Evaluation of Garden Crop Mercury Uptake and Potential Exposure from Consumption of Garden Crops Grown on Floodplain Soils

ABSTRACT

This study investigated Hg uptake from soil into garden crops to help assess the significance of human consumption of crops as a potential route of exposure to Hg. Locations for both a floodplain and a control garden were identified within the Augusta Forestry Center near Crimora, VA, USA, which is about 16 river-km downstream from the city of Waynesboro, along the South River. The floodplain garden had measured soil Hg concentrations ranging from 4.2 to 78 mg Hg kg⁻¹ dry weight basis in the surface to 15-cm deep layer. A total of 139 samples from the floodplain garden from 17 different crops were analyzed for Hg. All crop samples (except for nine) had less than 0.1 μg Hg g⁻¹ wet weight basis (ww). Many samples were less than the method detection limit (MDL) of 0.003 μg Hg g⁻¹ ww. Based on the measured Hg concentrations and several conservative assumptions (e.g., Hg assumed present when less than MDL; 100% consumption from the geographical area in which study was conducted; and 100% bioavailable Hg as methyl Hg), consumption of crops with these Hg levels is not expected to be a significant route of Hg exposure.

Key Words:

• Hg
• crop uptake
• hazard quotient
• exposure
• potential average daily dose
• floodplain gardens.

ACKNOWLEDGMENTS

The authors thank Augusta Forestry Center personnel, especially Larry Estes; the South River Science Team, especially Don Kain (Virginia Department of Environmental Quality); several James Madison University students including Lydia Cubbage, Allison Kelley, Zamda Lumbi, and Susie Temple; Barry Wolstenholme and Mark Starr (DuPont Co.); Mike Schifflet (INVISTA); Sharon Nordstrom and Barbara Rhodes (URS Diamond); and the people at Lancaster Laboratories and Studio Geochemica for their advice in sample collection, preparation, and analysis. In addition, the contributions of Dr. Khizar Wasti (Virginia Department of Health) in the evaluation of the data from a health perspective are much appreciated. This research was funded by the DuPont Co. Corporate Remediation Group.

The findings and conclusions in this report are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency.