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.
What body systems main function is to carry oxygen and nutrients to the tissues and remove waste from them?
Yes, the respiratory system removes waste. Besides providing oxygen to the lung and the cells of a body during inhalation, they also provide some nutrients as well. Therefore when a person is exhaling, carbon dioxide is picked up from the cells along with waste (unused or used nutrients) and is breathed out.
Many different things have been done with toxic waste of various types. Some businesses have discharged their toxic waste in rivers, which flow into the ocean, or have discharged waste into the ocean directly; mercury in particular has been a problem in this regard, and now the fish in the ocean are contaminated with mercury, and if you eat fish, you are going to eat some of this toxic waste, that was eaten (or absorbed)…