0 INTRODUCTION Permafrost refers to the ground that remains frozen year-round in polar and high-altitude regions,and its structure has traditionally been described by two distinct layers:the active layer and the permafrost layer(Dobiński,2011;French and Shur,2010;Muller,1943).The active layer undergoes seasonal cycles of thawing and freezing,which significantly influence hydrological cycles,biogeochemical processes,and ecosystem productivity(Dobiński,2020;Luo et al.,2023).
Dongliang LuoZeyong GaoFangfang ChenLuyang WangJia LiuShizhen LiQi ShenYajuan Zao
Our knowledge on permafrost carbon(C)cycle is crucial for understanding its feedback to climate warming and developing nature-based solutions for mitigating climate change.To understand the characteristics of permafrost C cycle on the Tibetan Plateau,the largest alpine permafrost region around the world,we summarized recent advances including the stocks and fluxes of permafrost C and their responses to thawing,and depicted permafrost C dynamics within this century.We find that this alpine permafrost region stores approximately 14.1 Pg(1 Pg=1015g)of soil organic C(SOC)in the top 3 m.Both substantial gaseous emissions and lateral C transport occur across this permafrost region.Moreover,the mobilization of frozen C is expedited by permafrost thaw,especially by the formation of thermokarst landscapes,which could release significant amounts of C into the atmosphere and surrounding water bodies.This alpine permafrost region nevertheless remains an important C sink,and its capacity to sequester C will continue to increase by 2100.For future perspectives,we would suggest developing long-term in situ observation networks of C stocks and fluxes with improved temporal and spatial coverage,and exploring the mechanisms underlying the response of ecosystem C cycle to permafrost thaw.In addition,it is essential to improve the projection of permafrost C dynamics through in-depth model-data fusion on the Tibetan Plateau.
This study aimed to investigate the performance evolution characteristics of concrete under permafrost ambient temperatures and to explore methods to mitigate the thermal perturbation by concrete on the permafrost environment.A program was designed to investigate the properties of various concretes at three curing conditions.The compressive strength development pattern of each group was evaluated and the concrete's performance was characterized by compressive strength damage degree,hydration temperature and SEM analysis in a low temperature environment.The experimental results show that the incorporation of fly ash alone or incombination with other admixtures in concrete under low-temperature curing does not deteriorate its microstructure,and at the same time,it can slow down the hydration rate of cement and significantly reduce the exothermic heat of hydration of concrete.These findings are expected to provide valuable references for the proportioning design of concrete in permafrost environments.
NING ZuojunLI HaoxinNIE KangjunNueraili MaimaitituersunAihemaitijiang TuerhongGAO Xiang
