1,720,979 research outputs found
Relationship between changes of soil microbial biomass content and imazamox and benfluralin degradation
No full textElimination reactions of 1,2-diaryl-1-chloroethanes promoted by sodium ethoxide in ethanol. The kinetic effects of alpha- and beta-phenyl substituents
No full textRimsulfuron in soil: effect of persistence on growth and activity of microbial biomass at varying environmental conditions
No full textComparison among different extractants for the determination of soluble sulphate in alkaline soil
No full textRelationship between rimsulfuron degradation and microbial biomass content in a clay-loam soil
No full textBiochemical parameter changes in urban waste compost used as a biofilter for pesticide decontamination
No full textUrban-waste compost (UWC) can be used as a biofilter filling to reduce the effects of pesticide spills. Here, water that was contaminated by three different pesticides, the insecticide chlorpyrifos (Chl), the fungicide metalaxyl (Meta) and the herbicide glyphosate (Gly), was percolated through 2 kg of UWC material. The pesticide residues in the leached water and the modifications induced in some of the UWC biochemical and microbiological parameters (including microbial biomass carbon (MBC) and nitrogen (MBN), and fluorescein diacetate (FDA) hydrolysis, alkaline monophosphatase (AMP) and dehydrogenase (DH) activities) were investigated over 2 months of incubation at 20 degrees C. The UWC showed a good retention capacity towards the three pesticides tested, with the highest efficiency for Gly. Chl caused an initial detrimental effect on the MBC content and a decrease in the FDA hydrolysis capacity, while Meta and Gly increased the MBC content throughout the incubation. The results demonstrate that UWC can be successfully used as a biofilter to reduce pesticide spills and to clean up water contaminated with pesticides. The evaluation of the modifications induced on the UWC MBC and MBN, and FDA hydrolysis, AMP and DH activities suggest different biodegradation potentials of the UWC micro-organisms vs. the three pesticides studied
The effect of the initial concentration, co-application and repeated applications on pesticide degradation in a biobed mixture
No full textA 180 d laboratory experiment was conducted to investigate the degradation rates of chlorpyrifos (10 and 50 mg kg(-1)) and metalaxyl (100 mg kg(-1)) separately and co-applied in a biomix constituted by topsoil, vine-branches and urban-waste-garden compost. The effect of repeated application of metalaxyl was also investigated. Microbial biomass-C (MBC) content and metabolic quotient (qCO(2)) were measured to evaluate changes in microbial biomass size and activity induced by the presence of the two pesticides.Degradation rate decreased with increasing concentration of chlorpyrifos in all treatments. Metalaxyl half-life was significantly reduced in co-application with chlorpyrifos indicating a synergic interaction between the two pesticides in favour of enhanced degradation rate for metalaxyl but not for chlorpyrifos. Furthermore, repeated application resulted in a sharp reduction of metalaxyl half-life from 37 d after first application to 4 d after third application.MBC content was negatively influenced by the addition of pesticides but it started to recover immediately, in both separate and co-applied treatments, reaching the control value when pesticide residues were about 50% of the initial concentration. The qCO(2) reached a steady-state after about 20 d in separately applied and 40 d in co-applied treatments, indicating a tendency to arrive at a new metabolic equilibrium.In conclusion, the biomix tested has been shown to degrade pesticides relatively fast and to have a microbial community that is varied enough to allow selection of those microorganisms able to degrade metalaxyl and chlorpyrifos. (c) 2008 Elsevier Ltd. All rights reserved
Changes in physico-chemical and biochemical parameters of soil following addition of wood ash: a field experiment
No full textHere we have investigated the effects of the addition of two different wood ash sizes at two different doses (5 and 20 t/ha) on the physicochemical,
microbiological and biochemical properties in the surface soil (0–30 cm) of an Italian agricultural system. Over 24 months, the pH,
electrical conductivity, soil microbial biomass-C and -N, and total hydrolytic activity were periodically tested, together with alkaline phosphatase,
arylsulphatase and o-diphenoloxidase activities. Analysis of variance (ANOVA) was performed to consider the effects of sampling time and wood
ash addition on the parameters tested and to reveal possible interactions between the two variables. For electrical conductivity, pH, soil microbial
biomass-C and total hydrolytic activity the ANOVA showed a significant ‘wood ash type× sampling time’ interaction, while no interaction was
found for the other enzymatic activities. Significant increases in pH and in electrical conductivity were seen over the first months in all of the
treated samples, which were more pronounced at the higher dose. Decreases in microbial biomass-C and changes in the microbial C/N ratios were
seen for all of the treatments, which were more pronounced at the higher dose. Increases in soil microbial activity were seen over the first 8 months.
The alkaline phosphatase and arylsulphatase activities were significantly inhibited for the first 4 months of soil treatment. The significant increases
seen in o-diphenoloxidase activity over the first 8 months under all of the treatments appear to be related to the increases in electrical conductivity.
After 12 months, the levels of all of the parameters tested in the treated soils returned to the levels of the untreated soils indicating that the disposal
of up to 20 t/ha of wood ash per year in Italian agricultural soil does not result in long-term changes in any of these parameters
Biomassbed: a biological system to reduce pesticide point contamination at farm level
No full textA potential method for cleaning water from point-source pollution by organic compounds is using biological reactors. In this study, four reactors were tested for their ability to retain and degrade pesticides. The pesticides tested were the insecticide chlorpyrifos, the fungicide metalaxyl and the herbicide imazamox. The reactors were filled with differing mixtures of vine-branch, citrus peel, urban waste and public green compost. The reactor volume was 188 1. Forced circulation of the contaminated solution was programmed to decontaminate the solution. Both retention and degradation of the compounds by the reactors was studied.Chlorpyrifos was the best retained, due to its physico-chemical characteristics, while only one substrate effectively retained metalaxyl and imazamox (citrus peel + urban waste compost). Degradation of the pesticides in the reactors was faster than published values for degradation in soil. The half-life of all pesticides in the reactors was less than 14 days, compared to literature values of 60-70 days in soil. The combined retention and fast degradation make the biofilter a feasible technique to reduce spill-related and point environmental contamination by pesticides. The technique is most effective against persistent pesticides, while for mobile pesticides, the efficiency can be improved with several passages of the contaminated solution through biofilters
Effect of rotation, nitrogen fertilization and management of crop residues on some chemical, microbiological and biochemical properties of soil
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