GATE Overflow for GATE ESE - Recent activity in Air and Noise Pollution

Edited: GATE ES 2026 | Question: 53

Wed, 15 Apr 2026 12:25:22 +0000

The concentration of chemical $\text{A}$ in ambient air is $50 ~\mu \mathrm{~g} / \mathrm{m}^{3}$ and the toxicological index limit for a threshold health effect for this chemical is $5$ $\mathrm{mg}$.

If the average breathing rate is $4 \mathrm{~L} / \mathrm{min}$, the minimum time of exposure that can lead to any health effect is $\_\_\_\_$ days (rounded off to one decimal place).

Edited: GATE ES 2026 | Question: 50

Wed, 15 Apr 2026 12:04:22 +0000

In a stack emission measurement at an industry, the stack cross-sectional area at $30$ m height was divided into four equal sectors. The measured velocities and $\mathrm{SO}_{2}$ concentrations through these sectors at this height are given in the table.

The mean $\mathrm{SO}_{2}$ concentration from the stack is $\_\_\_\_$ $\mathrm{mg} / \mathrm{m}^{3}$ (rounded off to two decimal places).

$$\begin{array}{|c|c|c|}
\hline
\begin{array}{c}
\textbf{Sector} \\
\textbf{Number}
\end{array}
&
\begin{array}{c}
\textbf{Velocity} \\
(\mathrm{m/s})
\end{array}
&
\begin{array}{c}
\mathrm{SO}_{2}\ \textbf{Concentration} \\
(\mathrm{mg}/\mathrm{m}^{3})
\end{array}
\\
\hline
1 & 15 & 1000 \\
\hline
2 & 17 & 1150 \\
\hline
3 & 19 & 1250 \\
\hline
4 & 21 & 1275 \\
\hline
\end{array}$$

Edited: GATE ES 2026 | Question: 37

Wed, 15 Apr 2026 10:56:17 +0000

The sound level measured at various locations in an urban area is given in the table.

The average sound level for that area is $\_\_\_\_$ dBA (rounded off to two decimal places).

$$\begin{array}{|l|l|l|l|l|}
\hline
\textbf{Location} & A & B & C & D \\
\hline
\begin{array}{l}
\text{Sound level} \\
(\text{dBA})
\end{array}
& 40 & 55 & 65 & 75 \\
\hline
\end{array}$$

Edited: GATE ES 2026 | Question: 36

Wed, 15 Apr 2026 10:50:51 +0000

Which of the following options is/are CORRECT assumption(s) in the Gaussian plume dispersion model?

The concentration of pollutants emitting from stack is continuous.
The process is under steady state.
The pollutants emitted are non-conservative.
The diffusion of pollutants is dominant in comparison with advection in the direction of wind.

Edited: GATE ES 2026 | Question: 30

Wed, 15 Apr 2026 10:37:56 +0000

Which ONE of the following options CORRECTLY matches the atmospheric stability conditions with plume conditions/ behaviours given in the table?

$$\begin{array}{|l|l|}
\hline
\begin{array}{c}
\textbf{Atmospheric Stability} \\
\textbf{Conditions}
\end{array}
&
\begin{array}{c}
\textbf{Plume Conditions/} \\
\textbf{Behaviours}
\end{array} \\
\hline
(P)\ \text{Strong instability} & (i)\ \text{Fanning plume} \\
\hline
(Q)\ \text{Neutral stability} & (ii)\ \text{Fumigation} \\
\hline
(R)\ \text{Surface inversion} & (iii)\ \text{Coning plume} \\
\hline
(S)\ \text{Aloft inversion} & (iv)\ \text{Looping plume} \\
\hline
\end{array}$$

$\text{(P) - (i); (Q) - (ii); (R) - (iii); (S) - (iv)}$
$\text{(P) - (iv); (Q) - (iii); (R) - (i); (S) - (ii)}$
$\text{(P) - (iii); (Q) - (iv); (R) - (ii); (S) - (i)}$
$\text{(P) - (ii); (Q) - (i); (R) - (iv); (S) - (iii)}$

