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General Aptitude(10)Mathematics Foundation(9)Environmental Chemistry(3)Environmental Microbiology(6)Water Resources and Environmental Hydraulics(6)Water & Wastewater Treatment and Management(10)Air and Noise Pollution(9)Solid and Hazardous Waste Management(4)Global and Regional Environmental Issues(2)Environmental Management and Sustainable Development(6)

General Aptitude

10 Questions

GATE→2026→General Aptitude→Verbal Ability

Q1

MCQ[1 Mark]

Suresh said, "I did it yesterday." Which one of the following options is the correct form of this sentence in indirect speech?

(A)

Suresh said that I did it yesterday.

(B)

Suresh says I did it yesterday.

(C)

Suresh says that he did it the day before.

(D)

Suresh said that he had done it the day before.

Explanation

GATE→2026→General Aptitude→Quantitative Aptitude

Q2

MCQ[1 Mark]

To continue the sequence of tiles shown, the tile indicated by the question mark should be

(A)

Option (A)

(B)

Option (B)

(C)

Option (C)

(D)

Option (D)

Explanation

GATE→2026→General Aptitude→Quantitative Aptitude

Q3

MCQ[1 Mark]

Consider an art gallery whose walkways are shown as lines in the diagram. A black dot represents a junction of two walkways. A guard may be placed at a junction to watch over the walkways that join at that junction. The minimum number of guards needed to watch all the walkways is

(A)

2

(B)

3

(C)

4

(D)

5

Explanation

GATE→2026→General Aptitude→Quantitative Aptitude

Q4

MCQ[1 Mark]

The 2nd of June is a Thursday in a certain year. Which day of the week is the 3rd of July in that year?

(A)

Thursday

(B)

Friday

(C)

Saturday

(D)

Sunday

Explanation

GATE→2026→General Aptitude→Quantitative Aptitude

Q5

MCQ[1 Mark]

A coin with heads facing up is shown as H and a coin with tails facing up is shown as T. Six coins are placed in the Starting Arrangement, as shown in the figure below. A "step" is defined as interchanging a pair of adjacent coins without flipping them. The minimum number of steps needed to go from the Starting Arrangement to the Final Arrangement, as shown in the figure, is

(A)

3

(B)

6

(C)

9

(D)

12

Explanation

GATE→2026→General Aptitude→Verbal Ability

Q6

MCQ[2 Marks]

Exacerbate: Mitigate :: Choose the option with the correct pair of words to fill the blank.

(A)

Aggravate: Alleviate

(B)

Alleviate: Precipitate

(C)

Aggravate: Precipitate

(D)

Emancipate: Exonerate

Explanation

GATE→2026→General Aptitude→Quantitative Aptitude

Q7

MCQ[2 Marks]

A paper shown in Panel I is folded along the dashed lines to construct a cube. The shaded regions shown in Panel I appear on the outer surface of the cube. Referring to cubes shown in Panel II, which one of the options is correct?

(A)

Only (i) can correspond to the unfolded cube in Panel I.

(B)

(ii) can correspond to the unfolded cube in Panel I.

(C)

Both (i) and (ii) can correspond to the unfolded cube in Panel I.

(D)

Neither (i) nor (ii) can correspond to the unfolded cube in Panel I.

Explanation

GATE→2026→General Aptitude→Quantitative Aptitude

Q8

MCQ[2 Marks]

In a population, patients who have high cholesterol also have high blood-pressure (BP). Some patients with high BP also have diabetes. There are no patients who have both high cholesterol and diabetes. Furthermore, 1. the total number of patients with at least one of these conditions is 75, 2. the number of patients with high cholesterol is 10, 3. the number of patients with high BP is 45, and 4. the number of patients with only high BP and no other conditions is 20. Then the number of patients who have both diabetes and high BP is

(A)

0

(B)

15

(C)

20

(D)

10

Explanation

GATE→2026→General Aptitude→Quantitative Aptitude

Q9

MCQ[2 Marks]

Four people P, Q, R, and S, of different ages, make the following observations. P: I am younger than S. Q: I am neither the youngest nor the oldest. R: P is older than me. Based on these observations, the youngest person is

(A)

P

(B)

Q

(C)

R

(D)

S

Explanation

GATE→2026→General Aptitude→Quantitative Aptitude

Q10

MCQ[2 Marks]

Circles $C_1$, $C_2$, and $C_3$, with centers $O_1$, $O_2$, and $O_3$, and radii $r_1$, $r_2$ and $r_3$, respectively, touch each other as shown in the following figure. Given $r_1 = 2$ cm, $r_2 = 1$ cm and the angle $\angle O_1O_3O_2$ is $90^\circ$, $r_3 =$ ____ cm.

