Some direct measurements of atmospheric sulfur fluxes over a pine plantation

Abstract

Direct measurements of the turbulent fluxes of total atmospheric sulfur have been made over a plantation of loblolly pine in Alamance County, North Carolina, during July 1977. Fluxes of total sulfur are found to have a strong diurnal cycle, with daytime peaks of about 0.04 μg m −2 s −1 and with daytime deposition velocities typically in the range 0.5–2.0 cm s −1. At night, fluxes of sulfur appear to have been zero or directed slightly upward, out of the canopy. On occasions when no gaseous sulfur compounds were detected, the measurements indicate deposition velocities for particulate sulfur that average about 0.7 cm s −1 in daytime. Eddy fluxes of small particles with diameter near 0.07 μm also display considerable variability; in this case the net transfer was upward during most of the diurnal cycle, but strongly downward in the afternoon.