Soil CO2 Uptake in Deserts and Its Implications to the Groundwater Environment

Abstract

Recent studies of soil carbon cycle in arid and semi-arid ecosystems demonstrated that there exists an abiotic CO 2 absorption by saline-alkali soils (A a ) at desert ecosystems and suggested potential contributions of CO 2 dissolution beneath deserts to the terrestrial ecosystems carbon balance. However, the overall importance of such soil CO 2 uptake is still undetermined and its implications to the groundwater environment remain unaddressed. In this manuscript, a simple method is proposed for the direct computation of A a from the total soil CO 2 flux (F a ) as well as for the evaluation of A a importance to F a . An artificial soil-groundwater system was employed to investigate the implications to groundwater environment and it was found that soil CO 2 uptake in deserts can contribute a possible influence on the evolution of the groundwater environment, providing that the absorbed CO 2 largely remained in the soil-groundwater system.

CO<sub>2</sub> and CH<sub>4</sub> fluxes are decoupled from organic carbon loss in drying reservoir sediments

“…Further research on the fate of the alkalinity produced by the calcium carbonate chemical weathering process is also needed to determine its impact on the carbon budget of lakes and reservoirs that seasonally or permanently dry. While CaCO 3 chemical weathering decreases CO 2 efflux, it is unlikely to constitute a long-term carbon sink if the bicarbonate ions produced by dissolution eventually transfom to CO 2 and re-enter the atmosphere through equilibration (Wang et al, 2016). However, if the bicarbonate ions produced by CaCO 3 dissolution are sequestered in either sediment or groundwater, it is also possible that the CO 2 influx observed in this study constitutes the basis of a previously unrecognized long-term carbon sink.…”

“…Those that do generally link chemical weathering to factors that are not applicable in the context of this investigation, i.e. climate (Lapenis et al, 2008)), high sediment alkalinity (Lapenis et al, 2008;Emmerich, 2003;Xie et al, 2009;Wang et al, 2016;Ma et al, 2014), and diurnal cycling (Roland et al, 2013;Hamerlynck et al, 2013;Chen and Wang, 2014;Fa et al, 2016). This raises the question of what conditions caused the calcium carbonate chemical weathering hypothesized to occur here.…”

Examining the Potential Environmental Controls of Underground CO2 Concentration in Arid Regions by an SVD-PCA-ANN Preview Model

“…Differing from the variability in soil surface CO 2 concentration and the atmospheric CO 2 concentration, the dynamics of CO 2 concentration beneath the ground might be influenced by many environmental factors and unknown subterranean processes [9][10][11][12][13][14][15][16][17]. Until now, the whole story of soil CO 2 absorption in arid regions is still a gap in our knowledge [31].…”

“…is implied that the underground CO 2 concentration in arid regions is closely linked with the soil surface CO 2 concentration. However, the controls of soil absorption of CO 2 in arid regions were not well-explained until now [12][13][14][15]. One significant reason is that the CO 2 concentration beneath the soil might be influenced by many factors and up to now, and the corresponding theoretical basis has not been well-described [16].…”

Effects of Prescribed Burning on Soil CO2 Emissions from Pinus yunnanensis Forestland in Central Yunnan, China

“…The changes in soil respiration and its 2 of 12 influencing factors must be determined for prediction of global climate change. Most studies have focused on undisturbed ecosystems, such as forests [10], grasslands [11], wetlands [12], deserts [13], and tundra [14], while ignoring the changes in the carbon cycle in these ecosystems in response to factors such as fire control [15], litter removal [16], clear-cutting [17], and nitrogen addition [18]. In particular, the carbon cycle of an ecosystem under disturbance is more complex and has practical significance, which needs much more attention.…”