Analysis of Environmental Controls on the Quasi-Ocean and Ocean CO 2 Concentration by Two Intelligent Algorithms

Previous studies have demonstrated CO 2 absorption by soils in arid regions, where the absorbed CO 2 is conjectured to be finally sequestrated in the “subterranean ocean”—groundwater. This study compares environmental controls of ocean CO 2 concentration (surface ocean pCO 2 ) and quasi-ocean CO 2 concentration (deep-soil pCO 2 ). We aim to explore the latent relationship, both linear and nonlinear between the environmental variables, and CO 2 concentration, utilizing two intelligent algorithms—the partial least linear regression (PLSR) algorithm and the artificial neural network (ANN) algorithm. For quasi-ocean CO 2 concentration, RPD <1.4 and R 2 <40%. While for ocean CO 2 concentration, RPD >1.4 and R 2 is 99.7%. Linear relationships between the considered environmental controls and ocean CO 2 concentration are proved; however, there is no evident relationship between most of the considered environmental controls and quasi-ocean CO 2 concentration. Groundwater level is proved to be a relatively important environmental control on the quasi-ocean CO 2 concentration, suggesting groundwater discharge/recharge as a significant modulator of soil CO 2 absorption in arid regions.