Biodegradation of endosulfan by a soil bacterium

A bacterium capable of metabolizing endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine3-oxide) was isolated from cotton-growing soil and effectively shown to degrade endosulfan into endosulfan sulfate. The bacterium degraded 50% of the compound within 3 days of incubation. Endosulfan sulfate was the only terminal product and no other metabolites were formed during the incubation. Endosulfan and its metabolites were analyzed by gas chromatography. The metabolites formed indicated that the organism follows an oxidative pathway for metabolism of this pesticide. Therefore, the present study, microbial degradation of endosulfan by a soil bacterium, may provide a basis for the development of bioremediation strategies to remediate the pollutants in the environment.     

Biodegradation of endosulfan by Mortieralla sp. strain W8 in soil: Influence of different substrates on biodegradation

To examine the bioremediation potential of Mortierella sp. strain W8 in endosulfan contaminated soil, the fungus was inoculated into sterilized and unsterilized soil spiked with endosulfan. Wheat bran and cane molasses were used as substrates to understand the influence of different organic materials on the degradation of endosulfan in soil. Strain W8 degraded α- and β-endosulfan in both sterilized and unsterilized soil. In unsterilized soil with wheat bran+W8, α- and β- endosulfan were degraded by approximately 80% and 50%, respectively after 28 d incubation against the initial endosulfan concentration (3 mg kg(-1) dw). The corresponding values for α- and β-endosulfan degradation with wheat bran only were 50% and 3%. Endosulfan diol metabolite was detected after 14 d incubation in wheat bran+W8 whereas it was not found with wheat bran only. Production of endosulfan sulfate, the main metabolite of endosulfan, was suppressed with wheat bran+W8 treatment compared with wheat bran only. It was demonstrated that wheat bran is a more suitable substrate for strain W8 than cane molasses. Wheat bran+W8 is a superior fungus and substrate mix for bioremediation in soil contaminated with endosulfan.     

Biodegradation of soil‐applied endosulfan in the presence of a biosurfactant

Abstract

Biodegradation of endosulfan isomers in soil‐applied and flask‐coated conditions was studied, by an isolated bacterial coculture. The degradation in soil‐applied form was 20–30% slower than in flask‐coated condition. Addition of a biosurfactant, isolated from Bacillus subtilis MTCC 1427, enhanced the rate of biodegradation by 30–45% in both the conditions. It also mobilized the residual endosulfan towards biodegradation, that otherwise remains undegraded.     

DDT uptake by arbuscular mycorrhizal alfalfa and depletion in soil as influenced by soil application of a non-ionic surfactant

A greenhouse pot experiment was conducted to investigate the colonization of alfalfa roots by the arbuscular mycorrhizal (AM) fungus Glomus etunicatum and application of the non-ionic surfactant Triton X-100 on DDT uptake by alfalfa and depletion in soil. Mycorrhizal colonization led to an increase in the accumulation of DDT in roots but a decrease in shoots. The combination of AM inoculation and Triton X-100 application enhanced DDT uptake by both the roots and shoots. Application of Triton X-100 gave much lower residual concentrations of DDT in the bulk soil than in the rhizosphere soil or in the bulk soil without Triton X-100. AM colonization significantly increased bacterial and fungal counts and dehydrogenase activity in the rhizosphere soil. The combined AM inoculation of plants and soil application of surfactant may have potential as a biotechnological approach for the decontamination of soil polluted with DDT.     

Biodegradation of phthalate esters in polluted soil by using organic amendment

This study investigated the biodegradation of the phthalate esters (PAEs) di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) in sludge and sludge-amended soil. DBP (100 mg kg^?1) and DEHP (100 mg kg^?1) were added to sewage sludge, which was subsequently added to soil. The results showed that sewage sludge can degrade PAEs and the addition of sewage sludge to soil enhanced PAE degradation. Sludge samples were separated into fractions with various particle size ranges, which spanned 0.1–0.45 μm to 500–2000 μm. The sludge fractions with smaller particle sizes demonstrated higher PAE degradation rates. However, when the different sludge fractions were added to soil, particle size had no significant effect on the rate of PAE degradation. The results from this study showed that microbial strains F4 (Rhodococcus sp.) and F8 (Microbacterium sp.) were constantly dominant in the mixtures of soil and sludge.     

