Incorporation of organic fertilizers/amendments has been, and continues to be, a popular strategy for golf course turfgrass management. Dissolved organic matter (DOM) derived from these organic materials may, however, facilitate organic chemical movement through soils. A batch equilibrium technique was used to evaluate the effects of organic fertilizer-derived DOM on sorption of three organic chemicals (2,4-D, naphthalene and chlorpyrifos) in USGA (United States Golf Association) sand, a mixed soil (70% USGA sand and 30% native soil) and a silt loam soil (Typic Fragiochrept). DOM was extracted from two commercial organic fertilizers. Column leaching experiments were also performed using USGA sand. Sorption experiments showed that sorption capacity was significantly reduced with increasing DOM concentration in solution for all three chemicals. Column experimental results were consistent with batch equilibrium data. These results suggest that organic fertilizer-derived DOM might lead to enhanced transport of applied chemicals in turf soils.
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"K F values for adsorption ranged from 5.32 to 15.78 for chlorpyrifos and from 3.93 to 6.54 for TCP. Similar observations have been reported in studies involving chlorpyrifos soprtion in soils (El-Nahhal, 2002; Li et al., 2005). The results showed that chlorpyrifos bound more strongly to soils than its metabolite TCP. "
[Show abstract][Hide abstract] ABSTRACT: The adsorption of chlorpyrifos and TCP (3,5,6, trichloro-2-pyridinol) was determined in four soils (Mollisol, Inceptisol, Entisol, Alfisol) having different specific surface areas (19–84 m2 g−1) but rather similar organic matter content (2.4–3.5%). Adsorption isotherms were derived from batch equilibration experiments at 25°C. After liquid-liquid extraction, the chlorpyrifos and TCP concentrations in the solution phase were determined by gas chromatography with an electron capture detector. Adsorption coefficients were calculated using the Freundlich adsorption equation. High KF coefficients for chlorpyrifos (15.78) and TCP (6.54) were determined for the Entisol soil, while low KF coefficients for chlorpyrifos (5.32) and TCP (3.93) were observed in the Alfisol soil. In all four soils, adsorption of chlorpyrifos was higher than that of TCP. A surface complexation model, the constant capacitance model, was well able to fit the adsorption isotherms of both chlorpyrifos and TCP on all four soils. The results showed that specific surface area affected adsorption of both chlorpyrifos and TCP. Among the soil properties, specific surface area could be a better indicator than organic matter content alone for adsorption of chlorpyrifos and TCP by soils that contained low organic matter.
Full-text · Article · Jan 2015 · Soil and Sediment Contamination
"This non-catalytic detoxification would help to overcome the potential side effects from other common remediation systems. For example, Li et al. (2005) showed that the addition of commercial organic amendments (32e35% organic carbon) to soil led to an increase of dissolved organic matter and, subsequently , a higher chlorpyrifos mobility. As current data show, the irreversible binding between CbE and chlorpyrifos-oxon would reduce its transport and toxicity, despite the inhibitoreenzyme complex might also be mobilized with the dissolved organic matter as well. "
[Show abstract][Hide abstract] ABSTRACT: Carboxylesterases (CbEs) are serine hydrolases involved in the detoxification of anticholinesterase (organophosphorus and methylcarbamate) pesticides. Past studies have documented the occurrence of these esterases in soil, but little is known about their origin, function, and particularly, their reactivity against agrochemicals. In this study, it was compared the potential CbE activity in earthworm-treated and control (earthworm-free) soils by enzyme kinetics with multiple carboxylic esters and native polyacrylamide gel electrophoresis. After 12 weeks of inoculation, CbE activity was between two- and four-fold higher in the earthworm-treated soils (α-naphthyl acetate = 4.85 ± 1.58 μmol h-1 g-1 dry soil, α-naphthyl butyrate = 2.93 ± 1.60, α-naphthyl valerate = 2.64 ± 1.27, 4-nitrophenyl acetate = 1.41 ± 0.37, 4-nitrophenyl butyrate = 0.87 ± 0.15 and 4-nitrophenyl valerate = 0.89 ± 0.11; values are presented as mean ± standard deviation) than in controls. Although this enhanced esterase activity remained unchanged for 1 month following earthworm removal, it decreased under soil desiccation (31% to 60%) or thermal denaturing (43% to 82%). The potential sources for enhanced soil CbE activity were also examined through plate-count of microorganisms and zymographic techniques. The earthworm gut microenvironment was a significant source of soil CbE activity, and the casts were found to be the main contributors to the esterase activity analyzed. Soil CbE activity was strongly inhibited by organophosphorus (chlorpyrifos-oxon, paraoxon-ethyl and paraoxon-methyl) and, at less extent, by methylcarbamates (carbaryl and carbofuran). In vitro inhibition kinetics showed a biphasic curve that revealed at least two sensitive esterases and a resistant fraction; the latter varied widely depending on the enzyme substrate (7 – 68 % of control activity). Likewise, spiking of earthworm-treated soils with 4 mg/kg (wet weight) of chlorpyrifos-oxon led to a significant inhibition of CbE activity 2 (40 – 72% inhibition) and 6 days (37 – 53%) after its application. Current results suggest that the soil-dwelling earthworm Lumbricus terrestris may be used as a promoter of soil enzyme activities with a direct benefit for pesticide bioremediation.
Full-text · Article · Aug 2014 · Soil Biology and Biochemistry
"Thus, compost is not only a good source of nutrients in soils , but also a significant source of DOM for a substantial period of time after its soil application . Since compost is known to bind pollutants, especially less polar ones, these cannot only be entrapped within the compost and reduce their bioavailability (Puglisi et al. 2007), but can be also mobilized through the soil profile together with the DOM released from compost after leaching events (Li et al. 2005). Further analyses by means of physicalchemical methods such as NMR spectroscopy, pyrolysis-GC-MS , and electrospray ionisation (ESI) LC-MS should be carried out in order to achieve a better characterization of DOM released by compost in time. "
[Show abstract][Hide abstract] ABSTRACT: The dissolved organic matter (DOM) released from compost by repeated water extractions was quantified and DOM conformational changes by high performance size-exclusion chromatography (HPSEC) were followed. Three commercial composts were extracted consecutively 4 times with equal water: compost ra- tios. The total organic carbon content of each DOM sample was analyzed using the chemical oxygen de- mand method, and the conformational size-distribution assessed by means of HPSEC. Results showed that compost continues to release considerable amounts of DOM with repeated water extractions, and that subsequent DOM extractions resulted in organic matter with increasing molecular dimensions and pre- sumably larger hydrophobicity. This may have important consequences on soil processes and functions such as organic matter dynamics and transport of pollutants.