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PubMed2002

[Microbial biomass affected by cadmium with the occurrence of organic acids in red soil].

Soil microbial biomass carbon and nitrogen were determined after adding fixed concentration of organic acids and changeable concentration of cadmium in pre-incubated red soil and 14-day incubation at 25 degrees C. The results show that soil microbial biomass carbon and nitrogen in the soil added with organic acids decreased with increasing concentration of cadmium. When the concentration of cadmium was higher than 25 mg.kg-1, the microbial biomass carbon and nitrogen in the soil added with low molecular weight of organic acids (oxalic acid, acetic acid, citric acid, tartaric acid) were lower than those without the addition of organic acids, indicating that low molecular weight of organic acids could increase the toxicity of cadmium. On the contrary, the microbial biomass carbon and nitrogen in the soil added with low molecular weight of organic acids were higher than those without the addition of organic acids when the concentration of cadmium was lower than 25 mg.kg-1, indicating that low molecular weight organic acids could decrease the toxicity of cadmium. The microbial biomass carbon and mitrogen in the soil containing humic acid were higher than those without the addition of organic acids, indicating that humic acid could decrease the toxicity of cadmium. However, the C:N ratio of soil microbial biomass was increased with increasing concentration of cadmium. Organic acids could increase microbial biomass carbon and nitrogen when soil was not added with cadmium.

Acetic Acid↗
PubMed2006

Arsenate sorption on two Chinese red soils evaluated with macroscopic measurements and extended X-ray absorption fine-structure spectroscopy.

Arsenic sorption is the primary factor that affects the bioavailability and mobility of arsenic in soils. To elucidate the characteristics and mechanisms of arsenate, As(V), sorption on soils, a combination of sorption isotherms, zeta potential measurements, and extended X-ray absorption fine-structure (EXAFS) spectroscopy was used to investigate As(V) sorption on two Chinese red soils. Arsenate sorption increased with increasing As(V) concentration and was insensitive to ionic strength changes at pH 6.0. Arsenate, mainly as H2AsO4- in soil solution at pH 6.0, was strongly sorbed mainly through ligand exchange by the two soils. The sorption capacity was affected by the iron and aluminum mineral contents in the soils. The zeta potential measurements showed that As(V) sorption lowered the zeta potential and the points of zero charge of the soils. The EXAFS data indicate that adsorbed As(V) forms inner-sphere complexes with bidentate-binuclear configurations, as evidenced by an As-Fe bond distance of 3.28 +/- 0.04 A and an As-Al bond distance of 3.17 +/- 0.03 A. The two As(V) complexes were stable at different As(V) loadings, whereas the proportions were related to the aluminum and iron mineral contents in the soils. This study illuminated the importance of inclusion of microscopic and macroscopic experiments to elucidate sorption behavior and mechanisms.

Absorption↗
PubMed2006

[Effects of organic acids on Cd desorption of South China red soil].

Cadmium (Cd) pollution greatly threatens the environment of South China, where the economy developed very fast during last 20 years. In this paper, batch experiments were conducted to study the effects of three organic acids and their mixed solutions on the Cd desorption of red soil in this region. The results showed that oxalic acid and malic acid retarded the Cd desorption, but oxalic acid promoted it when the concentration was 20 mmol x L(-1) and soil pH value was higher than 5.0. With the increase of soil pH, Cd desorption decreased rapidly in the presence of oxalic acid and malic acid. Citric acid retarded Cd desorption at pH < 5.0, but promoted it at pH > 5.0. When the concentration of citric acid was 2 mmol x L(-1) and pH value changed from 3.0 to 7.0, Cd desorption declined first, increased then, and declined again. But, at the citric acid concentration of 20 mmol x L(-1), Cd desorption declined first till pH 4.0, and increased then till pH 7.0. At low pH (3.0 and 4.0), malic acid desorbed most Cd; while at high pH (5.0-7.0), citric acid desorbed most Cd. The Cd desorption rate was much higher in the presence of citric acid than oxalic acid and malic acid. Organic acids did not interactive effect on Cd desorption. The Cd desorption rate by mixed acids was within the range of that by single acid alone.

Adsorption↗
PubMed2003

[Effects of rhizobia on morphological distribution of Cu, Zn and Cd in soil].

