Madeline Schreiber of Virginia Tech pulls sediment samples from the Dan River in Danville, Va., in 2014.
Madeline Schreiber of Virginia Tech pulls sediment samples from the Dan River in Danville, Va., in 2014. Erica Yoon AP
Madeline Schreiber of Virginia Tech pulls sediment samples from the Dan River in Danville, Va., in 2014. Erica Yoon AP