Hydrochemical characteristics and evolution of groundwater in the dried-up river oasis of the Tarim Basin,Central Asia

Intense human activities in arid areas have great impacts on groundwater hydrochemical cycling by causing groundwater salinization.The spatiotemporal distributions of groundwater hydrochemistry are crucial for studying groundwater salt migration,and also vital to understand hydrological and hydrogeochemical processes of groundwater in arid inland oasis areas.However,due to constraints posed by the paucity of observation data and intense human activities,these processes are not well known in the dried-up river oases of arid areas.Here,we examined spatiotemporal variations and evolution of groundwater hydrochemistry using data from 199 water samples collected in the Wei-Ku Oasis,a typical arid inland oasis in Tarim Basin of Central Asia.As findings,groundwater hydrochemistry showed a spatiotemporal dynamic,while its spatial distribution was complex.TDS and δ18O of river water in the upstream increased from west to east,whereas ion concentrations of shallow groundwater increased from northwest to southeast.Higher TDS was detected in spring for shallow groundwater and in summer for middle groundwater.Pronounced spatiotemporal heterogeneity demonstrated the impacts of geogenic,climatic,and anthropogenic conditions.For that,hydrochemical evolution of phreatic groundwater was primarily controlled by rock dominance and evaporation-crystallization process.Agricultural irrigation and drainage,land cover change,and groundwater extraction reshaped the spatiotemporal patterns of groundwater hydrochemistry.Groundwater overexploitation altered the leaking direction between the aquifers,causing the interaction between saltwater and freshwater and the deterioration of groundwater environment.These findings could provide an insight into groundwater salt migration under human activities,and hence be significant in groundwater quality management in arid inland oasis areas.

Saline dust storms and their ecological impacts in arid regions

In many arid and semiarid regions,saline playas represent a significant source of unconsoli-dated sediments available for aeolian transport,and severe saline dust storms occur frequently due to human disturbance.In this study,saline dust storms are reviewed systematically from the aspects of con-cept,general characteristics,conditions of occurrence,distribution and ecological impact.Our researches showed that saline dust storms are a kind of chemical dust storm originating in dry lake beds in arid and semiarid regions;large areas of unconsolidated saline playa sediments and frequent strong winds are the basic factors to saline dust storm occurrence;there are differentiation characteristics in deposition flux and chemical composition with wind-blown distance during saline dust storm diffusion;and saline dust storm diffusion to some extent increases glacier melt and results in soil salinization in arid regions.An under-standing of saline dust storms is important to guide disaster prevention and ecological rehabilitation.

Reduction of the wind erosion potential in dried-up lakebeds using artificial biocrusts

The artificial creation of biocrusts can be a rapid and pervasive solution to reduce wind erosion potential(WEP)in dried-up lakes(e.g.,Lake Urmia).So,in this study,we created a biocrust by the inoculation of bacteria and cyanobacteria on trays filled by soils collected from the dried-up bed of Lake Urmia,Iran,to reduce WEP in laboratory conditions.We used the wind erodible fraction of soil(EF)and soil crust factor(SCF)equations to calculate the WEP of the treated soils.EF and SCF were decreased(p<0.05)through applying the co-inoculation of bacteria and cyanobacteria by 5.6%and 10.57%,respectively,as compared to the control;also,the"cyanobacteria alone"inoculation decreased EF by 3.9%.Our results showed that the artificial biocrusts created by soil inoculation,especially with the co-using of bacteria and cyanobacteria,significantly reduced the WEP of a newly dried-up lakebed.Furthermore,we found that inoculation decreased the WEP of the study soil by increasing the soil organic matter content from 3.7 to 5 fold.According to scanning electron microscopy images,the inoculated microorganisms,especially cyanobacteria,improved soil aggregation by their exopolysaccharides and filaments;thus,they can be used with other factors to estimate the soil erodibility in well-developed biocrusts.The inoculation technique could be considered as a rapid strategy in stabilizing lakebeds against wind force.However,it should be confirmed after additional experiments using wind tunnels under natural conditions.