Edited: GATE ES 2026 | Question: 29

Wed, 15 Apr 2026 10:34:37 +0000

Which ONE of the following options CORRECTLY matches the Criteria Air Pollutants with measurement methods used in Continuous Ambient Air Quality Monitoring Stations (CAAQMS) operated by Central Pollution Control Board (CPCB) given in the table?

$$\begin{array}{|ll|ll|}
\hline & \textbf{Criteria Air Pollutants} & & \textbf{Measurement Methods} \\
\hline \text{(P)} & \text{Sulphur Dioxide } (\mathrm{SO}_{2},\ \mu \mathrm{g}/\mathrm{m}^{3}) & (i) & \text{Chemiluminescence} \\
\hline \text{(Q)} & \text{Nitrogen Dioxide } (\mathrm{NO}_{2},\ \mu \mathrm{g}/\mathrm{m}^{3}) & (ii) & \text{Non Dispersive Infra}\\ &&& \text{Red (NDIR) spectroscopy} \\
\hline \text{(R)} & \text{Particulate Matter } (\mathrm{PM}_{2.5},\ \mu \mathrm{g}/\mathrm{m}^{3}) & (iii) & \text{Ultraviolet fluorescence} \\
\hline \text{(S)} & \text{Carbon Monoxide } (\mathrm{CO},\ \mathrm{mg}/\mathrm{m}^{3}) & (iv) & \text{Beta attenuation} \\ \hline \end{array}$$

$\text{(P) - (i); (Q) - (ii); (R) - (iii); (S) - (iv)}$
$\text{(P) - (iv); (Q) - (iii); (R) - (ii); (S) - (i)}$
$\text{(P) - (iii); (Q) - (i); (R) - (iv); (S) - (ii)}$
$\text{(P) - (ii); (Q) - (iii); (R) - (i); (S) - (iv)}$

Edited: GATE ES 2026 | Question: 11

Wed, 15 Apr 2026 09:35:39 +0000

In the design of air pollution control devices, size of the particles that are removed with $50 \%$ efficiency is termed as $\_\_\_\_$.

mean size
mode size
cut size
median size

Edited: GATE ES 2025 | Question: 51

Mon, 02 Jun 2025 20:04:47 +0000

An incandescent light bulb operated for two hours per day uses $12.2 \: \text{kWh}$ of energy per month. Burning of one kg of coal generates $2 \: \text{kWh}$ of electrical energy and releases $7 \: g$ of $\mathrm{PM}_{10}$. The reduction in $\mathrm{PM}_{10}$ emitted per month, if this incandescent bulb is replaced with a light emitting diode (LED) bulb which consumes $1 / 6^{\text {th }}$ of energy, is $\_\_\_\_\_ \: g$. (rounded off to one decimal place)

Edited: GATE ES 2025 | Question: 50

Mon, 02 Jun 2025 20:03:37 +0000

A particle dispersoid has $1510$ spherical particles of uniform density. An air purifier is proposed to be used to remove these particles. The diameter specific number of particles in the dispersoid, along with the number removal efficiency of the proposed purifier is shown in the following table:
$$\begin{array}{|l|l|l|} \hline \text{Diameter of the} & \text{Number of particles} & \text{Number removal} \\ \text{particle} (\mu \mathrm{m}) && \text{efficiency} (\%) \\
\hline 1 & 1000 & 99 \\ \hline 10 & 500 & 75 \\ \hline 100 & 10 & 10 \\ \hline \end{array}$$

The overall mass removal efficiency of the proposed purifier is $\_\_\_\_\_ \: \%$. (rounded off to one decimal place)

Edited: GATE ES 2025 | Question: 31

Mon, 02 Jun 2025 19:43:41 +0000

At a pressure of $1$ atmosphere and temperature of $25^{\circ} \mathrm{C}$, $365 \mu \mathrm{~g} \mathrm{~m}{ }^{-3}$ of a pollutant corresponds to mixing ratio of $139$ parts per billion (ppb). The atomic weights: $\mathrm{C}- 12$, $\mathrm{H}-1, \mathrm{O}-16, \mathrm{~N}-14$ and $\mathrm{S}-32$. Which one of the following options most closely represents the pollutant

