The Uptake of 203Hg‐Labeled Mercury Compounds by Bromegrass from Irrigated Undisturbed Soil Columns

Abstract

AbstractBromegrass (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.