Wet deposition estimates from long-term bulk and event wet-only samples of incident precipitation and throughfall

This report describes a 2-yr study comparing two sampling systems that are used to measure major ionic constituents in incident precipitation and canopy throughfall: long-term bulk sampling vs. event-based, wet-only sampling. Major deviations in chemical concentrations (SO4^2-, NO3^-, K⁺, Ca²⁺, and H⁺) were documented between the two sampling systems, deviations that were ion-specific in both incident precipitation and throughfall. Differences in chemical concentrations between the two sampling systems were greater (i) during the growing than during the dormant seasons, and (ii) for incident precipitation (collected in the open) than for throughfall under chestnut oak forest (Quercus prinus L.) canopies. Nutrient-cycling processes in forests may be misinterpreted if flux data are based solely on long-term bulk samplers of incident precipitation and canopy throughfall. For example, comparison of bulk and wet-only throughfall solutions suggests that when bulk samplers collect throughfall under hardwood canopies, the ability of hardwood canopies to increase pH of low pH precipitation may be overestimated.

Duke Scholars

Author Daniel D. Richter Earth and Climate Sciences