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Bromegrass (Bromus inermis) was grown under conditions of sewage effluent irrigation on undisturbed soil columns in which the 0‐ to 10‐cm layers had been treated with 10 µg Hg/g soil as 203Hg‐labeled mercuric chloride (HgCl2), phenyl mercuric acetate (PMA), and methyl mercuric chloride (MMC). Mercury concentrations in plant dry matter decreased over three successive harvests and highest values were found on MMC‐treated soils of fine texture and low organic matter content (2.0 to 0.2 µg Hg/g for first and third harvest, respectively). Exposure of the plants and soils to simulated fall conditions resulted in a small but significant increase in the Hg concentration of plant dry matter. Higher levels of Hg were found in plant stems (up to 0.88 µg Hg/g) than plant foliage (up to 0.24 µg Hg/g) at the termination of the experiment and even higher levels in the main roots (up to 42.5 µg Hg/g) and fine roots (up to 106.4 µg Hg/g) separated from the 0–10 cm soil layer. Mercury concentration of roots decreased with depth for all Hg treatments but were still 150 times greater than background levels in the MMC‐treated soils at the 40‐ to 60‐cm depth. A significant amount of all forms of applied Hg (10–32%) was lost during the experiment, presumably by volatilization. The majority of the remaining Hg in the soil was found to be strongly bound and not extractable by weak salt solutions, dilute acids, and chelates.

The adsorption of Hg by two soils, differing in chemical and physical characteristics, indicated that both organic Hg compounds (methyl mercuric chloride [MMC] and phenyl mercuric acetate [PMA]) and inorganic compounds (mercuric chloride [HgCl2]) followed the linear form of the Langmuir adsorption isotherm. The highest adsorption maxima for all Hg compounds were found for the soils which had the higher organic matter content and clay content. Adsorption maxima increased in the order MMC < PMA < HgCl2. A two‐rate effluent leaching experiment was conducted utilizing undisturbed soil cores of the same two soils and the same three Hg compounds (labeled with 203Hg) which were applied uniformly to the top 0–10 cm of each column. In contrast to the movement of other cations in the effluent and soil, even at the higher irrigation rate, none of the applied Hg was found to move below the 10‐ to 20‐cm soil layer. More MMC than HgCl2or PMA were found in the 10‐ to 20‐cm layer; however, the differences were small. The lack of movement of Hg and the high adsorption maxima was a consequence of the strong binding between Hg compounds and soil. The inability of weak chemical extractants (CaCl2, NH4OAc, DTPA, EDTA) to remove significant quantities of Hg confirmed this hyphothesis. Seven to 31% of the applied Hg was lost from the columns during the experiment presumably by volatilization.