喀斯特山区溪流上覆水—孔隙水—沉积物中不同形态氮的赋存特征及其迁移——以麦西河为例

Distribution and migration of different forms of nitrogen among overlying water,pore water and sediments in karst mountain stream——A case in the Maixi River

选取贵州百花湖入湖支流麦西河为对象,研究了上覆水—孔隙水—沉积物体系氮的形态差异,结果表明：麦西河上覆水中,以硝态氮（NO3--N）为主,氨态氮（NH4＋-N）次之,亚硝态氮（NO2--N）最低;孔隙水中,溶解无机氮中以NH4＋-N为主,NO3--N次之,NO2--N最低;沉积物中,总氮（TN）的含量为1 110.67~4 413.16 mg/kg;固定态铵含量为34.56~170.05 mg/kg,占TN的1.47%~6.25%;可交换态氮以NH4＋-N为主,NO3--N次之,NO2--N最低。孔隙水NH4＋-N是上覆水NH4＋-N的2.65~19.51倍,上覆水NO3--N是孔隙水NO3--N的7.14~20.43倍。沉积物TN与孔隙溶解水无机氮（DIN）、孔隙水NH4＋-N、沉积物可交换态氮和沉积物可交换性NH4＋-N呈显著正相关;在沉积物中,可交换性NO3--N与可交换性NH4＋-N及可交换态氮呈显著正相关,可交换性NH4＋-N与可交换态氮呈极显著正相关;孔隙水溶解无机氮与孔隙水NH4＋-N呈极显著正相关。麦西河不同介质中氮的迁移关系则表现为：由于浓度梯度,上覆水中的NO3--N扩散到孔隙水中,进而累积到沉积物中;沉积物的可交换性NH4＋-N,进入孔隙水,最终扩散到上覆水中。

Distribution and migration of nitrogen among overlying water,pore water and sediments are investigated in the Maixi River,the results indicate that in overlying water,the content of different forms of nitrogen assumes an order NO-3-N（tric nitrogen）NH＋4-N（ammonicacal nitrogen）NO-2-N（trite nitrogen）;while the content of dissolved inorganic nitrogen（DIN） in pore water assumes an order NH＋4-NNO-3-NNO-2-N.Content of total nitrogen and fixed ammonium（F-NH4） is 1 110.67～4 413.16mg/kg and 34.56～170.05mg/kg in sediments,accounting for 1.47%～6.25% of total nitrogen;the content of different forms of exchangeable nitrogen in sediments assumes an order NH＋4-NNO-3-NNO-2-N.Content of NH＋4-N in pore water is 2.65～19.51 times higher than that in overlying water,and content of NO-3-N in overlying water is 7.14～20.43 times higher than that in pore water.TN in sediments has significant positive correlations with the content of DIN,NH＋4-N in pore water,exchangeable nitrogen and exchangeable NH＋4-N in sediments;in sediments,exchangeable NO-3-N has significant positive correlations with the content of exchangeable NH＋4-N and exchangeable nitrogen,and exchangeable NH＋4-N has significant positive correlations with the content of exchangeable nitrogen.DIN in pore water has significant positive correlations with the content of NH＋4-N in pore water.Migration of nitrogen in the Maxi River is shown as follows： with a concentration gradient,NO-3-N in overlying water is diffuse into pore water,finally accumulated in sediments,while the exchangeable NH＋4-N in sediments is released into the pore water and further into the overlying water.