2,4-Dichlorophenoxyacetic acid (2,4-D) sorption and degradation dynamics in three agricultural soils.
The fate and transport of 2,4-dichlorophenoxyacetic acid (2,4-D) in the subsurface is affected by a complex, time-dependent interplay between sorption and mineralization processes. 2,4-D is biodegradable in soils, while adsorption/desorption is influenced by both soil organic matter content and soil pH. In order to assess the dynamic interactions between sorption and mineralization, 2,4-D mineralization experiments were carried using three different soils (clay, loam and sand) assuming different contact times. Mineralization appeared to be the main process limiting 2,4-D availability, with each soil containing its own 2,4-D decomposers. For the clay and the loamy soils, 45 and 48% of the applied dose were mineralized after 10 days. By comparison, mineralization in the sandy soil proceeded initially much slower because of longer lag times. While 2,4-D residues immediately after application were readily available (>93% was extractable), the herbicide was present in a mostly unavailable state (<2% extractable) in all three soils after incubation for 60 days. We found that the total amount of bound residue decreased between 30 and 60 incubation days. Bioaccumulation may have led to reversible immobilization, with some residues later becoming more readily available again to extraction and/or mineralization.
Boivin
Arnaud
A
George E. Brown, Jr. Salinity Laboratory, USDA-ARS, 450 West Big Springs Road, Riverside, CA 92507-4617, USA. aboivin@ussl.ars.usda.gov
Amellal
Samira
S
Schiavon
Michel
M
van Genuchten
Martinus Th
MT
D015084:2,4-Dichlorophenoxyacetic Acid; D000327:Adsorption; D000383:Agriculture; D000538:Aluminum Silicates; D001673:Biodegradation, Environmental; D000077215:Clay; D006540:Herbicides; D006863:Hydrogen-Ion Concentration; D012822:Silicon Dioxide; D012987:Soil; D012988:Soil Microbiology; D012989:Soil Pollutants; D014877:Water Pollution, Chemical
D000538:Aluminum Silicates; D006540:Herbicides; D012987:Soil; D012989:Soil Pollutants; D015084:2,4-Dichlorophenoxyacetic Acid; D012822:Silicon Dioxide; D000077215:Clay