Probabilistic ecological risk assessment of DDTs in the Bohai Bay based on a food web bioaccumulation model

The screening of priority pollutants in the Bohai Sea based on ecological risk assessment

The Bohai Sea (BS) is a semi-enclosed inland sea and China's most polluted coastal sea. With the rapid economic development of the circum-Bohai Sea region, large amounts of pollutants have been discharged into the BS, posing a significant threat to human health and the ecosystem. Great efforts have been made on investigating the levels of various pollutants in the BS; however, the priority pollutants which are required for the implementation of suitable environmental management and remediation measures in this system remain unclear. By using the risk quotient method, this study evaluated the ecological risks of various pollutants (including antibiotics, heavy metals, total petroleum hydrocarbons (TPHs), endocrine disruptors, pesticides, and persistent organic pollutants) in BS water and sediments over the past twelve years to identify the priority pollutants in this system. The results showed that 8 and 10 pollutants were at risk in BS water and sediments, respectively. Overall, 13 pollutants (arsenic (As), copper (Cu), mercury (Hg), nickel (Ni), chromium (Cr), lead (Pb), zinc (Zn), cadmium (Cd), TPHs, bisphenol A (BPA), erythromycin, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs)) in the BS were identified to have potential risks and should be included in the list of priority pollutants. The monitoring of the changes in the contents of these pollutants in BS water and sediments needs to be strengthened in the future.

Food web bioaccumulation model for ecological risk assessment of emerging organic pollutants in marine ecosystems: Principles, advances and challenges

The bioaccumulation and trophic transfer of pollutants in marine ecosystem members determine their ultimate ecological risks. Food web bioaccumulation models are widely used in scientific and regulatory programs to assess the bioaccumulation and ecological risks of pollutants at the ecosystem scale. The food web models are mainly established through concentration- and fugacity-based modeling approaches and include some chemical, food web-related, physiological and environmental factors. The models applied in the "forward approach" predict bioaccumulation and conduct internal exposure level-based ecological risk assessment (IEL-ERA), whereas those in the "reverse approach" are used to back-calculate the IEL-based predicted no-effect concentrations (PNECs) or environmental criteria. However, some challenges still exist in the application of food web model integrated risk assessment, including the lack of standardized/generalized frameworks, the lack of chemical- and species-specific toxicokinetic data and internal exposure (or tissue residue)-based toxicity data, and the lack of uncertainty-control methods in model estimation and parameterization. There are urgent requirements to improve models, integrate methods and update study designs in the assessment and prediction of "system-scale risks" of marine emerging organic pollutants.

Ecological risk assessment at the food web scale: A case study of a mercury contaminated oilfield

Mercury, particularly methylmercury, can accumulate through food webs and generate high risks for species at higher trophic levels. Inorganic mercury can be methylated into the organic species methylmercury if suitable reducing conditions exist, for example, in hotspots like oilfields. We developed a conceptual model to conduct an ecological risk assessment based on the food web structure of the Shengli oilfield area, China. The model can identify species at risk and elucidate the sources of risks according to their diet. A risk rating criteria was developed based on the food web structure to categorize the different levels of risks for different species. As expected, the results indicate increasing risks for the biota higher in the food web hierarchy. Grasshoppers were mostly at no risk throughout the study area, whereas grubs at southwest were at minimal risks due to local high Hg concentration in the soil. Mantises, which are insect predators, were also at minimal risk. Herbivorous birds with similar feeding habits than grasshoppers were at no risk, but omnivorous and carnivorous birds were at moderate risk. The conceptual model is a useful tool to improve pollution remediation and establish risk control strategies based on ecological risks of the food web rather than just Hg concentrations in the environment.