(A)

\frac{1}{2}(-3+\sqrt{17})

(B)

\frac{1}{2}(3+\sqrt{17})

(C)

\frac{1}{2}(-2+\sqrt{17})

(D)

\frac{1}{2}(-3+2\sqrt{17})

Explanation

Mathematics Foundation

9 Questions

GATE→2026→Mathematics Foundation→Linear Algebra

Q11

MCQ[1 Mark]

If $2X + \begin{bmatrix} 1 & 2 \\ 3 & 4 \end{bmatrix} = \begin{bmatrix} 3 & 8 \\ 7 & 2 \end{bmatrix}$, then $X$ is

(A)

\begin{bmatrix} 2 & 5 \\ 5 & 3 \end{bmatrix}

(B)

\begin{bmatrix} -1 & 3 \\ 2 & -1 \end{bmatrix}

(C)

\begin{bmatrix} 1 & 3 \\ 2 & -1 \end{bmatrix}

(D)

\begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix}

Explanation

GATE→2026→Mathematics Foundation→Calculus

Q12

MCQ[1 Mark]

The correct integral of $\int \frac{\sin x}{\sqrt{1+\cos x}} dx$ (assuming integral constant as $c$) is

(A)

$-2\sqrt{2} \sin\left(\frac{x}{2}\right) + c$

(B)

$-2\sqrt{2} \cos\left(\frac{x}{2}\right) + c$

(C)

$-\frac{1}{\sqrt{2}} \cos\left(\frac{x}{2}\right) + c$

(D)

$-\frac{1}{\sqrt{2}} \sin\left(\frac{x}{2}\right) + c$

Explanation

GATE→2026→Mathematics Foundation→Calculus

Q13

MCQ[1 Mark]

Given $f(x) = 3x^4 + 4x^3 - 12x^2 + 6$, the minimum value of $f(x)$ is

(A)

-6

(B)

-36

(C)

-26

(D)

-46

Explanation

GATE→2026→Mathematics Foundation→Probability and Statistics

Q14

MCQ[1 Mark]

A box contains 26 cards with all English alphabets from A to Z. The probability of randomly choosing the card with either 'E' or 'S' from this box is

(A)

2/26

(B)

1/26

(C)

3/26

(D)

4/26

Explanation

GATE→2026→Mathematics Foundation→Probability and Statistics

Q15

MCQ[1 Mark]

Which ONE of the following options is the CORRECT formula for Chi-Square ($\chi^2$) test?

(A)

$\chi^2 = \sum_{i=1}^{n}\frac{(O_i-E_i)^{2}}{E_i}$

(B)

$\chi^2 = \sqrt{\frac{\sum_{i=1}^{n}(O_i-\overline{O})^{2}}{n-1}}$

(C)

$\chi^2 = \frac{\overline{O}-\mu}{\sigma_o\sqrt{n}}$

(D)

$\chi^2 = \frac{(\sigma_o)^{2}}{(\sigma_E)^{2}}$

Explanation

GATE→2026→Mathematics Foundation→Calculus

Q16

MCQ[2 Marks]

A first-order ordinary differential equation is given as follows: $\frac{dy}{dx} + x^2y = 0$. Which ONE of the following options CORRECTLY represents the characteristics of this equation?

(A)

Linear, homogeneous, and exact

(B)

Nonlinear, nonhomogeneous, and exact

(C)

Linear, homogeneous, and non-exact

(D)

Nonlinear, nonhomogeneous, and non-exact

Explanation

GATE→2026→Mathematics Foundation→Linear Algebra

Q17

MCQ[2 Marks]

Consider the matrix $A = \begin{bmatrix} 2 & 2 & 3 \\ 2 & 5 & 6 \\ 3 & 4 & 10 \end{bmatrix}$. Which ONE of the following options CORRECTLY lists the eigenvalues of A?