Red soil from Chenzhou of Hunan and brown soil from Gongyi of Henan were collected and treated with Cu (NO3)2, Zn(NO3)2 or Cd(NO3)2, respectively for 2 weeks, and Rhizobium fredii strain HN01 was inoculated. Sequential extraction method was employed to investigate the forms of Cu, Zn and Cd in the examined soils with the absence and presence of rhizobia. The results showed that after inoculation, the total amount of solid-bound Zn decreased 10%, and the amount of Zn associated with carbonate, Mn oxides, and organic matter fraction decreased 9-26%. No significant change was observed for the total amount of Zn combined with the solid phase of red soil in the presence of rhizobia. However, the amount of specifically adsorbed and Mn oxides bound Zn decreased, while the amount of exchangeable Zn increased. Inoculation of rhizobia depressed the release of Cu to the soil solution, and increased the total amount of Cu associated with the solid phase of brown soil. The increase of the amount of exchangeable Cu and of the Cu in fractions of carbonate, Mn oxides and organic matter ranged from 20% to 54%. There was no significant change for the level of Cd in the solution in both soils after rhizobia inoculation. The amount of exchangeable and organic Cd increased 22% and 11%, while the specifically adsorbed, and Mn oxides bound Mn decreased 14% and 29%, respectively. The different influence of rhizobia on the morphological distribution of test heavy metals in two soils was mainly ascribed to the soil pH changes.

Cadmium↗
PubMed2003

[Effect of phosphorus on arsenic adorption by three different soils].

The effect of phosphorus on arsenic adsorption by yellow soil, red soil and brown soil was studied using batch experiment. The results indicated that the arsenic without P amendment adsorption capacity of three tested soils was yellow soil > red soil > brown soil. The maximal adsorption capacity of yellow soil and red soil was decreased with 60 mg.kg-1 phosphorus added, and that of brown soil was increased with 20 mg.kg-1 phosphorus added. The arsenic adsorption capacity of three soils was greater when P: As = 1:2 than that when P: As = 1:1 and P: As = 2:1, and the differences between P: As = 1:1 and P: As = 2:1 treatments were not significant. Observations could be better fitted by Langmuir equations.

Adsorption↗
PubMed2002

[Characteristics of nitrogen loss from sloping field in red soil area under different cultivation practices].

The characteristics of nitrogen loss under six types of cultivation practices were studied in Lanxi Water and Soil Conservation Supervision Station of Zhejiang Province. The results showed that compared with the traditional cultivation practice (treatment 5, straight farming), the other cultivation practices including grass strip, contour ditch, contour farming, contour dam, and fallow decreased soil nitrogen loss significantly, and the percentages of nitrogen loss under the 5 types of cultivation practices decreased by 43.46%, 46.55%, 71.36%, 77.05%, and 87.92%, respectively. Soil nitrogen lost mainly with runoff, and it accounted for 81.9-93.4% of total soil nitrogen loss. Dissolved nitrogen was the major form of lost nitrogen and accounted for 78-87.6% of total lost nitrogen in runoff. Nitrogen loss was occurred mainly during May to August, and it accounted for 85-100% of total annual nitrogen loss.

Agriculture↗
PubMed2003

[Characteristics of phosphorus losses from slope field in red soil area under different cultivated ways].

A study on the properties of phosphorus loss under different cultivated ways was conducted in Lanxi Water and Soil Supervision Conservation Station of Zhejiang Province in 2000. The results showed that the phosphorus lost mainly through bed load and runoff. Phosphorus lost through runoff accounted for 55.26% of total lost phosphorus in straight farming field, but in other farming field, phosphorus lost with runoff accounted for 67.59%-88.11%. Particle phosphorus was the major form of the lost phosphorus, which contributed to 57.79%-77.59% of total lost phosphorus. The runoff most phosphorus was available phosphorus. Comparing with the traditional cultivated ways in the local area(treatment 5, stright farming field), the alternative different cultivated ways reduced soil phosphorus loss by 40.73%-84.70%, the contour, contour dam and fallow had better effect on controlling loss of phosphorus than the contour ditch and contour grass strip. In a year of 2000 most of the lost phosphorus was occurred during May to August accounting for 89.15%-100% of total lost.

Agriculture↗
PubMed2003

[Microbial eco-characteristics of reclaimed mining wasteland in red soil area of southern China. I. Effects on soil microbial activity].

