【作者】 肖敏；

【导师】 郭劲松；

【作者基本信息】 重庆大学 ， 市政工程， 2010， 硕士

【摘要】 水体中氮磷营养物含量超标是引起水体富营养化的关键因素之一,而农业面源污染已成为库区水体营养物的重要来源。农业面源污染物质氮、磷流失是与土壤营养物含量之间存在较强的联系,土壤营养物的累积可增大流失风险。因此,测定土壤营养物含量可为氮、磷流失风险及其对水环境的影响提供依据。论文对三峡库区重庆市忠县石宝镇新政村小流域农业种植区域5种不同土地利用类型的20个点位的土壤本底值进行了一年的原位监测,探讨库区典型小流域坡耕地不同土地利用类型土壤营养物含量年内变化趋势和空间分布规律,为研究农业面源污染物质的迁移过程及转化行为奠定基础;进一步分析了土壤样品易溶性营养物,调查了小流域农田排水沟渠径流营养物流失特征,以评估研究区域土壤营养物潜在的流失风险。论文得到以下主要结论:①研究范围内,小流域土壤有机质含量呈小幅先升高后降低的趋势,季节性差异不明显,土壤全氮、全磷含量随时间均呈小幅增加趋势,因季节不同存在一定差异。②研究区域小流域土壤有机质含量均值为(14.44±3.57)g/kg,土壤全氮均值为(1.03±0.26)g/kg,土壤全磷均值为(0.54±0.18)g/kg。不同土地利用类型土壤有机质、土壤全氮、土壤全磷含量存在显著差异。与不同地区小流域土壤营养物含量相比较,研究区域内土壤氮、磷平均含量均处于较低水平。③小流域从坡上果林地到坡下水稻田的顺坡采样带上,不同坡位处土壤营养物含量之间有较大的差异。土壤有机质、土壤全氮含量呈先逐渐增大再降低的趋势;土壤全磷含量呈先降低后增加的趋势。④小流域土壤矿质氮含量平均值为(15.99±13.64) mg/kg,最高值为最低值的12.6倍,各土地利用类型土壤矿质氮含量均值依次果林地>水田>库岸草地>旱田>消落带;小流域土壤有效磷含量均值为(32.14±32.63)mg/kg,土壤水溶磷含量均值为(2.46±2.21)mg/kg,不同土地利用类型土壤有效磷和水溶磷含量由高到低依次是果林地>旱地>水稻田>库岸草地>消落带。⑤小流域农田排水沟渠经流TN监测平均值达到《地表水环境质量标准》中的Ⅲ类限值的12倍,TP多次监测平均值达到地表水环境质量标准中的Ⅲ类限值的近2倍;径流中溶解态氮占TN的54.7%,溶解态磷占TP的63.3%,农田土壤营养物主要以溶解态流失为主。⑥研究范围内果林地、水田和库岸草地为铵态氮流失的高风险区域,旱地、消落带和果林地是硝态氮流失的高风险区域;研究范围内土壤磷素流失发生所对应的有效磷、水溶磷临界值分别为60.79mg/kg、3.04 mg/kg,果林地土壤样品50%超过临界值,流失风险最高,旱田仅少量样品超过临界值,总体上流失风险较小,而水稻田流失风险最小。更多还原

【Abstract】 The exceeding of nitrogen and phosphorus is one of the key factors that cause the eutrophication. Agricultural non-point source pollution has become the most important source of nutrient for the reservoir and has brought huge damage to the water environment. Studies have shown that the soil nutrient loss has strong connection with its content, and the accumulation of soil nutrient can increase the loss potential. Therefore, the determination of soil nutrient content can be used to assess the loss risk and environmental impact degree.Soil nutrient background value of 20 sampling points of five different types of land use were monitored in situ in 2009, and the changing trends by time and spatial distribution of soil organic matter, soil nitrogen and soil phosphorus were studied to lay the foundation for understanding the agricultural non-point pollutant migration process and the transformation behavior. The form of soil nitrogen and phosphorus were analyzed of soil samples of different season. Rainfall runoff samples were collected in August from agricultural drainage ditches in the watershed, and the characteristic of the runoff nutrient loss were analyzed. Appropriate methods were adopted to evaluate the potential of soil nutrient loss in research area and help to understand how the loss of agricultural non-point source pollution of nitrogen, phosphorus influence the receiving water body. The thesis draws following conclusions:The content of soil organic matter of the whole watershed has no obvious difference among seasons and the changing of content of forest land, rice paddies, dry land with time are small. The soil nitrogen, phosphorus content slightly increase over time and there is some difference in different seasons.The average content of soil organic matter in research area is (14.44±3.57) g/kg, the average content of soil nitrogen in research area is (1.03±0.26) g/kg, and the average content of soil nitrogen in research area is (0.54±0.18) g/kg. The content has significant differences among different types of land use. Compared with small watershed of other different regions, soil nitrogen and soil phosphorus content of research area is much lower.Along the top of the slope to base of the slope in the watershed, the soil nutrients show different disciplines. Soil organic matter totally increased with a relatively slower decrease after the increase. Soil nitrogen is showing a trend of gradual increase, whereas soil phosphorus is totally decreasing following with a relatively slower increase.The average content of soil mineral nitrogen is (15.99±13.64) mg/kg, the ranking of the content of different land use from high to low is forest land, paddy field, grass land, dry land and riparian land. The average content of Olsen-P and water soluble phosphate is (32.14±32.63) mg/kg and (2.46±2.21) mg/kg, and the ranking of these content of different land use from high to low is forest land, dry land ,paddy field, grass land and riparian land.The total nitrogen (TN) in runoff from agricultural drainage ditches is 12 times of the third limit for surface water environment quality standards, and the dissolved nitrogen in runoff accounts for 54.7% of TN. The total phosphorus (TP) in runoff from agricultural drainage ditches is 2 times of the third limit for surface water environment quality standards, and the dissolved phosphorus in runoff accounts for 63.3%% of TP. Soil nutrient are lost mainly in the form of dissolved shape .The soil of forest land, paddy field, and grassland will have high potential of loss with runoff erosion. The forest land, dry land and riparian land has much higher content of nitrate nitrogen where the potential of loss with runoff erosion will be higher. The critical loss content of soil Olsen-P is 60.79mg/kg and the according critical loss content of water soluble phosphate is 3.04 mg/kg. The ranking of the phosphorus loss risk content of different land use from high to low is forest land, dry land and paddy field.更多还原