Description:
Sustained wetland utilization has been effective in purifying urban riverine pollutants and promoting sustainable development. However, its effect on water CO2 system remains unclear in semi-arid areas. In this study, seasonal monitoring of the carbonate system was performed at two compared stations, i.e., in constructed wetland (Xiangyun station) and its upstream (Lancun station) in a semi-arid river (the Fenhe River) in China. As indicated by the result of the sustained monthly observation from May 2020 to May 2021, riverine dissolved inorganic carbon (DIC) and partial pressure of CO2 (pCO2) reached 30.9–46.7 mg L−1 and 524–1050 μatm in Lancun station, respectively, whereas the above-described values declined significantly in Xiangyun station with the values of 24.1–39.1 mg L−1 for DIC and 188–873 μatm for pCO2. Compared with the Lancun station where the carbonate system was primarily controlled by natural factors (e.g., carbonate weathering and temperature), significant aquatic photosynthesis and calcification precipitation due to constructed wetland triggered the decrease in DIC and pCO2 and dominated their temporal variation in Xiangyun station. Thus, the large CO2 reduction arising from constructed wetlands may create vital paths for CO2 neutralization and sustainable conservation in urban rivers in arid and semi-arid areas in the future.