Glyphosate degradation on biobeds: study of different biomixtures

MAIA LESCANO; DANIELA BUSCHIAZZO; CRISTINA ZALAZAR

Buenos Aires

Congreso; The Fifth International Symposium on Environmental Biotechnology and Engineering (5ISEBE); 2016

Biobeds are used to collect and decontaminate liquids with high concentration of pesticide residues. It consists on a biomixture of three components: soil, lignocellulosic and wetting materials which are mixed at different volume ratios. Straw and peat are used in the first biobeds made in Sweden. The biomixture has the ability to retain and degrade pesticides: the soil provides sorption capacity and also an active microbial community for pesticide degradation; peat increases the sorption capacity and contributes to moisture control and straw, is the main substrate for microbial activity, especially by lignin-degrading fungi producing phenoloxidases for pesticide degradation.1In order to apply this kind of system in Argentina, it is necessary to propose designs that can take into account low cost available materials to degrade the most widely pesticides used. In this line, glyphosate has become the most used herbicide in last years producing high concentrated residues. Therefore, in this study, in order to treat effluents containing glyphosate, new designs of biobeds were proposed. Since the use of peat is not environmentally or economically feasible in Argentina, a locally available material called ?resaca? that can be easily obtained from the river was tested. Also, two different soils soil that has been cultivated with soybeans (A) and soil that has not been cultivated (B) and two different lignocellulosic materials (alfalfa straw and wheat stubble) were tested. Eight biobeds were built at laboratory scale employing glass boxes and eight different biomixtures (B1: soil B+ straw + resaca; B2: soil B + stubble; B3: soil B + stubble + resaca; B4: soil B + straw; A1: soil A + stubble + resaca; A2: soil A + straw; A3: soil A + straw + resaca; A4: soil A + stubble). Biomixtures were matured for 50 days measuring temperature and moisture content daily. Then, commercial glyphosate concentrated was applied in all boxes in order to obtain 1000 mg glyphosate/kg of dry biomixture. The degradation assays were carried out for 63 days taking sample at 0 (initial), 4, 25, 45 and 63 days for extraction and glyphosate and AMPA quantification by chromatographic techniques.Results have shown that in all biomixtures high glyphosate degradation percentages were achieved (up to 90%) after 63 days being A4 (soil A + stubble) the one that presents highest degradation rate (75% for glyphosate degradation within 25 days). Also the presence of AMPA was measured and the potential capacity of its degradation through the biomixture during the experience was observed. In addition, biomixture A1 has shown better capacity to remain moisture content constant. This study has proved that local materials are suitable to build efficient and low cost biobeds in order to treat effluents with high glyphosate concentration.