Shrinkage of clay soils: A statistical correlation with other soil properties

The hypothesis that the shrinkage of soils is greater when expansible minerals are dominant was tested with 63 soils containing between 40 and 64% clay. Shrinkage between pF 2 and 4 (0.1 and 10 bar) correlated significantly with the expansible mineral content (measured by ethylene glycol retention) for remoulded but not for dried and rewetted specimens. Shrinkage between pF 4 and 6 (10 and 10³ bar) was strongly correlated with the expansible mineral content for both kinds of specimens. The physical significance of the results is discussed, and it is concluded that interlamellar shrinkage is not the principal component of bulk shrinkage.     

Sorption behavior of prochloraz in different soils.

The sorption behavior of the imidazole fungicide prochloraz [PCZ; N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl]imidazole-1-carboxamide] was studied in batch experiments with different soils. The soil organic matter content was found to control the amount sorbed by different soils. K(d) values ranged from 56 +/- 0 to 552 +/- 10 (mean = 221 +/- 5) and K(OC) values from 7273 +/- 0 to 16250 +/- 1300 (mean = 11829 +/- 303). As calculated from a linear regression of K(d) versus %OC, K(OC) was 12900 +/- 1300. Additionally, the pH value of the soil had considerable influence on the sorption of the weakly basic PCZ (pK(a) = 3.8), giving rise to stronger sorption at lower pH. K(d) values determined on pH-modified soils confirmed the pH dependency. Sorption isotherms on two soils were recorded, initial concentrations ranging from 0.09 to 5.71 mg L(-)(1). The Freundlich isotherm was fitted to the values measured. The Freundlich exponents calculated were significantly smaller than unity, indicating nonlinear sorption. Sorption experiments with two metabolites of PCZ (PCZ-formylurea and PCZ-urea) revealed K(d) values one-fourth to one-third those for PCZ on two soils.     

粘土土壤孔隙大小分布及其与土壤有机质的相关性

Soil pore size distribution(PSD) directly influences soil physical,chemical,and biological properties,and further knowledge of soil PSD is very helpful for understanding soil functions and processes.In this study,PSD of three clayey soils collected from the topsoil(0-20 cm) of Vertisols in Northern China was analyzed using the N_2 adsorption(NA) and mercury intrusion porosimetry(MIP) methods.The effect of soil organic matter(SOM) on the PSD of clayey soils was also evaluated.The differential curves of pore volume of clayey soils by the NA method exhibited that the pores with diameter 0.01 μm accounted for more than 50%in the pore size range of 0.001 to 0.1 μm.The differential pore curves of clayey soils by the MIP method exhibited three distinct peaks in pore size range of 60 to 100,0.3 to 0.4 and 0.009 to 0.012 μm,respectively.In the three clayey soils,the ultramicropores(5-0.1μm) were determined to be the main pore class(on average 35.5%),followed by macropores( 75 μm,31.4%),cryptopores(0.1-0.007μm,16.0%),micropores(30-5 μm,9.7%) and mesopores(75-30 μm,7.3%).The SOM greatly affected the pore structure and PSD of aggregates in clayey soils.In particular,SOM removal reduced the volume and porosity of 5-100 μm pores while increased those of 5 μm pores in the 5-2 and 2-0.25 mm aggregates of clayey soils.The increase in the volume and porosity of 5 μm pores may be attributed to the disaggregation and partial emptying of small pores caused by the destruction of SOM.     

Mercury content in volcanic soils across Europe and its relationship with soil properties

Purpose  

Volcanoes are a natural source of Hg, whose deposition can occur in neighbouring soils. This study examines the role of soil compounds in the geochemical behaviour of total Hg (Hg _T ) in volcanic soils. An estimation of Hg from lithological origin is also assessed to ascertain the relevance of other sources in Hg _T accumulated in volcanic soils.     

