Identification of trifluralin metabolites from rumen microbial cultures. Effect of trifluralin on bacteria and protozoa.
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Animals↗
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Environmental fate of trifluralin.
Trifluralin, a preemergence, soil-applied and soil-incorporated herbicide, has been in agricultural use since 1963. The environmental chemistry and fate of dinitroaniline herbicides, including trifluralin, has been studied extensively in agricultural soils. Probst et al. (1975) and Helling (1976) have summarized pre-1975 data on the mobility, persistence, and degradation or metabolism of dinitroaniline herbicides as a group. Since then, numerous studies have been carried out on the fate of dinitroanilines, especially trifluralin, in the environment to understand further their degradation in soil, potential for mobility and persistence, and environmental concentration in water and air. The present review, while summarizing briefly earlier data, concentrates primarily on the post-1975 data on degradation, mobility, and persistence of trifluralin in soils and its potential concentrations in water and air. Trifluralin is readily degraded under sunlight in all media, with half-lives (t1/2) of minutes to several months, depending on the substrate. In addition, other dissipation processes, such as microbial and chemical, are also operative in soils, water, and sediments. Several degradation products of trifluralin have been identified and characterized, both under photolysis and following aerobic and anaerobic metabolism in soils and water-sediment systems. The differences between various degradative pathways of trifluralin appear to be more quantitative than qualitative in nature, leading eventually to the same end products that are subject to binding or mineralization with time. The general lack of accumulation of the breakdown products of trifluralin suggests that these are also subject to the same degradative mechanisms as the parent compound. Trifluralin has low water solubility and is strongly bound to soil components; mean Koc values range from 4,000 to 13,000. Once applied and incorporated into the soil, trifluralin remains relatively immobile with minimal or no potential for contamination of groundwaters under or near the treated zones. Trifluralin residues in soil surface layers are subject to loss via transport in runoff water or volatilization into the air. Seasonal losses in surface runoff are consistently less than 0.5% of the amounts applied, with concentrations in edge-of-the-field run-off water typically < 1.0 microgram L-1. Consequently, trifluralin is infrequently detected in surface waters and, if present, usually occurs below levels of quantification. Seasonal trifluralin losses into the atmosphere can be as high as 25% of that applied. Maximum trifluralin residues in the air above treated fields are in the 2-3 micrograms m-3 range following application, decreasing to < 100 ng m-3 in ambient air of intensive use areas, indicating its rapid dissipation in air. Trifluralin residues at < 100 pg m-3 in the atmosphere of remote nonuse regions have been reported, suggesting its potential for long-range transport. However, there is a general lack of understanding of the mechanisms controlling its potential for long-distance transport, especially considering its rapid photodegradation in vapor and solution states. The persistence of trifluralin in agricultural soils following incorporation is highly variable, depending on several factors such as depth of incorporation, soil moisture, soil temperature, soil air, and soil organic matter content. Estimated half-lives under a variety of agronomic conditions range from 25 to > 201 d, thus categorizing its persistence from 'moderate' to 'persistent'. The estimated half-life data for trifluralin under agronomic conditions, however, cannot be extrapolated to other potential scenarios, such as its dissipation in nontarget areas where trifluralin residues, if any, are essentially deposited on surfaces. Surface deposits on nontarget areas, unlike soil-incorporated residues, would be subject to volatilization and photolysis and thus more short lived. (ABSTRACT TRUNCATED)
Canada↗
Treatment of experimental chronic chagas disease with trifluralin.
