Reliable and effective techniques for removing contaminants from soil are highly desirable. However, metolachlor residue bioremediation and soil fertility improvement by Rhodospirillum rubrum (R. rubrum) in effluent after wastewater treatment have not yet been investigated. The aims of this study were to investigate the feasibility of bioremediation of metolachlor residues in soil and soil fertility improvement by R. rubrum in effluent and to explain the mechanism that R. rubrum in effluent was induced to express the regulatory gene.
Materials and methodsSoybean processing wastewater was obtained from Harbin Soybean Products Machining Factory. Soil samples were the surface soil (0–30 cm) from campus (1.77 g/kg total N, 4.15 g/kg total P, 1.58 g/kg total K, 17 g/kg SOM, 0.07 g/kg SMBC). Cytochrome P450 monooxygenase regulatory gene, MAPKKKs gene, was measured by RT-PCR.
Results and discussionCompared to control treatment, metolachlor was removed efficiently and soil fertility was remediated by effluent containing R. rubrum. The removal in concentrations reached 2.97 mg/L (99%). Soil organic matter (SOM) and SMBC were enhanced 42 times. Molecular analysis revealed that metolachlor induced cpm gene expression to synthesize cytochrome P450 monooxygenase through activating MAPKKKs gene in MAPK signal transduction pathway.
ConclusionsBioremediation of metolachlor in soil and improvement of soil fertility using R. rubrum in effluent were feasible. Metolachlor, as environmental pressure, induced cpm gene expression to synthesize cytochrome P450 monooxygenase and to remove metolachlor through activating MAPKKKs, MAPKKs, MAPKs genes in MAPK signal transduction pathway.
相似文献In this study, the pot experiments were performed to investigate that Pb and fluoranthene toxicity can be reduced and soil biological properties in co-contaminated soil can be improved by Oudemansiella radicata (O. radicata) combining with Serratia marcescens (S. marcescens).
Materials and methodsThe soil used in this study was air-dried in 25 °C and sieved through a 2-mm mesh sieve, then was artificially contaminated with the different concentrations Pb. The microbial counts, the ligninolytic enzymes (Laccase and MnP), and soil enzymes (dehydrogenase and acid phosphatase) were analyzed by different methods. The Pb accumulation in mushroom and soils samples were analyzed by using the flame atomic absorption spectrometry (FAAS, SpectrAA-220Fs, United States Varian, Inc.). Fluoranthene content was analyzed using gas chromatograph-mass spectroscopy (GC–MS, Agilent 6890, USA).
Results and discussionResults showed that Pb and fluoranthene had a negative effect on soil biological properties and mushroom. S. marcescens inoculation and O. radicata cultivation mitigated the adverse impact and improved the soil biological characteristics. S. marcescens inoculation could significantly increase the percentage of HOAc-extractable Pb and Pb concentration in O. radicata. Meanwhile, O. radicata and S. marcescens inoculation in soil could accelerate the removal of fluoranthene, and removal rate of fluoranthene was 86.39–91.95% in inoculated groups compared to 71.46–81.76% of non-inoculated groups (P?<?0.05). This study demonstrated that the interaction of O. radicata and S. marcescens was effective in promoting the bioremediation of co-contaminated soil with Pb and fluoranthene, and thus making it easier for us to detoxify the pollutants.
ConclusionsThis study investigated that potential of O. radicata and S. marcescen on the bioremediation of Pb-fluoranthene co-contaminated soil. The combined effect of O. radicata and S. marcescen could significantly promote the bioremediation of Pb-fluoranthene co-contaminated soil, especially for the twice inoculation of S. marcescen groups. These results demonstrated that the presence of O. radicata and S. marcescen could significantly promote the bioremediation of Pb-fluoranthene co-contaminated soil, especially for the twice inoculation of S. marcescen groups.
相似文献The bioavailability of potassium (K) depends on its speciation distribution in the soil. Different methods are commonly used to estimate K speciation including traditional single leaching (TSL) and sequential extraction process (SEP). However, K speciation is largely affected by soil pretreatment methods. The effects of both TSL and SEP soil pretreatment methods were evaluated.
Materials and methodsThe TSL method classifies K speciation content based on bioavailability, while the SEP classifies the metal speciation based on the effects of environmental conditions. These two methods, together with a modified sequential single leaching (SSL) scheme, were used to evaluate five types of soil including soil without potassium fertilization, soil with long-term K fertilization, alkaline soil, red soil, and forest soil. The soil samples were gathered randomly at depths varying up to 30 cm before being dried in air at room temperature. The samples were then ground and mixed before passing through a sieve (10 mesh or 100 mesh) in order to perform K speciation analysis via the modified SSL technique, the TSL method, and the four schemes of SEP.