(A)

$1; 8-\sqrt{37}; -8+\sqrt{37}$

(B)

$2; 8-\sqrt{37}; -8+\sqrt{37}$

(C)

$1; 8+\sqrt{37}; 8-\sqrt{37}$

(D)

$2; 8+\sqrt{37}; 8+\sqrt{37}$

Explanation

GATE→2026→Mathematics Foundation→Linear Algebra

Q18

MSQ[2 Marks]

A system of linear equations is given as $AX = B$, where $A = \begin{bmatrix} 2 & 5 \\ 5 & -2 \end{bmatrix}$, $B = \begin{bmatrix} 7 \\ 3 \end{bmatrix}$ and $X$ is the solution vector. Which of the following statements is/are TRUE for this system?

(A)

Matrix A is skew-symmetric.

(B)

Eigenvalues of matrix A are real.

(C)

The system is homogeneous.

(D)

The system is singular.

Explanation

GATE→2026→Mathematics Foundation→Calculus

Q19

NAT[2 Marks]

The area in the first quadrant bounded by the function $y = 8 - x$ and the coordinate axes is _____ square units (answer in integer).

Explanation

Environmental Chemistry

3 Questions

GATE→2026→Environmental Chemistry→Fundamentals of Environmental Chemistry

Q20

MCQ[1 Mark]

In the reversible reaction shown below, $k_f$ is the forward reaction rate constant and $k_r$ is the reverse reaction rate constant. $A + B \rightleftharpoons C + D$ The CORRECT expression representing the reaction equilibrium constant is

(A)

$k_f + k_r$

(B)

$k_f \times k_r$

(C)

\frac{k_f}{k_r}

(D)

\frac{k_r}{k_f}

Explanation

GATE→2026→Environmental Chemistry→Atmospheric Chemistry

Q21

MSQ[1 Mark]

Which of the following chemical reactions is/are related to smog formation in the troposphere?

(A)

$CFCl_3 + h\nu \rightarrow CFCl_2 + Cl\cdot$

(B)

$CH_3O_2 + NO + O_2 \rightarrow HCHO + HO_2 + NO_2$

(C)

$NO_2 + O_2 + h\nu \rightarrow O_3 + NO$

(D)

$CH_4 + 8O_2 \rightarrow CO + H_2O + 2OH\cdot + 4O_3$

Explanation

GATE→2026→Environmental Chemistry→Principles of Water Chemistry

Q22

NAT[2 Marks]

The following two reactions describe the chemistry of S(IV) in an aquatic system. (i) $SO_{2(aq)} \rightleftharpoons H^+ + HSO_3^-$ ($K_{S1} = 1.3 \times 10^{-2}\text{ M}$) (ii) $HSO_3^- \rightleftharpoons H^+ + SO_3^{2-}$ ($K_{S2} = 6.6 \times 10^{-8}\text{ M}$) If the $\text{pH}$ of the system is $4.0$ and the equilibrium concentration of $SO_{2(aq)}$ is $1.0\text{ M}$, the equilibrium concentration of $SO_3^{2-}$ is _____ mM (rounded off to one decimal place).

Explanation

Environmental Microbiology

6 Questions

GATE→2026→Environmental Microbiology→Microbial Metabolism

Q23

MCQ[1 Mark]

The major class of enzymes catalyzing the cleavage of C-C, C-O, C-N, or other bonds by elimination, leaving double bonds or rings, or addition of groups to double bonds in any biochemical reactions is

(A)

lyases

(B)

transferases

(C)

oxidoreductases

(D)

hydrolases

Explanation

GATE→2026→Environmental Microbiology→Microbiology and Health

Q24

MCQ[1 Mark]

Malaria is caused by pathogenic

(A)

bacteria

(B)

fungi

(C)

protozoa

(D)

viruses

Explanation

GATE→2026→Environmental Microbiology→Cell Chemistry and Cell Biology

Q25

MCQ[2 Marks]

Which ONE of the following options is CORRECT with respect to sequential breakdown of deoxyribonucleic acid (DNA) into lower-molecular weight compounds?

