How do wetlands remove nutrients and toxic waste?

The way I understand it, wetlands have a lot of trees. Trees and other plants absorb carbon dioxode (what humans breath out) and emit oxygen (what humans breath). This is why people have fewer allergies and are generally healthier whe they have large leafed house plants in their homes. There are 2 parts to this question. The plants in the wetlands use the nutrients and thus sequester them. Wetlands, as are most environments, are full of bacteria. Many of these bacteria perform specific functions; some fix nitrogen (nutrients), while others perform functions such as breaking down heavy metals (toxic wastes). Studies at the Colorado School of Mines have shown that constructed wetlands can remove heavy metals from streams ("acid mine drainage"), a big problem in the Rocky Mountains.