W8 AM Agrochemicals and Pesticides
Wednesday, 16 November 2005: 8:00 AM - 11:40 AM in 337-338

(SHA-1117-837956) Role of particulate soil organic matter in the equilibrium sorption of pesticides.

Huang, Weilin¹, Sharma, Samriti¹, ¹ Rutgers University, New Brunswick, New Jersey, USA

ABSTRACT- We examined the differential roles of different types of soil organic matter (SOM) on the sorption of atrazine, metolachlor and napropamide by soils. These chemicals are commonly used herbicides in the US and are frequently detected in the groundwater and surface aquatic systems. Sorption to soils and sediments is the major phenomenon retarding transport and limiting bioavailability of these chemicals in the environment. To elucidate the mechanisms of pesticide sorption to SOM, organic matter from a soil was fractionated into operationally defined base extracted fraction (BE), humic acid fraction (HA), and kerogen and black carbon fraction (KB). KB is non-extractable particulate SOM. These samples, along with the original soil (OS) were used as the sorbents for the sorption study using a batch reactor system and with an equilibration time of 21 days. The results indicated that the KB fraction dominates the overall sorption process with greater sorption capacities and more nonlinear isotherms. The HA fraction exhibits more linear sorption isotherms, and its contribution to the overall sorption is limited. The results also show that the original soil has sorption capacities lower than the isolated fractions, suggesting that when associated with soil aggregates, the KB fraction may not be fully accessible to the sorbing pesticide molecules.

Key words: herbicide, sorption