(A)

Deoxyribonucleic acid $\rightarrow$ 2-deoxyribose $\rightarrow$ Nucleosides $\rightarrow$ Nucleotides

(B)

Deoxyribonucleic acid $\rightarrow$ 2-deoxyribose $\rightarrow$ Nucleotides $\rightarrow$ Nucleosides

(C)

Deoxyribonucleic acid $\rightarrow$ Nucleotides $\rightarrow$ Nucleosides $\rightarrow$ 2-deoxyribose

(D)

Deoxyribonucleic acid $\rightarrow$ Nucleosides $\rightarrow$ Nucleotides $\rightarrow$ 2-deoxyribose

Explanation

GATE→2026→Environmental Microbiology→Microbial Metabolism

Q26

MSQ[2 Marks]

Which of the following statements is/are CORRECT based on the electron donor (ED) and electron acceptor (EA) used in various bacterial mediated reactions in wastewater treatment?

(A)

In anaerobic heterotrophic acid fermentation, organic compounds are used as both ED and EA.

(B)

In anaerobic heterotrophic methanogenesis, volatile fatty acids and CO2 are used as ED and EA, respectively.

(C)

In denitrification process by denitrifiers, organic compounds and CO2 are used as ED and EA, respectively.

(D)

In aerobic autotrophic iron oxidation, Fe(II) and O2 are used as ED and EA, respectively.

Explanation

GATE→2026→Environmental Microbiology→Growth and Control of Microorganisms

Q27

NAT[2 Marks]

In a batch culture experiment, 2 cells of a microorganism were added to a growth medium. During the experiment, a lag phase of 1 hour was first experienced by the added cells, in which no cell multiplication occurred. Afterwards, cells started multiplying exponentially with a doubling time of 1 hour. After total 8 hours of experiment, the number of cells present in the growth medium was _____ (answer in integer).

Explanation

GATE→2026→Environmental Microbiology→Growth and Control of Microorganisms

Q28

NAT[2 Marks]

A thermal process, at a specific temperature, results in 2-log10 removal of non-thermotolerant pathogenic microorganisms from a water sample in 20 min. The time needed to achieve 99.999% removal of these microorganisms under similar condition is _____ min (answer in integer).

Explanation

Water Resources and Environmental Hydraulics

6 Questions

GATE→2026→Water Resources and Environmental Hydraulics→Environmental Hydraulics

Q29

MCQ[1 Mark]

Consider the following statements regarding the pressure measured at a point in a fluid. S1: Absolute pressure is gauge pressure plus atmospheric pressure. S2: Gauge pressure is measured by considering absolute zero pressure as datum. S3: Absolute pressure is measured by considering atmospheric pressure as datum. S4: Vacuum pressure is negative pressure obtained by subtracting absolute pressure from atmospheric pressure. Which ONE of the following options lists all the TRUE statements?

(A)

S1 and S2

(B)

S2 and S3

(C)

S1 and S4

(D)

S1, S2, and S4

Explanation

GATE→2026→Water Resources and Environmental Hydraulics→Surface Water Resources

Q30

NAT[1 Mark]

A 6-hour rainfall of 6 cm at a station was found to have a return period of 40 years. The probability that a 6-hour rainfall of this or larger magnitude will occur at least once in 20 successive years at that station is _____ (rounded off to three decimal places).

Explanation

GATE→2026→Water Resources and Environmental Hydraulics→Environmental Hydraulics

Q31

NAT[1 Mark]

Water is flowing at the rate of $15\text{ m}^3/\text{s}$ through a rectangular channel of $5\text{ m}$ width. If the acceleration due to gravity ($g$) is $9.81\text{ m/s}^2$, the critical velocity for the flow is _____ m/s (rounded off to three decimal places).

Explanation

GATE→2026→Water Resources and Environmental Hydraulics→Environmental Hydraulics

Q32

NAT[2 Marks]

A cylindrical roller gate of diameter $6.0\text{ m}$ and length $10.0\text{ m}$ is placed on a dam to store water behind it, as shown in figure. The magnitude of the resultant force due to water acting on that gate when the water is about to spill is _____ $\times 10^6\text{ N}$ (rounded off to two decimal places). (Consider $g = 9.81\text{ m/s}^2$, $\rho = 1000\text{ kg/m}^3$, $\pi = 3.14$)

Explanation

GATE→2026→Water Resources and Environmental Hydraulics→Surface Water Resources

Q33

NAT[2 Marks]

