A pollutant is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource A pollutant may cause long- or short-term damage by changing the growth rate of plant or animal species, or by interfering with humarn amenities, comfort, health, or property values. Some pollutants are biodegradable and therefore will not persist in the environment in the long term. However, the degradation products of some pollutants are themselves polluting such as the products DDE (Dichlorodiphenyldichloroethylene) and DDD (Dichlorodiphenyldichloroethane) produced from degradation of DDT (Dichlorodiphenyltrichloroethane)
Pollutant may be defined as "constituent in the wrong amount at the wrong place or at the wrong time." According to the Indian Environment (Protection) Act, 1986, "A pollutant has been defined as any solid, liquid or gaseous substance present in such concentration as may be or tend to be injurious to the environment"
Commonly, the term pollutant is applied to non-living , man-made substances and other nuisances and it refers to their being in excess in a particular location. For exam-ple, nitrogen, phosphorous and potassium are extensively used in agriculture to increase crop yield but sometimes, these in higher concentration cause pollution in lakes and rivers promoting algal growth. This adverse effect of pollution is more severe when the pollutants are man-made rather than natural preparation. In short, the unserviceable or residues of things which the humanity manufactures, uses and throws away, can also be regarded as pollutants.
Classification of Pollutants: The classification of pollutants is done from different points of view: (i) Depending upon their existence in nature pollutants are of two types, namely quantitative and qualitative pollutants. (a) Quantitative Pollutants: These are those substances normally occurring in the environment, who acquire the status of a pollutant when their con-centration gets increased due to the unmindful activities of man. For exam-ple, carbon dioxide, if present in the atmosphere in concentration greater than normal due to automobiles and industries, causes measurable effects on humans, animals, plants or property, then it is classified as a quantita-tive pollutant.
(b) Qualitative Pollutant These are those substances which do not normally occur in nature but are added by man, for example, insecticides
(i) Depending upon the form in which they persist after being released into the environment, the pollutants are categorized into two types, namely pri- mary and secondary pollutants (a) Primary Pollutants: These are those which are emitted directly from the source and persist in the form in which they were added to the environ-ment. Typical examples of pollutants included under this category are ash, smoke, fumes, dust, nitric oxide, sulphur dioxide, hydrocarbons etc.
Primary Pollutants CO CO2 SO2 NO NO2 Most hydrocarbons Most suspended particles Secondary Pollutants SO3 HNO HSO H202 O PANs Most NOj and so salts Sources Natural Stationary Mobile
(b) Secondary Pollutants: These are those which are formed from the pri-mary pollutants by chemical interaction with some constituent present in the atmosphere. Examples are: Sulphur trioxide, nitrogen dioxide, alde- hydes, ketones, ozone etc. Nitrogen oxides and hydrocarbons are two primary pollutants released from automobiles but in the presence of sunlight, they react to form peroxyacyl ni-trate (PAN) and ozone, two secondary s from which they are derived. This phenomenon of in-creased toxicity by chemical interaction among the pollutants is known as Synergism.
Primary Pollutant ment in the form they are produced. 2. They belong to various categories like particulate, aerosol, reduced, oxidized 3. They are less toxic. 4. They do not show synergism 5. Primary pollutants persist in the form they are released in the environment.
Secondary Pollutants: 1. The pollutants develop as a result of interaction of primary pollutants and environmental constituents. 2. They are generally oxidizing. 3. They are more toxic 4. Secondary pollutants show synergism. 5. They are modified products
Degradable pollutants or Bio-degradable Pollutants (Odum 1971): These are natural organic substances which can be decomposed, removed or consumed and thus, reduced to acceptable levels either by natural processes like biological or microbial action or by some engineered systems, like sewage treat-ment plants.
(ii) Slowly degradable or persistent pollutant: The degra-dation of these pollutants is a very slower process. It seems as if the amount of pollutant remains unchanged with time. For example, degradation of synthetic com-pounds and radio-active elements like lodine 137, Stron-tium 90 or Plutonium 239 takes a longer period of time.
Such non-degradable pollutants accumulate and are biologically magnified as they move in the biogeochemical cycle and along food chains in the ecosystem. For example, DDT, when washed from the ground goes to the streams where it is absorbed by the phytoplankton's which are eaten by the fishes So, the initial dose of DDT which was harmless in the phytoplankton becomes very harmful as it accumulates in the fish day by day, with the result that large populations offish die or become sterile and same is the case with the birds feeding on such fishes. This phenomenon is known as bio-magnification or biological magnification.
An assesses may get income from different sources, eg:- salaries-house property income-profits and gains of business or profession capital gains income from other sources like interest on securities, lottery winnings, races etc. Income from each of these sources calculated first to find out the gross total income, and then permissible deduction allowed arriving in total income according to sec 80 c to 80 u. Every person whose taxable income in the previous year exceeds the minimum taxable limit is liable to pay income tax during the current financial year at the rates applicable to the current financial year
ASSESSMENT YEAR SEC 2(9) Assessment year means the period of 12 months commencing on the first day of April every year and ending on 31st march of the next year. The current assessment year is 2007 -008(1.4.2007 to 31.03.2008). An Assessee is liable to pay tax on the income of the previous year during the next following assessment year. Eg: during the Assessment year 2007-08 income earned during 2006-07 is taxed.
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