华北农村水环境污染评价及源解析

Pollution assessment and source analysis of rural water environment in North China

近年来,国家相继发布多项重要文件要求整治农村人居环境、建设美丽乡村,但当前针对农村水环境问题研究相对较少,制约了农村环境治理工作开展。选取华北某镇农村河道坑塘,评价农村水环境污染水平、生态风险并进行污染溯源。结果表明,57处调查点位中有1处水体黑臭,但有多处调查点位水体溶解氧在2~3 mg·L^(-1)、透明度在25~35 cm、氨氮在8~15 mg·L^(-1),接近黑臭阈值。仅有约9%的水体全部水质指标均能满足地表水V类要求(检测指标为18项),超标指标主要为pH、CODMn、BOD、氨氮、总磷、总氮、粪大肠菌群等8项。底泥总磷、总氮标准指数分别处于中度、重度污染状态,营养盐综合指数属于重度污染状态。底泥存在不同程度的重金属富集,铜、锌、汞、镉、铬、铅、砷、镍等8项重金属的平均浓度是天津土壤背景值的0.45~2.73倍。汞的地累积指数平均值为0.64,为轻度污染;铜、锌、镉、铬、铅、砷、镍等其他7项重金属为清洁状态。汞的潜在生态风险指数约110,为较高生态危害;其他7项重金属生态风险指数均小于80,为轻微生态危害。综合Pearson相关性、主成分及PMF分析,研究区重金属最主要的污染来源是交通源和大气沉降,其次是工业源,最后是农业源。总体来看,研究区水体水质较差,沉积物有重金属轻度富集,其中汞是沉积物生态风险的主要贡献元素。

In recent years,polices had been issued by Chinese government requiring the improvement of rural living environment and the construction of beautiful rural areas.However,little research on rural water environment was conducted,which hindered the development of rural environmental governance.In this paper,rural river channels and ponds in a town in North China were selected to assess rural water environmental pollution and its ecological risks,and to trace their pollution sources.The results showed that one of 57 survey sites was evaluated as black and odorous water.DO,TS and NH4-N for other survey sites were 2~3 mg·L^(-1),25~35 cm,and 8~15 mg·L^(-1),which were close to the standard limits for black odorous water.Only 9% of survey sites meet the surface water Class V standard(18 monitoring indicators).pH,CODMn,CODCr,BOD,NH4-N,TP,TN and fecal coliform bacteria were indicators that exceeded the standard.TP standard index was in moderate level and TN standard index was in severe level.There was varying degrees of heavy metal enrichment in the sediment,with the average concentrations of eight heavy metals such as copper,zinc,mercury,cadmium,chromium,lead,arsenic,and nickel being 0.45~2.73 times of the background values of Tianjin soil.The average soil accumulation index of mercury was 0.64,indicating mild pollution,while the other seven heavy metals were in a clean state.The potential ecological risk index of mercury was about 110,indicating a high ecological hazard.The ecological risk index of the other seven heavy metals was less than 80,indicating a slight ecological hazard.Based on Pearson correlation,principal component analysis,and PMF analysis,the main sources of heavy metal pollution in the study area were transportation sources and atmospheric sedimentation,followed by industrial sources and finally agricultural sources.Overall,the water quality in the study area was poor,and there was a slight enrichment of heavy metals in the sediment,with mercury being the main contributing element to the ecological risk of the sediment.To improve the quality of rural water environment,it was necessary to strengthen the control and governance of agricultural and rural non-point source pollution.