穗花狐尾藻对外源15N在水-沉积物界面迁移转化的影响

通过构建室内模拟系统,利用同位素示踪技术研究过量外源NO3-在微环境中的归趋及生长期的穗花狐尾藻(Myriophyllum spicatum L.)在外源氮迁移转化中的作用.结果表明:在穗花狐尾藻组,反硝化作用、微生物固定、沉水植物吸收、异化硝酸盐还原成氨(DNRA)和转化为可溶性有机氮(DON)的去除作用分别占添加15N的47.54%、25.24%、12.76%、0.52%、1.21%;在对照组,反硝化作用、微生物固定、DNRA作用和转化为DON的去除作用分别占添加15N的32.74%、30.79%、0.54%、5.83%.在穗花狐尾藻组和对照组中约87.24%和69.90%的NO3-进行了转化.反硝化作用是去除两处理组中NO3-的主要方式,其次是微生物的固定作用,穗花狐尾藻的直接吸收也对NO3-的去除起到重要作用,DNRA作用和DON对NO3-的去除作用较小.穗花狐尾藻促进了反硝化作用,加快了NO3-在微环境中的迁移转化,直接或间接地促进了微环境对外源NO3-的去除.

Effects of Myriophyllum spicatum L. on the migration and conversion of exogenous 15N at the water-sediment interface

Simulated indoor experiments were conducted to investigate the fate of excess exogenous nitrate nitrogen and the effects of growing Myriophyllum spicatum on the migration and conversion of exogenous 15N by using the isotope labelling technology in microcosm. The results suggested that in a twelve-day experiment the percentage of exogenous nitrate nitrogen removed by denitrification, microorganism, submerged plants, dissimilatory nitrate reduction to ammonium (DNRA) and conversion to dissolvable organic nitrogen (DON) was 47.54%, 25.24%, 12.76%, 0.52% and 1.21%, respectively. in the treatment group (planted group), while in the unplanted group (control group), the percentage of exogenous nitrate nitrogen removed by denitrification, microorganism, DNRA and DON was 32.74% 30.79%, 0.54% and 5.83%, respectively. About 87.24% and 69.90% of the exogenous 15N was transformed in planted and unplanted groups, respectively during the twelve-day experiment. According to our finding, denitrification is the main pathway for nitrate nitrogen removal, followed by microorganism immobilization. M. spicatum also plays an important role in the removal of nitrate nitrogen, but the effects of DNRA and DON is relatively poor. To sum up M. spicatum promotes denitrification, accelerates the migration and conversion of nitrate nitrogen, which directly or indirectly accelerates the removal of exogenous nitrate nitrogen in the microcosm.