scholarly journals Lead and Chromium Immobilization Process Subjected to Different Freeze-Thaw Treatments in Soils of the Northeastern Qinghai-Tibet Plateau

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Leiming Li ◽  
Jun Wu
Keyword(s):  
Water Content ◽  
Tibet Plateau ◽  
Isothermal Adsorption ◽  
Adsorption And Desorption ◽  
Freeze Thaw ◽  
Soil Adsorption ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Qinghai Tibet Plateau ◽  
Insight Into

The freeze-thaw cycle is one of the important processes that affected heavy metal behaviors in soil. However, information regarding the adsorption and desorption behavior of heavy metals in soils under different freeze-thaw conditions is relatively less. Therefore, different freeze-thaw conditions including unfrozen, 15 freeze-thaw cycles at 60% water content, and 15 freeze-thaw cycles at 100% water content were investigated. Then the adsorption and desorption behaviors of Pb and Cr in freeze-thaw soils were studied. Results showed the Pb and Cr adsorption amount mostly decreased with increasing water-soil ratio, and the soil performance of Pb and Cr adsorption at same water-soil ratios showed variation under different freeze-thaw conditions. The Pb isothermal adsorption was higher for most freeze-thaw treatments compared to the control. The soil performance of Cr isothermal adsorption showed variation under different freeze-thaw conditions. Most electrostatic binding of Pb and Cr were stronger under unfrozen and freeze-thaw conditions than unfrozen conditions. Most Pb and Cr adsorption kinetics patterns of freeze-thaw treated soils were rapid than unfrozen conditions. These results implied that freeze-thaw cycles could change the soil adsorption and desorption patterns of Pb and Cr. Therefore, further studies are urgently needed to investigate Pb and Cr immobilization mechanisms in soils during freeze-thaw cycles. Hence, these findings provided useful information on Pb and Cr immobilization process in soils that underwent freeze-thaw cycles to offer an additional insight into predicting Pb and Cr behaviors in cold and freezing environments.

scholarly journals Soil respiration of alpine meadow is controlled by freeze–thaw processes of active layer in the permafrost region of the Qinghai–Tibet Plateau

2020 ◽  
Vol 14 (9) ◽  
pp. 2835-2848
Author(s):  
Junfeng Wang ◽  
Qingbai Wu ◽  
Ziqiang Yuan ◽  
Hojeong Kang
Keyword(s):  
Soil Respiration ◽  
Active Layer ◽  
Alpine Meadow ◽  
Tibet Plateau ◽  
Permafrost Region ◽  
Permafrost Degradation ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Qinghai Tibet Plateau

Abstract. Freezing and thawing action of the active layer plays a significant role in soil respiration (Rs) in permafrost regions. However, little is known about how the freeze–thaw processes affect the Rs dynamics in different stages of the alpine meadow underlain by permafrost in the Qinghai–Tibet Plateau (QTP). We conducted continuous in situ measurements of Rs and freeze–thaw processes of the active layer at an alpine meadow site in the Beiluhe permafrost region of the QTP and divided the freeze–thaw processes into four different stages in a complete freeze–thaw cycle, comprising the summer thawing (ST) stage, autumn freezing (AF) stage, winter cooling (WC) stage, and spring warming (SW) stage. We found that the freeze–thaw processes have various effects on the Rs dynamics in different freeze–thaw stages. The mean Rs ranged from 0.12 to 3.18 µmol m−2 s−1 across the stages, with the lowest value in WC and highest value in ST. Q10 among the different freeze–thaw stages changed greatly, with the maximum (4.91±0.35) in WC and minimum (0.33±0.21) in AF. Patterns of Rs among the ST, AF, WC, and SW stages differed, and the corresponding contribution percentages of cumulative Rs to total Rs of a complete freeze–thaw cycle (1692.98±51.43 g CO2 m−2) were 61.32±0.32 %, 8.89±0.18 %, 18.43±0.11 %, and 11.29±0.11 %, respectively. Soil temperature (Ts) was the most important driver of Rs regardless of soil water status in all stages. Our results suggest that as climate change and permafrost degradation continue, great changes in freeze–thaw process patterns may trigger more Rs emissions from this ecosystem because of a prolonged ST stage.

scholarly journals Effect of freeze-thaw cycles on soil physicochemical properties and fractions of Pb and Cr in the northeastern Qinghai-Tibet Plateau

2021 ◽  
pp. geochem2021-029
Author(s):  
Leiming Li ◽  
Jun Wu ◽  
Jian Lu ◽  
Xiuyun Min
Keyword(s):  
Physicochemical Properties ◽  
Water Content ◽  
Environmental Issues ◽  
Tibet Plateau ◽  
Control Treatment ◽  
Soil Physicochemical Properties ◽  
Content Type ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Qinghai Tibet Plateau

