MChem Master of Chemistry Environmental Chemistry 3

Question 1

Which process in the nitrogen cycle converts nitrate (NO3−) back to N2 gas under anaerobic conditions?

Accepted Answer

Denitrification

Answer

Nitrification

Answer

Nitrogen fixation

Answer

Ammonification

Question 2

What are persistent organic pollutants (POPs) characterized by?

Accepted Answer

Resistance to degradation, lipophilicity, long-range transport, and toxicity

Answer

High water solubility and rapid biodegradation

Answer

Rapid photodegradation in surface waters

Answer

High volatility and short atmospheric lifetime

Question 3

In advanced oxidation processes (AOPs) for water treatment, what is the primary reactive species generated?

Accepted Answer

Hydroxyl radical (•OH)

Answer

Hydrogen peroxide (H2O2)

Answer

Hypochlorous acid (HOCl)

Answer

Ozone (O3) alone

Question 4

What is phytoremediation in environmental chemistry?

Accepted Answer

Use of plants to accumulate, degrade, or stabilize contaminants in soil or water

Answer

Chemical precipitation of heavy metals from wastewater

Answer

Microbial degradation of petroleum hydrocarbons

Answer

UV photodegradation of pesticides in surface soils

Question 5

What does the BOD (Biochemical Oxygen Demand) measurement indicate about a water sample?

Accepted Answer

The amount of oxygen consumed by microorganisms to degrade organic matter

Answer

The total dissolved oxygen concentration

Answer

The concentration of nitrate and phosphate nutrients

Answer

The pH buffering capacity of the water

Question 6

What chemical principle explains why mercury is particularly toxic in aquatic environments — specifically the methylation process?

Accepted Answer

Sulfate-reducing bacteria convert inorganic mercury to lipophilic methylmercury that bioaccumulates

Answer

Inorganic Hg2+ is more bioavailable than methylmercury

Answer

Mercury reacts with dissolved oxygen to form HgO nanoparticles

Answer

Mercury is absorbed only through direct contact with Hg0 vapor