Herbicides alachlor

Cowell J.E., Danhaus, R.G., Kunstman, J.L., Hackett, A.G., Oppenhuizen, M.E., and Steimetz, J.R. (1987) Operator exposure from closed system loading and application of alachlor herbicide, Arch. Environ. Contam. Toxicol., 16 327-332. 

Verro et al. [53] evaluated the risk associated with the presence of alachlor herbicide in surface waters (released by drift and runoff) from Lombardia region (Northern Italy). They applied a GIS-based model for representing the obtained PECs in risk maps showing a static image of a worst-case simulation in each river subbasin. 

Several encapsulated herbicide formulations exist. Encapsulated alachlor herbicide has been sold as a liquid or dry granule formulation. The capsules, produced by interfacial polymerization, are spherical with a diameter of 2-15 /um. Two thiocarbamate herbicides, EPTC and vemolate [1929-77-7], were encapsulated by interfacial polymerization because they are volatile compounds. When applied in imencapsulated form, they must be incorporated in the soil within 2 h in order to provide effective weed control. When applied as a microencapsulated formulation, the rate of volatilization is lower and soil incorporation can be... 

Much of the chloroacetyl chloride produced is used captively as a reactive intermediate. It is useful in many acylation reactions and in the production of adrenalin [51-43-4] diazepam [439-15-5] chloroacetophenone [532-27-4] chloroacetate esters, and chloroacetic anhydride [541-88-8]. A major use is in the production of chloroacetamide herbicides (3) such as alachlor [15972-60-8]. 

Acid amide herbicides are nonionic and moderately retained by soils. The sorption of several acid amide herbicides has been investigated (369). Acetochlor [34256-82-1] is sorbed more than either alachlor or metolachlor, which are similarly sorbed by a variety of soils. Sorption of all the herbicides is well correlated to soil organic matter content. In a field lysimeter study, metolachlor has been found to be more mobile and persistent than alachlor (370) diphenamid [957-51-7] and napropamide [15299-99-2] have been found to be more readily leached (356). 

Chlorine adds to ketene to form chloroacetyl chloride [79-04-9] (78). Chloroacetyl chloride (CAC) is used in large volume in the manufacture of the pre-emergence herbicides alachlor [15972-60-8] and butachlor [23184-66-9]. It is estimated that the CAC requirement for this appHcation was in excess of 45,000 metric tons in 1992. Significant volumes of CAC are also used in pharmaceutical manufacture, such as anesthetics of the Hdocaine type, and in the production of the tear gas chloroacetophenone [532-27-4]. Other commercial methods for the manufacture of CAC have been described (79). 

Alachlor zero 0.002 Eye, liver, kidney or spleen problems anemia increased risk of cancer Runoff from herbicide used on row crops... 

Resistance of house flies (Musca domestica) to DDT was attributed to its transformation to the nontoxic DDE, and the enzyme that carries the dehydrochlorination has been characterized in DDT-resistant flies (Lipke and Kearns 1959a,b). The herbicide alachlor is transformed by chironomid larvae by O-demethylation followed by loss of the chloroacetyl group to produce 2,6-diethylaniline... 

Chloroacetanilides are soil-applied herbicides used for pre- and early post-emergence control of annual grasses and broadleaf weeds in crops. Representative chloroacetanilide compounds, alachlor, acetochlor, and metolachlor, are extensively used worldwide. Other chloroacetanilides with limited usages include propachlor, bu-tachlor, metazachlor, pretilachlor, and thenylchlor. Public environmental concerns and government regulatory requirements continue to prompt the need for reliable methods to determine residues of these herbicides. There now exist a variety of analytical methods to determine residues of these compounds in crops, animal products, soil, and water. The chemical structures and major crops in which these compounds are used are summarized in Table 1. 

The current methodology to determine residues of alachlor, acetochlor, propachlor, and butachlor in crops and animal products was developed over the last two decades by researchers at the Monsanto Company. These herbicides degrade rapidly in plants and animals to numerous metabolites that can be hydrolyzed to common aniline moieties. Little to no parent herbicide is found as intact residue in crops and animal products therefore, the residue methodology focuses on the determination of the common moieties that are derived from the parent herbicides and their metabolites. Initially, gas chromatography (GC) with flame ionization detection, nitrogen-phosphorus... 

