Dryfall: An important constituent of atmospheric hydrocarbon deposition

Abstract

The character and magnitude of C 13C 33 hydrocarbons in bulk, wet and dry atmospheric deposition samples are presented. Biogenic n-alkanes were a predominant component of all samples. Urban samples with the exception of wetfall, contained primarily anthropogenic hydrocarbons with minor biogenic inputs. Hydrocarbons derived from higher plant waxes constitute the largest source input to nonurban samples. The UCM was an important constituent of bulk and dry deposition but was absent in wet deposition samples. The PAHs were present in similar concentrations in bulk and dry deposition samples collected at the urban station but were absent in nonurban and wet deposition samples. Wet deposition samples accounted for approximately one-third of the total hydrocarbon deposition of corresponding bulk deposition samples. The comparison of hydrocarbon concentrations in precipitation to ambient air samples indicates that precipitation removed only a small portion of the high molecular weight hydrocarbons from the atmosphere. The quantitative and qualitative composition of dry deposition samples appears very similar to that of bulk deposition samples supporting the proposal that dry deposition is the primary atmospheric removal mechanism for high molecular weight particulate hydrocarbons.