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PubMed2006

Copper activity in soil solutions of calcareous soils.

Copper partitioning was studied in seven calcareous soils at moisture content corresponding to 1.2 times the field moisture content (soil water potential 7.84 J kg(-1)). Copper retention was accompanied by the release in soil solution of Ca(2+), Mg(2+), Na(+), and H(+), and the total amount of these cations released was 0.8 to 1.09 times the amount of Cu sorbed (mol(c):mol(c)). The relationships between Cu activity and pH, and the balance of cations in soils correspond with the surface precipitation of CuCO(3) as the main mechanism of Cu retention. The values of ion activity product of surface precipitate were close for all studied soils with the average log(IAP(CuCO(3)))=-15.51. The relationship between copper activity in soil solutions and soil properties is well fit by a regression relating pCu (-log copper ion activity) with soil pH, total Cu, and carbonate content.

Calcium↗
PubMed2002

Transport of fallout radiocesium in the soil by bioturbation: a random walk model and application to a forest soil with a high abundance of earthworms.

It is well known that bioturbation can contribute significantly to the vertical transport of fallout radionuclides in grassland soils. To examine this effect also for a forest soil, activity-depth profiles of Chernobyl-derived 134Cs from a limed plot (soil, hapludalf under spruce) with a high abundance of earthworms (Lumbricus rubellus) in the Olu horizon (thickness=3.5 cm) were evaluated and compared with the corresponding depth profiles from an adjacent control plot. For this purpose, a random-walk based transport model was developed, which considers (i) the presence of an initial activity-depth distribution, (ii) the deposition history of radiocesium at the soil surface, (iii) individual diffusion/dispersion coefficients and convection rates for the different soil horizons, and (iv) mixing by bioturbation within one soil horizon. With this model, the observed 134Cs-depth distribution at the control site (no bioturbation) and at the limed site could be simulated quite satisfactorily. It is shown that the observed, substantial long-term enrichment of 134Cs in the bioturbation horizon can be modeled by an exceptionally effective diffusion process, combined with a partial reflection of the randomly moving particles at the two borders of the bioturbation zone. The present model predicts significantly longer residence times of radiocesium in the organic soil layer of the forest soil than obtained from a first-order compartment model, which does not consider bioturbation explicitly.

Animals↗
PubMed2001

Increased retention of polycyclic aromatic hydrocarbons in soils induced by soil treatment with humic substances.

The analytical recovery of a mixture of polycyclic aromatic hydrocarbons (PAHs) was determined from a soil before and after oxidation with hydrogen peroxide, and subsequently treated with increasing amounts of an exogenous humic acid and subjected to different incubation periods. The release of PAHs from soil depended on the specific structure and physico-chemical properties of each PAH, and increased with additions of exogenous humic materials for both the oxidized and non-oxidized soil as well as with time of PAH permanence in soil. PAH recoveries were lower in the non-oxidized soil, thereby revealing the importance of native organic matter in increasing PAH retention in soils. This study shows that mobility of PAHs in soils can be controlled by soil conditioning with humic substances.

Environmental Pollution↗
PubMed2000

Adsorption and mobility of linuron in soils as influenced by soil properties, organic amendments, and surfactants.

Adsorption and mobility of the herbicide linuron (3-3, 4-dichlorophenyl-1-methoxy-1-methylurea) in 35 irrigated soils with organic matter (OM) contents in the 0.43-2.59% range and in four natural soils with OM contents in the 4.16-11.69% range were studied using the batch equilibration technique. The adsorption isotherms were found to conform to the Freundlich adsorption equation. The Freundlich constant, K, and the distribution coefficient, K(d), were seen to be highly significantly correlated (p < 0.001) with the OM content when all soils or only those with an OM content above 2% were considered. There was also a significant correlation of K and K(d) with the OM content (p < 0.05) and of K(d) with the clay and silt plus clay contents (p < 0.1) when the soils with a OM content below 2% were considered. On the basis of the R(f)() values obtained by soil TLC, the pesticide was found to be slightly mobile in 77% and moderately mobile in 23% of the soils studied. The results of the leaching of linuron in soil columns unmodified and modified with two organic agricultural amendments, a city refuse compost, and two surfactants (one of them cationic and the other anionic) revealed that the leaching rate and the mass transfer of the herbicide to water were affected, increasing or decreasing according to the characteristics of the amendments and the doses added. These results also point to the usefulness of selected organic materials and surfactants in the development of physicochemical methods for preventing the pollution of soils, sediments and aquifers by hydrophobic pesticides.

