临洪河口现代沉积环境及重金属元素的分布特征

Depositional environment and distribution characteristics of heavy metals in Linhong estuary

对江苏北部临洪河口不同区域的表层与柱状沉积物进行了粒度分析、石英颗粒表面微细结构和沉积物的测年分析以及沉积物中的重金属含量分析,将河口划分为不同的沉积环境区,探讨了不同沉积环境中沉积物的粒度分布、石英颗粒表面微细结构、沉积速率以及重金属元素分布差异的原因。结果显示,临洪河口可以划分为低潮滩上的波浪与潮流强烈混合作用区、高潮滩上的弱潮流作用区、口门附近的潮流与河流强烈混合作用区和河道内河流与潮流弱混合作用区。重金属的含量在柱样的30～40cm深度呈现向表层递增的趋势,Hg的污染比较严重,其他元素基本无污染,整个河口区域的生态危害性严重;沉积物粒度分布不是该区域重金属分布的主要影响因素,城市污水排放量增加、氧化还原层位、沉降方式和不同沉积区的水动力环境是影响本区域重金属元素分布和累积的主要原因。

Sediment grain-size distribution, surface texture, sediment dating and heavy metal concentrations in surface and core sediments from different areas in the Linhong estuary in north Jiangsu Province were analyzed. Different deposition areas were distinguished based on these results. The reason for different grain-size distribution, surface texture, sedimentation rate and the distribution characteristics of heavy metals were discussed. The result shows that depositional environment of Linhong estuai7 can be divided up as tide and wave intensive mixed deposition area in low tidal flat, tide mild dynamics deposition area in high tidal flat, tide and fluvial intensive mixed deposition area in river outlet, tide and fluvial mild mixed deposition area just inland of the river outlet. Concentrations of heavy metals increased from depths of 30 - 40 cm to the surface. Heavy metal pollution of Hg was heavy, other heavy metals pollution were negligible, and high potential ecological risk was exist in the whole Linhong estuary. Grain size distribution was not the main reason that influenced the distribution characteristics of heavy metals in this area. The increasing wastewater discharge, redox effect near the surface sediment, depositional style and different chemical environment caused by hydrodynamics in different deposition area were the main control factors.