Heavy Metals and Lead Isotope Ratios in Annual Rings of the Red Pine Trees Collected in the Chugoku District and Comparisons with Coastal Sediments

Abstract

Concentrations of heavy metals and lead isotope ratios in annual rings of the Red Pine trees were measured. The Red Pine trees were collected in four sites located in the western parts of the Honshu Island of Japan; two sites were beside the industrial areas and the other two sites were in the non-industrial areas. Concentrations of lead, cadmium and zinc in annual rings collected in the industrial areas were higher than those collected in the non-industrial areas. Concentrations of lead in annual rings increased since 1940s-1950s and lead isotope ratios also changed at the same period, suggesting that sources of lead in annual rings were changed at the period of 1940s-1950s. Lead concentration reached the highest level in 1960s-1970s, and then began to decrease steeply, regardless of sampling sites. Lead isotope ratios were not affected by the decrease of lead concentration. Although the sources of anthropogenic lead were complicated, the gasoline additives and industrial air dusts would be one of the major sources for the lead pollution since 1940s-1950s. Concentrations of cadmium and zinc in annual rings were also decreased since 1960s-1970s in the same manner as lead. Vertical profiles of lead concentrations and lead isotope ratios in coastal sediments collected in the Hiroshima Bay were compared with the chronological change in annual rings. There were some differences between chronological distribution of lead and lead isotope ratio in annual rings and those in sediments; In other metals, such as manganese, calcium, aluminum and copper, characteristic changes of the chronological distribution found for the heavy metals in annual rings could not clearly seen and concentrations were independent of the sampling sites.