Hexachlorocyclohexane isomers as markers in the water flow of the Atlantic Ocean

Abstract

Surface water, deep sea water and fish samples from various regions of the Atlantic Ocean were analyzed for a hexachlorocyclohexane (HCH) contamination. Fish samples integrate over area and time, but can only provide semi-quantitative information about the HCH burden of their individual environment, while water samples give spot values of a defined situation in time and space. As fish are easily available samples and may be stored without problems, they will remain valuable indicators for the pollution of the sea with persistent xenobiotics. In the surface water samples (1–250 m), no significant differences for the sums of alpha-and gamma-HCH contents could be found between the northern and the southern hemisphere (68–133 pg/l). The same trend was observed with the fish samples (3–15 ng/g extr. lipids), although they represented different areas and times. A characteristic variation in the ratio of the alpha/gamma HCH concentration (ratio alpha/gamma HCH) with geographic latitude could be established for both water and fish samples, reflecting the different input patterns of hexachlorocyclohexanes in both hemispheres (northern hemisphere alpha gamma > 1 , southern hemisphere alpha gamma < 1 ). In the water column near the Bermudas the alpha/gamma ratio switches from > 1 (15–25 m) to < 1 (350–900 m) and back to > 1 (1200 m) reflecting the input of water at 300–900 m deriving from the subantarctic convergence.