COMPARISON OF METHODS TO MEASURE pCO2 IN THE PIABANHA RIVER BASIN

Código

XXIV-SBRH0577

Autores

Suzan Juliana da Costa Santos, Gwenael Yves Abril, Marcelo Côrrea Bernardes

Tema

SR02- Processos hidrológicos e meio ambiente

Resumo

CO2 emissions from streams and rivers represent an amount of carbon equivalent to deforestation and forest fires. There is a wide divergence from the global estimates of CO2 emissions from river systems. This is partly due to the low volume of data in the tropical region, which accounts for almost 80% of global emissions. To estimate the CO2 balance in rivers, it is necessary to carry out quantitative surveys related to measurements of the partial pressure of CO2 (pCO2) in water, since the gradient of pCO2 at the water-atmosphere interface composes the flow calculation. Otherwise, global and regional carbon balances may be overestimated or underestimated. In this context, the analysis of pCO2 in water bodies requires methodologies capable of generating reliable, comparable results that are easy to implement in remote and difficult-to-access river areas. Sample stations were distributed along the Piabanha, Paquequer and Preto rivers (Rio de Janeiro -BR) between 2018 and 2019, where four pCO2 measurement methods were implemented: a equilibrator connected to a gas analyzer Licor, penicillin headspace (ex situ), syringe headspace in situ (both determined by chromatography gaseous) and as an indirect method, pCO2 was calculated using measurements of pH and total alkalinity (TA). The syringe method presents satisfactory results for the determination of pCO2 in freshwater, being well correlated with the reference equilibrator method. This method is a viable option for monitoring pCO2 in difficult-to-access rivers. In addition, easy and cost-effective methods to monitor pCO2 in rivers are essential to promote citizen science in monitoring studies.