Soil, vegetation, and rainfall, have been collected in the vicinity of a nickel–copper smelter at Sudbury, Ontario. The region is a major producer of many metals, and the large areas of forest desolation in the vicinity have been ascribed to sulphur dioxide fumigations over the past 80 years. In the present study, attention has been focused on potentially toxic heavy metals. Very elevated soil levels of nickel and copper were found, with values up to 5,104 ppm Ni and 2,892 ppm Cu within 1.1 km of the smelter. The concentrations decreased with distance to 49.8 km in one direction. Surface soils were the most contaminated, and a decline through the soil profile was found. Other metals such as iron, cobalt, and silver, showed a similar pattern of distance and depth, suggestive of an airborne source. Analyses of the foliage of three plant species also showed excessive levels of nickel and copper, as well as of aluminium. The levels declined with distance from the smelter.The relative possibilities of soilversusaerial uptake are considered. The soils within 2–3 km of the smelter were markedly more acidic than those from farther away, and this was paralleled by their increased conductivity. Dustfall–rainfall collections and analyses of the soluble heavy metals indicated that a major aerial source of metals existed, and that the problem of metallic emissions is not merely one of the past. Heavy metals are persistent in soils, and the ecological consequences to date have perhaps only been masked around Sudbury by the sulphur dioxide damage, and the particular importance attached to it in the past.
Soils from the Sudbury region, Canada, which have been contaminated by the heavy metals nickel, copper, cobalt, and iron, from airborne smelter emissions, have been assayed for their toxicity to seedling growth. The extent of radicle elongation in bathing solutions of soil-water extracts has been used as a bioassay index of soil toxicity. The root growth of four species was reduced in extracts of soils which had been collected up to a distance of 49.8 km from the Coniston smelter. Inhibition was greatest in surface soils. Water extracts had metal concentrations of up to 142 ppm Ni, 59.5 ppm Cu, and 4.6 ppm Co. In addition, aluminium occurred in water extracts at 50.6 ppm at 0.8 km from the smelter, and up to 98.9 ppm somewhat farther away, even though it was not smelted in the region.All of the four metals nickel, copper, cobalt, and aluminium, were shown to be markedly inhibitory to seedling growth at concentrations below 5 ppm. In addition, all of the metals tested were concentrated markedly in the seedlings, expecially in their roots. The concentration factor was often 50- to 100-fold that of the bathing solution. Nickel appears to be the greatest single heavy-metal problem with which the vegetation has to contend. Even in the event that the major emissions of sulphur dioxide in the area be controlled, the concentrations of the toxic heavy metals nickel and copper already existing in the soils over many square kilometres present severe problems for seedling establishment and, consequently, revegetation.
Wnrrev, L. M. axo ScsNrrzr,n, M. 1978 At this stage, the FA's also were high in ash.To lower the ash, several procedures were tried:(1) dissolution in methanol and butanol (Griffith and Schnitzer 1975a);(2) stepwise pH adjustment from 2.5 to 10.5, followed by centrifugation to remove insoluble residues (Holtzclaw etal. 1976
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