title: Herbicide sorption to fine particulate matter suspended downwind of agricultural operations: field and laboratory investigations.
abstract: Tillage-induced erosion of herbicides bound to airborne soil particles has not been quantified as a mechanism for offsite herbicide transport. This study quantifies the release of two preemergent herbicides, metolachlor and pendimethalin, to the atmosphere as gas- and particle-phase species during soil incorporation operations. Fine particulate matter (PM2.5) and gas-phase samples were collected at three sampling heights during herbicide disking into the soil in Davis, CA, in May 2000 and May 2001 using filter/PUF sampling. Quartz fiber filters (QFFs) were used in May 2000, and Teflon membrane filters (TMFs) were used in May 2001. The field data were combined with laboratory filter/PUF partitioning experiments to account for adsorption to the filter surfaces and quantify the mass of PM2.5-bound herbicides in the field samples. Laboratory results indicate a significant adsorption of metolachlor, but not pendimethalin, to the quartz filter surfaces. Metolachlor partitioning to PM2.5 collected on TMF filters resulted in corrected PM2.5 field partition coefficient values, Kp,corr = Cp/Cg, of approximately 10(-3.5) m3/microg, indicating its preference for the gas phase. Pendimethalin exhibited more semivolatile behavior,with Kp,corr values that ranged from 10(-3) to 10(-1) m3/ microg and increased with sampling height and distance downwind of the operation. An increase in pendimethalin enrichment at a height of 5 m suggests winnowing of finer, more sorptive soil components with corresponding higher transport potential. Pendimethalin was enriched in the PM2.5 samples by up to a factor of 250 compared to the field soil, indicating thatfurther research on the processes controlling the generation of PM-bound herbicides during agricultural operations is warranted to enable prediction of off-site mass fluxes by this mechanism.
authors.affiliation: CH2M Hill, Sacramento, California, USA.
authors.forename: Amelia S
authors.initials: AS
authors.lastname: Clymo
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Shin
authors.forename: Britt A
authors.initials: BA
authors.lastname: Holmen
mesh_terms: D000081:Acetamides / Q000032:analysis / Q000737:chemistry*; D000327:Adsorption; D000383:Agriculture; D000814:Aniline Compounds / Q000032:analysis / Q000737:chemistry*; D001272:Atmosphere; D004784:Environmental Monitoring; D008567:Membranes, Artificial; D010316:Particle Size; D012989:Soil Pollutants / Q000032:analysis*; D014835:Volatilization; D014919:Wind
chemical_list: D000081:Acetamides; D000814:Aniline Compounds; D008567:Membranes, Artificial; D012989:Soil Pollutants; C030856:pendimethalin; C051786:metolachlor