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At least 649 records · Page 36Linked to original sources
PubMed2005

Geochemical modeling of cadmium sorption to soil as a function of soil properties.

Cadmium sorption experiments were conducted to infer Cd sorption mechanisms to a reference smectite and three fractions of a Vertisol soil. Untreated Vertisol has a higher adsorption capacity for Cd than that of reference smectite. Surface complex modeling was used to calculate the potential contributions of Cd complexation reactions with permanent charge sites and pH-dependent charge sites over ranges in pH, for soils with given surface areas, and sorption site densities. The Langmuir model produced relatively good predictions of Cd sorption on reference smectite and Vertisol. However, the results of the triple-layer model (TLM) were inadequate to describe Cd adsorption on fixed-charge sites because the model could not account for the ion-exchange reaction on the basal plane. Based upon the two geochemical models of Cd adsorption to the reference smectite and Vertisol, it appears that the basal plane siloxane cavities are the most important sites for Cd complexation at pH<6.5. For the pH-dependent sites, the edge-site aluminol appears to be the dominant surface functional group responsible for Cd adsorption at pH>6.5.

Adsorption↗
PubMed2005

Uptake of heavy metals and As by Brassica juncea grown in a contaminated soil in Aznalcóllar (Spain): the effect of soil amendments.

Two crops of Brassica juncea (L.) Czern. were grown in a field experiment, at the site affected by the toxic spillage of acidic, metal-rich waste in Aznalcóllar (Seville, Spain), to study its metal accumulation and the feasibility of its use for metal phytoextraction. The effects of organic soil amendments (cow manure and mature compost) and lime on biomass production and plant survival were also assessed; plots without organic amendment and without lime were used as controls. Plots, with or without organic amendment, having pH < 5 were limed for the second crop. Soil acidification conditioned plant growth and metal accumulation. The addition of lime and the organic amendments achieved higher plant biomass production, although effects concerning metal bioavailability and accumulation were masked somewhat by pH variability with time and between and within plots. Tissue metal concentrations of B. juncea were elevated for Zn, Cu and Pb, especially in leaves of plants from plots with low pH values (maxima of 2029, 71 and 55 microg g(-1), respectively). The total uptake of heavy metals in the plants was relatively low, emphasising the problems faced when attempting to employ phytoextraction for clean-up of pluri-contaminated sites.

Arsenic↗
PubMed2005

Sequential extraction combined with isotope analysis as a tool for the investigation of lead mobilisation in soils: application to organic-rich soils in an upland catchment in Scotland.

Sequential extraction (modified BCR procedure) combined with isotope analysis has been investigated as a tool for assessing mobilisation of lead into streams at an upland catchment in NE Scotland. The maximum lead concentrations (up to 110 mg kg(-1) in air-dried soil) occurred not at the surface but at about 10 cm depth. The lowest (206)Pb/(207)Pb ratios in any profile occurred, with one exception, at 2.5-5 cm depth. In the one exception, closest to the only road in the area, significantly lower (206)Pb/(207)Pb ratios in the surface soil together with much increased chloride concentrations (in comparison to other surface waters) indicated the possible mobilisation of roadside lead and transfer to the stream. The (206)Pb/(207)Pb ratios in extractable fractions tended at depth towards the ratio measured in the residual phase but the ratios in the oxidizable fraction increased to a value higher than that of the residual phase.

Environmental Monitoring↗
PubMed2007

Optimizing the molarity of a EDTA washing solution for saturated-soil remediation of trace metal contaminated soils.

Three experiments were conducted to optimize the use of ethylenediaminetetraacetic acid (EDTA) for reclaiming urban soils contaminated with trace metals. As compared to Na(2)EDTA, (NH(4))(2)EDTA extracted 60% more Zn and equivalent amounts of Cd, Cu and Pb from a sandy loam. When successively saturating and draining loamy sand columns during a washing cycle, which submerged it once with a (NH(4))(2)EDTA wash and four times with deionised water, the post-wash rinses largely contributed to the total cumulative extraction of Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn. Both the washing solution and the deionised water rinses were added in a 2:5 liquid to soil (L:S) weight ratio. For equal amounts of EDTA, concentrating the washing solution and applying it and the ensuing rinses in a smaller 1:5 L:S weight ratio, instead of a 2:5 L:S weight ratio, increased the extraction of targeted Cr, Cu, Ni, Pb and Zn.

