近百年来珠江口淇澳岛滨海湿地沉积物重金属累积及生态危害评价

Heavy Metal Accumulation During Last Hundred Years and Its Assessment of Potential Ecological Risk in the Coastal Wetland of Qi'ao Island,Pearl River Estuary of China

河口地区细颗粒沉积物在输运和沉积过程中记录了人类活动的信息.对珠江口淇澳岛滨海湿地柱状沉积物进行粒度和测年分析结果表明,该地区沉积物以黏土质粉砂为主,沉积物黏土和粉砂含量及平均粒径均表现为由底向表逐渐增大的趋势,59 cm以上的沉积速率为4.15 cm.a-1,59 cm以下的沉积速率为0.97 cm.a-1.沉积物重金属测试结果表明,1966年以前各类重金属含量缓慢上升,为轻微的潜在生态危害强度;1966～1992年之间由于珠江口地区社会经济的快速发展,沉积物中重金属含量迅速增加;各类重金属污染危害程度排序为:Cd>Ni>Pb>Cu>Cr>Zn.Cd的潜在生态危害最为严重,其危害程度在1966年以前为轻微生态危害,在1966～1984年之间快速上升为中等生态危害,到1992年以后又上升为强生态危害,2001年以后又下降为中等生态危害.其余5个重金属元素的危害程度均属轻微生态危害.整个剖面的沉积物重金属潜在生态危害指数属轻微生态危害.淇澳岛重金属含量及潜在生态危害较好地反映了珠江口周边地区及流域内人类活动对滨海湿地沉积物重金属污染的影响过程和程度.

The processes of fine sediment transport and deposition can record some relative anthropogenic information in estuarine environments.Grain size analysis of the sediment core collected from coastal wetland of Qi＇ao Island in the Pearl River Estuary of China show that the sediment is mainly composed by clayey silt,and the mean grain size,contents of clay and silt increase upward gradually.Chronology analysis show that the sedimentation rate above 59 cm is about 4.15 cm.a-1,and 0.97 cm.a-1 beneath 59 cm.Heavy metal analysis indicate that the contents of the each heavy metal increased slowly with a slight intensity of potential ecological risk;however,from 1966 to 1992,the heavy metal contents increased obviously because of the quick social-economy development around the Pearl River Estuary area,and the order of polluting degree of these heavy metals in core sediment is Cd Ni Pb Cu Cr Zn.The potential ecological risk intensity of Cd increased from slight risk before 1966 to strong risk since 1992,and the potential ecological risk intensities other heavy metal are slight risk;the potential ecological risk index is weak level.The variations of core sediment heavy metal contents and its ecological risk assessments along the vertical profile reveal the interaction processes and intent of anthropogenic influences from the areas around the Pearl River Estuary and the catchments.