Sulfur
It is known from a comparison of the natural and anthropogenic fluxes
of sulfur that the total amount of sulfur entering the atmosphere has
doubled owing to human activity, but it is not known yet what the impact
will be. What are the effects of increased levels of sulfate in
precipitation? How do the effects vary? What is the role of sulfur in
upland and tropical soils? Are these soils a source or sink for trace
sulfur gases?