Simulation experiments were conducted by using soils in the northeastern Qinghai-Tibet Plateau to explore the effects of freeze-thaw cycles on soil physicochemical properties, Pb and Cr distribution and fraction transformation. Soils were incubated at -15 ℃ for 24 h and at 5℃ for 24 h to complete a freeze-thaw cycle. The soil physicochemical properties and the fractions of Pb and Cr in soils were analyzed after serial freeze-thaw treatments. The results showed that different freeze-thaw cycles and water content affected soil physicochemical properties and fractions of Pb and Cr in soils to some extent. The cation exchange capacity increased significantly in agricultural and pastoral soils after five freeze-thaw cycles. The sand proportion of soil in an urban area decreased at 60 freeze-thaw cycles. Freeze-thaw cycles did not change the functional groups and mineral constituents of soils. The infrared peaks of soils with different freeze-thaw conditions were very similar. The freeze-thaw treatment influenced the mobility, chemical fractions of Pb and ecological risk in most of soils. The exchangeable Pb in agricultural and pastoral area increased from 0.19% to 1.52%/0.90% after 5/10 freeze-thaw cycles with 60% water content. The ecological values of Pb in urban soil were 8.32%/7.38% higher at 10/15 freeze-thaw cycles compared with the control treatment. Hence, these findings provided useful information on physicochemical properties and fraction transformation of Pb and Cr in soils undergoing freeze-thaw cycles to offer an additional insight on Pb and Cr behaviors in cold and freezing environments.Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues

Study on Influence of Freeze-Thaw Cycles on the Physical-Mechanical Properties of Loess

2012 ◽  
Vol 442 ◽  
pp. 286-290
Author(s):  
Gui Quan Bi
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Water Distribution ◽  
Early Stage ◽  
Frozen Soil ◽  
Dry Density ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Filling Water

Loess foundations in seasonally frozen soil region are subject to severe effect of freeze-thaw cycles. This often results in water redistribution and structure weakening. So it is very important to study the physical-mechanical properties of loess under freeze-thaw cycles. In this paper, systematic study was carried out using freeze-thaw cycle machine. The impacts of freeze-thaw cycles on the physical-mechanical properties of loess including deformation, water distribution and dry density under the condition of filling water to loess samples were investigated. The results proved that the freeze-thaw cycles can increase the water content gradually from the bottom to the top in the loess samples under water supplied condition. The water content gradient reaches maximum at the freeze-thaw interface. The loess samples deform sharply at the early stage of the freeze-thaw cycles and then reach a stable status. The freeze-thaw cycles decrease the dry density of the loess samples gradually. The dry density at the top is lower than that at the bottom, due to more severe freeze-thaw effect at the top of the samples.

scholarly journals The Impacts of Freeze-thaw Cycles on Saturated Hydraulic Conductivity and Microstructure of Saline-alkali Soils

2021 ◽  
Author(s):  
Wenshuo Xu ◽  
Kesheng Li ◽  
Longxiao Chen ◽  
Weihang Kong ◽  
Chuanxiao Liu
Keyword(s):  
Hydraulic Conductivity ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Water Content ◽  
Size Distribution ◽  
Soil Permeability ◽  
Freeze Thaw ◽  
Alkali Soil ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

Abstract Study on the microscopic structure of saline-alkali soil can reveal the change of its permeability more deeply. In this paper, the relationship between permeability and microstructure of saline-alkali soil with different dry densities and water content in the floodplain of southwestern Shandong Province was studied through freeze-thaw cycles. A comprehensive analysis of soil samples was conducted using particle-size distribution, X-Ray diffraction, Freeze-Thaw cycle test, saturated hydraulic conductivity test and mercury intrusion porosimetry. The poor microstructure of soil is the main factor that leads to the category of micro-permeable soil. The porosity of the local soil was only 6.19–11.51%, and ultra-micropores (< 0.05 µm) and micropores (0.05-2 µm) dominated the pore size distribution. Soil saturated water conductivity was closely related to its microscopic pore size distribution. As the F-T cycles progressed, soil permeability became stronger, with the reason the pore size distribution curve began to shift to the small pores (2–10 µm) and mesopores (10–20 µm), and this effect was the most severe when the freeze-thaw cycle was 15 times. High water content could promote the effects of freeze-thaw cycles on soil permeability and pore size distribution, while the increase of dry density could inhibit these effects. The results of this study provide a theoretical basis for the remediation of saline-alkali soil in the flooded area of Southwest Shandong.

