Modeling of Throughfall Chemistry and Indirect Measurement of Dry Deposition

Abstract

Precipitation over a forested watershed is altered by interaction with plant surfaces which act as a filter for airborne gases and particles. This results in a major transfer to the forest floor of materials captured, washed, and leached from the forest canopy. Sequential samples of wetfall and sequential samples of throughfall under deciduous and coniferous trees were collected and chemically analyzed for major anions and cations. A simple washoff, mixing model based on leaf area index was used to simulate throughfall chemistry and to decouple foliar exudation from dry deposition. Model results gave excellent predictions of the measured sequential throughfall using estimated values of dry deposition. The model can also be used to calculate dry deposition, if the sequential throughfall data and wetfall data are used as input variables.