The Patuxent River -- the largest river solely within the borders of Maryland -- is showing a noticeable improvement in water quality, according to state environmental officials, who plan to present their findings to the biennial Chesapeake Research Conference in Baltimore today.
The improvement bodes well for the state's goal of reducing by 40 percent the amount of damaging nutrients entering the Chesapeake Bay, they say.
Since 1983, environmental officials have been monitoring phosphorus and nitrogen in the Patuxent at 14 stations along the river. The two chemicals -- which are found in many fertilizers and most sewage -- are responsible for increased aquatic algae growth. That growth begins a process that ends up literally smothering the bay of oxygen and making it inhospitable for plants and fish.
By the 1970s, the Patuxent, situated in the middle of the fast-growing Baltimore-Washington corridor, had become one of the most polluted tributaries of the bay, Robert Magnien, chief of bay programs for the Maryland Department of the Environment, said yesterday.
The nutrients came from a variety of sources, but most noticeably from sewage treatment plants and runoff from farms and residences, he noted.
Alarmed, the state instituted a number of tough runoff-control actions in 1982 and a ban on phosphate detergents in 1985. About that time, sewage treatment plants began to be upgraded to remove phosphorus.
The state also instituted tougher sediment control laws to stop ,, runoff from construction sites and other areas of intense development.
The result was a decline of approximately 20 percent in $l phosphorus emissions into the bay from runoff and a dramatic 75 percent decline from sewage plants.
The numbers look more positive when placed against the backdrop of the continued rapid growth of the counties surrounding the Patuxent -- Howard, Anne Arundel, Montgomery, Prince George's, Calvert, Charles and St. Mary's.
Monitoring devices along the Patuxent also found declines of up to 50 percent in concentrations of phosphorus from Solomons to the middle of the bay, according to an abstract of the report.
The other key nutrient -- nitrogen -- has not declined as much since 1984, according Robert Summers, another state environmental official. But that represents an improvement from the previous five years, when nitrogen levels were on a steady upward path.
Further declines could result from the installation of new nitrogen-removing equipment this year at the huge Western Branch wastewater treatment plant near Laurel.
Mr. Summers also has tracked an 8 percent decline in nitrogen runoff into the upper third of the Patuxent.
Both Mr. Summers and Mr. Magnien cautioned that the encouraging findings did not mean the battle to lower nutrient pollution of the Patuxent, and hence the bay, was over.
Besides conservation and good runoff control practices, factors such as the amount of rainfall and levels of nitrogen in the air could have affected the new findings and could be reversed, Mr. Summers said.
Environmentalist John Kabler of the group Clean Water Action said he was encouraged by the new findings but also sounded a note of caution.
"I'm surprised. It's a good sign, because whatever happens to the Patuxent happens to the bay," he said. "But it surely does not mean that we can let down our guard."
There has yet to be a significant improvement in the clarity of the water or the amount of aquatic vegetation, which needs clear, well-lighted water to grow, said Mr. Magnien.
Researchers also say it will be up to five years before there is a noticeable improvement in the amount of oxygen in the Patuxent.