Nitrous oxide production and sources in response to a simulated fall-freeze-thaw cycle

2020 ◽  
Author(s):  
Sisi Lin ◽  
Guillermo Hernandez Ramirez
Keyword(s):  
Climate Change ◽  
Water Content ◽  
Soil Water ◽  
High Water ◽  
Organic N ◽  
High Water Content ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Water Contents

&lt;p&gt;Thaw-induced N&lt;sub&gt;2&lt;/sub&gt;O emissions have been shown to account for 30-90% of N&lt;sub&gt;2&lt;/sub&gt;O emissions in agricultural fields. Due to the climate change, increased precipitatio is expected in fall and winter seasons for certain regions. As a result, this would in turn enhance the thaw-induced N&lt;sub&gt;2&lt;/sub&gt;O emissions and aggravate climate change. A mesocosm study was conducted to investigate N&lt;sub&gt;2&lt;/sub&gt;O production and sources from soils under elevated soil moisture contents in response to a simulated fall-freeze-thaw cycle. Treatments included two levels of N addition (urea versus control) and two different management histories [with (SW) and without (CT) manure additions]. Our results showed that at least 92% of the N&lt;sub&gt;2&lt;/sub&gt;O emissions during the study were produced during the simulated thawing across all treatments. The thaw-induced N&lt;sub&gt;2&lt;/sub&gt;O emissions increased with increasing soil water content. The fall-applied urea increased the soil-derived N&lt;sub&gt;2&lt;/sub&gt;O emissions during thawing, indicating an excessive mineralization of soil organic N. Compared to the CT soils, the SW soils induced more soil-derived N&lt;sub&gt;2&lt;/sub&gt;O emissions. This could be because the SW soil had more easily decomposable organic matter which was likely due to historical manure additions. Regarding to the daily primed N&lt;sub&gt;2&lt;/sub&gt;O fluxes, different soil water contents impacted the dynamics of daily priming effect. At the high water content, the soils experienced a shift in daily primed N&lt;sub&gt;2&lt;/sub&gt;O fluxes from positive to negative and eventually back to positive throughout the simulated thawing, while the soils at lower water contents underwent positive primed fluxes in general. The shift in daily primed fluxes was probably driven by the preference of soil microbes on the labile N substrates. When the microbes switched from easily to moderately decomposed substrates (e.g., from dissolved organic N to plant residuals), they started to uptake inorganic N from the soil due to a relatively high C:N ratio of plant residuals. Therefore, a net N immobilization and negative primed N&lt;sub&gt;2&lt;/sub&gt;O production occur in the short term in the soils at the high water content.&lt;/p&gt;

scholarly journals Study on Soil-Water Characteristics of Expansive Soil under the Dry-Wet Cycle and Freeze-Thaw Cycle considering Volumetric Strain

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Lisi Niu ◽  
Aijun Zhang ◽  
Jiamin Zhao ◽  
Wenyuan Ren ◽  
Yuguo Wang ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Expansive Soils ◽  
Volumetric Strain ◽  
Expansive Soil ◽  
Volumetric Water Content ◽  
Dry Density ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

This paper targets the expansive soils in Heilongjiang and Ankang to explore the influence of initial dry density, dry-wet cycle, and freeze-thaw cycle on the soil-water characteristics. The centrifuge method was used to obtain the soil-water characteristic curves (SWCCs) with different conditions. The volumetric strain of SWCC was modified based on the shrinkage test, and the corresponding fitting equations considering different factors were established. The results show that the volumetric water content is modified to consider the volume shrinkage effect of expansive soil, and the modification is more obvious in the high matric suction range. The smaller the initial dry density is, the worse the water-holding capacity of the sample is, and the smaller the air intake value is. The greater the time of the dry-wet cycle is, the greater the saturated volumetric water content of the sample is, and the corresponding water-holding capacity is significantly reduced. When the dry-wet cycle increases to a certain extent, the structure becomes stable. With the increase of the freeze-thaw cycle, the saturated volumetric water content first decreases and then increases. Similarly, after several times of the freeze-thaw cycle, the structure is basically stable. The fitted Gardner model equations under different conditions were proved to be able to describe the SWCCs of the two targeted expansive soils.

Effect of Freeze-Thaw Action on Phosphorus Adsorption and Desorption in Forest Wetland Soils at High Latitudes

2013 ◽  
Vol 316-317 ◽  
pp. 487-492
Author(s):  
Yi Bin Ren ◽  
Nan Qi Ren
Keyword(s):  
Soil Phosphorus ◽  
Phosphate Solution ◽  
Freezing And Thawing ◽  
Obvious Effect ◽  
Phosphorus Adsorption ◽  
Adsorption And Desorption ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Experimental Subjects

To clear the effect of freezing and thawing on the soil phosphorus adsorption and desorption of northeast China high latitude forest wetland, the change of soil phosphorus elements after five complete freeze-thaw cycles was analyzed with Wuyiling National Wetland as experimental subjects. Result shows that the soil phosphates desorption increased after influenced by five complete freezing and thawing. Soil sample which initial phosphates concentration is 40、80、240 mg/L reached minimum value after three freeze-thaw cycle and then increased. Compared to the without freeze-thaw soil, phosphorus adsorption capacity of different initial concentrations of phosphate solution samples was increased after five freeze-thaw cycles indicating that freeze-thaw cycle has obvious effect on soil phosphorus adsorption and desorption.

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