珠江水系沉积物重金属元素背景值估算及污染特征分析

Estimation of Background Values and Contamination Characteristics of Heavy Metals in Sediments of the Pearl River,China

估算水系沉积物的地球化学背景值和识别其异常对人为污染判别与环境风险评估非常重要。采集并分析了珠江58件水系沉积物样品,经分析检验,Al、Fe和Sc被选作参考元素,并对比了确定地球化学背景及识别异常值的方法。其中,基于最小截断二乘法的回归分析是定义地球化学背景的有效方法,它是一种对异常值不敏感的稳健统计方法,而基于局部富集因子的箱线图和回归诊断图更适用于识别异常值。珠江不同河段重金属污染存在差异,北江和河网区主要受As、Cd、Cu、Pb和Zn污染,东江主要受Cu、Cr和Ni污染,而西江几乎不存在重金属污染。水系沉积物的主要污染类型是点源污染,主要污染来源是采矿和电镀等相关的工业活动。

Estimating the background values and identifying anomalies are very important to discriminate anthropogenic contamination source and assess environmental risk of heavy metals.We collected and analyzed 58 sediment samples from different branches and channels of the Pearl River.China.Based on geochemical and statistical analysis.Al.Fe and Sc were proved suitable for as reference elements.Different methods of obtaining geochemical background values and outliers of heavy metals were presented and compared in this paper.A useful way to estimate the geochemical background values is provided by regression based on the least trimmed sum of squares (LTS).which is a robust statistical approach showing low sensitivity to outliers.Both boxplots of local enrichment factor and regression diagnostic plots turn out to be better for identifying outliers.Results show that contamination varied in the different segments of the Pearl River.The North River and Pearl River channels were contaminated by As.Cd.Cu.Pb and Zn and the East River by Cu.Cr and Ni while there was almost no contamination in the West River.Point source contamination remains a major cause of contamination to sediments.Main sources of heavy metals may be industrial contamination such as mining and electroplating.