• 关键词：农闲期  西北江三角洲  城郊农田  灌溉系统  水环境  单因子标识指数法  综合水质标识指数法

• 基金项目：国家重点研发计划项目（No.2017YFD0801300）

• 任杰
• 1. 兰州交通大学, 环境与市政工程学院, 兰州 730070;2. 生态环境部华南环境科学研究所, 广州 510655

• 刘晓文
• 生态环境部华南环境科学研究所, 广州 510655

• 吴颖欣
• 生态环境部华南环境科学研究所, 广州 510655

• 张杰
• 生态环境部华南环境科学研究所, 广州 510655

• 曹天轶
• 兰州交通大学, 环境与市政工程学院, 兰州 730070

• 李杰
• 兰州交通大学, 环境与市政工程学院, 兰州 730070

• 张永利
• 中国科学院广州地球化学研究所, 广州 510640

• 摘要：摸查了农田灌溉系统水环境经农（夏）闲期降水等外部强干预调理后的环境污染物含量——该值理论上是环境自净作用之后的最不利值，对农田灌溉系统水环境进行水质评价，探究其对农田土壤质量的潜在污染风险.于2019年6月中旬—7月下旬（降雨集中期），分别在西北江三角洲城市（清远市、佛山市和江门市）实验基地周边筛选研究区，并在雨后对有覆水的水源区域、灌渠、蓄水池和田间水等采集上覆水，共采得水样27×2份，对其pH值、悬浮物（SS）、矿化度、总磷（TP）、氨氮（NH₄⁺-N）、Cd、As、Pb、Cu和Zn的含量进行检测；对各研究区pH值、SS的成因和影响，矿化度的等级，重金属均值分布等进行分析；对全样品TP、NH₄⁺-N、重金属含量进行Pearson相关性分析和描述性特征分析；通过单因子水质标识指数P_i和综合水质标识指数P分别对各采样点、各构成项目和各研究区进行水质评价.研究发现雨后农田灌溉系统水环境构成复杂，物质呈无显著性差异的迁移，灌溉沿程上覆水中大部分物质可能处于动态平衡，受局部环境影响变小，TP、NH₄⁺-N和重金属等迁移物质主要还是灌溉水体中原有的，受外力驱动扰动后在水动力作用下可能以氮磷结合形态沿灌溉系统发生远距离迁移；使用河流水质标识指数法评价农田灌溉系统水环境，发现该法可以刻画局部灌溉的水质态势，对农田灌溉系统水环境的含量特征评价做出科学、合理的解释，也可以做出综合性定量评价.虽然灌溉水系统结构差异较大，但是从整体上可以初步得出农闲期西北江三角洲农田灌溉水的灌溉风险不高的结论，总体综合水质评价级别为Ⅰ类~Ⅱ类，达到水环境功能区的使用要求.

• Abstract：The contents of environmental contaminants in the water within the irrigation system during the (summer) slack season after intensive intervention, such as heavy precipitation, were investigated, which was theoretically the worst case after environmental self-purification. The quality of irrigation water was evaluated; and its potential pollution risk to farmland soil was explored. From mid-June to late July 2019 (Rainfall concentration period), the study areas were screened in the neighbouring of experimental field of Northwest River Delta cities (Foshan City, Jiangmen City and Qingyuan City), and the overlying water was collected from the water source areas, irrigation channels, cisterns and field after the rain. A total of 27×2 water samples were collected to detect the pH, suspended solids (SS), salinity, total phosphorus (TP), ammonia nitrogen (NH₄⁺-N), Cd, As, Pb, Cu and Zn. The change of pH, the source and effect of SS, the grade of salinity, and the distribution of heavy metals in each study area were analyzed. Pearson correlation analysis and descriptive characterization of the contents of TP, NH₄⁺-N and heavy metals were conducted. Single factor water quality labeling index P_i and the comprehensive water quality labeling index P were used to evaluate the water quality of each sampling point, component item and research area. The irrigation water environment is complex and there is no significant difference in substance migration. Most of the substances in the overlying water of irrigation may be in dynamic equilibrium, which is less affected by local environment. TP, NH₄⁺-N, heavy metals and other migration substances are mainly original in irrigation water. After the disturbance by external force, it would migrate in a long distance along the irrigation system under the action of hydrodynamic force in combination with nitrogen and phosphorus. The river water quality index method was appropriate to evaluate the quality of irrigation water. It is found that this method can describe the water quality of local irrigation, and can make a scientific and reasonable evaluation of the water environment content of the farmland irrigation system, and also make a comprehensive quantitative evaluation. Although there is a large difference among the three studied irrigation systems, it can be preliminarily concluded that the ecological risk of farmland irrigation water is not high in the Northwest River Delta during the agricultural slack period. The overall comprehensive water quality evaluation level is class I~class II, which meets the requirements for the use of water environment function zones.

• Key words：slack farming period  North River and West River Delta  suburban farmlands  irrigation system  water environment  single factor identification index method  comprehensive water quality index method

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