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滇池东岸风化壳（土壤）同位素分布与迁移研究
【作者】 蔡青；
【导师】 刘星；
【作者基本信息】 昆明理工大学 ， 地球化学， 2015， 硕士
【摘要】 长期以来,风化壳(土壤)的侵蚀研究都是以定性方式为主,定量研究一直是个难题。现在,放射性同位素示踪技术是一种研究风化壳(土壤)侵蚀的新方法。该方法不但可靠性比较高,且省时省力,是进行流域尺度范围研究的有效手段。本文应用放射性同位素137Cs定年方法,结合土壤中的总磷、总氮、有机碳的含量测试,对云南省昆明市滇池流域东岸的松茂水库区域、宝象河小流域的风化壳(土壤)近50a的侵蚀速率进行研究。得出以下成果：1、放射性同位素137Cs的含量与风化壳(土壤)类型有关。松茂水库区域依据不同土壤类型中的137Cs的平均含量递增的顺序进行排序：撂荒地6.73 bq/m2<林地83.38 bq/m2<河滩地290.40 bq/m2<草地332.99 bq/m2,撂荒地土壤中137Cs的平均含量最少,含量最多的是草地。宝象河小流域中依据不同土壤类型中的137Cs的平均含量递增的顺序进行排序：灌木地70.46 bq/m2<林地77.86bq/m2<草地84.17 bq/m2。灌木地土壤中137Cs的平均含量最少,含量最多的也是草地。总磷、总氮、有机碳的含量也与风化壳(土壤)类型有关,土壤侵蚀速率的会影响土壤中有机碳(TOC)、总氮(TN)、总磷(TP)的流失。松茂水库区域：TOC：撂荒地5.44%<草地8.955%<河滩地13.73%<林地14.71%；TN：撂荒地2.03%<林地2.07%<草地2.13%<河滩地3.16%；TP：林地0.85%<撂荒地0.87%<河滩地1.42%<草地1.58%。宝象河小流域：TOC：灌木地8.48%<林地9.8%<草地12.1%；TN：林地0.88%<灌木地1.16%<草地1.48%；TP：林地0.26%<灌木地0.33%<草地0.37%。松茂水库区域中TOC和TN含量最低的是撂荒地；TP含量草地最高,林地最低。宝象河小流域中TOC和TN含量最低的是灌木地和林地,草地最高；TP含量草地最高,林地最低。2、放射性同位素137Cs含量与风化壳(土壤)深度有关：随着深度的增加,137Cs的含量不断减少。同时,松茂水库区域和宝象河小流域均发生了土壤侵蚀。已知滇池盆地的137Cs背景值为906bq/m2,在松茂水库区域和宝象河小流域的各种土壤类型中,其137Cs含量均小于背景值,都发生了土壤侵蚀。3、风化壳(土壤)侵蚀速率与土壤类型有关。利用土壤侵蚀速率公式A(x)=Aref(1-eλx和计算得出各个小流域的土壤侵蚀速率,松茂水库区域和宝象河小流域的平均土壤侵蚀速率分别为：19.892 cm/a和19.962 cm/a,宝象河小流域的土壤侵蚀更加严重。松茂水库区域的平均土壤侵蚀速率按递增的顺序排列为草地19.787 cm/a<河滩地19.836 cm/a<林地19.948 cm/a<撂荒地19.997 cm/a；宝象河小流域平均土壤侵蚀速率按从小到大的顺序依次排列为草地19.958 cm/a<林地19.961 cm/a<灌木地19.966 cm/a。4、风化壳(土壤)侵蚀速率与土壤中有机碳(TOC)、总氮(TN)、总磷(TP)的含量呈负相关,土壤侵蚀速率越快,TOC、TN、TP的含量就越少。
【Abstract】 It’s always a difficult problem to research the weathering crust (soil) erosion in a quantitative approach for along time. Now the technique of radioisotope tracer is a new method to research the weathering crust (soil) erosion. This is a effective way to research the basin. The method is not only high reliability, but also saving time and labor. In this paper, the dating principle about 137Cs is applied, and combining with the test data about the content of organic carbon, total nitrogen and total phosphorus. In this study, the weathering crust (soil) was in Baoxianghe small drainage area and Songmao reservoir area where the east bank of Dianchi basin to be researched. This article draws the following results:1. The content of the radioactive isotope 137Cs is related to the types of the weathering crust (soil). The average content of 137Cs in different soil types about Songmao reservoir is in increasing sequence:abandoned land 6.73 bq/m2< woodland 83.38 bq/m2< flood land 290.40 bq/m2< grassland 332.99 bq/m2. The least average content of 137Cs is abandoned land, the most one is grassland. The average content of 137Cs in different soil types about Baoxianghe small drainage area is in increasing sequence:shrub land 70.46 bq/m2< woodland 77.86bq/m2< grassland 84.17 bq/m2. The least average content of 137Cs is shrub land, the most one is grassland.The content of organic carbon (TOC) total nitrogen (TN) and total phosphorus (TP) also bear on the weathering crust (soil) type. The rate of soil erosion affects the loss of the TOC, TN and TP.Songmao reservoir: TOC:abandoned land 5.44%< grassland 8.955%< flood land 13.73%< woodland 14.71%; TN:abandoned land 2.03%< woodland 2.07%< grassland 2.13%< flood land 3.16%: TP:woodland 0.85%< abandoned land 0.87%< flood land 1.42%< grassland 1.58%。Baoxianghe small drainage area: TOC:shrub land 8.48%< woodland 9.8%< grassland 12.1%; TN:woodland 0.88%< shrub land 1.16%< grassland 1.48%; TP:woodland 0.26%< shrub land 0.33%< grassland 0.37%.The lowest content of TOC and TN is abandoned land in Songmao reservoir. The highest one is grassland and the lowest one is woodland about TP. The lowest content of TOC and TN is shrub land; and the highest one is grassland in Baoxianghe small drainage area. The highest one is grassland and the lowest one is woodland about TP.2. The content of the radioactive isotope 137Cs related to the depth of the weathering crust (soil):with the increasing of depth, the content of 137Cs decreased constantly.At the same time, the soil erosion all occurred in Songmao reservoir area and Baoxianghe small drainage area. The reference of 137Cs is 906bq/m2 in Dianchi basin. The content of 137Cs which are kind of soil were less than the reference whatever Songmao reservoir area or Baoxianghe small drainage area. They all have undergone the soil erosion.3. The rate of weathering crust (soil) erosion bears on soil types. The formula "Ah=Aref(1-eλh)" was used to count the rate of soil erosion in each small drainage areas. The average rate of soil erosion were 19.892 cm/a and 19.962 cm/a in Songmao reservoir area and Baoxianghe small drainage area. The soil erosion is more serious in Baoxianghe small drainage area.The rate of soil erosion in Songmao reservoir area is in increasing sequence: grassland 19.787 cm/a< flood land 19.836 cm/a< woodland 19.948 cm/a< abandoned land 19.997 cm/a. The rate of soil erosion in Baoxianghe small drainage area is in increasing sequence:grassland 19.958 cm/a< woodland 19.961 cm/a< shrub land 19.966 cm/a.4. It was positively related that the rate of soil erosion with the content of organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in weathering crust (soil). The faster the rate of soil erosion is, the less the content of TOC, TN and TP.