低温期浅水湖泊氮的分布及无机氮扩散通量:以白洋淀为例

本文以我国华北地区最大的浅水湖泊白洋淀为研究对象，探究其低温期沉积物-水界面无机氮的分布特征，分析沉积物孔隙水中无机氮扩散通量对上覆水水质的影响.结果表明，低温期白洋淀表层水总氮（TN）平均浓度范围为4.83~8.23 mg·L^-1，氨氮（NH₄⁺-N）平均浓度维持在0.21~0.34 mg·L^-1之间，硝氮（NO₃^--N）平均浓度在0.01~2.75 mg·L^-1之间.TN污染较严重，超过地表水Ⅴ类水质标准.表层沉积物TN平均含量在681~4365 mg·kg^-1之间，其中有机氮（TON）为氮素的主要存在形式，占总氮比例61.6%~93.1%.NH₄⁺-N为无机氮（TIN）的主要存在形式，平均含量范围为28.9~116.3 mg·kg^-1，NO₃^--N含量整体较低，平均值范围为5.2~23.7mg·kg^-1.低温期白洋淀0~30 cm沉积物孔隙水中NH₄⁺-N浓度是上覆水中的3~16倍，呈现逐渐累积趋势.沉积物-水界面NH₄⁺-N、NO₃^--N和NO₂^--N扩散通量范围分别为-0.55~4.09、-1.44~3.67和-0.88~0.04 mg·（m²·d）^-1，冬季低温期仍具有潜在释放风险.低温期沉积物中积累大量的NH₄⁺-N，可能会在温度升高后影响白洋淀上覆水体水质.因此研究低温期白洋淀沉积物-水界面氮的分布特征和沉积物中无机氮的内源释放风险对于改善白洋淀水质和认识浅水湖泊内源氮污染具有重要意义.

Nitrogen Distribution and Inorganic Nitrogen Diffusion Flux in a Shallow Lake During the Low Temperature Period: A Case Study of the Baiyangdian Lake

The distribution of inorganic nitrogen across the sediment-water interface in Baiyangdian Lake, the largest shallow lake in North China, was examined during the low temperature period. Furthermore, the influence of inorganic nitrogen diffusion flux in sediment porewater on the overlying water quality was analyzed. The results showed that the mean TN concentration in the surface water ranged from 4.83 to 8.23 mg·L^-1, the mean NH₄⁺-N concentration ranged from 0.21 to 0.34 mg·L^-1, and the mean NO₃^--N concentration ranged from 0.01 to 2.75 mg·L^-1. TN exceeds the Class V water quality standard for surface water, indicating serious pollution. The mean TN content of the sediments ranged from 681 to 4365 mg·kg^-1, of which TON was the main form of TN, accounting for 61.6%-93.1%. NH₄⁺-N was the main form of TIN, with a mean content ranging from 28.9 to 116.3 mg·kg^-1, and a mean NO₃^--N content of between 5.2 and 23.7 mg·kg^-1, which is relatively low. The NH₄⁺-N concentration in the porewater was 3 to 16 times that of the overlying water, showing a gradual accumulation trend. The diffusion flux ranges of NH₄⁺-N, NO₃^--N, and NO₂^--N across the sediment-water interface were -0.55-4.09, -1.44-3.67, and -0.88-0.04 mg·(m²·d)^-1, respectively. There was still a potential release risk during the low temperature period. A large amount of NH₄⁺-N accumulated in the sediments during the low-temperature period, which may affect the quality of the overlying water after the temperature rises. Therefore, studying the distribution of nitrogen across the sediment-water interface, and the risk of internal release of inorganic nitrogen during the low temperature period, is of great significance for improving water quality in Baiyangdian Lake and understanding the internal nitrogen pollution of shallow lakes.