Only a few studies have investigated foliar air-surface exchange associated with wetland plants and none have investigated this exchange in an experimental setting as a function of different soil and water mercury (Hg) exposure concentrations or monitored foliar Hg concentrations. In this study, foliar total Hg (THg) and methyl Hg (MeHg) concentrations and foliar Hg flux were investigated using Typha latifolia growing within controlled mesocosms. Exposure scenarios included combinations of two soil exposure Hg concentrations (0.03–0.1 and 0.38–0.44 µg g⁻¹), and two water exposure Hg concentrations (4–8 and 40–140 ng L⁻¹). Soil and water Hg concentrations were not correlated with foliar total Hg concentrations or foliar Hg flux. Foliar Hg fluxes measured with a gas exchange chamber were low, and atmospheric deposition to foliage was the dominant flux for all exposures, except for those plants growing in the low Hg in water and soil scenario. Based on data developed, it is suggested that Hg concentrations in foliage of Typha latifolia growing in media contaminated with Hg from historic mine waste were influenced primarily by assimilation of Hg from the atmosphere and not contaminated by water or sediment. In contrast, foliar MeHg concentrations followed a temporal pattern that was similar to observed changes in water MeHg concentrations. This indicated that MeHg in foliage could have been derived from the rooting media and was assimilated by different processes than THg in leaves.