Effect of biobed composition, moisture, and temperature on the degradation of pesticides.

Biobeds retain and degrade pesticides through the presence of a biobed mixture consisting of straw, peat, and soil. The effects of biobed composition, moisture content, and temperature on pesticide degradation were investigated in laboratory studies. Straw produced the main microbial activity in the biobed mixtures as strong positive correlations were observed between straw, respiration, and phenoloxidase content. Most pesticides investigated were dissipated by cometabolic processes, and their dissipation was correlated with respiration and/ or phenoloxidase content. More pesticides were more dissipated at biobed moisture levels of 60% water holding capacity (WHC) than at 30% and 90% WHC, while 20 degrees C gave higher dissipation rates than 2 and 10 degrees C. A straw:peat:soil ratio of 50:25:25% v/v is recommended in field biobeds since this produces high microbial activity and low pH, favorable for lignin-degrading fungi and phenoloxidase activity.