Evaluation of butyltin compounds in Maryland waters of Chesapeake Bay

A monthly sampling programme for dibutyltin (DBT), tributyltin (TBT) and tetrabutyltin (TTBT) was initiated for a period of one year (July 1985–June 1986) in the Maryland waters of Chesapeake Bay. Concentrations of the above butyltin species were evaluated in the microlayer and water column of eight sampling stations representing two small and two large marinas, a large harbour, two major river systems and a heavily used shipping channel. DBT concentrations in the microlayer were generally higher in the four marinas when compared with the other stations. The highest DBT concentration reported in the microlayer was 1156 ng l −1. Mean microlayer TBT concentrations ranged from 54–310 ng l −1 in the four marinas. Three TBT concentrations ranging from 1049–1171 ng l −1 were reported in the microlayer of the marinas. TBT concentrations of 41 and 29 mg l −1 were detected in the microlayer of a heavily used shipping channel (C & D Canal) during May and June. TTBT concentrations were not detected in the microlayer at most stations during the 12 month sampling period. Mean DBT concentrations in the water column ranged from 23–145 ng l −1 in the four marinas. DBT concentrations in the water column of the other stations were < 35 ng l −1. Mean water column concentrations of TBT ranged from 51–408 ng l −1 in all four marinas. Peak concentrations of TBT were reported in May and June for the various marinas. The highest TBT concentration reported in the water column was 998 ng l −1. TBT concentrations of 20–24 ng l −1 were reported in one of the river systems (Potomac River). TTBT concentrations were not detected in the water column at most of the stations.