$\mathrm{SO}_{2}$
$\mathrm{NO}_{2}$
$\mathrm{O}_{3}$
$\mathrm{CO}$

Edited: GATE ES 2025 | Question: 30

Mon, 02 Jun 2025 19:43:00 +0000

Consider the following statements

Sound pressure changes with distance from the source
Sound power is a property of the source
Sound intensity is sound power per unit volume

Choose the correct option from the following

(i), (ii), and (iii) are correct
only (i) and (ii) are correct
only (i) and (iii) are correct
only (ii) and (iii) are correct

Edited: GATE ES 2025 | Question: 17

Mon, 02 Jun 2025 16:53:27 +0000

Stubble burning results in release of particulate matter, volatile organic compounds, oxides of nitrogen and sulfur, to name a few. A researcher is planning to use a conventional Gaussian dispersion model to estimate the contribution of stubble burning in a nearby state to air pollution in New Delhi.

Choose the option(s) which could explain the possible limitations in this approach

assumption of steady state conditions e.g. constant wind speed, wind direction, and mission, etc. in conventional Gaussian dispersion models
non-accounting of wet and dry deposition in conventional Gaussian dispersion models
non-handling of chemical transformation of pollutants in conventional Gaussian dispersion models
requirement of more computational resources by conventional Gaussian dispersion models compared to chemical transport models

Edited: GATE ES 2025 | Question: 10

Mon, 02 Jun 2025 16:01:33 +0000

Consider the following statements

$P$: According to the National Ambient Air Quality Standards (Central Pollution Control Board, Govt. of India, notification $2009$), annual time weighted average $\mathrm{PM}_{10}$ standard is more than $\mathrm{PM}_{2.5}$ standard.

$Q$ : According to the National Air Quality Index released by Govt. of India in $2015$, sub index value of $\mathrm{PM}_{10}$ can be less than that of $\mathrm{PM}_{2.5}$.

Choose the correct option from the following

$P$ is TRUE; $Q$ is FALSE
$P$ is FALSE; $Q$ is TRUE
$P$ is TRUE; $Q$ is TRUE
$P$ is FALSE; $Q$ is FALSE

Recategorized: GATE ES 2024 | Question: 20

Mon, 21 Apr 2025 17:03:50 +0000

Which is/are the secondary air pollutant(s)?

$\mathrm{O}_{3}$
$\mathrm{HNO}_{3}$
$\mathrm{CO}_{2}$
$\mathrm{H}_{2} \mathrm{SO}_{4}$

Recategorized: GATE ES 2024 | Question: 19

Mon, 21 Apr 2025 17:03:48 +0000

The equipment that can be used to control particulate air pollution in an industrial unit is/are

Electrostatic precipitator
cyclone separator
Gravity settler
Incinerator

Recategorized: GATE ES 2024 | Question: 31

Mon, 21 Apr 2025 17:03:14 +0000

A gravity settling chamber of height ' $H$ ' and length ' $L$ ' is designed to control particulate air pollution. In the chamber, the horizontal velocity of air flow is ' $V_{h}$ ' and terminal settling velocity of the target particle is ' $V_{t}$ '.

Which one of the following expressions is the correct concept used to calculate the minimum size of the target particle that will be removed with $100 \%$ efficiency?

$\frac{V_{t}}{L}=\frac{V_{h}}{H}$
$V_{h} \times V_{t}=L \times H$
$V_{h}=V_{t} \times L \times H$
$\frac{V_{t}}{H}=\frac{V_{h}}{L}$

Recategorized: GATE ES 2024 | Question: 49

Mon, 21 Apr 2025 17:02:16 +0000

An industrial stack emits $100 \mathrm{~g} / \mathrm{s}$ of $\mathrm{CO}$ at an effective height of ' $\mathrm{H}$ ', where the wind speed is $5 \mathrm{~m} / \mathrm{s}$. At $3 \mathrm{~km}$ distance downwind, the values of dispersion coefficient in $\mathrm{y}-$ direction and z-direction are $50 \mathrm{~m}$ and $25 \mathrm{~m}$, respectively. The $\mathrm{CO}$ concentration at the centerline of the plume at $3 \mathrm{~km}$ distance downwind is __________ $\mathrm{mg} / \mathrm{m}^{3}$ $\text{(rounded off to 2 decimal places)}$?

