南方低山丘陵区稻田氮磷排放的尺度效应

Scale Effects of the Emission Laws of Nitrogen and Phosphorus from Paddy Fields in South China's Hills

在典型南方低山丘陵区的水稻种植区浙江省永康市姚塘村,选取封闭性较好且逐级嵌套的5个尺度,于2013年7-10月水稻生育期监测各尺度试区进出口水量,并采集排水水样进行氮磷浓度化验,以研究稻田氮磷排放负荷随不同尺度的变化规律及其原因。结果表明,稻田氮、磷素排放负荷随着尺度的增大先增加而后降低,即存在尺度效应。总氮、总磷、铵态氮、硝态氮的排放负荷从田间尺度到支沟尺度分别下降了70.8%、69.4%、46.7%、79.1%。氮磷排放负荷产生尺度效应的原因是排水的重复利用及氮磷在向下游迁移过程中在各级排水沟或塘堰中被净化。因此,对于农田氮磷排放对下游水体污染的评价应考虑其尺度效应。

In a typical hilly area of southern rice-growing area Yongkang Yaotong, five nesting scales composing of subbasins were se- lected to analyze the variation and their causes of nitrogen and phosphorus emission load by measuring water quantity of inlet and out- let at different scales and collecting water samples for nitrogen and phosphorus analysis during the whole rice growing season from July to October in 2013. The results show that the emission load of nitrogen and phosphorus increases as the scale increases first and then decreases. From field scale to ditch scale, the emission load of total nitrogen, total phosphorus, ammonia nitrogen, nitrate ni- trogen decreases by 70. 8%, 69.4%, 46. 70% ,79. 1% respectively. The scale effect is caused by the reuse of drainage and purification of nitrogen and phosphorus pollutants in both ponds and drainage ditches in the process of downstream migration. Therefore, scale effect should be taken into consideration for nitrogen and phosphorus emissions on downstream water pollution evaluation.