Degradation of imazosulfuron in soil.
Imazosulfuron, 1-(2-chloroimidazo[1,2-alpha]pyridin-3-ylsulfonyl)-3- (4,6-dimethoxypyrimidin-2-yl)urea, is a new post-emergence sulfonylurea herbicide applied once per growing season, highly active at low application levels, used to control most annual and perennial broad-leaf weeds and sedges in paddy rice (75-95 g AI ha-1) and turf (500-1000 g AI ha-1), and characterised by low mammalian toxicity. The degradation of imazosulfuron in a sandy loam soil (10-15 cm depth) has been investigated under aerobic and anaerobic laboratory conditions to evaluate its likely environmental fate. Test soils were treated with imazosulfuron in acetonitrile to give a final concentration of 0.2 mg kg-1 (100 g ha-1). The treated soils were extracted with methylene chloride + acetonitrile + 1 M ammonium hydroxide (4 + 15 + 1 by volume) and analysed by HPLC. Recoveries from spiked soils ranged from 80% to 95% (RSD 0.5-2.5%; n = 3) for imazosulfuron and its metabolites 2-chloroimidazo[1,2-alpha]pyridin-3-sulfonamide (IPSN), 1-(2-chloroimidazo[1,2-alpha]pyridin-3-ylsulfonyl)-3-(4-hydroxy-6- methoxypyrimidin-2-yl)urea (HMS) and 2-amino-4,6-dimethoxypyrimidine (ADPM). The limits of quantitation ranged from 0.001 mg kg-1 to 0.005 mg kg-1. Chemical cleavage of the sulfonylurea bond to give ADPM and IPSN was the main degradation pathway in aerobic conditions, whereas a remarkable production of HMS under anaerobic conditions suggested that degradation was due to micro-organisms which had the ability to demethylate imazosulfuron. In aerobic and anaerobic conditions, imazosulfuron disappeared from the soil with a half-life of approximately 70 (90% CL 62-75; r2 = 0.98) and 4 (90% CL 3.2-4.2; r2 = 0.97) days, respectively.
Morrica
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P
Dipartimento di Chimica Farmaceutica e Tossicologica, Università degli Studi di Napoli Federico II, Via D Montesano 49, 80131 Naples, Italy. morrica@unina.it
Giordano
A
A
Seccia
S
S
Ungaro
F
F
Ventriglia
M
M
D000332:Aerobiosis; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004784:Environmental Monitoring / Q000379:methods; D006207:Half-Life; D006540:Herbicides / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D011725:Pyridines / Q000737:chemistry / Q000378:metabolism*; D011743:Pyrimidines / Q000737:chemistry / Q000378:metabolism*; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*; D013453:Sulfonylurea Compounds
D006540:Herbicides; D011725:Pyridines; D011743:Pyrimidines; D012987:Soil; D012989:Soil Pollutants; D013453:Sulfonylurea Compounds; C433346:1-(2-chloroimidazo(1,2-a)pyridin-3-ylsulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl)urea