Energy and resources including coal, oil, and gas are in demand all over the world. Because these resources near the earth's surface have been exploited for many years, the extraction depth has increased.As mining...Energy and resources including coal, oil, and gas are in demand all over the world. Because these resources near the earth's surface have been exploited for many years, the extraction depth has increased.As mining shafts in the coal extraction process become deeper, especially in western China, an artificial freezing method is used and is concentrated in the fractured rock mass. The frost-heaving pressure(FHP)is directly related to the degree of damage of the fractured rock mass. This paper is focused on FHP during the freezing process, with emphasis on the frost-heaving phenomenon in engineering materials. A review of the frost phenomenon in the geotechnical engineering literature indicates that:(1) During the soil freezing process, the ice content that is influenced by unfrozen water and the freezing rate are the determining factors of FHP;(2) During the freezing process of rock and other porous media, the resulting cracks should be considered because the FHP may damage the crack structure;(3) The FHP in a joint rock mass is analyzed by the joint deformation in field and experimental tests and can be simulated by the equivalent expansion method including water migration and joint deformation.展开更多
High total dissolved solids （TDS） content is one of the most important pollution contributors in lakes in arid and semiarid areas. Ulansuhai Lake, located in Urad Qianqi, Inner Mongolia, China, was selected as the o...High total dissolved solids （TDS） content is one of the most important pollution contributors in lakes in arid and semiarid areas. Ulansuhai Lake, located in Urad Qianqi, Inner Mongolia, China, was selected as the object of study. Temperatures and TDS contents of both ice and under-ice water were collected together with corresponding ice thickness. TDS profiles were drawn to show the distribution of TDS and to describe TDS migration. The results showed that about 80% （that is 3.602x108 kg） of TDS migrated from ice to water during the whole growth period of ice. Within ice layer, TDS migration only occurred during initial ice-on period, and then perished. The TDS in ice decreased with increasing ice thickness, following a negative exponential-like trend. Within un- der-ice water, the TDS migrated from ice-water interface to the entire water column under the effect of concentra- tion gradient until the water TDS content was uniform. In winter, 6.044x 107 kg （16.78% of total TDS） TDS migrated from water to sedirnent, which indicated that winter is the best time for dredging sediment. The migration effect gives rise to TDS concentration in under-ice water and sediment that is likely to affect ecosystem and water quality of the Yellow River. The trend of transfer flux of ice-water and water-sediment interfaces is similar to that of ice growth rate, which reveals that ice growth rate is one of the determinants of TDS migration. The process and mechanism of TDS migration can be referenced by research on other lakes with similar TDS content in cold and arid areas.展开更多
Frost heave experiments on saturated sandstone and tuff with an open crack are conducted under uniform and unidirectional freezing conditions.Frost heave of crack in sandstone with high permeability is more significan...Frost heave experiments on saturated sandstone and tuff with an open crack are conducted under uniform and unidirectional freezing conditions.Frost heave of crack in sandstone with high permeability is more significant under uniform freezing condition than that under unidirectional freezing condition.However,frost heave of crack in tuff with low permeability is more significant under unidirectional freezing condition.To illustrate the reasons for this phenomenon,a numerical model on the freezing processes of saturated rock with an open crack considering the latent heat of pore water and water in crack is proposed and confirmed to be reliable.Numerical results show that a frozen shell that blocks the migration of water in crack to rock develops first in the outer part of the rock before the freezing of water in crack under unifonn freezing condition.However,the migration path of water in crack to the unfrozen rock under freezing front exists under unidirectional freezing condition.The freezing process and permeability of rock together determine the migration of water in crack and lead to the different frost heave modes of crack for various permeable rocks under different freezing conditions.The frost heave modes of crack in rock with low or high permeability are similar under uniform freezing condition because water migration is blocked by a frozen shell and is irrelevant to rock permeability.For high permeability rock,the frost heave of crack will be weakened due to water migration under unidirectional freezing condition;however,the frost heave of crack would be more significant for low permeability rock because water migration is blocked under unidirectional freezing condition.Therefore,the freezing condition and rock permeability determine the frost heave of rock with crack together,and this should be concerned in cold regions engineering applications.展开更多
