IMHE OpenIR  > 山地表生过程与生态调控重点实验室
紫色丘陵区典型小流域磷素迁移特征
Alternative TitleCharacteristics of Phosphorus Loss in Some Typical Small Watersheds in the Hilly area of Purple Soil
Language中文
沈茜
Thesis Advisor朱波
2014
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name硕士
Degree Discipline环境工程
Keyword支沟 小流域 土地利用 磷迁移过程 径流与泥沙 非点源污染
Abstract磷是植物生长发育所必须的大量元素之一,也是农田生态系统生产力的主要限制因素之一,但过量施用磷肥也带来环境问题,非点源磷污染已成为水体富营养化的关键源。近年来农业过量施用磷肥和随意分散排放的村镇生活和生产废水等污染源含有大量磷,它随降雨径流或泥沙由陆地向水生态系统迁移导致水体中磷污染负荷增加。紫色丘陵区位于长江上游生态屏障的最前沿,是三峡水库水环境的重要影响区。然而,非点源磷污染的大量研究结果局限在地块尺度,而在主要类型支沟和小流域尺度上的研究结果较少。而地块尺度的磷迁移受空间异质性的影响,在宏观评估中应用时需要对通量作尺度拓展,导致评估的基础数据科学性不足,而支沟和小流域是包含空间异质性的景观单元,在宏观评估中已考虑空间异质性,其观测结果可作为宏观评估的基础。本研究选取紫色丘陵区典型土地利用支沟和小流域,开展次降雨事件的产流、产沙和磷素迁移过程的定位监测,研究主要土地利用类型对小流域磷负荷的贡献和影响,揭示紫色土典型小流域非点源磷污染的来源、输移过程与通量及其对水环境的影响。主要研究结果与结论如下: (1)降雨产流特征取决于土地利用与植被覆盖,居民点支沟在降雨量4mm即可产流,而林地与坡耕地支沟的产流的临界降雨量为20mm左右。居民点支沟的降雨径流响应迅速,受不透水地面的地表径流过程主导;林地与坡耕地支沟产流延迟,是植被拦截降雨,土壤入渗增强所致,前期径流过程受地表径流主导,后期受壤中流过程主导。暴雨和大暴雨情况下径流量和泥沙量大,泥沙流失主要集中在径流过程前期。集镇-农林小流域表现出与居民点支沟相似的径流过程,降雨径流响应快,呈现“暴涨暴落”的特点,而农林复合小流域的径流呈现显著“滞后效应”,退水时间长。 (2)居民点和林地支沟随径流迁移的总磷(Total P-TP)、颗粒态磷(Particulate P-PP) 浓度在径流过程中迅速达到峰值后陡然下降,坡耕地支沟流失的总磷(TP)、颗粒态磷(PP)浓度呈多峰状变化。居民点支沟径流的可溶性磷(Dissolved P-DP)浓度随径流量增大而减少,林地支沟产流过程中径流的可溶性磷(DP)浓度逐渐增加,坡耕地可溶性磷(DP)、磷酸盐( PO43--P) 浓度较低且波动较小。居民点支沟在小雨、中雨、大雨和暴雨等几种雨型下的TP流失负荷分别为42.6、136.3、190.0、1245.6g/hm2,平均负荷为403.6 g/hm2,林地支沟在中雨、大雨和暴雨等雨型下的TP流失负荷分别为3.5、3.9、90.6 g/hm2,平均负荷为32.7g/hm2,坡耕地支沟在中雨、大雨和暴雨等雨型下的TP流失负荷分别为6.6、10.2、210.6g/hm2,平均负荷为75.8 g/hm2,降雨量越大,磷流失量越高。且暴雨条件下的TP流失量最高。在典型降雨条件下,居民点支沟的磷流失负荷远高于坡耕地和林地,表明居民点是紫色丘陵区非点源磷污染控制的关键源区。 (3)支沟、小流域磷的迁移主要集中在雨季,特别是6-9月。居民点支沟的TP年输出负荷为9934.5 g/hm2.a;林地支沟的TP年输出负荷为309.8 g/hm2.a;坡耕地支沟的TP年输出负荷为1386.9 g/hm2.a,居民点的磷年流失负荷是林地和坡耕地的28倍与7倍。集镇-农林小流域的TP年流失负荷为2337.2g/hm2.a;农林复合小流域的TP流失年负荷为690.1 g/hm2.a。 (4)集镇-农林小流域与居民点支沟的磷迁移过程特征相似,在小雨型条件下以DP迁移,而在中雨、大雨和暴雨情况下,均以PP迁移为主,而降雨量越大,径流中PP占TP比例越高。农林复合小流域磷迁移主要以PP迁移为主,但后期DP比例上升,壤中流主导退水过程,且降雨量越大,DP占TP比例越大。集镇-农林小流域的TP、DP、PP输出负荷显著高于农林复合小流域,说明上游居民点支沟对集镇-农林小流域的磷输出影响较大,而农林复合系统可能有利于缓解非点源磷污染献。 (5)2014年集镇-农林小流域各土地利用支沟对小流域磷流失通量的贡献为,小流域中占地面积为3.2hm2的居民区TP流失总量为47685.6g/a,坡耕地土地面积为18.77 hm2,TP总流失量为24645.2 g/a,林地在小流域土地面积为12.43 hm2,TP总流失量为3850.8 g/a。集镇-农林小流域径流中TP流失量为81802 g/a。居民点以仅14%的土地面积贡献了57%的磷负荷,坡耕地以50%的土地面积贡献了34%的磷负荷,林地以36%的土地面积贡献了5%的磷负荷。结果发现,集镇-农林小流域中,不同土地利用类型对小流域磷贡献率表现为居民点>坡耕地>林地,其中居民点和坡耕地是小流域非点源磷污染的主要来源。 (6)小流域尺度的降雨径流和磷素迁移特征与支沟尺度有相似之处,由于支沟涵盖了土壤、地貌、植被覆盖等空间异质性,是径流、泥沙和非点源污染过程观测的重要尺度,既能区分污染源,也能在一定程度上反映小流域特点。因此,支沟尺度的观测研究结果可以在一定程度上作为流域或区域尺度的非点源磷污染评估的基础,因此未来应加强支沟尺度的综合观测。
Other AbstractNon-point source phosphorus pollution has become an important external source for fresh water eutrophication. Phosphorus is one of the major nutrient elements necessary for plant growth and development, whereas, also one of the major limiting factors for agricultural productivity. Surplus application of phosphorus fertilizer to meet with the need for agricultural production results in excessive accumulation in soil. Meanwhile, untreated sewage from small towns and villages also accumulates in drainage ditches and contains large amounts of phosphorus. Those accumulated P in soils and ditches will diffuse with runoff and sediment induced by rainfall and to conflux into aquatic ecosystems leading to increasing phosphorus loading. Hilly area of purple soil lies at the forefront of the upper reaches of the Yangtze River. It is an important influencing area for water environment of Yangtze River and the Three Gorges reservoir. Non-point sources phosphorus pollution from hilly area of purple soil may