重庆南川岩溶区不同土地利用类型下碳运移特征及其影响因素

发布时间：2018-01-12 23:29

本文关键词：重庆南川岩溶区不同土地利用类型下碳运移特征及其影响因素　出处：《西南大学》2016年博士论文　论文类型：学位论文

【摘要】：随着全球气候变暖以及极端气候事件的频频发生,碳循环逐渐受到人们的重视。碳酸盐岩作为全球最大的碳库,其对全球碳循环的重要性不言而喻。碳酸盐岩通过岩溶作用消耗大气或土壤CO_2,对大气起到减源增汇的作用。受上覆植被类型、土壤理化性质、耕作方式以及HNO3和H2SO4等强酸影响,不同土地利用类型下的土壤CO_2浓度及岩溶碳循环具有明显差异。为此,弄清岩溶区不同土地利用类型下碳运移特征及其影响因素,有助于准确估算岩溶碳汇效应,并为改善土地利用方式以增强岩溶碳汇效应提供理论依据。本文以重庆市南川区柏树湾泉域、兰花沟泉域和后沟泉域为例,通过监测岩溶泉水化学性质,探讨不同土地利用类型下岩溶碳循环的差异。另外,本文通过研究3个泉域上覆土壤理化性质、植被类型以及土壤CO_2,并运用稳定碳同位素对碳在各圈层的运移进行示踪,揭示不同土地利用类型下碳运移特征及其影响因素的差异。3个岩溶泉中的阳离子均以Ca~(2+)为主,但阴离子组成具有明显差异。柏树湾泉域受人类活动干扰小,阴离子主要以HCO3-为主,泉水为HCO3-Ca型。兰花沟泉域和后沟泉域受氮肥及煤铁残渣等因素影响,NO3-和SO42-的含量增加,泉水属于HCO3·SO4-Ca型。通过水化学性质计算出了3个泉域的岩溶碳汇效应。在不同土地利用类型下,岩溶作用对土壤CO_2的净消耗量具有明显差异,柏树湾泉域岩溶作用对土壤CO_2的净消耗量最大,后沟泉域最小,兰花沟泉域居中。在不同季节,岩溶作用对土壤CO_2的净消耗量也会发生变化。其中柏树湾泉域土壤CO_2净消耗量由旱季的2.17 mmol·L-1增加到雨季的2.31 mmol·L-1;兰花沟泉域和后沟泉域土壤CO_2的净消耗量则分别由旱季的0.58 mmol·L-1、-0.15 mmol·L-1下降到雨季的0.27mmol·L-1、-0.27mmol·L-1。3个泉域土壤CO_2浓度具有明显的季节变化特征,即雨季土壤CO_2浓度明显大于旱季。兰花沟泉域和后沟泉域土壤CO_2浓度与土壤温度呈正相关关系(0.05P0.1),雨季土壤温度升高促进了土壤CO_2的产生,但土-气之间的CO_2通量也随温度升高而增加,导致兰花沟和后沟泉域岩溶作用对土壤CO_2的净消耗量在雨季并没有增加。不同土地利用类型下土壤CO_2浓度也存在明显差异:无论雨季还是旱季,柏树湾泉域土壤CO_2浓度均大于兰花沟和后沟泉域;旱季兰花沟泉域土壤CO_2浓度小于后沟泉域,而雨季兰花沟泉域20cm和50cm处土壤CO_2浓度大于后沟泉域。在土壤CO_2浓度的垂向变化上,柏树湾泉域土壤CO_2浓度在雨季和旱季均出现双向梯度;兰花沟泉域土壤较薄,土壤CO_2浓度随土壤深度的增加而增加;后沟泉域土壤CO_2浓度在旱季表现为双向梯度,在雨季则随土壤深度增加而增加。上覆植被以及土壤性质是导致不同土地利用类型下土壤CO_2浓度变化特征出现差异的主要原因。柏树湾泉岩溶作用对土壤CO_2的净消耗量最大且雨季大于旱季,与土壤CO_2浓度的变化一致。但兰花沟和后沟CO_2净消耗量却与土壤CO_2浓度变化趋势相反,并且无论兰花沟泉域土壤CO_2浓度是否大于后沟泉域,其土下岩溶作用对土壤CO_2的净消耗量均大于后沟泉域。这说明土壤CO_2浓度并不是影响兰花沟和后沟泉域土下岩溶作用的主要因素。在不同的土地利用类型下,受土壤性质及人类活动等影响,碳运移特征及其影响因素也会出现差异。室内模拟实验中设计了6个不同的处理,以分析不同因素对土下岩溶作用及碳运移特征的影响。实验结果表明,H2SO4含量增加导致土下岩溶作用增强,但岩溶作用对CO_2的净消耗量并没有随之增加。并且当H2SO4溶蚀碳酸盐岩产生CO_2没有再次参与岩溶作用时,岩溶作用对CO_2的净消耗量随H2SO4含量的增加而减少;降水对下渗水的水化学性质产生了明显的稀释效应,即降水量增加导致下渗水中各离子浓度减小;土壤厚度既可以通过土壤CO_2又可以通过土壤中H2SO4含量间接影响土下岩溶作用强度及碳在各圈层中的运移方向。通过监测土壤CO_2的δ~(13)C以及泉水δ~(13)CDIC发现,雨季植物残体以DOC的形式进入底部土壤也是引起底部土壤CO_2δ~(13)C变化的重要原因,因此仅仅依靠土壤CO_2的δ~(13)C并不能判断HNO3和H2SO4溶蚀碳酸盐岩后产生的CO_2是否返回到土壤中。兰花沟泉和后沟泉水化学性质及泉水δ~(13)CDIC显示,HNO3和H2SO4溶蚀碳酸盐岩后产生的CO_2并没有全部再次对碳酸盐岩进行溶蚀。在降水减少的时期,土壤CO_2因水岩接触时间增加,其对碳酸盐岩溶蚀量的贡献增加。但HNO3和H2SO4溶蚀碳酸盐岩后产生的CO_2对碳酸盐岩的溶蚀作用也随之加强,这意味着更多来自碳酸盐岩的碳进入到水体中。另外,由于表层土壤呈酸性,在土壤水下渗速率减慢时,更多的H+与HCO3-结合,较轻的碳从水体中脱离,从而导致岩溶泉水δ~(13)CDIC偏重。以上作用共同控制泉水δ~(13)CDIC,导致泉水δ~(13)CDIC不能反映出岩溶碳汇效应的变化。以上结果表明,受上覆植被类型、土壤性质及人类活动影响,本研究中林地岩溶作用对土壤CO_2的净消耗量主要受土壤CO_2浓度控制;而在农用地,岩溶作用对土壤CO_2的净消耗量主要受降水控制。另外,运用碳同位素技术估算岩溶碳汇效应时,HNO3和H2SO4溶蚀碳酸盐岩后产生的CO_2脱离水体可能会导致计算结果出现偏差。因此在研究岩溶碳汇效应时,需考虑此部分CO_2运移方向对其产生的影响。
[Abstract]:With the global climate warming and the frequent occurrence of extreme weather events, the carbon cycle has attracted more and more attention. Carbonate rocks as the world's largest carbon pool, its importance to the global carbon cycle. The role of Yan Rong self-evident carbonate consumption atmosphere or soil CO_2, reducing the source sink effect on gas. By over the vegetation types, soil physicochemical properties, tillage and HNO3 and H2SO4 acid, under different land use types on soil CO_2 concentration and Yan Rong carbon cycle has a significant difference. Therefore, clarify the different Yan Rong land use characteristics and influence factors of carbon migration type, contribute to the accurate estimation of the carbon sink effect and to improve the Yan Rong. Land use patterns to enhance the carbon sink effect and provide a theoretical basis for Yan Rong. In this paper, Nanchuan District of Chongqing cypress Bay springs, spring area and orchids ditch ditch spring area as an example, through the