黄土高原降雨驱动下流域碳输移特征及其碳流失评估：以羊圈沟坝系流域为例

Characteristics of Carbon Transportation Under Rainfall Events and Associated Carbon Loss Evaluation in Loess Plateau,China:A Case Study of Yangjuangou Dam Watershed

通过对黄土高原典型坝系流域雨季碳沉降与径流碳输移过程的研究,探讨降雨径流过程对流域碳流失的驱动机制,并进一步评估流域碳侵蚀通量.结果表明,羊圈沟坝系流域湿、干季碳沉降月通量为3.33 kg·hm^(-2)、2.18 kg·hm^(-2),干湿季碳沉降存在一定变化且对流域碳输出贡献较小.流域8月碳输出量为944.89 kg·km^(-2),其中DOC、DIC输出量分别占55.39%、44.61%;9月碳输出量为300.29 kg·km^(-2),DOC、DIC输出量分别占23.03%、79.97%,不同降雨强度径流的碳流失量不同,总体溶解性无机碳输出比重较大.羊圈沟小雨强降雨事件中径流溶解性碳输出量为156.98 kg·km^(-2),中等雨强降雨事件中径流碳输出284.60 kg·km^(-2);该流域雨季月均碳流失模数为1.89 kg·(km^2·mon)^(-1),经评估得出研究区域年碳流失模数为2.70kg·(km^2·a)^(-1).

In this study,by monitoring carbon transportation and its rainfall-runoff process during the rainy season in Loess Plateau＇s Yangjuangou dam watershed,we analyzed changes in carbon transportation driven by rainfall and further evaluated the C loss flux for the dam watershed. Results showed that the monthly C wet deposition flux for the wet and dry seasons were 3. 33 kg·hm^（-2）and 2. 18 kg·hm^（-2）,respectively,which were only small contributions to C transportation for the watershed. C transportation under the rainfallrunoff process in this watershed can reach 944. 89 kg·km^（-2）and 300. 29 kg·km^（-2）in August and September,respectively. Different intensities of rainfall runoff lead to different C loss processes,wherein dissolved inorganic carbon（ DIC） is the main C form. Under small rainfall events,the output of dissolved total carbon（ DTC） in this watershed was 156. 98 kg·km^（-2）; and the output of moderate rainfall events was 284. 60 kg·km^（-2）. Finally,we determined that the C loss modulus of the Yangjuangou watershed was 1. 89kg·（ km^2·mon）^（-1）in the rainy season,thus the C loss modulus for the study area could reach 2. 70 kg·（ km^2·a）^（-1）.