RESUMO
Rapid urbanization has driven surface runoff pollution in urban areas to a serious state. In particular, polycyclic aromatic hydrocarbons(PAHs)from road surface runoff has attracted wide attention. Two traffic roads in Shanghai (Caobao Road in an urban central area, and Jiajin Expressway in the suburbs) were identified as research objects. Runoff samples from these two traffic roads were collected for 7 rainfall events between 2007 and 2018. Then, the concentration characteristics and composition ratio of PAHs were analyzed. The differences in pollution sources of runoff PAHs from two types of traffic roads were identified based on characteristic ratio method and positive matrix factorization(PMF). The results showed that the geometric mean value (5539.2 ng·L-1) of 16 PAHs of runoff from Jiajin Expressway in the suburbs was 10 times greater than that from Caobao Road (548.1 ng·L-1), which was related to a higher truck traffic and a lower cleaning frequency on Jiajin Expressway. The benzo(a)pyrene(BaP)concentration on both roads exceeded the national emission standard, and the amount in the Jiajin Expressway was up to 21 times higher than the standard. There was no significant difference in the composition of PAHs of runoff between Caobao Road and Jiading Expressway, and 4-6 ring were dominant and responsible for 80% of total PAHs loads in both sites. Based on the analysis of the characteristic ratio method, the PAHs of runoff from Caobao Road mostly came from coal-fired sources and traffic sources, while that from Jiajin Expressway were mostly from fossil fuels, coal, and other traffic sources. Quantitative source analysis through PMF method showed that the primary sources of PAHs were gas and coal, accounting for 48.6%, followed by traffic emission sources (29.8%), and oil sources (21.7%). The contribution ratios of PAHs sources of runoff from Jiajin Expressway, sorted in descending order, are:traffic emission sources (38.5%), coal-fired sources (34.6%), oil sources (14.6%), and coking sources (12.6%). PAHs sources and contribution rates between urban and suburban roads are completely different. Gas and coal were the main sources of PAHs of runoff from Caobao Road, which was related to the high population density and relatively large gas consumption in the Xuhui District. Traffic emission was the main source of PAHs from surface runoff on Jiajin Expressway, which was related to the massive flow of coaches and trucks, and their higher PAHs emission compared to small cars. In addition, there are still coking sources of PAHs of runoff from Jiajin Expressway, which can be related to the massive industrial coal consumption in the Qingpu District.
