Desert Abiotic Carbon Sequestration Weakening by Precipitation

Abstract

Desert carbon sequestration plays an active role in promoting carbon neutralization. However, the current understanding of the effect of hydrothermal interactions and soil properties on desert carbon sequestration after precipitation remains unclear. Based on the experiment in the hinterland of the Taklimakan Desert, we found that the heavy precipitation will accelerate the weakening of abiotic carbon sequestration in deserts under the background of global warming and intensified water cycle. The high soil moisture can significantly stimulate sand to release CO2 at an incredible speed by rapidly increasing microbial activity and organic matter diffusion. At this time, the CO2 flux in the shifting sand was synergistically affected by soil temperature and soil moisture. As far as soil properties are concerned, with less organic carbon substrate and stronger soil alkalinity, the carbon sequestration of shifting sand is gradually highlighted and strengthened at low temperature. On the contrary, the carbon sequestration of shifting sand is gradually weakened. Our study provides a new way to assess the contribution of desert to the global carbon cycle and improve the accuracy and scope of application.

Thermoelectrically Regulating Heat Flux in Metal−Organic Framework Monoliths for High-Yield Atmospheric Water Harvesting in Arid Regions

“…Scanning electron microscopy and element mapping analyses were conducted using a Hitachi S4800 scanning electron microscope. N2 and water vapor adsorption isotherms were measured on a BELSORP max-II gas sorption analyzer by using a liquid nitrogen bath (77 K) and water bath (19,22,25,30,35, and 55 °C), respectively. The specific surface areas of samples were determined by the Brunauer−-Emmett−Teller (BET) method at relative N 2 pressures of 0.01−0.3 based on N 2 adsorption isotherms at 77 K. The matrix and surface temperature of CF@MOF were recorded using a fluorescence temperature detector (TMEAS FM-07) and an infrared (IR) camera (Testo 871), respectively.…”

“…However, water adsorption is an exothermal process accompanied by the release of a large amount of adsorption heat (up to 56 kJ mol −1 ). , Due to the thermal insulating nature of MOFs rendered by their exceptionally high porosity, such adsorption heat would inevitably accumulate in MOFs and significantly compromise the water adsorption capabilities. This negative impact becomes extremely prominent when MOFs are implemented at large scales in industrially favorable compact forms such as bulky monoliths, and AWH is carried out in hot environments such as deserts where the air temperature may rise to 46 °C during the day. Opposite to water adsorption, the heat-driven water desorption process is an endothermal process that requires a large amount of energy input, representing one of the major contributions to the overall energy cost of MOF-based AWH.…”

“…The automatic atmospheric water harvester consisted of two PMMA chambers (26 × 19 × 6 cm 3 ), a condenser (48 W), a PLC system (200 W), and an MTMbased sorption unit consisting of six MTMs (35.4 W) and a forcing fan (10 W) in which each MOF side was accommodated in the chambers. The RH (30%) and temperature (25,30,35, and 40 °C) of tested arid air were controlled by a Constant Humidity Chamber and recorded with a Temperature/Humidity Meter (Fatai L95-8, China). Before conducting the continuous water production, atmospheric water adsorption was first conducted on the cold MOF side of MTM for 2 h. Then, upon reversing the applied current direction on MTMs every 2 h, the continuous water production of water harvester was achieved.…”