The mass curve of a rainfall event of $100\text{ min}$ duration over a catchment is given in the table. If the initial loss is $0.6\text{ cm}$ and $W$-index is $0.6\text{ cm/hour}$, the total surface runoff from the catchment is _____ cm (rounded off to one decimal place). Time (min): 0, 20, 40, 60, 80, 100 Cumulative rainfall (cm): 0, 0.5, 1.2, 2.6, 3.3, 3.5

Explanation

GATE→2026→Water Resources and Environmental Hydraulics→Groundwater Resources

Q34

NAT[2 Marks]

A well penetrates an unconfined aquifer. The water level (head) in the well prior to pumping is $25\text{ m}$. After a long period of pumping at a constant rate of $Q = 0.05\text{ m}^3/\text{s}$, the drawdowns at distances of $r_1 = 50\text{ m}$ and $r_2 = 150\text{ m}$ from the well are observed to be $s_1 = 3\text{ m}$ and $s_2 = 1.2\text{ m}$, respectively. The hydraulic conductivity of the unconfined aquifer is _____ $\times 10^{-4}\text{ m/s}$ (rounded off to two decimal places). ($\pi = 3.14$)

Explanation

Water & Wastewater Treatment and Management

10 Questions

GATE→2026→Water & Wastewater Treatment and Management→Sewage Treatment, Sludge & Wastewater Management

Q35

MCQ[1 Mark]

Which ONE of the following options CORRECTLY matches the processes associated with the growth condition given in the table?

(A)

(P) - (ii); (Q) - (iii); (R) - (iv); (S) - (i)

(B)

(P) - (iii); (Q) - (ii); (R) - (iv); (S) - (i)

(C)

(P) - (iii); (Q) - (i); (R) - (iv); (S) - (ii)

(D)

(P) - (iv); (Q) - (iii); (R) - (ii); (S) - (i)

Explanation

GATE→2026→Water & Wastewater Treatment and Management→Sewage Treatment, Sludge & Wastewater Management

Q36

MSQ[1 Mark]

Which of the following processes is/are primarily used to remove the organic matter in sludge?

(A)

Digestion

(B)

Incineration

(C)

Magnetic separation

(D)

Wet-oxidation

Explanation

GATE→2026→Water & Wastewater Treatment and Management→Water and Wastewater Quality Parameters & River Pollution

Q37

MSQ[1 Mark]

Which of the following options is/are CORRECTLY listing the species included in Total Kjeldahl Nitrogen (TKN) estimation of an aqueous sample?

(A)

Ammoniacal - N

(B)

Nitrite - N

(C)

Nitrate - N

(D)

Organic - N

Explanation

GATE→2026→Water & Wastewater Treatment and Management→Water and Wastewater Quality Parameters & River Pollution

Q38

MCQ[2 Marks]

The analysis of a water sample is shown in the table. The hardness of the water sample is _____ mg/L as $CaCO_3$. Atomic weight (g/mol): $Ca=40$, $Mg=24$, $Na=23$, $Cl=35.5$, $S=32$, $O=16$, $N=14$. Species Concentration (mg/L): $Na^+ = 30$, $Ca^{2+} = 10$, $Mg^{2+} = 15$, $Cl^- = 30$, $SO_4^{2-} = 60$, $NO_3^- = 5$.

(A)

87.5

(B)

62.5

(C)

25.5

(D)

47.5

Explanation

GATE→2026→Water & Wastewater Treatment and Management→Water Treatment Methods & Distribution

Q39

MSQ[2 Marks]

Which of the following options is/are TRUE about reverse osmosis process?

(A)

Reverse osmosis is used as a pretreatment for microfiltration process.

(B)

Ultrafiltration is used as a pretreatment for reverse osmosis process.

(C)

Membrane fouling occurs in microfiltration and reverse osmosis processes.

(D)

Concentration polarization does not occur in reverse osmosis process.

Explanation

GATE→2026→Water & Wastewater Treatment and Management→Water Treatment Methods & Distribution

Q40

MSQ[2 Marks]

Which of the following options is/are TRUE about coagulation-flocculation process?

(A)

Collision of colloidal particles due to their Brownian motion results in orthokinetic flocculation.

(B)

Collision of colloidal particles due to the external mixing of bulk medium results only in perikinetic flocculation.

(C)

In an electric double layer model of a colloidal particle, Stern layer is more compact than the diffuse layer.

