Given below are two statements: Statement I: Volatile Organic Chemicals (VOCs)…
2020
Given below are two statements: Statement I: Volatile Organic Chemicals (VOCs) are contaminants more commonly found in groundwater than in surface water Statement II: VOCs are one of the criterion parameters to determine drinking water quality
In light of the above statements, choose the correct answer from the options given below
- A.
Both Statement I and Statement II are true
- B.
Both Statement I and Statement II are false
- C.
Statement I is correct but Statement II is false
- D.
Statement I is incorrect but Statement II is true
Show answer & explanation
Correct answer: A
Concept
Volatile Organic Compounds (VOCs) are carbon-based chemicals (e.g., benzene, trichloroethylene, chloroform) with high vapour pressure, so they evaporate readily at ordinary temperatures. Their behaviour in water is governed by this volatility: at an open surface they escape into the air, but once they reach the subsurface they are shielded from the atmosphere and persist. In water-quality regulation, a "criterion parameter" is a constituent that has a defined limit (e.g., a Maximum Contaminant Level) used to judge whether water is safe to drink.
Applying it to the two statements
Statement I — where VOCs concentrate. In surface water, VOCs are continuously lost to the atmosphere by volatilization, so they tend not to accumulate. In groundwater there is no air interface, so VOCs are persistent and migrate toward supply wells. National monitoring (USGS NAWQA) detects VOCs in roughly one-third of sampled wells, and groundwater is treated as the primary VOC-contamination concern. Hence Statement I is true.
Statement II — VOCs as a water-quality criterion. Drinking-water regulators set enforceable limits for VOCs: about two dozen individual VOCs carry Maximum Contaminant Levels (for example benzene at 0.005 mg/L), and standard analytical methods exist to measure them in finished drinking water. A constituent with a regulatory limit used to certify potability is by definition a criterion parameter, so Statement II is true.
Cross-check / result
Both statements are independently supported by water-quality science and regulation, and Statement II does not contradict Statement I. Therefore both statements are true.