Pollution: UPSC Previous Year Questions (Environment and Ecology)
3 previous year UPSC Prelims questions on Pollution (Environment and Ecology). Choose an option to see the answer and explanation.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
Showing 1–3 of 3 questions
UPSC 2017Environment and Ecology · Pollution
Q1. Biological Oxygen Demand (BOD) is a standard criterion for:
Explanation
BOD measures the amount of dissolved oxygen required by microorganisms to break down organic material in water over a specific time. BOD is the amount of dissolved oxygen needed by bacteria in decomposing the organic wastes present in water. It is measured in milligrammes per litre of water of oxygen. The higher value of BOD indicates low (Dissolved Oxygen) DO content of water. BOD is not a reliable method for assessing water pollution because it only includes biodegradable elements.
Additional insight:
Standard Method 5210B is the most widely used method for determining Biological Oxygen Demand (BOD). It measures the difference in dissolved oxygen (DO) over a five-day incubation period at 20°C. The initial DO is recorded, and after incubation, the final DO is measured. The BOD value is then calculated based on oxygen depletion. Higher BOD indicates poor water quality due to higher oxygen demand, while lower BOD suggests purer water with less oxygen consumption. DO levels are lower in summer as warm water holds less oxygen.
UPSC 2017Environment and Ecology · Pollution
Q2. In the context of solving pollution problems, what is/are the advantage/advantages of bioremediation techniques? 1. It is a technique for cleaning up pollution by enhancing the same biodegradation process that occurs in nature. 2. Any contaminant with heavy metals such as cadmium and lead can be readily and completely treated by bioremediation using microorganisms. 3. Genetic engineering can be used to create microorganisms specifically designed for bioremediation. Select the correct answer using the code given below:
Explanation
Bioremediation is a branch of biotechnology that employs the use of living organisms in the removal of contaminants, pollutants, and toxins from soil, water, and other environments. These organisms can include microbes and bacteria. As a result, compared to other cleanup techniques, bioremediation causes less disruption to the neighbourhood communities.
Statement 1 is correct: Bioremediation uses naturally occurring organisms to break down hazardous substances into less toxic or non-toxic substances.
Statement 2 is incorrect: Not all contaminants are easily treated by bioremediation using microorganisms. For eg. Heavy metals such as cadmium and lead are not readily absorbed or captured by microorganisms.
Statement 3 is correct: The use of genetic engineering to create organisms specifically designed for bioremediation has great potential. For e.g. Alcanivorax, a bacteria with oil-eating abilities, can be used to create species that are much more capable of cleaning oil spills.
Additional insight:
Types of Bioremediation:
Aerobic Bioremediation: Requires oxygen for microbial reactions, where bacteria use a carbon substrate as an electron donor and oxygen as the electron acceptor to break down contaminants. Anaerobic Bioremediation: Occurs in the absence of oxygen, using alternatives like nitrate, sulfate, or carbon dioxide as electron acceptors. Processes include fermentation, methanogenesis, and reductive dechlorination to degrade pollutants. Cometabolic Bioremediation: Microbes degrade contaminants without gaining energy or carbon from them, breaking down pollutants as a side reaction while metabolizing other substances.
Exam tip:
For S2, "Readily and Completely" treated- it is Clearly an extreme phrase, hence very unlikely to be true. If this would have been true, water and soil pollution would have been talk of past, but that’s not the case, hence likely false. Eliminating options B and D.
UPSC 2017Environment and Ecology · Pollution
Q3. It is possible to produce algae based biofuels, but what is/are the likely limitation(s) of developing countries in promoting this industry? 1. Production of algae based biofuels is possible in seas only and not on continents. 2. Setting up and engineering the algae based biofuels production requires high level of expertise/ technology until the construction is complete. 3. Economically viable production necessitates the setting up of large scale facilities which may raise ecological and social concerns. Select the correct answer using the code given below:
Explanation
Biofuels are hydrocarbon fuel that is created in a short amount of time--days, weeks, or even months--from organic matter (living or once-living material). Biofuels may be solid, liquid or gaseous in nature:
Solid: Wood, dried plant material, and manure Liquid: Bioethanol and Biodiesel Gaseous: Biogas
Statement 1 is incorrect: Algaculture (farming algae) can be initiated on land unsuitable for agriculture or saline water or wastewater. Statements 2 and 3 are correct: Producing algae for biofuels (excluding simple seaweed production) requires significant capital investments, which may be a significant barrier in developing countries that have a weak investment climate. Also during the setup stage, the production of algae- based biofuels will necessitate expertise in advanced technology.
Exam tip:
For S1, "seas ONLY" is an extreme absolute phrase and hence unlikely to be true. Thus eliminate options A and D. In contrast, S 2 and S3 are too general and practical to be false, hence more likely to be true.
Answer key for these questions
Q
UPSC year
Correct answer
1
2017
(c) Pollution assay in aquatic ecosystems
2
2017
(c) 1 and 3 only
3
2017
(b) 2 and 3 only
Frequently asked questions
How many previous year UPSC questions are there on Pollution?
This page covers 3 previous year UPSC Prelims GS Paper-I questions on Pollution (Environment and Ecology), asked from 2005 to 2025. Each has the correct answer and an explanation.
How should I use previous year UPSC questions for Prelims?
Attempt each question first, then open the answer and read the explanation for every option. Repeat by chapter, and track which statements UPSC reuses across years. Previous year questions show the exam pattern and difficulty level.
Which years are covered for Pollution?
Questions on Pollution (Environment and Ecology) are available for 14 years, from 2005 to 2025. Use the Year filter to practise a single paper.
