珠三角典型区域农田小区尺度氮、磷、镉、砷输移特征与控制对策

Transport fluxes of nitrogen, phosphorus, cadmium and arsenic at farmland plot scale in the typical areas of Pearl River Delta region

  • 摘要: 区域氮、磷、镉、砷输移变化是影响农业生产、导致农田面源污染的主要因素。基于土壤表观平衡模型,以珠三角流域佛山市农业科学研究所试验农田为典型研究区域,构建农田小区尺度土壤表观氮、磷、镉、砷平衡模型,对4种元素在土壤中输移结构和平衡进行分析。结果表明:研究区域4种元素的主要输入途径是施肥,而输出的主要形式各有不同。其中,氮、磷主要输出形式是作物富集输出,输出占比分别为57.5%和39.0%;镉、砷主要输出形式分别是地表径流和作物富集输出,输出占比分别为66.7%和10.7%。研究区域4种元素均出现了不同程度土壤富集现象,农田小区尺度氮、磷平衡处于盈余状态,而镉、砷平衡处于亏损状态,4种元素的平衡强度分别为37.40、8.88、−1.35和−20.50 kg/(hm2·a),仅氮、磷未超过当地土壤环境安全阈值。分析试验农田中5类蔬菜各部位镉、砷富集情况发现,砷的富集系数均达到70.0%以上,而镉的富集只在辣椒叶中较为突出,富集系数达到57.5%。研究显示,应重视肥料输入的有效利用,加强农田灌溉水、农作物和地表径流中重金属的监测,以保障区域粮食安全和水环境安全。

     

    Abstract: The transport of nitrogen, phosphorus, cadmium and arsenic is the main factor affecting agricultural production as well as a significant non-point source of pollution of farmland. Taking the experimental farmland of the Foshan Institute of Agricultural Science and Technology (FIAST) in the Pearl River Delta as a typical research area, and based on the soil apparent balance model, a soil apparent balance model of nitrogen, phosphorus, cadmium and arsenic was constructed at the farmland plot scale, to analyze the transport structure and balance of nitrogen, phosphorus, cadmium and arsenic in the soil. The results showed that fertilization was the main input of the four elements in the study area, but the main outputs were different. The main output of nitrogen and phosphorus was crop enrichment, accounting for 57.5% and 39.0%, respectively, whilst the main outputs of cadmium and arsenic were surface runoff and crop enrichment, accounting for 66.7% and 10.7%, respectively. The enrichment was observed for all four elements in the study area to different degrees. On the plot scale, the balance of nitrogen and phosphorus was in surplus, while cadmium and arsenic were in deficit, with their intensity being 37.40, 8.88, −1.35 and −20.50 kg/(hm2·a), respectively. Nitrogen and phosphorus were within the local soil environmental safety thresholds. The analysis of cadmium and arsenic enrichment in five types of vegetables showed that the enrichment coefficient of arsenic was greater than 70.0% in all the types of vegetables, while the enrichment of cadmium was only found in pepper leaves, with a coefficient of 57.5%. Therefore, more attention should be paid to the effective utilization of fertilizer input and the monitoring of heavy metals in irrigation water, crops and surface runoff to ensure regional food security and water quality.

     

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