Degradation Of Trifluralin Research Articles

Biodegradation of Trifluralin in Harran Soil

Degradation of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) was investigated in soils taken from three different locations at Harran region of Turkey under laboratory conditions. Surface (0–10 cm) soils, which were taken from a pesticide untreated field Gürgelen, Harran-1 and Ikizce regions in the Harran Plain, were incubated in biometer flasks for 350 days at 25°C. Ring-UL-14C-trifluralin was applied at the rate of 2 µg g−1 with 78.7 kBq radioactivity per 100 g soil flask. Evolved 14CO2 was monitored in KOH traps throughout the experiment. Periodically, soil sub-samples were removed and extracted by supercritical fluid extraction (SFE). Unextractable soil-bound 14C residues were determined by combustion. During the 350 days incubation period 6.6, 5.4, and 3.3% of the applied radiocarbon was evolved as 14CO2 from the Harran-1, Gürgelen, and Ikizce soil, respectively. At the end of 350 days the SFE-extractable and bound 14C-trifluralin residues were 39.0 and 29.2% of the initially applied herbicide in Gürgelen soil. The corresponding values for Harran-1 and Ikizce soils were 36.2, 28.4% and 41.6, 18.5% respectively.

Abiotic reduction of dinitroaniline herbicides

The importance of abiotic reductive transformations as a sink for four dinitroaniline herbicides (trifluralin, pendimethalin, nitralin, and isopropalin) has been evaluated. Using reductants representative of abiotic reductants found in natural systems, the results of this study indicate that nitro groups present on the dinitroaniline herbicides can be reduced by surface-bound Fe(II) species in goethite suspensions or by hydroquinone moieties such as (mercapto)juglone in a hydrogen sulfide solution. Aqueous iron species are also effective at pH values above 7.0. The reaction in aqueous Fe(II) and in Fe(II)/goethite systems is strongly pH dependent, with rates increasing with increasing pH. Montmorillonite clay, however, is not effective in mediating the reduction of dinitroaniline herbicides in the presence of Fe(II). Because the selected dinitroaniline herbicides have a mixture of electron withdrawing and electron donating groups, linear free energy relationships were developed for the H 2S/(mercapto)juglone and Fe(II)/goethite systems. Anilines resulting from reduction of the nitro group as well as cyclization products (benzimidazoles) were observed in the degradation of trifluralin. Only one aniline product was observed for pendimethalin.

Abiotic Degradation of Trifluralin by Fe(II): Kinetics and Transformation Pathways

The herbicide trifluralin (2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine) is widely used in agriculture and may pose toxic risks to some aquatic organisms. While its degradation has been investigated in field studies, this research is the first to elucidate the specific abiotic transformations that trifluralin may undergo in reducing environments such as flooded soils and wetland sediments. Kinetic data and product identities were determined for the degradation of trifluralin in Fe(II)/goethite suspensions at near-neutral pH values. Under these conditions, trifluralin is consumed rapidly through a surface-mediated process that includes three distinct reactions: reduction of nitro groups, dealkylation of propylamines, and cyclization to form benzimidazoles. All detected products are among those that have been reported in natural soils and sediments. Therefore, these transformation pathways may play a significant role in affecting the fate of trifluralin in the environment.

Fitotoxic effects of trifluralin to hybrid maize (zea mays l) and their persistance

The objective of the study was to analyze the susceptibility of three different types of hybrid maize to carryover potential of trifluralin using the bioassay, and persistence of trifluralin. Herbicide toxicity was analyzed by determining the inhibition of root and shoot length and fresh weight. In addition, using the bioassay trifluralin persistence in the leached chernozen soil type was studied applying two doses. Herbicide degradation was monitored over a period of one year following application during the two trial years. The hybrids tested showed a significant susceptibility to herbicide tested. The doses analyzed inhibited root length and fresh weight. Regression analysis was used to determine I50 values for the parameters tested thus proving fresh root weight reduction to be the most susceptible and accurately computed parameter. Hybrid ZPSC 633 was the most susceptible (with regard to the parameters tested). Higher herbicide doses provoked slower degradation of trifluralin, as confirmed by calculated DT-50 values. Trifluralin residues (applied at the rate of 960 g a.i.7ha) provoked no damage to ground parts. Root length and fresh weight inhibition was about 10% in the case of the most susceptible hybrid. However trifluralin (applied at the rate of 1920 g a.i./ha) residues one year following application provoked damage to ground parts (up to 20% in the case of the most susceptible hybrid), whereas root length and fresh weight inhibition was approx. 30%.