(D)

The zeta potential is also called Stern potential.

Explanation

GATE→2026→Water & Wastewater Treatment and Management→Kinetics and Reactor Design

Q41

NAT[2 Marks]

Reaction $A \rightarrow B$ follows first-order elementary kinetics and the reaction rate constant for A is $0.01\text{ min}^{-1}$. The time taken to reduce the concentration of A from $100\text{ M}$ to $10\text{ M}$ in a batch reactor is _____ min (rounded off to one decimal place).

Explanation

GATE→2026→Water & Wastewater Treatment and Management→Water and Wastewater Quality Parameters & River Pollution

Q42

NAT[2 Marks]

The calibration graph between absorbance and the concentration of chromate ($CrO_4^{2-}$) in a water sample is given by the equation $y = 0.8003x + 0.0055$. For an absorbance of $0.35$ in a water sample, the estimated $Cr(VI)$ concentration is _____ mg/L (rounded off to two decimal places). (Atomic weights: $Cr = 52$, $O = 16$)

Explanation

GATE→2026→Water & Wastewater Treatment and Management→Sewage Treatment, Sludge & Wastewater Management

Q43

NAT[2 Marks]

A sewage treatment plant employing activated sludge process is operated under the following conditions: - Wastewater flow rate ($Q$) = $0.150\text{ m}^3/\text{s}$ - Soluble $BOD_5$ in influent ($S_0$) = $84\text{ mg/L}$ - Soluble $BOD_5$ in effluent ($S$) = $11\text{ mg/L}$ - Mean cell residence time ($\theta_c$) = $5\text{ days}$ - Total yield coefficient ($Y$) = $0.5\text{ kg MLVSS/kg } BOD_5$ removed - Decay rate ($k_d$) = $0.050\text{ day}^{-1}$ The net waste activated sludge produced in the plant is _____ $\text{kg VSS/day}$ (rounded off to two decimal places).

Explanation

GATE→2026→Water & Wastewater Treatment and Management→Kinetics and Reactor Design

Q44

NAT[2 Marks]

A continuous flow stirred tank reactor (CSTR) operates under a steady-state condition with a flow rate of $Q = 300\text{ L/hour}$. The influent concentration of a substrate entering the reactor is $S_0 = 150\text{ mg/L}$. To give a treatment efficiency of $76\%$ for the substrate that decays according to half-order kinetics with a rate constant $k = 0.05\text{ (mg/L)}^{1/2}\text{ hr}^{-1}$, the required volume of the reactor is _____ $\text{m}^3$ (answer in integer).

Explanation

Air and Noise Pollution

9 Questions

GATE→2026→Air and Noise Pollution→Particulate Pollutants: Measurement and Control

Q45

MCQ[1 Mark]

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

(A)

mean size

(B)

mode size

(C)

cut size

(D)

median size

Explanation

GATE→2026→Air and Noise Pollution→Atmospheric Processes and Air Quality Parameters

Q46

MCQ[1 Mark]

The general atmospheric composition of gases in the decreasing order is

(A)

$N_2 > O_2 > CO > CO_2 > NH_3$

(B)

$N_2 > O_2 > CO_2 > CO > NH_3$

(C)

$N_2 > CO_2 > O_2 > NH_3 > CO$

(D)

$N_2 > CO_2 > NH_3 > CO > O_2$

Explanation

GATE→2026→Air and Noise Pollution→Atmospheric Processes and Air Quality Parameters

Q47

MCQ[2 Marks]

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

(A)

(P) - (i); (Q) - (ii); (R) - (iii); (S) - (iv)

(B)

(P) - (iv); (Q) - (iii); (R) - (ii); (S) - (i)

(C)

(P) - (iii); (Q) - (i); (R) - (iv); (S) - (ii)

(D)

(P) - (ii); (Q) - (iii); (R) - (i); (S) - (iv)

Explanation

GATE→2026→Air and Noise Pollution→Air Quality Management and Dispersion Modelling

Q48

MCQ[2 Marks]

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

(A)

(P) - (i); (Q) - (ii); (R) - (iii); (S) - (iv)

(B)

(P) - (iv); (Q) - (iii); (R) - (ii); (S) - (i)

(C)

(P) - (iii); (Q) - (iv); (R) - (ii); (S) - (i)

(D)

(P) - (ii); (Q) - (i); (R) - (iv); (S) - (iii)

Explanation

GATE→2026→Air and Noise Pollution→Air Quality Management and Dispersion Modelling

Q49

MSQ[2 Marks]

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

(A)

The concentration of pollutants emitting from stack is continuous.

