Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China.
Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; Puding Karst Ecosystem Observation and Research Station, Chinese Academy of Sciences, Puding 562100, China.
Sci Total Environ. 2020 Apr 20;714:136833. doi: 10.1016/j.scitotenv.2020.136833. Epub 2020 Jan 21.
Hydrochemical behavior and dissolved carbon dynamics are highly-sensitive to hydrological variations in the monsoon-influenced karstic critical zone which has high chemical weathering rates and experiences strong anthropogenic impact. Continuous high-frequency monitoring in the spring outlet of a karstic catchment in Southwestern China revealed that most hydrochemical variables changed distinctively in response to hydrologic variations, influenced by mixing of different sources and miscellaneous biogeochemical processes. Na, K and SO varied significantly with hydrology, showing weak chemostatic behavior controlled by dilution. The flushing effect and random behavior of NO and Cl likely reflect agricultural inputs from high throughflow. Soil CO in infiltrated water supports carbonate weathering, enabling DIC (dissolved inorganic carbon) and weathering products (e.g., Ca and Mg) to maintain chemostatic behavior. Biogenic DIC exhibited a stronger chemostatic response than carbonate sources and was the foremost control in DIC behavior. Carbon exchange between DIC and DOC (dissolved organic carbon) did not significantly influence DIC concentration and δC due to very low DOC concentration. More DOC was exported by flushing from increasing discharge. Hysteretic analysis indicated that the transport processes were controlled by proximal sources mixing and diverse mobilization in various periods responding to rainstorms. NO and Cl presented different hysteresis behavior as sourced from agricultural activities. DOC increased on the hydrograph rising limb and was controlled by a transport-limited regime. However, the hysteresis behavior of most weathering products and DIC were regulated by a process-limited regime in the karstic critical zone. Overall, biogeochemical processes, hydrogeological properties, storm intensity/magnitude and the timing of storms (antecedent conditions) are main factors influencing the response of hydrochemical variables and dissolved carbon to storm events.
水文变化对季风影响下的喀斯特关键带的水化学行为和溶解碳动态具有高度敏感性，该关键带具有高化学风化率和强烈的人为影响。在中国西南部的一个喀斯特流域的泉水出口进行的连续高频监测表明，大多数水化学变量因混合不同来源和多种生物地球化学过程而明显响应水文变化。Na、K 和 SO 的变化与水文学密切相关，表现出由稀释控制的弱化学稳定行为。NO 和 Cl 的冲洗效应和随机行为可能反映了高流量下的农业输入。渗入水中的土壤 CO 支持碳酸盐风化，使 DIC（溶解无机碳）和风化产物（如 Ca 和 Mg）保持化学稳定行为。生物成因 DIC 表现出比碳酸盐源更强的化学稳定响应，是 DIC 行为的主要控制因素。由于 DOC 浓度非常低，DIC 与 DOC（溶解有机碳）之间的碳交换对 DIC 浓度和 δC 没有显著影响。DOC 浓度增加导致更多的 DOC 通过流量增加从出口中排出。滞后分析表明，运输过程受近端源混合和不同时期对暴雨的多种迁移控制。NO 和 Cl 由于源自农业活动，呈现出不同的滞后行为。DOC 在水文图上升支增加，受输运限制控制。然而，在喀斯特关键带中，大多数风化产物和 DIC 的滞后行为受过程限制控制。总体而言，生物地球化学过程、水文地质特性、风暴强度/幅度以及风暴的时间（前序条件）是影响水化学变量和溶解碳对风暴事件响应的主要因素。
