Anthropogenic land use substantially increases riverine CO2 emissions.

• The mean p CO 2 was 1474 ± 1614 µatm in the Yue River draining to the Yangtze. • Anthropogenic land use had major seasonal influence on riverine p CO 2. • Annual CO 2 emissions were 1.6-2.8 times greater than river dissolved carbon discharge. • Urban land use and nutrient concentrations were used to predict riverine p CO 2. Carbon dioxide (CO 2) emissions from inland waters to the atmosphere are a pivotal component of the global carbon budget. Anthropogenic land use can influence riverine CO 2 emissions, but empirical data exploring cause-effect relationships remain limited. Here, we investigated CO 2 partial pressures (p CO 2) and degassing in a monsoonal river (Yue River) within the Han River draining to the Yangtze in China. Almost 90% of river samples were supersaturated in CO 2 with a mean ± standard deviation of 1474 ± 1614 µatm, leading to emissions of 557 - 971 mmol/m2/day from river water to the atmosphere. Annual CO 2 emissions were 1.6 - 2.8 times greater than the longitudinal exports of riverine dissolved inorganic and organic carbon. p CO 2 was positively correlated to anthropogenic land use (urban and farmland), and negatively correlated to forest cover. p CO 2 also had significant and positive relationships with total dissolved nitrogen and total dissolved phosphorus. Stepwise multiple regression models were developed to predict p CO 2. Farmland and urban land released nutrients and organic matter to the river system, driving riverine p CO 2 enrichment due to enhanced respiration in these heterotrophic rivers. Overall, we show the crucial role of land use driving riverine p CO 2 , which should be considered in future large-scale estimates of CO 2 emissions from streams. Land use change can thus modify the carbon balance of urban-river systems by enhancing river emissions, and reforestation helps carbon neutral in rivers. [Display omitted] [ABSTRACT FROM AUTHOR]

Copyright of Journal of Environmental Sciences (Elsevier) is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)