Surface soils collected near the Almadén, Spain, mercury mine reflected increasing concentrations of mercury (Hg) with proximity to the mine due to weathered mineral deposits and to atmospheric deposition of Hg from the smelter. Extractions with NaHCO3 or NH4OAc removed small amounts of Hg from both control (20 km from the mine; total Hg = 2.3 µg/g) and mine site soils (1 km; total Hg = 97 µg/g). Density gradient centrifugation indicated a significant fraction of the Hg to be associated with a high‐density mineral fraction, presumably cinnabar. Accumulation of Hg by alfalfa suggested a dual mechanism of uptake; roots accumulated Hg in proportion to the soil levels, while aerial plant material absorbed Hg vapor directly from the atmosphere. Soil fertilization with and without liming significantly increased total Hg uptake, largely due to plant growth stimulation. Liming itself had no significant effect. The rate of volatilization of elemental Hg from both soils (∼0.13 and 0.33 µg/m2 per hour at 25°C, for control and mine site, respectively) exceeded reported background emission rates by factors of 4 to 10, increasing with surface temperature and Hg content and decreasing with increased plant cover.

Comparisons were made of two in situ extractors for collection of soil water samples: Amicon hollow fibers and porous ceramic cup lysimeters. Intact soil cores removed from a fescue pasture were fitted with lysimeters and fibers at 10 and 20 cm depth. Cores were leached by adding increments of water in excess of field capacity weekly. After drainage, soil solutions were extracted using lysimeters and fibers. Concentrations of Ca and Mg in soil solutions were greater at 10‐cm than at 20‐cm soil depths. Neither extractor altered the concentrations of Ca, Mg, or PO4‐P during collection.These studies suggest that lysimeters and hollow fibers are viable devices for extracting of soil water samples. Porous ceramic cup lysimeters are preferable for field plots, while hollow fibers are advantageous for intact soil cores. A major advantage of the hollow fiber technique is the small soil displacement required for installation.

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Grassland field plots were compared to two sizes of excised microcosms (15 and 30 cm diameter) and 30-cm diameter homogenized microcosms to assess the effects of As on soil-plant nutrient dynamics. The goal of this experiment was to determine the feasibility of using microcosms for screening chemicals which are potentially toxic to terrestrial ecosystems. All experimental units were treated with As, at rates of 0, 0.5, and 5.0 mg cm -2, by superficial application of dissolved Na2AsO 4. Calcium, PO4-P , NO3-N , dissolved organic carbon (DOC), and NH4-N were determined in soil leachate and soil extracts. Greater loss of PO4-P, NO3-N, NH4-N , and DOC occurred via soil leachate from microcosms treated with the greatest level of As relative to untreated microcosms. Field plots were unaffected by As treatment. Excised microcosms were found to be more representative of field plots in reflecting microbial dynamics than were homogenized microcosms. Thus excised microcosms were recommended for testing potentially hazardous chemicals.

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