The coupled heat and moisture transfer in a freezing process of wood particle material was mathematically modeled in the paper. The models were interactively solved by using the numerical method(the finite element met...The coupled heat and moisture transfer in a freezing process of wood particle material was mathematically modeled in the paper. The models were interactively solved by using the numerical method(the finite element method and the finite difference method). By matching the theoretical calculation to an experiment, the nonlinear problem was analyzed and the variable thermophysical parameters concerned was evaluated. The analysis procedure and the evaluation of the parameters were presented in detail. The result of the study showed that by using the method as described in the paper, it was possible to determine the variable (with respect to temperature, moisture content and freezing state) thermophysical parameters which were unknown or difficult to measure as long as the governing equations for a considered process were available. The method can significantly reduces the experiment efforts for determining thermophysical parameters which arc very complicated to measure. The determined variable of the effective heat conductivity of wood particle material was given in the paper. The error of the numerical calculation was also estimated by the comparison with a matched experiment.展开更多
A frozen soil parameterization coupling of thermal and hydrological processes is used to investigate how frozen soil processes affect water and energy balances in seasonal frozen soil. Simulation results of soil liqui...A frozen soil parameterization coupling of thermal and hydrological processes is used to investigate how frozen soil processes affect water and energy balances in seasonal frozen soil. Simulation results of soil liquid water content and temperature using soil model with and without the inclusion of freezing and thawing processes are evaluated against observations at the Rosemount field station. By comparing the simulated water and heat fluxes of the two cases, the role of phase change processes in the water and energy balances is analyzed. Soil freezing induces upward water flow towards the freezing front and increases soil water content in the upper soil layer. In particular, soil ice obviously prevents and delays the infiltration during rain at Rosemount. In addition, soil freezingthawing processes alter the partitioning of surface energy fluxes and lead the soil to release more sensible heat into the atmosphere during freezing periods.展开更多
Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size ...Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size groups, different water contents, various freeze-thaw cycles, and various freezing temperatures. The results showed that, when at suitable water content, aggregate stability was enhanced, aggregate sta-bility will be disrupted when moisture content is too high or too low, especially higher water content. Temperature also had a significant ef-fect, but moisture content determined the suitable freezing temperatures for a given soil. Water-stable aggregate （WSA〉0.5）, the total aggre-gate content, and mean weight diameter decreasing with the freeze-thaw cycles increase, reached to 5 percent significance level. The reason for crumbing aggregates is the water and air conflict, thus raising the hypothesis that water content affects the aggregate stability in the process of freezing and thawing.展开更多
It is generally known that soil pollution poses a terrible hazard to the environment, but the present techniques of contaminated soil remediation cannot control this growing threat. This paper compares the pollutant e...It is generally known that soil pollution poses a terrible hazard to the environment, but the present techniques of contaminated soil remediation cannot control this growing threat. This paper compares the pollutant extraction efficiency of traditional pumping and treating, which is a typical washing technology for the remediation of contaminated soils, with methods that utilize freeze-thaw cycles. In the soil freezing process, water shifts from unfrozen soils to the freezing front, and the permeability of soil will be enhanced under certain temperature gradients and water conditions. Therefore, this paper discusses the purification of contaminated soil through freeze-thaw action. We conducted a cleansing experiment on clay and silica sand infused with NaCl（simulation of heavy metals） and found that the efficiency of purification was enhanced remarkably in the latter by the freeze-thaw action. To assess the effective extraction of DNAPLs in soil, we conducted an experiment on suction by freezing, predicated on the different freezing points of moisture and pollutants. We found that the permeability coefficient was significantly increased by the freezing-thawing action, enabling the DNAPL contaminants to be extracted selectively and effectively.展开更多
