Daily Variation of CO2 Flux at Water-Air Interface and Analysis of Its Affecting Factors in a Typical River of the Three Gorges Reservoir

Abstract

Diurnal and seasonal characterization of CO2 partial pressure p(CO2) and CO2 areal flux F(CO2) at the water-air interface in an anthropogenic river in the Three Gorges Reservoir area was studied. A tributary of the Jialing River in Chongqing Municipality was chosen, and daily and seasonal samples were taken in summer and autumn, focusing on riverine p(CO2), F(CO2), and their associated controls. Henry's law combined with the thin boundary layer model was adopted to estimate the CO2 flux via the water-air interface. The results indicated that F(CO2) was not high on average, namely (87.8±27.5) mmol·(m2·d)-1 and (139.2±34.0) mmol·(m2·d)-1 in summer and autumn, respectively. The water-air interface F(CO2) showed significant hourly, daily, and seasonal variations. CO2 release peaked around 09:00 and then slightly decreased. We also found that pH, alkalinity, water, and temperature were significantly related to p(CO2) and F(CO2), whereas pH and alkalinity were the best predictors of F(CO2). This study aids understanding of the impacts of urbanization on CO2 emissions in the rivers and helps to re-evaluate local riverine CO2 budgets.