Studies on the soil microbes, soil enzyme activity and soil biochemical intensity in copper mining wasteland indicated that the total quantity of major soil microbes declined by 68.43%-80.32%, compared with that of the non-minig soil. The proportion of bacteria and actinomyces decreased, while that of fungi did not changed obviously. The amount of major physiological groups including ammonifiers, nitrogen fixing bacteria, cellulose decomposing bacteria, aerobic nitrogen fixing bacteria and anaerobic nitrogen fixing bacteria all decreased, and soil basic respiration descended, compared with the control. The activity of soil enzymes weakened, which included urease, sucrase, proteinase, acid phosphtase, peroxidase, polyphenol oxidase and dehydrogenase. Soil biochemical intensity including ammonification, nitrification, nitrogen fixation and cellulose decomposition descended, and the circulation of C and N in mining soil inhibited. All the results showed that the weakening of microbial activity was one of major characteristics in reclaimed mining soil.

Ecology↗
PubMed2004

[Microbial eco-characterization and its restoration in copper reclaimed wasteland in red soil area of China. II. Effects on soil microbial characteristics and community structure].

Soil microbial features in Lipu copper mining and non-mine soil were studied comparatively. The results indicated that mine soil possessed obviously different microbial features such as lower microbial biomass carbon and soil basal respiration strength, Cmic/Corg decreasing, and higher microbial ecophysiological parameters qCO2, indicating that heavy metal had a depressive impact on soil microbial eco-characteristics. Biolog data showed that mine soil microbial community structure was changed obviously, the speed and quantity of carbon consuming were increased significantly, and the kinds of carbon sources which soil microorganism used were changed, led to consume much more energies for maintaining the normal needs of its life. But the utilization efficiency was lower compared with the control. All the results showed that soil microbial eco-characteristics could be used as a sensitive, effective and liable index of mine soil environment qualities.

Bacteria↗
PubMed2001

[Effect of rare earth elements on the seedling ratio of crops].

The effects of rare earth elements(REEs) on the relative seedling ratio of three crops(rice, rape and soybean) in three soil(red soil, yellow fluvo-aquic soil and yellow cinnamon soil) were studied according to OECD method, and the LC50 were obtained. Toxicity effect of REEs on rice was minimum among the crops tested. The toxicity on crops in yellow cinnamon soil was lower, whereas on soybean in yellow fluvo-aquic soil and on rape in red earth were higher.

Crops, Agricultural↗
PubMed2000

Influence of modified soils on the removal of diesel fuel oil from water and the growth of oil degradation micro-organism.

Three soils were modified with two kinds of cationic surfactants in order to increase their sorptive capabilities for organic contaminants. Sorption of diesel fuel oil in water by these modified soils had been investigated. Modified soils can effectively sorb diesel fuel oil from water. The sorption capability of modified soils is: HDTMA-black soil > HDTMA-yellow brown soil > HDTMA-red soil > TMA-black soil > TMA-yellow brown soil > TMA-red soil. Sorption of diesel fuel oil by natural soils and HDTMA modified soils is via partition, the sorption isotherms can be expressed by Henry equation, and logK(SOM) is 2.42-2.80, logK(HDTMA) is 3.37-3.60. Sorption isotherms of TMA modified soils can be expressed by Langmuir equation, the saturation sorption capacities are 1150 (TMA-black soil), 750 (TMA-yellow-brown soil), 171 mg/kg (TMA-red soil), respectively. A diesel fuel oil degradation micro-organism (Pseudomonas sp.) was isolated in the lab. To test the influence of the modified soils on the micro-organism, various growth curves of Pseudomonas in different conditions were drawn. Pseudomonas can grow very well with natural soils and TMA modified soils. The acclimation period of Pseudomonas is reduced. As to HDTMA modified soils, HDTMA loading amount is very important. When HDTMA loading amount is no higher than 0.5 CEC, the micro-organism can grow very well after a long acclimation period.

Absorption↗
PubMed2003

[Effects of simulated acid rains on Cd, Cu and Zn release and their form transformation in polluted soils].

The release and form transformation of Cd, Cu, and Zn in polluted red soil and yellow red soil affected by simulated acid rains were studied through batch equilibrium experiments. The results showed that the release of test heavy metals increased significantly with decreasing pH value of simulated acid rain. Their release amount was negatively correlated to the pH value of acid rains. In polluted red soil and yellow red soil, Cd existed mainly in exchangeable form, and Cu in organically bound and Mn oxide-occluded forms. Zn existed mainly in residual and exchangeable forms in polluted red soil, and in residual and organically bound forms in polluted yellow red soil. To some extents, the release of Cd, Cu and Zn and the chemical forms of Cd and Zn in test soils were affected by soil organic matter content and CEC. The release amount of bio-available Cd and Cu in polluted red soil and yellow red soil was increased greatly with the increasing acidity of simulated acid rains, but the transformation of Zn from stable to bio-available form was not obvious.