Sorption and mobility of 14C-labeled imazaquin and metolachlor in four soils as influenced by soil properties

Aqueous batch-type sorption-desorption studies and soil column leaching studies were conducted to determine the influence of soil properties, soil and suspension pH, and ionic concentration on the retention, release, and mobility of [14C]imazaquin in Cape Fear sandy clay loam, Norfolk loamy sand, Rion sandy loam, and Webster clay loam. Sorption of [14C]metolachlor was also included as a reference standard. L-type sorption isotherms, which were well described by the Freundlich equation, were observed for both compounds on all soils. Metolachlor was sorbed to soils in amounts 2-8 times that of imazaquin, and retention of both herbicides was related to soil organic matter (OM) and humic matter (HM) contents and to herbicide concentration. Metolachlor retention was also related to soil clay content. Imazaquin sorption to one soil (Cape Fear) increased as concentration increased and as suspension pH decreased, with maximum sorption occurring in the vicinity of pK(a1) = (1.8). At pH levels below pK(a1) imazaquin sorption decreased as hydronium ions (H3O+) increased and competed for sites. NaCl was more effective than water in desorption of imazaquin at pH levels near the pK(a1). Mechanisms of bonding are postulated and discussed. The mobility of imazaquin through soil columns was in the order Rion > or = Norfolk > Cape Fear > or = Webster, whereas for metolachlor it was Rion > or = Norfolk > Webster > or = Cape Fear. Imazaquin was from 2 to 10 times as mobile as metolachlor.     

Sorption and desorption of cobalt by soils and soil components

The sorption of Co by individual soil components was studied at solution Co concentrations that were within the range found in natural soil solutions. Soil-derived oxide materials sorbed by far the greatest amounts of Co although substantial amounts were also sorbed by organic materials (humic and fulvic acids). Clay minerals and non-pedogenic iron and manganese oxides sorbed relatively little Co. It is considered that clay minerals are unlikely to have a significant influence on the sorption of Co by whole soils. Cobalt sorbed by soil oxide material was not readily desorbed back into solution and, in addition, rapidly became non-isotopically exchangeable with solution Co. In contrast, Co was relatively easily desorbed from humic acid and a large proportion of the Co sorbed by humic acid remained isotopically exchangeable. Cobalt sorbed by montmorillonite was more easily desorbed than that sorbed by soil oxide but less easily than that sorbed by humic acid. Cobalt sorption isotherms for whole soils at low site coverage were essentially linear and the gradients of isotherms increased with pH. A comparison of isotherm gradients for whole soils and individual soil components supported the suggestion that Co sorption in whole soils is largely controlled by soil oxide materials.     

复合污染土壤中土霉素的吸附行为及其对土壤重金属解吸影响的研究

参考经济合作与发展组织(OECD)化学品试验导则No.106,采用批量平衡试验的方法,探讨了土霉素(Oxytetracycline,OTC)在3种土壤中的吸附解吸特性,并考察了土霉素外加量对土壤中4种代表性重金属元素(铜、锌、铅、镉)解吸量的影响。试验设置的土霉素初始浓度为0.01、0.1、1.0、5.0、10.0、25.0、50.0、100、200和400 mg L-1。结果表明:(1)存在一个土霉素特征浓度,高于或低于该浓度值时土霉素的吸附性质有所差异,且高低两个浓度范围内的数据均能用Freundlich模型与Langmuir模型较好地拟合;(2)当土霉素浓度在0~25 mg L-1之间时,能在土壤表面与重金属发生竞争吸附,且重金属解吸量随土霉素浓度的增加而增加;当土霉素浓度在25~100 mg L-1之间时,部分游离态重金属以与土霉素的络合物形式重新固定于土壤表面,土壤重金属的解吸量随土霉素浓度增加而减少;土霉素浓度高于100 mg L-1时,体系p H相对于对照有明显下降,土壤重金属的解吸量与土霉素浓度又呈正相关。     

Sorption and desorption of triadimefon by soils and model soil colloids

Sorption-desorption of the azole fungicide triadimefon [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2, 4-triazol-1-yl)-2-butanone] on eight soils and a series of single, binary, and ternary model soil colloids was determined using the batch equilibration technique. Regression analysis between Freundlich sorption coefficients (K(f)) and soil properties suggested that both clay and organic C (OC) were important in triadimefon sorption by soils, with increasing importance of clay for soils with high clay and relatively low OC contents. Triadimefon sorption coefficients on soil were not significantly affected by the concentration of electrolyte or the presence of soluble soil material in solution, but they were highly dependent on the soil:solution ratio due to the nonlinearity of triadimefon sorption on soil. Freundlich sorption isotherms slopes were very similar for all soils (0.75 +/- 0.02). Desorption did not greatly depend on the concentration at which it was determined and showed higher hysteresis for more sorptive soils. Results of triadimefon sorption on model sorbents supported that both humic acid and montmorillonite-type clay constituents contribute to triadimefon retention by soil colloids.     

