Carbon wet deposition and river carbon output in river basins are important components of global carbon cycle. The assessment of both properties is of great significance for regional carbon budget. However, research on these topics in high-latitude permafrost regions in China is still lacking. We conducted dynamic monitoring of carbon wet deposition and carbon output in the river from May 28th to October 30th, 2022, in Laoyeling watershed, a typical forested watershed in the Da Xing'an Mountains permafrost region. We analyzed the variations of carbon component concentrations and fluxes in precipitation and river water, and estimated the contribution of carbon wet deposition to carbon output in the watershed. The results showed that wet deposition fluxes of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and total dissolved carbon (TDC) in the Laoyeling watershed were 1354.86, 684.59, and 2039.45 kg·km-2, respectively. The fluxes of DOC, DIC, TDC, particulate organic carbon (POC), particulate inorganic carbon (PIC), and total carbon (TC) in the river were 601.75, 1977.30, 2579.05, 125.13, 21.99, and 2726.17 kg·km-2, respectively. The contribution of TDC wet deposition to the river TDC output was 9941.89 kg, accounting for 17.6% of total output. The DIC concentration in the river showed significant seasonal differences, with increased runoff resulting from precipitation leading to a decrease in DIC concentration in the river and showing a clear dilution effect, while the concentrations of DOC, POC, and PIC increased, mainly due to erosion effect. In conclusion, carbon wet deposition flux in the Laoyeling watershed was mainly determined by precipitation, and its contribution to river carbon output was relatively small compared to other factor. Runoff was the dominant factor affecting river carbon output. The results would provide important insights into carbon cycling and carbon budget balance in permafrost regions under climate change.
流域碳湿沉降与河流碳输出是全球碳循环的重要组成部分,对区域碳收支评估具有重要意义,然而在我国高纬度多年冻土区的相关研究仍然缺乏。本研究以大兴安岭多年冻土区典型森林流域——老爷岭流域为对象,在2022年5月28日—10月30日通过对流域内碳湿沉降过程及河流碳输出过程的动态监测,分析了降水和河流中各碳组分浓度与通量的变化特征及影响因素,并估算了流域内碳湿沉降对河流碳输出的贡献。结果表明: 观测期内,老爷岭流域溶解有机碳(DOC)、溶解无机碳(DIC)和总溶解碳(TDC)湿沉降通量分别为1354.86、684.59和2039.45 kg·km-2;河流中DOC、DIC、TDC的输出通量分别为601.75、1977.30、2579.05 kg·km-2,颗粒有机碳(POC)、颗粒无机碳(PIC)、总碳(TC)的输出通量分别为125.13、21.99、2726.17 kg·km-2;流域内TDC湿沉降对河流TDC输出的贡献量为9941.89 kg,相对贡献率为17.6%;河流中DIC浓度表现出显著的季节性差异,降水引起径流量的增加使河流中DIC浓度降低并表现出明显的稀释效应,而DOC、POC、PIC的浓度有所增加,主要表现出冲刷效应。综上,老爷岭流域的碳湿沉降通量主要由降水量决定,碳湿沉降对河流碳输出的贡献较小,径流量是影响河流碳输出的主导因素。本研究结果对理解气候变化影响下多年冻土区流域碳循环过程及碳收支平衡具有重要意义。.
Keywords: carbon wet deposition; permafrost; river carbon component; river carbon output; watershed carbon cycle.