Atmospheric concentrations and the deposition velocity to snow of nitric acid,sulfur dioxide and various particulate species

A study of deposition velocities to snow was conducted during the 1982–1983 and 1983–1984 winters at the University of Michigan Biological Station in northern Michigan. Weekly measurements were made of dry deposition rates to snow and the atmospheric concentrations of the depositing species. SO₂, with an average concentration of 2.2 ppb, was the dominant atmospheric sulfur containing species. NO₂, with an average concentration of 1.8 ppb, was the dominant atmospheric nitrogenous species. NO⁻₃ deposition was due primarily to HNO₃, which averaged 0.2 ppb. The HNO₃ deposition velocity averaged 1.4cm s⁻¹. The SO₂ deposition velocity varied with temperature, averaging 0.15 cm s⁻¹ for samples with appreciable exposure time above − 3°C, and 0.06 cm s⁻¹ for samples which remained below an ambient temperature of −3°C. Deposition velocities of Ca²⁺, Mg²⁺ , Na⁺, K⁺ and NH⁺₄ were 2.1, 1.5, 0.44, 0.51 and 0.10cm s⁻¹, respectively. The mass median diameters of these species were 4.4, 2.7, 1.8, 0.9 and 0.46 μm, respectively.