Sorption of Pb in chemical and particle-size fractions of soils with different physico-chemical properties

Journal of Soils and Sediments - Lead (Pb) sorption capacity (PbSmax) and distribution in chemical and particle-size fractions of six soils with different physico-chemical properties were...     

Sorption behavior of copper,zinc, and cadmium in response to simulated changes in soil properties

Abstract

Environmental changes and management practices which alter soil properties may affect the capacity of soils to sorb trace metals, such as copper (Cu), zinc (Zn), and cadmium (Cd), and thus influence the bioavailability and leach ability of the metals. Two agricultural soils were treated to partially oxidize organic matter and to decrease soil pH for evaluating the effects of acidification and organic matter oxidation on trace metal sorption onto soils. For the one soil with a pH value of 6.74 and organic carbon (C) content of 46.9 g‐kg^‐1, loss of 11% of its organic matter reduced by 97, 72, and 62% the original sorption capacity for Cu, Zn, and Cd, respectively, while the corresponding values caused by acidifying the soil one pH‐unit were 32, 16, and 29%. For the another soil with a pH of 4.69 and organic C content of 16.3 g‐kg^‐1, a decrease in pH by one unit resulted in a loss of 43, 21, and 52% of the sorption capacity for Cu, Zn, and Cd, respectively.     

Spatial variation of ammonia volatilization from soil and its scale‐dependent correlation with soil properties

Quantitative predictions of ammonia volatilization from soil are useful to environmental managers and policy makers and empirical models have been used with some success. Spatial analysis of the soil properties and their relationship to the ammonia volatilization process is important as predictions will be required at disparate scales from the field to the catchment and beyond. These relationships are known to change across scales and this may affect the performance of an empirical model. This study is concerned with the variation of ammonia volatilization and some controlling soil properties: bulk density, volumetric water content, pH, CEC, soil pH buffer power, and urease activity, over distances of 2, 50, 500, and >2000 m. We sampled a 16 km × 16 km region in eastern England and analyzed the results by a nested analysis of (co)variance, from which variance components and correlations for each scale were obtained. The overall correlations between ammonia volatilization and the soil properties were generally weak: –0.09 for bulk density, 0.04 for volumetric water content, –0.22 for CEC, –0.08 for urease activity, –0.22 for pH and 0.18 for the soil pH buffer power. Variation in ammonia volatilization was scale‐dependent, with substantial variance components at the 2‐ and 500‐m scales. The results from the analysis of covariance show that the relationships between ammonia volatilization and soil properties are complex. At the >2000 m scale, ammonia volatilization was strongly correlated with pH (–0.82) and CEC (–0.55), which is probably the result of differences in parent material. We also observed weaker correlations at the 500‐m scale with bulk density (–0.61), volumetric water content (0.48), urease activity (–0.42), pH (–0.55) and soil pH buffer power (0.38). Nested analysis showed that overall correlations may mask relationships at scales of interest and the effect of soil variables on these soil processes is scale‐dependent.     

The effects of fungicides on certain chemical and microbial properties of soils

Field application of six fungicides at twice the normal rate resulted in increases in bacterial and fungal numbers after 28 days. Members of the fungal genera Gliocladium. Penicillium and Trichoderma predominated. Fungicides when applied at the field rate decreased the concentration of NO₃^? -N in soils. while the level of exchangeable NH₄⁺ -N, K, Mn and Na were generally increased. Addition of the fungicides to soil incubated in the laboratory consistently increased exchangeable Mn and K, and occasionally increased exchangeable Cu, Na and Zn. The results are discussed in relation to the microbial changes which occur, and in relation to soil fertility.     

Electrokinetic properties of soil minerals and soils modified with polyelectrolytes

The formation features of nanoadsorption polyelectrolyte (PE) layers with the formation of a mineral-organic matrix on the surface of clay minerals and soils (kaolinite, montmorillonite, quartz sand, gray forest soil, and chernozemic soil) have been elucidated by direct adsorption measurements. It has been found that the experimental values for the limit adsorption of polyacrylamide (PAM) and polyacrylic acid (PAA) on all the minerals are significantly higher than the calculated values for the formation of a monolayer. This indicates adsorption on the surface of not only separate macromolecules but also secondary PE structures as packets or fibrils determining the cluster-matrix structure of the modified surface. The study of the electro-surface properties (electrophoretic mobility, electrokinetic potential, pH, and electroconductivity) of mineral and soil particles adsorption-modified with PEs has confirmed the differences in the adsorption mechanisms (from physical sorption to chemisorption) with the formation of surface compounds depending on the different polar groups of PEs and the mineral type.     