Use Gaussian plume model and value of $\pi=3.14$. Neglect reactions and the ground effect of plume in the calculations.

Recategorized: GATE ES 2024 | Question: 48

Mon, 21 Apr 2025 17:02:13 +0000

Two sources of noise, adjacent to each other in a room, have sound pressure levels of $30$ and $40$ decibel $\text{(dB)}$. The combined sound pressure level in the room is ________ $\mathrm{dB}$ $\text{(rounded off to $2$ decimal places)}$.

Use reference sound pressure as $20 \mu \mathrm{Pa}$.

Recategorized: GATE ES 2023 | Question: 8

Mon, 21 Apr 2025 17:01:13 +0000

Which of the following is true according to the Central Pollution Control Board $\text{(CPCB)}$, Government of India's notification issued in the year $2009$?

$24$ hour averaged standard for $\mathrm{PM}_{2.5}$ in ambient air is $60 \mu \mathrm{g} / \mathrm{m}^3 ; 24$ hour averaged standard for $\mathrm{PM}_{10}$ in ambient air is $100 \mu \mathrm{g} / \mathrm{m}^3$
$24$ hour averaged standard for $\mathrm{PM}_{2.5}$ in indoor air is $60 \mu \mathrm{g} / \mathrm{m}^3 ; 24$ hour averaged standard for $\mathrm{PM}_{10}$ in ambient air is $100 \mu \mathrm{g} / \mathrm{m}^3$
$24$ hour averaged standard for $\mathrm{PM}_{2.5}$ in ambient air is $60 \mu \mathrm{g} / \mathrm{m}^3 ; 24$ hour averaged standard for $\mathrm{PM}_{10}$ in indoor air is $100 \mu \mathrm{g} / \mathrm{m}^3$
$24$ hour averaged standard for $\mathrm{PM}_{2.5}$ in indoor air is $60 \mu \mathrm{g} / \mathrm{m}^3 ; 24$ hour averaged standard for $\mathrm{PM}_{10}$ in indoor air is $100 \mu \mathrm{g} / \mathrm{m}^3$

Recategorized: GATE ES 2023 | Question: 9

Mon, 21 Apr 2025 17:01:10 +0000

The sub index values of $\mathrm{NO}_{2}, \mathrm{SO}_{2}$ and $\mathrm{PM}_{10}$ are $80,80$ and $100$, respectively. According to the National Air Quality Index $\text{(NAQI)}$ released by the Government of India in the year $2015$, the overall $\text{(NAQI)}$ is

$80$
$260$
$100$
$151$

Recategorized: GATE ES 2023 | Question: 30

Mon, 21 Apr 2025 17:00:10 +0000

A boiler in an industry, located where high plume rise is expected, releases flue gas with fine particulate matter. Which one of the following options is most suited and efficient if this particulate matter is intended for reuse?

reduce stack height and increase stack diameter
use of wet collectors
use of flue gas desulfurization $\text{(FGD)}$
use of electrostatic precipitator $\text{(ESP)}$

Recategorized: GATE ES 2023 | Question: 51

Mon, 21 Apr 2025 16:59:03 +0000

An industry with an effective stack height of $80 \mathrm{~m}$ emits $1200 \mathrm{~g} / \mathrm{h}$ of $\mathrm{CO}$. The windrose plotted using the meteorological data at the top of the stack, and the relation between dispersion coefficients and wind direction are given below:

\begin{array}{|l|c|c|}
\hline \multirow{2}{*}{ Wind Direction } & \multicolumn{2}{|c|}{ Dispersion coefficients (in m) } \\
\cline { 2 - 3 } & Crosswind direction & Vertical direction \\
\hline Northeast & 50 & 20 \\
\hline North & 45 & 30 \\
\hline Northwest & 40 & 35 \\
\hline East & 45 & 30 \\
\hline Southeast & 55 & 35 \\
\hline South & 60 & 40 \\
\hline Southwest & 65 & 45 \\
\hline West & 70 & 50 \\
\hline
\end{array}

