丹江口库区典型小流域水体氮素分布特征研究

丹江口水库水质总体良好,但总氮浓度超标问题突出。为明确不同类型小流域氮素的分布和输出特征,优化制定库区控氮措施,选择库周典型小流域,开展水体氮素浓度系统观测和分析。结果显示:(1)余家湾(养殖型)总氮浓度平均为21.23 mg/L,五龙池(村落型)总氮浓度平均为4.00 mg/L,高于钱家沟(自然型)和张沟(农田型);五龙池(村落型)硝态氮浓度最高,平均为2.37 mg/L,张沟最低,平均为1.06 mg/L;余家湾(养殖型)氨氮浓度远高于钱家沟(自然型)、五龙池(村落型)和张沟(农田型)。(2)钱家沟(自然型)氨氮浓度沿程下降趋势显著(p0.05);张沟(农田型)硝态氮(p0.01)和总氮浓度(p0.01)沿程上升趋势显著,坑塘湿地等微地形结构可能是影响小流域氮素的沿程变化的主要因素。(3)钱家沟(自然型)和五龙池(村落型)氮素冬季(12～2月)浓度较高,夏秋季(6～11月)浓度较低,春季(3～5月)波动最大;张沟(农田型)氮素高值出现在6月;余家湾(养殖型)氮素浓度高值出现在8月。(4)余家湾(养殖型)氮素以氨氮为主,五龙池(村落型)、张沟(农田型)和钱家沟(自然型)以硝态氮为主。基于上述结论,后续丹江口库区氮素控制应系统梳理不同类型小流域的分布和数量,重点关注养殖型小流域的氨氮污染和村落型小流域的硝态氮污染。

Characteristics of Nitrogen Distribution in Typical Small Watershed in Danjiangkou Reservoir Area

Abstract：The water quality of Danjiangkou reservoir is good on the whole, but the problem of excessive total nitrogen is prominent. To clarify the distribution and output characteristics of nitrogen in different types of small watershed, and optimize the formulation of nitrogen control measures in the reservoir area, typical watershed around the reservoir was selected to carry out observation and analysis of nitrogen concentration in water. The results showed: (1) The average total nitrogen content in Yujiawan (hoggery type) was 21.23 mg/L, and that in Wulongchi (village type) was 4.00 mg/L, higher than that in Qianjiagou (natural type) and Zhanggou (farmland type). Wulongchi had the highest nitrate nitrogen, with an average of 2.37 mg/L, while Zhanggou had the lowest, with an average of 1.06 mg/L. The content of ammonia nitrogen in Yujiawan is much higher than that in Qianjiagou and Zhanggou. (2) The downward trend of ammonia nitrogen along Qianjiagou was significant (p<0.05), and the nitrate nitrogen (p<0.01) and total nitrogen (p<0.01) increased significantly in Zhanggou. The micro-topographic structure such as the pit wetland may be the main factor affecting the nitrogen change along the small watershed. (3) The concentration of nitrogen in Qianjiagou and Wulongchi was higher in winter (from December to February), lower in summer and autumn (from June to November), and fluctuated the most in spring (from March to May). The high value of nitrogen in Zhanggou appeared in June, while the high value of nitrogen concentration in Yujiawan appeared in August. (4) In Yujiawan, ammonia nitrogen was the main nitrogen. In Wulongchi, Zhanggou and Qianjiagou, nitrate nitrogen dominated. Based on the above conclusions, the distribution and quantity of different types of small watershed should be systematically sorted out for subsequent nitrogen control in danjiangkou reservoir area, with the emphasis on ammonia nitrogen pollution in hoggery type small watershed and nitrate nitrogen pollution in village type small watershed.