Developing Triage Assessment Tools for Old Landfills and Arsenic

This study's objective is to test whether the As/Fe ratio measured in iron flocculates can predict As in groundwater. Iron flocculates often exist in springs and seeps near old landfills due to the vertical relief of the sites. Groundwaters downgradient from old, unlined landfills can be quite reducing due to the influence of landfill leachate and can mobilize naturally occurring arsenic from natural soils. Mobilized Arsenic can be observed from the elevated groundwater concentrations in monitoring wells downgradient from old landfills. There are more than 200 inactive municipal solid waste landfills in the seven counties of New York's lower Hudson region. The majority of these facilities are unlined landfills which were operated by municipalities, and about three quarters of these do not have any groundwater monitoring programs in place. The combination of large numbers of old landfills with the increasing occurrence of new housing developments nearby suggests that there is potential for unregulated private wells to be tapping into arsenic-rich groundwater. Finding and sampling seeps with iron flocculates is an attractive alternative for tracing landfill-mobilized arsenic, since it is relatively easy compared to sinking monitoring wells. Preliminary data from landfills in Maine, Massachusetts and New York's lower Hudson region suggest that flocculates show promise as a simple, cheap assessment tool. The As concentration in flocculates adjacent to landfills varies from 2 to 628 ppm, and the As/Fe ratio in the flocculates appears roughly indicative of groundwater As concentrations in the plumes downgradient of impacted monitoring wells. More work needs to be done to understand the relationship of flocculate chemistry to that of heterogeneous groundwater plumes.