Causes and Effects of Acidic Rain Formation

Pictorial aspect of acidic rain formation

The term acidic rain was first used by Robert Angus in 1872. Literally it means the presence of excessive acids in rain water or the fall of acids mixed with rain and snow. Nitrogen oxides and sulphur dioxide which are acidic gases dissolve in in the rain water in the atmosphere and make it acidic. Acidic rain in fact is a cocktail of mainly H2SO4 (Sulfuric acid) and HNO3 (Nitric acid) where the ratio of these two may vary depending on the relative quantities of oxides of sulphur and nitrogen emitted. H2SO4 is the major contributor (60-70 percent) to acid precipitation. HNO3 ranks second (with 30-40 percent) and HCL third.

Although the oxides sulfur and nitrogen have been recognized as the main components responsible for acid rain, their relative contributions to acid rain is still not very clear because of the highly complex nature of their transport and complexity involved in their removal from rain water. Once these oxides have fallen, along with rain water, it is difficult to remove them from the environment. These oxides may travel long distances in the atmosphere and during this journey, they may undergo several physical and chemical transformations to products which may also fall with rain. Hence, acid rain which is mainly a man made is a global ecological challenge. Normal rain water is always slight acidic because of the fact that CO2 present in the atmosphere gets dissolved in it, forming carbonic acid (H2CO3). Because of the presences of SO2 and NO2 gases as pollutants in the atmosphere, the pH (a measure of how acidic/basic water is) of the rain water is further lowered, often to as low as 2.4 and this type of precipitation of lower pH is called acidic rain.

Formation of Acidic rain

Acid rain is the one phase of acid deposition which can either be wet or dry. It is the form of snow, dew, fog, frost and mist represent the wet form of deposition while dust particles containing sulphates and nitrates, settled on earth, and constitute dry deposition. However, the wet rain is much more common. Wet acid rain every source of energy that we use be it coal, fuel wood or petroleum products have sulphur and nitrogen. These two elements, when burnt in atmospheric oxygen, they become converted into their respective oxides (SO2 and NO2) which are highly soluble in water. By anthropogenic and natural sources, oxides of sulphur and nitrogen enter the atmosphere. In case of nitrogen, following reaction, following involved under humid condition of air N2O5 invariably with vapours to form droplet of HNO3. Some HNO2 are also formed. HNO3 and HNO2 are then dropped to the earth's surface. However, HNO3 can be removed as a particulate nitrates after reaction with bases such as NH3. SO3 in humid atmosphere forms droplets of H2SO4. This HNO3 and H2SO4 formed combined with HCL (emitted from natural and man made sources) to generate precipitation which is commonly referred to as acid rain.

What aggravate acidic rains?

Extreme wind can aggravate acidic rain. The oxides of sulphur and nitrogen are swept up into the atmosphere and travel thousands of kilometers. The longer they stay in the air, the more likely they are to be oxidized into acids. For instance, a given molecules of SO2 may remain in the atmosphere up to 40 hours. While a sulphate particles may remain for three weeks. They have enough long life periods and so these molecules may be transported several kilometer from their point of release and aggravate the existence of acidic rain.

Effects of Acidic rain

Acidic rain exerts both direct and indirect effect on both organisms and materials it comes into contact with. The direct effects of rain are determined by concentration of pollutants in the air. They are mainly of local nature with a geographical extent of few kms. They decline rapidly with distance from the emission sources. They affect organisms and material and cause more harm at a distance and some thousands of kms. The dry deposition has several direct effects on environment. It attacks building materials, principally, limestone, marble, steel, nickel and other metals causing loss of millions of dollars spent in making structures like statues and buildings. When deposited in gases, it causes direct damage to plants and trees, the visible injury being gradual yellowing of leaf tissues (chlorosis).

The wet deposition has direct as well as indirect effects. It increases the acidity of lakes and rivers which is made worse inflow of acids and metals from nearby soils. Wet deposition also affects aquatic as well as territorial ecosystems. Vast tracts of forests and lakes in Europe and North America are being destroyed by acidic rain. Wet deposition can transport metals such as Al, Cd, Hg and Cr into soil water, ground water, lakes and streams, depleting the stocks of nutrients in the soil, there by causing harm to various ecosystems. Acidity kills fish, algae, bacteria and aquatic system gets collapsed into the sterility leaving a crystal clear but ultimately a dead lock. Accordingly, a number of acidic precipitation victims were identified by scholars like aquatic biota, lake ecosystem, buildings, human beings.

