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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #263124
Title: Sorption-desorption of aminocyclopyrachlor in selected Brazilian soils

Author
item OLIVEIRA, RUBEM - University Of Maringa
item ALONSO, DIEGO - University Of Maringa
item Koskinen, William

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2011
Publication Date: 3/8/2011
Citation: Oliveira, R.S., Alonso, D.G., Koskinen, W.C. 2011. Sorption-desorption of aminocyclopyrachlor in selected Brazilian soils. Journal of Agricultural and Food Chemistry. 59(8):4045-4050.

Interpretive Summary: Aminocyclopyrachlor is a new herbicide from a new class of chemistry known as pyrimidine carboxylic acids. Although aminocyclopyrachlor has exhibited a number of positive stewardship attributes with very low impact to mammals and the environment, not much is known about its fate in soil. Aminocyclopyrachlor sorption and desorption was investigated in 14 soils from Brazil, presenting a range of pH, and organic carbon (OC) and clay contents. Results suggest that although aminocyclopyrachlor would be very mobile based on its sorption coefficients; pesticides that are highly soluble in water, minimally sorbed by soil particles, and not readily degradable can move rapidly with water and hence, have a high potential to be found in surface and ground waters. However, if sorption coefficients are used to predict mobility, its potential mobility may be overestimated due to its desorption characteristics; it does not readily desorb from soil. These data are the first published data on aminocyclopyrachlor sorption-desorption in soil. However, for scientists to better evaluate potential mobility, information is needed on aminocyclopyrachlor degradation and sorption of aged residues.

Technical Abstract: Aminocyclopyrachlor sorption and desorption was investigated in 14 soils from Brazil, presenting a range of pH, and organic carbon (OC) and clay contents. Sorption kinetics demonstrated that soil-solution equilibrium was attained in a 24-h period. Freundlich equation adequately described behavior of aminocyclopyrachlor in soil. Freundlich sorption coefficient (Kf) values ranged from 0.06 to 1.64 and 1/n values for sorption were 0.90. Sorption was correlated to OC (Kf,oc ranged from 11 to 64) and clay contents. The lowest sorption was found for soils with very low OC contents (0.50-0.65%) and loamy-sand to sand textures. The 1/n values for desorption were lower than those observed for sorption, suggesting that aminocyclopyrachlor sorption by soil was not reversible; hysteresis coefficients ranged from 0.13 to 0.74. The results suggest that although aminocyclopyrachlor would be very mobile based on its sorption coefficients, its potential mobility may be overestimated due to the hysteretic desorption.