Environmental Pollution

Step 1: Understanding the Ringelmann scale.
The Ringelmann scale is a visual method developed to assess the opacity or darkness of smoke emitted from chimneys and stacks.
Step 2: Purpose of the scale.
It compares the darkness of smoke with a set of standardized grey shades, ranging from clear (Ringelmann 0) to very dark (Ringelmann 5).
Step 3: Analyzing the options.
(A) Incorrect, CO concentration is measured using gas analyzers.
(B) Incorrect, CO is measured using infrared analyzers.
(C) Correct, the Ringelmann scale is specifically used to grade the density of smoke.
(D) Incorrect, automobile exhaust grading is not done using Ringelmann charts.
Step 4: Conclusion.
The Ringelmann scale is used to grade the density of smoke.

Step 1: Understanding photochemical oxidants.
Photochemical oxidants are secondary air pollutants formed by reactions of nitrogen oxides and hydrocarbons in the presence of sunlight.
Step 2: Formation of ozone.
Ground-level ozone is produced when NO and volatile organic compounds react under sunlight. It is the most abundant and reactive photochemical oxidant in the atmosphere.
Step 3: Evaluating the options.
(A) H O : Not the major photochemical oxidant in ambient air.
(B) O : Correct, ozone is the principal photochemical oxidant.
(C) NO: A precursor pollutant, not an oxidant.
(D) PAN: A secondary pollutant, but not the major oxidant.
Step 4: Conclusion.
The major photochemical oxidant present in photochemical smog is ozone (O ).

Step 1: Understanding weedicide.
A weedicide is a chemical substance used to destroy or control unwanted plants and weeds. These chemicals are commonly used in agriculture and warfare-related defoliation programs.
Step 2: Understanding Agent Orange and Herbicide Orange.
Agent Orange is a well-known chemical defoliant and weedicide used during the Vietnam War to destroy forest cover and crops. Herbicide Orange refers to a similar class of herbicidal chemicals used to control vegetation.
Step 3: Analyzing the options.
(A) Agent green: Incorrect, as it is not recognized as a standard weedicide.
(B) Herbicide orange: Correct, since it is used to destroy unwanted vegetation.
(C) Agent orange: Correct, as it is a powerful weedicide and defoliant.
(D) Both B & C: Correct, because both are weedicides.
Step 4: Conclusion.
The correct answer is (D) Both B & C, as both Herbicide Orange and Agent Orange act as weedicides.

Step 1: Understanding coal-based thermal power stations.
Coal-based thermal power stations generate electricity by burning coal. During combustion, various pollutants are released into the atmosphere due to the presence of impurities in coal and incomplete combustion processes.
Step 2: Identifying major pollutants released.
Burning coal releases nitrogen oxides (NOX) due to high-temperature combustion, sulphur dioxide (SO2) because coal contains sulphur impurities, and suspended particulate matter (SPM) in the form of ash and fine dust particles.
Step 3: Analyzing the options.
(A) NOX and SO2: Incorrect, as this option ignores particulate matter, which is a major pollutant.
(B) NOX, SO2 and SPM: Correct, as modern coal-based thermal power stations mainly emit these three pollutants.
(C) NOX, SO2, SPM and CO: Incorrect, as carbon monoxide (CO) is not a significant emission in modern thermal power plants due to efficient combustion.
(D) NOX, SO2 and CO: Incorrect, since it excludes suspended particulate matter.
Step 4: Conclusion.
The correct answer is (B) NOX, SO2 and SPM because these are the primary atmospheric pollutants released by modern coal-based thermal power stations.