太湖竺山湾污染底泥环保疏浚深度的推算

Calculation of environmental dredging depth of contaminated sediments in Zhushan Bay of Taihu Lake

根据颜色、气味、粒径、黏稠度等理化指标,将太湖竺山湾柱状底泥样品由上至下依次分为氧化层(A)、污染层(B)、污染过渡上层(C1)、污染过渡下层(C2)和健康层(D).通过对底泥中氨氮、总磷、总氮和烧失量垂直分布规律的分析,结合柱状底泥各分层氮、磷吸附/解吸实验,推算出竺山湾污染底泥环保疏浚层及其深度.结果表明,底泥中氨氮、总磷、总氮和烧失量含量随深度的增加呈下降趋势.A层和B层中污染物含量明显高于其他层;无机磷吸附/解吸平衡浓度随深度的增加而下降,在C1层与C2层间出现拐点;而氨氮的吸附/解吸平衡浓度变化趋势较复杂.结合上覆水中无机磷与氨氮浓度,推算出竺山湾底泥环保疏浚层次为C1层,疏浚平均深度为0.40～0.70m.

According to physical and chemical indexes of sediment,such as color,odor,particle size and viscosity,column sediments of Zhushan Bay were divided into oxide layer（A）,polluted layer（B）,upper polluted transition layer（C1）,lower polluted transition layer（C2）and healthy mud layer（D） from top to bottom.To calculate the environmental dredging layer and depth of Zhushan Bay,vertical distributions of ammonia nitrogen（NH4＋-N）,total phosphorus（TP）,total nitrogen（TN） and loss of ignition（LOI） were analyzed.Nitrogen and phosphorus adsorption/desorption experiments about every layer were also conducted.Concentrations of NH4＋-N,TP,TN and LOI decreased with depths,and concentrations of contaminants in layer A and layer B were significantly higher than those in other layers.Adsorption/desorption equilibrium concentrations of inorganic phosphorus（IP） in sediment decreased with depths,and there was an inflection point between C1 layer and C2 layer.Changes of adsorption/desorption equilibrium concentrations of NH4＋-N with depths were complex.Combined with concentrations of IP and NH4＋-N in overlying water,environmental dredging（env-dredging） layer of Zhushan Bay was layer C1 and environmental dredging depth range from 0.4 to 0.7m.