Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2014
Publication Date: 3/16/2014
Citation: Rittenhouse, J.L., Rice, P.J., Spokas, K.A., Koskinen, W.C. 2014. Assessing biochar's ability to reduce bioavailability of aminocyclopyrachlor in soils. Environmental Pollution. 189:92-97.
Interpretive Summary: In this study, the use of biochars as a potential tool for the sorption of a new herbicide (aminocyclopyrachlor) was evaluated for a variety of different biochars and three Minnesota soils. Adsorption-desorption studies were performed using a batch equilibration method. The major finding in this work was that for the six different biochars evaluated here, the addition of biochar to soil did not significantly alter the sorption of the herbicide. Additional research was done to show, that steam activation of biochar did increase the sorption of this particular herbicide, which increased the sorption approximately four times. The greatest sorption was observed with activated charcoal, indicating that even though biochar is close to the chemical properties of activated charcoal, biochar is not as effective at sorbing aminocyclopyrachlor as activated charcoal. Additional research is needed to fully characterize the surface chemistry responsible for these effects. These findings could provide additional insight and direction in the focus of the benefits of biochar additions on plant and soil microbial communities. These results are significant to farmers and policy makers and will assist scientists and engineers in developing improved biochars based on properties to minimize agrochemical transport and improve soil carbon management.
Technical Abstract: Aminocyclopyrachlor is a pyrimidine carboxylic acid herbicide used to control broadleaf weeds and brush. Amending soil with activated charcoal is recommended to prevent off-site transport of aminocyclopyrachlor and non-target plant damage. We used the batch-equilibrium method to determine the concentration of aminocyclopyrachlor in a pseudo-steady state with biochar, soil, and biochar-soil systems (<10% biochar by weight). We observed that aminocyclopyrachlor is mobile in soils. Soil incorporation of activated charcoal removed nearly all of the aqueous aminocyclopyrachlor thereby limiting its bioavailability to non-target flora. On the other hand, biochars were less effective than activated charcoal. Biochar produced from olive mill waste feedstock was the most effective biochar that we assessed for reducing the aqueous herbicide concentration. Although these biochars reduced the aminocyclopyrachlor concentration, they would not be practical remediation media due to the extraordinarily high application rates required to reduce the concentration by 50% (2.13 × 105 kg ha-1–7.27 × 105 kg ha-1).