Organic amendments to enhance herbicide biodegradation in contaminated soils

Pesticide contamination of soil and groundwater at agricultural chemical distribution sites is a widespread problem in the USA. Alternatives to land-farming or solid waste disposal include biostimulation and phytoremediation. This research investigated the ability of compost, corn stalks, corn fermentation byproduct, peat, manure, and sawdust at rates of 0.5% and 5% (w/w) to stimulate biodegradation of atrazine [6-chloro-N-ethyl-N′-(1-methyethyl)-1,3,5-triazine-2,4-diamine], metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], and trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] added as a mixture to soil. Initial concentrations were 175±42 mg atrazine kg–1 soil, 182±25 mg metolachlor kg–1 soil, and 165±23 mg trifluralin kg–1 soil. After amendment addition, 30% of the atrazine, 33% of the metolachlor, and 44% of the trifluralin was degraded over 245 days, which included 63 days' aging prior to amendment additions. Atrazine degradation was enhanced by 0.5% manure, 5% peat, and 5% cornstalk amendments compared to nonamended soils. Metolachlor degradation was enhanced by all amendments at the 5% level, except for compost and peat. Amendments had no effect on trifluralin degradation. The 5% addition of compost, manure, and cornstalks resulted in significant increases in bacterial populations and dehydrogenase activity. A second experiment compared the persistence of atrazine, metolachlor, and trifluralin applied in a mixture to their persistence in soil individually. A combined average of 123 mg atrazine kg–1 remained in soil treated with the three-herbicide mixture compared to 31 mg atrazine kg–1 remaining in soil treated with atrazine only. Atrazine mineralization and atrazine-degrading microorganisms were suppressed by high concentrations of metolachlor, but not by trifluralin.

ANODIC FENTON TREATMENT OF TREFLAN MTF®

Anodic Fenton Treatment (AFT) is a radical oxidation treatment process which generates highly reactive hydroxyl radicals via the Fenton reaction. The degradation of trifluralin, a widely used hydrophobic yet volatile dinitroaniline herbicide, was studied during AFT. Three different concentrations of trifluralin, as the emulsifiable concentrate Treflan MTF®, were treated at three different concentrations and Fe2+:H2O2 delivery ratios. Each treatment, done in triplicate, involved electrochemical Fe2+ delivery from a sacrificial anode and H2O2 delivery via a peristaltic pump. Optimal treatment conditions of Fe2+:H2O2 delivery for the AFT of Treflan MTF® were determined. Data were pooled for multiple regression analyses to determine whether first, second or third order models for degradation of trifluralin and formulation ingredients were appropriate. Trifluralin degraded partially and slowly with an optimal Fe2+:H2O2 delivery of 1:1 for 100 μM and 40 μM trifluralin solutions and 1:10 for 15 μM solutions. The trifluralin degradation data did not fit the regression models. However, the main formulation ingredient, compound X, degraded completely and rapidly with an optimal Fe2+:H2O2 delivery of 1:5 and with a first order rate of degradation.

