Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
Sci Total Environ. 2022 May 15;821:153296. doi: 10.1016/j.scitotenv.2022.153296. Epub 2022 Jan 21.
Rivers significantly contribute to the global carbon budget, but data limitations and uncertainty are hampered by CO quantification in the global rivers. Thus, this study estimated riverine pCO by employing the pH-alkalinity-temperature method, and dissolved inorganic (DIC), dissolved organic (DOC), particulate organic (POC) carbon, and their isotopes (δC) with Chlorophyll-a (Chl a) were measured in river water samples from 26 sampling sites for characterization and source identification in the Yangtze River system. The estimated pCO varies from (120 ppm) to (3400 ppm) with an average (1085 ppm) across the Yangtze River and pCO is almost three times oversaturated than the ambient air (380 ppm). The downstream sites pronounced elevated pCO than the upstream sites. The relationship of δC and pCO indicated that pCO control is seasonally independent. The significant correlations between DOC, POC, and pCO revealed that organic carbon influenced pCO in the river. The seasonal fluctuations of pCO were observed with an average of (762.23 ppm) and (1407.35 ppm) in winter and summer, respectively. δC showed that the metabolic process has a negligible influence on DIC, δC and pCO. δC values increased from -8.95‰ to -4.91‰ during summer, whereas winter increased from -19.76‰ to -1.97‰ suggesting that DIC derived from carbonate weathering, dissolution of atmospheric and soil CO. The δC (-30.43‰ to -24.05‰) and δC (-29.87‰ to -23.37‰) values confirmed that organic carbon mainly derived from the degradation of organic materials in soil. δC revealed that anthropogenic sewage discharge slightly modified DIC composition. Overall, this study provides new insight into recent seasonal fluctuations of the pCO, DOC, POC, DIC, δC, and their inputs. Thus, these variations and inputs of carbon transported by the Yangtze River could have a significant influence not only on the biogeochemical cycle and ecosystem process but also on the global carbon budget.
河流对全球碳预算有重大贡献，但由于全球河流 CO2 定量存在数据限制和不确定性，因此受到阻碍。因此，本研究采用 pH-碱度-温度法估算河流水体中的 pCO2，并测量了长江水系 26 个采样点的河水样品中的溶解无机碳（DIC）、溶解有机碳（DOC）、颗粒有机碳（POC）及其同位素（δC）和叶绿素-a（Chl a），以进行特征描述和来源识别。估算的 pCO2 范围为（120ppm）至（3400ppm），平均为（1085ppm），长江流域 pCO2 几乎是环境空气（380ppm）的三倍过饱和。下游站点的 pCO2 明显高于上游站点。δC 和 pCO2 的关系表明，pCO2 控制是季节性独立的。DOC、POC 和 pCO2 之间的显著相关性表明，有机碳影响河流中的 pCO2。观察到 pCO2 的季节性波动，冬季平均为（762.23ppm）和夏季平均为（1407.35ppm）。δC 表明，代谢过程对 DIC、δC 和 pCO2 的影响可以忽略不计。δC 值从夏季的-8.95‰增加到-4.91‰，而冬季从-19.76‰增加到-1.97‰，表明 DIC 来自碳酸盐风化、大气和土壤 CO2 的溶解。δC（-30.43‰至-24.05‰）和δC（-29.87‰至-23.37‰）值证实，有机碳主要来自土壤中有机物质的降解。δC 表明，人为污水排放略微改变了 DIC 的组成。总体而言，本研究为近期 pCO2、DOC、POC、DIC、δC 及其输入的季节性波动提供了新的见解。因此，长江输送的这些碳的变化和输入可能不仅对生物地球化学循环和生态系统过程有重大影响，而且对全球碳预算也有重大影响。
