Science behind Acid Rain: Analysis of Its Impacts and Advantages on Life and Heritage Structures

Abstract

INTRODUCTION Acid rain is a major problem facing the environment today. It is formed through both natural and anthropogenic sources. Industrial emissions are anthropogenic sources, and a volcano eruption is an example of a natural source. One of the most direct effects of acid rain is on aquatic ecosystems. Acid rain is the term given to increased acidity of rain due to the effects of gases (from industrial and natural processes) which dissolve in rainwater to form various acids. Acid rain forms when certain atmospheric gases (primarily carbon dioxide, sulphur dioxide, and nitrogen oxides) come in contact with water in the atmosphere or on the ground and are chemically converted to acidic substances. Oxidants play a major role in several of these acid-forming processes. Carbon dioxide dissolved in rain is converted to a weak acid (carbonic acid). Other gases, primarily oxides of sulphur and nitrogen, are converted to strong acids (sulphuric and nitric acids). Although rain is naturally slightly acidic because of carbon dioxide, natural emissions of sulphur and nitrogen oxides, and certain organic acids, human activities can make it much more acidic. Occasional pH readings of well below 2.4 (the acidity of vinegar) have been reported in industrialized areas. The principal natural phenomena that contribute acid-producing gases to the atmosphere are emissions from volcanoes and from biological processes that occur on the land, in wetlands, and in the oceans. The effects of acidic deposits have been detected in glacial ice thousands of years old in remote parts of the globe. Principal human sources are industrial and power-generating plants and transportation vehicles. The gases may be carried hundreds of miles in the atmosphere before they are converted to acids and deposited. Since the industrial revolution, emissions of sulphur and nitrogen oxides to the atmosphere have increased. Industrial and energy-generating facilities that burn fossil fuels, primarily coal, are the principal sources of increased sulphur oxides. These sources, plus the transportation sector, are the major originators of increased nitrogen oxides. The problem of acid rain not only has increased with population and industrial growth, it has become more widespread. The use of tall smokestacks to reduce local pollution has contributed to the spread of acid rain by releasing gases into regional atmospheric circulation. On the surface, the argument of caution is used, that steps should not be taken unless backed up by a high degree of technological proof, such that doubt is no longer present, or at least that the doubt is not large enough to outweigh the cost of action. Beneath this scientific, logical, ordered sheen however is the self centered interests of an industry which does not want to change the status quo, one of predictability and security, required ultimately for economic growth and shareholder contentedness. Fundamental to the argument against providing flue gas emission reduction technology is the high cost associated with this, compounded by lack of knowledge on the cause – pathway – effect linkage. The acid rain scenario is repeated and magnified in the case of CO2 emissions and the suspected anthropogenically induced enhanced greenhouse effect.