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1.
The paper by W. H. Zhou and J. H. Yin includes a problem regarding the pull-out resistance of a soil nail within dilatant soils. They calculate the pull-out force due to soil dilatancy using cylindrical expansion in an elastic medium. However, the soil in the vicinity of the nail experiences significant local softening behavior. This discussion indicates another method for calculating the normal stress due to soil dilatancy.  相似文献   

2.
The goal of the paper was to determine the activity of 137Cs and 40K radionuclides as well as heavy metals Zn, Cr, Pb in soil samples taken from the Tatra National Park in the south of Poland. The samples were obtained as cores (10 cm in diameter) from the top 10-cm layer of the soil. Each sample was divided into three subsamples (a, b and c), where a was the subsample closest to the surface and c was the deepest one. Activity of the radionuclides was determined by means of gamma spectrometry, while analysis of heavy metals was performed (after microwave digestion) using atomic absorption spectrometry technique. The highest activity of cesium-137 was detected (5112 ± 120 Bq kg?1) in the “a” layer of the core with the peak concentration of cesium-137 (14,452 ± 278 Bq m?2) in the whole soil core. The highest detected concentration of heavy metals was: Zn—52.8 ± 4.4 mg kg?1, Pb—260.1 ± 9.4 mg kg?1, Cr—52.8 ± 4.4 mg kg?1, respectively. Cluster analysis and principal component analysis were used to examine the obtained data. Application of statistical analysis tools allowed specifying the interdependencies between the examined variables.  相似文献   

3.
Electrical conductivity of saturated soil extracts (ECe) in three reclaimed tideland (RTL) soils on the west coast of Korea decreased with time since reclamation, indicating natural desalinization through leaching of salts by precipitation water. Soil N concentration increased with decreasing ECe. With the increase in soil N concentration, the δ15N decreased, likely caused by the input of 15N-depleted N sources. As N2-fixing plant species were found in the oldest RTL, atmospheric N2 fixation likely contributed to the increase in soil N concentration in the oldest RTL. Negative δ15N (−7.1 to −2.0‰) of total inorganic N (NH4 ++NO3 −) and published data on N deposition near the study area indicate that atmospheric N deposition might be another source of N in the RTLs. Meanwhile, the consistently negative δ15N of soil NO3 − excluded N input from chemical fertilizer through groundwater flow as a potential N source, since NO3 − in groundwater generally have a positive δ15N. The patterns of δ15N of NH4 + (+2.3 to +5.1‰) and NO3 − (−9.2 to −5.0‰) suggested that nitrification was an active process that caused 15N enrichment in NH4 + but denitrification was probably minimal which would otherwise have caused 15N enrichment in NO3 −. A quantitative approach on N budget would provide a better understanding of soil N dynamics in the studied RTLs.  相似文献   

4.
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5.
Salt-rich soft soils have not only general characteristics of common soft soils, but also contain high contents of Mg2+, Cl?, and SO42?, which have negative effects on deep mixing method using cement to treat soft soils. Laboratory and field tests were conducted to investigate the effects of changing cement incorporating ratio, water content, cement mixing ratio, and contents of Mg2+, Cl?, and SO42? on the unconfined compressive strength of the salt-rich soil–cement. The microstructure of soil–cement and the mechanism for the strength change of salt-rich soil–cement were investigated using X-ray diffraction, scanning electronic microscopy (SEM), and backscattered diffraction technology. It was found that an increase of cement incorporating ratio enhanced the strength of soil–cement but reduced its strength when water is added. Different amounts of Mg2+, Cl?, and SO42? not only caused the difference in the microstructures of salt-rich soil–cement but also influenced the soil–cement strength.  相似文献   

6.
Xu  Wen-Jie  Zhang  Hai-Yang 《Acta Geotechnica》2022,17(9):3765-3782
Acta Geotechnica - Composed of large rock blocks and fine soil particles, the physical and mechanical behaviors of soil–rock mixtures (S–RMs) are quite complex. To develop insight into...  相似文献   

