Chemical composition of East Pacific Rise basal sediments

Analyses by atomic absorption spectrophotometry and spark-source mass spectrography of 25 basal metalliferous sediment units from widely spaced locations on the western flank of the East Pacific Rise show that the deposits are enriched relative to normal pelagic sediment in Fe, Mn, Ni, Cu, Pb, Zn, and many trace elements. The elements are partitioned differently between the various mineralogic constituents of the sediment, with Fe and Mn largely in separate phases and many of the remaining elements primarily associated with reducible ferromanganese oxide minerals but also with iron minerals and other phases. Most of the iron in the deposits is probably of volcanic origin, and much of the manganese and minor elements is derived from sea water. The bulk composition of the deposits varies with age; this is thought to be due to variations in the incidence of volcanic activity at the East Pacific Rise crest where the deposits were formed.

Concentrations of As and other chemical elements in bottom sediments of the Baltic Sea

As is less toxic than Hg, Cd, Pb, Se, Zn, and Cu. The As clarke for clays and shales is 10 ppm. Our samples of bottom sediments from Kurshskii Bay were determined to contain from 15 to 26 ppm As and up to 34 ppm As in the vicinity of the Neman River mouth. Elevated As concentrations (50-114 ppm) were detected in four columns of subsurface bottom sediments (at depths of 10-65 cm) from the Vistula Lagoon. Elevated As concentrations (50-180 ppm) were also found in a few surface samples of sand from the Gdansk Deep near oil platform D-6. These sediments are either partly contaminated with anthropogenic As or contain Fe sulfides and glauconite, which can concentrate As and contain its elevated concentrations. The As concentration in columns of bottom sediments from the Gulf of Finland were at the natural background level (throughout the columns) typical of the area (9-34 ppm). We repeatedly detected very high As concentrations (up to 227 ppm As) in politic ooze from Bornholm Deep, in the vicinity of the sunken vessel with chemical weapons. The sources of elevated As concentrations in the Baltic Sea are the following: (1) chemical weapon (CW) material buried in the floor of the Baltic Sea; (2) As-bearing pesticides, agricultural mineral fertilizers, and burned coal and other fuels; (3) kerogen-bearing Ordovician rocks exposed on the bottom; and (4) As-rich Fe sulfides brought to the area together with construction sand and gravel. This mixture was used in paper production and for the construction of hydraulic engineering facilities in the Vistula Lagoon in the early 20th century and later caused the so-called lagoon disease.

Chemical composition of nodules from two locations in the Pacific Ocean using different methods

Manganese nodules recovered in the Pacific Ocean by the U. S. Bureau of Mines and by DeepSea Ventures Ltd. are studied for their chemical composition using X microprobe and X-ray fluorescence methods.