Effects of smelter pollutants on forest leaf litter decomposition near a nickel–copper smelter at Sudbury, Ontario

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Abstract
Forest soils and litter in the vicinity of a large Ni-Cu smelter at Sudbury, Ontario are contaminated with a variety of heavy metals. Studies were conducted to determine if forest litter decomposition processes were affected. The effects of Ni and Cu on the decomposition of forest litter were investigated using a variety of techniques in which contaminated and control sites were compared. At contaminated sites an increase in litter standing crop was found. This was related to lower rates of litter decomposition at these sites, as evidenced by reduced rates of breakdown of litter in mesh bags, compared with uncontaminated sites. Lower rates of CO2 flux and acid phosphatase activity were also found at the contaminated sites. In a laboratory experiment, the addition of Cu and (or) Ni to a homogenate of leaf litter depressed the rate of dry weight loss and CO2 flux. Negative effects commenced at metal concentrations comparable to those observed in litter at contaminated sites in the field.