Field measurements of dry deposition to spruce foliage and petri dishes in the Black Forest, F.R.G.

Dry deposition fluxes of Ca²⁺, Mg²⁺ , K⁺, Mn²⁺, Pb²⁺ and SO²⁻₄ to spruce foliage and petri dishes were measured in two high-elevation sites ( > 900 m) in the southern Black Forest, F.R.G., during 12 periods (2–7 days, each) from mid-September to mid-November, 1983, In situ extraction of deposited material from small spruce branches allowed repeated use of the same foliar collecting surfaces for a direct comparison of deposition between periods. Fluxes were corrected for leaching of internally cycled constituents using factors determined from serial extraction experiments. The ratio of flux to petri dishes vs foliage (PF">PF) was > 1.0 for Ca²⁺, Pb²⁺ and SO²⁻₄, and somewhat < 1.0 but more constant for Mg²⁺ . Temporal variations in dry deposition fluxes at an exposed site near the industrialized Rhine Valley correlated with variations in total air particulate concentrations at a nearby air quality station. Deposition rates were comparable in magnitude but different in temporal pattern at a remote site in the Black Forest interior. Fluxes at each site reached a minimum during the period of 4–9 November when a regional air inversion confined pollutants to the Rhine Valley below the study sites. High fluxes accompanied the inversion break-up.