Assessing ecological risks caused by human activities in rapid urbanization coastal areas: Towards an integrated approach to determining key areas of terrestrial-oceanic ecosystems preservation and restoration

Rapid urbanization and industrialization in the coastal zone have caused increasingly serious impacts on coastal ecosystems. It is necessary to assess the ecological risk caused by human activities to determine key areas of terrestrial-oceanic ecosystems preservation and restoration to ensure sustainable ecological management in the coastal zone. Key areas of ecosystem preservation and restoration were studied through the assessment of the impacts of ecological pressure sources related to human activities from the perspective of terrestrial-oceanic ecosystems, using the habitat risk assessment (HRA) and habitat quality (HQ) models in the Chinese coastal zone. The results showed that the impact of human activities on the terrestrial ecosystems in the South of China was significantly lower than that in the North. An improvement rate of habitat quality was noticed only in the south and central coastal areas when further away from industrial land. Agricultural production, urban expansion, and industrial pollution had major negative impacts on the habitat quality of terrestrial ecosystems in the Chinese coastal zone, and also threatened the health of marine ecosystems. The ecological risks caused by human activities in the offshore areas of northern Shandong and eastern Jiangsu were relatively low. Mineral development in the north, excessive nitrogen and phosphorus emissions from agricultural production in the south, and port operations were important drivers of increased ecological risks in offshore areas. There were regional spatial differences in the key ecosystem preservation and restoration areas. The provinces of Shandong, Jiangsu, Hebei, Liaoning, and Guangdong are key areas for strengthening the preservation and restoration of terrestrial-oceanic ecosystems. This study provides a reference for large-scale territorial spatial planning and ecosystems conservation.

Polycyclic aromatic hydrocarbons (PAHs) in water from three estuaries of China: Distribution, seasonal variations and ecological risk assessment

The distribution, seasonal variations and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in water from three estuaries in Hai River Basin of China, which has been suffering from different anthropogenic pressures, were investigated. In three estuaries, the average concentration of ΣPAHs was the lowest in Luan River estuary, followed by Hai River estuary, and the highest in Zhangweixin River estuary. There were significant seasonal variations in ΣPAHs, the concentrations of ΣPAHs were higher in November than in May and August. The composition profiles of PAHs in different sites were significantly different, and illustrated seasonal variations. Generally, 2-ring (Nap) and 3-ring PAHs (Acp, Fl and Phe) were the most abundant components at most sampling sites in three estuaries. The PAHs in three estuaries were mainly originated from pyrogenic sources. A method based on toxic equivalency factors (TEFs) and risk quotient (RQ) was proposed to assess the ecological risk of ΣPAHs, with the ecological risk of individual PAHs being considered separately. The results showed that the ecological risks caused by ΣPAHs were high in Hai River estuary and Zhangweixin River estuary, and moderate in Luan River estuary. The mean values of ecological risk in August were lower than those in November. The contributions of individual PAHs to ecological risk were different in May, August and November. 3-ring and 4-ring PAHs accounted for much more ecological risk than 2-ring, 5-ring and 6-ring, although the contributions of 5-ring and 6-ring to ecological risk were higher than these to PAHs concentrations.

Linking the environmental loads to the fate of PPCPs in Beijing: Considering both the treated and untreated wastewater sources

The environmental loads of pharmaceutical and personal care products (PPCPs) in Beijing were estimated from direct discharge of untreated wastewater and WWTP treated effluent. The annual environmental loads of 15 PPCP components ranged from 16.3 kg (propranolol) to 9.85 tons (caffeine). A fugacity model was developed to successfully estimate the PPCP pollution based on the estimated environmental load. The modeled results approximated the observed PPCP concentrations in Beijing. The untreated wastewater contributed significantly to PPCP pollution in Beijing, ranging from 46% (propranolol) to 99% (caffeine). The total environmental burden of target PPCPs ranged from 0.90 kg (propranolol) to 536 kg (caffeine). Water is the most important media for the fate of PPCPs. Monte Carlo-based concentration distributions of PPCPs are consistent with the observed results. The most important way to reduce the PPCP pollution is to both improve wastewater collection rate and adopt deep treatment technologies.