We tested trifluralin against Trypanosoma cruzi in a model of chronic Chagas disease in mice. CF1 mice (n=148) were intraperitoneally infected with 10(5) trypomastigotes of T. cruzi, H510C8C3 clone. One hundred mice were partially treated with benznidazole. Mortality was 100% at day 41 in the control group (n=48). At day 90 of the chronic disease (74% survival) mice were divided into three groups and treated orally with trifluralin (50 mg/kg/day, n=26), benznidazole (50 mg/kg/day, n=25) and vehicle (peanut oil; control group, n=23) for 60 days. Electrocardiography (under pentobarbital anaesthesia, 30 mg/kg/dose), serologic immunofluorescence and microstrout were performed at the beginning and at the end of the treatment. Mice were sacrificed at day 10 after treatment; cardiac tissue was studied histopathologically and polymerase chain reaction (PCR) was performed. Spontaneous mortality was 30.43%, 3.85% and 4% in the control, trifluralin and benznidazole groups, respectively (significant survival, P=0.03). Microstrouts were negative in all three groups. Negative immunofluorescence titers were 0%, 16% (P=0.05) and 29% (P<0.02) in the control, trifluralin and benznidazole groups, respectively. The prevailing electrocardiographic disorder was prolongation of the PR interval in the control group, which was not significantly altered in trifluralin- and benznidazole-treated mice, suggesting that trifluralin and benznidazole improve or even stop the damage caused by the disease on the conduction system. Trifluralin- and benznidazole-treated animals showed similar histologic patterns of myocarditis. PCR results were negative for benznidazole and trifluralin (100% and 70.8%, respectively). These results show the therapeutic potential of trifluralin in the treatment of chronic Chagas disease.
Animals↗
Comparison among soil Series and extraction methods for the analysis of trifluralin.
Accurate analytical procedures are needed to improve understanding of the fate and transport of trifluralin, a chemical widely used as a herbicide. Analytical determination of trifluralin is challenging due to its hydrophobic, yet volatile, character and its tendency to degrade into numerous metabolites. In this research, efficient analytical methods for fortified and field-incurred soils were developed for simultaneous quantitation of trifluralin, I [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine, CAS Registry No. 1582-09-8; CAS Registry No. have been provided by the author], a trifluralin metabolite, II [2,6-dinitro-N-propyl-4-(trifluoromethyl)benzenamine, CAS Registry No. 2077-99-8], and a related trifluoromethyldinitroaniline isomer of trifluralin, III [2,4-dinitro-N,N-dipropyl-6-(trifluoromethyl)benzenamine, CAS Registry No. 23106-20-9]. Extractions of trifluralin (0.5 and 2.5 microg/g) from silt loam, sandy loam, and silty clay soils were compared. A method was developed for the supercritical fluid extraction of trifluralin from soil using modified supercritical carbon dioxide, and the effects of cosolvent, pressure, and flow rate on recovery were evaluated. Supercritical fluid extraction was compared to liquid vortex extraction and automated Soxhlet (soxtec) extraction. Solid-phase extraction was examined for purifying soil extracts. Protocols were developed for analysis of extracts by gas and/or liquid chromatography. Immunoassay was investigated but proven to be impractical for this analysis. Soil properties and extraction methods were observed to affect the level of coextracted background interferences. Trifluralin exhibited concentration-dependent recovery regardless of soil series or extraction method.
Chromatography, Gas↗
Effects of trifluralin on soil microbial populations and the nitrogen fixation activities.
Effects of trifluralin on soil microbial populations and the nitrogen fixation activity of nitrogen-fixing bacteria Azotobacter chroococcum and Bradyrhizobium japonicum and the decomposition of trifluralin by soil microorganisms were studied. Trifluralin at lower concentrations from 0.5 mg microg(-1) dry soil to lower than 10.0 mg microg(-1) dry soil appeared to stimulate the growth of soil bacteria, actinomycetes, mould, and the pure cultures of Br. japonicum and A. chroococcum. Not only the colony amounts of these two species of nitrogen-fixing bacteria increased, grown on agar medium containing lower concentrations of trifluralin, but also these colonies also enlarged in size and appeared obviously in shorter formation time. However, trifluralin at higher concentrations would inhibit the development of microbial colonies both in amount and size. Trifluralin inhibited the activity of acetylene reduction of A. chroococcum when it was added at the same time of inoculation with A. chroococcum, but it showed a noteworthy stimulation to nitrogen fixation of A.chroococcum when it was put into culture after the cells of the nitrogen-fixing bacterium had grown well. The observation that soil microorganisms could use trifluralin as sole carbon and nitrogen resources for their growth, indicated that microorganisms could decompose trifluralin well.