Adsorption↗
PubMed2001

Survival and proliferation of alginate encapsulated Trichoderma spp. in Egyptian soil in comparison with allyl alcohol soil fumigation.

Conidia of Trichoderma harzianum and T. pseudokoningii (Rifai) were formulated to make alginate pellets with or without 10% cellulose as a food-base material. The formulations were compared for their ability for survival and proliferation of Trichoderma spp. in clay-loamy soil (50% moisture content) with allyl alcohol fumigation (0.05, 0.1 and 0.2 ml/1,000 ml space). Trichoderma medium E (TME) containing 100 microg/ml pentachloronitrobenzene (PCNB) was valuable for isolation and counting of Trichoderma spp. from the tested soil than the Glucose-Czapek's agar medium containing 1:15,000 Rose-bengal. The promotive effect of Trichoderma by different doses of allyl alcohol fumigation still enhanced after two-month incubation period. Conidia entrapped in alginate with or without cellulose and introduced into the soil survived better than conidia added directly to the same soil after three months incubation period. Sterile soil provided a more favorable environment for the proliferation and survival of immobilized conidia than the non-sterile soil, and the addition of 10% cellulose increased the survival of the entrapped conidia more than those prepared without cellulose. Soil fumigation inhibited the occurrence of other fungal species; however, inoculation of the soil with alginate immobilized conidia or conidial suspension had such inhibitory effect but in a less extent.

Alginates↗
PubMedDate not supplied

Quantitative estimates of soil ingestion in normal children between the ages of 2 and 7 years: population-based estimates using aluminum, silicon, and titanium as soil tracer elements.

This investigation was undertaken to provide quantitative estimates of soil ingestion in young children on a population basis, and to identify demographic and behavioral characteristics that influence the amount of soil ingested. A total of 104 children between the ages of 2 and 7 yr were selected randomly from the population of a three-city area in southeastern Washington State. Using aluminum, silicon, and titanium as tracer elements, a mass-balance approach was employed to assess daily soil ingestion. A duplicate of all food items consumed, all feces, and some urine excreted were collected on 4 consecutive d, along with soil and house dust samples from each child's home. Samples were analyzed by x-ray fluorescence spectrometry. After adjustment of the soil ingestion estimates to account for missing food, excreta samples, and nonfood items consumed, the average daily values based on the three tracer elements were: aluminum, 38.9 mg/d (median = 25.3 mg/d); silicon, 82.4 mg/d (median = 59.4 mg/d); and titanium, 245.5 mg/d (median = 81.3 mg/d). No consistent pattern emerged regarding a demographic or behavioral profile that was predictive of soil ingestion. This work demonstrates (a) the feasibility of conducting large-scale studies to determine soil intake levels in human populations, (b) provides estimates of soil ingestion in small children based on a random population sample, and (c) suggests several possibilities for additional research initiatives in this area.

Age Factors↗
PubMed1996

Effect of soil loading on dermal absorption efficiency from contaminated soils.

The effect of soil loading on the dermal uptake of soil-borne contaminants was examined using an in vitro evaporation/penetration apparatus and abdominal skin from human cadavers. Dermal uptake of two 14C-labeled pesticides, lindane and 2,4-dichlorophenoxyacetic acid (2,4-D), was assessed at nominal soil loadings of 1, 5, and 10 mg/cm2. Sub-150-microns fractions of two soils with differing organic carbon contents were employed. Mean 24-h dermal absorption values ranged from 0.45 to 2.35% for lindane and from 0.18 to 1.64% for 2,4-D, depending upon soil load and type. Mean mass fluxes ranged from 8.8 to 32 pg/cm2/h for lindane and from 1.9 to 6.4 pg/cm2/h for 2,4-D. Results were aggregated as ratios of flux or percent absorption at 1 and 10 mg/cm2 to corresponding values obtained at 5 mg/cm2. Fluxes at 5 and 10 mg/cm2 did not differ significantly, but flux at 1 mg/cm2 was about one-half the value observed at the higher loadings. The most plausible explanation for this decrease in mass flux is incomplete (submonolayer) coverage of the skin. Evidence in the form of electron micrographs is presented in support of this conclusion. Relative percent absorption increased significantly with decreases in soil load from 10 to 5 and from 5 to 1 mg/cm2. This effect was inversely proportional to loading reduction in the former case, but was less than proportional due to the impact of contact area reduction (and, in the case of lindane, volatilization losses) in the latter. Percent dermal absorption data obtained in the laboratory require adjustment for differences in loading and coverage before application to assessment of exposure to contaminants in soils. Description of dermal absorption from soil in a manner comparable to that used to describe absorption from a liquid or vapor (i.e., using a driving force and a mass transfer coefficient) would reduce confusion on this point and is recommended.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1976

Volatilization of lindance from water in soil-free and flooded soil systems.