7.
Char and soot （black carbon, BC） are highly surface-active materials that can play an important role in contaminant fate and bioavailability in soils and sediments. This report summarizes our research on the influence of adsorbate structure and BC properties on adsorption of organic compounds, and the possible attenuation of BC surface activity by humic substances in the environment. The BC was a maple wood char formed at 400 ℃ in air and under other conditions. The solutes were polar and apolar aromatic compounds. The following points will be discussed. （1） By comparing adsorption to nonporous graphite, it was shown that molecular sieving effects （steric restriction） in the char micropore system occur in the order of increasing substitution on the benzene ring and in the order of increasing fused ring size. （2） By accounting for hydrophobic and steric effects it was shown that aromatic rings substituted with strongly pi-electron-accepting functional groups, such as nitro, undergo pi-pi electron donor-acceptor （EDA） interactions with the pi-donor polyaromatic （graphene） surface of the char. The free energy of adsorption due to pi-pi EDA interactions correlated with the free energy of molecular complexation in chloroform with model compounds representing the graphene surface （napthalene, phenanthrene, pyrene）. （3） A series of chars were prepared of different polarity （O content） but similar surface area and pore size distribution by varying temperature and atmosphere. Single- and bi-solute experiments showed that polar interactions with surface O are not a significant driving force for adsorption of polar compounds. Rather, surface O attracts water molecule clusters that inhibit adsorption of both polar and nonpolar compounds by competition. （4） Aging of char particles in a soil-water suspension strongly reduced char SA and sorption of added benzene. Studies were conducted with dissolved humic （HA） acid, HA-char co-precipitates, Ala＋-HA-char co-flocculates, and soybean oil representing humic lipid components.  相似文献   

8.
Zhang  Ze  Huang  Canjie  Jin  Huijun  Feng  Wenjie  Jin  Doudou  Zhang  Guike 《Acta Geotechnica》2022,17(10):4377-4393
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9.
During the last century, several lead mines and a metal smelter were in production in the Upper Ribeira Valley, southeastern Brazil. After fifty years of activity, the refinery was shut down in November 1995 and, thereafter the last mines in production were closed. Since 1998, a multidisciplinary research group has carried out an ambitious investigation among the population of five municipalities in the Ribeira Valley （sampled population of 472 children and 523 adults） to assess the human exposure to lead. The highest blood lead levels were found among the population of two villages in the vicinity of the smelter where soil and indoor-dust are highly contaminated. During the present study, the lead contents of several food species that are part of local population diet were investigated. Greens, vegetables, corn, chicken eggs and cow milk, were sampled in two occasions, July 2004 and February 2005. The analytical procedures included burning of organic matter, pre-concentration of lead and, finally, determination by AAS using background correction. The quantification limit was 0.05 μg/g Pb. Soil samples were also collected and analyzed by X-ray fluorescence spectroscopy with a quantification limit of 2 μg/g Pb. The results are very impressing since 100% of greens, vegetables and eggs yielded lead concentrations exceeding the upper limits established by Brazilian regulations whereas milk and maize samples presented lead contents below the regulated limit of 0.05 μg/g Pb. Lead concentrations in soil varied between 156 and 1292 μg/g Pb, resembling the results of previous studies and far exceeding the threshold of 200 μg/g Pb indicated as the intervention value. Lead contents in some species vary consistently with lead concentrations in soils, however, other factors may account for the bioavailability of lead and its intake by plants, like the soil pH, its cationic exchange capacity, clay and organic matter contents, characteristics of the plant species itself, climate, among others.  相似文献   