Acid Rain↗
PubMed2005

Adsorption and desorption characteristics of hydrophobic pesticide endosulfan in four Indian soils.

Adsorption and desorption characteristics of endosulfan in four Indian soils were studied extensively. The soils used were clayey soil (CL--lean clay with sand), red soil (GM--silty gravel with sand), sandy soil (SM--silty sand with gravel) and composted soil (PT--peat) as per ASTM (American Society for Testing and Materials) standards. Adsorption and desorption rates were calculated from kinetic studies. These values varied for alpha and beta endosulfan depending on the soil type. Maximum specific adsorption capacities (qmax) for different soils were calculated by Langmuir model. The values varied from 0.1 to 0.45 mg g(-1) for alpha endosulfan and 0.0942-0.2722 mg g(-1) for beta endosulfan. Maximum adsorption took place in clay soil followed by composted soil and red soil. Adsorptions of alpha and beta endosulfan were negligible in sand. The binding characteristics of various functional groups were calculated using Scatchard plot. Effect of functional groups was more predominant in clayey soil. Organic matter also played a significant role in adsorption and desorption of endosulfan. Endosulfan adsorption decreased drastically in clay soil when the pH was reduced. Desorption was higher at both acidic and alkaline pH ranges compared to neutral pH. Results indicated that alpha endosulfan is more mobile compared to beta endosulfan and mobility of endosulfan is maximum in sandy soil followed by red soil. It can be inferred that crystal lattice of the clay soil plays a significant role in endosulfan adsorption and desorption. Immobilization of endosulfan is more advisable in clay soil whereas biological and or chemical process can be applied effectively for the remediation of other soil types.

Adsorption↗
PubMed2006

Bioremediation of endosulfan contaminated soil and water -- optimization of operating conditions in laboratory scale reactors.

A mixed bacterial culture consisted of Staphylococcus sp., Bacillus circulans-I and -II has been enriched from contaminated soil collected from the vicinity of an endosulfan processing industry. The degradation of endosulfan by mixed bacterial culture was studied in aerobic and facultative anaerobic conditions via batch experiments with an initial endosulfan concentration of 50mg/L. After 3 weeks of incubation, mixed bacterial culture was able to degrade 71.58+/-0.2% and 75.88+/-0.2% of endosulfan in aerobic and facultative anaerobic conditions, respectively. The addition of external carbon (dextrose) increased the endosulfan degradation in both the conditions. The optimal dextrose concentration and inoculum size was estimated as 1g/L and 75mg/L, respectively. The pH of the system has significant effect on endosulfan degradation. The degradation of alpha endosulfan was more compared to beta endosulfan in all the experiments. Endosulfan biodegradation in soil was evaluated by miniature and bench scale soil reactors. The soils used for the biodegradation experiments were identified as clayey soil (CL, lean clay with sand), red soil (GM, silty gravel with sand), sandy soil (SM, silty sand with gravel) and composted soil (PT, peat) as per ASTM (American society for testing and materials) standards. Endosulfan degradation efficiency in miniature soil reactors were in the order of sandy soil followed by red soil, composted soil and clayey soil in both aerobic and anaerobic conditions. In bench scale soil reactors, endosulfan degradation was observed more in the bottom layers. After 4 weeks, maximum endosulfan degradation efficiency of 95.48+/-0.17% was observed in red soil reactor where as in composted soil-I (moisture 38+/-1%) and composted soil-II (moisture 45+/-1%) it was 96.03+/-0.23% and 94.84+/-0.19%, respectively. The high moisture content in compost soil reactor-II increased the endosulfan concentration in the leachate. Known intermediate metabolites of endosulfan were absent in all the above degradation studies.

Bacillus↗
PubMed2001

Effects of pig manure and wheat straw on growth of mung bean seedlings grown in aluminium toxicity soil.

