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 rela tion 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 di scharge were highly contaminated with arsenic (up to 18 650 mug g-1 in sediments) compared with other areas. Macrophytes tended to bioconcen trate arsenic relative to sediment concentrations (up to a factor of t en), with submerged species containing much higher levels of arsenic t han 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 difference s in the ability to exclude arsenic with increasing sediment concentra tions. High environmental arsenic concentrations appeared to have nega tive effects on Typha latifolia, as suggested by decreased stand heigh t, necrosis of leaf tips and reduced micro-nutrient concentrations in root tissues of copper, manganese, and zinc. Phytotoxic symptoms in Ty pha were generally observed at sediment and water concentrations excee ding 300 mug g-1 and 400 mug l-1, respectively. The lack of relationsh ips between tissue concentrations of arsenic and environmental concent rations of phosphorus (as pore water PO4(-3), particulate total extrac table P, or As:P ratios) did not support the hypothesis that arsenic b ioavailability (as arsenate) and toxicity is related to its competitio n for uptake with phosphate.