潮滩沉积物-水界面营养盐N、P分布及交换特征

通过2月枯季和8月洪季样品的采集、室内分析和测试,对滨岸带潮滩沉积物孔隙水中营养盐含量的分布、迁移和扩散通量进行了初步研究。结果表明,NH_4~--N和N0_3~--N的平均含量8月洪季比2月枯季低,但是NO_2-N含量在8月份却达到最高,为0.04 mg/L;TP在季节分布上变化不大,8月洪季时含量较高。在空间分布上发现,排污口及大面积围垦对营养盐局部分布的影响较大。营养盐剖面分布总体趋势为NH_4~--N含量随深度增加而增加,NO_3~--N随深度增加而减少,但同时受到沉积速率和污水排放的影响。潮滩沉积物—水界面间无机氮磷的平均扩散通量分别为7.15、-0.53μg/(cm~2·d),因此沉积物是N的输入源,P的汇。同时还发现,污染物的排放能极大地改变该地区的N、P迁移量甚至迁移方向。

Distribution and Exchanging Characteristics of Porewater Nutrients in Tidal Sediments-Water Interface

Based on seasonal sampling and chemical analysis of sediments and water samples taken from Shanghai tidal flat, the nutrient concentration distribution of porewater, migration and diffusive fluxes have been studied. Results showed that the average concentration of ammonium and nitrate in August was lower than in February, while nitrite presented the highest (0.04mg/ L). Total phosphorus changed a little in seasonal distribution, and was also higher in August. The sewage discharges and the reclamation showed much impact on the spatial distribution of nitrogen and phosphorus. The total trends of distribution from nutrient profiles showed that ammonium increased in porewater profile, and nitrate decreased with depth. But sedimentary rates and sewage discharge have also important contributions to nutrient level. The average diffusive fluxes of inorganic nitrogen and total phosphorus at the sediment-water interface was 7.15 and 0.53ug/(cm2-d), presenting that phosphorus in water column is mainly from sediments, and sediment is an input for phosphorus, while nitrogen in sediments is originated from water, showing sediment is a sink of nitrogen. Moreover, the contaminant effluents can change the direction of nutrients migration.