One century of sedimentation and Hg pollution at the mouth of the Sagua la Grande River (Cuba)

Abstract

The Sagua la Grande River is the largest of northern Cuba. The socioeconomic development in this region during the last 100 years has caused changes in its natural conditions, such as an increase in Hg levels. In 1981, a chlor-alkali plant with mercury-cell technology was built on the river bank and has released several contaminants to the environment. Sedimentation along the river and the nearby coastal zone was reconstructed using the radionuclides ²¹⁰Pb, ²²⁶Ra, ¹³⁷Cs, and ^239,240Pu in sediment cores. The changes in sediment accumulation were related to important changes in the river basin after 1950, such as the channeling of the river in 1955 and the construction of the Alacranes Dam in 1972. Maximum sediment accumulation rates were attributed to large floods in 1933, 1948, and 1985 (Hurricane Kate). The ²¹⁰Pb chronology allowed the reconstruction of Hg pollution during the last four decades. In the locations with greatest fluvial influence, Hg concentrations increased since the early 1980s exceeding the Effects Range-Median (0.71 mg kg^–1). The accumulated Hg inventories released from the plant were one order of magnitude larger than those due to other sources. These results show the impact of Hg releases from this industry on the estuary, especially in the coastal zone close to the river mouth.