Andosols and soils with andic properties in the German soil taxonomy

The presence of soils with andic properties on German territory has been suspected for decades and there are numerous reports of sites where they may potentially occur. Andic properties, however, are not adequately represented by the German soil‐classification system. The German taxonomic category “Lockerbraunerde” has not been revised or reconciled with international taxonomic categories since the year 1957, when it was initially proposed. With this review, we show that there are true Andosols of both the silandic (allophane‐containing) and the aluandic (Al‐Humus‐dominated) type in Germany and that their properties differ substantially from other soils which merely exhibit low bulk density. By (1) comparing soil carbon storage between some German Andosols, Chernozems, and nonandic Cambisols with particularly low bulk density and (2) elucidation of the differential pedogenetic pathways leading to Andosol formation, we further demonstrate that Andosols are important objects of study in research issues of contemporary interest. We propose that appropriate measures be taken to lay the foundations for the protection and conservation of these soils, because they are valuable as archives of natural history and provide opportunities to study unique soil processes.     

Sorption of organic acids in acid soils and its implications in the rhizosphere

Organic acids have been implicated in many soil-forming and rhizosphere processes, but their fate in soil is poorly understood. We examined the sorption of four simple short-chain organic acids (citric, oxalic, malic and acetic) in five acid soils and on synthetic iron hydroxide (ferrihydrite). The results for both soils and ferrihydrite indicated that the sorption depended on concentration in the following order of strength: phosphate >> oxalate > citrate > malate >> acetate. The sorption reactions in soil were shown to be little influenced by pH, whereas for ferrihydrite, sorption of all ligands increased strongly with decreasing pH. The sorption of organic anions onto ferrihydrite was influenced to a lesser extent by the presence of metal cations in solution. From the results we calculated that when organic acids enter solution they rapidly become sorbed onto the soil's exchange complex (> 80% within 10 min), and we believe that this sorption will greatly diminish their effectiveness to mobilize nutrients from the rhizosphere.     

Sorption behavior of selenium and antimony in soils as a function of phosphate ion concentration

Abstract

Both selenium (Se) and antimony (Sb) are major soil and water pollutants. Their sorption behavior in a soil–plant system was studied. Soil–soil solution distribution coefficients (K _ds) for Se and Sb were measured, using a radiotracer, as an indicator of their sorption levels. Both Se and Sb behave as oxoanions (SeO^2? ₄, H₂PO^? ₄ and SO^2? ₄) in soil; thus, the effects of concentrations of two major oxoanions (SeO^2? ₄ and SeO^2? ₃) on Se and Sb sorption were also examined. The K _d values for Se for Japanese soils significantly correlated with the K _d values for Sb (n = 141). The K _ds of both Se and Sb similarly decreased with increasing SbO^? ₃ concentration. These results indicated that the sorption of Se and Sb was similarly controlled by a ligand-exchange mechanism such as phosphate sorption in soil. However, an increase in the concentration of SeO^2? ₃ did not decrease the K _ds of Se and Sb. Furthermore, the ligand-exchangeable fractions of stable Se and Sb in major Japanese soils were determined by extraction with 0.1 mol L^?1 Na₂HPO₄ solution. For both Se and Sb, the phosphate-extractable fractions were 10-fold higher for Se and fivefold higher for Sb than their water-soluble fractions. Although the total Se and Sb amounts in soils were the same, their ligand-exchangeable fractions were different. Approximately 0.9–12% of total Se and 0.2–1.3% of total Sb were extracted by the phosphate solution. These findings suggested that Se was more likely to be mobilized by the addition of phosphate than Sb. The effect of plant-available phosphate in the soil and the phosphate sorption capacity of soil on Se and Sb availabilities for plants were also examined using a pot experiment with soybean plants. The experimental results suggested that a high content of available phosphate and/or low phosphate sorption capacity of soil increased both Se and Sb availabilities to the plant. However, the results also suggested that the soil Se availability to the plant was higher than that of Sb even though the soil total Se and Sb amounts were the same.     