Volatilization of 14C-lindane from water in planchets and under flooded soil ecosystem was investigated. Lindane disappeared faster than parathion from planchets. More rapid loss of both insecticides occurred from water than from chloroform. Loss of lindane and parathion was related to measured losses of water by evaporation. During 5-day incubation under flooded soil conditions, disappearance of lindane was faster from open vials than from sealed vials, whereas in nonflooded soil, no volatile loss of the insecticide was evident despite water evaporation. Over 5 day incubation under flooded conditions, greater volatile loss of lindane occurred in sandy soil than in alluvial soil apparanetly due to greater adsorption to the soil colloids decreasing the insecticide concentration in the standing water on the laterite soil. Under identical conditions of water evaporation, lindane loss was directly proportional to its initial concentration in the water. These results suggest that considerable loss of soil applied pesticides can occur by volatilization from the standing water in flooded rice fields, particularly under tropical conditions.

Hexachlorocyclohexane↗
PubMed2003

Influence of organic and inorganic soil amendments on plant growth in crude oil-contaminated soil.

Phytoremediation can be a viable alternative to traditional, more costly remediation techniques. Three greenhouse studies were conducted to evaluate plant growth with different soil amendments in crude oil-contaminated soil. Growth of alfalfa (Medicago sativa L., cultivar: Riley), bermudagrass (Cynodon dactylon L., cultivar: Common), crabgrass (Digitaria sanguinalis, cultivar: Large), fescue (Lolium arundinaceum Schreb., cultivar: Kentucky 31), and ryegrass (Lolium multiflorum Lam., cultivar: Marshall) was determined in crude oil-contaminated soil amended with either inorganic fertilizer, hardwood sawdust, papermill sludge, broiler litter or unamended (control). In the first study, the addition of broiler litter reduced seed germination for ryegrass, fescue, and alfalfa. In the second study, bermudagrass grown in broiler litter-amended soil produced the most shoot biomass, bermudagrass produced the most root biomass, and crabgrass and bermudagrass produced the most root length. In the third study, soil amended with broiler litter resulted in the greatest reduction in gravimetric total petroleum hydrocarbon (TPH) levels across the six plant treatments following the 14-wk study. Ryegrass produced more root biomass than any other species when grown in inorganic fertilizer- or hardwood sawdust + inorganic fertilizer-amended soil. The studies demonstrated that soil amendments and plant species selection were important considerations for phytoremediation of crude oil-contaminated soil.

Cynodon↗
PubMed2006

Soil survival of Escherichia coli O157:H7 acquired by a child from garden soil recently fertilized with cattle manure.

AIMS: This investigation was conducted to determine the survival of a naturally occurring Escherichia coli O157:H7 in garden soil linked to a sporadic case of E. coli O157 infection in Minnesota. METHODS AND RESULTS: The presence and viability of E. coli O157:H7 was monitored in manure-contaminated garden soil for several weeks. Bacterial isolates were characterized using PCR and pulsed-field gel electrophoresis (PFGE). Isolates obtained from the patient and the garden plots during this investigation had indistinguishable PFGE patterns and had the same virulence factors (stx1, stx2, eaeA, ehxA). The E. coli O157:H7 levels obtained from the garden plots declined gradually for a period of 2 months, and on day 69 only one garden plot of four had detectable levels of pathogen. All plots were negative on day 92. The rate of decline in the soil samples stored at 4 degrees C was faster compared with soil samples that remained in ambient conditions, and in refrigerated storage E. coli O157:H7 could not be detected after 10 days. CONCLUSIONS: E. coli O157:H7 strains can survive on manure-amended soil for more than 2 months, and this survival could be reduced by low temperature. SIGNIFICANCE AND IMPACT OF THE STUDY: This is one of the few reports that have investigated the survival of a proven virulent strain in naturally contaminated soil samples. This case stresses the importance of avoiding the use of raw cattle manure to amend soil for cultivation of foods, including soils in residential garden plots.

Animals↗
PubMedDate not supplied

Bioremediation of residual fertilizer nitrate: II. Soil redox potential and soluble iron as indicators of soil health during treatment.

