Chemical Forms of Mercury and Cadmium Accumulated in Marine Mammals and Seabirds as Determined by XAFS Analysis

Abstract

Marine mammals and seabirds tend to exhibit high accumulations of mercury, cadmium, and selenium in their livers and kidneys. In this study, chemical forms of mercury, cadmium, and selenium accumulated in the livers and kidneys of northern fur seal (Callorhinus ursinus), Risso's dolphin (Grampus griseus), and black-footed albatross (Diomedea nigripes) were studied by extended X-ray absorption fine structure (EXAFS) spectroscopy to reveal the detoxification mechanisms of these metals. It was found that mercury and selenium exist in the form of HgSe in the liver of northern fur seal. Mercury levels were found to be higher than those of Se, based on their molar ratio, in black-footed albatross. XAFS analysis disclosed an existence of chalcogenide containing both Hg-Se and the Hg-S bonds, suggesting the existence of a solid solution Hg(Se, S) as granules in black-footed albatross. In contrast, Cd concentrations in the kidney were higher than those in the liver for northern fur seal, black-footed albatross, and Risso's dolphin. It was found that Cd was bound to sulfur, which was probably derived from the metallothionein. The Cd-O bond was observed in the tissues of northern fur seal.

What are the toxicological effects of mercury in Arctic biota?

“…This complex probably represents a direct covalent (or other strong) interaction of Hg and Se. In some wild aquatic predatory bird and mammal species, it has been shown that MeHg predominates in the liver at low total Hg (THg) concentrations whereas at higher concentrations an increasingly large percentage of THg is present as inorganic Hg associated with Se, and some studies have identified this complex as HgSe (tiemanite) (Koeman and van deVen, 1975;Dietz et al, 1990Dietz et al, , 1998aDietz et al, , 1998bDietz et al, , 2000aDietz et al, 2000bScheuhammer et al, 1998Scheuhammer et al, , 2008Wang et al, 2001;Woshner et al, 2001aWoshner et al, , 2001bWoshner et al, , 2008O'Hara et al, 2003;Arai et al, 2004;Ikemoto et al, 2005;Dehn et al, 2005Dehn et al, , 2006Eagles-Smith et al, 2009;Moses et al, 2009;Routti et al, 2011).…”

The Chemical Nature of Mercury in Human Brain Following Poisoning or Environmental Exposure

“…Previous work has identified HgSe in whale liver (20), and species with HgSe coordination also have been found in the livers and kidneys of dolphin, seal, and albatross (21). HgSe is a particularly stable and insoluble form of mercury [molar solubility product K sp ≈ 10 -59 ].…”

Arsenic in Marine Mammals, Seabirds, and Sea Turtles

“…It is well known that mercury is detoxified through binding to selenium and/or sulfur in marine mammals and seabirds Ng et al 2001;Arai et al 2004;Ikemoto et al 2004). Similarly, interaction between arsenic and selenium and/or sulfur may also occur (Gailer 2007).…”