Determination, Distribution And Source Apportionment Of PAHs In Soils And Sediments In Shanghai, China

Polycyclic aromatic hydrocarbons (PAHs) containing two or more fused benzene rings, were one of the most important classes of environmental pollutants. Due to the persistent, toxic, mutagenic and carcinogenic characteristics of PAHs, some of them have been on the United Nation Environmental Program (UNEP) list of persistent toxic substances (PTS) and on the US EPA list of priority pollutants. PAHs were generated mainly from the incomplete combustion of organic matters in the high temperature, and existed widely in the environment, such sediments, soils and waters. Nowadays, international environmental protection organization, governments and people have focused on environmental pollution of PAHs. It is one of hotspots and difficulties in the environmental science research to understand the pollution level of PAHs in the environment humans live in, and to know the distribution and characteristic of PAHs in all kinds of environmental matrix, and to master sources and transportation of PAHs in the environmental matrix. This work focused on the development of pre-treatment and chromatography analysis method for trace 19 PAHs, including US EPA 16 PAHs, in the environmental matrix, and the determination of PAHs concentrations in surface sediments and soils of Shanghai, and the analysis on the pollution level and spatial distribution of PAHs in the sediments and soils, and the qualitative and quantitative source apportionment of PAHs, and the discussion on transportation of PAHs in the environment matrix at a certain region of Shanghai. The results of this study will add new data to the global database, and provide valuable information for regulatory actions to improve the environmental quality of the Yangtze River Delta area.At the aspect of determination of trace PAHs in the environmental matrix, this work was performed to develop and optimize the HPLC separation of US EPA 16 PAHs at a normal analysis column of C18-ODS. On the base of qualification by retention time, ultraviolet spectra obtained from PhotoDiode Array detector (PDA) were analyzed to improve qualification of 19 PAHs. Furthermore, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[e]pyrene and perylene in sediment samples were identified with the difference of ultraviolet spectra of the isomers. The quantum method for trace 19 PAHs in environmental sediments was developed. In order to intensify ultraviolet response of target components and weaken those of interferents, quantitative wavelengths of 19 PAHs were optimized. The limits of detection were improved further and were less than 10 ng/g-dw except for F1, BeP and Pery. And spike recoveries from environmental samples were 87～113%. As results of determination of sediment samples and soils samples from Shanghai were shown, 18 PAHs were detected except for AcNy, and a good repeatability of data can be obtained due to relative standard deviation (RSD) <20%. Therefore, the quantum method in this paper was sensitive and accurate and met determination requirements of trace PAHs in environmental samples.At the aspect of the monitoring for environmental samples in Shanghai, research work were performed to surface sediments and surface soils, respectively.The total PAHs concentrations of surface sediments in Shanghai were from 107 ng/g-dw to 7,177 ng/g-dw, which exhibited an obvious difference in the PAHs pollution among samples. The contamination level of sedimentary PAHs in Yangtze Estuary can be categorized as low on the global scale, and that in Huangpu River can be as moderate. Sedimentary PAH concentrations of the Huangpu River were higher than those of the Yangtze Estuary. The concentration of the Suzhou River was close to the average concentration of the Huangpu River. PAHs source analysis suggested that, in the Yangtze Estuary, PAHs at locations far away from cities were mainly from petrogenic sources. At other locations, both petrogenic and pyrogenic inputs were significant. In the Huangpu and Suzhou Rivers, pyrogenic input outweighed other sources. The pyrogenic PAHs in the upper reaches of the Huangpu River were mainly from the incomplete combustion of grass, wood and coal, and those in the middle and lower reaches were from vehicle and vessel exhaust. Cluster analysis and principal component analysis (PCA) with multivariate linear regression (MLR) were applied to apportion sources of polycyclic aromatic hydrocarbons in surface sediments of the Huangpu River in Shanghai, China, based on the measured PAH concentrations of 32 samples collected at 8 sites in four seasons, 2006. The results indicated biogenic conversion, petrogenic and pyrogenic were three important sources of PAHs and their contributions were 19%, 24% and 57%, respectively. Further analysis on the pyrogenic PAHs of the Huangpu River sediments discovered two major sources of vehicular exhaust and coal combustion, the contributions of which were quantified as 30% and 27%, respectively. Rainfall and monsoon played important roles for the distinct seasonal variation of PAHs pollution so that the contamination level of PAHs in spring was significantly higher than that in the other seasons.The total PAHs concentrations of surface soils in Shanghai were from 29-37,000 ng/g-dw, and average concentrations were 1984 ng/g-dw, and middle concentrations were 417 ng/g-dw. And a significant difference in the PAHs pollution was observed at the different regions. The contamination levels of Shanghai soils included all of levels on the global scale. -65% of samples belongs to low pollution, -20% belongs to moderate pollution, -10% belongs to free-pollution, -5% belongs to high pollution. There were three regions with the severer PAHs pollution in Shanghai. They locates at Shanghai central region (Huangpu district, Zhabei district, Changning district, Jing'an district, Luwan district, Hongkou district, Yangpu district, Xuhui district, Putuo district, part of Pudong district and Baoshan district), Songjiang & Minhang region and Jinshan region. The distribution of PAHs in soils was related closely with human activities (anthropogenic factor). Soils with different usages were contaminated by PAHs in varying degrees, namely, contamination level of soils in urban area was higher than that in agriculture area. There were different contamination conditions for different PAHs components in soils. Soils in urban area were severer contaminated by the height-weight-molecule (HWM) PAHs than soils in agriculture area. However, there were the similar contamination level among different usages soils for the light-weight-molecule (LMW) PAHs, such as naphthalene and methylnaphthalene. Source apportionment results exhibited that pyrogenic and petrogenic source were two major sources of PAHs, the contributions of which were 92.1% and 7.9%, respectively.In the end, transportation of PAHs in the environmental matrix was preliminarily investigated and discussed according to PAHs data of soils and sediments from a certain region in Shanghai. The result indicated that there are two or more pathways on PAHs transportation in the environmental matrix.