The prospect of using wastewater containing high loads of soluble organic matter (OM) for removing residual agricultural chemicals (fertilizer, pesticide, or herbicide) in farm soil, although promising, could have adverse effects on soil agricultural quality as a result of development of redoximorphic features in the soil profile. In this study, the effect of organic carbon supplement for bioremediation of residual fertilizer nitrate on soil properties, redox potential (Eh), pH, and metal ion mobilization was studied using sandy soils packed in columns. The study was included in a general project, described elsewhere (Ugwuegbu et al., 2000), undertaken to evaluate use of controlled water table management (WTM) systems to supply organic carbon for creating a reduced environment conducive to denitrification of residual fertilizer nitrate leaching from the farm to subsurface water. The columns were subjected to subirrigation with water containing soluble organic carbon in the form of glucose. The work was carried out in two experimental setups and the long-term effect of a range of glucose concentrations on the Eh, pH, and soluble levels of Fe and Mn was investigated. From the results obtained, it could be concluded that excessive organic carbon supplement to soil can have adverse effects on soil quality and that Eh and soluble Fe are the two most practical parameters for monitoring soil health during treatment of farm chemicals.

Agriculture↗
PubMed2001

Predicting soil-water partition coefficients for Hg(II) from soil properties.

The metal adsorption characteristics for fifteen Taiwan soils by Hg(II), were evaluated using pH as the major variable. The soil samples were thoroughly characterized for their physical chemical properties and composition, particularly organic matter and metal oxides. The adsorption of Hg(II) increased with increasing pH between pH 2.5 and 5.5, whereas the adsorption significantly decreased above around pH 5.5. Below pH 5.5, greater adsorption was found for soils with a higher organic matter content at constant pH and metal concentration. To better understand the mechanism of adsorption, the experimental results for Hg (II) were tested in a partition coefficient model to relate the adsorption of the Hg(II) by the different soils with soil components: organic matter, iron oxide, aluminium oxide and manganese oxide. This model was not successful when applied to measurements at the differing natural soil pHs because of the importance of pH. At pH greater than 5.5 the model fails because of the complexation of Hg by the dissolved organic matter. However, partition coefficients obtained from experimental data were highly correlated with those calculated for a partition coefficient between mercury and organic matter alone at lower pH. Normalization of the partition coefficients, Kd, for the organic matter content of the soils, Kom, greatly improved the correlation between the partition coefficient and pH under pH 5.5 (R2 increased from 0.484 to 0.716). This suggests that the surficial adsorption sites are principally due to organic matter for pH less than 5.5. For the 24-hour equilibration period employed, diffusion of Hg through this superficial organic matter coating to underlying sorptive materials, including metal oxides, is not important in the partitioning of Hg. At pH above 5, a decrease of mercury adsorption with increasing solution pH was also found. This result may be explained in part by the complexation of mercury by soil dissolved organic matter whose concentration increased with increasing pH.

Adsorption↗
PubMed1975

Degradation of organophosphorus pesticides in soils with special reference to unaerobic soil conditions.

Organophosphorus pesticides are generally transformed by the reactions including oxidation, reduction, hydrolysis, hydroxylation, dehydrochlorination, dealkylation, methylation, isomerization, and conjugate formation. Although the degradation process of pesticides in soils is complicated, main factors may be soil constituents, soil microflora, and chemical structures of pesticides. Chemical structures are especially important for soil metabolism of organophosphorus pesticides, because the priority of the reactions mentioned above is decided. Although organophosphorus pesticides are generally hydrolyzable, the order of hydrolysis varies with chemical structures. It might be said that the slower the hydrolysis rate of the molecule, the more the possibility to be attacked by reactions other than hydrolysis. In such cases, oxidation and reduction are primarily important for the degradation of organophosphorus pesticides. Flooded soils in paddy fields give a favourable environment for the reduction of organophosphorus pesticides having labile substituents such as nitro groups. The threshold of reduction in-flooded soil is expressed as redox potential. Eh, the Eh of paddy soil fluctuates to a great extent, depending on seasons and soil types, especially organic matter content. The result of laboratory experiments with fenthion, disulfoton, Kitazin P (0,0-diisopropyl S-benzyl phosphorothiolate), edifenphos (0-ethyl S,S-diphenyl phosphorodithiolate) and amiprophos (0-ethyl 0-(2-nitro-p-tolyl) N-isopropyl phosphoramidothionate) suggested the participation of several factors mentioned above in the degradation of organophosphorus pesticides.

Anaerobiosis↗
PubMed2003

[Relationship between soil enzyme activities and trace element contents in Eucalyptus plantation soil].

