5.14.4. Impact Of Acid Rain

(a) Soil

♤ The exchange between hydrogen ions and the nutrient cations like potassium and magnesium in the soil cause leaching of the nutrients, making the soil infertile.

♤ This is accompanied by a decrease in the respiration of soil organisms.

♤ An increase in ammonia in the soil due to a decrease in other nutrients decreases the rate of decomposition.

♤ The nitrate level of the soil is also found to decrease.

♤ The impact of acid rain on soil is less in India; because Indian soils are mostly alkaline, with good buffering ability.

(b) Vegetation

Acid rains affect trees and undergrowth in forest in several ways, causing reduced growth or abnormal growth:

♤ The typical growth-decreasing symptoms are:

♤ Discoloration and loss of foliar biomass

♤ Loss of feeder-root biomass, especially in conifers

♤ Premature senescence (aging) of older needles in conifers

♤ Increase in susceptibility of damage to secondary root and foliar pathogens

♤ Death of herbaceous vegetation beneath affected trees

♤ Prodigious production of lichens on affected trees.

♤ Death of affected trees.

(c) Micro organisms

♤ pH determines the proliferation of any microbial species in a particular environment and the rate at which it can produce.

♤ The optimum pH of most bacteria and protozoa is near neutrality; most fungi prefer an acidic environment, most blue-green bacteria prefer an alkaline environment.

♤ So after a long run of acid rain, microbial species in the soil and water shift from bacteria-bound to fungi- bound and cause an imbalance in the microflora.

♤ This causes a delay in the decomposition of soil organic material, and an increase in fungal disease in aquatic life and forests.

(d) Wild life

The effects of acid rain on wild life are not very obvious and are therefore, difficult to document. Nevertheless, several direct and indirect effects of acid rain on the productivity and survival of wildlife populations have been reported.

♤ Acid rain can directly affect the eggs and tadpoles of frogs and salamanders that breed in small forest ponds.

♤ It has been postulated that acid rain can indirectly affect wildlife by allowing metals bound on soils and sediments to be released into the aquatic environment, where toxic substances may be ingested by animals, like birds, that feed in such an environment.

♤ Other indirect effects of acid rain on wildlife are loss or alteration of food and habitat resources.

(e) Humans

Acid rain affects human health is a number of ways.

♤ The obvious ones are bad smells, reduced visibility; irritation of the skin, eyes and the respiratory tract.

♤ Some direct effects include chronic bronchitis, pulmonary emphysema and cancer.

♤ Some indirect effects include food poisoning vis a vis drinking water and food.

♤ An increase in the levels of toxic heavy-metals like manganese, copper, cadmium and aluminium also contribute to the detrimental effects on human health.

Do you know?

♤ Bonsai—i.e., tailored or human-made miniature or dwarfed living trees that have been prevented from reaching their normal size—are grown in pots and kept in greenhouses, drawing rooms, etc. This technique was first perfected by the Japanese.

♤ Bamboos are trees without a main trunk but with a cluster of culms arising from the underground rhizome. These culms are unbranched, with distinct nodes and internodes that give them a jointed appearance.

♤ Trees reduce oxides of carbon in the air, can also fix atmospheric nitrogen, disintegrate waste and act as sinks of pollution

♤ Sometimes seeds of a plant are formed without fertilization. This phenomenon is called “agamospermy,” a kind of parthenogenesis. A fruit that matures without seed formation is called “parthe-nocarpic fruit.”

♤ Beverage plants are those plants which yield beverages or drinks—nonalcoholic or alcoholic—that are palatable and refreshing. Nonalcoholic beverages usually contain caffeine, an alkaloid, which has stimulating and refreshing qualities. Alcoholic beverages are those that contain one or more hydroxyl (-

OH) groups; e.g., ethanol

(f) Acid rain damage on Materials

(g) Socio-economic impacts of acid rain:

The adverse impact of acid rain on farming and fishing leads to the deterioration of life quality indices like GNP and per capita income, especially in the predominantly agricultural and developing countries like India