Atmospheric deposition ecosystem health

The impact of the emission cuts is beginning to be noticed, although more with respect to deposition than ecosystem recovery. The U.S. Environmental Protection Agency soon reported declines in wet sulphate deposition in the order of 10 to 25% across the eastern United States. There are also possible improvements with respect to dry deposition of sulphates, fine particulate matter concentrations, and visibility. Aquatic and terrestrial ecosystems respond slowly, and it is not surprising that evidence of ecosystem improvements would trail behind trends in reduced atmospheric transport and deposition. The EPA, while modest in its assessment of the environmental benefits to be accrued from reduced acidification, has been rather bullish about the investment in human health benefits represented by acid rain controls. It expects SO emission cuts to reduce American health costs by 10 billion annually, through reduced morbidity and mortality, and these savings are projected to rise to 40 billion annually by 2010 (EPA 1995). 

Once critical load estimates are available it may be of interest to produce critical load maps. It is possible that such maps will be particularly useful in comparison with rates of acid deposition, in order to see the balance between the two and also where most effort is required to limit and control depositions so that ecosystems (and eventually buildings and structures, and human health) can be protected. In fact, as already indicated, such activities may form the basis of linking fuel use and other acid emitting processes, S and N emissions, atmospheric transport and deposition to cost-effective abatement procedures, in a cost-optimized way, to produce coordinated abatement strategies. 

Norton, S.A. (1980). Geologic factors controUmg the sensitivity of aquatic ecosystems to acidic precipitation. In Atmospheric Sulphur Deposition ECivtronmental Impact and Health Effects, pp. 539-53. Ann Arbor, Michigan. 

---