monitoring of Yan Rong Water chemical properties of different land use types of karst carbon cycle difference. In addition, through the study of the 3 spring area of overlying soil physicochemical properties, vegetation types and soil CO_2, and the use of stable carbon isotope of carbon tracer migration in other spheres, reveal the different land use factors between karst.3 cation the spring migration characteristics and influence types of carbon were Ca~ (2+), but the anion composition has a significant difference. The cypress Bay spring area disturbed by human activities, the anion is dominated by HCO3-, HCO3-Ca. Spring orchids ditch spring area and gully spring area affected by nitrogen and iron and coal residue etc., increase the content of NO3- and SO42-, HCO3 and SO4-Ca belong to the spring type. The chemical properties of water through calculating the 3 spring area. The karst carbon sink effect under different land use types, karst measuring net consumption of soil CO_2 There are obvious differences, the cypress Cove karst effect net consumption of soil CO_2, after the ditch spring area minimum, orchid spring field ditch center. In different seasons, karst net consumption of soil CO_2 will change. The cypress Cove spring area soil CO_2 net consumption increased by 2.17 during the dry season mmol - L-1 2.31 mmol - L-1 to the rainy season; consumption ditch spring area soil CO_2 orchid spring ditch domain and dry season respectively by 0.58 mmol - L-1, -0.15 mmol L-1 0.27mmol L-1 down to the rainy season, with obvious variation -0.27mmol L-1.3 spring field soil CO_2 concentration that is the rainy season, the soil CO_2 concentration was significantly higher than the dry season. The orchid spring area and after the ditch ditch spring area soil CO_2 concentration was positively correlated with soil temperature (0.05P0.1), the relationship between the soil temperature promote the soil CO_2, but the CO_2 flux of soil air are increased with temperature increasing Plus, lead orchid ditch and ditch karst effect net consumption of soil CO_2 in the rainy season did not increase. Under different land use types of soil CO_2 concentration varied significantly: no matter in rainy season or dry season, cypress Bay spring area soil CO_2 concentration were higher than after the ditch ditch and orchid spring area; dry season orchid spring ditch the domain of soil CO_2 concentration is less than the channel after spring area, and the rainy season spring orchids ditch domain 20cm and 50cm soil CO_2 concentration is greater than the spring area. After the ditch to changes in soil CO_2 concentration in the vertical, the cypress Cove spring area soil CO_2 concentration showed bidirectional gradient in the rainy season and the dry season; orchid thin ditch spring area soil, increase the soil CO_2 concentration with soil depth increased; after the ditch spring field soil CO_2 concentration in dry season showed bidirectional gradient, in the rainy season increased with soil depth. The overlying vegetation and soil properties in different land use types of soil CO_2 The concentration variation of the main reasons for the differences. Cypress Bay spring karst net consumption of soil CO_2 maximum and wet season than in dry season, consistent with the change of CO_2 concentration in the soil. But after the ditch ditch and orchid net CO_2 consumption has the opposite trend with soil CO_2 concentration, and