Glacier variations and their response to climate change in an arid inland river basin of Northwest China

Glaciers are a critical freshwater resource of river recharge in arid areas around the world.In recent decades,glaciers have shown evidence of retreat due to climate change,and the accelerated ablation of glaciers and associated impacts on water resources have received widespread attention.Glacier variations result from climate change,so they can serve as an indicator of climate change.Considering the climatic differences in different elevation ranges,it is worthwhile to explore whether different responses exist between glacier area and air temperature in each elevation zone.In this study,we selected a typical arid inland river basin(Sugan Lake Basin)in the western Qilian Mountains of Northwest China to analyze the glacier variations and their response to climate change.The glacier area data from 1989 to 2016 were delineated using Landsat Thematic Mapper(TM),Enhanced TM+(ETM+)and Operational Land Imager(OLI)images.We compared the relationships between glacier area and air temperature at seven meteorological stations in the glacier-covered areas and in the Sugan Lake Basin,and further analyzed the relationship between glacier area and mean air temperature of the glacier surfaces in July–August in the elevation range of 4700–5500 m a.s.l.by the linear regression method and correlation analysis.In addition,based on the linear regression relationship established between glacier area and air temperature in each elevation zone,we predicted glacier areas under future climate scenarios during the periods of 2046–2065 and 2081–2100.The results indicate that the glaciers experienced a remarkable shrinkage from 1989 to 2016 with a shrinkage rate of–1.61 km^2/a(–0.5%/a),and the rising temperature is the decisive factor dominating glacial retreat;there is a significant negative linear correlation between glacier area and mean air temperature of the glacier surfaces in July–August in each elevation zone from 1989 to 2016.The variations in glaciers are far less sensitive to changes in precipitation than to changes in air temperature.Due to the influence of climate and topographic conditions,the distribution of glacier area and the rate of glacier ablation first increased and then decreased in different elevation zones.The trend in glacier shrinkage will continue because air temperature will continue to increase in the future,and the result of glacier retreat in each elevation zone will be slightly slower than that in the entire study area.Quantitative glacier research can more accurately reflect the response of glacier variations to climate change,and the regression relationship can be used to predict the areas of glaciers under future climate scenarios.These conclusions can offer effective references for assessing glacier variations and their response to climate change in arid inland river basins in Northwest China as well as other similar regions in the world.

A modified damage and fracture phase field model considering heterogeneity for rock‐like materials

Damage and fracture are the most extensive failure modes of rock materials,which may easily induce disaster and instability of engineering structures.This study developed a nonlocal damage fracture phase field model for rocks considering the heterogeneity of rocks.The modified phase field model introduced the heterogeneity of fracture parameters and modified the governing equations.Meanwhile,the free energy was constructed by the elastic strain energy sphere‐bias decomposition and the plastic strain energy.As for the numerical implementation,the three layers finite elements method structure was used in the frame of the finite element method.The ability of the modified phase field model has been illustrated by reproducing the experiment results of rock samples with pre‐existing cracks under compression.

Identification of visible colored dissolved organic matter in biological and tertiary municipal effluents using multiple approaches including PARAFAC analysis

This study provided insights into the persistent yellowish color in biological and tertiary effluents of municipal wastewater through a multi-characterization approach and fluorescence excitation-emission matrix-parallel factor(EEM-PARAFAC)analysis.The characterization was performed on three to five full-scale municipal wastewater treatment plants(WWTPs),including differential log-transformed absorbance(DLn A)spectroscopy,resin fractionation,size-exclusion chromatography for apparent molecular weight analysis(SECAMW),and X-ray photoelectron spectroscopy(XPS)analysis.Hydrophobic acids(HPOA)were abundant in visible colored dissolved organic matter(DOM).The SEC-AMW result showed that the molecular weight of the colored substances in the secondary effluents is mainly distributed in the range of 2–3 k Da.Through XPS analysis,C-O/C-N and pyrrolic/pyridonic(N-5)were found to be positively correlated with chroma.PARAFAC component models were built on biological(two components)and tertiary effluent(three components)and the correlation analysis revealed that PARAFAC component 2 in biological effluent(BE-C2)and component 1in tertiary effluent(TE-C1),which were ascribed to Hydrophobic acids and Humic acid-like,were the responsible visible colored DOM components cause yellowish color.In addition,component similarity testing found that the identified visible colored DOM PARAFAC BE-C2,and PARAFAC TE-C1 were identical(0.96)in physicochemical properties,with 4%removal efficacy on average,compared with 11%for invisible colored DOM.This implied that tertiary effluents containing colorants(TE-C1)were resistant to degradation/removal using different disinfection and filtration processes in advanced treatments.This sheds light on many physicochemical aspects of PARAFAC-identified visible colored DOM components and provides spectral data to build an online monitoring system.