Results and discussionSoil pretreatment influenced K speciation, with higher concentration in soil samples sieved through 100 mesh than through 10 mesh. In alkaline soil, potassium was observed to be associated with carbonate. For the various SEP schemes, K speciation was found to be greatest in the residual fraction, with only 3% observed in the carbonate, exchangeable, metal organic complex, or amorphous hydroxides of Fe or Mn. After following the first two steps of the SEP schemes, the available K was similar to that of the TSL method. Distribution of non-exchangeable K using the TSL method was comparable with the five combined SEP extraction steps which were all affected by environmental conditions.
ConclusionsPretreatment affected K speciation distribution and total amount of metal in the soil. The 100 mesh sieve was more effective in estimating K soil speciation. The SEP method was acceptable for estimating K speciation, with the Krishnamurti et al. (Analyst 120:659–665, 1995) scheme as a useful appraisal of K bioavailability. Combination analyses using both TSL and SEP methods are useful techniques to enable a better understanding of K speciation transformation in soil.
相似文献It is very important to obtain the information on the soils capacity to immobilize HMs and distribute them among soil components. The aim of this work was to study the fractional composition of Cu compounds in Haplic chernozem under model contamination conditions using different fractionation methods.
Materials and methodsThe fractional composition of copper compounds in Haplic Chernozem artificially contaminated with copper acetate has been studied under model experimental conditions. General regularities and differences in the distribution of Cu forms in soils at the use of sequential fractionation by the Miller method modified by Berti and Jacobs (1996) and the Tessier method (Tessier et al. 1979) are revealed.
Results and discussionThe differences are related to the metal affinity for specific carrier phases, as well as to the selectivity and extraction capacity of the reagents used in these methods. A significant increase in the most mobile exchangeable Cu fraction is observed in contaminated soils. Aluminosilicates and soil organic matter make the largest contribution to the adsorption and retention of Cu.
ConclusionsThe Tessier method is more suitable for the separation of the total technogenic component from contaminated soils. The Miller method is more informative at the determination of loosely bound HM compounds because of the use of weaker extractants.
相似文献Accounting for ionic strength and ion association, the degree of calculated supersaturation with CaCO3 of gleyic solonetz and molic solonetz soil solution is high. The purpose of the research was to reveal the effect of the water-dissolved organic matter (DOM) on the calcium carbonate equilibrium (CCE) in soil solution, to create a thermodynamic model of carbonate association and complexation with DOM and heavy metals (HMs), and to correct the principal of soil management.
Materials and methodsObject of research—Kastanozem complex of the dry steppe, Rostov Oblast, Russia. The water extraction of soluble salts was made at the water-to soil-ratio 5:1 and analyzed using standard methods. DOM content was determined by Strosser (J Agrobiol 27:49–60, 2010). The soil solution macro-ion equilibrium composition was calculated using ION-2 program (Endovitsky et al. 2009). DOM role in soil solution supersaturation with СаСО3 was assessed, comparing C content in real solution and in identical artificial solution prepared without organic matter. Taking into account the ion association, the molar fractions of free and bound HM ion were calculated using microelement association coefficient, kas(ME). The soil liquid-phase saturation with CaCO3 was characterized by the ratio of the real solubility product (S) to the thermodynamic solubility product (S0): К?=?S/S0.
Results and discussionThe soil solution supersaturation with CaCO3 was characterized by the product of analytical concentrations (S), equilibrium concentrations [accounting ion activity (SI), ion association (SII), ion association and complexation (SIII)], and the thermodynamic solubility product (S0). To evaluate the role of DOM in soil solution supersaturation with CaCO3, the initial pure Ca (HCO3)2 solution series was prepared. The humic and fulvic acids from the illuvial horizon of gleyic solonetz with concentrations of 20 mg C L?1 and 120 mg C L?1 decreased the CaCO3 precipitation compared with initial soil solution. The release of CaCO3 from soil water extracts containing water-soluble organic matter was 1.2–1.9 times less compared with identical artificial solution not containing organic matter. The HM binding by carbonates is proportional to the DOM content.
ConclusionsIn molic solonetz and gleyic solonetz, the neutralization of the soda should be assessed by the soil solution supersaturation with CaCO3. To calculate the degree of HM passivation in soil solution containing DOM, the coefficient of soil solution oversaturation with CaCO3 is proposed. For reducing soil organic matter and DOM mobility and loss from soil, as well as for Pb passivation, intra-soil mechanical processing, intra-soil waste management, and intra-soil watering are proposed.
