青年湖沉积物中氮赋存形态的季节性变化

通过对青年湖中心区和浅滩区近1 a的野外观测,分析其沉积物、间隙水和上覆水中TN、EN(可交换态氮)和Fixed-NH4+-N(固定态铵)的含量及表层沉积物Eh和温度的季节变化.结果表明:沉积物中w(TN)较高,且中心区大于浅滩区;NH4+-N是沉积物中EN的主要形式,约占w(EN)的95%,是氮自沉积物向表层水扩散的主要形态;沉积物中w(NO3--N)和w(NO2--N)较低;青年湖沉积物具有较强的吸持Fixed-NH4+-N的能力,浅滩区和中心区w(Fixed-NH4+-N)占w(TN)的比例分别为18.57%和20.84%,Fixed-NH4+-N是潜在氮源;沉积物中w(可交换态NH4+-N)和w(Fixed-NH4+-N)呈现春、夏季降低,秋、冬季升高的变化趋势,w(NO3--N)呈春、夏季升高而秋、冬季降低的变化趋势,且浅滩区变幅大于中心区;植物根系、温度的季节性变化可改变表层沉积物的还原环境,进而影响氮的硝化-反硝化作用和矿化作用.

Seasonal Variation of Nitrogen in Sediments of Lake Qingnian

Through one year of field observation in the deep and shallow water areas of Lake Qingnian,total nitrogen(TN),exchangeable nitrogen(EN) and fixed ammonium(NH4+-N) in the sediments,pore water and the overlying water were investigated.Seasonal variation of Eh and temperature were also studied.The results showed that TN in the sediments was the highest,and increased closer to the deep water area.Ammonium(NH4+-N) accounted for about 95% of EN,and was the main form of nitrogen which spread from sediments to the surface water.Meanwhile,nitrate(NO3——N) and nitrite(NO2——N) were the lowest in the sediments.As a potential nitrogen source strongly retentive in the sediments,fixed ammonium accounted for 18.57% of TN in the shallow area and 20.84% in the deep area.Statistics revealed that exchangeable ammonium and fixed ammonium declined in spring and summer,while increasing in autumn and winter.However,NO3——N had the opposite seasonal variation.Furthermore,variations in the shallow water were greater than those in the deep water.Lastly,it was found that plant roots and seasonal variation of temperature affects the reduction environment in the surface sediments and the processes of nitrification-denitrification and mineralization.