ABSTRACT
Nitrate and pesticides are the agrichemical contaminants of foremost concern because of their potential impacts on both public health and ecosystem function, and because of the widespread use of nitrogen and pesticides in modern agriculture. The environmental impacts of agrichemical contamination of surface and groundwaters are a special concern in the Midwest. Non-point loads of nutrients to surface waters in this region are among the highest in the country, and there is contamination of surface and groundwater by a variety of pesticides. Nitrate loss in mesocosm and microcosm studies can be described as a first-order process over a wide range of concentrations, and loss rates can be modeled based on factors controlling the rate of nitrate flux to anaerobic sites. Based on measurements of macrophyte production, litter decomposition, benthic aerobic metabolism, and denitrification, the mesocosms reasonably simulate nearby emergent wetlands. In addition, the mesocosms have proven to be remarkably replicable in both flowthrough and batch dose modes of operation.
