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
"Dissolved organic carbon (DOC) plays a great role in terrestrial and aquatic ecosystems (Jones et al. 2004; Monaghan et al. 2007; Haaland and Mulder 2010). DOC may enhance the sorption and mobility of pesticides and heavy metal in surface waters and leads to drinking water quality problems (David et al. 1991; Li and Shuman 1997; Li et al. 2005). Loss of DOC from agricultural soil occurs at the expense of both soil organic carbon and water quality. "
[Show abstract][Hide abstract]ABSTRACT: Runoff is a major driver for dissolved organic carbon (DOC) diffusing into aquatic ecosystems. Transport of DOC in runoff is important in the C cycle of soils in an agricultural ecosystem. This study provides a combined dataset on DOC loss pathways and fluxes from sloping upland in the purple soil area of southwestern China. A free-drain lysimeter experiment was conducted to quantify DOC loss through overland flow (2010–2012), interflow (2010–2012) and sediment (2011–2012). Average annual cumulative discharges of overland and interflow were 58.3 ± 3.1 and 289.4 ± 5.4 mm, accounting for 6.8 and 33.8 % of the totals during the entire rainy season, respectively. Average annual cumulative sediment loss flux was 183.5 ± 14.6 g m−2. Average DOC concentrations in overland flow and interflow were 3.44 ± 0.36 and 3.04 ± 0.24 mg L−1, respectively. Average DOC content in sediment was 73.76 ± 4.09 mg kg−1. The relationship between DOC concentration and discharge in overland flow events could be described by a significant exponential decaying function (R = 0.53, P = 0.027). Average annual DOC loss fluxes through overland flow, interflow and sediment were 163.6 ± 28.5, 865.5 ± 82.5 and 9.4 ± 1.5 mg m−2, respectively, and total DOC loss was 1,038.5 ± 112.5 mg m−2. The results suggest that interflow is the major driver of DOC leaching loss on sloping upland. It is shown that interflow is fundamentally important for reducing DOC loss on sloping croplands in the Sichuan Basin and possibly beyond.
Full-text · Article · Mar 2014 · Nutrient Cycling in Agroecosystems