Environmental Science MCQ – Asked in Previous Years, WBCS Mains

Answer – C. to make turbidity standard.
Explanation-
▪ Formazin is used in turbidity analysis to prepare a standardized turbidity solution. It is a synthetic polymer that, when mixed with water, produces a suspension with known turbidity levels.

▪ This standardized solution is then used as a reference to calibrate turbidity meters or instruments and to compare the turbidity of other samples. Formazin helps establish a consistent and reproducible measurement scale for turbidity.

Answer – C. Faecal pollution
Explanation-
▪ MPN (Most Probable Number) is a statistical method used to estimate the concentration of microorganisms, particularly coliform bacteria, in a water sample. It is commonly employed to assess the presence of faecal contamination in water sources. The MPN test involves multiple dilutions of the sample and inoculation into growth media to determine the most probable number of microorganisms present based on the observed growth patterns.

Answer –D. Ozone (O<sub>3)
Explanation-
▪ Ozone (O3) is a secondary pollutant that is produced as a result of the interaction between sunlight (UV rays) and certain primary pollutants, such as nitrogen oxides (NOx) and volatile organic compounds (VOCs).

▪ When these primary pollutants undergo photochemical reactions in the presence of sunlight, ozone formation occurs, especially in polluted urban environments. Ozone is a major component of smog and has harmful effects on human health and the environment.</sub>

Answer – B. 1985
Explanation-
▪ The major stratospheric ozone layer depletion over Antarctica, commonly known as the “ozone hole,” was discovered in 1985. Scientists from the British Antarctic Survey reported a significant decline in ozone levels over the Antarctic region, particularly during the spring season. This discovery led to increased awareness and international efforts to address the causes and consequences of ozone depletion.

Answer – A. CFCs.
Explanation-
▪ The peeling or depletion of the ozone layer, commonly referred to as the “Ozone umbrella,” is primarily caused by chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS). CFCs were once widely used in aerosol propellants, refrigerants, and other industrial applications.

▪ When released into the atmosphere, these chemicals can reach the stratosphere, where they break down under the influence of sunlight and release chlorine atoms. The chlorine atoms then catalytically destroy ozone molecules, leading to the thinning of the ozone layer.

Answer – A. 1986
Explanation-
▪ The Environmental Protection Act was enacted in India in the year 1986. This legislation aims to provide the framework for the protection and improvement of the environment. It empowers the central government to take measuresto prevent and control pollution, regulate environmental impact assessments, and enforce environmental standards across various sectors.

Answer – C. Cr⁺⁶
Explanation-
▪ Hexavalent chromium, represented as Cr⁺⁶, is the toxic species of chromium in water. It is a highly carcinogenic compound that can enter water sources through industrial discharges and improper waste disposal. Exposure to high levels of hexavalent chromium in drinking water can pose serious health risks, including an increased risk of cancer and other adverse health effects.

Answer –B. Air pollution
Explanation-
▪ A cyclone collector, also known as a cyclone separator, is a device used to minimize air pollution by separating solid particles or particulate matter from the air stream. It operates based on the principle of centrifugal force, causing the heavier particles to be separated from the air and collected in a separate chamber.

▪ Cyclone collectors are commonly used in industries and air pollution control systems to remove dust, pollutants, and particulate matter from industrial exhaust gases before they are released into the atmosphere.

Answer – D. UV radiations reach the earth
Explanation-
▪ The ozone hole, characterized by a significant depletion of stratospheric ozone, leads to an increased influx of ultraviolet (UV) radiations reaching the Earth’s surface. Ozone in the stratosphere acts as a protective layer, absorbing most of the incoming UV-B and UV-C radiation from the sun.

▪ When the ozone layer is depleted, more UV radiation penetrates the atmosphere, which can have harmful effects on human health, ecosystems, and the environment. Increased UV radiation can cause skin cancer, cataracts, and disruptions in the marine and terrestrial ecosystems.

Answer – B. Uttarakhand
Explanation-
▪ Rajaji National Park is situated in Uttarakhand, India. It is named after C. Rajagopalachari, a prominent freedom fighter and the last Governor-General of India. The national park is spread across the Shivalik ranges and encompasses a diverse range of flora and fauna, including elephants, tigers, leopards, deer, and various bird species. Rajaji National Park is known for its natural beauty and is an important protected area for wildlife conservation.