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磷素(P)在环境中的过量累积是导致农业面源污染的主要因素。论文以湖南省长沙县脱甲河农区小流域(52 km2)和涧山河森林-农区小流域(50 km2)为研究单元,基于入户调查资料和连续4 a的流域把口站水文水质定位观测数据,采用物质流分析法,对比研究了亚热带丘陵区典型小流域P的收支平衡及流失特征。结果表明,农区小流域出口地表水总磷(TP)含量变化为0.03~0.68 mg·L-1,平均含量为0.21 mg·L-1,整体达到Ⅲ类水质标准;森林-农区小流域TP含量变化范围为0.01~0.35 mg·L-1,平均为0.08 mg·L-1,整体为Ⅱ类水质,表明森林-农区小流域地表水水质明显优于农区小流域。农区小流域P的环境滞留强度(32.0 kg·hm-2·a-1)显著高于森林-农区小流域(20.6 kg·hm-2·a-1),对环境影响更大。以2013年为例,农区小流域P的主要输入项为饲料,占53.1%,森林-农区小流域则以肥料为主,占53.0%;两个流域的P输出项都以植物和畜禽产品输出为主,均占总输出量的94.0%左右。控制小流域肥料和饲料投入、增加循环利用途径以及提高P利用率是当前减轻水体富营养化的有效途径。
Over-accumulation of phosphorus (P) in the environment is the main factor leading to agricultural non-point source pollution. Based on the household survey data and the continuous 4-a-year watersheds, the hydrology and water quality of the station (52 km2) and the Jian Shan River forest-small watershed of a farming village (50 km2) Positioning observation data, the use of material flow analysis method, a comparative study of the P subtropical hilly typical small P balance and loss characteristics. The results showed that the total phosphorus (TP) content in the surface waters of the small watershed at the agricultural area varied from 0.03 to 0.68 mg · L-1 with an average content of 0.21 mg · L-1, which met the Grade Ⅲ water quality standards as a whole. The forest- TP content ranged from 0.01 mg / L to 0.35 mg · L-1 with an average of 0.08 mg · L-1, indicating that the surface water quality of small watershed in forest-agri-culture was significantly better than that in small watershed. The retention of soil P (32.0 kg · hm-2 · a-1) in the small watershed of the agricultural area was significantly higher than that of the small-scale forest-agricultural area (20.6 kg · hm-2 · a-1) and had a greater environmental impact. Taking 2013 as an example, the main input of P in the small farmland is feed, accounting for 53.1% of the total. The forest-farm small watershed is dominated by fertilizers, accounting for 53.0% of the total. The P outputs of the two basins are based on plants and livestock The main output of poultry products, both of the total output of about 94.0%. It is an effective way to reduce the eutrophication of water body by controlling the input of fertilizers and feeds in small watersheds, increasing the recycling ways and increasing the utilization rate of P.