1. Atmospheric CO₂ concentration at present is at
(a) 300 ppm
(b) 330 ppm
(c) 360 ppm
(d) 400 ppm
2. In the Gaussian plume dispersion studies stability, class ‘B’ represents atmosphere that is
(a) moderately stable.
(b) moderately unstable.
(c) slightly unstable.
(d) slightly stable.
3. Greenhouse effect is due to
(a) atmospheric CO₂ absorbing sun’s radiation.
(b) atmospheric ozone absorbing sun’s radiation.
(c) methane absorbing UV radiation in ionosphere.
(d) atmospheric CO₂ absorbing reflected radiation from earth.
4. An observer on a level ground standing at a distance of 80 m away from a source receives 100 dBA noise. As the observer shifts to 320 m away from source, the SPL experienced decreases to
(a) 90 dB
(b) 80 dBA
(c) 88 dBA
(d) 110 dB
5. Dissolved oxygen (DO) level in fresh water flowing at 300 L/s is 7 mg/L. DO fall to 5.0 mg/L after the fresh water mixes with an effluent stream having DO of 1.0 mg/L. The flow rate of the effluent stream is
(a) 100 L/s
(b) 150 L/s
(c) 175 L/s
(d) 200 L/s
6. The incorrect statement is : Smog formation is contributed by
(a) unstable atmosphere.
(b) unburnt hydrocarbons.
(c) sunshine.
(d) nitrogen oxides.
7. In order to trap coarse dust particles, one may preferably use
(a) electrostatic precipitator
(b) konimeter
(c) cyclone
(d) bag-house filter
8. Flocculation jar test is performed to estimate
(a) reactivity of dissolved solids.
(b) alkalinity of water
(c) heavy metals in water
(d) settling rate of turbid water
9. Dissolved organic substances in water can be removed by
(a) passing through activated carbon
(b) chlorination
(c) UV radiation
(d) fumigation
10. An overpressure of 2 Pa results in a noise level of
(a) 110 dB
(d) 100 dB
(c) 90 dB
(d) 80 dB
Answers
1. (d) As of 2018, CO₂ constitutes about 0.041% by volume of the atmosphere, (equal to 410 ppm).
2. (b)
Pasquill Stability Classes
- A: Extremely unstable conditions
- B: Moderately unstable conditions
- C: Slightly unstable conditions
- D: Neutral conditions
- E: Slightly stable conditions
- F: Moderately stable conditions
- G: Extremely Stable
3. (d) The gases which are transparent to solar radiation but retain and partially reflect back long-wave heat radiations are called greenhouse gases. Greenhouse gases are essential for keeping the earth warm and hospitable. The various greenhouse gases are carbon dioxide (warming effect 60%), methane (warming effect 20%), chlorofluorocarbons or CFCs (warming effect 14 percent) and nitrous oxide (warming effect 6 percent). Other gases of minor importance are water vapour and ozone.
4. Wrong question. Data is missing.
5. (d)
DO = [QsDOs + QRDOR]/[QS + QR]
Where
QS and QR is flow of water in stream and river respectively
(DO)S and (D)R is dissolved oxygen in stream and river respectively
Hence, 5 = [QS x 2 + 300 x 7]/[QS + 300]
⇒ QS = 200 L/s
6. (a) Nitrogen oxides come from car exhaust, coal power plants, and factory emissions. VOCs are released from gasoline, paints, and many cleaning solvents. When sunlight hits these chemicals, they form airborne particles and ground-level ozone—or smog.
7. (c) Cyclones of this type are used primarily to collect coarse particles when collection efficiency and space requirements are not a major consideration. Collection efficiency for conventional cyclones on 10 micron particles is generally 50 to 80 percent.
8. (d)
9. (a) Granular activated carbon (GAC) adsorption is a widespread water treatment technology especially applied in waterworks for removing dissolved organic compounds (natural organic matter, micropollutants).
10. Wrong question
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