A factory illegally dumps arsenic-rich wastewater into a lake,where the residence time of the arsenic is 10 years.If the dumping stops,after 30 years,the amount of arsenic in the lake will be one-third what it was when the dumping was stopped.

Question

Quizplus · Accepted Answer

The amount of arsenic in the lake will not decrease to one-third of its original level after 30 years, even if the dumping stops. This is because the residence time of arsenic in the lake is 10 years, meaning it takes 10 years for half of the arsenic to be removed through natural processes. After 30 years without further arsenic dumping, only one-eighth (2^-3) of the original amount of arsenic would remain in the lake.

A Factory Illegally Dumps Arsenic-Rich Wastewater into a Lake,where the Residence