Publication Summary

Wetlands adjacent to the B&L Landfill were investigated to evaluate the impacts of arsenic contaminated groundwater discharge. Surface waters exceeded the arsenic ambient water quality standards. Soil arsenic levels were slightly higher at study locations and porewater arsenic concentrations were highest closest to the landfill. Samples of plant roots sequestered significant quantities of arsenic, but translocated little to shoots or biotransformed. Microtox bioassays found statistically significant depression of relative light output throughout the study area relative to controls. A weight of evidence evaluation concluded that overall wetland health was poor to moderate.

The B&L Landfill, located in Milton, is composed of wood waste and slag. Adjacent to the landfill, extensive reed canary grass (Phalaris arundinacea) wetlands are present in an area with arsenic contaminated groundwater. This investigation was undertaken to determine the fate and transport of potential arsenic discharges and their impacts on wetland biota.

The study was conducted during late winter and spring of 2002. Initial surface water quality sampling on March 10 found one station with concentrations of 556 µg/L total arsenic, which exceeds the chronic water quality standard of 190 µg/L. Follow-up surface water sampling on May 6 determined that the bulk of arsenic in surface water was not identifiable to arsenic species, as it was likely bound to a particulate fraction.

Soil concentrations of lead, copper, and zinc were not elevated in zones closest to the landfill relative to the control locations. Soil arsenic concentrations were slightly higher in surficial soils at all study locations relative to the control location. Soil arsenic concentrations slightly exceeded the Model Toxics Control Act residential soil standard of 20 mg/Kg.

In general, pore-water metals concentrations were not elevated in areas of likely groundwater discharge relative to control stations. The exception was for total arsenic which was found at concentrations up to 397 µg/L nearest the landfill. Bioassays were conducted on soil pore waters using the Microtox bioassay. Statistically significant depression of Microtox relative light output was found throughout the study area relative to control locations.

Samples of plant root and shoot tissues demonstrated that, where arsenic concentrations are high, roots sequester significant quantities of arsenic, but less than 1% is translocated between roots and shoots. Additionally, the majority of this arsenic is in the inorganic form, and little arsenic is biotransformed by plants into less toxic organic forms.

Link to EIM data for User Study ID RJAC003