Harford and Cecil counties will mark the 400th anniversary of Captain John Smith's second expedition to the northern Chesapeake area with some 21st-century technology.

 A smart buoy, equipped with sensors that constantly provide meteorological and water-quality data, including salinity and turbidity, and measure currents, will soon be anchored in the Susquehanna River near where it meets the bay. The buoy, the fifth in the National Oceanic and Atmospheric Administration's Chesapeake Bay Interpretive Buoy System, will be visible from Havre de Grace and Perryville.

 The buoy will arrive by truck Friday, along with its 2,500-pound steel anchor. A chartered barge, equipped with a crane, will drop the anchor that day. The crane will drop the buoy during a ceremony at 10:30 a.m. Saturday.

 The Susquehanna buoy has an additional sensor that determines nitrate levels, making it, at $100,000, the most expensive in the NOAA system.

 "This buoy will let us evaluate the water as it flows by," said Doug Wilson, NOAA oceanographer and program manager for the buoy system. "The Susquehanna, the major source of bay nutrients, is a great place for us to monitor with this nitrate sensor."

 After a few years of collecting such data, NOAA might be able to better ascertain the river's impact on the bay. That information could prompt critical improvements in land use upstream, Wilson said.