Mercury Uptake by Wild Rice Plants in Northern Minnesota

Abstract

Mercury (Hg) is a naturally occurring element that can be taken up by microbes, converted into toxic, organic methylmercury (MeHg), and exported into surrounding sediment. The MeHg can then be taken up by plants through rhizofiltration. In Minnesota, 2-4 million lbs of Wild Rice is harvested each year and 1 lb yield 10.5 cups of rice. This study involves sampling surface water, surface sediment, and wild rice grains from 6 lakes on the White Earth Reservation, Fond du Lac Reservation, and 1854 Treaty Area in Minnesota. This was done in order to assess a possible toxicity risk from the consumption of Wild Rice. Finished and unfinished rice grains were analyzed, and all samples were consistent for the six lakes. Using a chronic exposure formula and the highest THg and MeHg concentrations in finished rice grains, it was determined that the toxicity in wild rice grains in Minnesota is extremely low.