Pollution Characteristics And Risk Assessment Of Polycyclic Aromatic Hydrocarbons In The Aquatic Environment Of Potable Water Sources From Shilong To Zhongtang, Dongguan

As a category in Persistent Organic Pollutants(POPs), Polycyclic Aromatic Hydrocarbons(PAHs) are commonly studied for the fact that they are widely distributed in the environment. They may cause potential hazard to aquatic organisms and human beings when they converge into water via atmospheric deposition, surface runoff and washing. The pollution condition and risk assessment of drinking water sources has become a hot point in environmental science owing to its paramount function in providing superior water and sensitivity towards ecological change.The thesis determined the concentrations of 16 priority-controlled PAHs in 11 water samples collected from drinking water source in Dongguan city from Shilong to Zhongtang. First and foremost, pollution characteristics were analyzed to identify the source, composition and spatial distribution of PAHs in study areas. Then the ecological risk was assessed using risk quotient based on species sensitivity distribution(SSD). Finally, water environmental health risk assessment model and carcinogenesis risk factor were established to assess the health risk of PAHs to local residents through drinking water. The conclusions are listed as follows.1. The concentration in Site 1(the second bridge of South Shilong) turned out to be the highest while the lowest point appeared at Site 6(Wanjiang Bridge). The concentrations of PAHs showed a decreasing trend in south tributary while the ones showed an opposite trend in Zhongtang waterway, this attributes to the type of industry and agriculture in the ambient environment. Among detected PAHs, high ring PAHs were predominating ones. Source appointment indicated that PAHs in aquatic environment mainly originated from the burning of fossil fuel and the emission of industrial waste water. Besides, oil contamination caused by tiny leakage of industrial ingredients may also be a potential source of PAHs in study areas.2. It can be inferred from the result of effect-dose assessment that for the same PAH, it shows a severer toxicity towards invertebrates than vertebrates and the toxicity to all species selected is moderate. Anthracene, Fluoranthene and Benzo[?]Pyrene showed a relatively high influence to ecological system according to HC5 values, among which Benzo[?]Pyrene was the most poisonous pollutant. Risk quotients(RQ) of different pollutants indicated that there was not a conspicuous ecological risk in study areas and the risk can even be omitted. Anthracene contributed a lot to total hazardous index(HI).3. The calculation results of water environmental health risk assessment model indicated that(non)carcinogenic risk of PAHs were closely related to concentration and category of PAHs and the variation trend was in accord with that in concentration distribution. Total health risk is mainly contributed by carcinogenic ones. Generally speaking, the risk can't be omitted though the value was extremely low. Conclusions can be drawn from the result of incremental lifetime carcinogenic risk(ILCR) that PAHs in most of sampling sites didn't show a conspicuous detrimental influence on mankind. The risk value in the second bridge of South Shilong, however, illustrated a middle degree potential of contracting cancer, requiring relative industries to take pertinent actions to prevent the pollution condition from continuously aggravating.