广东吴川市近岸海域表层沉积物重金属分布特征与污染评价

为了解广东吴川市近岸海域表层沉积物中重金属的污染状况，2020年10月底在吴川市近岸海域采集了41个站点的表层沉积物，系统地进行了典型重金属检测与沉积物粒度分析，并运用单因子指数法、富集因子评价法和潜在生态风险指数法对研究区内重金属的污染程度进行评价，分析了沉积物粒径大小对重金属含量分布的影响，并讨论了重金属的可能来源。研究结果表明：重金属含量分布由西向东总体上呈高-低-高的趋势，高值区主要分布在西部近岸、东北部和东南部，低值区主要分布在北部和西南部，平均含量依次为Zn>Cr>Pb>Cu>As>Cd，均符合国家一类沉积物质量标准。通过计算得出，吴川海域表层沉积物中6种重金属元素的污染程度排序为Cu≈Cr＞Pb＞Cd＞Zn＞As，单因子污染指数均<1；重金属富集程度主要集中在强富集，平均富集系数排序为Cu＞Pb＞Zn＞Cr＞Cd＞As；吴川海域的近岸海洋生态环境受到一定污染，Eir的平均值排序为：Cd＞Cu＞Pb＞As＞Cr＞Zn，仅有29.2%的站点属于轻微风险，其中对综合潜在生态风险指数影响最大的重金属元素是Cd，综合分析可得，重金属的毒理作用占主导因素，推断养殖场废水、工业废水是造成此风险指数较高的主要原因。研究区内表层沉积物中6种重金属的分布均遵循“元素粒度控制规律”，即重金属含量与沉积物平均粒径（Mz）呈显著正相关。此外，重金属之间的相关性分析结果表明，Cu、Pb、Zn、Cr、As主要来源于陆域岩石自然风化剥蚀，Cd受人类活动影响导致变异系数偏高。

Assessment on heavy metal pollution in surface sediments off Wuchuan,Guangdong Province

To understand the pollution of heavy metals in the surface sediment in the coastal waters of Wuchuan City, Guangdong Province, 41 samples of surface sediment were collected in the end of October 2020 in nearshore waters, the content of typical heavy metals were detected, sediment particle size was analyzed, and the sources of heavy metals were discussed. The distribution of heavy metals was characterized, the pollution level of enrichment factors was evaluated, and the relationship between sediment particle size and heavy-metal concentration was explored based on correlation analysis. Results show that heavy metal content showed a high-low-high trend in west-east; high-value areas were mainly distributed in the western nearshore, northeast and southeast, low-value areas were mainly distributed in the north and southwest. The average content (in mg/kg) was in the descending order of Zn (72.62±29.94)>Cr(52.36±20.22)>Pb(32.12)>Cu(22.81±9.72)>As(8.35±2.79)>Cd(0.25±0.12), which met the national Class I of sediment quality standards. The pollution degree of the 6 heavy metal elements in the surface sediment in Wuchuan coastal area was in a descending order of Cu≈Cr>Pb>Cd>Zn>As, and the single factor pollution index was below 1. Heavy metals were mainly concentrated in strong enrichment area and the average enrichment coefficient was in a descending order of Cu>Pb>Zn>Cr>Cd>As; Cu and Pb were strongly enriched; Zn, Cr, and Cd were weakly enriched; and As was depleted. The coastal ecological environment in was polluted to some extents. The average ranking of enrichment factor was: Cd>Cu>Pb>As>Cr>Zn. Only 29.2% of the site was in slight risk, of which Cd was the biggest contributor to the overall potential ecological risk and was the dominant factor in toxicology. It is inferred that wastewater discharged from farms and factories are accountable for the high risk. In addition, heavy metal content showed a significant positive correlation with the sediment average grain size following the law of element particle size dependency. Meanwhile, correlation among heavy metals show that Cu, Pb, Zn, Cr and As were mainly derived from natural rock erosion and Cd was from human activities.