Ecological Risk Assessment Of Polybrominated Diphenyl Ethers (PBDEs) In The Aquatic Environment Of Estuary

The chemical formula of PBDEs (polybrominated diphenyl ethers, PBDEs) is C12H (0-9)Br (1-10)O. According to the number of bromine atoms, they are divided into 10 different groups, with 209 kinds of homologues. PBDEs are now considered ubiquitous pollutants. It released into the environment in the phase of its production, use and waste disposal with varying degrees. Although the potential harm of PBDEs is recognized, because of its good performance, and difficulty to find substitutes, only few countries expressly prohibit or limit use of PBDEs used as flame retardants, and the amount has been great. As far as estimated that in the world, especially in developing countries. The use of PBDEs will not only use a very long time, but the amount of it will also maintain the considerable growth.The estuary is important places for land-sea interaction and the coastal zone with the most frequent human activity, population density, economic development, and have a pivotal position in the national economy of various countries. But stressed he objectives of a single economic model of resource development and utilization of resources bring on the environmental problems, causing pollutants into the sea, including a significant increase in the estuary decline in biodiversity. The problem of environmental pollution and ecological impact in the estuary are serious. Experiments show that PBDEs'homologue general has toxicity. Therefore, theEcological Risk Assessment of Polybrominated Diphenyl Ethers (PBDEs) in the Aquatic Environment of Estuary has become an extremely urgent task.Ecological risk assessment is a comprehensive branch of science that based on ecology, ecotoxicology, mathematics and computer technology disciplines. And it's generally object refers to human activities or adverse events that cause harm to the ecological environment or on biological individuals, populations and ecosystems. Ecological risk assessment is the processes to analyze the possibility of adverse effect. Based on the evaluation framework of "Guide to Ecological Risk Assessment"(USEPA) for the main body, the study divides the question of ecological risk assessment of polybrominated diphenyl ethers (PBDEs) in the aquatic environment of estuary with ecological risk assessment form, risk analysis and risk characterization of three stages. At the same time, the study use the evaluation method of the EU for new chemicals, existing chemicals and pesticides to human health and environmental risk, combined with PBDEs'related nature and the characters of aquatic environment of estuary, do research on the following areas :(1) The formation of ecological risks with PBDEsEcological risk of chemical substances is closely related to the nature of the hazard identification of chemical substances. The study collects the information of PBDEs in the production, use and release of. And analyze the requirements against the screening of EU REACH regulations, China's "new chemical substance risk assessment guidelines" and " Stockholm Convention on Persistent Organic Pollutants ". Combined with the requirements of " Stockholm Convention on Persistent Organic Pollutants " and the EU REACH regulations to identify the ecological risk. Through the analysis of estuary ecosystems, the study confirms the form of estuary and founds the conceptual model of ecological risk and to develop an analysis plan.(2) Research on exposure characterizationExposure characterization of ecological risk is an important part of the analysis phase. It is the analysis of risks and risk sources or potential receptor that exists between the contacts and the process of symbiotic relationship. These studies analyze the typical exposure way of PBDEs in the water environment, and show the qualitative and quantitative characterization methods of exposure and analysis the application of the food chain model and the fugacity model in the ecological risk assessment.(3) Research on ecological effects characterizationCharacterization of ecological effects is the analysis of pressure caused by changes in ecological receptors. And the evaluation endpoint of the corresponding can be in the biological level, population level and ecosystem level. This study discusses the application of ecotoxicology method on ecological effects characterization. The study introduces the toxicity data extrapolation methods and use the United States Environmental Protection Agency laboratory toxicity data extrapolation method to calculate the multi-ethnic no effect concentration (MS NOEC) of PBDEs in the water environment. And the PeBDE and OBDE in the water for the MS NOEC values are 0.53μg/L and 0.17μg/L; PeBDE, OBDE and DBDE in sediments of MS NOEC values are 0.31 mg / kg, 134 mg / kg and 453.6mg/kg.(4) Research on risk characterization The risk characterization of hazardous wastes or hazardous substances is to analyze the whether there are any potential adverse effects on the ecosystem or biological individual, population, integral part of community, or to express the potential adverse effect. This study mainly discusses the quotient and probability risk characterization method to provide technical support for ecological risk assessment.(5) The uncertainty analysis of ecological riskUncertainty analysis should be conduct throughout the analysis phase. With the analyze of the study, the uncertainty of ecological risk assessment of PBDEs generated by the following main aspects: vulnerability data, including detection methods as well as the experimental error, and the representativeness of samples, the process of model founded, and uncertainty of experience model.(6) Case study: take the Pearl River estuary as an exampleThe Pearl River estuary is the major concourse of land-based sources of pollutants in the northern South China Sea. Early study of this area of showed that the region has been subject to a certain degree of PBDEs pollution.This study uses the conceptual model that has been founded and collects the PBDEs exposure data in sediments and water of the Pearl River estuary, conducts the ecological risk evaluation of Pearl River estuary. Evaluation results showed that there is no ecological risk in Pearl River estuary from PBDEs for a while; compared with the sediment, water environment in the Pearl River Estuary has higher level of ecological risk, the risk comes mainly from the pressure of PeBDE, the result of ecological risk assessment of it is 0.00703; not only in the water and sediment, the risk of PBDEs mainly from PeBDE, and it mainly because of it has more observably toxicity than others; and why there is no ecological risk in Pearl River estuary from PBDEs for a while because the main fireproof product is DBDE, and the toxicity of DBDE is low. But because the DBDE can decompose significant, we should pay due attention to the potential ecological risk of PBDEs in order to protect the ecological environment.