The influence of smelter fumes upon the chemical composition of lake waters near Sudbury, Ontario, and upon the surrounding vegetation

Analyses for sulphate, calcium, and pH have been made on surface waters from 102 lakes and ponds in the Sudbury metal-smelting district, and data are presented for 35 of these. Sulphur pollution is frequently high within about 5 miles of the three smelters, many ponds exhibiting more than three times the sulphate concentration normal for this area, and three waters more than 10 times this level. Outside about 15 miles distance the influence of smelter pollution upon sulphate concentrations in surface waters is negligible. As expected, many of the most polluted waters are strongly acid, with pH values going as low as 3.3. Sulphuric acid from air pollution has also led to increased weathering of calcium from soils and rocks, so that this ion tends to rise in concentration not only in waters above pH 6 (as expected) but also in those below pH5. Damage to terrestrial vegetation is frequently marked within about 5 miles of the smelters, while it is seldom obvious to the untrained eye beyond this distance. Severe damage occurs chiefly within about 2 miles of the smelters.