Biodegradation, Environmental↗
PubMed2002

Adsorption of propisochlor on soils and soil components equation for multi-step isotherms.

Static equilibrium measurements were performed for the study of propisochlor on three different kinds of soils at pH = 7.0 at 25 degrees C. The concentration of herbicide was changed from 30 to 300 mumol/l. The obtained two-step adsorption isotherms cannot be evaluated by using the Freundlich or Langmuir equations. New equation has been derived by making use of the usual mass balance and equilibrium relationships of the adsorption and by considering the possibility of the formation of associates of the hydrophobic solute molecules. The characteristic model parameters of each step of the adsorption isotherm were estimated for the studied systems by a non-linear least square regression. The calculated curves fit well to the experimentally obtained two-step isotherms and the parameters of the model can be used for the characterization of the pesticide-soil interactions and consequently the mobility of the propisochlor in soil/water systems.

Acetamides↗
PubMed2000

The development of fungi as affected by pH and type of soil, in relation to the occurrence of bacteria and soil fungistatic activity.

A study was made on the effect of liming (Ca(OH)2) on the numbers of colony-forming units (CFU) and the biomass of fungi in loamy sand (ls) and a loose sandy soil (lss) during 90 days under laboratory conditions. Liming inhibited the growth of fungi more strongly in the lighter soil. Raising the pH of lss from its native 4.5 to 7.0 and 9.0 decreased mean fungal CFU numbers by 50%, and their biomass by 42% and 68%, respectively, in comparison with control unlimed samples. Also in ls with its native pH of 7.7, when alkalinised to 9.0 and 11.0 the fungal CFU numbers were smaller than in the control by 25% and 50%, respectively, and the fungal biomass decreased by 40% and 56%, respectively. Although in a parallel research alkalinisation has been shown to stimulate bacterial growth very strongly, especially in lss, the total microbial biomass (fungal + bacterial) declined by an average of 30% (pH 9.0) and 40% (pH 11.0) in limed ls, and by 35% (pH 7.0) and as much as 50% (pH 9.0) in lss, in comparison with the control.

Bacteria↗
PubMed2001

Functional characterization of colloidal phosphorus species in the soil solution of sandy soils.

The impact of mobile colloids on the transport of phosphorus in the subsurface environment is not well understood. We hypothesized that interactions between metals, organic matter, and P control the dynamics of mobile colloidal P species in excessively fertilized sandy soils. The effect of UV irradiation and additions of 32P, orthophosphate, Fe, Al, and NaF on the concentration of colloidal P was examined using gel filtration chromatography. In addition, molybdate unreactive P (MUP) was characterized using phosphomonoesterase assays. The high molecular mass reactive P (HMMRP) fraction did not react to orthophosphate additions, increased upon Al and Fe additions and decreased upon NaF addition and UV irradiation. These results support the hypothesis that HMMRP is present as organic matter-metal-orthophosphate complexes. The concentration of high molecular mass unreactive P (HMMUP) decreased upon UV irradiation. The MUP concentration slightly decreased upon incubation with phytase and acid phosphatase. These observations fitted well to the "protection" hypothesis, where hydrolyzable P bonds are protected from monoesterase attack through occlusion in colloidal material. Taken together, this study indicates the high potential for subsurface P loss by colloidal particles in soils excessively fertilized with animal manure.

Agriculture↗
PubMed1982

The effect of soil temperature on the degradation of cis, trans - permethrin in soil.

