Which statement describes wetlands' role in redox processes and contaminant degradation?

• A. Wetlands worsen redox processes by increasing salinity.
• B. Wetlands support redox processes that degrade contaminants, helping purification.
• C. Wetlands do not affect redox or degradation.
• D. Wetlands only store water, not affecting chemistry.

Answer: (B)

Wetlands create conditions that invite microbes to drive redox reactions, which break down contaminants. In waterlogged soils, oxygen is scarce, so microbes use other electron acceptors such as nitrate, iron, manganese, sulfate, or carbon dioxide. As these redox-driven processes proceed, many pollutants are transformed or degraded into less harmful forms, effectively purifying the water. Plant roots also contribute by releasing some oxygen into the surrounding soil (the rhizosphere), creating small zones where aerobic degradation can occur. This combination makes wetlands natural systems for contaminant attenuation through redox chemistry and microbial activity. The statement capturing this—that wetlands support redox processes that degrade contaminants, aiding purification—is the best description. The other options imply incorrect or incomplete roles, such as not affecting redox at all or merely storing water, which isn’t accurate for wetlands’ chemistry.