太湖流域雪堰镇氮素流失规律及形态特性

Regularity and characteristic form of nitrogen losses in the Xueyan town of Taihu Lake basin

以太湖流域雪堰镇为例,通过2009年3月～2010年2月连续12个月及两场次降雨事件的水质监测进行分析,研究不同河流、月份、区域、汛情、土地利用类型下氮素流失规律及形态特性,分析降雨过程中不同尺度3个流域(上涧村、龙泉河、雪堰镇)氮流失特征和不同河段氮流失规律。研究结果表明,雪堰镇氮素为劣Ⅴ类,非汛期污染比汛期严重,变化幅度大,不稳定,氮以溶解态为主,溶解态氮以硝氮为主;镇区硝氮浓度较非镇区低,氨氮比非镇区高,坑塘水面氮流失最严重,有林地(乔木较多)氮流失最少,茶园硝氮占溶解态氮百分比最高,果园氨氮占溶解态氮百分比最高;降雨前期未产流前氮素流失稳定,产流后流失越来越大,不同河段氮沿程变化基本稳定。

The water quality in the Xueyan town of the Taihu Lake basin was continuously monitored for 12 consecutive months from March 2009 to February 2010 during which two typical rainfall events were encountered. Accordingly, a study on the regularity and characteristic form of nitrogen losses was conducted in the context of different river systems, months, reglons, flooding and land-use types. In addition, three studying sites （Shangjian village, Longquan River, Xueyan town） with different spatial scales were selected for analyzing these pollution characteristics during the two rainfall events. The result shows that nitrogen in Xueyan town water is even worse than Category V, and the nitrogen＇s most common form is found in the liquid state of nitrate nitrogen. Compared to flooding seasons, the level of nitrogen pollution will be higher over non-flooding seasons. The pollutant load is highly variable and unstable. More specifically, the nitrate nitrogen concentration the townships are lower than that in non-townships. However, the oppo- site is true for the ammonia nitrogen concentration. Most nitrogen losses are found in ponds, and woodlands （arbor more） had the lowest nitrogen loss. In tea gardens, the nitrate nitrogen has the highest percentage of dissolved nitro- gen; while the ammonia nitrogen is the predominant compound in dissolved nitrogen in orchard gardens. Before runoff being generated during a rainfall event, the nitrogen loss is stable. With the increase of runoff, the loss will in- crease. The increase rate is along different sections of a river.