Spatial and temporal variation of dissolved CO2 in rainwater from an arid region with special focus on its association with DIC and pCO2

Kuwait, being one of the leading oil producers in the world, is enriched with CO2 in the atmosphere, despite the frequent dust storms. Rainwater dissolves the atmospheric CO2 that acts as a carbon sink. The different sources for the contribution of CO2 in an arid region like Kuwait were determined by collecting 50 rainwater samples from November 2018 to December 2019. Total CO2, dissolved inorganic carbon (DIC) and pCO(2) calculated from the analytical values of rainwater chemistry were distributed spatially to identify the specific areas enriched with CO2. Shuaiba, an industrial region, observed acidic pH (5.69) that led to the highest pCO(2) (388ppmV) while Ishbiliya, the residential area, had alkaline pH with the highest DIC and total CO2 as 1147.9 mu mole/L and 50.4 mg/L, respectively. The carbonate dust and major neutralizing ions were inferred to govern the DIC and the total CO2 in rainwater. Comparing the rainwater values to that of the groundwater and the seawater reflects similar pCO(2) values, but the seawater has very high DIC. The biotic respiration and phytoplankton community influence pCO(2) at the ocean-atmospheric interface. This phenomenon alters the transfer of CO2 to the atmospheric sink, thereby CO2 concentration in the rain showers. The statistical analysis of the rainwater chemistry data for samples from both residential and industrial regions predominantly indicated the influence of natural than anthropogenic sources. Samples of the study area and those from different parts of the world were represented in a bivariate plot using Total CO2 and (HCO3-/Ca2+ + Mg2+) variables. It was inferred from the graph that the samples of GCC region fall in a definite range.

Automated summary

This research collected rainwater samples from different regions in Kuwait to determine the sources and distribution of carbon dioxide (CO2). The results showed significant differences in the rainwater chemistry between industrial and residential areas, with natural sources having a greater impact on CO2 levels. Biotic respiration and phytoplankton communities at the ocean-atmospheric interface also influence the concentration of CO2 in rainwater.