Hydrate formation and dissociation processes are always accompanied by water migration in porous media, which is similar to the ice. In our study, a novel pF-meter sensor which could detect the changes of water conten...Hydrate formation and dissociation processes are always accompanied by water migration in porous media, which is similar to the ice. In our study, a novel pF-meter sensor which could detect the changes of water content inside sand was first applied to hydrate formation and dissociation processes. It also can study the water change characteristics in the core scale of a partially saturated silica sand sample and compare the differences of water changes between the processes of formation and dissociation of methane hydrate and freezing and thawing of ice. The experimental results showed that the water changes in the processes of formation and dissociation of methane hydrate were basically similar to that of the freezing and thawing of ice in sand. When methane hydrate or ice was formed, water changes showed the decrease in water content on the whole and the pF values rose following the formation processes. However, there were very obvious differences between the ice thawing and hydrate dissociation.展开更多
Background Seasonal freeze-thaw(FT)processes alter soil formation and cause changes in soil microbial communi-ties,which regulate the decomposition of organic matter in alpine ecosystems.Soil aggregates are basic stru...Background Seasonal freeze-thaw(FT)processes alter soil formation and cause changes in soil microbial communi-ties,which regulate the decomposition of organic matter in alpine ecosystems.Soil aggregates are basic structural units and play a critical role in microbial habitation.However,the impact of seasonal FT processes on the distribution of microbial communities associated with soil pores in different aggregate fractions under climate change has been overlooked.In this study,we sampled soil aggregates from two typical alpine ecosystems(alpine meadow and alpine shrubland)during the seasonal FT processes(UFP:unstable freezing period,SFP:stable frozen period,UTP:unstable thawing period and STP:stable thawed period).The phospholipid fatty acid(PLFA)method was used to determine the biomass of living microbes in different aggregate fractions.Results The microbial biomass of 0.25–2 mm and 0.053–0.25 mm aggregates did not change significantly dur-ing the seasonal FT process while the microbial biomass of>2 mm aggregates presented a significant difference between the STP and UTP.Bacterial communities dominated the microbes in aggregates,accounting for over 80%of the total PLFAs.The microbial communities of soil aggregates in the surface layer were more sensitive to the sea-sonal FT process than those in other soil layers.In the thawing period,Gram positive bacteria(GP)was more dominant.In the freezing period,the ratio of Gram-positive to Gram-negative bacterial PLFAs(GP/GN)was low because the enrichment of plant litter facilitated the formation of organic matter.In the freezing process,pores of 30–80μm(mesopores)favored the habitation of fungal and actinobacterial communities while total PLFAs and bacterial PLFAs were negatively correlated with mesopores in the thawing process.Conclusions The freezing process caused a greater variability in microbial biomass of different aggregate fractions.The thawing process increased the differences in microbial biomass among soil horizons.Mesopores of aggregates supported the habitation of actinobacterial and fungal communities while they were not conducive to bacterial growth.These findings provide a further comprehension of biodiversity and accurate estimation of global carbon cycle.展开更多
Freeze-induced acceleration of I–oxidation and the consequent iodination of dissolved organic matter(DOM)contribute to the formation of organoiodine compounds(OICs)in cold regions.The formed OICs may be a potentially...Freeze-induced acceleration of I–oxidation and the consequent iodination of dissolved organic matter(DOM)contribute to the formation of organoiodine compounds(OICs)in cold regions.The formed OICs may be a potentially important source of risk and are very closely with the environment and human health.Herein,we investigated the acceleration effects of the freeze process on I–oxidation and the formation of OICs.In comparison to reactive iodine species(RIS)formed in aqueous solutions,I–oxidation and RIS formation were greatly enhanced in frozen solution and were affected by pH,and the content of I–and O_(2).Freeze-thaw process further promoted I–oxidation and the concentration of RIS reached 45.7μmol/L after 6 freeze-thaw cycles.The consequent products of DOM iodination were greatly promoted in terms of both concentration and number.The total content of OICs ranged from 0.02 to 2.83μmol/L under various conditions.About 183–1197 OICs were detected by Fourier transform ion cyclotron resonance mass spectrometry,and more than 96.2%contained one or two iodine atoms.Most OICs had aromatic structures and were formed via substitution and addition reactions.Our findings reveal an important formation pathway for OICs and shed light on the biogeochemical cycling of iodine in the natural aquatic environment.展开更多
