Changes in lead and mercury atmospheric deposition due to industrial emissions in Southeastern Brazil

Abstract

This study presents the first estimate of Pb and Hg loads to southeastern Brazil, the most industrialized region of South America, during the 20th century. This estimate was based on the analysis of dated ombrotrophic lake sediment cores, from the Itatiaia Mountains, at the Paraíba do Sul River valley region, in the Rio de Janeiro State. Average Pb concentrations along the cores ranged from 40 to 180 µg g-1, whereas for Hg, concentrations ranged from 30 to 420 ng g-1. Mercury concentrations correlated significantly with Pb concentrations up to the middle of the 1980's. Average regional pre-industrial (prior to 1940) Pb accumulation rate was 8.0 ± 2.0 mg m-2 yr-1, with maximum at the surface of the cores ranging from 40 to 80 mg m-2 yr-1. The average Hg deposition rate was 36 µg m-2 yr-1, between 1910 and 1940. A maximum of 120 µg m-2 yr-1 was observed in the 1960's, with a further decrease after the late 1970's. The temporal Hg distribution pattern is similar to those reported in different regions of the northern hemisphere. However, regional pre-industrial Pb and Hg accumulation were from 3 to 6 times higher than those reported for the northern hemisphere. Emissions from the earlier industrialization of the northern hemisphere may have influenced the magnitude of regional pre-industrial Pb and Hg deposition in South America, where the industrialization started about 100 years latter. In the case of Hg, gold and silver mining during the previous three centuries, may have also affected regional pre-industrial values