The degradation of [carbonyl - 14C] - cis, trans-permethrin was studied in Dubbs fine sandy loam soil incubated at 10, 25, and 40 degrees C from 0 to 64 days. The most rapid degradation of permethrin to [carbonyl - 14C] - cis, trans -3- (2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylic acid (DCVA) and ultimately 14CO2 occurred at 25 degrees C. Rapid degradation to DCVA also occurred at 40 degrees C, however, further degradation of DCVA to 14CO2 was reduced. Permethrin degradation to 14CO2 was slowest at 10 degrees C. The degradation rate of trans-permethrin was greater than the cis-permethrin at all temperatures tested. The halflives of cis- and trans-permethrin were 55 and 14 days at 10 degrees C, 12 and 5 days at 25 degrees C, and 27 and 4 days at 40 degrees C, respectively. Compounds identified from treated soil were the original [carbonyl - 14C]-cis, trans-permethrin and the major degradation products cis-, and trans-DCVA.

Biodegradation, Environmental↗
PubMed2000

Higher diversity of Rhizobium leguminosarum biovar viciae populations in arable soils than in grass soils.

The bacterial genetic diversity after long-term arable cultivation was compared with that under permanent grassland using replicated paired contrasts. Pea-nodulating Rhizobium leguminosarum populations were sampled from pairs of arable and grass sites at four locations in Yorkshire, United Kingdom. Isolates were characterized using both chromosomal (16S-23S ribosomal DNA internal transcribed spacer PCR-restriction fragment length polymorphism) and plasmid (group-specific repC PCR amplification) markers. The diversities of chromosomal types, repC profiles, and combined genotypes were calculated using richness in types (adjusted to equal sample sizes by rarefaction), Shannon-Wiener index, and Simpson's index. The relative differences in diversity within each pair of sites were similar for all three diversity measures. Chromosomal types, repC profiles, and combined genotypes were each more diverse in arable soils than in grass soils at two of the four locations. The other comparisons showed no significant differences. We conclude that rhizobial diversity can be affected by differences between these two management regimens. Multiple regression analyses indicated that lower diversity was associated with high potential nitrogen and phosphate levels or with acidity.

Agriculture↗
PubMed2006

Simulating long-term and residual effects of nitrogen fertilization on corn yields, soil carbon sequestration, and soil nitrogen dynamics.

Soil carbon sequestration (SCS) has the potential to attenuate increasing atmospheric CO2 and mitigate greenhouse warming. Understanding of this potential can be assisted by the use of simulation models. We evaluated the ability of the EPIC model to simulate corn (Zea mays L.) yields and soil organic carbon (SOC) at Arlington, WI, during 1958-1991. Corn was grown continuously on a Typic Argiudoll with three N levels: LTN1 (control), LTN2 (medium), and LTN3 (high). The LTN2 N rate started at 56 kg ha(-1) (1958), increased to 92 kg ha(-1) (1963), and reached 140 kg ha(-1) (1973). The LTN3 N rate was maintained at twice the LTN2 level. In 1984, each plot was divided into four subplots receiving N at 0, 84, 168, and 252 kg ha(-1). Five treatments were used for model evaluation. Percent errors of mean yield predictions during 1958-1983 decreased as N rate increased (LTN1 = -5.0%, LTN2 = 3.5%, and LTN3 = 1.0%). Percent errors of mean yield predictions during 1985-1991 were larger than during the first period. Simulated and observed mean yields during 1958-1991 were highly correlated (R2 = 0.961, p < 0.01). Simulated SOC agreed well with observed values with percent errors from -5.8 to 0.5% in 1984 and from -5.1 to 0.7% in 1990. EPIC captured the dynamics of SOC, SCS, and microbial biomass. Simulated net N mineralization rates were lower than those from laboratory incubations. Improvements in EPIC's ability to predict annual variability of crop yields may lead to improved estimates of SCS.

Biomass↗
PubMed2000

[Dynamics of soil P pool in a long-term fertilizing experiment of wheat-maize rotation. II. Dynamics of soil Olsen-P and inorganic P].

Studies on the dynamics of soil Olsen-P and different form inorganic P in the long-term fertilizing experiment of winter wheat-summer maize-->spring maize rotation showed that the contents of Olsen-P and inorganic P were changed by the accumulation and consumption of P in soil. In P0 treatments, Olsen-P decreased gradually, and then, trended to the critical level. When fertilizing amount was basically equal to the intake by crops, the balance of Olsen-P was dynamically maintained. The contents of Olsen-P and inorganic P were enhanced, when applied P was larger than the P intake by crops. The major contents of residual inorganic P were Ca2-P and Ca8-P, both accounting for 52.3% of total inorganic P in average, and Ca8-P accounting for 78.3%. Al-P and Fe-P accounted for 26.1%, and O-P and Ca10-P accounted for 20.4% of total inorganic P. The availability of fertilizer P was obviously increased by long-term applying fertilizer P together with manure, compared with applying fertilizer P alone.

