RESUMEN
To examine the mountainous lake CO2 evasion in Southwest China, partial pressures of carbon dioxide[p(CO2)] and the CO2 exchange flux[F(CO2)] via the water-air interface of nine mountainous lakes in Chongqing, China, have been studied in summer using the thin boundary layer model (TBL) and floating chambers. Key water quality parameters were concomitantly measured. The results indicate that the pCO2 in the mountainous lakes in western Chongqing ranges from 2.1 to 45.0 Pa, with a mean value of (18.1±12.1) Pa. The mean CO2 fluxes calculated by the TBL model and chamber method are (-8.0±2.9), (-3.4±3.6), and (-7.1±22.3) mmol·(m2·d)-1, respectively. The p(CO2) and F(CO2) have positive correlations with the wind speed and ORP but negative correlations with the pH. Our study indicates that mountainous lakes are atmospheric sinks of CO2 and the TBL model should be cautiously adopted.
RESUMEN
An extensive investigation on the main tributaries of the Three Gorges Reservoir (TGR) region was conducted in autumn (Oct. 2015), with focuses on riverine CO2 partial pressure (pCO2) and its associated controls. Our results indicated that pCO2 in the main rivers of the TGR region ranged from 18.75 to 296.31 Pa, with a mean value of (141.06±77.51) Pa in the autumn, which was much higher than the atmospheric CO2 concentration. Therefore, the studied rivers acted as an atmospheric CO2 source, and the mean CO2 emission rate to the atmosphere was estimated at (101.1±78.0) mmol·(m2·d)-1. The highest and lowest values were (131.9±101.8) and (70.3±54.3) mmol·(m2·d)-1, respectively. pCO2 in the main rivers of the TGR area was significantly related to DO, pH, and bicarbonate. Furthermore, the biogeochemical process of within-river respiration of organic carbon rather than photosynthesis resulted in negative relationships between pCO2 and DO or pH because of the high velocities and short residence time in these mountainous rivers and streams. Our results will help to accurately develop the carbon budget for the rivers of the Three Gorges Region.
RESUMEN
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.