Azotobacter↗
Protective effects of trifluralin on benzo(a)pyrene-induced tumors in A/J mice.
Trifluralin, a widely used herbicide, added to the diet before the p.o. administration of benzo(a)pyrene (BP) and fed continuously, significantly inhibited the induction of lung and forestomach tumors in female A/J mice. Dietary intake of trifluralin before the administration of BP resulted in a significant increase in glutathione in lung and forestomach but not in liver and glandular stomach. Trifluralin treatment also inhibited the binding of [3H]BP to liver and lung DNA, as well as to protein in the liver. Under these conditions, the protection against BP-induced lung tumors and perhaps forestomach tumors may be due to an elevation of tissue glutathione, resulting in a decreased binding of reactive metabolites of BP to macromolecules at these sites. The results indicate that trifluralin has a "blocking" effect in its inhibition of BP-induced tumors. Our studies show that trifluralin also inhibits chemical carcinogenesis in lung and forestomach when started in the diet 1 day after the administration of BP and fed continuously thereafter. In the case of lung, although maximum inhibition of tumors occurred when trifluralin was started 1 day after BP, there was significant protection at all time intervals (0 to 7 days) against lung tumors. The finding that trifluralin protects against BP tumorigenesis when started in the diet after the administration of the carcinogen clearly demonstrates that trifluralin also has a "suppressive" effect against BP-induced tumors.
Animals↗
Effects of the pesticides carbofuran, chlorpyrifos, dimethoate, lindane, triallate, trifluralin, 2,4-D, and pentachlorophenol on the metabolic endocrine and reproductive endocrine system in ewes.
Many pesticides are used in the agricultural environment, and some may have the potential to disrupt reproductive or endocrine function. Ewes, in separate groups of 6, received orally into their rumen either empty gelatin capsules or capsules containing chlorpyrifos (12.5 mg/kg), trifluralin (17.5 mg/kg), lindane (2.5 mg/kg), or pentachlorophenol (2 mg/kg) 2 times per week for 43 d. Dimethoate (0.2 mg/kg), carbofuran (0.30 mg/kg), 2,4-dichlorophenoxyacetic acid (10 mg/kg), or triallate (5 mg/kg) was given 3 times per week. After 36 d of treatment, blood samples were taken every 12 min for 6 h for hormone analysis. Ewes were euthanized at the end of the study for necropsy and histopathology. No overt signs of toxicity were seen, and body weight was not affected by treatment. Carbofuran caused a significant increase in serum concentrations of thyroxine compared to control ewes, but all other pesticides, except trifluralin, resulted in a marked decrease in thyroxine concentrations. Serum concentrations of cortisol were significantly increased by trifluralin and chlorpyrifos. Concentrations of insulin in serum were markedly increased in ewes given dimethoate, lindane, trifluralin, triallate, and pentachlorophenol, and concentrations of estradiol were also significantly increased in ewes given lindane and trifluralin. Mean serum concentrations of LH were markedly decreased by trifluralin, and basal LH concentrations were significantly decreased by lindane, dimethoate, and trifluralin but increased by triallate. Both pentachlorophenol and triallate caused a significant increase in severity of oviductal intraepithelial cysts in ewes. Data suggest that several currently used pesticides could influence serum concentrations of reproductive and metabolic hormones, particularly thyroxine, the major secretory product of the thyroid and a principal regulator of metabolism.
Agriculture↗
Uptake of trifluralin and lindane from water by ryegrass.
