UGC-NET (NTA) Environmental Sciences, June-2019

Total Questions: 100

71. Match List-I (Soil Type) with List-II (Degree of Compressibility):

List-I (Soil Type)List-II (Degree of Compressibility)
(a) Softy Clay(i) Low
(b) Clay(ii) High
(c) Silt(iii) Medium
(d) Sandy Clay(iv) Very High

Choose the correct answer from the options given below:

(a)(b)(c)(d)
A.(ii)(i)(iii)(iv)
B.(iv)(iii)(i)(ii)
C.(iii)(ii)(iv)(i)
D.(iv)(ii)(iii)(i)
Correct Answer: D.
Solution:

Identification of Fine-Grained Soil Fractions from Manual Test

72. Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R).

Assertion (A): Carbon dioxide content in soil air is more than atmospheric air.
Reason (R): Carbon dioxide released from automobile exhaust and industries gets sequestered in the soil.
Choose the correct answer from the options given below:

Correct Answer: C. (A) is true, but (R) is false
Solution:

The gaseous phase, or soil air, is a mixture of gases, and its content and composition are determined by soil-water-plant relationships. Whereas atmospheric air contains 20% oxygen, 0.03% carbon dioxide, and 78% nitrogen by volume, soil air tends to be lower in oxygen (<20%) and higher in carbon dioxide, (CO₂) content (>0.03%).

In soil air, the CO₂ content may be 10 times or considerably higher than that in atmospheric air. It can reach levels of 5% but can be as low as 0.3%. Soil air in direct contact with plant roots, generally in the form of films, often contains ≥90% CO₂.
Here Assertion (A) is true and Reason (R) is false.

73. Landslide incidences in the Himalayas have increased due to:

(a) Increased rainfall
(b) Deforestation
(c) Construction of new roads
Choose the correct option:

Correct Answer: B. (b) and (c) only
Solution:

Human impacts such as building construction, deforestation, and the collapse of agricultural terraces were associated with smaller landslides, while geological factors showed no significant correlations with landslide volume.

Road engineering factors such as the location of another road upslope and the collapse of roadcut retaining wall also proved unimportant. However, the height of the roadcut, channel incision undermining the roadcut and, especially, the steepness of the hillside upslope proved significant.

74. For a negatively skewed distribution, which is the correct relation?

Correct Answer: A. Arithmetic mean < Median < Mode
Solution:

A skewed distribution is one in which many more values fall on one side of the mean than on the other side of the mean. This imbalance creates a difference between the mean and the median. In a negatively skewed distribution, more values are above the mean, but the mean is lowered by some extremely low values below it.

Figure illustrates a negatively skewed distribution. Notice that most of the x-axis values in the distribution are at the high end, to the right, and the smaller number of extremely low values at the low end are pulling the mean to the left of the median. Thus, in a negatively skewed distribution, the tail is on the left, at the lower end of x-axis values.

75. Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R):

Assertion (A): Hydroxides of Aluminium (IIІ or Iron (III) are quite effective in removing colloidal clay particles from turbid water.
Reason (R): Hydroxides from positively charged flocs attract and carry down negatively charged colloidal clay particles.
Choose the correct answer from the options given below.

Correct Answer: A. Both (A) and (R) are true and (R) is the correct explanation of (A)
Solution:

Preliminary purification by flocculation is necessary, if the untreated water has a high turbidity, particularly as a result of colloidal or soluble organic impurities. Iron or aluminium salts are added to the water, so that iron(III) or aluminium hydroxide is precipitated:

Al₂(SO₄)₃+ 6 H₂O→ 2 Al(OH)₃↓+3 H₂SO₄
FeSO₄CI + 3 H₂O→ Fe(OH)₃↓+ H₂SO₄ + HCІ
Fe₂(SO₄)₃ + 6 H₂O→ 2 Fe(OH)₃+ 3 H₂SO₄

Hydroxyl from positively charged flocs attract and carry down negatively charged colloidal clay particles.

76. Cartagena Protocol deals with:

Correct Answer: D. Biosafety
Solution:

The Cartagena Protocol on Biosafety to the Convention on Biological Diversity is an international agreement which aims to ensure the safe handling, transport and use of living modified organisms (LMOs) resulting from modern biotechnology that may have adverse effects on biological diversity, taking also into account risks to human health.

It was adopted on 29 January 2000 and entered into force on 11 September 2003. The Protocol seeks to protect biological diversity from the potential risks posed by living modified organisms resulting from modern biotechnology.

It establishes an advance informed agreement (AIA) procedure for ensuring that countries are provided with the information necessary to make informed decisions before agreeing to the import of such organisms into their territory.

77. Which of the following parameters provides information on ignition quality of diesel?

Correct Answer: B. Cetane number
Solution:

Cetane number: An engine rating method is the only reliable method of determining the ignition quality of a diesel fuel.

Cetane has a low auto-ignition temperature of 202°C and a short ignition delay which ensures smooth combustion in a diesel engine. 1-MN has a high auto-ignition temperature of 529°C and a long ignition delay Heptamethylnonane has an auto-ignition temperature of 472°C and an ignition delay that is between cetane and 1-MN.

Cetane Index (CI): Cetane index is a calculated value, derived from fuel density and volatility. Cetane index usually gives a reasonably close approximation to real cetane number, which is derived from measurement in a real engine.

Cetane index is widely used for routine monitoring of diesel fuel ignition quality. The calculated cetane index has mainly served as an alternative method of determining the ignition quality of diesel fuel to minimize the need for engine tests.

78. A lake has 2.5 mgL⁻¹ of dissolved organic carbon. The dissolved organic matter concentration in the lake is approximately:

Correct Answer: B. 4.25 mgL⁻¹

79. Remote sensing data from which of the following remote sensing satellites is most suitable for urban ecological studies?

Correct Answer: B. CARTOSAT-2
Solution:

CARTOSAT-2 is a remote sensing satellite. Cartosat-2B weighed 694 kilograms at launch and is capable of steering its panchromatic camera up to plus or minus 26 degrees along its north-south and east-west axes to facilitate frequent imaging of any area in its field of view.

80. If x and y are two variables with independent frequency distributions with means μₓ and μᵧ and variances σₓ² and σᵧ² then the population variance of their difference σ²ₓ₋ᵧ is:

Correct Answer: A. σ²ₓ+ σ²ᵧ