南盘江流域(云南段)水系沉积物中重金属含量分布特征及其污染状况评价

Distribution and Pollution Evaluation of Heavy Metals in Sediments in the Nanpan River Basin (Yunnan Section)

为了查明南盘江流域(云南段)水系沉积物中重金属的含量分布特征和污染程度,系统采集了流域内水系沉积物25个,运用电感耦合等离子体质谱仪分析沉积物中重金属含量。利用地球化学方法和统计学方法,对该流域水系沉积物中重金属含量、空间分布特征与元素相关性等方面进行探讨和分析;采用富集因子、地累积指数和污染负荷指数等综合指标,评估南盘江流域水系沉积物的污染程度和厘定流域主要的重金属污染元素。结果表明,南盘江流域内普遍富集Cd,上游富集Cr和As,中游富集Pb和Sb,下游富集Sb。中游处泸江支流汇入,显著影响了南盘江干流沉积物中重金属分布。流域内有色金属硫化物矿床遍布、采冶工矿企业众多,金属硫化物的自然风化和矿业活动是该流域部分河段水系沉积物中重金属富集的主要来源。南盘江流域(云南段)存在一定程度的重金属污染,且不同河段重金属污染程度差异大,表现为中游>上游>下游。流域内主要污染贡献元素为Cd和As,Sb和Cr次之,Zn、Pb和Cu的污染程度较轻。

In order to reveal the distribution characteristics of heavy metals in the Nanpan River Basin（ Yunnan section）, twenty-five sediment samples were collected. Contents of trace metal in sediments were determined by using inductively coupled plasma mass spectrometry（ICP-MS） .Geochemical and statistic methods were applied to analyze the spatial distribution and correlation of heavy metals in sediments of the Nanpan River. Degree of contamination and major pollutant elements in the Nanpan River basin were assessed by using enrichment factor（EF）, pollution loading index（PLI） and index of geo-accumulation（ Igeo ）. Results show that the enrichment degree of heavy metal elements in sediments of the Nanpan River are followed the order of Cd〉As〉Cr〉Pb〉Sb〉Zn〉Cu. Cadmium is riched in the whole Nanpan River basin, while the upper reaches are enriched in Cr and As; the middle reaches are enriched in Pb and Sb; and the lower reaches are enriched in Sb. Lujiang tributary in the middle reaches significantly influences the distribution of elements in sedi- ments of the Nanpan River. Due to nonferrous metal sulfide deposits, mining and smelting factories are located throughout the Nanpan River Basin. Potential sources of heavy metals in sediments of the Nanpan River basin might be the weathering of sulfide and mining/smelting activities. The Nanpan River Basin（Yunnan section）is polluted by heavy metals, and its pollution degree varies from different reaches（ middle reaches〉upper reaches〉lower reaches）. Among the major contamination elements in the Nanpan River, Cd and As occupy the first place; Sb and Cr rank the second; while Pb, Zn and Cu take the third place.