Precipitation was collected during 1984 and 1985 at two sites in southeastern Arizona within 100 km of two copper smelters. The precipitation-depth-weighted mean pH was 4. 63 and wet sulfate deposition was 8. 9 kg ha** minus **1 over a 13-month period. High acidity and sulfate concentration occurred when upper-level winds were from the directions of the smelters. A smelter 'fingerprint', based on antimony, arsenic, cadmium, copper, lead and zinc, was identified, and used to evaluate the smelter contribution to precipitation sulfate on an annually-averaged basis. The variations in the relative proportions of these trace metals were too large to permit application of the method to individual precipitation events.