Trifluralin Degradation under Microbiologically Induced Nitrate and Fe(III) Reducing Conditions

Trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] ranks among the most commonly used herbicides in the United States. The compound persists under most environmental conditions, yet it is rapidly transformed under certain anaerobic conditions. In this study, the fate of trifluralin in anoxic environments and the contribution of Fe(II) to its anaerobic degradation have been investigated. Trifluralin was rapidly degraded under anaerobic conditions in a range of soils representing typical agricultural usage in the Midwest. The presence of nitrate or oxygen suppressed trifluralin degradation. Degradation rate increased under iron-reducing conditions, and the addition of trifluralin appeared to promote reoxidation of extractable Fe2+. Transformation of trifluralin under iron-reducing conditions apparently involved the soil solid phase and was not limited by bioavailability. In a soil-free aqueous system, no reaction of trifluralin with dissolved Fe2+ was detected in the presence or absence of kaolinite clay under anoxic conditions. Reduced but not oxidized or reoxidized forms of purified ferruginous smectite (sample Swa-1) catalyzed rapid transformation (72% of applied in 30 h) of trifluralin to polar products with a concomitant reoxidation of structural Fe in the clay. Results indicate that, as for other nitroaromatics, trifluralin is subject to reaction with Fe(II) associated with the minerals in anoxic environments.

Degradation of trifluralin in three Victorian soils —long-term field trials

Summary. The persistence of trifluralin was investigated at 3 sites in southern Australia over 8 years. Persistence varied from year-to-year, with the highest persistence being recorded at all sites in the dry year of 1984. Trifluralin persistence (expressed as a percentage of the initial measured concentration) 1 year after application was lowest at Rutherglen (7–22%), followed by Dooen (7–26%) and Walpeup (13–120%). Trifluralin degradation at Walpeup in 1984 was negligible. The resultant high residue concentrations would have posed a threat to subsequent crops. However, 1 year later after the subsequent fallow, the residue concentration had dropped to more typical levels. Trifluralin did not accumulate after repeated application (either 1 or 2 years apart) at all 3 sites. It was found important to measure the amount of trifluralin in the soil immediately after application because the trifluralin concentration could not be assumed from the rate. Soil concentrations immediately after application ranged from 32 to 138% of that expected from the nominal application rate. Therefore, measuring initial concentrations when comparisons were to be made between treatments, years and sites, was essential. In addition to studies of 1 year persistence, trifluralin concentration was also measured 2 years after application at Walpeup and Dooen. There was evidence to suggest that the rate of degradation over the same 1 year period, was different for a recent application when compared with weathered trifluralin residues from a previous application. Correlations between persistence and various weather factors indicated that the most influential factors were those that occurred in the first 60 days after application. These included total rainfall, effective rainfall (rainfall minus evaporation) and average maximum temperature.

Degradation of trifluralin in three Victorian soils under field and laboratory conditions

The effects of soil moisture and temperature on trifluralin degradation were investigated in 3 Australian soils under field and laboratory conditions. For the field trials, the amount of trifluralin persisting over 1 year into the next cropping season varied from 9 to 24%. From laboratory experiments, separate relationships were derived for the effects of temperature and moisture 1 on trifluralin degradation. Trifluralin degradation I increased with both increasing moisture and increasing temperature. The results indicate potential for unusually long persistence of trifluralin in years of low rainfall when the soil becomes very dry. It is therefore recommended that analysis for trifluralin residues or activity be undertaken if a sensitive crop such as oat, sorghum, or millet, or a sensitive pasture species such as phalaris or ryegrass, is sown after very dry climatic conditions following trifluralin application. The wheatbelt regions of Australia do not experience cold conditions for long enough periods for low temperatures to be a major factor contributing to trifluralin persistence. Degradation was compared for trifluralin applied as a formulation of the herbicide and as the active ingredient alone, to determine the validity of results obtained using the pure herbicide. In half of the 6 field and laboratory studies, there was a statistically significant difference between degradation of trifluralin as the active ingredient and as the formulation. This indicates a need to use the formulated compound in laboratory experiments if results are to reflect normal agricultural practices.

Degradation of Trifluralin by Bacteria Isolated from Soil.

Degradation of Trifluralin by Bacteria Isolated from Soil.

