GATE Overflow for GATE ESE - Recent activity in Gaseous Pollutants

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: 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: 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 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: 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: 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 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: 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: 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 $24.45 \mathrm{L}$]
${\left[\text { Molecular weight of } \mathrm{NO}_{2}=46 \mathrm{~g} / \mathrm{mol}\right]}$