ZHOU Shiyu1,2, CAO Xingxing1,2, WU Pan1,2, LI Kai1,2, LI Linwei1,2

（1.School of Resource and Environmental Engineering, Guizhou University, Guiyang 550025, China; 

2.Key Laboratory of Karst Geological Resources and Environment, Ministry of Education, Guizhou University, Guiyang 550025, China）

Abstract：In order to reveal the spatial and temporal distribution characteristics of CO2 partial pressure (pCO2) at the water-air interface of karst surface rivers under the influence of acid mine drainage, the Gedangzhai River in Majang, Guizhou province, which is affected by acid mines dranage, is selected as the research sites in this study. Samples collected in wet season, dry season, and normal water season. The spatial and temporal variation of pCO2 in water and the influencing factors were measured, and the CO2 diffusion flux at the water-air interface was analyzed by the model method. The results showed that the whole river was manifested as a source of atmospheric CO2 emission. The pCO2 of the rivers was 57~122 Pa, 79~98 Pa and 146~189 Pa during the normal, dry, and wet season before the influence of acid mine drainage, respectively. Under the influence of mine acid water, the river pCO2 is 99~4034 Pa, 81~701 Pa and 146~2117 Pa, respectively. As a whole, the pCO2 in the acid mine drainage-affected reaches was higher than that in the non-acid mine drainage-affected reaches. At the same time, under the influence of acid mine drainage, river pCO2 showed a trend of increasing and then decreasing with the direction of river flow. The spatial variation trend of CO2 diffusion flux was similar to that of pCO2. The rivers front end of the riverside CO2 diffusion flux after being affected by the mineral acid and water was 5.2 ~ 203.1 times when it was not affected, and the variation was most significant in the normal period. Additionally, the flux was higher than that of the karst surface river without the influence of acid mine drainage reported in the literature. The results showed that acid mine drainage can enhance the emission of CO2 in karst surface rivers.

Key words：karst surface river; acid mine drainage; partial pressure of CO2; water-air interface; CO2 diffusion flux

EARTH AND ENVIRONMENT Vol.51, No.2, Tot No.352, 2023, Page 196