The complexity of the metabolism of alachlor, acetochlor, butachlor, and propachlor has led to the development of degradation methods capable of hydrolyzing the crop and animal product residues to readily quantitated degradation products. Alachlor and acetochlor metabolites can be hydrolyzed to two major classes of hydrolysis products, one which contains aniline with unsubstituted alkyl groups at the 2- and 6-positions, and the other which contains aniline with hydroxylation in the ring-attached ethyl group. For alachlor and acetochlor, the nonhydroxylated metabolites are hydrolyzed in base to 2,6-diethylaniline (DBA) and 2-ethyl-6-methylaniline (EMA), respectively, and hy-droxylated metabolites are hydrolyzed in base to 2-ethyl-6-(l-hydroxyethyl)aniline (HEEA) and 2-(l-hydroxyethyl)-6-methylaniline (HEMA), respectively. Butachlor is metabolized primarily to nonhydroxylated metabolites, which are hydrolyzed to DEA. Propachlor metabolites are hydrolyzed mainly to A-isopropylaniline (NIPA). The base hydrolysis products for each parent herbicide are shown in Eigure 1. Limited interference studies have been conducted with other herbicides such as metolachlor to confirm that its residues are not hydrolyzed to the EMA under the conditions used to determine acetochlor residues. Nonhydroxylated metabolites of alachlor and butachlor are both hydrolyzed to the same aniline, DEA, but these herbicides are not used on the same crops. 

The method using GC/MS with selected ion monitoring (SIM) in the electron ionization (El) mode can determine concentrations of alachlor, acetochlor, and metolachlor and other major corn herbicides in raw and finished surface water and groundwater samples. This GC/MS method eliminates interferences and provides similar sensitivity and superior specificity compared with conventional methods such as GC/ECD or GC/NPD, eliminating the need for a confirmatory method by collection of data on numerous ions simultaneously. If there are interferences with the quantitation ion, a confirmation ion is substituted for quantitation purposes. Deuterated analogs of each analyte may be used as internal standards, which compensate for matrix effects and allow for the correction of losses that occur during the analytical procedure. A known amount of the deuterium-labeled compound, which is an ideal internal standard because its chemical and physical properties are essentially identical with those of the unlabeled compound, is carried through the analytical procedure. SPE is required to concentrate the water samples before analysis to determine concentrations reliably at or below 0.05 qg (ppb) and to recover/extract the various analytes from the water samples into a suitable solvent for GC analysis. 

Limits of detection for each of the three parent herbicides in surface and groundwater were determined using results obtained from control samples analyzed along with hundreds of surface and ground water sets during the years 1995-2001. In each of these years, the calculated LODs (minimum detectable true concentrations/detection) were below 0.03 pg for acetochlor and metolachlor and 0.05 pg for alachlor. A detection criterion is a measured concentration threshold that defines a likely upper bound for samples not containing the analyte. If the actual concentration of an analyte is at this detection limit or greater, there is at least a 95% chance of detection. 

LOQs for each of the three parent herbicides in surface water were determined using all the analytical results (not corrected for background) of samples fortified at the lowest fortification level, 0.05 pgL , during the analysis in years 1995-2001. The calculated LOQs were below 0.05 pgL for acetochlor and metolachlor and approximately 0.05 pgL for alachlor. If the true concentration of an analyte is at the LOQ or greater, the standard error of individual measured concentration values relative to the true concentration is at most 10%. 

J.A. Shoemaker, Analytical method development for alachlor ESA and other acetanilide herbicide degradation products, Presented at the 49th ASMS Conference, Chicago, IL, May 27-31, 2001. 

Structurally related compounds may cross-react with the antibody, yielding inaccurate results. In screening for the herbicide alachlor in well water by immunoassay, a number of false positives were reported when compared with gas chromatography (GC) analysis. A metabolite of alachlor was found to be present in the samples and it was subsequently determined that the cross-reactivity by this metabolite accounted for the false-positive results. On the other hand, cross-reactivity by certain structural analogs may not be an issue. For example, in an assay for the herbicide atrazine, cross-reactivity by propazine is 196% because of atrazine and propazine field use... 

Because of the possibility that the herbicide alachlor could adulterate food if either poultry or livestock consumed contaminated materials, Lehotay and Miller evaluated three commercial immunoassays in milk and urine samples from a cow dosed with alachlor. They found that milk samples needed to be diluted with appropriate solvents (1 2, v/v) to eliminate the matrix effect. One assay kit (selected based on cost) was also evaluated for use with eggs and liver samples from chickens. Egg and liver samples were blended with acetonitrile, filtered, and diluted with water. Linear calibration curves prepared from fortified egg and liver samples were identical... 

Phytodegradation Soils, groundwater, landfill leachate, land application of wastewater Herbicides (atrazine, alachlor) Aromatics (BTEX) Chlorinated aliphatics (TCE) Nutrients (NO, NH4+, PO3) Ammunition wastes (TNT, RDX) Phreatophyte trees (poplar, willow, cottonwood, aspen) Grasses (rye, Bermuda, sorghum, fescue) Legumes (clover, alfalfa, cowpeas)... 