Effects of amino-acid chemistry and soil properties on the behavior of free amino acids in acidic forest soils

Free amino acids (FAAs) in soil solution are increasingly recognized as a potentially important source of nitrogen (N) for plants, yet we are just beginning to understand the behavior of FAAs in soil. I investigated the effects of amino-acid chemistry and soil properties on mineralization, microbial assimilation and sorption of amino-acid N in soils from three ecosystems representing the two endpoints and mid point of a temperate forest fertility gradient ranging from low mineral N availability/high FAA oak forests to high mineral N availability/low FAA maple-basswood forests. Soils were amended with six ¹⁵N-labeled amino-acid substrates that ranged widely in chemical properties, including molecular weight, C:N ratio, average net charge, hydrophobicity, and polarity: Arginine (Arg), Glutamine (Gln), Glutamate (Glu), Serine (Ser), Glycine (Gly) and Leucine (Leu). Mineralization of amino-acid N accounted for 7-45% (18% avg.) of the added label and was most strongly affected by soil characteristics, with mineralization increasing with increasing soil fertility. Mineralization of amino-acid N was unrelated to amino-acid C:N ratio, rather, I observed greater N mineralization from polar FAAs compared to non-polar ones. Assimilation of amino-acid N into microbial biomass accounted for 6-48% (29% avg.) of the added label, and was poorly predicted by either intrinsic amino-acid properties or soil properties, but instead appeared to be explicable in terms of compound-specific demand by soil micoorganisms. Sorption of amino-acid N to soil solids accounted for 4-15% (7% avg.) of the added label and was largely controlled by charge characteristics of individual amino acids. The fact that both positively- and negatively-charged amino acids were more strongly sorbed than neutral ones suggests that cation and anion exchange sites are an important factor controlling sorption of FAAs in these acid forest soils. Together, the findings from this study suggest that there may be important differences in the behavior of free amino acids in sandy, acidic forest soils compared to generalizations drawn from finer-textured grassland soils, which, in turn, might affect the availability of some FAAs in soil solution.     

Enzyme activities in vineyard soils long-term treated with copper-based fungicides

Copper-based fungicides have been applied in vineyard soils for a long time, which has resulted in increasing soil Cu concentration. However, information relating to non-target effects of these fungicides on microorganisms of these soils is scarce. The aim of this study was to determine the potential enzyme activities of vineyard soils in relation to Cu content and evaluate the potential risks of long-term application of Cu-based fungicides. For this purpose, a wide range of soil samples, having different total, exchangeable and bioavailable Cu contents, were collected from six regions of quality wines located in the NW Iberian Peninsula, and the activity of dehydrogenase, β-glucosidase, urease and phosphatase were measured. Overall, the results obtained indicate adverse effects of Cu on dehydrogenase, β-glucosidase and phosphatase activities and an inconsistent effect on urease activity. Threshold Cu concentrations at which changes in the enzyme activities became evident were 150-200 mg total Cu kg⁻¹ and 60-80 mg bioavailable Cu kg⁻¹.     

Sorption and desorption behaviors of diuron in soils amended with charcoal

Charcoal derived from the partial combustion of vegetation is ubiquitous in soils and sediments and can potentially sequester organic contaminants. To examine the role of charcoal in the sorption and desorption behaviors of diuron pesticide in soil, synthetic charcoals were produced through carbonization of red gum (Eucalyptus spp.) wood chips at 450 and 850 degrees C (referred to as charcoals BC450 and BC850, respectively, in this paper). Pore size distribution analyses revealed that BC850 contained mainly micropores (pores approximately 0.49 nm mean width), whereas BC450 was essentially not a microporous material. Short-term equilibration (< 24 h) tests were conducted to measure sorption and desorption of diuron in a soil amended with various amounts of charcoals of both types. The sorption coefficients, isotherm nonlinearity, and apparent sorption-desorption hysteresis markedly increased with increasing content of charcoal in the soil, more prominently in the case of BC850, presumably due to the presence of micropores and its relatively higher specific surface area. The degree of apparent sorption-desorption hystersis (hysteresis index) showed a good correlation with the micropore volume of the charcoal-amended soils. This study indicates that the presence of small amounts of charcoal produced at high temperatures (e.g., interior of wood logs during a fire) in soil can have a marked effect on the release behavior of organic compounds. Mechanisms of this apparent hysteretic behavior need to be further investigated.