Reclaimed water was discharged into the Yongding River channels as ecological water. Pollutants from such water may leak into the underlying aquifer and put the groundwater environment at risk. River leakage estimation under different possible river lining conditions and the established groundwater flow and reactive solute transport model were jointly applied to investigate the impact of the ecological restoration of the Yongding River on the local groundwater environment. Scenario-based investigations were conducted since the channel reconstruction in 2009. The results show that the seepage from the Yongding River without liners can greatly raise the groundwater level. Leakage through liners constructed with geomembranes can effectively control the seepage of water and the spread of solutes in the aquifer.
Under the context of climate change, studying CO2 emissions in alpine rivers is important because of the large carbon storage in these terrestrial ecosystems. In this study, riverine partial pressure of CO2 (pCO2) and CO2 emission flux (FCO2) in the Yellow River source region (YRSR) under different landcover types, including glaciers, permafrost, peatlands, and grasslands, were systematically investigated in April, June, August, and October 2016. Relevant chemical and environmental parameters were analyzed to explore the primary controlling factors. The results showed that most of the rivers in the YRSR were net CO2 source, with the pCO2 ranging from 181 to 2441 μatm and the FCO2 ranging from −50 to 1574 mmol m−2 d−1. Both pCO2 and FCO2 showed strong spatial and temporal variations. The highest average FCO2 was observed in August, while the lowest average was observed in June. Spatially, the lowest FCO2 were observed in the permafrost regions while the highest FCO2 were observed in peatland. By integrating seasonal changes of the water surface area, total CO2 efflux was estimated to be 0.30 Tg C year−1. This indicates that the YRSR was a net carbon source for the atmosphere, which contradicts previous studies that conclude the YRSR as a carbon sink. More frequent measurements of CO2 fluxes, particularly through several diel cycles, are necessary to confirm this conclusion. Furthermore, our study suggested that the riverine dissolved organic carbon (DOC) in permafrost (5.0 ± 2.4 mg L−1) is possibly derived from old carbon released from permafrost melting, which is equivalent to that in peatland regions (5.1 ± 3.7 mg L−1). The degradation of DOC may have played an important role in supporting riverine CO2, especially in permafrost and glacier-covered regions. The percent coverage of corresponding land cover types is a good indicator for estimating riverine pCO2 in the YRSR. In view of the extensive distribution of alpine rivers in the world and their sensitivity to climate change, future studies on dynamics of stream water pCO2 and CO2 outgassing are strongly needed to better understand the global carbon cycle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.