ARSENIC BIOACCUMULATION AND TOXICITY IN AQUATIC MACROPHYTES EXPOSED TO GOLD-MINE EFFLUENT - RELATIONSHIPS WITH ENVIRONMENTAL PARTITIONING, METAL UPTAKE AND NUTRIENTS

Arsenic concentrations in freshwater macrophytes were examined in relation to arsenic loadings in sediments (solid phase and pore water) and surface waters for a group of lakes contaminated by the discharge of mine tailings near Yellowknife, N.W.T. Lakes closest to the current discharge were highly contaminated with arsenic (up to 18 650 mug g-1 in sediments) compared with other areas. Macrophytes tended to bioconcentrate arsenic relative to sediment concentrations (up to a factor of ten), with submerged species containing much higher levels of arsenic than emergents. Differences in levels between the most common submerged (Potamogeton pectinatus L.) and emergent species (Typha latifolia L.) were attributed to differences in growth form and possible differences in the ability to exclude arsenic with increasing sediment concentrations. High environmental arsenic concentrations appeared to have negative effects on Typha latifolia, as suggested by decreased stand height, necrosis of leaf tips and reduced micro-nutrient concentrations in root tissues of copper, manganese, and zinc. Phytotoxic symptoms in Typha were generally observed at sediment and water concentrations exceeding 300 mug g-1 and 400 mug l-1, respectively. The lack of relationships between tissue concentrations of arsenic and environmental concentrations of phosphorus (as pore water PO4(-3), particulate total extractable P, or As:P ratios) did not support the hypothesis that arsenic bioavailability (as arsenate) and toxicity is related to its competition for uptake with phosphate.