(B)

The process is under steady state.

(C)

The pollutants emitted are non-conservative.

(D)

The diffusion of pollutants is dominant in comparison with advection in the direction of wind.

Explanation

GATE→2026→Air and Noise Pollution→Noise Pollution

Q50

NAT[2 Marks]

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). Location: A (40 dBA), B (65 dBA), C (55 dBA), D (75 dBA)

Explanation

GATE→2026→Air and Noise Pollution→Atmospheric Processes and Air Quality Parameters

Q51

NAT[2 Marks]

Standard deviation for the particulate matter (PM) concentrations listed in the table is _____ $\mu\text{g/m}^3$ (rounded off to one decimal place). Locations (1 to 7): 65, 45, 55, 60, 40, 50, 35

Explanation

GATE→2026→Air and Noise Pollution→Atmospheric Processes and Air Quality Parameters

Q52

NAT[2 Marks]

The mixing ratio of $CO_2$ at a pressure of 1 atm and at 300K is reported as 340 ppmv. Considering ideal gas conditions, the equivalent concentration of $CO_2$ in air is _____ $\text{mg/m}^3$ (rounded off to two decimal places). (Molecular weight of $CO_2 = 44\text{ g/mol}$; Universal gas constant $= 8.314\text{ J/mol-K}$; $1\text{ atm} = 101325\text{ Pa}$)

Explanation

GATE→2026→Air and Noise Pollution→Atmospheric Processes and Air Quality Parameters

Q53

NAT[2 Marks]

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 $SO_2$ concentrations through these sectors at this height are given in the table. The mean $SO_2$ concentration from the stack is _____ $\text{mg/m}^3$ (rounded off to two decimal places). Sector 1: $v = 15\text{ m/s}$, $C = 1000\text{ mg/m}^3$ Sector 2: $v = 17\text{ m/s}$, $C = 1150\text{ mg/m}^3$ Sector 3: $v = 19\text{ m/s}$, $C = 1250\text{ mg/m}^3$ Sector 4: $v = 21\text{ m/s}$, $C = 1275\text{ mg/m}^3$

Explanation

Solid and Hazardous Waste Management

4 Questions

GATE→2026→Solid and Hazardous Waste Management→Integrated Solid Waste Management & Municipal Waste

Q54

MCQ[1 Mark]

Which ONE of the following options is NOT a parameter as a part of proximate analysis of municipal solid waste?

(A)

Volatile matter

(B)

Ash content

(C)

Carbon to nitrogen ratio

(D)

Moisture content

Explanation

GATE→2026→Solid and Hazardous Waste Management→Hazardous Waste Management and Soil Contamination

Q55

MSQ[1 Mark]

Which of the following statements is/are CORRECT in the context of hazardous waste management and its risk assessment?

(A)

Risk is estimated based on the probability of an action occurring multiplied by the severity of damage.

(B)

High octanol water constant (Kow) is indicative of lower accumulation of an organic chemical in body tissue.

(C)

Pump and treat is an example of contaminated groundwater remediation.

(D)

Biological treatment processes are never applied for hazardous waste management.

Explanation

GATE→2026→Solid and Hazardous Waste Management→Integrated Solid Waste Management & Municipal Waste

Q56

NAT[2 Marks]

An anaerobic digestion system is operated for methane gas generation from organic fraction of municipal solid waste (OFMSW). - Moisture content = $20\%$ - Volatile solids (VS) content = $90\%$ (on dry basis) - Biodegradable volatile solids (BVS) in VS = $70\%$ - BVS conversion efficiency to methane = $85\%$ - Methane gas generation rate = $12\text{ m}^3$ per kg of BVS converted The total volume of methane gas produced from one kilogram of OFMSW is _____ $\text{m}^3$ (rounded off to two decimal places).

