西昌邛海沉积物重金属含量时空变化与污染评价

通过对四川省西昌市邛海沉积岩芯10种金属元素全量与表层沉积物7种重金属元素全量和赋存形态的分析，研究了近百年来重金属累积和污染的时空特征及其在表层沉积物中的潜在生态风险.20世纪70年代之前，沉积岩芯中金属元素含量均较为稳定；70年代沉积物中Al、Fe、K和Cr含量呈明显的峰值，与流域降水量增加及围湖造田和毁林开荒等导致的细颗粒表土侵蚀输入有关；90年代以来，随着流域土壤侵蚀强度降低，Al、Fe、K和Cr等含量总体呈下降趋势，而As、Cd、Cu、Pb和Zn含量逐渐升高或较为稳定.富集系数结果表明，沉积岩芯中Cd、Pb和Zn受到不同程度的人为污染；其中Cd污染最重，污染开始于20世纪60年代，90年代以来保持在中等污染水平.表层沉积物中，Cd在西北部湖区含量较高，其余重金属含量空间变化趋势不明显；Cd、Pb和Zn的有效态质量分数平均分别为95%、63%和48%，其中Cd以酸可提取态为主，Pb和Zn主要赋存于可还原态和可氧化态中；其余重金属有效态质量分数平均值小于27%.重金属全量与有效态含量结果均表明，表层沉积物中Pb和Zn为轻度污染或中度污染水平，Cd平均为中度污染水平，但在西北部湖区达到了重度污染水平.基于重金属全量与有效态含量分别估算的表层沉积物中人为源Cd、Pb和Zn的含量较为接近（P>0.05），说明人为输入的重金属在沉积物中主要赋存于有效态中.综合沉积物质量基准、潜在生态风险指数评价结果及重金属赋存形态，表层沉积物中Cd具有较强的潜在生态风险，其余重金属表现为低生态风险.

Spatial-temporal Variations and Pollution Assessment of Heavy Metals in Sediments of Qionghai Lake in Xichang City

Based on the analysis of the total concentrations of 10 metals in the sediment core and total concentrations and chemical fractions of seven metals in the surface sediments of Qionghai Lake in Xichang City, Sichuan Province, the spatial-temporal characteristics of metal accumulation and pollution over the past century and the potential ecological risk of metals in surface sediments were studied. Before the 1970s, metal concentrations in the sediment core were stable. The total concentrations of Al, Fe, K, and Cr in the sediment core exhibited visible peaks in the 1970s, which were related to the enhanced input of fine-grained topsoil caused by increasing precipitation, lake reclamation, and deforestation. Since the 1990s, the total concentrations of Al, Fe, K, and Cr decreased with the reduced topsoil erosion, whereas the total concentrations of As, Cd, Cu, Pb, and Zn gradually increased or remained stable. The enrichment factor results showed that Cd, Pb, and Zn were the main contaminants, with Cd as the typical contaminant in the sediment core. The Cd contamination started in the 1960s and has remained at a moderate level since the 1990s. In the surface sediments, the total concentrations of Cd were higher in the northwest lake area, and no visible spatial concentration trends of the other metals were displayed. The bioavailable fractions of Cd, Pb, and Zn accounted for 95%, 63%, and 48% of the total metal concentrations on average. Among the bioavailable fractions, Cd was mainly in the acid-soluble fraction, and Pb and Zn were mainly in the reducible and oxidized fractions. The bioavailable fractions of the other metals were less than 27%. The results of total concentrations and bioavailable fractions of metals revealed that Pb and Zn in the surface sediments were slightly or moderately contaminated, and Cd was moderately contaminated on average. Cd contamination was at a severe level in the northwest lake area. The concentrations of anthropogenic Cd, Pb, and Zn in the surface sediments estimated from the total and bioavailable concentrations were comparable (P>0.05), indicating that anthropogenic metals primarily existed in bioavailable fractions in the sediment. Integrating the assessment results from sediment quality guidelines, potential ecological risk index, and chemical forms of metals, Cd in surface sediments may pose a high ecological risk, whereas the other metals has a low ecological risk.