Impact of sulfuric acid on carbonate dissolution in the upper-middle reaches of Wujiang River

Due to rapid population and economic growth in recent years, the Wujiang River has been heavily impacted by anthropogenic activities. Of particular concern is the increase in SO4 2- concentration of the river water from various anthropogenic sources. The results showed that the major cations of groundwater and surface water were Ca2+ and Mg2+ (>70% of the cation concentration), and the main anions were HCO3- and SO4 2- (>85% of the anion concentration). In groundwater, the contributions of carbonate dissolution to Ca2+ +Mg2+ by sulfuric acid ranged from 20.6% to 92.9% (average 51.5%); and to HCO3- from 11.5% to 86.7% (average 36.9%). In the surface water, the contributions of carbonate dissolution to Ca2+ +Mg2+ ranged from 56.1% to 94.6% (average 76.9%); and to HCO3from 39.0% to 89.7% (average 64.2%). Our results demonstrate that besides carbonic acid, sulfuric acid also plays an important role on carbonate rock weathering, and influences the hydrochemistry of both groundwater and surface water in the Wujiang River drainage.