NOM AND TRACE METAL ATTENUATION DURING STORM-WATER INFILTRATION

The increasing practice of infiltration in disposal of storm-water runoff leads to concerns over the long-term quality of receiving ground waters. To ensure that best management practices are employed, understanding the fate and transport of applied trace pollutants within the vadose zone must be improved. This study is directed at expanding the knowledge base governing facilitated transport of heavy metals by dissolved or particulate natural organic matter (NOM). Experimental studies were conducted to evaluate the effects of NOM on the mobility of trace quantities of cadmium, copper, lead, and zinc dissolved in water infiltrating through near-surface soils. Large-scale soil columns (on order of 1 m) were tested under periodic loading conditions thought to be similar to those experienced under actual infiltration scenarios. The corresponding metals transport was observed as function of depth and volume eluted. Increased concentrations of NOM yielded greater metal attenuation within the soils tested. Explanation of these results focus on the possible presence of organo-metallic complexes that exhibit a high affinity for the soil matrix.