A REVIEW OF CONCURRENT AMBIENT WATER COLUMN AND SEDIMENT TOXICITY TESTING IN THE CHESAPEAKE BAY WATERSHED - 1990-1994

The objectives of this study were to identify toxic ambient areas in t he Chesapeake Bay watershed by using a battery of water column and sed iment toxicity tests. Twenty-five ambient stations in nine river/harbo rs were tested during 1990 through 1994. Seasonal and annual compariso ns were conducted at selected stations. Inorganic and organic contamin ants were evaluated in ambient water and sediment concurrently with wa ter column and sediment tests to assess possible causes of toxicity, a lthough absolute causality cannot be established. Multivariate statist ical analysis was used to develop a TOX-INDEX at each station for both water column and sediment toxicity data. Water column tests from the 5-year testing period showed that 43% of the time, some degree of toxi city was reported. The most toxic sites based on water column results were located in urbanized areas such as the Elizabeth River, Baltimore Harbor, and the Middle River. Water quality criteria for copper, lead , mercury, nickel, and zinc were exceeded at one or more of these site s. Some degree of sediment toxicity was reported from 70% of the tests conducted during the 5-year period. The Elizabeth River and Baltimore Harbor stations were reported as the most toxic areas based on sedime nt results. Sediment toxicity guidelines (Long and Morgan effects rang e median [ER-M] values) were exceeded for one or more of the following metals at these two locations: arsenic, cadmium, chromium, copper, le ad, nickel, and zinc. At the Elizabeth River stations 9 of 16 semivola tile organics and 2 of 7 pesticides measured exceeded the ER-M values. Various semivolatile organics exceeded the ER-M values at a number of Baltimore Harbor sites; pyrene and dibenzo (a,h) anthracene were part icularly high at one of the stations (Northwest Harbor).