Biodegradation of phthalate esters in polluted soil by using organic amendment

This study investigated the biodegradation of the phthalate esters (PAEs) di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) in sludge and sludge-amended soil. DBP (100 mg kg(-1)) and DEHP (100 mg kg(-1)) were added to sewage sludge, which was subsequently added to soil. The results showed that sewage sludge can degrade PAEs and the addition of sewage sludge to soil enhanced PAE degradation. Sludge samples were separated into fractions with various particle size ranges, which spanned 0.1-0.45 μm to 500-2000 μm. The sludge fractions with smaller particle sizes demonstrated higher PAE degradation rates. However, when the different sludge fractions were added to soil, particle size had no significant effect on the rate of PAE degradation. The results from this study showed that microbial strains F4 (Rhodococcus sp.) and F8 (Microbacterium sp.) were constantly dominant in the mixtures of soil and sludge.     

Persistence of alpha and beta isomers of endosulphan and endosulphan sulphate in diverse soils of India as influenced by flooding

Laboratory studies were undertaken to evaluate the persistence of alpha-endosulphan, beta-endosulphan and endosulphan sulphate in four diverse soils under non-flooded and flooded conditions. Significant variations were observed in the extent of persistence of the three chemicals in different non-flooded soils with maximum persistence observed in Alfisol and the least in Mollisol having near neutral pH and higher organic matter. Degradation was more in all the flooded soils than in the non-flooded counterpart but in Vertisol under flooded and non-flooded conditions, the rate of degradation of endosulphan sulphate was found to be nearly same.     

Sorption of alpha and beta hydrophobic endosulfan in a Vertisol from southeast region of Turkey

Endosulfan has been applied to control numerous insects in a variety of food and non-food crops. Limited information is available on dynamics of this pesticide in the soil. The objective of this research was to determine the adsorption–desorption behavior of the alpha (α) and beta (β) endosulfan in a Vertisol from the southeast region of Turkey, where cotton is the main crop in the large irrigated lowlands. The α and β endosulfan were adsorbed considerably and Freundlich adsorption–desorption isotherms fitted the α and β endosulfan data (R² > 0.98). Freundlich adsorption coefficients (K_f) for the α endosulfan ranged between 21.63 and 16.33 while for the β endosulfan they were between 14.01 and 17.98 for the Ap and Bw2 horizons. The difference of K_f values of α and β endosulfan for two horizons were explained with the slight difference in the amount of organic matter and clay, but considerable difference in Fe contents of the two horizons. Alpha and β endosulfan K_fd values were 118.03 and 45.81 for the Ap and 48.08 and 68.71 for the Bw2 horizons. Higher adsorption and desorption behavior of the endosulfan isomers for the same horizon was attributed to poor physical bonding between the endosulfan molecule and the surfaces of fundamental soil particles. This fact is thought to increase the effective use of endosulfan in agriculture with a possibility of its movement to the surface and groundwater in the Vertisol studied.     

Biodegradation of alpha and beta isomers of endosulphan and endosulphan sulphate in Indian soils

The degradation of alpha and beta isomers of endosulphan and endosulphan sulphate in four sterilized and non sterilized Indian soils under laboratory conditions was studied. Degradation was found to be more in non-sterilized as compared to the sterilized soil. The half life of alpha-endosulphan, beta-endosulphan and endosulphan sulphate was found to be 136.8, 273 and 301 days in sterilized Alfisol and 55, 256 and 277 days in non-sterilized Alfisol,respectively. Alpha-endosulphan degraded more readily than beta-endosulphan and endosulphan sulphate under both sterilized and non-sterilized soil conditions.     

不同有机物料对次生盐渍化设施土壤的修复效果研究

在设施大棚内,将不同用量的有机物料(商品有机肥、稻草、砻糠)还田栽培"春光"西瓜,研究有机物料对设施土壤盐渍化的防治效果。在连续2年4季的设施栽培过程中,分5次采集土壤样品,测定土壤有机质、全盐量、电导率(EC)、容重、孔隙度、最小持水量等物理化学性状指标。结果表明,有机物料对改善设施土壤次生盐渍化有一定作用,不仅降低了土壤全盐量和EC,提高土壤有机质含量,还可改善设施土壤结构,降低土壤容重,提高总孔隙度,改善土壤的水气矛盾。其中,高用量(9 000kg/hm2)砻糠处理组对设施土壤盐渍化修复效果最佳,土壤硝酸盐比单施无机肥料的对照组降低67.1%,有机质提高41.9%,最小持水量提高43.6%,土壤总孔隙度提高32.3%。     

Migration of heavy metals in soil as influenced by compost amendments

Soils contaminated with heavy metals can pose a major risk to freshwaters and food chains. In this study, the success of organic and inorganic intervention strategies to alleviate toxicity in a highly acidic soil heavily contaminated with As, Cu, Pb, and Zn was evaluated over 112 d in a mesocosm trial. Amelioration of metal toxicity was assessed by measuring changes in soil solution chemistry, metal leaching, plant growth, and foliar metal accumulation. Either green waste- or MSW-derived composts increased plant yield and rooting depth, reduced plant metal uptake, and raised the pH and nutrient status of the soil. We conclude that composts are well suited for promoting the re-vegetation of contaminated sites; however, care must be taken to ensure that very short-term leaching pulses of heavy metals induced by compost amendment are not of sufficient magnitude to cause contamination of the wider environment.     