10.
In recent years,more and more attention has been paid to the problem of the cryosphere changes on the Tibetan Plateau,and it has gradually become a hot issue for scholars. Known as the“water tower of Asia”,the Tibetan Plateau is the source of many major rivers in Asia. Under the combined influence of climate change and human activities,water resources on the Tibetan Plateau have undergone profound changes,especially soil water,as an important component of water resources,which plays an important role in regulating vegetation and crop growth,rainfall and runoff. However,global warming leads to the degradation of permafrost and seasonal⁃ ly frozen soil,which affects the original water cycle process and the spatial and temporal pattern of water re⁃ sources by changing the properties of soil water storage and water transport. In the Tibetan Plateau,where there are few data,it is difficult to directly study the soil water cycle process under freezing-thawing by using original data. Therefore,it is an important means to simulate the variation characteristics of soil water and temperature under freezing-thawing in seasonally frozen soil regions of the Tibetan Plateau by using coupling model of soil water and heat. Aiming at the key problem of the difference of soil temperature and moisture characteristics in typical seasonally frozen soil regions under different meteorological conditions,this paper simulated the charac⁃ teristics of soil moisture and temperature change in Maqu,Naqu（Nagqu）and Shiquanhe from 2017 to 2018 by using SHAW（Simultaneous Heat and Water）model and three soil moisture characteristic curve models. The simulation effect and variation characteristics of soil moisture and temperature under different meteorological conditions were analyzed,and the influence of soil moisture characteristic curve model on the simulation effect was studied. The results show that SHAW model can well simulate the temporal variation and vertical distribu⁃ tion of soil temperature and moisture under different meteorological conditions. The simulation effect of soil tem⁃ perature is better than that of soil moisture. The average NSE,R2 and RMSE of soil temperature are 0. 88,0. 96 and 2. 20 ℃,respectively. The mean NSE,R2 and RMSE of soil moisture are 0. 60,0. 72 and 0. 03 m3·m-3,respec⁃ tively. In terms of different meteorological conditions,the simulation effect of soil temperature in relatively dry region was significantly better than that in humid region,while the simulation effect of soil water in relatively hu⁃ mid region was significantly better than that in arid region. From different depths in soil,the simulation effect of soil temperature decreases gradually with the increase of depth,while the simulation effect of soil moisture in the middle and lower layers is better than that in the surface layer. From the view of different soil moisture character⁃ istic curve models,different soil water characteristic curve models have no significant effect on soil temperature simulation effect,but there are significant differences in soil moisture simulation effect. In addition,there are great differences and uncertainties in simulating soil temperature and moisture in different freezing-thawing stag⁃ es. With the increasing trend of climate warming,permafrost and seasonally frozen soil on the Tibetan Plateau may continue to degrade,may change the current water resources pattern,resulting in frequent extreme weather events. Therefore,from the perspective of numerical simulation,this paper verified the applicability of soil moisture and heat coupling model in soil temperature and moisture simulation under different meteorological con⁃ ditions,revealed the influence of precipitation and temperature on soil temperature and moisture simulation at different depths in seasonally frozen soil regions,and analyzed the differences in simulation effects of different soil moisture characteristic curve models. The results provide reference for the study of soil water resources vari⁃ ation under freezing-thawing conditions. © 2023 Chinese Journal of General Practitioners. All rights reserved.  相似文献   

11.
The biogeochemical migration of iodine in soil and its effect factors were studied by the isotope tracer (125I) and experiments of leaching and absorption by Chinese cabbage to iodine under simulated condition. The results show that the quantities of tran…  相似文献   

12.
Acta Geotechnica - Soil–structure interfaces typically exhibit a shear behavior that is independent of the direction of relative displacement due to symmetry in the solid material's...  相似文献   

13.
Through systematic sampling and analysis of water and soil in the planning area of Langfang City, employing national environmental quality standards, the qualities of groundwater and surface-water was overall evaluated. On the whole, the quality of deep-level groundwater was better and hazardous substances were not superstandard, F is higher, Fe and Mg was superstandard in several sites. The quality of shallow groundwater was general worse and COD, Fe, Mn, NH4^＋-N, F, total hardness, total dissolved solids etc. overstep drinking water standard; the quality of surface water was worst and many indices were evidently higher, which was very worst in the east of downtown. Main pollution way of water body was lixiviation type of primary pollution groundwater and infiltration type of secondary pollution groundwater. Environmental quality assessment of plough layer soil indicated that it was better in the northwest and worse in the southeast, furthermore from Xiwu, Daguanzhang, Zhougezhuang to Pengzhuang, Dazhaolin and the north of Jingshan railroad, the environmental quality is worst.  相似文献   

14.
Soil organic matter (SOM) is the important phase for sorption of hydrophobic organic contaminants (HOCs) by soils and sediments. A linear partition model was invoked for mechanistically and quantitatively describing the sorption equilibria as partitioning…  相似文献   

15.
Cai  Guoqing  Zhou  Annan  Liu  Yi  Xu  Runze  Zhao  Chengang 《Acta Geotechnica》2020,15(12):3327-3341
Acta Geotechnica - This paper presents an experimental investigation of the soil water retention curve (SWRC) and volume change curve over a large suction range (0–286.7 MPa), and...  相似文献   

