不同尺度排水沟道对稻田退水中氮磷的削减规律及影响因素研究

REMOVAL PERFORMANCE OF NITROGEN AND PHOSPHORUS IN FARMLAND DRAINAGE BY DIFFERENT SCALE DRAINAGE DITCHES AND THE INFLUENCE FACTORS

针对我国大中型灌区典型的农田排水体系(毛-农-斗-支-干多级排水沟道),以上海市崇明岛新海农场的稻田为切入点,运用单因素方差分析和主坐标分析对农田排水水质进行评价,研究不同尺度排水沟道中氮、磷污染物的时空变化特征,并揭示逐级排水系统对氮、磷污染物的去除规律;结合Spearman相关性分析,探明影响不同尺度排水沟道中氮、磷去除效率的主要因素。结果表明:不同尺度农田排水沟道中NH^(+)_(4)-N、NO^(-)_(3)-N、NO^(-)_(2)-N、AP和PP浓度在水稻全生长期内总体表现出与TN、TP相一致的变化规律,即水稻播种期(6月)和分蘖期(7月)浓度较高,灌浆成熟期(10月)最低,抽穗扬花期(8月)呈大幅波动状态。毛-农-斗-支-干沟道分别可削减TN为13.30%、39.24%、11.23%、5.27%、8.86%和TP为13.20%、36.57%、9.10%、13.18%、11.07%。农田排水沟道的尺度效应是引起水体理化性质变化,进而造成氮、磷去除效率差异的重要原因。农沟独特的尺寸结构和环境特征使其成为削减氮、磷的热区,在今后的生态型排水通道建设中应加强对农沟的生态化改造。

Aiming at the typical farmland drainage system(multilevel field-sublateral-head-branch-trunk ditch)in the large and medium-sized irrigation districts of China,this paper selected the rice field of Xinhai Farm in Chongming Island of Shanghai as a starting point,which the one-way analysis of variance and principal coordinate analysis were used to evaluate the drainage water quality of farmland.In order to study the temporal and spatial variation characteristics of nitrogen and phosphorus pollutants in drainage ditches of different scales,and reveal the removal rules of nitrogen and phosphorus pollutants in the step-by-step drainage system.Combined with Spearman correlation analysis,the main factors affecting the removal efficiency of nitrogen and phosphorus in drainage ditches of different scales were identified.Results indicated that ammonia nitrogen,nitrate nitrogen,nitrite nitrogen,available phosphorus and particulate phosphorus in farmland drainage ditches of different scales showed the same change law as total nitrogen and total phosphorus during the whole growing period of rice,that is,the rice seeding period(June)and tillering period(July)had higher concentrations,while the filling maturity period(October)had the lowest concentration,and the heading and flowering period(August)fluctuated greatly.Multilevel fieldsublateral-head-branch-trunk ditch can remove 13.30%,39.24%,11.23%,5.27%,8.86%of total nitrogen and 13.20%,36.57%,9.10%,13.18%,11.07%of total phosphorus,respectively.The scale effect of farmland drainage ditches was the main reason for the changes in the physical and chemical properties of water bodies,which in turn led to the differences in nitrogen and phosphorus removal efficiency.The unique size structure and environmental characteristics of sublateral ditches made it a hot point for reducing nitrogen and phosphorus,so the ecological renovation of sublateral ditches should be strengthened in construction of ecological drainage ditches in the future.