相似文献The application of sludge from wastewater in agriculture has increased in recent years, and it is therefore important to assess the effect that such treatment has on both the soil and the plant. The aim of the study described here was to ascertain whether there is a variation in the properties of the soil and to determine if this addition has an impact on the plant.
Materials and methodsThe area of investigation was close to the municipality of Villarrubia de los Ojos (Ciudad Real). In this work, six samples were taken from the surface horizon in the studied plot at a depth of 35 cm. A further three samples were taken: (i) a surface horizon of a soil close to the area under investigation but without treatment (control sample), (ii) a sample of sludge from the wastewater treatment plant and (iii) a sample of the mixture used by farmers as fertilizer. Laboratory tests were conducted in accordance with the SCS-USDA (1972) guidelines. Trace element samples were analysed by X-ray fluorescence spectrophotometry (Philips PW 2404).
Results and discussionThe parcel of land studied is dominated by a sandy texture (88.3 % sand), and a decrease in pH was observed in areas in which the mixture (manure + sludge) was added (pH?=?8.0) compared to areas in which fertilizer was not applied (pH?=?8.5). It was observed that the addition of the compound led to an increase in the electrical conductivity of the soil. The trace elements can be organized into two groups based on the results obtained in this study. One group contains the trace elements that were only present in the rows that were treated with the fertilizer. The other group of trace elements was mobilized throughout the whole plot.
ConclusionsThe application of sewage sludge on agricultural soils can be very useful as an organic amendment because it produces an increase in soil organic matter. However, sewage sludge must be applied with caution due to the changes in soil chemical properties (for example, pH and E.C.). The use of this type of waste for prolonged periods of time can cause problems of contamination in the soil.
相似文献Elevated CO2 and nitrogen (N) addition both affect soil microbial communities, which significantly influence soil processes and plant growth. Here, we evaluated the combined effects of elevated CO2 and N addition on the soil–microbe–plant system of the Chinese Loess Plateau.
Materials and methodsA pot cultivation experiment with two CO2 treatment levels (400 and 800 μmol mol?1) and three N addition levels (0, 2.5, and 5 g N m?2 year?1) was conducted in climate-controlled chambers to evaluate the effects of elevated CO2 and N addition on microbial community structure in the rhizosphere of Bothriochloa ischaemum using phospholipid fatty acid (PLFA) profiles and associated soil and plant properties. Structural equation modeling (SEM) was used to identify the direct and indirect effects of the experimental treatments on the structure of microbial communities.
Results and discussionElevated CO2 and N addition both increased total and fungal PLFAs. N addition alone increased bacterial, Gram-positive, and Gram-negative PLFAs. However, elevated CO2 interacting with N addition had no significant effects on the microbial community. The SEM indicated that N addition directly affected the soil microbial community structure. Elevated CO2 and N addition both indirectly affected the microbial communities by affecting plant and soil variables. N addition exerted a stronger total effect than elevated CO2.
ConclusionsThe results highlighted the importance of comprehensively studying soil–microbe–plant systems to deeply reveal how characteristics of terrestrial ecosystems may respond under global change.
相似文献This investigation assessed the responses of soil fertility, enzyme activity, and microbial community diversity to soil texture and land use type.
Materials and methodsThe tested soils included five soil textures (sandy loam, medium loam, heavy loam, light clay, and medium clay soils) with two land use types (uncultivated and paddy soils) in the coastal zone of Zhejiang Province, China.
Results and discussionSoil texture had a significant effect on soil pH, electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), available nitrogen (AN), phosphorus (AP) and potassium (AK), catalase and protease activities, total phospholipid fatty acids (PLFAs), bacterial and actinomycetes PLFAs, and microbial diversity (MD). The clay content was significantly positively correlated to soil EC, OC, TN, AN, AP, AK, catalase activity, total PLFAs, bacterial and actinomycetes PLFAs, and MD but significantly negatively associated with soil pH and protease activity. Land use type also had significantly influenced soil pH, EC, OC, TN, AN, AP, AK, catalase, protease and urease activities, total PLFAs, bacterial, actinomycetes, and fungal PLFAs, and MD. The paddy soil had higher OC, TN, AN, AP, catalase, protease and urease activities, total PLFAs, bacterial and actinomycetes PLFAs, and MD but lower soil pH, EC, and AK than the uncultivated soil. The interaction with soil texture and land use type had significantly affected soil pH, EC, OC, TN, AN, AP, AK, catalase and protease activities, total PLFAs, bacterial and actinomycetes PLFAs, and MD.
ConclusionsSoil texture and land use type could be considered important factors in improving soil fertility, enzyme activity, and microbial diversity in coastal saline soils.
