多环芳烃在岩溶区上覆土壤中的垂直迁移及控制因素

RULES AND CONTROLLING FACTORS OF VERTICAL MIGRATION OF POLYCYCLIC AROMATIC HYDROCARBONS IN THE OVERLYING SOIL IN KARST TERRANES

选取典型表层岩溶泉域内的土壤剖面为研究对象,分析土壤样品的主要理化指标,并采用气相色谱-质谱联用仪对土壤中的多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)进行定量分析,研究16种PAHs在土壤剖面中的垂直迁移规律及控制因素。结果表明,所研究的5个土壤剖面中,16种PAHs均被检测出,其多环芳烃含量范围为161～3 285 ng g-1,平均值为987 ng g-1。兰花沟泉域水稻田和水房泉泉域土壤剖面中,PAHs的组成均以低环PAHs为主,后沟泉泉域土壤剖面中以高环PAHs为主,柏树湾泉域马尾松林地和兰花沟泉域马尾松林地土壤剖面中,0～2 cm表层土壤中以高环PAHs为主,2 cm以下土层中以低环PAHs为主。从剖面PAHs含量和组成变化可以判断,低环PAHs较易迁移,但在土层较薄的后沟泉泉域土壤剖面中,由于翻耕等人为的扰动,高环PAHs也较易迁移。5个剖面中,PAHs在水房泉泉域土壤剖面的迁移能力最强。由于岩溶区较薄的土壤层,使得PAHs较易迁移并污染表层岩溶泉水。对土壤理化性质和PAHs总量进行多元回归分析,表明土壤总有机碳(TOC)是控制后沟泉、兰花沟泉和柏树湾泉泉域土壤中PAHs迁移的主要因子,而在水房泉泉域土壤中,无主要影响因子。

Five soil profiles were selected in typical epikarst spring catchments in Nanchuan District, Chongqing Municipality as objects of the study on rules and controlling factors of the vertical migration of 16 kinds of polycyclie aro- matic hydrocarbons （PAHs） in the soils. Soil samples were collected from every soil layers, 10 cm thick each, of the soil profiles for quantitative analysis of the PAHs with gas chromatography-mass spectrometry （GC-MS）. Results show that all the 16 PAHs were detected in all the 5 soil profiles, varying in the range of 161 -3 285 ng g-1, and averaging 987 ng g in concentration. In the soil profile at the Hougou epikarst catchment, high-ring PAHs were in dominancy, while in the soil profile at the paddy field of the Lanhuagou spring catchment and at the Shuifang spring catchment, low-ring PAHs were. However, in the soil profih, s in pine forests at the Baishuwan and Lanhuagou spring catchments, high-ring PAHs dominated the 0 - 2 cm soil layers, but low-ring PAHs did the soil layers below 2 era. From the contents of PAHs and changes in composition along the profiles, it could be inferred that low-ring PAHs migrate easily. But in soil profiles with a thin surface soil layer, artificial disturbance, like plowing, make it easy for high-ring PAHs to migrate. Among the five soil profiles, only the one in the Shuifang spring catchment witnesses the highest mobility of PAHs. As in karst areas, the surface soil layers are generally thin, PAHs migrate easily, thus polluting epikarst spring water. Multiple regression analy- sis between the total PAHs and physicochemical properties of the soils shows that total organic carbon （TOC） is the main factor controlling the migration of I＇AHs in the Hougou, Lanhuagou and Baishuwan spring catchments, while in the Shui- fang spring catchment, there is no main factor impacting migration of PAHs.