The coupling effects and mechanisms of water,heat,and salt in frozen soils are considered to be one of the core scientific issues in frozen soil studies.This study was based on in situ observation data of active layer...The coupling effects and mechanisms of water,heat,and salt in frozen soils are considered to be one of the core scientific issues in frozen soil studies.This study was based on in situ observation data of active layer soil volumetric water content(VWC),temperature,and bulk electrical conductivity(EC)obtained at an alpine meadow site from October 2016 to November 2019.The site is located in the headwater area of the Yellow River(HAYR).We analyzed the synergetic variations of active layer soil VWC,temperature,and bulk EC during the freeze and thaw processes and discussed the underlying mechanisms.When the thaw process occurred from 10 to 80 cm depths,the VWC and bulk EC at a 10 cm depth showed syn-chronous high-frequency fluctuations and both increased linearly.The linear decreasing rate of the VWC(bulk EC)at an 80 cm depth in the freeze depths between 0 and 40 cm was 2(1.6e2.3)times that of the VWC(bulk EC)at an 80 cm depth in the freeze depths occurring 0e10 cm.As soil temperature decreased in the frozen layer,unfrozen water content(bulk EC)decreased nonlinearly along with the absolute value of soil temperature(|T|),following a power(logarithmic)function.This study provided data that partly elucidate the interactions among permafrost,meadow,and ecohydrological processes in the HAYR.Also,our results can be used as a scientific basis for decision making on the protection and restoration of alpine grasslands,as well as for soil salinization studies.展开更多
基金financial assistance provided by the National Natural Science Foundation of China (Nos. B14021 and 51304209)the Science Foundation of Jiangsu (No. 16KJB580014)
文摘Energy and resources including coal, oil, and gas are in demand all over the world. Because these resources near the earth's surface have been exploited for many years, the extraction depth has increased.As mining shafts in the coal extraction process become deeper, especially in western China, an artificial freezing method is used and is concentrated in the fractured rock mass. The frost-heaving pressure(FHP)is directly related to the degree of damage of the fractured rock mass. This paper is focused on FHP during the freezing process, with emphasis on the frost-heaving phenomenon in engineering materials. A review of the frost phenomenon in the geotechnical engineering literature indicates that:(1) During the soil freezing process, the ice content that is influenced by unfrozen water and the freezing rate are the determining factors of FHP;(2) During the freezing process of rock and other porous media, the resulting cracks should be considered because the FHP may damage the crack structure;(3) The FHP in a joint rock mass is analyzed by the joint deformation in field and experimental tests and can be simulated by the equivalent expansion method including water migration and joint deformation.
基金Financial support was provided by the National Natural Science Foundation of China (50569002,50669004 and 51069007)Natural Science Foundation of Inner Mongolia (200711020604)Key Project from Department of Water Resources of Inner Mongolia (20080105)
文摘High total dissolved solids （TDS） content is one of the most important pollution contributors in lakes in arid and semiarid areas. Ulansuhai Lake, located in Urad Qianqi, Inner Mongolia, China, was selected as the object of study. Temperatures and TDS contents of both ice and under-ice water were collected together with corresponding ice thickness. TDS profiles were drawn to show the distribution of TDS and to describe TDS migration. The results showed that about 80% （that is 3.602x108 kg） of TDS migrated from ice to water during the whole growth period of ice. Within ice layer, TDS migration only occurred during initial ice-on period, and then perished. The TDS in ice decreased with increasing ice thickness, following a negative exponential-like trend. Within un- der-ice water, the TDS migrated from ice-water interface to the entire water column under the effect of concentra- tion gradient until the water TDS content was uniform. In winter, 6.044x 107 kg （16.78% of total TDS） TDS migrated from water to sedirnent, which indicated that winter is the best time for dredging sediment. The migration effect gives rise to TDS concentration in under-ice water and sediment that is likely to affect ecosystem and water quality of the Yellow River. The trend of transfer flux of ice-water and water-sediment interfaces is similar to that of ice growth rate, which reveals that ice growth rate is one of the determinants of TDS migration. The process and mechanism of TDS migration can be referenced by research on other lakes with similar TDS content in cold and arid areas.
