The USGS, in cooperation with the Maryland Department of the Environment, the Metropolitan Washington Council of Governments, and the Virginia Department of Environmental Quality, is also studying the amount of nutrient pollution that enters the Chesapeake Bay each year from its major tributaries. Excessive phosphorus runoff has long been recognized as associated with eutrophication of lakes and other nonflowing bodies of water. Eutrophication is the response of a body of water to enrichment by nutrients. The results include heavy growth of aquatic plants and algal mats and deoxygenation. Although industrial and sewage discharges of phosphate have been reduced greatly during the past 25 years, eutrophication remains a major environmental issue.
Most phosphorus enters bodies of water through soil erosion from agricultural lands.
Fertilizer production also is an environmental concern. For every ton of phosphoric acid produced, five tons of phosphogypsum are generated. Phosphogypsum is a solid material that results from the reaction of phosphate rock with sulfuric acid. Although it is nearly identical to natural gypsum, it may contain small amounts of sand, phosphate, fluorine, radium, and other elements present in phosphate ore. Federal regulations restrict both use and research involving phosphogypsum because of its radium content and require phosphogypsum to be stacked on the ground.