Polycyclic aromatic hydrocarbons are a kind of important environment pollutants, which are produced from such human activities as industrial technology process, anoxycausis, waste incineration and landfill, food preparation and traffic emmision and the like, and have widely existed in various environment mediums, such as a water body, and so on. The polycyclic aromatic hydrocarbon pollutants have the characters of carcinogenesis, teratogenesis, mutagenesis and non-biodegradability, which pose a threat to ecological system and human health, and therefore, more and more attentions are paid on pollution control and risk control of the polycyclic aromatic hydrocarbon pollutants.
Existing researches have shown that main rivers in China are contaminated by the polycyclic aromatic hydrocarbons at different levels. However, the water environment quality standard system in China does not cover the polycyclic aromatic hydrocarbon pollutants, and therefore, the basis for evaluating the pollution level of the polycyclic aromatic hydrocarbon in the water body is lacked. Internationally, the environment risk evaluation has become a research hotspot in the current environment field. In recent years, Chinese scholars have also tried to research on the water environment issue through environment risk theory and method, and provided a new thought for studying the ecological risks of polycyclic aromatic hydrocarbons in the water body.
At present, a quotient method is the most widely used in determining the ecological risks, i.e., the size of ecological risk is represented by means of a ratio of the environmental concentrations of pollutants to a reference value of toxicity. However, the calculation result of the quotient method belongs to a determined value, and is a rough estimate of risks. In fact, the concentration and space distribution of the polycyclic aromatic hydrocarbons in the water body have randomness and indeterminacy, and the ecological hazard effects thereof are also indeterminate due to the biological species and individual differences. Therefore, a scientific processing method will be the evaluation and analyzation of the ecological risks of the polycyclic aromatic hydrocarbons in the water body from the viewpoint of probability.
Moreover, since the basic toxicity data lacks limitation, the categories of the polycyclic aromatic hydrocarbons, the risks of which can be evaluated by using the quotient method, are limited, mainly focused on several minority polycyclic aromatic hydrocarbons like phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, benzo[a]pyrene or the like, and researches on the ecological risks of other types of polycyclic aromatic hydrocarbons are relatively lacked. Meanwhile, due to similar structures and properties, different polycyclic aromatic hydrocarbon pollutants may produce cumulative risks. Therefore, the issue of cumulative risks of the polycyclic aromatic hydrocarbon pollutants shall also be considered while determining the ecological risks of polycyclic aromatic hydrocarbons in the water body.
A patent application 200910232672.4 (A Method for Determining Ecological Risks of Pesticides in Water Body) integrates the existing risk quotient method and the probability risk evaluation method, and uses relatively fewer toxicity data to achieve quantification of the total level of the ecological risks of pesticides in the water body. However, the final risk quotient values obtained through this method are still point estimated values, which do not solve the indeterminacy problem in the risk analysis procedure. Moreover, for the polycyclic aromatic hydrocarbon substances lacking toxicity data, the ecological risk analysis thereof cannot be performed in accordance with this method.
Generally speaking, the polycyclic aromatic hydrocarbon pollutants are research hotspots for scholars at home and abroad, but the scholars mainly concentrated on such aspects as migration and transformation and environmental fate thereof. In particular, there are fewer researches on risk identification of the water ecological system, and problems such as the indeterminacy during ecological risk analysis, determination for ecological risks of polycyclic aromatic hydrocarbon pollutants lacking toxicity data as well as united risks of different pollutants have not been solved yet. Presently, no mature literatures for solving the above problem of determining the ecological risks of polycyclic aromatic hydrocarbon in the water body are retrieved.