基金This study was supported by the National Natural Science Foundation of China (Grant Nos.51778475 and 41472248).
文摘Frost heave experiments on saturated sandstone and tuff with an open crack are conducted under uniform and unidirectional freezing conditions.Frost heave of crack in sandstone with high permeability is more significant under uniform freezing condition than that under unidirectional freezing condition.However,frost heave of crack in tuff with low permeability is more significant under unidirectional freezing condition.To illustrate the reasons for this phenomenon,a numerical model on the freezing processes of saturated rock with an open crack considering the latent heat of pore water and water in crack is proposed and confirmed to be reliable.Numerical results show that a frozen shell that blocks the migration of water in crack to rock develops first in the outer part of the rock before the freezing of water in crack under unifonn freezing condition.However,the migration path of water in crack to the unfrozen rock under freezing front exists under unidirectional freezing condition.The freezing process and permeability of rock together determine the migration of water in crack and lead to the different frost heave modes of crack for various permeable rocks under different freezing conditions.The frost heave modes of crack in rock with low or high permeability are similar under uniform freezing condition because water migration is blocked by a frozen shell and is irrelevant to rock permeability.For high permeability rock,the frost heave of crack will be weakened due to water migration under unidirectional freezing condition;however,the frost heave of crack would be more significant for low permeability rock because water migration is blocked under unidirectional freezing condition.Therefore,the freezing condition and rock permeability determine the frost heave of rock with crack together,and this should be concerned in cold regions engineering applications.
文摘The coupled heat and moisture transfer in a freezing process of wood particle material was mathematically modeled in the paper. The models were interactively solved by using the numerical method(the finite element method and the finite difference method). By matching the theoretical calculation to an experiment, the nonlinear problem was analyzed and the variable thermophysical parameters concerned was evaluated. The analysis procedure and the evaluation of the parameters were presented in detail. The result of the study showed that by using the method as described in the paper, it was possible to determine the variable (with respect to temperature, moisture content and freezing state) thermophysical parameters which were unknown or difficult to measure as long as the governing equations for a considered process were available. The method can significantly reduces the experiment efforts for determining thermophysical parameters which arc very complicated to measure. The determined variable of the effective heat conductivity of wood particle material was given in the paper. The error of the numerical calculation was also estimated by the comparison with a matched experiment.
基金supported by the National Basic Research Program of China under Grant No 2006CB400504National Natural Science Foundation of China under Grant Nos 40605027 and 40775050
文摘A frozen soil parameterization coupling of thermal and hydrological processes is used to investigate how frozen soil processes affect water and energy balances in seasonal frozen soil. Simulation results of soil liquid water content and temperature using soil model with and without the inclusion of freezing and thawing processes are evaluated against observations at the Rosemount field station. By comparing the simulated water and heat fluxes of the two cases, the role of phase change processes in the water and energy balances is analyzed. Soil freezing induces upward water flow towards the freezing front and increases soil water content in the upper soil layer. In particular, soil ice obviously prevents and delays the infiltration during rain at Rosemount. In addition, soil freezingthawing processes alter the partitioning of surface energy fluxes and lead the soil to release more sensible heat into the atmosphere during freezing periods.
