Gerald Winegrad: These four pollution sources stand in the way of a better Chesapeake Bay

My last column focused on the urgency of curbing farm pollution, especially from thousands of tons of raw manure from 609 million Delmarva chickens. Let’s address the four other major sources of Bay pollutants — nitrogen, phosphorus, and sediment. These pollutants foul the Chesapeake Bay, threaten human health and lead to collapsed fisheries.