Abstract
Dissolved inorganic carbon isotope composition (δ13CDIC), together with major ion concentrations were measured in the Mun River and its tributaries in March 2018 to constrain the origins and cycling of dissolved inorganic carbon. In the surface water samples, the DIC content ranged from 185 to 5897 μmol/L (average of 1376 μmol/L), and the δ13CDIC of surface water ranged from −19.6‰ to −2.7‰. In spite of the high variability in DIC concentrations and partial pressure of carbon dioxide (pCO2), the δ13CDIC values of the groundwater were relatively consistent, with a mean value of −16.9 ± 1.4‰ (n = 9). Spatial changes occurred in the direction and magnitude of CO2 flux through water-air interface (FCO2). In the dry season, fluxes varied from −6 to 1826 mmol/(m2·d) with an average of 240 mmol/(m2·d). In addition to the dominant control on hydrochemistry and dissolved inorganic carbon isotope composition by the rock weathering, the impacts from anthropogenic activities were also observed in the Mun River, especially higher DIC concentration of waste water from urban activities. These human disturbances may affect the accurate estimate contributions of carbon dioxide from tropical rivers to the atmospheric carbon budgets.
Highlights
The global estimate of atmospheric carbon dioxide exchange shows that the amount of carbon dioxide exchanged in the tropics is huge and cannot be ignored [1]
Thailand is a traditional agricultural country, and agriculture is the largest sector of the economy
Groundwater recharge may be the main source of dissolved inorganic carbon (DIC) in the surface water, especially in the dry season
Summary
The global estimate of atmospheric carbon dioxide exchange shows that the amount of carbon dioxide exchanged in the tropics is huge and cannot be ignored [1]. Because of the role of atmospheric carbon dioxide in controlling global climate change, the process of controlling carbon in and out of inland water is receiving special attention [2,3,4,5]. The special connection between hydrological and biogeochemical processes regulating carbon dioxide fluxes in above systems is still unclear. Some studies have shown that dissolved inorganic carbon (DIC) accounts for about 50% of global carbon fluxes transported by the rivers [16]. A huge amount of DIC is transported by the river into the ocean, and released into the
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call