不同下垫面类型对地表径流中多环芳烃污染特征的影响分析

Pollution characteristics of PAHs in urban runoffs on different types of underlying surfaces

为了解下垫面对径流中多环芳烃(PAHs)污染特征的影响,对4次降雨事件中不同下垫面地表径流中的PAHs污染特征进行了分析.研究发现,屋面(A点)与交通路面(C点)的PAHs污染负荷远远大于另两种下垫面,降雨事件平均浓度分别达到26.66μg·L-1和27.87μg·L-1.各场降雨事件都存在随着降雨历时污染物浓度逐渐降低的过程,其中交通路面变化最为剧烈,PAHs浓度由初始的33.50μg·L-1经90 min后下降至16.36μg·L-1,而屋面则在径流结束前伴有浓度回升的现象.径流中溶解态PAHs含量远低于颗粒态含量,以2—3环略占优势,达31%—42%;而在颗粒态PAHs中5—6环则相对更多.广场路面(B点)和交通路面(C点)由于汇流面积较大,具有较明显的初期冲刷效应;屋面(A点)的冲刷效应相对较弱;草地(D点)则未表现出初期冲刷效应.研究结果表明下垫面对径流中PAHs的含量和消除均有一定影响,但与PAHs组分的相对比例无明显相关.

To understand the role of underlying surface in affecting the pollution characteristics of polycyclic aromatic hydrocarbons （ PAHs） in urban runoff, we analyzed the PAHs contents in runoff samples from different underlying surfaces in 4 rainfall events. In the study, the PAHs contents in runoff from roof （ site A） and highway （ site C） were much higher than other underlying surfaces, and their concentrations were up to 26. 66 and 27. 87 μg·L^-1, respectively. PAH concentrations decreased along with rainfall duration in all rainfall events. Among them, the contents of PAHs in highway runoff changed most dramatically, which declined from 33.50μg·L^-1 down to 16.36μg·L^-1 within 90 min. However, PAHs in runoff showed a unique concentration elevation near the end of the rainfall. The PAHs distribution analysis showed there were more particulate PAHs than dissolved PAHs in runoff. Furthermore, 2—3 ring PAHs （ 31%—42%） slightly edged other constituents in dissolved PAHs, while 5—6 ring PAHs were major components of particulate PAHs. With larger catchment areas, square （ site B） and highway （ site C） , had more obvious first initial effects. Roof （ site A） showed a weak first initial effect, and grassland （ site D） had no such effect. Our results suggested that the underlying surface had impacts on the contents and elimination of PAHs in runoff, but had little relation with the compositional distribution of PAHs.