Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 55, Issue 18, Pages 12393-12402Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c03572
Keywords
mercury nanoparticles; mercury methylation; mercury association; spICP-TOF-MS; mercury bioavailability proxy; sediment contamination; mercury methylation indicator
Categories
Funding
- U.S. Army Engineer Research Office [W911NF1910063]
- NSF
- EPA under NSF, Center for the Environmental Implications of NanoTechnology (CEINT) [EF-1266252]
- Chevron
- U.S. Department of Defense (DOD) [W911NF1910063] Funding Source: U.S. Department of Defense (DOD)
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The study found that marine sediments contained 20-50% of total Hg in the <0.5 µm size fraction, while terrestrial and river sediments only contained 0.5-3.0% in this fraction. X-ray absorption spectroscopy revealed that metacinnabar (beta-HgS) was the main mercury species in marine sediment, while organic Hg-thiol (Hg(SR)(2)) was predominant in terrestrial sediment. Single-particle inductively coupled plasma time-of-flight mass spectrometry analysis indicated that half of the Hg in the <0.5 µm size fraction of marine sediment existed as individual nanoparticles.
Particle-specific properties, including size and chemical speciation, affect the reactivity of mercury (Hg) in natural systems (e.g., dissolution or methylation). Here, terrestrial, river, and marine sediments were size-fractionated and characterized to correlate particle-specific properties of Hg-bearing solids with their bioavailability potential and measured biomethylation. Marine sediments contained similar to 20-50% of the total Hg in the <0.5 mu m size fraction, compared to only 0.5 and 3.0% in this size fraction for terrestrial and river sediments, respectively. X-ray absorption spectroscopy (XAS) analysis indicated that metacinnabar (beta-HgS) was the main mercury species in a marine sediment, whereas organic Hg-thiol (Hg(SR)(2)) was the main mercury species in a terrestrial sediment. Single-particle inductively coupled plasma time-of-flight mass spectrometry analysis of the marine sediment suggests that half of the Hg in the <0.5 mu m size fraction existed as individual nanoparticles, which were beta-HgS based on XAS analyses. Glutathione-extractable mercury was higher for samples containing Hg(SR)(2) species than beta-HgS species and correlated well with the amount of Hg biomethylation. This particle-scale understanding of how Hg speciation and particle size affect mercury bioavailability potential helps explain the heterogeneity in Hg methylation in natural sediments.
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