Understanding of the plant uptake of organic chemicals is essential to assessing contaminant mobility in the ecosystem, exposure to humans, and phytoremediation technologies. In this study, we measured the uptake of trifluralin and lindane from water by ryegrass as a function of uptake time for periods of 96 and 120 h, respectively. Trifluralin concentration in ryegrass increased sharply at the early stage of uptake and reached the maximum at 10 h, and then decreased with uptake time. 14C-labelled trifluralin uptake displayed a similar trend but a higher 14C-concentration than that of extracted parent compound, indicating metabolism and formation of bound residues following trifluralin uptake. Lindane concentration in ryegrass slowly increased with uptake time and approached a plateau, indicating minimal metabolism and formation of bound residues. The difference in the uptake characteristics of these two chemicals may be related to the differences in their lipophilicity, and chemical and biological reactivities. A two-compartment model accounting for the contributions of transpiration, metabolism and formation of bound residues to overall uptake was developed to assess the uptake kinetics. The model adequately described the uptake of trifluralin and lindane into ryegrass by providing the first-order rate constants of uptake, release, transpiration, and metabolism and formation of bound residues. These rate constants are used in calculating plant concentration factor (PCF). The ratios of trifluralin concentrations in ryegrass to its aqueous concentrations are between the PCF at thermodynamic equilibrium and the PCF at steady state, suggesting the utility of both PCF values.
Biological Availability↗
Leaching of trifluralin, metolachlor, and metribuzin in a clay loam soil of Louisiana.
Trifluralin[2,6-dinitro-N,N-dipropyl-4-(trifluormethyl)benzenamine], metolachlor[2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], and metribuzin[4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)one] were applied in field plots located on a Commerce clay loam soil near Baton Rouge, Louisiana at the rate of 1683 g/ha, 2759 g/ha and 609 g/ha, respectively. The half-lives of trifluralin, metolachlor, and metribuzin in the top 0-15 cm soil depth were found to be 54.7 days, 35.8 days and 29.8 days, respectively. The proportion of trifluralin, metolachlor, and metribuzin in the top 0-15 cm soil depth was 94.7%, 86.6%, and 75.4%, respectively of that found in the top 0-60 cm soil depth 30 days after application. Trifluralin concentrations were within a range of 0.026 ng/mL to 0.058 ng/mL in 1 m deep well water, and between 0.007 ng/mL and 0.039 ng/mL in 2 m deep well water over a 62 day period after application. Metolachlor concentrations in the 1 m and 2 m wells ranged from 3.62 ng/mL to 82.32 ng/mL and 8.44 ng/mL to 15.53 ng/mL, respectively. Whereas metribuzin concentrations in the 1 m and 2 m wells ranged from 0.70 ng/mL to 27.75 ng/mL and 1.71 ng/mL to 3.83 ng/mL, respectively. Accordingly, trifluralin was found to be strongly adsorbed on the soil and showed negligible leaching. Although metolachlor and metribuzin were also both readily adsorbed on the soil, their leaching potential was high. As a result, in the clay loam soil studied, metribuzin concentration in groundwater with shallow aquifers is likely to exceed the 10 mg/L US Environmental Protection Agency (EPA) advisory level for drinking water early in the application season, whereas trifluralin and metolachlor concentrations are expected to remain substantially lower than their respective 2 ng/mL and 175 ng/mL EPA advisory levels.
Acetamides↗
Simultaneous determination of linuron and trifluralin residues in carrots and their pulp by liquid chromatography and gas chromatography.
