Characterization And Ecosystem Risk Assessment Of Polycyclic Aromatic Hydrocarbons (PAHs) Of Two Rivers In The Hai River Basin, China

Polycyclic aromatic hydrocarbons (PAHs) are an environmental concern due to their carcinogenicity, mutagenicity and toxicity. PAHs'behavior, transport, fate, sources and environmental risk to ecological systems have been extensively studied. The concentration and distribution of PAHs in natural water has become a research focus in the world. In China, the Hai River Basin is the most polluted among the eight big river basins. The proverb, "Almost all rivers were dry, almost all water in rivers was polluted." is the most vivid portrayal of the water environment of the Hai River Basin. However, according to recent literatures, currently study on PAHs of the Hai River Basin mainly focused on the areas around Beijing and Tianjin and research about PAHs in other areas could only be seen in a very few reports. Based on these reasons, the Luan River which was relatively less polluted and the Zhangweinan River which was most polluted among all the rivers in the Hai River Basin were chosen as the study objects.In wet season, the distribution of PAHs was studied by determining the levels of 16 PAHs in water and sediment samples of the Luan River; a very important drinking water source for Tianjin and Tangshan in Hebei province, China. A total of 11 water samples, 11 sediment samples were collected during April 2008. The total PAHs concentrations in water varied from 9.8 to 310 ng·L^–1, and those in surficial sediments ranged from not detected (ND) to 478 ng·g–1 dry weight. The results showed that the upstream, downstream areas were less polluted and high polluted sites concentrated in the middle reaches of the river. The concentrations of PAHs in rural areas (5 sites) which could be considered as the'background'levels were lower than those near city zones (6 sites) which could be regarded as the'maximum'values. The PAHs were dominated by 3- (38.4%), 4-ring (60.7%) components in water samples and by 3- (27.4%), 4- (38.5%) and 5-ring (15.8%) compounds in sediments. High molecular weight PAHs were inclined to be absorbed into sediments. The 3-, 4-ring PAHs were the most common components in the Luan River. The molecular indices and the distribution of different rings were used to infer the sources of PAHs, and the results suggested that anthropogenic heavy fuel combustion was likely to be the main source. And petroleum PAHs had a high contribution to PAHs pollution at Baohekou and Daheiting.In dry season, the distribution and source of 16 polycyclic aromatic hydrocarbons (PAHs) in the Luan River, China, has been investigated.∑PAHs levels ranged from 37.3 to 234 ng·L^–1 in water, from 20.9 to 287 ng·g-1 in sediment and from 36.9 to 378 ng·g-1 in bank soil, respectively, showing the mean concentration of PAHs in bank soil was a little higher than that in sediment. The compositional profile of PAHs revealed that low molecular (2- to 3-ring) weight PAHs were predominant in dissolved phase, and 4-ring and higher molecular (5- to 6-ring) weight PAHs were abundant in bank soil and sediment, showing different composition profile characteristics in different medias. The spatial distribution of PAHs indicated that the most polluted sites all gathered in the middle and lower reaches of the region, which was in accordance with the distribution pattern of cities in the Luan River Basin, and the rural areas and estuary were much less polluted. There was no significant difference between the main river and it's tributaries on PAHs contamination in water, sediment and bank soil. PAHs in water from different sites showed familiar composition profiles, while PAHs in sediment and bank soil from rural areas and city zones presented different composition profiles. A method based on toxic equivalency factors (TEFs) and risk quotient (RQ) which can be used to access the ecosystem risk of∑PAHs sensitively and accurately was invented and a new ecosystem risk classification of∑PAHs was suggested. The results indicated that the PAHs in aquatic environment of the Luan River resulted in low ecosystem risk and at S9 the ecosystem risk of PAHs in water was moderate. Low and moderate molecular PAHs presented much more ecosystem risk than high molecular PAHs in the Luan River Basin and the mean ecosystem risk in water was higher than that in sediment and bank soil. As it was concluded that the PAHs in bank soil could better reflect the original source of PAHs, the PAHs data of bank soil was used for PAHs source identification. Both diagnostic ratios of selected PAHs and principal component analysis (PCA) with multiple linear regression (MLR) analysis were studied, suggesting mixed sources of fossil fuels combustion and biomass combustion deriving PAHs in the Luan River Basin.In the Zhangweinan River, the distribution and sources of 16 priority dominated polycyclic aromatic hydrocarbons (PAHs) in surface water were investigated. The total concentrations of PAHs ranged from 31.7 to 74.5ng·L^–1 in April with the average value of 56.3 ng·L^–1, from 45.3 to 99.0 ng·L^–1 in October with the average value of 62.9ng·L^–1, which is lower when compared with the PAHs concentration in other rivers in the world. The spatial distribution of PAHs showed that Sinvsi was heavily polluted site and the Estuary was slightly polluted compared to other sampling sites. The temporal distribution showed that concentrations of PAHs in October were higher than those in April. The PAHs were dominated by 2-, 3-, 4-ring components in water samples in April (25.1%, 48.7% and 19.1%) and October (29.9%, 45.5% and 22.9%). A new ecological risk assessment method was introduced in this study. The values of RQ∑PAHs(MPCs) at all sites were 0 and the values of RQ∑PAHs(NCs) ranged from 34.7 to 111.0 in April with the mean value of 58.4 and from 20.4 to 88.8 in October with the mean value of 49.8, respectively. The levels of ecological risk were generally low, and the risk in April was slightly higher than that in October. The ecological risk was the highest at Sinvsi in April and was the lowest at the estuary in October. The molecular indices and isomer pair ratios were used to infer the sources of PAHs, and the results suggested that anthropogenic heavy fuel combustion might be the main source. And at Sinvsi and Estuary, petroleum had a high contribution to PAHs pollution.Contrast of the two rivers showed that PAHs pollution characteristics such as levels, composition, distribution, ecosystem risk and sources in the two rivers were similar in some aspects. When compared with the Hai River in Tianjin, with PAHs and common pollutants considered, pollution status of the three rivers showed different characteristics and it was preliminarily concluded that different pollutants showed different distribution and transformation features and different kinds of rivers were polluted with different compositions of pollutants. KEY WORDS: polycyclic aromatic hydrocarbons (PAHs); the Luan River; the Zhangweinan...