Asubstance has a half-life of 100,000 years and an initial mass of 1,000 grams. how many years will pass before only 250 grams of the substances parent material is left?

What is point source pollution of an aquatic ecosystem? a) pollution of freshwater sources b) pollution from many sources that combine into one c) pollution that occurs over a wide area; water that runs off from fields, parking lots, and other land surfaces d) pollution that can easily be identified with a single discharge source, such as an open pipe which drains into a body of water