Explanation

GATE→2026→Solid and Hazardous Waste Management→Integrated Solid Waste Management & Municipal Waste

Q57

NAT[2 Marks]

The characteristics of two types of solid waste are given in the table. The quantity of sludge to be added to leaves to achieve a C/N ratio of 25 (on dry basis) for the mixed waste is _____ kg of sludge/kg of leaves (rounded off to three decimal places). - Leaves: Moisture = $0.7$, C/N ratio = $50$, Nitrogen content = $50\%$ - Sludge: Moisture = $6.3$?, C/N ratio = $75$, Nitrogen content = $5.6\%$

Explanation

Global and Regional Environmental Issues

2 Questions

GATE→2026→Global and Regional Environmental Issues→Ecology, Biodiversity & Population Growth

Q58

MCQ[1 Mark]

A species whose impact on an ecosystem is disproportionately large in comparison to its population is called _____ species.

(A)

dominant

(B)

keystone

(C)

apex predator

(D)

endemic

Explanation

GATE→2026→Global and Regional Environmental Issues→Global Effects of Air Pollution & Climate Change

Q59

MSQ[1 Mark]

Which of the following statements is/are TRUE about global warming?

(A)

Interception of incoming solar radiation by greenhouse gases in earth's atmosphere is responsible for global warming.

(B)

Interception of outgoing longwave radiation by greenhouse gases in earth's atmosphere is responsible for global warming.

(C)

Global warming can cause sea level rise.

(D)

Carbon dioxide is one of the major greenhouse gases in earth's atmosphere responsible for global warming.

Explanation

Environmental Management and Sustainable Development

6 Questions

GATE→2026→Environmental Management and Sustainable Development→Environmental Law, Policy, and Treaties

Q60

MCQ[1 Mark]

Which ONE of the following principles is directly related to environmental compensation?

(A)

Intergenerational equity principle

(B)

Precautionary principle

(C)

Subsidiarity principle

(D)

Polluter-pay principle

Explanation

GATE→2026→Environmental Management and Sustainable Development→Sustainable Development and Economics

Q61

MCQ[1 Mark]

As per the United Nations General Assembly resolution adopted in 2015 "Transforming Our World: The 2030 Agenda for Sustainable Development", the number of sustainable development goals (SDGs) is

(A)

4

(B)

15

(C)

17

(D)

11

Explanation

GATE→2026→Environmental Management and Sustainable Development→Environmental Management Systems & Impact Assessment

Q62

MCQ[1 Mark]

Which ONE of the following options CORRECTLY matches the ISO series with their usages in environmental management system (EMS) given in the table?

(A)

(P) - (i); (Q) - (ii); (R) - (iii); (S) - (iv)

(B)

(P) - (ii); (Q) - (i); (R) - (iv); (S) - (iii)

(C)

(P) - (iii); (Q) - (iv); (R) - (i); (S) - (ii)

(D)

(P) - (iv); (Q) - (iii); (R) - (ii); (S) - (i)

Explanation

GATE→2026→Environmental Management and Sustainable Development→Environmental Management Systems & Impact Assessment

Q63

MSQ[1 Mark]

Which of the following options is/are directly associated with the steps involved in carrying out life cycle assessment (LCA)?

(A)

Determination of functional unit

(B)

Defining goal and scope

(C)

Defining technology readiness level

(D)

Listing out inventory of inputs and outputs

Explanation

GATE→2026→Environmental Management and Sustainable Development→Environmental Management Systems & Impact Assessment

Q64

NAT[2 Marks]

The concentration of chemical A in ambient air is $50\text{ }\mu\text{g/m}^3$ and the toxicological index limit for a threshold health effect for this chemical is $5\text{ mg}$. If the average breathing rate is $4\text{ L/min}$, the minimum time of exposure that can lead to any health effect is _____ days (rounded off to one decimal place).

Explanation

GATE→2026→Environmental Management and Sustainable Development→Energy and Environment

Q65

NAT[2 Marks]

An agricultural land can support energy crops yield to produce $7000\text{ L}$ of bioethanol per hectare and energy content of bioethanol is $21\text{ MJ/L}$. This bioethanol displaces fossil-based petrol. The $CO_2$ offset potential of land used for growing energy crops as a bioethanol feedstock is _____ $\times 10^6\text{ g of } CO_2\text{/hectare}$ (rounded off to one decimal place). ($CO_2$ footprints: $10\text{ g}$ and $80\text{ g of } CO_2\text{ per MJ}$ for bioethanol and petrol, respectively)

Explanation