In the mainstream of the Lancang River, eight cascade dams have been constructed. In order to find the effects of the cascade reservoirs on the transformation of nitrate (NO₃-N) and ammonium (NH₄-N) in pore water of sediments, a field survey was carried out both in the upper natural river reach (NRR) and cascade reservoirs reach (CRR) of the Lancang River from January 10 to 20, 2018. The results indicated that (1) in the NRR, NO₃-N concentrations in sediment pore water were higher than those in the CRR, whereas the total nitrogen (TN) and NH₄-N were significantly lower; the diffusion fluxes of NH₄-N from sediment to overlying water varied from −0.180 to 0.049 mg·(m²·d)^-1, and the diffusion fluxes of NO₃-N varied from 0.012 to 0.098 mg·(m²·d)^-1. (2) in the CRR, the NH₄-N concentrations in sediment pore water were much higher than those in the overlying water, but the NO₃-N concentrations in the overlying water were much higher; the diffusion fluxes of NH₄-N from the sediments to the overlying water varied from 0.161 to 1.561 mg·(m²·d)^-1, but the NO₃-N diffused downward from the overlying water to the sediments and the diffusion fluxes varied from −0.011 to −0.223 mg·(m²·d)^-1. It was concluded that the cascade reservoirs could increase the NH₄-N concentration and inversely decrease the NO₃-N concentration in the sediment pore water, which meant that the risk of the nitrogen release from the sediment in the cascade reservoirs was much higher than that in the natural river.

中文翻译：

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梯级水库对澜沧江沉积物孔隙水中氮转化的影响

澜沧江干流已建成8座梯级大坝。为了解梯级水库对沉积物孔隙水中硝酸盐（NO ₃ -N）和铵盐（NH ₄ -N）转化的影响，在天然河上游河段（NRR）进行了实地调查。 ) 和澜沧江梯级水库河段 (CRR) 于 2018 年 1 月 10 日至 20 日。 结果表明 (1) 在 NRR 中，沉积物孔隙水中的NO ₃ -N 浓度高于 CRR，而总氮（TN）和NH ₄ -N显着降低；NH ₄ -N从沉积物到上覆水的扩散通量从-0.180到0.049 mg·(m ² ·d)不等^-1 ,NO ₃ -N的扩散通量在0.012~0.098 mg·(m ² ·d) ^{-1 之间变化}。(2)在CRR中，沉积物孔隙水中的NH ₄ -N浓度远高于上覆水中的NH ₄ -N浓度，而上覆水中的NO ₃ -N浓度则高得多；NH ₄ -N从沉积物到上覆水的扩散通量为0.161～1.561 mg·(m ² ·d) ^-1，但NO ₃ -N从上覆水向下扩散至沉积物，扩散通量为从 -0.011 到 -0.223 mg·(m ² ·d) ^-1. 结果表明，梯级水库可以提高沉积物孔隙水中的NH ₄ -N浓度，反之降低沉积物孔隙水中的NO ₃ -N浓度，这意味着梯级水库中沉积物释放氮的风险远高于那在天然河流中。