基金National Basic Research Program of China (2005CB121101, 2005CB121103)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-407)
文摘Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size groups, different water contents, various freeze-thaw cycles, and various freezing temperatures. The results showed that, when at suitable water content, aggregate stability was enhanced, aggregate sta-bility will be disrupted when moisture content is too high or too low, especially higher water content. Temperature also had a significant ef-fect, but moisture content determined the suitable freezing temperatures for a given soil. Water-stable aggregate （WSA〉0.5）, the total aggre-gate content, and mean weight diameter decreasing with the freeze-thaw cycles increase, reached to 5 percent significance level. The reason for crumbing aggregates is the water and air conflict, thus raising the hypothesis that water content affects the aggregate stability in the process of freezing and thawing.
基金supported by the National Natural Science Foundation of China (No. 41371092)the Scientific Research Foundation for Returned Overseas Students+1 种基金the Education Department of Henan Province Science and Technology Research projects (No.14B170007)the doctoral foundation of Henan Polytechnic University (No. 648349)
文摘It is generally known that soil pollution poses a terrible hazard to the environment, but the present techniques of contaminated soil remediation cannot control this growing threat. This paper compares the pollutant extraction efficiency of traditional pumping and treating, which is a typical washing technology for the remediation of contaminated soils, with methods that utilize freeze-thaw cycles. In the soil freezing process, water shifts from unfrozen soils to the freezing front, and the permeability of soil will be enhanced under certain temperature gradients and water conditions. Therefore, this paper discusses the purification of contaminated soil through freeze-thaw action. We conducted a cleansing experiment on clay and silica sand infused with NaCl（simulation of heavy metals） and found that the efficiency of purification was enhanced remarkably in the latter by the freeze-thaw action. To assess the effective extraction of DNAPLs in soil, we conducted an experiment on suction by freezing, predicated on the different freezing points of moisture and pollutants. We found that the permeability coefficient was significantly increased by the freezing-thawing action, enabling the DNAPL contaminants to be extracted selectively and effectively.
基金supported by the CAS Knowledge Innovation Key Project (Grant No. KZCX2-YW-330)the National Science Fund FosteringTalents in Basic Research to Glaciology and Geocryology (Grant No. J0630966).
文摘Hydrate formation and dissociation processes are always accompanied by water migration in porous media, which is similar to the ice. In our study, a novel pF-meter sensor which could detect the changes of water content inside sand was first applied to hydrate formation and dissociation processes. It also can study the water change characteristics in the core scale of a partially saturated silica sand sample and compare the differences of water changes between the processes of formation and dissociation of methane hydrate and freezing and thawing of ice. The experimental results showed that the water changes in the processes of formation and dissociation of methane hydrate were basically similar to that of the freezing and thawing of ice in sand. When methane hydrate or ice was formed, water changes showed the decrease in water content on the whole and the pF values rose following the formation processes. However, there were very obvious differences between the ice thawing and hydrate dissociation.
