The sound is cleaner: a century of contaminant trends observed from dated cores [Puget Sound]

Human activity in and around Puget Sound is reflected in the discharge of concentrated organic and inorganic contaminants into the sound's sediments. As industrial-age human activity increased, so did the contaminant levels in the sediment. Age-dated sediment cores collected in 1982 showed that the input of chemicals to the Sound, including lead (Pb), mercury (Hg), silver (Ag), copper (Cu), and hydrocarbons, began to increase above background in the late 1800s. The maximum concentration of these chemicals appears to have been discharged into sediments between 1945 and 1965. Synthetic organic compounds, such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichlorethane (DDT), and chlorinated butadienes, first appeared in sediments deposited in the 1930s and reached a maximum in the 1960s. The presence of the subsurface maximum concentrations in fine-grained, deep-water sediments suggests that pollution-control strategies have improved the sediment quality of central Puget Sound.