Degradation alachlor

Figure 14. Alachlor degradation with time, a, amount in soil and water o, amount in water.

In an effort to enhance detoxification of high concentrations of alachlor, we designed studies to test the effects of soil dilution, concentration, formulation, and nutrient amendments on persistence. Additionally, we developed a protocol to enrich, isolate, and screen bacteria and fungi for enhanced capabilities of alachlor degradation. Our studies represent the intital stages of the biostimulation and bioaugmentation strategies for waste cleanup. 

Soil used in the alachlor persistence studies and in the enrichments for alachlor-degrading organisms was derived from two sources a waste site at an agrochemical facility in Piatt Co., IL and a soybean plot near the waste site that was divided into replicated blocks for a land application study (24.) The soil type was a mixture of Ipava silt loam (fine, montmorillonitic, mesic, Aquic Argiudolls) and Sable silty clay loam (fine silty mixed, mesic, Typic Haplaquolls) with pH 5.4-5.5. The soil at the waste site had been excavated and stored in piles which were sampled as needed for laboratory studies (waste-pile soil). Untreated check plots in the soybean field served as sources of uncontaminated soil (CHECK soil). Soils were stored at 2-4°C and passed through a 3-mm screen before use. 

Screening of Fungi for Alachlor Degradation. Fungal isolates CCF-1 (tentatively identified as Fusarium sp.) and CCF-2 degraded more than 70% and 50%, respectively of a 100 ppm dose of alachlor after 14 days of incubation in peptone-yeast extract medium (PYA1). About 18% of the... 

After 56 days of incubation, degradation of 1000 ppm alachlor did not exceed 35% in any soil treatment (Table VI). About 33% of the applied alachlor was degraded in the inoculated, CS-amended soil after 28 days, but no further degradation was observed thereafter. In nearly every two-way comparison, alachlor degraded significantly faster in the 100 ppm treatments than in the 1000 ppm treatments. Coincidentally, soil dehydrogenase activity in all 1000 ppm treatments was severely depressed. 

Biodegradation is much dependent on the pH, moisture, temperature, and type of soil. Jurado-Exposito has shown that alachlor degradation increases with temperature and soil moisture. A laboratory study on the biodegradation of butachlor and acetochlor in soils showed that... 

Alachlor was degraded in soil and aquifer matrix material. The amount of alachlor that remained under aerobic conditions after 112 d ranged from 30% in the B horizon soil to about 80% in the C2 soil (Figure 3). Under anaerobic conditions, alachlor degradation was much less, widi 70% or more of the applied alachlor remaining after 112 d. 

The addition of the algae biomass under aerobic condition increased alachlor degradation in the A horizon soil and die F and S sediments. At the end of 112 d in treatments with C addition, less than 2% of alachlor remained in the A horizon soil whereas about 30% alachlor remained in the F and 10% remained in the S sediments. Under anaerobic conditions, the addition of N increased degradation in the F and S sediments with about 70% remaining as alachlor (vs about 80% without N addition). 

Table 2. Radioactive regions (+) of thin layer chromotographic plates. The letter s indicates that a lesser amount of this compound was detected than when the sediment was untteated. Extracts were obtained from soil and aquifer sediment 112 d after alachlor treatment (incubation temperature of 10 C). Letters behind the Rf value refer to alachlor degradation products shown in Figure 2. Anodier alachlor compound that cocomatagraphed to 0.6S was 2-chloro-2, 6 -diedialacetanilide.

Wei LY, CR Vossbrinck (1992) Degradation of alachlor in chironomid larvae (Diptera Chironomidae). J Agric Food Chem 40 1695-1699. 

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. 

Propachlor, alachlor, acetochlor, and butachlor degrade readily and extensively in soil mainly through displacement of chlorine followed by further metabolism to numerous... 

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. 

Wang X, Zhang Y (2009) Degradation of alachlor in aqueous solution by using hydrodynamic cavitation. J Fiaz Mater 161 202-207... 

In soil, alachlor is photolytically unstable. After an 8-h exposure to sunlight, degradation yields in a sandy loam, loam, silt loam, and clay were 22, 27, 36, and 39%, respectively. Degradation appeared to be enhanced in soils having low organic carbon content and low pH (Fang et al., 1979). 

Persistence in soil is approximately 6 to 10 wk (Hartley and Kidd, 1987) but is moderately slower in sandy soils low in organic matter (Ashton and Monaco, 1991) and much slower under sterilized conditions. In nonsterile soils, 39-54% of the applied amount degraded after 28 d (Fang, 1983). The half-lives for alachlor in soil containing 6 and 15% moisture were 23 and 5.7 d, respectively (Walker and Brown, 1985). In a Ustollic Haplargid clay with 1.1% organic matter. 

Surface Water. 2,6-Dichloroaniline, 2-chloro-2, 6 -diethylacetanilide, and 2-hydroxy-2, 6 -dieth-ylacetanilide were reported as possible degradation products of alachlor that were identified in the Mississippi River and its tributaries (Pereira and Rostad, 1990). 

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. 

Somich, C.J., Kearney. P.C., Muldoon, M.T., and Elsasser, S. Enhanced soil degradation of alachlor by treatment with ultraviolet light and ozone, /. Agric. Food Chem., 36(6) 1322-1326, 1988. 

Tiedje, J.M. and M.E. Hagedorn. Degradation of alachlor by a soil fungus, Chaetomium globosum, J. Agric. Food Chem., 3(1) 77-81, 1975. 

Studies were initiated at Iowa State University in 1977 to determine if pesticides would be contained and degraded when deposited in water/soil systems. Although the addition of known amounts of the selected pesticides was controlled, the physical environment was not temperature, humidity, wind speed, etc. were normal for the climate of Central Iowa. Four herbicides and two insecticides were chosen on the basis of three factors. Firstly, they represented six different families of pesticides. The four herbicides, alachlor, atrazine, trifluralin, and 2,4-D ester, represent the acetanilides, triazines, dinitroanilines, and phenoxy acid herbicides, respectively. The two insecticides, carbaryl and para-thion, represent the carbamate and organophosphorus insecticides, respectively. Secondly, the pesticides were chosen on the basis of current and projected use in Iowa Q) and the Midwest. Thirdly, the chosen pesticides were ones for which analytical methodology was available. 

Most acetanilides are biodegraded rapidly in soil, but alachlor appears to be degraded by a mechanism different from that for other members of this group of herbicides. The presence of either the 2, 6 -dialkyl substituents, the N-alkoxylmethyl substituent, or both, may preclude enzymatic hydrolysis of the carbonyl or... 

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