Risk assessment of butyltins based on a fugacity-based food web bioaccumulation model in the Jincheng Bay mariculture area: I. Model development

A fugacity-based model was developed to simulate the bioaccumulation of butyltins in the food web of the Jincheng Bay mariculture area. The predicted biological tissue residues of tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) were 0.04-17.09, 0.14-53.54, and 0.27-108.77 ng-Sn g(-1), respectively, and the predicted values in six mollusca agreed well with the measured ones. The lipid-normalized concentrations did not significantly increase across trophic levels, indicating no biomagnification across aquatic food webs. These results were highly consistent with those observed both in the laboratory and field, which had been reported in numerous references. The explanation, from calculating their flux equilibrium in the food web, was that butyltins were primarily taken in via respiration from the water column by marine organisms. The sensitivities of the model parameters were analyzed, revealing that the hydrophobicity of butyltins played the dominant role in their bioaccumulation phenomena. The verified model predictions of the biotic tissue concentrations of the butyltins could be readily applied to perform internal ecological risk and human health risk assessments in this area.

Health and ecological risk-based characterization of soil and sediment contamination in shipyard with long-term use of DDT-containing antifouling paint

Dichlorodiphenyltrichloroethane (DDT) was a frequently occurring type of persistent organic environmental pollutant in China and DDT-containing antifouling paint could be the main contributor of DDT to shipyards and fishing harbors. A field survey was conducted in a shipyard in southern China to investigate the content and distribution of DDT in soil and sediments. Human health and screening-level ecological risk assessments were conducted for DDT contamination in soil and sediments and the results indicated that total DDT in all samples tested exceeded present advisory safe limits. Analysis of the composition and distribution implicated DDT-containing antifouling paint used for ship maintenance as an important source of DDT. Individual and cumulative health risks for residents exceeded the extra lifetime cancer risks of 10(-6) and 10(-5), mainly from exposure to soil, ingestion and dermal contact. DDT in sediments is associated with a high level of toxicity for the benthic community when >99% of samples exceed the threshold concentration likely to be responsible for effects and severe effects. Further risk control for DDT is required to ensure safety for human health, the benthic community and the environment.

The pollution and ecological risk of endosulfan in soil of Huai'an city, China

Endosulfan, a persistent organic pollutant newly listed under the Stockholm Convention, is currently widely produced and used as a pesticide in China. Concentrations of endosulfans (including α-, β-isomers, and their metabolite endosulfan sulfate) were determined in surface soil collected from Huai'an city, where the largest endosulfan producer is located. The concentrations of Σendosulfan (sum of α-endosulfan, β-endosulfan, and endosulfan sulfate) at all sites ranged from 0.28 to 44.81 ng/g dry weight (dw), following a lognormal distribution. The geometric mean was 1.09 ng/g dw, and the geometric standard deviation was 3.02. The β-endosulfan levels were consistently greater than those of α-isomer. The concentration ratios of α-endosulfan to β-endosulfan ranged from 0.03 to 0.70, which were much lower than the commercial endosulfan mixture. This is because that α-endosulfan is more volatile and degrades faster than β-endosulfan in soil. The contour map of Σendosulfan levels in soil indicates that the factory was the point pollution source with the highest endosulfan level in its surrounding area, especially the southern area. However, the non-point agricultural sources are more important. Based on Monte Carlo simulation, the Σendosulfan inventory in soil in Huai'an is estimated to be 0.8-3.0 tons. In order to understand the potential ecological risk of endosulfan, the Monte Carlo-based hazard quotient distribution was estimated and showed that Σendosulfan posed a potentially high risk to soil organisms. To our knowledge, this study is the first that reports soil pollution and risk of endosulfan around the manufacturer in China. This study will help China's implementation of Stockholm Convention for the reduction and elimination of endosulfan in future.