whether the orchid spring field ditch soil CO_2 concentration is after more than ditch spring area, the karst soil net consumption of soil CO_2 was greater than the ditch spring area. It indicated that the soil CO_2 concentration is not the main factor influencing the karst spring area and orchids ditch ditch under the soil. In different land use types, affected by soil properties and human activities so, characteristics and influence factors of carbon migration will be different. The experiment designed 6 different treatment of indoor simulation, in order to analyze the influence of different factors on soil under karstification and carbon migration characteristics. Experimental results show that the content of H2SO4 Increase the amount of lead to enhanced karst soil, but the karst net consumption of CO_2 volume was not increased. And when the dissolution of carbonate rocks H2SO4 CO_2 did not participate in the karst again, increasing karst net consumption of CO_2 with the content of H2SO4 decreased; water chemistry of precipitation produced under seepage the dilution effect is obvious, which leads to increased precipitation infiltration of each ion concentration in water decreased; soil thickness can by soil CO_2 can also be affected indirectly through the migration direction of karst soil and carbon intensity in all spheres of H2SO4 content in the soil. By monitoring soil CO_2 8 ~ (13) C and ~ Delta spring CDIC (13) found that the rainy season plant residues into the bottom of the soil in the form of DOC is caused by the bottom soil CO_2 8 ~ (13) C an important reason for change, therefore only rely on soil CO_2 8 ~ (13) C and HNO3 and H2SO can not judge 4 CO_2 after the dissolution of carbonate rocks is returned to the soil. The orchid spring and spring ditch ditch water chemical properties and ~ (13) CDIC Delta, HNO3 and H2SO4 CO_2 after the dissolution of carbonate rocks and carbonate rocks are not all again on the dissolution. The reducing precipitation period, soil CO_2 increased by water rock contact time, its contribution to the increase of the amount of carbonate dissolution. But the dissolution of HNO3 and H2SO4 CO_2 after the dissolution of carbonate rocks in carbonate rocks has been strengthened, which means more from carbonate carbon into the water. In addition, the surface soil is acidic, the soil water infiltration rate slow down, H+ and HCO3- more with the lighter carbon from the water, resulting in karst spring 8 ~ (13) CDIC on the above interaction control spring. 8 ~ (13) CDIC, ~ (13) Delta resulting in spring CDIC cannot reflect the karst carbon sink effect Change. The above results showed that the vegetation types, soil properties and human activities, the role of Forest karst in this study net consumption of soil CO_2 was mainly affected by soil CO_2 concentration control; while in farmland, karst net consumption of soil CO_2 was mainly affected by water control. In addition, the estimation of karst carbon sink the effect of using carbon isotope techniques, the production of HNO3 and H2SO4 CO_2 after the dissolution of carbonate rocks from the water may cause the deviation of calculation results. Therefore research on Karst carbon sink effect, need to consider the effect of this portion of the CO_2 on the migration direction of production.

【学位授予单位】：西南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S151.9

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