CHEMICAL-CHANGES IN THE STEM MATRIX OF 3 TREE SPECIES EXPOSED TO FLUORIDE EMISSIONS FROM AN ALUMINUM SMELTER

The principal objective of this study was to investigate the major org anic and trace elemental composition of the stem tissues of three tree species of a mixed forest on Cornwall Island in the St. Lawrence Rive r, Ontario. This forest was exposed to atmospheric hydrogen fluoride ( HF) at levels >71 mu g F/m(3)/24 h from an aluminum smelter (Reynolds Metals Co. Ltd.) for twenty years, followed by fourteen years of reduc ed emissions (<40 mu g F/m(3)/24 h), which is still greater than the c urrent Ontario air quality criterion for HF (0.36 mu g F/m(3)/24 h). I ncrement cores were collected at breast height from white pine, red oa k, and American beech from the study woodlot on Cornwall Island and at a control site in Long Sault Provincial Park. Tree-rings were analyze d for eight elements (fluorine, aluminum, manganese, magnesium, calciu m, sodium, chlorine and potassium) and some major organic compounds (t otal extractives, lignin and holocellulose). All three species from th e study woodlot showed significant chemical compositional changes duri ng the peak pollution and post-abatement periods. There was a substant ial increase of the levels of total extractives (up to 167%), lignin ( up to 38%), fluorine, aluminum and manganese and a significant decreas e of holocellulose content (up to 17%) in the stem tissues during the period of HF exposure, compared to the pre-pollution period. In contra st, trees from the control site showed no significant change in chemic al composition in any of the three periods. Lower cellulose and higher lignin and extractives concentrations potentially makes the wood weak er and less suitable for dimension lumber and pulping.