Persistence of seven pesticides as influenced by soil moisture1

Abstract

Pesticides are often applied in combination, but less‐often is soil persistence measured this way. The present field and laboratory study determined relative persistence of five herbicides and two insecticides, co‐applied, as a function of three soil water contents. Losses were modeled adequately by first‐order dissipation, with no significant improvement by using a two‐compartment model. The order of persistence in a silt loam, at 25% moisture, was carbofuran < cyanazine < metribuzin = alachlor < atrazine < ethoprop < metolachlor (t_½ ranged from 7–91 days). Carbofuran degradation increased greatly from 12–25% soil moisture; atrazine was unaffected by 12–35%, whereas the remaining compounds showed limited increasing loss in wetter soil. Field‐based persistence was more variable, but generally similar to lab rankings.     

Biodegradation of polystyrene-graft-starch copolymers in three different types of soil

Materials based on polystyrene and starch copolymers are used in food packaging, water pollution treatment, and textile industry, and their biodegradability is a desired characteristic. In order to examine the degradation patterns of modified, biodegradable derivates of polystyrene, which may keep its excellent technical features but be more environmentally friendly at the same time, polystyrene-graft-starch biomaterials obtained by emulsion polymerization in the presence of new type of initiator/activator pair (potassium persulfate/different amines) were subjected to 6-month biodegradation by burial method in three different types of commercially available soils: soil rich in humus and soil for cactus and orchid growing. Biodegradation was monitored by mass decrease, and the highest degradation rate was achieved in soil for cactus growing (81.30 %). Statistical analysis proved that microorganisms in different soil samples have different ability of biodegradation, and there is a significant negative correlation between the share of polystyrene in copolymer and degree of biodegradation. Grafting of polystyrene on starch on one hand prevents complete degradation of starch that is present (with maximal percentage of degraded starch ranging from 55 to 93 %), while on the other hand there is an upper limit of share of polystyrene in the copolymer (ranging from 37 to 77 %) that is preventing biodegradation of degradable part of copolymers.     

Biodegradation of fluoranthene by soil fungi

A selection of 39 strains of micromycetes known as good degraders of polychlorinated aromatic compounds, mostly isolated from soil and belonging to various taxonomic groups, have been investigated for fluoranthene degradation. Toxicity assays, first evaluated on solid medium MEA, have not shown any toxicity of fluoranthene (1-100 mg.L-1) towards fungi. Whereas, consumption assays on a solid synthetic medium showed a toxicity at 100 mg.L-1. The degradation of fluoranthene (10 mg.L-1) was then investigated in a liquid synthetic medium for 4 days and evaluated by HPLC. Among the 39 strains tested, 18 degraded fluoranthene at 60% or more. Zygomycetes appeared to be the most efficient group (mean degradation: 90%). Among 18 performant strains, 10 had not yet been reported in the literature: Sporormiella australis, Cryptococcus albidus, Cicinobolus cesatii, Pestalotia palmarum, beauveria alba, Aspergillus terreus. Cunninghamella blakesleeana, C. echinulata, Mortierella ramanniana and Rhizopus arrhizus. Fluoranthene adsorption on fungi was very low for the strains which degraded well fluoranthene (mean adsorption: 4%). Whereas, some strains adsorbed it much more such as Colletotrichum dematium (47%) and Penicillium italicum (43%).     

Leaching and reduction of chromium in soil as affected by soil organic content and plants

The oxidation state of chromium in contaminated soils is an important indicator of toxicity and potential mobility. Chromium in the hexavalent state is highly toxic and soluble, whereas the trivalent state is much less toxic and relatively insoluble. A laboratory study investigated the impact of growing plants and supplemental organic matter on chromium transport in soil. Plants alone had no appreciable effect on the chromium oxidation state in soil. Soil columns with higher organic content were associated with lower ratios of chromate:total chromium than the columns with lower organic matter. Analyses of column leachate, plant biomass, and soil indicate that more chromium leaching occurred in the vegetated, low organic columns. Retention of Cr in the soils was correlated to the Cr(III) content. Plant uptake of chromium accounted for less than 1% of the chromium removed from the soil. Overall, the addition of organic matter had the strongest influence on chromium mobility.     

