USE OF EPIPHYTE PLANTS AS BIOMONITORS TO MAP ATMOSPHERIC MERCURY IN AGOLD TRADE CENTER CITY, AMAZON, BRAZIL

Evaluation of Hg in urban air is a quite complex and expensive task si nce conventional sampling systems are fragile and need special attenti on if long-term sampling is needed. Tillandsia usneoides, a Bromeliace a, is an epiphyte that captures all its nutrients from the atmosphere, and concomitantly accumulates heavy metals, among them mercury. Its m orphology, with millimetric dimensions of the leaves and no roots, mak es it ideal for handling and preparation of transplanting systems and due to its high relation between surface area and mass, has a high eff iciency for Hg accumulation. One hundred systems of two baskets each w ith T. usneoides were distributed through Alta Floresta city-MT and re covered after an exposure of 15 and 45 days during the dry season (Aug ust-September, 1995) and also repeated during the rainy season (Februa ry-March, 1996). Each compartment (basket) contained 5 g of plants pre viously collected in a clean area. Only the younger parts were selecte d for transplantation experiments. Systems were hung at 2-20 m height in open areas, close to and in the surroundings of the gold shops as w ell as in control areas. Relative occupational exposure was also evalu ated with systems installed inside gold dealer shops. Concentrations o f Hg in the exposed plants were remarkably high in the shops, reaching values up to 26 ppm (parts per million) or 300 times higher than in t he control plants. (C) 1998 Elsevier Science B.V.