Crop production in red soil areas may be limited by Al toxicity. A possible alternative to ameliorate Al toxicity is the application of such organic manure as crop straw and animal manure. A pot experiment was conducted to investigate the effects of organic materials on the alleviation of Al toxicity in acid red soil. Ground wheat straw, pig manure or CaCO3 were mixed with the soil and incubated, at 85% of water holding capacity and 25 degrees C, for 8 weeks. After the incubation, 14 seedlings of mung bean (Phaseolus aures Roxb) were allowed to grow for 12 days. Results showed that application of organic material or CaCO3 increased soil pH and decreased soil monomeric inorganic Al concentrations. Growth of mung bean seedling was improved sustantially by the application of organic material or CaCO3. Pig manure or wheat straw was more effective in ameliorating Al toxicity than was CaCO3. Mung bean plants receiving pig manure or wheat straw contained relatively high concentrations of P, Ca and K in their leaves. It is suggested that the beneficial effect of organic manure on mung bean is likely due to decreasing concentrations of monomeric inorganic Al concentrations in soil solution and improvement of mineral nutrition.

Aluminum↗
PubMed1974

The relationship between endemic elephantiasis of the lower legs and the local soils and climate.

The prevalence of endemic elephantiasis of the lower legs in relation to the red soil on which the barefooted population lives has been investigated. Counts of 43,573 adults attending weekly markets have been made in ten markets of which five were on the red soil, two were on the limits of the soil, and three were at a distance from this area. Prevalence falls from a maximum of 6.92% on the red soil area, to 2.96% at the limit and to 0.98% in two directions within 25 km of the edge of the red soils. There is an association between the degree of prevalence and residence on the red soils. This is discussed and the possibility of a chemical irritant absorbed in colloid form through the bare feet is suggested as an etiological factor in the disease.

Elephantiasis↗
PubMed2003

[Effects of pesticide-contamination on population size and denitrification activity of denitrifying bacteria in paddy soils].

The effects of pesticide contamination on the population size and denitrification activity of denitrifying bacteria (DNB) were studied with three types of paddy soil (Huangsong paddy soil, red earth paddy soil and purple paddy soil) treated with carbofuran, carbendazim and butachlor for four weeks. The results showed that the population size of DNB in purple paddy soil, Huangsong paddy soil and red earth paddy soil varied in the range of 59.04 x 10(4)-157.59 x 10(4), 42.89 x 10(4)-108.97 x 10(4) and 32.14 x 10(4)-75.30 x 10(4) cfu.g-1 dried soil, respectively, which was positively related to the quantity of consumed nitrate in paddy soils. The population size and denitrification activity of DNB were increased by adding carbofuran (1 mg.kg-1 dried soil) or butachlor (1 mg.kg-1 dried soil), but decreased significantly by adding 10 mg.kg-1 dried soil of butachlor, 5 mg.kg-1 dried soil of carbofuran, and 10 mg.kg-1 dried soil of carbendazim on 7th d, 14th d and 7th d, respectively.

Bacteria↗
PubMed2004

Adsorption-desorption characteristics of lead in variable charge soils.

Adsorption desorption processes of Pb at contaminated levels in two variable charge soils were investigated. The red soil (RAR) developed on the Arenaceous rock (clayey, mixed siliceous thermic typic Dystrochrept) adsorbed more Pb2+ than the red soil (REQ) derived from the Quaternary red earths (clayey, kaolinitic thermic plinthite Aquult). The maximum adsorption values (Xm) that were obtained from the simple Langmuir model were 52.6 mmol Pb2+ kg(-1) soil and 29.9 mmol Pb2+ kg(-1) soil, respectively, for the RAR and REQ. Adsorption of Pb2+ decreased soil pH by 1.10 unit for the RAR soil and 1.21 unit for the REQ soil at the highest loading. The adsorption equilibrium pH of RAR was higher than that of REQ at the same Pb2+ concentration. The distribution coefficient (Kd) of Pb in the soils decreased exponentially with increasing Pb2+ loading. Most of the adsorbed Pb2+ in the soils was not desorbed in the 0.01 mol L(-1) NaNO3 solution. After five successive extractions with NaNO3, only 0-11% of the total adsorbed Pb2+ in the RAR soil was desorbed and the corresponding value of the REQ soil was 0-19%, indicating that the RAR soil had a greater affinity for Pb2+ than the REQ soil at the same Pb2+ loading. Different mechanisms might be involved in Pb2+ adsorption/desorption at different levels of Pb2+ loading and between the two soils.

Adsorption↗