Some Recent Measurements of Trace Metals in Atlantic Ocean Waters

Measurements of dissolved arsenic have been made on samples from vertical profiles at six stations in the Cape Basin. After initial reduction of arsenic (V) to arsenic (III), arsine was generated and trapped in a solution containing potassium iodide and iodine. The concentrates were analysed using a zinc reductor column in conjunction with electrothermal atomic absorption spectrophotometry. Concentrations showed only small variations with depth, the average concentration for 17 samples collected above 110 m being 19.9 (range 17–23) nmol 1−1 and that for 42 samples from deeper waters, up to 4770 m, being 21.1 (range 17–28) nmol 1−1. Overall, the concentrations of arsenic were not significantly correlated with those of phosphate.

A method using extraction of metal dithiocarbamate complexes has been used, in conjunction with electrothermal atomic absorption spectrophotometry, to determine dissolved manganese at four stations in the Nares Abyssal Plain region. Surface concentrations of manganese were about 3 nmol 1−1; there was a rapid decrease in concentration over the uppermost several hundred metres and in deeper water concentrations mostly varied about 0.5 nmol 1−1. Concentrations of cadmium measured at these stations showed increases with depth which were closely related to those of phosphate, the deep water values fitting well with predictions based on comparable relationships in the Pacific Ocean.