宁夏引黄灌区种植业面源污染流失量模拟

Simulation of non-point source pollution losses from farmland in Yellow River irrigation area of Ningxia

为揭示灌区种植业氮磷流失规律与空间分布格局,基于水量平衡与土壤物理化学吸附理论,构建了宁夏引黄灌区种植业面源污染流失量轻简化模型,模拟了灌区玉米、小麦和水稻氮磷流失的时间特征与空间格局。模拟结果表明:灌区主要作物退水氮磷流失量的时间变异大,玉米春灌流失量、小麦春灌头水流失量和水稻分蘖期流失量是各自灌水周期氮磷流失量的最高值;灌区农田总氮(TN)流失量(以N计)为887.51 t,玉米、小麦和水稻分别贡献了25%、8%和67%,平均氮流失系数为1.99%;灌区农田总磷(TP)流失量为48.05 t,玉米、小麦和水稻分别贡献了19%、18%和63%,平均磷流失系数为0.15%;种植业氮磷流失量最大的区县为平罗县,氮磷流失系数最大的区县为兴庆区,永宁县中部以及河东地区东部是氮磷流失的热点区域。该模型反映了农田管理、降水和土壤条件等过程对退水量和退水中氮磷浓度的影响,模型参数少、物理机制明确,可用于宁夏引黄灌区种植业面源污染流失量模拟。

To reveal the patterns and spatial distributions of nitrogen and phosphorus losses from farmland in an irrigation area,we built a simplified model of non-point source pollution losses based on the theory of water balance and soil physicochemical adsorption in the Yellow River irrigation area in Ningxia.We then simulated the temporal and spatial patterns of nitrogen and phosphorus losses for wheat,maize,and rice in the irrigated area.The results showed that the variations in losses were large,with the highest losses occurring during spring irrigation for maize and wheat and during tillering stage irrigation for rice.The TN loss in the irrigation area was 887.51 t,to which maize,wheat,and rice contributed 25%,8%,and 67%,respectively;the average loss coefficient was 1.99%.The TP loss in the irrigated area was 48.05 t,to which maize,wheat,and rice contributed 19%,18%,and 63%,respectively;the average loss coefficient was 0.15%.The largest nitrogen and phosphorus losses occurred in Pingluo County compared with those in other counties;we found the largest nitrogen and phosphorus loss coefficients in Xingqing District compared with those in the other counties.Central Yongning County and the eastern Yellow River were hotspots for nitrogen and phosphorus losses.In conclusion,we found that our model reflected the effects of farmland management,precipitation,and soil conditions on the volume and concentration of nitrogen and phosphorus in drainage water.Moreover,the model has few parameters and a clear physical mechanism.Therefore,the model may be used to simulate non-point source pollution losses from farmland in the irrigated Yellow River area of Ningxia.