During the maximum duration of the year, the ground level $\mathrm{PM}_{2.5}$ concentration at the downwind distance of $2 \mathrm{~km}$ (at the plume centerline) from the stack is _________ (in $\mu \mathrm{g} / \mathrm{m}^{3}$, $\text{rounded off to two decimal places).}$

Recategorized: GATE ES 2022 | Question: 13

Mon, 21 Apr 2025 16:47:23 +0000

Which one of the following is most commonly used raw material in flue gas desulfurization units?

Limestone
Titanium Oxide
Fenton reagent
Beryllium Oxide

Recategorized: GATE ES 2022 | Question: 20

Mon, 21 Apr 2025 16:47:03 +0000

$\quad \mathrm{PM}_{2.5}$ concentrations in ambient air can be measured using

Beta attenuation method
Chemiluminescence method
Gravimetric method
Non dispersive infrared spectroscopy method

Recategorized: GATE ES 2022 | Question: 31

Mon, 21 Apr 2025 16:46:32 +0000

A bag filter is used for removal of particulate matter having a range of sizes. The correct sequence of air filtration mechanisms for their removal, in order of decreasing size, is

Diffusion, Impaction, Disintegration
Disintegration, Impaction, Interception
Diffusion, Impaction, Interception
Impaction, Interception, Diffusion

Recategorized: GATE ES 2022 | Question: 32

Mon, 21 Apr 2025 16:46:27 +0000

A relatively calm room has background sound power level (SPL) of 30 decibels (dB). A television and a radio with SPL of $80 \mathrm{~dB}$ and $70 \mathrm{~dB}$, respectively, started operating simultaneously in this room. Given the reference sound power is $10^{-12}$ Watts, what will be the resulting SPL in the room, assuming all the sources operate independently?

$180.0 \mathrm{~dB}$
$80.4 \mathrm{~dB}$
$82.4 \mathrm{~dB}$
$150.0 \mathrm{~dB}$

Recategorized: GATE ES 2022 | Question: 37

Mon, 21 Apr 2025 16:46:16 +0000

According to the National Ambient Air Quality Standards (Central Pollution Control Board, Govt. of India, notification 2009) which of the following statement(s) is/are correct?

$\mathrm{SO}_{2}$ and $\mathrm{NO}_{2}$ have annual average standards; while $\mathrm{O}_{3}$ and $\mathrm{CO}$ have eight hour average standards.
$\mathrm{SO}_{2}$ and $\mathrm{CO}$ have annual average standards; while $\mathrm{O}_{3}$ and $\mathrm{NO}_{2}$ have eight hour average standards.
$\mathrm{SO}_{2}$ and $\mathrm{CO}$ have eight hour average standards; while $\mathrm{O}_{3}$ and $\mathrm{NO}_{2}$ have hourly average standards.
$\mathrm{SO}_{2}$ and $\mathrm{NO}_{2}$ have 24 hour average standards; while $\mathrm{O}_{3}$ and $\mathrm{CO}$ have hourly average standards.

Recategorized: GATE ES 2022 | Question: 38

Mon, 21 Apr 2025 16:46:13 +0000

Consider the figure shown below for three different cases:
Which of the following statement(s) is/are correct for surface level emissions, given the environmental temperature?

Case P represents unstable atmosphere and results in higher dispersion of emissions.
Case Q represents subsidence inversion and results in higher dispersion of emissions than Case P.
Case Q represents elevated inversion and results in lower dispersion of emissions than Case P.
Case R represents subsidence inversion and results in lower dispersion of emissions than Case P.