基金financially supported by the National Natural Science Founda-tion of China(Grant number:42371107)the Project Supported by State Key Laboratory of Earth Surface Processes and Resource Ecology(2022-TS-03)
文摘Background Seasonal freeze-thaw(FT)processes alter soil formation and cause changes in soil microbial communi-ties,which regulate the decomposition of organic matter in alpine ecosystems.Soil aggregates are basic structural units and play a critical role in microbial habitation.However,the impact of seasonal FT processes on the distribution of microbial communities associated with soil pores in different aggregate fractions under climate change has been overlooked.In this study,we sampled soil aggregates from two typical alpine ecosystems(alpine meadow and alpine shrubland)during the seasonal FT processes(UFP:unstable freezing period,SFP:stable frozen period,UTP:unstable thawing period and STP:stable thawed period).The phospholipid fatty acid(PLFA)method was used to determine the biomass of living microbes in different aggregate fractions.Results The microbial biomass of 0.25–2 mm and 0.053–0.25 mm aggregates did not change significantly dur-ing the seasonal FT process while the microbial biomass of>2 mm aggregates presented a significant difference between the STP and UTP.Bacterial communities dominated the microbes in aggregates,accounting for over 80%of the total PLFAs.The microbial communities of soil aggregates in the surface layer were more sensitive to the sea-sonal FT process than those in other soil layers.In the thawing period,Gram positive bacteria(GP)was more dominant.In the freezing period,the ratio of Gram-positive to Gram-negative bacterial PLFAs(GP/GN)was low because the enrichment of plant litter facilitated the formation of organic matter.In the freezing process,pores of 30–80μm(mesopores)favored the habitation of fungal and actinobacterial communities while total PLFAs and bacterial PLFAs were negatively correlated with mesopores in the thawing process.Conclusions The freezing process caused a greater variability in microbial biomass of different aggregate fractions.The thawing process increased the differences in microbial biomass among soil horizons.Mesopores of aggregates supported the habitation of actinobacterial and fungal communities while they were not conducive to bacterial growth.These findings provide a further comprehension of biodiversity and accurate estimation of global carbon cycle.
基金This work was supported by the National Natural Science Foundation of China(Nos.22176199,21806173,and 42192571)the Jinan University and Institute Innovation Team Project(No.2021GXRC061).
文摘Freeze-induced acceleration of I–oxidation and the consequent iodination of dissolved organic matter(DOM)contribute to the formation of organoiodine compounds(OICs)in cold regions.The formed OICs may be a potentially important source of risk and are very closely with the environment and human health.Herein,we investigated the acceleration effects of the freeze process on I–oxidation and the formation of OICs.In comparison to reactive iodine species(RIS)formed in aqueous solutions,I–oxidation and RIS formation were greatly enhanced in frozen solution and were affected by pH,and the content of I–and O_(2).Freeze-thaw process further promoted I–oxidation and the concentration of RIS reached 45.7μmol/L after 6 freeze-thaw cycles.The consequent products of DOM iodination were greatly promoted in terms of both concentration and number.The total content of OICs ranged from 0.02 to 2.83μmol/L under various conditions.About 183–1197 OICs were detected by Fourier transform ion cyclotron resonance mass spectrometry,and more than 96.2%contained one or two iodine atoms.Most OICs had aromatic structures and were formed via substitution and addition reactions.Our findings reveal an important formation pathway for OICs and shed light on the biogeochemical cycling of iodine in the natural aquatic environment.
基金the Strategic Priority Research Pro-gram of Chinese Academy of Sciences(Grant No.XDA20100103)Natural Science Foundation of China(Grant No.41971091).
文摘The coupling effects and mechanisms of water,heat,and salt in frozen soils are considered to be one of the core scientific issues in frozen soil studies.This study was based on in situ observation data of active layer soil volumetric water content(VWC),temperature,and bulk electrical conductivity(EC)obtained at an alpine meadow site from October 2016 to November 2019.The site is located in the headwater area of the Yellow River(HAYR).We analyzed the synergetic variations of active layer soil VWC,temperature,and bulk EC during the freeze and thaw processes and discussed the underlying mechanisms.When the thaw process occurred from 10 to 80 cm depths,the VWC and bulk EC at a 10 cm depth showed syn-chronous high-frequency fluctuations and both increased linearly.The linear decreasing rate of the VWC(bulk EC)at an 80 cm depth in the freeze depths between 0 and 40 cm was 2(1.6e2.3)times that of the VWC(bulk EC)at an 80 cm depth in the freeze depths occurring 0e10 cm.As soil temperature decreased in the frozen layer,unfrozen water content(bulk EC)decreased nonlinearly along with the absolute value of soil temperature(|T|),following a power(logarithmic)function.This study provided data that partly elucidate the interactions among permafrost,meadow,and ecohydrological processes in the HAYR.Also,our results can be used as a scientific basis for decision making on the protection and restoration of alpine grasslands,as well as for soil salinization studies.