A simple method is described for determining trifluralin and linuron in carrots and their pulp. Samples are extracted with hexane-ethyl ether (1 + 1), cleaned up with a disposable Florisil cartridge, and eluted first with hexane-ethyl ether (99 + 1) (for trifluralin), and then with hexane-ethyl ether (3 + 7) (for linuron). Trifluralin is then analyzed by electron capture gas chromatography (GC/ECD), and linuron by GC/ECD and liquid chromatography with ultraviolet detection (LC/UV). Recoveries were determined by spiking untreated carrot and carrot pulp homogenates with trifluralin and linuron at 0.04, 0.16, and 0.32 micrograms/g. Six determinations were performed at each level for both compounds. GC/ECD average recoveries were 87.1% for trifluralin and 93.6% for linuron in carrots and 89.9% for trifluralin and 94.2% for linuron in carrot pulp. LC/UV recoveries for linuron were 91.5% for carrots and 92.8% for carrot pulp.
Chromatography, Gas↗
Genes similar to naphthalene dioxygenase genes in trifluralin-degrading bacteria.
Trifluralin (alpha,alpha,alpha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) is a dinitroaniline compound which was first produced in the 1960s and has been used extensively as an agricultural herbicide. There are a few publications on the biodegradation of this xenobiotic compound, but to our knowledge nothing has been documented on the genetic aspects of its catabolism. In this article, we report the analysis of DNA isolated from bacteria previously shown to degrade trifluralin, using as probes the catabolic genes ndoB, todC, xyIX, catA and xyIE which encode the enzymes naphthalene 1,2-dioxygenase, toluene dioxygenase, toluate 1,2-dioxygenase, catechol 1,2-dioxygenase and catechol 2,3-dioxygenase respectively. Using PCR and hybridization analysis, the strong hybridization of the ndoB gene with DNA extracted from four trifluralin-degrading isolates was demonstrated, although none of them was able to degrade naphthalene, as indicated by the 'clear zone' test. The results indicated the presence in these bacteria of a dioxygenase gene, whose product could act on trifluralin as its principal substrate, or fortuitously, by cometabolism. This is the first publication on genes in trifluralin-degrading bacteria.
Bacillus megaterium↗
Ozone treatment of soil contaminated with aniline and trifluralin.
Column studies were conducted to determine the ability of ozone to degrade aniline and trifluralin in soil. Ozone rapidly degraded aniline from soil under moist soil conditions, 5% (wt). Removal of 77-98% of [UL-14C]-aniline was observed from soil columns (15 ml, i.d. = 2.5 cm), exposed to 0.6% O(3) (wt) at 200 ml/min after 4 min. Initial ozonation products included nitrosobenzene and nitrobenzene, while further oxidation led to CO(2). Ring-labeled-[UL-14C]-trifluralin removal rates were slower, requiring 30 min to achieve removals of 70-97%. Oxidation and cleavage of the N-propyl groups of trifluralin was observed, affording 2,6-dinitro-4-(trifluoromethyl)-aniline, 2,6-dinitro-N-propyl-4-(trifluoromethyl)-benzamine, and 2,6-dinitro-N-propyl-N-acetonyl-4-(trifluoromethyl)-benzamine. Base solutions revealed that trifluralin was similarly oxidized to CO(2), where 72-83% of the activity recovered comprised 14CO(2). Use of ozone-rich water improved contaminant removal in trifluralin-amended soil columns, but did not improve removal in aniline, pentachloroaniline, hexachlorobenzene amended soil columns, suggesting that ozonated water may improve contaminant removal for reactive contaminants of low solubility.
Aniline Compounds↗
Using 19F NMR spectroscopy to determine trifluralin binding to soil.