China↗
PubMed2001

[Changes of crop yields and soil fertility under long-term application of fertilizer and recycled nutrients in manure on a black soil].

The results from a field experiment over thirteen years on a black soil in Northeast China indicated that nitrogen fertilizer increased crop yields by 724 kg.hm-2 per year on average, with an increase rate of 27.5% and about 9.4 kg increased yield from 1 kg applied N. In the early stage, the crop yields almost gave no response to phosphorus fertilizer, owing to the high level of soil available phosphorus at the beginning of the experiment. The average increase of crop yields by phosphorus in thirteen years was only 241 kg.hm-2 per year, with an increase rate of 7%, about 12.7 kg increased yield from 1 kg applied P. Annual application of recycled pig manure made by 80% of harvested grain fed to pigs and the stolks as bedding materials could increase crop yields by 268, 258 and 255 kg.hm-2 per year with an increase rate of 9.8%, 7.6% and 7.0%, based on no fertilizer, with N and with P and N, respectively. There was a trend that the effect of recycled manure on crop yield was gradually increased during the period of experiment, implying the existence of accumulative residual effect from the manure.

Agriculture↗
PubMed2003

[Spatial variability of soil nutrients in cultivated surface soil of Sujiatun District, Shenyang City].

The spatial variability of organic matter (OM), available nitrogen (AN), available phosphorus (AP), and available potassium (AK) in 0-20 cm horizon in cultivated soils of Sujiatun District, Shenyang City were investigated using geostatistics and geographic information system (GIS). Data of each variable fitted normal distribution or normal distribution after log transformation, and a spherical model for semivariogram fitted all the variables. Semivariograms indicated that OM content strongly spatially dependent with the ratio of nugget to sill of 24.11%. The contents of AN, AP and AK were moderately spatially dependent with the ratio of nugget to sill of 29.53%, 60.77% and 58.82%, respectively. The ranges of spatially dependent for OM, AN, AP and AK were 26.051, 28.293, 15.132 and 23.813 km, respectively. The spatial variability for OM and AN was fundamentally affected by structural factors such as soil formation factors, and that for AP and AK was by random factors such as fertilization. Kriging maps showed the spatial distributions of the four variables, which were useful in monitoring nutrient changes and providing quantitative support to decision and policy making for agriculture and environment management.

Geographic Information Systems↗
PubMed2001

The Adsorption of Gemini and Conventional Surfactants onto Some Soil Solids and the Removal of 2-Naphthol by the Soil Surfaces.

The adsorption of two cationic gemini surfactants, [C(n)H(2n+1) N(+)(CH(3))(2)-CH(2)CH(2)](2).2Br(-), where n=12 and 14, on limestone, sand, and clay (Na-montmorillonite) from their aqueous solution in double-distilled water and the effect of this adsorption on the removal of 2-naphthol have been studied. Compared to those of conventional cationic surfactants with similar single hydrophilic and hydrophobic groups (C(n)H(2n+1)N(+)(CH(3))(3).Br(-), where n=12 and 14), the molar adsorptions of the gemini and the conventional surfactants on Na-montmorillonite are almost identical and very close to their cation exchange capacities. On sand and limestone, the molar adsorption of the cationic gemini surfactants is much larger than that of their corresponding conventional surfactants. Adsorption studies of the pollutants onto the three kinds of solids treated by either the gemini or the conventional surfactants show that the former are both more efficient and more effective at removing 2-naphthol from the aqueous phase. On all three soil solids, the addition of KBr increases the efficiency of the adsorption of both types of cationics and for most cases increases also the maximum amount adsorbed, but decreases slightly the efficiency of removal of 2-naphthol. On limestone, the anionic gemini adsorbs with one hydrophilic group oriented toward the Ca(2+) sites on the surface and its second hydrophilic group oriented toward the aqueous phase. The conventional anionic surfactant forms a double layer. The gemini anionic is more efficient and more effective than the conventional anionic in the removal of 2-naphathol from the aqueous phase. Both anionic conventional and gemini surfactants have no adsorption on sand. The adsorption mechanisms for all the surfactants on the three soil solid surfaces are discussed. Copyright 2001 Academic Press.

