How do wetlands contribute to environmental chemistry and water purification?

• A. Wetlands filter pollutants, trap sediments, sequester nutrients, and support redox processes that degrade contaminants.
• B. Wetlands increase nutrient levels by concentrating fertilizers.
• C. Wetlands mainly store water without affecting chemistry.
• D. Wetlands prevent all microbial activity.

Answer: (A)

Wetlands act as natural water purifiers by combining physical, chemical, and biological processes. They physically slow and filter water, allowing sediments and attached pollutants to settle out and become trapped in the sediment and plant matter. They also remove substances through chemical interactions: nutrients like phosphorus can bind to minerals in the sediment, and metals may immobilize or precipitate, reducing their mobility. Plants contribute by taking up nutrients and some contaminants, while the surrounding microbial communities drive redox reactions that transform and degrade pollutants. In the waterlogged, low-oxygen environment, microbes perform processes such as denitrification, which converts nitrates to nitrogen gas, effectively removing nitrogen from the water. These together lead to cleaner water leaving the wetland and reduced pollution downstream.