Canonical correlation analysis on soil enzyme activities and trace element contents in Eucalyptus plantation soil showed that among the test elements, only Zn and Mn affected enzyme activity. Both Zn and Mn increased soil proteinase activity. Zn decreased the activities of soil urease and peroxidase, while Mn promoted them. "Integral soil enzyme factor" could be used as an index of soil fertility. Together with other growth factors, this index should be considered when evaluating soil fertility of Eucalyptus forest sites. It also had a definite significance on the division of Eucalyptus soil families.

Endopeptidases↗
PubMed2004

Indigenous soil bacteria and low moisture may limit but allow faecal bacteria to multiply and become a minor population in tropical soils.

The soil environment in Hawaii is generally characterised as sub-optimal but permissive to support the in situ growth of E. coli and enterococci. However, soil desiccation and competition for nutrients by major indigenous soil microflora have been identified as potential factors that could limit a rapid and continual growth of faecal indicator bacteria in this soil environment. Despite these limitations, the genetic capacities of E. coli and enterococci are robust enough to enable these bacteria to become established as minor populations of Hawaii's soil microflora. Although the concentrations of E. coli and enterococci may have represented a fraction of the total soil microbiota, their presence in this habitat was very significant, for two important reasons: (a) soil was a major environmental source of E. coli and enterococci, and (b) the elevated counts of these bacteria in streams that routinely exceeded the EPA standards were due to run-off from soil. As a result, E. coli and enterococci were inadequate indicators to measure the degree of faecal contamination and potential presence of sewage-borne pathogens in Hawaiian streams.

DNA, Bacterial↗
PubMed1981

[Survival of ascaris eggs, salmonella and fecal coli in soil and on vegetables grown in infected soil (author's transl)].

In an experiment it was shown that eggs of Ascaris suum, salmonella and fecal coliform bacteria mixed with sewage sludge and added to soil, will survive the first growing season. Most eggs of Ascaris suum in soil embryonated within a period of 7--15 weeks. In soil without a protective vegetation the concentration of eggs in the top soil layer 0--3 cm decreased faster than in soil with a protective vegetation. At the same time there seemed to be a corresponding increase in the concentration of eggs in the deeper layers of the soil. In the top layer, especially in the top soil without a protective vegetation, there was towards the end of the first growing season a higher per cent of dead eggs than in the deeper layers. The concentration of fecal coliform bacteria and salmonella was in the course of the first growing season reduced to 1/1000 and 1/10000, respectively, of the initial concentration. Infective Ascaris suum eggs and salmonella were found in washing water from vegetables grown in the first season. Infective Ascaris suum eggs were also present in soil in the second and third growing season.

Ascaris↗
PubMed2001

Enhancing pyrene mineralization in contaminated soil by the addition of humic acids or composted contaminated soil.

The addition of composted PAH-contaminated soil to PAH-contaminated soil spiked with 14C-labeled pyrene resulted in rapid mineralization of pyrene (more than 57% after 21 days compared with 3.4% in un-amended soil). The addition of the humic acid fraction of the composted soil also increased the mineralization potential of the soil significantly, but to a lesser extent (37.5% mineralization after 106 days compared with 20.6% in unamended soil). Increasing the humic acid concentration increased mineralization up to a maximum of more than three times the unamended rate, after which the rate of pyrene mineralization decreased, possibly due to inhibitory pH or concentrations of salts. The amendment of PAH-contaminated soil with materials containing humic acids or humic acid extracts is suggested as a method of bioremediation.

Bacteria↗
PubMed2004

[Ecological effects of low dosage mixed rare earth elements accumulation on major soil microbial groups in a yellow cinnamon soil].

A combination of field plot experiment and simulated low dosage accumulation test was adopted to study the ecological effects of low dosage mixed rare earth elements (REE) accumulation on major soil microbial groups in a yellow cinnamon soil. The continuous accumulation of REE had the alternative effects of stimulation, inhibition and re-stimulation on soil bacteria and actinomycetes, and a continuous stimulation on soil fungi. The inhibitory intensity of REE on the three groups of soil microorganisms was in the order of bacteria > actinomycetes > fungi. At the accumulation of 150 mg x kg(-1) of REE, the population structure of three groups changed remarkably. The number of REE-tolerant microbes increased, with gram negative bacteria, white spore group and penicillium being predominant in bacteria, actinomycetes and fungi population, respectively. The median effect concentration (EC50) of REE was 24.1, 41.6-73.8 and 55.3-150.1 mg x kg(-1) for soil bacteria, actinomycetes and fungi, respectively. The EC50 value of 30 mg x kg(-1) might be taken as the critical value of mixed REE in yellow cinnamon soil.

Ecosystem↗