Human Activities Elevate Greenhouse Gas Emissions from Inland Waters in a Rapidly Urbanizing Region of China

Greenhouse gas (GHGs) emissions from inland waters constitute an important part of the global carbon (C) cycle. However, the effects of different types of water bodies influenced by human activities on GHG emissions remain unclear, particularly in regions undergoing rapid urbanization and economic development. This study investigated the temporal and spatial changes in GHG (N2O, CH4, and CO2) concentrations and the causes of these changes in different types of water bodies influenced by human activities, specifically undisturbed natural rivers, water supply reservoirs, ecotourism lakes and rivers, aquaculture ponds, water bodies within agricultural land, and water bodies within industrial land, in Jiashan County, China. We collected 96 samples across these water bodies for each season of the year. The results show that all the investigated water bodies were C sources. Substantial variability in the concentrations and fluxes of GHGs was observed within these water bodies, and this variability was strongly influenced by human activity. Specifically, approximately twofold higher GHG emissions were observed at aquaculture ponds and industrial sites than at other sites. However, sites with minimal human intervention, such as undisturbed natural rivers, water supply reservoirs, and ecotourism lakes, had comparatively low GHG emissions. The N2O concentrations were primarily regulated by temperature, NH4+, and pH, whereas the CH4 concentrations were strongly correlated with total nitrogen and dissolved oxygen concentrations. CO2 concentrations were closely related to salinity, relative humidity, and temperature. This study emphasizes the importance of gaining a better understanding of the effects of water bodies influenced by human activities on GHG emissions, particularly considering the potential changes in water utilization patterns and rapid population growth around urban rivers in the future.