Major-ion chemistry of the Rocky Mountain snowpack, USA

During 1993-97, samples of the full depth of the Rocky Mountain snowpack we re collected at 52 sites from northern New Mexico to Montana and analyzed f or major-ion concentrations. Concentrations of acidity, sulfate, nitrate, a nd calcium increased from north to south along the mountain range. In the n orthern part of the study area, acidity was most correlated (negatively) wi th calcium. Acidity was strongly correlated (positively) with nitrate and s ulfate in the southern part and for the entire network. Acidity in the sout h exceeded the maximum acidity measured in snowpack of the Sierra Nevada an d Cascade Mountains. Principal component analysis indicates three solute as sociations we characterize as: (1) acid (acidity, sulfate, and nitrate), (2 ) soil (calcium, magnesium, and potassium), and (3) salt (sodium, chloride, and ammonium). Concentrations of acid solutes in the snowpack are similar to concentrations in nearby wetfall collectors, whereas, concentrations of soil solutes are much higher in the snowpack than in wetfall. Thus, dryfall of acid solutes during the snow season is negligible, as is gypsum from so ils. Snowpack sampling offers a cost-effective complement to sampling of we tfall in areas where wetfall is difficult to sample and where the snowpack accumulates throughout the winter. Published by Elsevier Science Ltd.