HISTORICAL INPUTS OF POLYCHLORINATED-BIPHENYLS AND OTHER ORGANOCHLORINES TO A DATED LACUSTRINE SEDIMENT CORE IN RURAL ENGLAND

Lacustrine sediment cores were obtained from Esthwaite Water, a seasonally anoxic rural English lake. Samples were sectioned, radioisotopically dated, and analyzed for 22 individual polychlorinated biphenyl (PCB) congeners and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its metabolites. The most abundant congeners in the sediments were 28, 44, 66, 110, 138, 149, 153, and 180. PCB fluxes to the sediment increased slowly from the late 1920s/early 1930s until the late 1940s, escalating sharply thereafter. Maximum PCB fluxes (3.26 ng cm-2 year-1) occurred to sediments dated from the late 1950s/early 1960s. During the following decade inputs of PCBs decreased rapidly, concurrent with restrictions on production and use. Present input levels are ca. 2.17 ng cm-2 year-1, with lower chlorinated congeners making the major contribution. Inputs of DDT and its analogues peaked in the mid-1950s (19.2 ng SIGMA-DDT cm-2 year-1), with DDD the major metabolite. The possible influence of postdepositional factors and coring artifacts on the concentration depth profiles and the apparent presence of PCBs in pre-1930 sediments are discussed.