16.
To date our knowledge is limited with regard to the responses of ethylene and methane consumption by forest soils to tree species and soil types, and to the effect of presence of ethylene on atmospheric methane consumption. The soils at depths from tropical and temperate forests in China were used to study the responses of ethylene and methane consumption to tree species and soil types. The ethylene and methane consumption by soils beneath each forest floor was measured under the same oxic conditions, along with main properties of forest soils. The accumulation of ethylene was studied in the soil slurry （soil/water, 1/2.5）. In temperate soils under spruce and birch forests, maximal consumption rates of ethylene and methane were observed in the 2.5-5.0 cm and 5.0-7.5 cm soil layers, respectively （P〈0.05）. However, a maximal consumption of both occurred in the 0-2.5 cm soil layer under temperate Korean pine forest （P〈0.05）. Contrary to temperate forest soils, there was a significant lower consumption of ethylene and methane in tropical forest soils at less than 20 cm depths under a seasonal rainforest and secondary rubber forest （P〈0.05）. Hence, the potential of ethylene and methane consumption in the 0-20 cm soil profile was variable with tree species and soil types. According to ethylene formation in the soil slurry, there was greater accumulation of ethylene in the 0-2.5 cm soil under temperate forests than under tropical forests, and its accumulation under spruce and birch forests was more than under Korean pine forest （P〈0.05）. The presence of extrinsic ethylene can significantly inhibit the consumption of atmospheric methane by forest soils.  相似文献   

17.
Due to the persistent nature of DDT, a persistent organic pollutant and its adverse environmental and health impacts, the present study was undertaken to examine the residual DDT in and around DDT manufacturing factory in Amman Gharh, Nowshera, NWFP. The factory was established in 1963 and remained in operation till 1994. Composite samples of soil, sediments and water were collected in and around the factory area, nearby DDT stores, main factory drain leading to river and nearby villages. Standard procedures were used for the collection, transportation and storage of samples for analysis. Physical parameters for the collected water samples measured were temperature, pH and conductance. Extraction of each sample for DDT analyses was carried out in triplicates using soxhlet extraction apparatus. The extract was transferred to well washed, clean; dry glass vial, sealed and put in the refrigerator. Gas Chromatograph with electron capture detector and capillary column was used for analysis. DDT in the samples was identified on the basis of their retention time and quantified on the basis of peak areas. It is evident from the analytical data obtained in the present study that both water and soil in and around the factory area are still contaminated with DDT, despite the closure of the factory since the past few years.  相似文献   

18.
1 IntroductionThe term“Environmental Geochemical Baseline(EGB)”first appeared in the International Geochemi-cal Mapping Program (IGCP259) and the InternationalGeochemical Baseline Program (IGCP360) of Interna-tional Geography Contrast Program. The defin…  相似文献   

19.
The aim of this research is to study the change of P and N contents of the surface runoff and subsurface flow caused by rainfall events, from the watershed till the stream. Samples were taken and analyzed from the surface runoff water after each rainfall …  相似文献   

20.
As the most important part of the global carbon cycle,soil carbon pool is the largest carbon pool in terrestrial ecosystems. Soil carbon pool in permafrost regions is the most sensitive carbon pool to climate change. Weak climate change will have a huge impact on the organic carbon production in the shallow soil,and then affect the regional landscape and ecology. As an indicator reflecting the antioxidant capacity of soil organic carbon,oxidation stability affects the quantity and quality of soil organic carbon,and its variation has a certain regularity in the alpine permafrost region under the influence of climatic factors. In order to explore the distribution characteristics of soil organic carbon and its oxidation stability in frozen soil,based on the experimental data and the climatic data from 2011 to 2019,the random forest model was used to conduct multi-factor digital mapping on soil organic carbon content,soil organic carbon components with different oxidation difficulty degrees,and soil organic carbon oxidation stability coefficient and environmental variables（average annual precipitation,average annual sunshine hours,average annual air temperature,and altitude）and analyze the controlling factors. The results showed that the model had an interpretation degree of more than 54% for the shallow soil organic carbon in frozen soil area of Three River Source Region,and the digital mapping could reflect the distribution of soil organic carbon well. Soil organic carbon was mainly affected by precipitation and sunshine duration,and temperature took second place. The spatial distribution of components with different oxidation difficulty is different,but the oxidation stability has the distribution characteristics of high in the north and low in the south. Cold and dry are conducive to improving the oxidation stability of organic carbon in shallow soil of frozen soil area. © 2022 Science Press (China).  相似文献   

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