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.

After the completion of a highway construction project in Great Smoky Mountains NationalPark in 1963, a fish kill was noted in a small stream draining an area of roadbed fill. After 10 years, the stream remained devoid of fish for at least 8 km downstream from the fill. The downstream water had a pH of 4.5 to 5.9; upstream from the fill the pH was 6.5 to 7.0. The rock material in the fill contains iron sulfide minerals. Other streams in the area flowing on the sulfide-rich rocks also showed low pH values. Survivability tests and stream surveys showed that brook trout cannot tolerate conditions in the stream below the road fill or in a stream flowing over natural outcrops of the same rock used in construction of the road fill. Native salamanders were also adversely affected downstream from the road fill. Chemical analyses of stream water and leaching tests indicated that lowered pH and increased sulfate and metals concentrations derived from the leaching of the sulfide-rich rocks were responsible for the trout and salamander mortalities. A kill of native brook trout (Salvelinus/ontinalis) occurred in 1963 in a small stream (Beech Flats Creek) draining a watershed near the crest of the Great Smoky Mountains in Great Smoky Mountains National Park, North Carolina. The kill was coincident with a construction project in which a new road fill and culvert were built across the stream valley at an elevation of about 1500 m, near Newfound Gap. Brook trout were eliminated from the main stream for at least 8 km below the construction area, but fish in tributaries of the stream were unaffected. A dense whitish to yellowish precipitate coated stream bed rocks for at least 2 km downstream from the road fill.It was assumed that the kill was related to the construction work, probably due to a toxic substance that would be washed away or de-

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We investigated both total and methylmercury accumulation in fish and invertebrates in the North Fork of the Holston River below a currently inactive chloralkali plant (i) to quantify the extent of contamination, (ii) to determine what proportion of the variance in mercury concentration in fish can be explained by mercury concentration in water, sediment, benthic invertebrates, and (iii) to determine what proportion of mercury concentration in benthic invertebrates can be explained by mercury concentration in water and sediment. Fish species [rock bass (Ambloplites rupestris) and hog sucker (Hypentelium nigricans)] and benthic invertebrates were collected from stations above and below the plant, and axial muscle (fish) or whole animal (invertebrates) was analyzed for total mercury by flameless atomic absorption and for methylmercury by gas chromatography. The relation of total mercury concentration to fish weight and factors affecting mercury concentration in fish and invertebrates were examined through regression analysis. Total mercury concentration in fish and benthic invertebrates decreased with distance below the plant. Significant linear regressions of total mercury concentration on fish weight were observed for some, but not all, samples examined. Mercury in the methyl form comprised 91.7% of total mercury in fish analyzed, while approximately 50% of the mercury in invertebrates was methylmercury. Multiple regression analysis indicated 96.4% of the variance in total mercury concentration in rock bass and 80.5% in hog suckers was accounted for by mercury in water, sediment, and benthic invertebrates. Independent variables accounted for 97.4% of the variance in total mercury concentration in benthic invertebrates. The potential implication of these results for environmental monitoring programs is discussed.