Estimation of Deposition Velocities of Sulfur and Nitrogen to a Japanese Cedar Forest by Throughfall Method

Abstract

This study presents a multiple regression analysis to estimate dry deposition velocities of gases and particles to a forest using the net throughf all flux (throughf all + stemflow - precipitation) as the dependent variable and atmospheric concentrations of gases and aerosols as independent variables. The advantage of this method, for chemical species where canopy leaching and uptake are negligible, is that the contributions of dry deposition to net throughfall fluxes and deposition velocities of various kinds of gases and particles can be estimated simultaneously only from a data set of net throughfall fluxes and atmospheric concentrations. This regression analysis was applied to the one-year data set observed at a Japanese cedar (Cryptomeria japonica) forest located in Isehara City, Kanagawa Prefecture. Annual mean deposition velocities of SO₂, particulate SO₄^2-, HNO₃ and particulate NO₃^- were estimated at 0.50 cm/s, 0.057 cm/s, 3.5 cm/s, and 1.3 cm/s, respectively. These values agreed fairly well with those estimated by several different methods in the literature.