India Goes On An Acid Trip

The next time it rains at the end of a hot summer, don't rush out to enjoy the monsoon showers. Chances are it won't be the naturally distilled water we have come to expect, but acid rain _- cloud bursts bringing down oxides of sulphur, nitrogen and carbon to cause a host of health and environmental problems.

Thanks to increasing industrialisation, India enjoys the dubious distinction of releasing the maximum pollutants in the air after China which leads the world as the most polluting country. Most of Indian energy demands are met through coal-based sources, leading to sulphur release in the air. Vehicular pollution in cities is the second major cause and disposal of wastes is the third. Total sulphur emissions in India are expected to rise from 4,400 kilotons (kt) in 1990 to 6,500 kt in 2000, 10,900 kt in 2010 and 18,500 kt in 2020, a pollution load under which Indian cities will be nothing more than large gas chambers.

 

In the atmosphere, sulphur and nitrogen oxides get converted into sulphuric and nitric acid due to a complex interaction of pressure, temperature, oxidisation of sulphur and nitrogen and wind. This then gets dissolved in rain drops as sulphate or nitrate ions and comes down along with the rain causing respiratory diseases in humans, boring holes in the protective topsoil layer, laying waste crops and diverting courses of rivers.

According to Manju Mohan and Sanjay Kumar, two researchers at the Centre for Atmospheric Sciences, Indian Institute of Technology, New Delhi, north-east India is particularly vulnerable to acidic deposition through rain due to the movement of atmospheric pollutants with predominant winter winds from the south. It is a tragedy that a region that has thick forest cover should be subject to an "acid attack" from the skies. Worse, acid rain may be destabilising the entire ecosystem of the region by degrading the land and disturbing the food chain. The successive floods in the region may be an indication of worse things to come.

The situation over India could have been worse but for several natural factors that have partially checked acid rain, say the authors of a research paper. Tropical climatic conditions reduce the atmospheric oxides load, the predominantly alkali-rich soil has an additional neutralising effect, high ambient temperature and sunlight brightness increase the efficiency of atmospheric chemical reactions which decrease acidic deposition. But this may not be enough to contain the rising pollution load due to rapid and unchecked industrialisation and the addition of vehicular load in urban and semi-urban areas.

The researchers collected rain water samples from five Indian cities _ Delhi, Calcutta, Bhopal, Lucknow and Pune _ to check the chemical composition of rainwater at various stages of the monsoon. What they found is indeed a cause for serious concern. Ions of hydrogen and carbon were a major constituent in all rainwater samples. These ions are produced by the reaction of carbonic acid with alkaline earth-bicarbonates present in the soil, dust or otherwise in the atmosphere as particulate matter. Delhi, not unexpectedly, has the highest level of hydrogen and carbon ions.

Elaborating on the effects of acid rain on earth, the researchers said it prevents essential nutrients such as potassium, calcium and magnesium from being uplifted by plants, reduces the productivity of micro-organisms in nitrogen-fixing and decomposition. In plants, the all-important photosynthesis process, which produces food and releases oxygen in the atmosphere, can be hindered. Besides, the ability of the plant to resist pest attacks can be impeded. Acid rain quickly erodes topsoil ridding the earth of nutrients needed by plants.

Acid rain can have devastating effect on aquatic life. The presence of ions of aluminium in acid rain is highly toxic to many organisms. Entire generations of fish have been found to have disappeared after acid rain water came down on lakes in the former Soviet Union. When fish die, their prey like beetles and dragonfly larvae thrive, and become pests in surrounding areas.

On humans, acidic water can have devastating effect. It liberates mercury from the soil which can affect brain development during the foetal stage. Mercury is also absorbed by various plants and animals on which humans feed and can lead to indirect mercury poisoning. Cadmium is another commonly found constituent of acid rain and can cause renal disorders and Alzheimer's and Parkinson's diseases.

The study has identified three areas in India as being most vulnerable to the ill-effects of acid rain _- Delhi, parts of south Bihar and mid Bengal. All three grossly exceed the ambient air quality requirement of the Central Pollution Control Board (30-50 milligram per cubic metres) five or six times. The prevalence of two thermal power plants and chemical industries within Delhi limits and very high concentration of motor vehicles is the main cause for the high pollution in the capital. In south Bihar and Bengal, coal mines, thermal plants and the use of coal in industries have been responsible for the high incidence of acid rain in the region. These areas are characterised by lower agricultural productivity than surrounding ones in the same agroclimatic belt but with a lower pollutant load factor. Also, the incidence of respiratory and other ailments are severe with one in 10 residents suffering from them at some point in his life.

There are new acid rain `hotspots' like the Maharashtra-Karnataka Konkan coast which is experiencing rapid industrialisation. The commissioning of the Dhabol power plant and the Konkan railway line are certain to cause a quantum jump in sulphur dioxide release. Similarly, parts of Tamil Nadu also are in the acid rain hit list due to existing and proposed power plants and rapid industrialisation.

The scientists say the acid rain factor can be controlled if India adopts pollution control technologies of which they are two kinds _ local and advanced _ available abroad. An investment if Rs 3,000 crore is needed if local technologies are to be adopted extensively and twice that if advanced technologies are to be procured. Strong political will is needed to recognise the urgency of the problem and address it from a technological perspective. Without the investment, the situation could deteriorate to a point where the concentration of acids in acid rain could increase tremendously causing burns and destroying crops on contact.

The government needs to first determine the acid rain load for different areas given the agroclimatic diversity of the country. An acid rain model that can predict the amount of pollutant-loaded rain water falling on a particular area in a given timeframe should be worked out based on which one can determine the probable damage to humans and land. Steps to stop and progressively roll back the acid rain should then be taken using the available control technologies.

Interestingly, advanced Asian countries like Japan, South Korea and Taiwan with higher industrial production than India have a much lower atmospheric pollution load, mainly because they adopt appropriate pollution control norms.

Controlling industrial pollution pays in the form of a healthier population, high agricultural production, abundant plant resources and so on. A study by the European Union has found a correlation between adoption of pollution control technology and higher industrial and human output. Unless it reforms itself quickly, balancing that equation could grow tougher for India every year.