Atmospheric balance of sulphur above an equatorial forest

Abstract

The atmospheric sulphur balance over the humid tropical forest of the Ivory Coast is studied over a 1-year period. A box model limited by the monsoon layer between the coast of the Gulf of Guinea and the savannah is used. The height of the box is between 1 and 3 km. its length 120 km, and its width 0.001 km. The sulphur compounds considered are gaseous H₂S and SO₂ and particulate SO₄^- Chemical criteria are used to differentiate the SO₄^- of atmospheric. oceanic. soil-derived and plant origins. The sulphur compounds are measured in the air and in the rain-water at 2 stations, one at the box entry (Adiopodoume) and the second at the exit (Lamto). The sulphur balance of the box (inflow minus outflow) indicates that the mean annual emission by the soils of the forests is 1.5 g S m^-1 yr^-1. This emission is modulated by the rainfall. It is shown that the mean emission of the wet season is 6 times that of the dry season. If such a sulphur emission takes place in all other humid tropical forests, 25 x 10⁶ metric tons of sulphur per year would be injected into the atmosphere, about 1/4 of the present anthropogenic emissions. The tropical forests would then be one of the most important natural sources of atmospheric sulphur. DOI: 10.1111/j.1600-0889.1983.tb00015.x