贵州阿哈湖喀斯特小流域DOC输出特征

河流不仅是陆地碳循环的通道,也是碳交换的重要场所,而小流域更被认为是陆地碳循环的热点。为探究人类活动影响下喀斯特小流域溶解性有机碳(DOC)输出特征,于2017年6月～2018年5月对阿哈湖3条主要入湖小流域游鱼河、白岩河、金钟河河水主要理化特征和DOC含量进行分析,并计算流域DOC输出通量。研究期间游鱼河、白岩河、金钟河DOC含量分别为4.78±2.11、5.61±2.27、7.40±2.51 mg/L,输出通量分别为2.71、2.91、3.82 t/(km~2. a)。结果表明:(1)阿哈湖小流域河水DOC含量时空变化特征明显,与降雨、流域土地利用类型密切相关,人类外源输入对DOC有显著影响;(2)对比不同河流DOC输出特征发现,小流域通常具有更高的DOC输出通量,特别是受城市输出影响的中小流域,其河流碳过程在碳循环中的贡献可能被低估。

Characteristics of Dissolved Organic Carbon Export ofA Karst Small Catchment in Guizhou Aha Lake

Abstract：River is the channel of the terrestrial carbon cycle and an important carbon exchange place, particularly, with the small watershed as a hotspot. In order to explore the characteristics of dissolved organic carbon (DOC) export in karst catchments under the effect of human activities, the water samples were collected in Youyu River, Baiyan River and Jinzhong River of Aha Lake. The main physical and chemical characteristics and DOC concentration were analyzed from December 2017 to February 2018, and then calculated the DOC export flux. The DOC concentration of Youyu River, Baiyan River and Jinzhong River were 4.78±2.11, 5.61±2.27, 7.40±2.51 mg/L， respectively, and the DOC flux were 2.71, 2.91, 3.82t/(km2. a). The result showed that the temporal and spatial variation of DOC concentration in the Aha Lake was obvious. The DOC concentration was related to the precipitation，land-use types and water quality indexs, and the human external input did significant impact on DOC. The small-size watershed usually possessed higher DOC export flux than that of large rivers, especially the rivers impacted by municipal wastewater. Thus, the role it played in the global carbon cycle could have been underestimated.