三峡库区湖北段消落带氮磷含量分布及流失特征研究

发布时间：2018-08-22 19:13

【摘要】：三峡大坝对于保障社会经济、水资源安全和生态屏障方面具有重要的影响。本文研究了三峡库区湖北段消落带氮磷含量分布及其流失特征,以期为三峡库区消落带防治水土流失,控制氮磷流失以及降低农业面源污染提供一定的理论依据。本研究通过采集消落带三种母质(紫砂岩、花岗岩、石灰岩)研究区域内不同水位高程下的土、水样品,并在水库以最低水位运行期间,选择库区内广泛分布的紫砂岩母质区域进行模拟径流冲刷试验,最后统计分析了三峡大坝蓄水前后、库区不同研究区域的氮磷含量以及赋存形态变化规律。得到以下研究结果:(1)不同水位高程的土壤容重分布在1.35~1.53 g/cm3之间,均值为1.45±0.06 g/cm3;总孔隙度分布在41.87~49.81%之间,均值为46.79±2.57%。随着海拔升高,消落带表层土壤容重逐渐增大,总孔隙度逐渐降低,砂粒含量(28.62~51.74%)逐渐升高;随着水位海拔升高,土壤表层土壤pH(6.87~6.57)逐渐降低,土壤有机质和全氮逐渐升高,有机质含量分布在8.54~22.85 g/kg之间,均值为14.22±9.68 g/kg,土壤全氮、全磷含量分别分布在0.15~0.76 g/kg和0.16~0.29 g/kg之间,均值分别为0.51±0.18 g/kg和0.22±0.04 g/kg。水样中总氮总磷含量随着水位下降而升高,而水质逐渐变差,且不同母质水样中全氮含量存在极显著差异,水样中全磷含量则未表现出显著性差异。(2)径流中氮磷浓度随时间的变化趋势大致相同,均是在放水冲刷的初期达到最大浓度,然后呈现逐渐下降的趋势,并在一定时间之后慢慢趋于稳定。初始总氮和总磷浓度分别分布在50.44~66.09 mg/L和68.56~85.06 mg/L之间;硝态氮和铵态氮初始浓度分别分布在16.91~20.57 mg/L和22.41~34.26 mg/L之间。指数函数能较好地拟合径流中氮磷浓度随冲刷时间的变化过程。草带对于氮磷的拦截效率为TNNO3--NNH4+-NTP,对径流中各氮素指标的拦截效率在85.7%以上,对总磷的拦截效率在61.3%以上;随着宽度的增加,草带对于氮磷的拦截效率增强;随着冲刷强度的增大,草带对氮磷的拦截能力均有一定程度的降低;通过对比冲刷前后各层次土壤中氮磷含量发现冲刷结束后氮磷在土壤表层有较高程度的富集,表明草带拦截的氮磷多被土壤所蓄存,各氮磷养分变化率分别于冲刷强度、土层深度呈现负相关关系,随着冲刷强度和土层深度的增加,氮磷在土层中的富集程度随之降低。(3)产流时间随着冲刷强度的增大而显著减小,产流速率随冲刷强度的增大而显著递增。具体表现:中、高冲刷强度(90、120 mm/h)相比低冲刷强度(60mm/h)的产流时间分别缩减了22.9%、40.8%(5 m草带)和16.3%、69.5%(10m草带),而中、高冲刷强度下的稳定产流速率分别是低冲刷强度下的1.48、3.10倍(5 m草带)和1.54、2.40倍(10 m草带)。累积径流量随着产流历时的延长而逐渐增加,二者之间具有显著的线性相关关系。径流小区上、下坡位不同深度(5、10、20、30 cm)土壤含水量对径流冲刷的响应模式存在显著的差异。上坡表层土壤含水量上升幅度最大,增幅约0.10 v/v;30 cm深度土壤含水量增加缓慢,增幅范围为0.009~0.012 v/v。下坡10 cm深度土壤含水量增幅(0.121 v/v)最大。(4)在三峡水库正式蓄水后,总氮总磷含量较蓄水前有不同程度的降低,库区湖北段的氮磷含量普遍低于重庆段,全磷含量随着淹水时间的延长而降低。氮磷的不同赋存形态是影响其吸附和释放的重要因素。Fe-Al/P(铁-铝磷)是TP中含量最低的一种赋存形态,但也对沉积物向上覆水体释放磷素造成影响。Ca-P(钙磷)是TP中含量最高的一种赋存形态,属于稳定态的磷,不易被生物吸收利用。OSF-N(有机硫化物结合态氮)和CF-N(碳酸盐结合态氮)含量占据TF-N(可转化态氮)的绝大部分,而IEF-N(离子交换态氮)和IMOF-N(铁锰结合态氮)占比相对较小。
[Abstract]:The Three Gorges Dam has an important impact on social economy, water resources security and ecological barrier. This paper studies the distribution of nitrogen and phosphorus content and its loss characteristics in the ebb zone of Hubei section of the Three Gorges Reservoir area, in order to provide a theoretical basis for preventing and controlling soil erosion, controlling nitrogen and phosphorus loss and reducing agricultural non-point source pollution in the ebb zone of the Three Gorges Reservoir area. According to this study, soil and water samples of three parent materials (purple sandstone, granite and limestone) in the study area were collected and simulated runoff scouring test was carried out in the purple sandstone parent material area widely distributed in the reservoir area during the operation of the reservoir at the lowest water level. The results are as follows: (1) Soil bulk density at different water levels ranges from 1.35 g/cm 3 to 1.53 g/cm 3, with an average value of 1.45.06 g/cm 3; total porosity ranges from 41.87% to 49.81%, with an average value of 46.79.57%. With the increase of water level and elevation, soil pH (6.87-6.57) gradually decreased, soil organic matter and total nitrogen gradually increased, organic matter content ranged from 8.54 g/kg to 22.85 g/kg, with an average value of 14.22 + 9.68 g/kg, soil total nitrogen and total phosphorus content ranged from 0.15 to 0.15 g/kg, respectively. The total nitrogen