Trifluralin is a widely used herbicide for the control of broad leaf weeds in a variety of crops. Its binding to soil may result in significant losses in herbicidal activity and a delayed pollution problem. To investigate the nature of soil-bound trifluralin residues, 14C-labeled herbicide was incubated for 7 weeks with four soils under anoxic conditions. As determined by radiocounting, trifluralin binding ranged between 10 and 53% of the initial 14C depending on the soil tested. 19F NMR analyses of the methanol extracts and different fractions of the extracted soil suggested that bound residue formation largely involved reduced metabolites of the herbicide. A 2,6-diamino product of trifluralin reduction with zero-valent iron (Fe-TR), and the standard of a 1,2-diaminotrifluralin derivative (TR6) formed covalent bonds with fulvic acid (FA), as indicated by the 19F NMR spectra taken periodically over a 3-week contact time. At short contact times, TR6 and Fe-TR formed weak physical bonds with FA, as the respective spin-lattice relaxation times (T1) decreased from the range 1300-1831 ms for TR6 or Fe-TR analyzed in the absence of FA to the range 150-410 ms for TR6/FA or Fe-TR/FA mixtures. In general, the results indicated that trifluralin immobilization involved a variety of mechanisms (covalent binding, adsorption, sequestration), and with time it became increasingly stable.
Adsorption↗
Kinetics and hydrolysis of fenamiphos, fipronil, and trifluralin in aqueous buffer solutions.
Hydrolyses of fenamiphos, fipronil, and trifluralin were studied in aqueous buffer solutions of pH 4.1, 7.1, and 9.1 at different temperatures, 5, 22 +/- 1, 32 +/- 1, and 50 +/- 1 degrees C. Fenamiphos, fipronil, and trifluralin were found to be more stable in acidic and neutral buffer solutions at temperatures of 5 and 22 +/- 1, and dissipation is rapid at 50 +/- 1 degrees C. In basic buffer and at higher temperature, degradation of fenamiphos was found to be very rapid when compared with fipronil and trifluralin. The rate constants calculated at 32 degrees C for fenamiphos were 2349.4 x 10(-)(8) (pH 4.1), 225.2 x 10(-)(8) (pH 7.1), and 30476.0 x 10(-)(8) (pH 9.1); for fipronil 1750.0 x 10(-)(8) (pH 4.1), 3103.0 x 10(-)(8) (pH 7.1), and 3883.0 x 10(-)(8) (pH 9.1); and for trifluralin 2331.0 x 10(-)(8) (pH 4.1), 2360.0 x 10(-)(8) (pH 7.1), and 3188.0 x 10(-)(8) (pH 9.1). On the basis of rate constant values, these pesticides appeared to be more susceptible to hydrolysis than synthetic organophosphorus compounds such as chlorpyriphos, diazinon, malathion, and ronnel. DT(50) values calculated at 32 degrees C were 228 (pH 4.1), 5310.24 (pH 7.1), and 37.68 (pH 9.1) h for fenamiphos; 608.6 (pH 4.1), 373.9 (pH 7.1), and 270.2 (pH 9.1) h for fipronil; and 502.1 (pH 4.1), 496.8 (pH 7.1), and 355.7 (pH 9.1) h for trifluralin.
Buffers↗
Herbicides to curb human parasitic infections: in vitro and in vivo effects of trifluralin on the trypanosomatid protozoans.
Leishmaniasis is a major tropical disease for which current chemotherapies, pentavalent antimonials, are inadequate and cause severe side effects. It has been reported that trifluralin, a microtubule-disrupting herbicide, is inhibitory to Leishmania amazonensis. In this study, the in vitro effect of trifluralin on different species of trypanosomatid protozoans was determined. In addition to L. amazonensis, trifluralin is effective against Leishmania major and Leishmania tropica, which cause cutaneous infections, Leishmania donovani, which causes visceral disease, Leishmania panamensis, which may cause mucocutaneous infection, and Trypanosoma brucei, an important human and veterinary pathogen. Moreover, most encouragingly, trifluralin is effective in vivo as a topical ointment against L. major and Leishmania mexicana murine cutaneous leishmaniasis. Thus, trifluralin is a promising lead drug for several related, prevalent tropical diseases: leishmaniasis, trypanosomiasis of animals, and, possibly, African trypanosomiasis in humans.
Animals↗
Adsorption and leaching of trifluralin, metolachlor, and metribuzin in a commerce soil.
Trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine], metolachlor [2-chloro-N-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) aceta mide], and metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4,-triazin-5(4H) -one] were selected to study adsorption and leaching potentials related to pollution on Commerce silty clay loam soil near Baton Rouge, Louisiana. At a I:10 soil/water ratio, the Koc values for trifluralin, metolachlor and metribuzin were 875, 135, and 96, respectively. Leaching of these herbicides was evaluated in soil columns (5.4 cm i.d. x 26 cm long). Total recoveries of the herbicides applied to the soil column were 73.1% +/- 4.1%. When the soil columns were leached with three pore volumes of water, the distributions of trifluralin in soil and leachate were 99.993% and 0.007% of the total recoveries, respectively. The distributions of metolachlor was 65.27% in soil and 34.7% in leachate. The distributions of metribuzin was 11.42% in soil and 88.58% in leachate. The results showed that metolachlor and metribuzin were readily leached, while trifluralin was strongly adsorbed to soil. Leaching of three herbicides in the soil column followed the leaching trends of their calculated leaching indices 1.41 x 10(4), 4.18 x 10(6), and 3.38 x 10(8) for trifluralin, metolachlor, and metribuzin, respectively. The results of the study demonstrated the potential of pollution for metolachlor and metribuzin to be leached into the ground water in soils with shallow aquifer.
Acetamides↗
Runoff of trifluralin, metolachlor, and metribuzin from a clay loam soil of Louisiana.
Trifluralin[2,6-dinitro-N,N-dipropyl-4-(trifluormethyl)benzenamine], metolachlor[2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] and metribuzin[4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)one] were applied as pre-emergent herbicides to soybean plots in Louisiana (LA) at the rate of 1683 g/ha, 2759 g/ha and 609 g/ha, respectively. The concentrations of trifluralin in the runoff water ranged between 0.09 ng/mL and 0.02 ng/mL, which is lower than the 2 ng/mL US Environmental Protection Agency (EPA) advisory level for trifuralin in drinking water. Metolachlor concentrations in the runoff water ranged from 9.0 ng/mL to 221.5 ng/mL, which is both lower and higher than the 175 ng/mL EPA advisory level for metolachlor. Similarly, metribuzin concentrations in the runoff water ranged between 1.5 ng/mL and 56.2 ng/mL, which is also lower and higher than the 10 ng/mL EPA advisory level for metribuzin. Accordingly, from the field plots located on a Commerce clay loam soil in LA, although the concentration of trifluralin in runoff water were substantially lower than the EPA advisory level, metolachlor and metribuzin concentrations are likely to exceed the EPA advisory levels early on in the application season with a subsequent rapid decrease to safe levels. The total loss of trifluralin in runoff water was 0.005% of the applied amount over an 89 day period after application. The total loss of metolachlor and metribuzin in the runoff water was 4.67% and 5.36% of the applied amount, respectively, over a 22 day period after application. As such, there was almost no movement of trifluralin in the runoff water, whereas metolachlor and metribuzin were much more easily moved.
Acetamides↗
Effect of manure on glyphosate and trifluralin mineralization in soil.
Manure additions to soil may alter soil chemical, physical, and biological characteristics, and thereby change pesticide fate processes in soil. This is the first study to examine the impact of liquid hog manure amendments on glyphosate and trifluralin mineralization in soil. Experiments were conducted in soil microcosms in the laboratory for a total of 332 (glyphosate) and 430 (trifluralin) days. The rate and amount of mineralization of both glyphosate and trifluralin were significantly influenced by the additions of fresh manure to soil in the laboratory and by the history of manure applications in the field. However, the maximum difference in herbicide mineralization between soils that were free of manure application and those amended with manure in the field or in the laboratory was only 6.1% and 7.3% of that initially applied, for trifluralin and glyphosate, respectively. Therefore, we conclude that liquid hog manure application to soil will have no significant effect on the mineralization of glyphosate and trifluralin under field conditions.
Animals↗