Evidence for the decline of silver and lead and the increase of copper from 1977 to 1990 in the coastal marine waters of California

Abstract

Data collected from 1977 to 1990 by the California State Mussel Watch programme was analysed for long-term trends in silver, copper and lead at 20 sites along the California coast. 75% of the sites showed a clear trend in at least one heavy metal. Changes were evident in contaminated harbours as well as remote sites. 55% of the sites showed significant decreases in silver, 25% increased in copper and 40% decreased in lead. Declines in silver and lead appear related to decreased mass emission rates by wastewater treatment facilities, more effective reclamation efforts, and decreases in the use of leaded gasoline. Increase in copper appear related to increased vessel traffic and use of new, copolymer anti-fouling paints. These results suggest that the coastal waters of California are becoming cleaner, at least with respect to silver and lead. However, trends in copper are disturbing. These and other sites should continue to be monitored to document the status of copper and other trace metals in the environment.