and phosphorus content in the water sample increased with the water level decreasing, but the water quality gradually deteriorated, and the total nitrogen and phosphorus content in the different parent material water samples had extremely significant difference, but the total phosphorus content in the water sample did not show significant difference at any time. The initial concentrations of total nitrogen and phosphorus were 50.44-66.09 mg/L and 68.56-85.06 mg/L, respectively, and the initial concentrations of nitrate and ammonium nitrogen were 16.91-20.5, respectively. The interception efficiency of straw strip for nitrogen and phosphorus was TNNO3 - NNH4 + - NTP, the interception efficiency of each nitrogen index in runoff was above 85.7%, and the interception efficiency of total phosphorus was above 61.3% with the increase of straw width. The interception efficiency of nitrogen and phosphorus increased; with the increase of scouring intensity, the interception ability of grassland to nitrogen and phosphorus decreased to a certain extent; through the comparison of nitrogen and phosphorus content in different layers of soil before and after scouring, it was found that nitrogen and phosphorus had a higher degree of enrichment in the soil surface layer after scouring, indicating that nitrogen and phosphorus intercepted by grassland were mostly stored by the soil, and the nitrogen and phosphorus nutrients of each layer were stored (3) Runoff yield time decreases significantly with the increase of erosion intensity, and runoff yield rate increases significantly with the increase of erosion intensity. Specifically, high erosion intensity (90%). The runoff yield time at 120 m m/h was reduced by 22.9%, 40.8% (5 m straw belt) and 16.3%, 69.5% (10 m straw belt) respectively, compared with that at 60 m m/h. The steady runoff yield rate at high erosion intensity was 1.48, 3.10 times (5 m straw belt) and 1.54, 2.40 times (10 m straw belt) respectively, and the cumulative runoff increased gradually with the extension of runoff duration. There was a significant linear correlation between the two. In the runoff plot, the response patterns of soil water content to runoff scouring at different depths (5,10,20,30 cm) on the downhill slope were significantly different. (4) After the Three Gorges Reservoir was formally impounded, the content of total nitrogen and phosphorus decreased to some extent. The content of total nitrogen and phosphorus in Hubei section of the reservoir area was generally lower than that in Chongqing section. The content of total phosphorus decreased with the prolongation of flooding time. Fe-Al/P (Fe-Al/P) is the lowest form of phosphorus in TP, but it also affects the release of phosphorus from sediments to overlying water. Ca-P (calcium and phosphorus) is the highest form of phosphorus in TP. It is a stable form of phosphorus and is not easily absorbed by organisms. OSF-N (organic sulfide bound nitrogen) and CF-N (carbonate formation). The content of TF-N occupies the most part of TF-N, while the proportion of IEF-N and IMOF-N is relatively small.
【学位授予单位】：华中农业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S157

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