Identification of mercury-containing nanoparticles in the liver and muscle of cetaceans

Natural mercury-containing nanoparticles (Hg-NPs) have been found in the environment, but the information for Hg-NPs in organisms was still limited. Clarifying the unique roles of Hg-NPs in organisms is crucial to fully understand the health risks of Hg. Herein, liver and muscle tissues of cetaceans were collected to identify the presence and characteristics of Hg-NPs. We found that methylmercury (MeHg) was the dominant species of Hg in muscles, while inorganic Hg (IHg) accounted for 84.4-99.0% (average 94.0%) of Hg in livers. By using transmission electron microscopy (TEM), size exclusion chromatography coupled with inductively coupled plasma mass spectrometry (SEC-ICPMS) and single particle ICPMS (sp-ICPMS), large amounts (9-161 mu g/g) of Hg-NPs in livers and small amounts (0.1-0.4 mu g/g) in muscles were observed, indicating that Hg-NPs was an important form of Hg in livers. Both small sized (5-40 nm) and large sized (>100 nm) Hg-NPs were identified, which were mainly complexed with selenium (Se) and sulfur (S) as well as a few cadmium (Cd), lead (Pb) and silver (Ag). This study provided direct evidence of Hg-NPs in marine mammals as well as their chemical form and size distribution, which are helpful for further understanding the biogeochemical cycle and health risk of Hg.

Automated summary

This study identified the presence of significant amounts of Hg-NPs in the livers of cetaceans, mainly in the form of inorganic mercury, while methylmercury was predominant in muscle tissues. The Hg-NPs were found to vary in size, being complexed with selenium, sulfur, and in some cases cadmium, lead, and silver. This research provides valuable insights into the biogeochemical cycle and health risks associated with mercury in marine mammals.