title: The fate of imazapyr in a Swedish railway embankment.
abstract: The long-term fate of the herbicide imazapyr [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid] applied to a Swedish railway embankment was studied. Imazapyr was applied at 750 and 1500 g ha(-1) by a spraying train used for full-scale herbicide treatment operations. Soil and groundwater were sampled twice a year for 8 years after application of the herbicide, and the dissipation of imazapyr was studied by HPLC analysis of the residues in soil and groundwater. A clean-up procedure including solid-phase extraction was performed prior to detection by HPLC. Recoveries of imazapyr from soil and water samples were 76-98% and 61-90%, respectively, and detection levels were 0.003 mg kg(-1) and 0.05 microg litre(-1), respectively. Sorption, desorption and microbial amount and activity were also measured at the two locations. The organic matter content correlated positively and the pH negatively to the adsorption of imazapyr on soil, and increasing organic matter contents decreased desorption. Apart from the 0-10-cm top layers of both sites, the microbial amount and activity were small. The main proportion of imazapyr was found in the upper 30 cm of the soil, and degraded with a half-life in the range 67-144 days. Small amounts were transported to lower soil layers and to the groundwater in proportion to the amounts applied. Traces of imazapyr were detected in the groundwater even 8years after application. It was concluded that environmental risks from the use of herbicides on railway embankments could be reduced by including adsorption layers in the embankment during their construction and by reducing the dose of the herbicide used.
authors.affiliation: Swedish University of Agricultural Sciences, Department of Microbiology, PO Box 7025, SE-750 07 Uppsala, Sweden. Elisabet.Borjesson@mikrob.slu.se
authors.forename: Elisabet
authors.initials: E
authors.lastname: Börjesson
authors.forename: Lennart
authors.initials: L
authors.lastname: Torstensson
authors.forename: John
authors.initials: J
authors.lastname: Stenström
mesh_terms: D000327:Adsorption; D002851:Chromatography, High Pressure Liquid; D006207:Half-Life; D006540:Herbicides / Q000032:analysis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000032:analysis* / Q000737:chemistry; D007700:Kinetics; D009525:Niacin / Q000031:analogs & derivatives* / Q000032:analysis* / Q000737:chemistry; D010573:Pesticide Residues / Q000032:analysis* / Q000737:chemistry; D011890:Railroads; D012989:Soil Pollutants / Q000032:analysis*; D013548:Sweden; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D006540:Herbicides; D007093:Imidazoles; D010573:Pesticide Residues; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D009525:Niacin; C076656:imazapyr