Presenter: Samuel Gregory, Massey University

Presentation title: Use of biochar for the sustainable remediation of sheep dip sites

Application of biochar to a soil contaminated with organochlorines and arsenic (As) from a past agricultural practice known as sheep dipping was analysed to investigate its effects on contaminant mobility and plant growth characteristics during a 180 d glasshouse and field trial study. Soil from a known dip site was removed and treated with biochar made from a willow (Salix sp.) feedstock (pyrolysed at 350°C and 550°C) added at 20 t ha-1 and 40 t ha-1 to gauge the appropriate treatments to be used in a later field trial. Soil microbial activity as analysed using the dehydrogenase activity assay (DHA) was significantly increased (P<0.01) under all biochar amendments. After 60 d of amendment, biochar containing soils underwent > 100% increase in DHA resulting in significant decreases in alpha-HCH (10-fold) and gamma-HCH (3-fold) concentrations in soil. Significant reductions in DDT with biochar amendment were also noticed after 180 d of treatment compared to unamended soils. Biochar did not increase water-extractable arsenic concentrations but significantly (P<0.05) increased phytoextraction into both a arsenic hyperaccumulator fern (Pteris cretica) and ryegrass (Lolium perenne). Ryegrass growth was signifcantly increased (P<0.01) under biochar amendment with 2-fold increase in shoot dry weight and 3-fold increase in root dry weight after 180 d. These results have the potential to reduce the remediation time of contaminated soil and decrease the environmental risk to nearby ecosystems.

Event: WasteMINZ Conference 2013

Date: Wednesday 23 October 2013