填埋场地下水溶解性有机物时空分布特征分析:以四川红层区某生活垃圾填埋场为例

Spatiotemporal Distribution of Dissolved Organic Matter in Groundwater Near Municipal Solid Waste Landfill in Red Bed Zone:A Case Study of a Landfill in Sichuan Province

溶解性有机物(DOM)是生活垃圾填埋场地下水的主要污染物之一,但红层区填埋场地下水中DOM的特征尚不明晰.因此,为了探究红层区填埋场地下水中DOM组成及时空分布特征,本文运用三维荧光光谱技术,对我国典型红层区某生活垃圾填埋场地下水进行现场调研,结果表明:①调查区域地下水导排层监测井(DP17)、污染扩散监测井(KS2~KS6)和水产源监测井(SC8)地下水中COD_(Mn)的Psi(表示i评价指标相对于GB/T 14848—2017《地下水质量标准》Ⅲ类值的污染指数)介于1.323~5.392之间,水产源监测井(SC8)地下水中Mn^(2+)的Psi为1.140,所有监测井地下水中TN、TP、Fe、Cd、Hg和Cr的Psi介于0.001~0.587之间,其浓度均未超过GB/T 14848—2017《地下水质量标准》Ⅲ类标准限值;但相对于背景井(BJ1),各污染物的Pbi(表示i评价指标相对于背景值的污染指数)均介于0.703~142.991之间,说明调查区已受到不同污染源的影响.②填埋场渗滤液及附近地下水中DOM包括类胡敏酸(C1)和类富里酸(C2)等腐殖质类物质,以及类色氨酸(C3)蛋白质类物质.③填埋场地下水中DOM污染主要集中在填埋场附近,对周围地下水无明显影响.④地下水中DOM的腐殖化程度在丰水期[平均HIX(腐殖化指数)为3.99]和枯水期(平均HIX为10.69)具有显著性差异.⑤地下水导排层监测井中类胡敏酸(C1)和类富里酸(C2)的荧光强度分别是其他污染源的3.1~11.9倍和1.9~8.3倍,可作为填埋场地下水DOM污染的指示性指标.研究显示,调查区填埋场渗滤液及地下水有机质腐殖化程度高,对地下水的影响只局限在填埋场附近,对周围地下水未造成严重影响,填埋场趋于稳定.

Dissolved organic matter(DOM)is one of the main pollutants in the groundwater of municipal solid waste landfills(MSWLs).However,the characteristics of DOM in the groundwater of MSWLs in the red bed zone are still unclear.Therefore,based on the field investigation in a typical red bed zone of China,the source,composition and spatiotemporal distribution of DOM in the groundwater of MSWLs were studied with fluorescence excitation-emission matrix spectra.The results showed that:(1)The Psi of COD_(Mn) concentration in groundwater of groundwater drainage layer monitoring well(DP17),pollution diffusion monitoring well(KS2-KS6)and aquatic source monitoring well(SC8)was 1.323-5.392,and the Psi of Mn^(2+)concentration in aquatic source monitoring well(SC8)was 1.140.The Psi of TN,TP,Fe,Cd,Hg and Cr in all monitoring wells was 0.001-0.587,and the concentration does not exceed the classⅢlimits of the GB/T 14848-2017 Standard for Groundwater Quality.However,compared with the background well(BJ1),the Pbi of each pollutant was between 0.703 and 142.991,indicating that the survey area was affected by different pollution sources.(2)The DOM in the landfill leachate and in the nearby groundwater included humic-like substances,fulvic-like substances and tryptophan-like protein substances.(3)The groundwater contamination of DOM derived from the landfill was just limited to its vicinity.It is inferred that the groundwater diversion well could effectively reduce the impact of leachate leakage on the groundwater.(4)There was a significant difference in the degree of DOM humification in groundwater between the wet season(average HIX=3.99)and dry season(average HIX=10.69).(5)The fluorescence intensities of the humic acid and the fulvic acid in the DP17 well were 3.1-11.9 and 1.9-8.3 times higher than the monitoring wells of other pollution sources,respectively.Therefore,they can be used as indicator pollutants for the groundwater contamination of DOM derived from the MSWLs.The research shows that the organic matter of leachate and groundwater in the survey area is highly humified,the landfill tends to be stable,and the impact on the groundwater is limited to the vicinity of the landfill,without serious impact on the surrounding groundwater.