Abstract
The majority of rivers are a CH4 source that accounts for an important proportion of annual global emissions. However, CH4 evasion from urban river networks has received disproportionately less attention than their contribution. The effect of water governance on water quality and CH4 emission in urban areas remains unclear. Water quality, CH4 concentrations, and fluxes from a river network in Binhu District, Wuxi City, and their response to water governance were analyzed in this study. CH4 concentrations in the investigated rivers ranged from 0.05 μmol L−1 to 16.37 μmol L−1 (2.47 ± 4.5 μmol L−1, medium 0.23 μmol L−1), and CH4 diffusive fluxes were 75.55 ± 171.78 μmol m−2 h−1 with a medium of 6.50 μmol m−2 h−1. CH4 concentration showed a significant correlation with water quality parameters, especially for NH3–N (r = 0.84, p < 0.001). Significant differences in water quality and CH4 levels were found between sites that had conducted water management and those that continued to exhibit poor water quality. Our analysis showed that rivers under water governance have a positive tendency toward water ecological restoration, and a significant decrease in CH4 efflux to the air can be achieved after extensive and intensified water governance.
Highlights
CH4 is a potent greenhouse gas, and the global warming potential per CH4 molecule is approximately 30 times greater than that of CO2 at a 100-year time scale
CH4 concentrations in the investigated rivers ranged from 0.05 μmol L−1 to 16.37 μmol L−1 (2.47 ± 4.5 μmol L−1, medium 0.23 μmol L−1 ) based on 21 measured data, and according to the measured in situ water temperature and mean wind speed from the meteorological website (~2.5 m s−1 ), the calculated CH4 diffusive fluxes were 75.55 ± 171.78 μmol m−2 h−1 with a medium of 6.50 μmol m−2 h−1 (Table 2)
18, 21, 24, and 26, demonstrated CH4 concentrations higher than 1 μmol L−1. These results indicated high CH4 concentration in Xianjingbang and Lucunhe Rivers and in the downstream of Chendahe
Summary
CH4 is a potent greenhouse gas, and the global warming potential per CH4 molecule is approximately 30 times greater than that of CO2 at a 100-year time scale. Carbon evasion from the Shanghai river network can offset up to 40% of regional terrestrial net ecosystem production and 10% of net carbon uptake in the river-dominated East China Sea [7]. Both studies of rivers in Shanghai and Chongqing found that urban and suburban areas contribute higher river CH4 concentration and flux than rural locations due to the worse water quality of the former [7,8]. CH4 evasion from urban river networks requires additional attention as the urbanization process and proportion of urban land use increase globally
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