基于APCS-MLR模型的西藏茶巴朗湿地表层沉积物重金属分布特征及来源解析

Distribution characteristics and source analysis of heavy metals in surface sediments of Chabalang wetland in Xizang based on APCS-MLR model

湿地作为介于水体和陆地之间的第三生态系统,有着重要的生态功能。由于特殊的地理位置和自然环境条件,西藏地区形成了众多独具特色的天然高原湿地,在拉萨河流域湿地聚集现象尤为显著,茶巴朗湿地就是该流域的重要成员之一。近年来,随着城市旅游业、农牧业大力发展,湿地面积、动植物资源丰富度和湿地功能等方面出现了不同程度的退化。为了解西藏茶巴朗湿地表层沉积物的重金属分布特征与污染状况,于2021年8月共采集湿地表层沉积物样品19个,分别测定了沉积物样品中重金属含量,同时利用内梅罗污染指数和潜在生态风险指数对研究区重金属污染现状进行评价,并通过绝对主成分得分-多元线性回归模型(APCS-MLR)进行重金属来源解析。结果发现,茶巴朗湿地表层沉积物中Cu、Cr、Ni、Zn、Pb、Cd、As和Hg元素含量分别是西藏背景值的1.71、0.56、0.65、1.02、1.31、1.52、0.92、1.48倍,但远低于《土壤环境质量农用地土壤污染风险管控标准(试行)》(GB 15618—2018)中筛选值,与西藏其他高原湿地相比,沉积物重金属富集水平较低;研究区内梅罗污染指数均值为1.68,属轻度污染水平;潜在生态风险指数RI均值为134.45,属于轻微生态风险。绝对主成分得分-多元线性回归模型结果表明,茶巴朗湿地沉积物中Cu、Zn、Pb、Hg来源于交通运输和农业活动混合源,Cr、Ni来源于土壤母质源,As来源于地热源,Cd来源于地热源、交通运输和农业活动混合源,研究区湿地的沉积物重金属主要影响途径为交通运输和农业活动混合输入。本研究揭示了茶巴朗湿地沉积物中重金属元素的赋存现状、空间分布特征和生态风险等级,以及重金属的可能来源,客观了解湿地环境质量现状,为茶巴朗湿地和其他区域高原湿地后续的污染防治工作和可持续发展提供科学依据和理论支撑。

Wetlands,serving as the third ecosystem situated between water bodies and land,possess significant ecological functions.Due to its unique geographical location and natural environmental conditions,Xizang has formed numerous distinctive natural plateau wetlands.In the Lhasa River basin,the phenomenon of wetland aggregation is particularly pronounced,with the Chabalang wetland being a crucial member of this basin.In recent years,the vigorous development of urban tourism,agriculture,and animal husbandry has led to varying degrees of degradation in wetland area,biodiversity,and wetland functions.To understand the distribution characteristics and pollution status of heavy metals in the surface sediments of the Chabalang wetland in Xizang,19 samples of wetland surface sediments were collected in August 2021.The concentrations of heavy metals in these sediment samples were determined,and the Nemerow Pollution Index and Potential Ecological Risk Index were employed to evaluate heavy metal pollution in the study area.Additionally,the Absolute Principal Component Scores-Multiple Linear Regression model(APCS-MLR)was utilized for source apportionment of heavy metals.The results revealed that the concentrations of Cu,Cr,Ni,Zn,Pb,Cd,As,and Hg in the surface sediments of the Chabalang wetland were 1.71,0.56,0.65,1.02,1.31,1.52,0.92,and 1.48 times the background values in Xizang,respectively,but significantly lower than the screening values in the Soil Environmental Quality Standards for Agricultural Land(GB 15618—2018).Compared with other plateau wetlands in Xizang,the enrichment level of heavy metals in the sediment was relatively low.The average Nemerow Pollution Index in the study area was 1.68,indicating a mild pollution level,and the average Potential Ecological Risk Index(RI)was 134.45,representing a slight ecological risk.The APCS-MLR results indicated that Cu,Zn,Pb,and Hg in the sediments of the Chabalang wetland originated from a mixed source of transportation and agricultural activities,while Cr and Ni originated from the soil parent material source,As originated from the geothermal source,and Cd originated from both the geothermal source and a mixed source of transportation and agricultural activities.The primary pathway for sediment pollution in the study area was identified as a mixed source of transportation and agricultural activities.This study elucidates the current status of heavy metal elements in the sediment of the Chabalang wetland,including their occurrence,spatial distribution characteristics,ecological risk levels,and possible sources.It provides an objective understanding of the current environmental quality of the wetland,offering scientific evidence and theoretical support for pollution prevention,control efforts,and sustainable development in the Chabalang Wetland and other similar high-altitude wetlands.