|TRIGO, CARMEN - Consejo Superior De Investigaciones Cientificas (CSIC)|
|COX, LUCIA - Consejo Superior De Investigaciones Cientificas (CSIC)|
Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2016
Publication Date: 10/1/2016
Citation: Trigo, C., Cox, L., Spokas, K.A. 2016. Influence of pyrolysis temperature and hardwood species on resulting biochar properties and their effect on azimsulfuron sorption as compared to other sorbents. Science of the Total Environment. 566-567:1454-1464. doi:10.1016/j.scitotenv.2016.06.027.
Interpretive Summary: The environmental risk of applied pesticides to soils is often assessed through sorption experiments to guide field management decisions. Application of biochar is one amendment that has been receiving attention as a means to reduce the environmental risk of applied pesticides to surface and groundwater resources. In this study we evaluated several different hardwood species and compared the sorption to that of geological mineral materials to assess the degree of sorption. The sorption of an acidic herbicide (azimsulfuron) did increase with temperature of the biochar. However, the impact on leaching was hardwood species specific, with no impact observed from apple wood biochar, while significant reductions were observed were montmorillonite additions. This strongly suggests the need to assess biochar behavior before application of a biochar to mitigate pesticide transport. The data also supports the conclusion that clay additions were superior than apple wood biochar at reducing the total amount of herbicide leached through the soil. These results are significant to farmers and policy makers and will assist scientists and engineers in developing improved models for assessing agrochemical leaching risks based on mechanistic processes, which should be utilized in developing improved assessments of the fate and transport of applied agrochemicals.
Technical Abstract: Azimsulfuron is an acidic herbicide with a high water solubility which makes risk of groundwater contamination a concern. Various wood based biochars produced at different pyrolysis temperatures were characterized along with their sorption capacity for the herbicide azimsulfuron. In addition, we compared sorption on biochars with sorption on mineral sorbents such as clay minerals and iron oxides. In biochar formed at high temperatures (500 and 700 C), FT-IR studies confirmed the increase in aromaticity. SEM images of the biochars showed differences in the macroporous structure and lower size pores at higher temperatures. SSA of the biochars increased with pyrolysis temperature and, for all different biochars, this resulted in higher sorption of azimsulfuron. In the case of mineral sorbents, sorption is not related to SSA. Higher sorption is observed in a montmorillonite, of lower SSA, than in mixture of clay minerals with 30 % smectite (w/w). On the contrary as with the clays, sorption on the two iron oxyhydroxides increased with SSA. Desorption studies showed hysteresis. Leaching studies showed no effect on azimsulfuron retention on soil column amended with apple wood biochar, while a reduction of azimsulfuron in leachates in soil columns amended with the pure montmorillonite.