Dichlobenil and 2,6-dichlorobenzamide (BAM) dissipation in topsoil and deposits from groundwater environment within the boreal region in southern Finland.

BAM (2,6-dichlorobenzamide) is a metabolite of pesticide dichlobenil and a common groundwater contaminant. Dichlobenil and BAM half-lives were determined in five Finnish subsurface deposits and in topsoil. Aerobic and anaerobic conditions with sterilized controls were included in this 1.4-year incubation experiment. In subsurface deposits, dichlobenil half-life varied from 157 days to no degradation and that of BAM from 314 days to no degradation. Microbes and oxygen enhanced dichlobenil and BAM dissipation rates in some deposits. However, dichlobenil and BAM concentrations were most significantly affected by deposit characteristics, especially carbon and nitrogen amounts. Also low pH, cadmium, iron, zinc, manganese and lead correlated with low dichlobenil and/or BAM concentrations. In mineral topsoil, dissipation was faster with half-lives of 41-54 days for dichlobenil, and 182-261 days for BAM. Dichlobenil was depleted completely in surface soil, but BAM was not dissipated below 55-81 % of the initial concentration. Generally, dichlobenil and BAM dissipation in samples from the northern boreal region was similar to that reported for the temperate region. BAM was persistent in topsoil and subsurface deposits, indicating long-term persistence problems in groundwater also within the northern boreal region.