cause crucial impacts on water environment of both Three Gorges Reservoir and throughout Yangtze River. However, whereas great deal of researches on non-point source phosphorus pollution limits in plot scales, very few researches is invloled in sub-catchment in different land use and watershed scales. Phosphorus loss fluxes via plot-scales will be limited for use when macro-scale or watershed scale assessment is needed due to spatial heterogeneity. Because sub-ctachment or small watershed is a landscape which contains spatial heterogeneity, sub-catchment based catchment scale monitoring will provide basic scientific data for watershed and regional assessment. Therefore, processes and loss fluxes monitoring of rainfall-induced runoff, sediment yield and phosphorus transport from several sub-catctments in different land uses and some typical small watersheds will be conducted to learn characteristics of non-point-source phosphorus loss and loading to water environment. The results and conclusions were listed as follows: (1)In the residential sub-catchment, runoff started while rainfall reached 4mm, whereas, runoff occurred if rainfall is higher than 20 mm in the forestland and hillslope cropland sub-catchment, respectively. Runoff responded to rainfall rapidly at almost the same peak in the residence sub-catchment, whereas, runoff retard in the forestland and cropland sub-catchments.When heavy and stormy rain happened, runoff and sediment yield responded to rainfall quickly, and concentrated on the early stage of runoff process. The runoff process of residential-agricultural-foresry catchment showed similartrend to residential sub-catchment,presented "sharp rises and sharp down ",agroforestry catchment runoff showed a significant "lag effect".Agroforestry watershed runoff showed a significant "lag effect", depletion time is long. This is because Agroforestry system can significantly improve the structure of soil, interspersed with a tree root system to increase infiltration, making the subsurface flow increases. (2)The concentration of total P (TP) and particulate phosphorus (PP) of runoff water from the residence and forestland sub-catchment reached peak quickly and decreased sharply, whereas, TP and PP of runoff water from the hill slope cropland turned into a process with multi-peaks. The concentration of dissolved P (DP) of runoff water from the residence sub-catchment decreased when runoff discharge increased. DP of runoff water from the forestland sub-catchment increased during the runoff process. DP and phosphate (PO43--P) concentrations of runoff from farmland were relative low. The TP loss fluxes under small, medium, heavy and storm rain conditions from the residence sub-catchment were 42.6, 136.3, 190.0 and 1245.6 g/ hm2with average loss fluxes being 403.6 g/ hm2in the typical rain events; while, the TP loss fluxes under medium, heavy and storm rain conditions from forestland and hill slope cropland were 3.5, 3.9, 90.6g/ hm2(average 32.7 g/ hm2) and 6.6, 10.2, 210.6g/ hm2(average 75.8 g/hm2), respectively. The phosphorus loss flux from the residence sub-catchment was significantly higher than that from the hill slope cropland and forestland sub-catchment under various rain-type conditions. Therefore, residence area is the “hotspot” for non-point source phosphorus pollution control in the hilly area of purple soil. (3) In seasonal variation perspective ofphosphorus migration, sub-catchment, catchment