Journal Article↗
PubMed2006

Trace element availability and plant growth in a mine-spill contaminated soil under assisted natural remediation I. Soils.

We evaluated the effects of different amendments and/or a plant cover on reclamation of a trace element contaminated soil. Seven treatments were established: four organic (leonardite (LEO), litter (LIT), municipal waste compost (MWC), biosolid compost (BC)), one inorganic (sugar beet lime (SL)) and two controls (control without amendment but with Agrostis (CTRP) and control without amendment and without Agrostis (CTR)). Results showed that total organic C was significantly higher in organic treatments in all samplings. Water-soluble C was lower in CTR compared to other treatments, but no significant differences were observed between organic treatments and SL and CTR. SL, BC and MWC treatments increased soil pH and reduced 0.01 M CaCl2-extractable Cd, Cu and Zn concentrations more efficiently, especially in the first 2 years. At the end of the experiment 0.01 M CaCl2-extractable trace element concentrations were similar in all treatments. 0.01 M CaCl2-extractable As and Pb were below the detection limit. Addition of amendments showed no clear reduction in 0.05 M EDTA-extractable trace element concentrations and some amendments even increased 0.05 M EDTA-extractable As and Cu with time. Pseudo-total trace element concentrations were higher for As in controls. On the other hand, mean values of Cu and Zn were higher in MWC treatment. BC and SL treatments also showed higher Zn mean concentration than controls. No amendment effect was observed for Cd and Pb.

Journal Article↗
PubMed2003

Certification of the European Reference Soil Set (IRMM-443--EUROSOILS). Part II. Soil-pH in suspensions of water and CaCl2.

IRMM-443 re-groups a set of six European Reference Soils (EUROSOILS), which had been certified for their adsorption coefficients for atrazine, 2,4-D and lindane (Certification of the European Reference Soil Set (IRMM-443-EUROSOILS)-Part I. Adsorption coefficients for atrazine, 2,4-D and lindane. Sci Total Environ, in press). The certification of these parameters was complemented by an additional certification of pH in suspension as well by the determination of indicative values for total nitrogen, organic and total carbon content. While Part I explained the principles of the value assignment process and discussed their application to the adsorption coefficients, Part II presents the certified values for pH as well as the indicative values for N(tot), C(tot) and C(org). In addition, the assessment of uncertainty components for stability and homogeneity, which have been included in the final uncertainty budget, is discussed.

Journal Article↗
PubMed2000

Bound residues of organic compounds in the soil: the significance of pesticide persistence in soil and water: a European regulatory view.

The paper discusses key aspects of the European Union (EU) regulatory policy for persistence of agricultural pesticide active substances (a.s.) in soil, which is examined in the context of the EU Authorisations Directive (91/414/EEC). For agricultural pesticide regulation within EU Member States (MS), the Authorisations Directive will gradually replace existing national systems. Discussion is concentrated on this directive, looking in particular at the Uniform Principles therein and the possible ways that these decision-making guidelines could be developed into a regulatory framework. The aim in this process of negotiated development is to identify any questions or data requirements that will be needed for persistent pesticides, over and above those generally required for all compounds. The present European regulatory position on soil non-extractable or bound residues is discussed. Finally, a brief mention of pesticide persistence in water and sediment is made.

Journal Article↗
PubMed1995

Methanogenic and other strictly anaerobic bacteria in desert soil and other oxic soils.

Strictly anaerobic bacteria such as methanogenic, sulfate-reducing, and homoacetogenic bacteria could be enriched from all five oxic soils tested. The number of cells was lower than that in typical anoxic habitats. Spores did not always dominate the population of sulfate-reducing bacteria. In all soils, the methanogenic population displayed a long lag phase after anoxic conditions were imposed before methane production began.

Journal Article↗