Sulphur status in some Swedish podzols as influenced by acidic deposition and extractable organic carbon

To evaluate the changes in sulphur pools in response to acidic deposition, two studies were made-one in southwest Sweden where podzolic B horizons originally sampled in 1951 were resampled in 1989. At the Norrliden site, northern Sweden, sulphur pools in control plots were compared to plots that had been subjected to H(2)SO(4) application between 1971 and 1976. The results show that in southwest Sweden neither organic S nor extractable SO(4)(2-) increased significantly over the 38-year period, despite a decreasing pH and a high S deposition. At Norrliden, about 37% of the applied S was still remaining in the upper and central parts of the Bs horizon, most of which was inorganic sulphate. These contrasting results are explained by intrinsic differences in the soil organic carbon status between the sites-in southwest Sweden, organic carbon concentrations were high which inhibited SO(4)(2-) adsorption. Low organic carbon concentrations and high extractable Fe/Al concentrations promoted SO(4)(2-) adsorption and caused a low subsequent SO(4)(2-) desorption rate at the Norrliden site. The results suggest that sulphate adsorption may be an important mechanism which delays the response in soil chemistry to H(2)SO(4) deposition, provided that soil organic carbon concentrations are low. Organic S retention was not shown to be an important S retention mechanism in any of the sites studied.     

Biodegradation of cyclodextrins in soil

Cyclodextrins, especially random methylated betaCD (RAMEB) and hydroxypropyl betaCD (HPbetaCD), are becoming common enhancing additives in the bioremediation of soils formerly contaminated by hydrocarbons and/or other poorly bioavailable organic pollutants. Therefore, their degradation in the soil, particularly the most persistent RAMEB, has been of great concern. Like oil contaminants, these additives should be biodegradable via an environmentally safe technology. Hence, in this paper, the biodegradability of eight different cyclodextrins (CDs) in four different soils was examined under various treatment conditions in laboratory and pilot scale field experiments. This paper is the first report on the potential biological fate of CDs studied under a large variety of environmental conditions and in different soil ecosystems. Data on the potential relationship between CD biodegradation and the biological removal of hydrocarbons in the CD-amended contaminated soils are also given. All CDs were found to be more or less biodegradable; even the most persistent RAMEB was depleted from soils under favourable conditions. In the field experiments, the depletion of RAMEB to about 40% of its initial level was observed for a period of 2 years in hydrocarbon-contaminated soils of high organic matter and cell concentration.     

Biodegradation of nonylphenol in soil

We investigated the effects of various factors (brij 30, brij 35, yeast extract, hydrogen peroxide and compost) on the aerobic degradation of nonylphenol (NP) in soil and characterized the structure of the microbial community in that soil. Residues of NP were measured using gas chromatography-mass spectrometry (GC-MS) and a change of microbial communities was demonstrated using denaturing gradient gel electrophoresis (DGGE). The results showed that Taichung sandy clay loam had higher NP degradation rate than Kaoshiung silty clay. The addition of compost, yeast extract (0.5 mg/l), brij 30 (55 microM), or brij 35 (91 microM) enhanced NP degradation, while the addition of hydrogen peroxide (1.0 mg/l) inhibited its degradation. We also found that the addition of various substrates changed the microbial community in the soils. Cytophaga sp. and Ochrobactrum sp. were constantly dominant bacteria under various conditions in the soil.     

Axi-symmetric simulation of soil vapor extraction influenced by soil fracturing

Fracturing, either pneumatic or hydraulic, is a method to improve the performance of soil vapor extraction (SVE) in relatively low permeability soils (< 10(-5) cm/s). A two-dimensional model is presented to simulate trichloroethylene (TCE) soil vapor extraction modified by fracturing. Flow and transport is modeled using mobile macropore and micropore networks, which also have been identified in the literature as dual porosity, dual permeability, or heterogeneous flow models. In this model, fluids can flow in both the macropore and micropore networks. This represents a more general model compared to immobile micropore, mobile macropore models presented thus far in the literature for vapor flow and transport in two dimensions. The model considers pressure- and concentration-driven exchange between the macropore and micropore networks, concentration-driven exchange between the gas and sorbed phases within each network, and equilibrium exchange between the gas and water and a sorbed phase within each network. The parameters employed in an example simulation are based on field measurements made at a fractured site. Considered in the simulations were the influence of the volume percentage of fractures, the length of fractures, the relative location of the water table, and the influence of pulsed pumping. For these simulations, internetwork concentration-driven exchange most significantly affected mass removal. The volume percentage of fractures more significantly influence flow and mass removal than the length of fractures. The depth of the water table below the contamination plume only significantly influenced flow and mass removal when the water table was within 60 cm of the bottom of the contaminated soil in the vadose zone for the parameters considered in this study. Pulsed pumping was not found to increase the amount of mass removed in this study.