, Jr . MERCURY IN SEDIMENTS

In recent years, the Coastal Water Research Project has conducted surveys of the distribution of certain trace substances in sediments around the major municipal wastewater outfalls off southern California. Because of high levels of heavy metals found in sediments near Los Angeles County Sanitation Districts outfall system off Whites Point in 1970, detailed surveys of the Palos Verdes shelf were conducted in 1972 and 1973. This article presents the results of the 1975 survey for total mercury in surface sediments in this same area. From previous data, we estimated that there are approximately 4 metric tons of anthropogenic mercury in the upper 30 cm of the Palos Verdes sediments. Because of the threat this mercury could pose to the local marine life, our studies have been aimed at determining its ultimate fate. Organic mercury compounds, which exhibit higher chronic toxicities and a strong affinity for animal tissues, are generally considered to be the most deleterious of the various forms of mercury. Other researchers have shown that organic mercury can be produced from inorganic forms by microbial methylation in the sediments: In Minamata, Japan, organic mercury taken up by marine animals via the sediments and subsequently ingested by humans was responsible for the poisoning of local inhabitants. Therefore, in 1975, we measured the total organic mercury content of the sediments for the first time. Other parameters related to sediment geochemistry were determined as well.