Treatment of Four Biorefractory Contaminants in Soils Using Catalyzed Hydrogen Peroxide

AbstractThe treatment of soil contaminated with pentachlorophenol, trifluralin [2,6‐dinitro‐N, N‐dipropyl‐4‐(trifluoromethyl) benzenamine], hexadecane, and dieldrin (3,4,5,6,9,9‐hexachloro‐1a,2,2a,3,6,6a,7,7a‐octahydro‐2,7:3,6‐dimethanonaphth[2,3‐b]oxirene) using catalyzed hydrogen peroxide [H202 and iron(II)] was investigated in a soil of low development with organic C ranging from 2000 mg kg–1 to 16 000 mg kg–1. Soil treatment was conducted at pH 3 with 240 and 400 mg L–1 iron additions and 120 000 mg L–1 H2O2. Pentachlorophenol and trifluralin degradation rates decreased as a function of soil organic C content. However, soil organic C had no effect on the degradation rates of dieldrin and hexadecane. In addition, the four contaminants degraded at equal rates with soil containing organic C > 10 000 mg kg–1. The ratio of first‐order rate constants for contaminant degradation to hydrogen peroxide consumption (kcontaminant/kh2O2) was used as an empirical measure of treatment efficiency. These ratios were sensitive to both the soil organic C content and to the concentration of iron added during treatment. The efficiency ratios were highest for treatment with no iron addition; these data suggest that iron minerals and H2O2 provide a system in which Fenton‐like oxidations are catalyzed. The ability of iron minerals and H2O2 to oxidize pentachlorophenol was evaluated in goethite‐, hematite‐, and magnetite‐silica sand at pH 3. Pentachlorophenol was degraded in the mineral‐silica sand systems, which was verified by the loss of organic C and the stoichiometric recovery of chloride.

Mathematical Description of Trifluralin Degradation in Soil

Degradation of trifluralin in four soils, each represented at four sites, under field conditions was determined quantitatively and described mathematically. A biexponential equation that resulted from integration of first-order and second-order differential rate equations described degradation data better than the first-order kinetic model for 15 of 25 soil-site combinations. Biexponential model regression coefficients indicated extent of degradation and that degradation is rapid at initially high trifluralin concentrations but slows as concentration decreases. The first-order kinetic model initially underestimated but ultimately overestimated degradation of trifluralin, thereby inferring that a first-order half-life is inadequate for predicting trifluralin persistence.

Degradation of Trifluralin in Seawater When Used to Control Larval Mycosis in Penaeid Shrimp Culture

AbstractTreflan (trifluralin, Elanco) is among the compounds used in the treatment of larval mycosis in penaeid shrimp caused by the phycomycetous fungi hagenidium sp. and Sirolpidium sp. Some culturists have reported treatments for these fungi with trifluralin to be ineffective while others have found it to be quite efficacious.To study losses of trifluralin in seawater systems, experiments were conducted under varying conditions of aeration, lighting, and algal biomass using nominal concentrations of 19.3 to 65.5 ppb trifluralin. There was no detectable loss of trifluralin over a six hour period in seawater mechanically stirred and covered to prevent photodegradation. Under varying conditions of aeration and light, the estimated half‐life of trifluralin ranged from 30 to 138 min. When diatoms were added to the seawater, trifluralin levels dropped to 4% of theoretical within two to three min. These observations confirm the need for a continuous administration for trifluralin to be effective in treating larval mycoses in penaeid shrimp hatching facilities.

Microbial degradation of trifluralin by Aspergillus carneus, Fusarium oxysporum and Trichoderma viride.

