土地利用变化对喀斯特水体溶解无机碳、总氮和总磷输出的影响--以贵州普定沙湾模拟试验场为例

Effects of Land Use Change on Dissolved Inorganic Carbon,Total Nitrogen and Total Phosphorus Export to Karst Groundwater:A Case Study from the Shawan Simulation Test Site,Puding,Guizhou

耦联水生光合作用的碳酸盐岩风化碳汇是全球碳循环研究的关键问题,生物碳泵效应不仅能够稳定碳酸盐风化碳汇,也有利于改善水环境,而过量输入氮、磷会导致水环境变差。土地利用变化作为全球变化重要内容之一,对流域碳氮磷的输出具有重要影响,但关于土地利用变化对喀斯特水体溶解无机碳、总氮和总磷输出影响的研究有待进一步加强。本研究以贵州普定沙湾喀斯特试验场为研究对象,以研究土地利用变化对水文、水化学、溶解无机碳汇通量、总氮通量和总磷通量的影响。结果表明,流量、径流深、土壤CO_(2)浓度、pCO_(2)、HCO_(3)^(-)浓度和电导率呈现出夏秋季节高、春冬季节低的变化特征,与pH变化相反。样地间,土壤CO_(2)浓度、pCO_(2)、HCO_(3)^(-)浓度和电导率表现为草地>灌丛地>农耕地>裸土地>裸岩地,与pH变化相反。参与岩溶作用的土壤CO_(2)是造成水化学变化的主要原因。溶解无机碳汇通量和总氮通量呈现出夏秋季节高、春冬季节低的变化特征,总磷通量秋季最高、春季最低。样地间,草地溶解无机碳汇通量最大,HCO_(3)^(-)浓度是决定溶解无机碳汇通量大小的主导因素。有植被覆盖的土地利用方式的总氮、总磷浓度及其通量明显低于无植被生长的类型,总氮通量灌丛地最小,总氮浓度是决定总氮通量大小的主导因素,总磷通量草地最小,而流量是决定总磷通量大小的主导因素。综上,我们认为可以通过调整土地利用方式来达到增加岩溶碳汇和改善水环境双赢的目标。

Carbonate weathering coupled with aquatic photosynthesis(biological carbon pump-BCP)on the continents is a key issue in the study of global carbon cycle.The BCP can not only stabilize carbonate weathering-related sinks,but also improve water environment.The excessive import of nitrogen and phosphorus will lead to the deterioration of water environment.Land use change is one of the important contents of global change,which has an important impact on the output of carbon,nitrogen and phosphorus.However,the relationship between land use change and dissolved inorganic carbon,total nitrogen and total phosphorus export to karst groundwater needs further investigation.In this study,the Shawan Karst Test Site in Puding,Guizhou Province,was taken as the research object to study the effects of land use change on hydrology,hydrochemistry,dissolved inorganic carbon sink flux,total nitrogen flux and total phosphorus flux.The results showed that the discharge(Q),runoff depth(RD),soil CO_(2) concentration,pCO_(2),HCO_(3)^(-) concentration and electrical conductivity(EC)are higher in summer and autumn and lower in spring and winter,which is opposite to the change of pH.Between sample plots,soil CO_(2) concentration,pCO_(2),HCO_(3)^(-) concentration and EC showed grassland>shrub land>agricultural land>bare soil land>bare rock land,which is opposite to the change of pH.The main cause of hydrochemical change is soil CO_(2) which is involved in karstification.Dissolved inorganic carbon sink flux and total nitrogen flux are higher in summer and autumn and lower in spring and winter.Total phosphorus flux is the highest in autumn and the lowest in spring.Between sample plots,dissolved inorganic carbon sink flux of grassland is the largest,and the HCO_(3)^(-) concentration is the dominating factor of dissolved inorganic carbon sink flux.The concentrations and fluxes of TN and TP in land use with vegetation cover were significantly lower than those without vegetation.The total nitrogen flux of shrub land is the smallest,and the total nitrogen concentration is the dominating factor of total nitrogen flux.The total phosphorus flux of grassland is the smallest,and the discharge is the dominating factor of total phosphorus flux.To sum up,we think that we can achieve the win-win goal of increasing carbonate weathering-related sink and improving water environment by adjusting land use.