Real-time and dynamic estimation of CO<sub>2</sub> emissions from China��s lakes and reservoirs

Abstract

<p>Lakes and reservoirs act as active carbon (C) reactors and regulators. Both play a crucial terrestrial ecosystem C balance role via carbon dioxide (CO<sub>2</sub>) exchange processes across the water-air interface. It has previously been confirmed that CO<sub>2</sub> flux from lakes and reservoirs generally exhibits significant spatiotemporal heterogeneity. Nevertheless, spatiotemporal CO<sub>2</sub> flux variation has seldom been considered in global and regional CO<sub>2</sub> emission estimates from lakes and reservoirs. By accounting for spatiotemporal CO<sub>2</sub> flux and water surface area variability, we evaluated spatial and temporal CO<sub>2</sub> emission dynamics from China��s inland lakes and reservoirs using national real-time water quality monitoring data and machine learning (ML) models. Between 2021�C2022, we estimated total C emission flux at 6.78 (��2.5) Tg C yr<sup>?1</sup>, where seasonal and regional distribution both exhibited significant heterogeneity. Our state-of-the-art estimate is significantly lower than previous estimates of 7.9~25 Tg C yr<sup>?1</sup> from the 1980s to the 2010s. Water quality parameters (pH and dissolved oxygen [DO]) and climate factors (air temperature) were identified as the general environmental CO<sub>2</sub> flux controls. For the first time, this study clarifies the spatiotemporal patterns and drivers of CO<sub>2</sub> flux from China��s inland lakes and reservoirs, providing a more complete C budget picture of China��s aquatic ecosystems.</p>