phosphorus migration mainly distributed in the rainy season, especially from June to September. The phosphorus’s main migration pattern is TP in runoff. The runoff TP loss fluxes is 9934.5 g/hm2·a in Residential sub-catchment; The forestland sub-catchment TP loss fluxes is 309.8 g/hm2·a; The TP loss fluxes of cropland sub-catchment is 1386.9 g/hm2·a.The total phosphorus years loss fluxes is 28 times and 7 times than the forestland and cropland. The TP loss fluxes of residential-agricultural-foresry catchment n the annual is 2337.2 g/hm2·a, and the agroforestry catchment is 690.1 g/hm2·a. (4)The process of phosphorus loss in residential-agricultural-foresry catchmentis similar to the residential sub-catchment, DP was the main form of P lost in the light rain conditions.In moderate, heavy and storm conditions, PP was the main form of P lost. The concentration of PP of runoff water from the residential-agricultural-foresry catchmentdecreased when runoff discharge increased. DP of runoff water from the agroforestry catchmentincreased during the runoff process. Subsurface runoff dominant depletion process, and the greater the rainfall, DP accounted for the greater proportion of TP. The TP, DP, PP loss fluxes of residential-agricultural-foresry catchmentwas significantly higher than agroforestry catchment, indicating that the residential sub-catchment has a greater impact on residential-agricultural-foresry catchment, and agroforestry systems have outstanding contributions to alleviate non-point source phosphorus pollution. (5)The contribution of phosphorus loss flux from different land use sub-catchment in residential-agricultural-foresry catchment during 2014 :The residential sub-catchment a small basin covers an area of ??total loss of 3.2 hm2 residential TP is 47685.6g / a, cropland sub-catchment of the land area is arable 18.77 hm2, TP total loss amount of 24645.2 g / a, in catchment forest land area of ??12.43 hm2, TP total loss amount of 3850.8 g / a. Residential-agricultural-foresry catchment runoff TP loss amount was 81802 g / a. Residential with only 14% of the land area contributed 57% of the phosphorus load, slope land with 50% of the land area contributed 34% of the phosphorus load, 36% of the forest land area contributed 5% of the phosphorus load. It was found that the town - small watershed in agriculture, forestry, land use different types of phosphorus contribution of small watershed showed Residential> sloping land> forest, where settlements and sloping land is the main source of small watershed non-point source phosphorus pollution. (6) In this study, regardless of the rainfall-runoff process or phosphorus loss process, whatever catchment and sub-catchment scales have similarities.As sub-catchment areas covered soil, topography, vegetation and other spatial heterogeneity, it is a important scale to observe runoff, sediment and non-point source pollution process.It also can reflect the characteristics of small watershed to some extent. Therefore, the results of sub-catchment-scale observational studies can provide a more reliable basis as non-point source phosphorus pollution assessment than plot scale, so it should be to strengthen the observation of sub- catchment scale in the future.
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7828
Collection山地表生过程与生态调控重点实验室
Recommended Citation
GB/T 7714
沈茜. 紫色丘陵区典型小流域磷素迁移特征[D]. 北京. 中国科学院研究生院,2014.
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