相似文献Rhizoremediation is a complex type of green clean-up technology that involves both plants and the rhizosphere-associated microorganisms to decompose hazardous compounds. The success of the strategy strongly depends on plant tolerance towards the pollutant, as well as plant's interactions with the rhizospheric microbes. The microorganisms may be stimulated by the secreted root exudates, which results in an increased breakdown of contaminants in the rhizosphere. The main goal of this study was to establish a potential rhizoremediation combination for a diesel-polluted site. Inoculation of plant roots or seeds with indigenous rhizospheric populations is a common approach in the rhizoremediation. However, we introduced hydrocarbon-degrading consortia (M10, R3, and K52) that were previously isolated from crude oil-contaminated soil instead of indigenous microbes. Bioaugmentation with these petroleum degraders was applied to screen four high biomass crop species (Indian mustard, alfalfa, high erucic acid rapeseed, HEAR, and low erucic acid rapeseed, LEAR) for their tolerance towards diesel oil. At no pollution, a promoting effect of M10 bacteria could be observed on germination and root elongation of all plant species. Moreover, M10 consortiums increased the germination index at 6,000 mg diesel oil per kilogram dry soil in the case of Indian mustard, alfalfa, and HEAR. The latter species was found to increment its dry weight upon bioaugmentation with M10 bacteria and all diesel oil treatments (6,000 and 24,000 mg diesel oil per kilogram dry soil). The initial results indicate HEAR and the M10 bacterial consortium as a promising plant–microbe tandem for a long-term rhizoremediation process.
相似文献Heavy metals’ contamination of soil is a serious concern as far as public health and environmental protection are concerned. As a result of their persistent and toxic properties, heavy metals need to be removed from contaminated environments using an efficient technology. This study is aimed to determine the heavy metals’ (Ni, Pb, and Zn) bioremoval capacity of consortia of filamentous fungi from landfill leachate-contaminated soil.
Materials and methodsThree different groups of consortia of fungi, namely all isolated fungi, Ascomycota, and Basidiomycota, were employed for the bioremediation of the contaminated soil. A total of thirteen fungal species were used to make up the three consortia. The setup was kept for 100 days during which regular watering was carried out. Soil subsamples were collected at day 20, day 60, and 100 for monitoring of heavy metal concentration, fungal growth, and other physicochemical parameters.
Results and discussionHighest tolerance index of 1.0 was recorded towards Ni and Zn concentrations. The maximum metal bioremoval efficiency was observed for soil bioaugmented with the all isolated fungi for Ni and Pb with the removal efficiencies as 52% and 44% respectively. However, 36% was realized as the maximum removal for Zn, and was for Ascomycota consortium-treated soil. The order for the heavy metal removal for Ni and Pb is all isolated fungi > Basidiomycota?>?Ascomycota, while for Zn is Basidiomycota?>?all isolated fungi > Ascomycota. Spectra analysis revealed the presence of peaks (1485–1445 cm?1) only in the consortia-treated soil which corresponded to the bending of the C–H bond which signifies the presence of methylene group.
ConclusionsSoil treated using bioaugmentation had the best heavy metal removal as compared to that of the control. This suggests the contribution of fungal bioaugmentation in the decontamination of heavy metal–contaminated soil.
相似文献Variation in soil microbial metabolism remains highly uncertain in predicting soil carbon (C) sequestration, and is particularly and poorly understood in agroecosystem with high soil phosphorus (P) variability.
Materials and methodsThis study quantified metabolic limitation of microbes and their association with carbon use efficiency (CUE) via extracellular enzymatic stoichiometry and biogeochemical equilibrium models in field experiment employing five inorganic P gradients (0, 75, 150, 225, and 300 kg P ha?1) in farmland used to grow peas.
Results and discussionResults showed P fertilization significantly increased soil Olsen-P and NO3?-N contents, and enzyme activities (β-1,4-glucosidase and β-D-cellobiosidase) were significantly affected by P fertilization. It indicated that P fertilization significantly decreased microbial P limitation due to the increase of soil available P. Interestingly, P application also significantly decreased microbial nitrogen (N) limitation, a phenomenon primarily attributable to increasing NO3?-N content via increasing biological N fixation within the pea field. Furthermore, P fertilization increased microbial CUE because the reduction in microbial N and P limitation leads to higher C allocation to microbial growth. Partial least squares path modeling (PLS-PM) further revealed that the reduction of microbial metabolic limitation is conducive to soil C sequestration.
ConclusionsOur study revealed that P application in agroecosystem can alleviate not only microbial P limitation but also N limitation, which further reduces soil C loss via increasing microbial CUE. This study provides important insight into better understanding the mechanisms whereby fertilization mediates soil C cycling driven by microbial metabolism in agricultural ecosystems.
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