Transfer of PCBs from bottom sediment to freshwater river fish: a food-web modelling approach in the Rhône River (France) in support of sediment management

Since 2005, restrictions have been because of fish consumption along the Rhone River because of high polychlorobiphenyl (PCB) concentrations, which have resulted inadverse economic consequences for professional fisheries in affected areas. French environmental authorities have expended considerable efforts to research sediment remediation strategies and development of sediment quality guidelines designed to protect the health of humans consuming Rhône River fish. Here we: (1) develop a bioaccumulation food-web model that describes PCB concentrations in three common freshwater fish species of the Rhône River, using Bayesian inference to estimate the input parameters; (2) test the predictive power of the model in terms of risk assessment for fish consumption; and (3) discuss the use of this approach to develop sediment quality guidelines that protect the health of humans consuming Rhône River fish. The bioaccumulation model predictions are protective for human consumer of fish and are efficient for use in risk assessment. For example, 85% of the predicted values were within a factor of 5 of measured CB153 concentrations in fish. Using sensitivity analyses, the major role played by sediment and diet behaviors on bioaccumulation process is illustrated: the parameters involved in the respiratory process (contamination from water) have little impact on model outputs, whereas the parameters related to diet and digestion processes are the most sensitive. The bioaccumulation model was applied to derive sediment concentrations compatible with safe fish consumption. The resulting PCB sediment thresholds (expressed as the sum of seven PCB indicator congeners) that are protective for the consumption of the fish species ranged from 0.7 to 3 ng/g (dw).

Estimating chemical biotransformation rates from food web concentrations

Biotransformation is widely recognized as the most important and most uncertain determinant of bioaccumulation. A step-wise method for estimating organism-specific biotransformation half-lives from field observations and using established food web modeling is developed. As a proof of concept, the method is applied to the case of nine polycyclic aromatic hydrocarbons (PAHs) in a well-studied food web in Bohai Bay, China. The estimated half-lives are in good agreement with the existing literature. The proposed biotransformation estimation method, through data mining, for sufficiently defined ecosystems, may greatly reduce the necessary animal testing involved in chemical assessments by providing useful guidance to experimentalists and regulators.

Development of a relative risk model for evaluating ecological risk of water environment in the Haihe River Basin estuary area

Ecological risk assessment for water environment is significant to water resource management of basin. Effective environmental management and systems restoration such as the Haihe River Basin require holistic understanding of the relative importance of various stressor-related impacts throughout the basin. As an effective technical tool for evaluating the ecological risk, relative risk model (RRM) was applied in regional scale successfully. In this study, the risk transfer from upstream of basin was considered and the RRM was developed through introducing the source-stressor-habitat exposure filter (SSH), the endpoint-habitat exposure filter (EH) and the stressor-endpoint effect filter (SE) to reflect the meaning of exposure and effect more explicit. Water environment which includes water quality, water quantity and aquatic ecosystems was selected as the assessment endpoints. We created a conceptual model which depicting potential and effect pathways from source to stressor to habitat to endpoint. The Haihe River Basin estuary (HRBE) was selected as the model case. The results showed that there were two low risk regions, one medium risk region and two high risk regions in the HRBE. The results also indicated that urbanization was the biggest source, the second was shipping and the third was industry, their risk scores are 5.65, 4.71 and 3.68 respectively. Furthermore, habitat destruction was the largest stressor with the risk scores (2.66), the second was oxygen consuming organic pollutants (1.75) and the third was pathogens (1.75). So these three stressors were the main influencing factors of the ecological pressure in the study area. For habitats, open waters (9.59) and intertidal mudflat were enduring the bigger pressure and should be taken considerable attention. Ecological service values damaged (30.54) and biodiversity decreased were facing the biggest risk pressure.

Emission inventory for PFOS in China: review of past methodologies and suggestions

Perfluorooctane sulfonate (PFOS) is a persistent, bioaccumulative, and toxic chemical that has the potential for long-range transport in the environment. Its use in a wide variety of consumer products and industrial processes makes a detailed characterization of its emissions sources very challenging. These varied emissions sources all contribute to PFOS' existence within nearly all environmental media. Currently, China is the only country documented to still be producing PFOS, though there is no China PFOS emission inventory available. This study reviews the inventory methodologies for PFOS in other countries to suggest a China-specific methodology framework for a PFOS emission inventory. The suggested framework combines unknowns for PFOS-containing product penetration into the Chinese market with product lifecycle assumptions, centralizing these diverse sources into municipal sewage treatment plants. Releases from industrial sources can be quantified separately using another set of emission factors. Industrial sources likely to be relevant to the Chinese environment are identified.