ation exchange of calcium, magnesium, and other metals found in many soils takes the place of the acid's hydrogen ions. The source of the metal ions is rock weathering: the dissolving of minerals by precipitation and groundwater containing dissolved carbon dioxide, which gives the positive metal ions with anions of bicarbonate (HCO3 -). Then, when sulfuric acid is added the sulfate (SO4 2-) of the acid can displace calcium and magnesium ions, hydrogen ions responsible for acidity are left behind. The effectiveness of this natural buffer is dependent on the geology of the land.If air pollution, and specifically acid rain, plays a part in forest decline, it probably does so less as a lethal agent than as a stress. Acid and other pollutants could add to the high level of abiotic stresses, including thin soil, low temperatures, and desiccating winds. Meaning that the actual cause of death for the trees would not be acid rain itself but acid rain may just be the next contributing stress that put the tree over the edge. What to do about reducing nitric and sulfuric emissions requires going straight to the source of the problem. Many coal-burning power plants have no system of attempted emission purification. There are many new ideas of how to do this, but perhaps the most promising is flue-gas desulfurization (FGD). In which wet limestone is sprayed into the plants hot exhaust where it can absorb and lock up to 90% of sulfur dioxide. Other methods of coal cleansing are being experimented with in an attempt to reduce the formation of oxides of nitrogen. Retrofitting plants with these new techniques could be a solution to further damage to the environment. The drawbacks to all reform in this field and others similar to it are the slow processes, which everything must go through to gain approval and widespread acceptance and trust. But one thing is for sure, the need for human intervention of the destructive way we have treated our environment ...
