In a process called phytoremediation, specific plants are planted in areas where toxic chemicals have contaminated groundwater. the roots absorb the contaminants to eliminate the tainted water, which is often drinking water. this is an example of

This is an example of bioaccumulation. This is when an organism accumulates substances, most often toxins such as pesticides or other chemicals. The accumulation takes place at a faster rather than the rate at which the substance is excreted or broken down. Plants are suitable for removing dissolved toxins in the ground because they take up water through their roots, and pure water vapour is lost through evapotranspiration, leaving the toxins behind. 

Idont really understand