Shanxi and Liaoning, new loadings of PAHs and derivatives are identified. This is the first large scale study on nPAHs and oPAHs contamination levels in agricultural soils in China. The risk assessment based on this underpins the policy making and is valuable for both scientists and policy makers.

Toward refined environmental scenarios for ecological risk assessment of down-the-drain chemicals in freshwater environments

Current regulatory practice for chemical risk assessment suffers from the lack of realism in conventional frameworks. Despite significant advances in exposure and ecological effect modeling, the implementation of novel approaches as high-tier options for prospective regulatory risk assessment remains limited, particularly among general chemicals such as down-the-drain ingredients. While reviewing the current state of the art in environmental exposure and ecological effect modeling, we propose a scenario-based framework that enables a better integration of exposure and effect assessments in a tiered approach. Global- to catchment-scale spatially explicit exposure models can be used to identify areas of higher exposure and to generate ecologically relevant exposure information for input into effect models. Numerous examples of mechanistic ecological effect models demonstrate that it is technically feasible to extrapolate from individual-level effects to effects at higher levels of biological organization and from laboratory to environmental conditions. However, the data required to parameterize effect models that can embrace the complexity of ecosystems are large and require a targeted approach. Experimental efforts should, therefore, focus on vulnerable species and/or traits and ecological conditions of relevance. We outline key research needs to address the challenges that currently hinder the practical application of advanced model-based approaches to risk assessment of down-the-drain chemicals. Integr Environ Assess Manag 2017;13:233-248. © 2016 SETAC.

Development of a multimedia model (POPsLTEA) to assess the influence of climate change on the fate and transport of polycyclic aromatic hydrocarbons in East Asia

A dynamic multimedia model (POPsLTEA) for an East Asia region was developed and evaluated to quantitatively assess how climate change (CC) alters the environmental fate and transport dynamics of 16 polycyclic aromatic hydrocarbons (PAHs) in air, water, soil, and sediment. To cover the entire model domain (25°N-50°N and 98°E-148°E) where China, Japan, and South and North Koreas are of primary concern, a total of 5000 main cells of 50km×50km size were used while 1008 cells of a finer spatial resolution (12.5km×12.5km) was nested for South Korea (33°N-38°N and 126°E-132°E). Most of the predicted concentrations agreed with the observed values within one order of magnitude with a tendency of overestimation for air and sediment. Prediction of the atmospheric concentration was statistically significant in both coincidence and association, suggesting the model's potential to successfully predict the fate and transport of the PAHs as influenced by CC. An example study of benzo(a)pyrene demonstrates that direction and strength of the CC influence on the pollution levels vary with the location and environmental media. As compared to the five year period of 2011 to 2015, the changes across the model domain in the annual geometric mean concentration over the years of 2021 through 2100 were predicted to range from 88% to 304%, from 84% to 109%, from 32% to 362%, and from 49% to 303%, in air, soil, surface water, and sea water, respectively, under the scenario of RCP8.5.

A Multimedia Fate Model to Support Chemical Management in China: A Case Study for Selected Trace Organics

SESAMe v3.3, a spatially explicit multimedia fate model for China, is a tool suggested to support quantitative risk assessment for national scale chemical management. The key advantage over the previous version SESAMe v3.0 is consideration of spatially varied environmental pH. We evaluate the model performance using estimates of emission from total industry usage of three UV filters (benzophenone-3, octocrylene, and octyl methoxycinnamate) and three antimicrobials (triclosan, triclocarban, and climbazole). The model generally performs well for the six case study chemicals as shown by the comparison between predictions and measurements. The importance of accounting for chemical ionization is demonstrated with the fate and partitioning of both triclosan and climbazole sensitivity to environmental pH. The model predicts ionizable chemicals (triclosan, climbazole, benzophenone-3) to primarily partition into soils at steady state, despite hypothetically only being released to freshwaters, as a result of agricultural irrigation by freshwater. However, further model calibration is needed when more field data becomes available for soils and sediments and for larger areas of water. As an example, accounting for the effect of pH in the environmental risk assessment of triclosan, limited freshwater areas (0.03% or ca. 55 km(2)) in mainland China are modeled to exceed its conservative environmental no-effect threshold. SESAMe v3.3 can be used to support the development of chemical risk assessment methodologies with the spatial aspects of the model providing a guide to the identification regions of interest in which to focus monitoring campaigns or develop a refined risk assessment.

Environmental Distributions of Benzo[a]pyrene in China: Current and Future Emission Reduction Scenarios Explored Using a Spatially Explicit Multimedia Fate Model

SESAMe v3.0, a spatially explicit multimedia fate model with 50 × 50 km(2) resolution, has been developed for China to predict environmental concentrations of benzo[a]pyrene (BaP) using an atmospheric emission inventory for 2007. Model predictions are compared with environmental monitoring data obtained from an extensive review of the literature. The model performs well in predicting multimedia concentrations and distributions. Predicted concentrations are compared with guideline values; highest values with some exceedances occur mainly in the North China Plain, Mid Inner Mongolia, and parts of three northeast provinces, Xi'an, Shanghai, and south of Jiangsu province, East Sichuan Basin, middle of Guizhou and Guangzhou. Two potential future scenarios have been assessed using SESAMe v3.0 for 2030 as BaP emission is reduced by (1) technological improvement for coal consumption in energy production and industry sectors in Scenario 1 (Sc1) and (2) technological improvement and control of indoor biomass burning for cooking and indoor space heating and prohibition of open burning of biomass in 2030 in Scenario 2 (Sc2). Sc2 is more efficient in reducing the areas with exceedance of guideline values. Use of SESAMe v3.0 provides insights on future research needs and can inform decision making on options for source reduction.