Pollution Characteristics And Influencing Factors Of Polycyclic Aromatic Hydrocarbons In Urban Soil Rainfall Runoff

Polycyclic aromatic hydrocarbons (PAHs), as one of the most common POPs, can be migrated to a long distance due to its own semi-volatile, which are widely existed in various environmental media. Thus have caused serious pollution. In a high degree of industrialization and urbanization area, the concentration of PAHs in the environment are usually very high. With the continuous consumption of energy and vulgar drainage methods, PAHs showed a rising trend year by year. Therefore, PAHs environmental problems in urban areas has focused much attention in the scientific research. Moreover, Non-point pullution does more harm than point source pollution.This paper studied the concentrations of PAHs in the rainfall runoff formed in soils as well as the dynamic process, and then analysed the influencing factors of PAHs in the runoff. For all kinds of sample sites, PAHs in runoff are evaluated both for the qualitative and quantitative analysis.Using benzopyrene toxicity equivalent concentration, HQ value and risk value method to do the ecological risk assessment of PAHs. The conclusion is as follows:(1):For the average values of 16 ΣPAHs in the runoff, according to the concentration, industrial point is the highest(2632.22ng-L-1), and then the residential areas (1405.26ng·L-1), campus sites has the lowest value(1087.63 ng·L-1). This probably has relationship with the surrounding environment. For the three sites, the ratio of 16 AHs in dissolved phase and particle phase are respectively (9.15%, 90.85%), (6.17%,93.83%), (6.91%,93.09%). PAHs in all the samples were dominated by 4 ring. The concentrations of PAHs can be seen in the box and the line, which showed the trend of EMC, industrial point pollutant varies the largest, then the residential area, campus is the last. Pollutants concentration in the process of rainfall runoff for the 2015-08-22 rainfall event varies fiercely than that of 2015-06-06.(2):For all the 16 PAH and Σ PAHs, the concentration reduced gradually. Both the dissolved PAHs in phase and particle phase in the process of dynamic change showed a consistent trend, but the mass concentration of PAHs performed opposite. The dissolved PAHs minimum phase epipodium components, and lowest concentration of particle phase 2 ring PAHs. For the 08-22 rainfall event, the maximum rainfall runoff rate appeared in the middle of the runoff, so runoff concentration of PAHs in the highest peak also moved to the middle of runoff.(3):Both TOC and TSS showed a significant correlation with PAHs. But the correlation between PAHs and runoff is not obvious. This may be associated with the corrosion of soil corrosion index. The bigger soil corrosion index, the greater influence for PAHs. The PAHs loss in soil were closely related to the PAHs concentration in runoff. The occurrence characteristics of soil itself also had an effect on the PAHs. Rainfall can lead to the loss of soil PAHs, which represented the decline of PAHs concentration. But atmospheric precipitation meant input to the soil PAHs, which made soil PAHs accumulation stablely. By monitoring campus soil, we could draw the conclusion that the atmospheric precipitation had a greater effect on the PAHs in soils than the runoff.(4):Using ratio characteristics of LMW/HMW, Fla/(Pyr+Fla), Ant/(Ant+ Phe), BaA/(Chr+BaA) to parse the sources of PAHs in the runoff. It turned out to be pyrolytic source in generally. Then the principal component analysis do the parse job. The campus and industrial point could be extracted out three principal components, and the residential sites were extracted out two. Linear regression could calculate the contribution of each principal component. For the Campus sites, coal/transportation fuel explaied the contribution rate of 69.2%. The residential site turned out to be mixed sources of pollution, oil/coal and transport fuel explained the contribution rate of 59.4% and 40.6%, respectively. For the industrial sites, main pollution sources were transportation fuel and coal source, which explained the contribution rate of 49.3% and 38.7% respectively.(5):The TEQ value in industrial soil was the highest, and the campus ranked the last. The TEQ values of three sample for the 08-22 rainfall events were greater than 06-26 rainfall event. For the 06-26 times rainfall event, the risk level of Σ16PAHs in each sample was medium; For the 08-22 rainfall event, the risk level of Σ16PAHs in the campus and residential sites were medium, while industrial point was high.