PERFORMANCE-CHARACTERISTICS OF AN AUTOMATED WET DEPOSITION COLLECTOR AND POSSIBLE EFFECT ON COMPUTED ANNUAL DEPOSITION

Performance characteristics of what is believed to be a typical automated wet deposition collector were examined. For properly functioning collectors, the primary characteristic affecting wet deposition collection efficiency was found to be precipitation rate. Low precipitation rates resulted in the early precipitation not being collected; often at very low, but typical, rates no precipitation was collected. This results in underreporting of both precipitation amounts (if raingage data are not used) and wet deposition, even if corrections to deposition are made using raingage data. This is true because the early precipitation contains the largest solute concentrations. A precipitation scavenging model was used to estimate the amount df wet deposition uncollected for a wide range of precipitation rates and amounts. Correction factors that could be applied to published data for semi-arid sites similar to those in Colorado were developed. The most probable, but conservative, estimate of corrected wet deposition was found to be: true wet deposition = 1.10 to 1.25 (measured wet deposition).