Abstract:

This study explored the distribution characteristics, pollution status and the source of polycyclic aromatic hydrocarbons (PAHs) in farmland soils in sewage irrigation area to reveal and better understand soil pollution problems caused by sewage irrigation. A total of 110 soil samples were collected from farmlands around the sewage irrigation area in Taiyuan city. The 16 priority- controlled PAHs recommended by USEPA were analyzed by gas chromatography-mass spectrometery (GC-MS) to distinguish their compositions and contents. Principal Component Analysis and Multiple Linear Regression (PCA/MLR) were employed to identify the PAHs source. The mean Effect Range-Median Quotient method (Q_MERM) and the toxicity equivalent quantity method (Q_TE) were used to assess the ecological risks. The results showed that the average PAHs content was 3197.57 μg·kg^-1 in the sewage irrigation area, dominated by 4-6 ring PAHs. In the Xiaodian area, the pollution sources of PAHs included fossil fuel combustion and coking sources (66.9%), as well as the coke source (33.1%). In the Jinyuan area, the fossil fuel combustion accounted for 53.2% of pollution sources, while the other half were mainly from coal and coking combustion (46.8%). In the Qingxu area, the PAHs pollution was mainly caused by fossil fuel combustion (88%). The secondary cause was the co-combustion of coal, wood and coke (12%). Results of the risk assessment showed that the agricultural soil was low or moderate in toxicity. The Xiaodian area showed a higher PAHs value based on the Q_TE results, followed by Jinyuan and Qingxu areas. Moreover, the 7 carcinogenic PAHs were the main source compositions which accounted for more than 90% of PAHs contents. Benzo-a-Pyrene (BaP) was the most toxic monocase as it contributed to 48%-50% of Q_TE concentrations and thus should be given more attention.

Key words: polycyclic aromatic hydrocarbons, farmland soil, source, pollution characteristic, ecological risk

摘要：

通过对污灌区农田土壤多环芳烃（Polycyclic Aromatic Hydrocarbons,PAHs）的分布特征、污染程度及来源进行解析,深入了解污水灌溉引发的土壤污染问题,实现污水灌溉农田土壤的污染预警和科学合理利用。在太原污灌农田共采集110个土壤样品,使用气相色谱-质谱仪（Gas Chromatography-Mass Spectrometery,GC-MS）分析美国环境保护署（U.S. Environmental Protection Agency,USEPA）优控的16种PAHs组成与质量分数,运用主成分分析/多元线性回归法（Principal Component Analysis and Multiple Linear Regression,PCA/MLR）定量分析农田土壤中PAHs的来源。结果表明,污灌区农田土壤中16种PAHs质量分数平均值为3197.57 μg∙kg^-1（质量分数范围为214.50—13511.50 µg∙kg^-1）,以4—6环PAHs为主。PAHs来源分析表明,小店区农田土壤中PAHs主要来源及其贡献率分别为化石燃料和炼焦66.9%、焦炭源33.1%,晋源区分别为化石燃料53.2%、煤燃烧和炼焦的混合源46.8%,清徐县分别为化石燃料88%、煤木材燃烧和炼焦的混合源12%。平均效应区间中值商法（Mean Effect Range Median-Quotient,Q_MERM）生态风险评价结果表明,研究区农田土壤中PAHs为低毒性或中低毒性。毒性当量法（Toxic Equivalent Quantity,Q_TE）进一步分析指出,污灌区农田土壤PAHs的Q_TE值排序为小店区>晋源区>清徐县,其中7种致癌多环芳烃的Q_TE值占多环芳烃总量的95%以上,是PAHs毒性风险的主要来源;苯并a芘（Benzo-a-Pyrene,BaP）作为毒性最强的单体之一,其Q_TE的贡献值为44%—48%,应重点关注。

关键词: 多环芳烃, 农田土壤, 源解析, 污染特征, 生态风险