Stability of methylmercury and inorganic mercury in aquatic plants (Elodea densa)

Abstract

Elodea densa plants containing either methylmercury or inorganic mercury-203 were transferred to a flowing water system along with untreated plants for a period of 6 months. Although little or no radioactivity was measurable in the water throughout the experimental period, untreated plants accumulated some methylmercury (MMC) and to a lesser extent inorganic mercury (MC) within the 1st month. Treated plants lost more MC than MMC within the 1st month. The two species of mercury move in opposite directions within the plant with time: MMC moves toward young tissue whereas MC moves toward older tissue. Methylmercury remains stable in younger plant tissues almost indefinitely, but converts partly to inorganic forms in old and decomposed tissue. Conversion of inorganic mercury to methylmercury was not detected.