Recategorized: GATE ES 2022 | Question: 54

Mon, 21 Apr 2025 16:45:29 +0000

A ground level source emits $1000 \mathrm{~g}$ per day of $\mathrm{SO}_{2}$. In vicinity of the source, ambient temperature is measured at $10 \mathrm{~m}$ and $110 \mathrm{~m}$ as $25^{\circ} \mathrm{C}$ and $24.5^{\circ} \mathrm{C}$, respectively. The mean wind speed is found to be $2 \mathrm{~m}$ per second. The dispersion coefficients at 1000 $\mathrm{m}$ downwind distance from the source are given in table below:

Estimated ground level concentration $\text{(in $\mu$ g / $m^{3}$, rounded off to two decimal places)}$ of $\mathrm{SO}_{2}$ at a downwind distance of $1000 \mathrm{~m}$ (at the plume centerline) from the source is________

Recategorized: GATE ES 2021 | Question: 4

Mon, 21 Apr 2025 15:42:37 +0000

A sample of air is collected in the morning at an ambient temperature of $\mathbf{2 5}{ }^{\circ} \mathbf{C}$. The concentration of carbon monoxide $\text{(CO)}$ in this sample is $30$ppmv $\text{(ppm by volume)}$. The same sample is analysed later in the afternoon when the sample temperature is $35^{\circ} \mathbf{C}$. The analysis results will show the CO concentration as___________.

$<29 \mathrm{ppmv}$
$>30 \mathrm{ppmv}$
$=30 \mathrm{ppmv}$
$=29 \mathrm{ppmv}$

Recategorized: GATE ES 2021 | Question: 10

Mon, 21 Apr 2025 15:42:21 +0000

In the context of noise pollution, SPL is the sound pressure level in decibels (dB). The relationship between SPL, the root mean square $\text{(rms)}$ sound pressure $p$ $\text {,and the reference (hearing threshold) pressure } p_{0} \text { is }$ expressed as ___________.

$\mathrm{SPL}=20 \times \log _{10} \frac{p}{p_{0}}$
$\mathrm{SPL}=20 \times \log _{10} \frac{p_{0}}{p}$
$\mathrm{SPL}=20-\log _{10} \frac{p}{p_{0}}$
$\mathrm{SPL}=20+\log _{10} \frac{p}{p_{0}}$

Recategorized: GATE ES 2021 | Question: 28

Mon, 21 Apr 2025 15:41:36 +0000

Match the entries in Column I with the correct entries in Column II.

Column I	Column II
Diffusion	Pasquill
Drag force	Fick
Atmospheric stability	Stokes

$\text{P-(iii), Q-(ii), R-(i)}$
$\text{P-(ii), Q-(i), R-(iii)}$
$\text{P-(i), Q-(iii), R-(ii)}$
$\text{P-(ii), Q-(iii), R-(i)}$

Recategorized: GATE ES 2021 | Question: 36

Mon, 21 Apr 2025 15:41:09 +0000

Which of the following isiare the dominant mechanism(s) for the removal of spherical particles with diameter less than $10 \mu \mathrm{m}$ from a gas stream using a fabric filter?

Impaction
Gravitation
Interception
Diffusion

Recategorized: GATE ES 2021 | Question: 37

Mon, 21 Apr 2025 15:41:07 +0000

In air pollution, which of the following is/are classified as primary pollutants?

Carbon monoxide $(\mathrm{CO})$
Sulphur dioxide $\left(\mathrm{SO}_{2}\right)$
Ozone $\left(\mathrm{O}_{3}\right)$
Nitrogen dioxide $\left(\mathrm{NO}_{2}\right)$

Recategorized: GATE ES 2021 | Question: 43

Mon, 21 Apr 2025 15:40:49 +0000

The concentration of $\mathrm{NO}_{2}$ in the air at $\mathrm{NTP}$ is reported as $0.30$ ppmv $\text{(ppm by volume)}$. The concentration of $\mathrm{NO}_{2} \mathrm{in} \mu \mathrm{g} / \mathrm{m}^{3} \mathrm{is}$ __________ $\text { (rounded off to the nearest integer). }$
[At NTP, temperature }=$298 \mathrm{~K}$, pressure =$1$ atm, and one mole of ideal gas occupies $24.45 \mathrm{L}$]
${\left[\text { Molecular weight of } \mathrm{NO}_{2}=46 \mathrm{~g} / \mathrm{mol}\right]}$