The objectives of this study were to (a) determine the mobilities of the herbicides, alachlor (2-chloro-2, 6 -diethyl-N-(me-thoxymethyl)acetanilide), butylate (S-ethyl diisobutylthiocarba-mate), and metolachlor (2-chloro-N-(2-ethyl-6-methyl phenyl)-N-(2-methoxy-l-methyl ethyl) acetamide in the laboratory using soil leaching columns and soil thin-layer vapor diffusion techniques,... 

Soil Column Leaching. The distribution of radioactivity from [ 1 C]butylate applied at 4.5 KG/HA and [1 l C]alachlor and [1 C] — metolachlor applied at 2.25 KG/HA and leached with 15 cm of water in Felton sand, is shown in Figure 4. Although all three herbicides are mobile in this soil type, butylate showed less mobility, with 59.6% of the applied raidoactivity found in the upper 10 cm of the column, while 28.4% and 24.3% of the applied 1 C was found in the upper 10 cm of the alachlor and metolachlor columns, respectively. 

Wu, T.L. 1980. Dissipation of the herbicides atrazine and alachlor in a Maryland cornfield. Jour. Environ. Qual. 9 459-465. 

In the United States, about 80% of the 23 million kg of technical PCP produced annually — or about 46% of worldwide production — is used mainly for wood preservation, especially utility poles (Pignatello etal. 1983 Kinzell etal. 1985 Zischke etal. 1985 Choudhury etal. 1986 Mikesell and Boyd 1986 USPHS 1994). It is the third most heavily used pesticide, preceded only by the herbicides atrazine and alachlor (Kinzell et al. 1981). Pentachlorophenol is a restricted-use pesticide and is no longer available for home use (USPHS 1994). Before it became a restricted-use pesticide, annual environmental releases of PCP from production and use were 0.6 million kg to the atmosphere from wood preservation plants and cooling towers, 0.9 million kg to land from wood preservation use, and 17,000 kg to aquatic ecosystems in runoff waters of wood treatment plants (USPHS 1994). There are about 470 wood preservative facilities in the United States, scattered among 45 states. They are concentrated in the South, Southeast, and Northwest — presumably due to the availability of preferred timber species in those regions (Cirelli 1978). Livestock facilities are often constructed of wood treated with technical PCP about 50% of all dairy farms in Michigan used PCP-treated wood in the construction of various components of livestock facilities (Kinzell et al. 1985). The chemical is usually applied to wood products after dilution to 5% with solvents such as mineral spirits, No. 2 fuel oil, or kerosene. More than 98% of all wood processed is treated with preservative under pressure about 0.23 kg of PCP is needed to preserve 1 cubic foot of wood (Cirelli 1978). Lumber treated with PCP retains its natural appearance, has little or no odor, and can be painted as readily as natural wood (Wood et al. 1983). 

The most important substituted anilide herbicides (Fig. 10, Table 3) are Propanil,Propachlor,and Alachlor [43,151,175-178]. 

The herbicide alachlor (4.146, Fig. 4.7) also displayed species-dependent toxicity, since it induced nasal tumors in rats but not in mice. Its metabolic scheme in rats and mice (Fig. 4.7) shows that alachlor can be transformed into 2,6-diethylaniline (4.149) by two different pathways, one of which proceeds via formation of 4.147. The other pathway implies glutathione (GSH) conjugation, followed by /3-lyase-mediated liberation of the thiol, followed by S-methylation to produce the methylsulfide 4.148. The two secondary amides 4.147 and 4.148 were hydrolyzed by microsomal arylamidases, but alachlor itself was not a substrate for this enzyme. The hydrolytic product 2,6-diethylaniline (4.149) was oxidized in nasal tissues to the electrophilic quinonimine metabolite 4.150, which can bind covalently to proteins. Aryl-... 

Koskinen et al. (1994) studied the ultrasonic decomposition of alachlor (3.1 nM) in pure water using a sonicator operating in the continuous mode at a maximum output of 20 kHz. Decomposition followed first-order kinetics and the rate increased with increasing power and temperature. The disappearance half-lives at 24, 27, and 30 °C were 375, 180, and 86 min, respectively. The authors suggested that decomposition of alachlor was probably the result of the herbicide reacting with highly reactive hydroxyl free radicals. 

Fang, C.H. Studies on the degradation and dissipation of herbicide alachlor on soil thin layers, J. Chin. Agric. Chem. Soc., 17 47-53, 1979. 

Lee, J.K. Degradation of the herbicide, alachlor, by soil microorganisms. III. Degradation under an upland soil condition, J. 

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