3H-Trifluralin was synthesized by condensation of 3H-4-chloro-3,5-dinitro-alpha, alpha, alpha-trifluorotoluene with di-n-propylamine. After incubation of trifluralin with Aspergillus carneus, Fusarium oxysporum and Trichoderma viride for 10 days, a small percentage (less than 10%) of unchanged herbicide was recovered in the extractable fraction. This indicates a fairly rapid degradation of the herbicide by the fungal species. Other than trifluralin, the culture medium contained at least five labelled products: 2,6-dinitro-N-n-propyl-alpha, alpha, alpha-trifluoro-p-toluidine; 2,6-dinitro-alpha, alpha, alpha-trifluoro-p-toluidine; 2-amino-6-nitro-alpha, alpha, alpha-trifluoro-p-toluidine, 2,6-dinitro-4-trifluoromethyl phenol and a major polar product which constituted more than 50% of the total extractable transformation products. A pathway, which simulates that of aerobic degradation of the herbicide in soil, is suggested for the microbiological degradation of trifluralin.

Trifluralin degradation and binding in soil

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Soil degradation of trifluralin: Mass spectrometry of products and potential products

The examination of soil which has been treated with trifluralin (TREFLAN alpha,alpha,alha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) has resulted in the identification of 28 degradation products. This paper presents the mass spectra of these products and a number of related compounds which were suspected products but were not found in trifluralin-treated soil. The mass spectra of the N,N-dialkylamines, with one exception, show major peaks due to amine alpha-cleavage and due to amine alpha-cleavage followed by carbon-nitrogen bond fission with rearragement of a hydrogen atom. Compounds having nitro groups yield mass spectra containing peaks due to intra-ionic oxidation by the nitro groups. In some cases, propionyl ions formed by this process are major ions in the spectra. Azo and azoxybenzenes resulting from condensation of two trifluraline moieties through nitro-nitrogens fragment mainly through the nitrogen-nitrogen bond.

FIELD PERSISTENCE AND MOVEMENT OF TRIFLURALIN IN TWO SOIL TYPES

Trifluralin (α, α, α-trifluoro-2, 4, dinitro-N, N-dipropyl-p-toluidine) was applied in 1973 to Egam loam and Beason clay field plots, which differed in slope and texture of the surface 12 in. of soil. Recommended (1×) and excessive (1.5× and 2×) rates of trifluralin were applied, and the herbicide was incorporated to a depth of 4 in. Movement of trifluralin below the 8-in. depth was essentially nil in both soils, but considerable movement occurred to the 8-in. depth in both. Trifluralin longevity in each soil was essentially the same, although higher rates were applied in the clay soil. On the average, less than 1% of the herbicide remained 5 months after application; an increasing trend of trifluralin residues with 1.5× and 2× rates was discerned, however. No herbicide was found in the soil the following spring (11 months after application). There was some evidence of upward movement of trifluralin in both soils. Trifluralin degradation followed first-order kinetics with half-life values of 35.8 and 25.7 days for Egam and Beason soils, respectively. Five weeks after herbicide application, control of two broad-leaf weeds and one grass weed was poor, being consistent with low herbicide concentrations (0.06 ppm) remaining in the soil at that time. The growth of oats (Avena sativa L.), a species sensitive to trifluralin, was also not significantly affected in the greenhouse at 0.05 ppm of trifluralin concentration.

Degradation of Trifluralin in Soil Suspensions as Related to Redox Potential

AbstractA system for controlling redox potential in soil suspensions was used to investigate the relationship between oxidation‐reduction potential (Eh) and the rate of trifluralin (a‐a‐a‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) degradation. Redox potentials of +450, +250, +150, +50, 0, and −50 mV were imposed on trifluralinamended (1 ppm oven‐dry weight soil basis) soil suspensions (100 g soil in 300 ml H2O) for 21 days. Results indicated that exclusion of O2 by soil flooding initiated rapid trifluralin degradation only when the Eh decreased below a critical range between +150 and +50 mV. There was no clear‐cut relationship between trifluralin degradation and microbiological respiratory activity (CO2 evolution).If soil flooding is to be a practical cultural technique for accelerating the rate of degradation of persistent pesticides, steps may have to be taken to ensure that soil Eh decreases below a critical value for some required period of time. This may include soil incorporation of a readily available carbon or energy source to stimulate an active soil microbial population to enhance lowering of the soil Eh.