Acid rain effects on Aquatic Biota

Reduce fish population accompanied by decreasing the variety of species in food chain. There are 15,000 lakes with no living fish population in Sweden and 100 such lakes in the Adirondack region of USA, because of increased acidity of lakes. It create a big exposure to be unfavourable pH levels which was not appropriate for fishes reproductive process, many algae and bacteria will be killed due to acidity, disrupting the whole ecological balance, destroy tree (in west Germany 10 percent of forests perished and 18 millions acres of forests are severely affected), and actual nutrients like calcium, potassium, iron and magnesium have leched a way from soil by acids. It also destroy crops and forest reducing agricultural productivity, retarded the growth of crops like pea, beans, radish, potato, spinash, broccoli, carrots etc. Similarly, in Japan 5000sq kms cedar trees were affected by high acidic deposition.

Acidic rain effects on the ecosystem of lakes

It causes a number of complication in ponds, rivers and lakes where it accumulates as acidic snow. In summer time, rapid snow melting gives a jolt of acid water to lakes that cause the death of a number of Young fishes, algae and insects including discharging food chain. Black flies, mosquitoes, deer flies and other aquatic worms occur abundantly where fishes are eliminated. So, they appear to thrive in acid condition. Dragon fly larvae and water boatmen also flourished in acidified lakes. Moreover, the activity of bacteria and other microscopic animals is reduced in acidic water. So the dead materials and other accumulated substance lying on the bottom of lakes are rapidly decomposed. Thus essential nutrients as nitrogen and phosphorus stay locked up in plant and animal remains. Biomass production is reduced and fish population declines. Aquatic plants like broad leaved trees and weeds do not grow in acidic water.

Acid rain effects on buildings:

Acid rain causes extensive damage on building and structural materials of marble, limestone and slate. Limestone could be attacked rapidly and attacks of marble termed as stone leprosy. In Greece and Italy, invaluable stone have been partially dissolved by acid rain. Further, as a result, ever year, 1450 millions of dollars are lost around the world. For instance Taj Mahal in Arga and British Parliaments Building have also suffered damage of H2SO4. Due to acidity, levels of heavy metals like Al, Mn, Pb, Cd, Cr, and Cu in water increased beyond the safe limits which indirectly affects the buildings. Traces of radio active elements present in radioactive rain severely damage buildings.

Effects of Acid rain on human beings

Acidic rain has been found to be very dangerous to the living organisms as it can destroy life. Acidity can play havoc with nervous system, respiratory system and digestive system by making the person vulnerable to neurological diseases. This happens because these acids produce highly toxic compounds which contaminate the portable water and enter man's body. It also contain air pollutants contribute to a variety of safety hazards, associated with reduced visibility due to smog. Here I tried to familiarize you some core points on how acidic rain is formed, aggravated and also affects the world and living things.

Eventually, as a journalist I would like to applaud Japan's government measure to protect acidic rain effects. [Because] currently, acidic rain measuring kit are available. As to my source, when a chemical is placed in small plastic container and acid rain falls on it, the colour changes and hence the acidity content of the rain can be read. As it had been in Northern Europe and Northern America, it has become significantly noticeable in Japan. Similarly, Japan's Environment Agency has established a national monitoring network and records from 1994 show that pH values in rain fall in 28 place averaged 4.8 and acidic rain fall reported in both urban and rural areas ranging between pH 4.5 to 5.8 .

Therefore, I do have one question for all of us. Are we strong enough to protect such kind of acidic rain effects? What have we been doing to protect our renewable and non-renewable environmental resources? Specially, what our stakeholders, professionals, expertise, researchers, authoritative bodies as well as national and international private sector actors have been doing in their respective roles to withstand the effects of acidic rain? Have the aforementioned effects and signs of acidic rain been observed in your country yet?

Actually, a number of horrible events have been occurring around the world because of acidic rain. For instance, drought, flood starvation and the likes are the direct and indirect results or effects of acidic rain fall. Therefore, we have to be united and get hand to hand so as to protect this as well as the next generation from negative effects of acidic rain.