ABSTRACT
This chapter addresses three issues which are primarily felt to be of concern at the regional level: acid deposition, heavy metals and tropospheric ozone. The first two of these represent pollutants whose major anthropogenic source is fossil fuel combustion, while ozone is a product of photochemistry. The direct deposition of gases and particles onto a surface is known as dry deposition. A significant element of acid deposition was a transboundary air pollution problem. In common with the precursors of acid deposition, heavy metals such as arsenic, lead and mercury, may come from a range of natural and anthropogenic sources. Tropospheric ozone is largely produced by photochemical reactions involving oxides of nitrogen (NOx) and volatile organic compounds (VOCs). Carbon monoxide (CO) and methane (CH4) also play an important role. The timescales for the chemical production of ozone and the transport distances of the pollutants involved make tropospheric ozone a regional and indeed hemispheric problem.
