三岔河流域水文特征与化学风化碳汇效应

在喀斯特地区的流域产汇流过程中,由于富含碳酸的水体对可溶岩的溶蚀作用,导致河流断面输出大量溶解无机碳(DIC),反映了流域化学风化消耗大气CO2的强度,与流域水文过程密切相关。为了正确估算流域水文过程中化学径流及其碳汇效应,解析水文特征对流域地表过程中碳的生物地球化学行为的影响规律,以喀斯特地貌广布的三岔河流域三个水文站断面为例,研究了河源区河流水文特征与碳汇效应。结果表明:处于亚热带湿热环境下的喀斯特流域在观测水文年内,碳汇强度远大于非喀斯特的花岗岩流域且具有显著的季节变化,绝大部分的碳汇发生在高温多雨的6-11月。相关分析表明,流域碳汇强度与流域气温、降水和径流量呈显著的正相关关系;流域碳汇强度与河流总溶解固体物(TDS)浓度、DIC浓度呈显著的负相关关系。丰水期径流对河流TDS和DIC有明显的稀释效应。流域碳汇强度主要决定于河流TDS和DIC输出载荷而非河流TDS和DIC的浓度,与流域水文特征密切相关。

Hydrological characteristics and the atmospheric carbon sink in the chemical weathering processes of the Sanchahe watershed

In a karstic drainage basin,the fluxes of the riverine dissolved inorganic carbon (DIC)implied the atmospheric CO₂ consumption in the chemical weathering processes because of carbonate karst dissolution for the carbonic acid water closely related to the hydrological processes.In order to calculate the atmospheric carbon sink(ACS)on the riverine chemical runoff of the weathering processes and to understand the effects of the hydrologic processes on the carbon biogeochemical behaviors in the land surface processes, by the correlation analysis on the hydrological characteristics and its ACS,an investigation was carried out with a case study of the three hydrological cross-sections of the Sanchahe Watershed source area in which the karst landforms were widely developed.The results revealed that:(1)the intensity of annual atmospheric carbon sinks in chemical weathering processes of the Sanchahe Watershed was far greater than those of the non-karst granite basins because of the hot-humid environment of the subtropical karst basin during the studied hydrological year,in which the greatest part of the flux of the ACS occurred from June to November of the high-temperature and rainy monsoon with striking seasonal variation;(2) The correlation analysis demonstrated that there were distinct positive correlations between the basin ACS strength and basin temperature,precipitation,and runoff,while there was striking negative correlation between the basin ACS strength and riverine total dissolved solids concentration(TDS);(3)The variation of the DIC concentration indicated a significant dilution effect because of the high flow in the humid runoff period.The watershed ACS strength,which was closely related to the hydrological characteristics of a watershed, depended mainly on the TDS and DIC output loads instead of their concentrations.