太湖流域典型河网水体氮磷负荷及迁移特征

Characteristics of nitrogen and phosphorus loading and migration in typical river networks in Taihu lake basin

对西太湖流域典型河道水体及沉积物氮磷含量进行分析,利用原柱样培养实验测定了沉积物-水界面氮磷交换通量及需氧量(SOD),并探讨他们之间的关系,结果表明:研究区域河道水体和沉积物氮磷总体含量水平较高,水体TN和TP平均含量分别为4.12mg/L和0.16mg/L,沉积物TN和TP平均含量分别为1658.76mg/kg和712.25mg/kg,NO3--N为水体无机氮的主要存在形态,NH4+-N为沉积物无机氮的主要存在形态.沉积物需氧量(SOD)区域间差异较大,大体呈现西、南部区域较高,北部区域较低的特征;沉积物-水界面各无机氮磷交换通量分别为:NH4+-N为-188.08~329.45mg/(m2?h),均值为13.05mg/(m2?h);NO3--N为-118.68~42.86mg/(m2?h),均值-28.09mg/(m2?h);NO2--N为-18.37^-4.81mg/(m2?h);均值-8.22mg/(m2?h);溶解性活性磷(SRP)为-10.94~10.58mg/(m2?h),均值1.34mg/(m2?h).NH4+-N整体表现为由沉积物向上覆水释放,且与沉积物有机质(LOI)呈极显著正相关,SRP交换通量与沉积物中TP和TDP均显著正相关,表明NH4+-N的释放与沉积物有机质的分解有关,SRP释放主要受沉积物TP和TDP影响.总体看,西部区域点位沉积物及水体氮磷污染最为严重,氮磷交换通量也较大,在区域内又表现为下游入湖口>上游的特征,表明人类活动对太湖流域典型河网氮磷水平及迁移转化特征影响较大.

The nitrogen and phosphorus content in water and sediment in Taihu Lake basin river were studied, the diffusion flux of nitrogen and phosphorus at the sediment-water interface were determined by sediment core culture experiment, and the relationships between them were also discussed. The results showed that the content of nitrogen and phosphorus in water and sediment were high, the average concentrations of total nitrogen（TN） and total phosphorus（TP） in water column were 4.12mg/L and 0.16mg/L respectively, in sediment were 1658.76mg/kg and 712.25mg/kg respectively. Nitrate（NO3--N） was the main inorganic nitrogen form in water column. However, ammonium was the main inorganic nitrogen in the sediment. Significant differences were detected in the sediment oxygen demand（SOD）, which was higher in the western and southern regions but lower in the northern region. The diffusion flux of inorganic nitrogen at the water-sediment interface were： NH4＋-N,-188.08~329.45mg/（m2·h）（average 13.05mg/（m2·h））; NO3--N,-118.68~42.86mg/（m2·h）（average-28.09mg/（m2·h））; NO2--N,-18.37^-4.81mg/（m2·h）（average-8.22mg/（m2·h）） respectively and the diffusion flux of soluble reactive phosphorus（SRP） was-10.94~10.58mg/（m2·h）（average 1.34mg/（m2·h））. In general, the flux of NH4＋-N released from sediment to overlying water, and which was positively correlated with loss on ignition（LOI） extremely significantly. The diffusion flux of SRP was positively correlated with TP and total dissolvable phosphorus（TDP） in the sediment significantly. The results indicated that the release of NH4＋-N was involved with the decomposition of the organic matters in the sediment, and the release of SRP was mainly affected by TP and TDP in the sediment. On the overall view, the pollution of nitrogen and phosphorus was most serious in the water and sediment of the sampling sites in the western region, where the diffusion flux of nitrogen and phosphorus were also relatively higher. In the western region, the diffusion flux of the sites located in downstream region were higher than those of the sites located in the upstream region, which confirmed that human activities had huge effect on the loading of nitrogen and phosphorus and their migration in the typical river networks in Taihu Lake basin.