Research highlights: elucidation of biogeochemical factors influencing methylmercury production

2015 ◽  
Vol 17 (10) ◽  
pp. 1708-1711 ◽  
Author(s):  
Paul R. Erickson ◽  
Vivian S. Lin
Keyword(s):  
Nutrient Availability ◽  
Mercury Contamination ◽  
Factors Influencing ◽  
Biogeochemical Factors ◽  
Methylmercury Production ◽  
Demethylation Activity

This Highlight features recent articles that examine in detail the effects of nutrient availability on the methylation–demethylation activity of microorganisms living in sediment with mercury contamination.

Factors influencing the achievement of steady state in mercury contamination among lakes and catchments of south-central Ontario

2009 ◽  
Vol 66 (2) ◽  
pp. 187-200 ◽  
Author(s):  
R. Brad Mills ◽  
Andrew M. Paterson ◽  
Jules M. Blais ◽  
David R.S. Lean ◽  
John P. Smol ◽  
...  
Keyword(s):  
Organic Matter ◽  
Steady State ◽  
Annual Runoff ◽  
Model Fit ◽  
Mercury Contamination ◽  
Positive Linear Relationship ◽  
South Central ◽  
Factors Influencing ◽  
Headwater Lakes ◽  
Drainage Ratio

Mercury (Hg) concentrations in recent (0.5–1 cm) and preindustrial (>30 cm) sediments were examined across lakes in south-central and eastern Ontario, Canada (45.53°N, 82.41°W to 44.15°N, 76.25°W), to determine whether Hg exported from watersheds is at steady state with atmospheric deposition. An examination of headwater lakes revealed that Hg enrichment was not uniform among watersheds but that the enrichment factor (EF = [Hg]present day/[Hg]preindustrial, standardized for organic matter) decreased as a function of drainage ratio (Ad /Ao, watershedarea/lakearea). Furthermore, the model fit was improved after accounting for differences in sulfate concentrations and pH among lakes: EF = (Ad /Ao)–15.96 – 0.07(SO 42– ) – (3.55(pH>8.3)) (R2 = 0.458, p = 0.0001). Hg concentrations in preindustrial sediments of headwater lakes showed a positive linear relationship with drainage ratio (partial t = 4.83, p < 0.0001, n = 66) that was strengthened following an adjustment for mean annual runoff (MAR) ([Hg]preindustrial = 0.011 ± 0.002(Ad /Ao) + 0.0008 ± 0.0003(MAR) (R2 = 0.108, F[1,66] = 8.01, p = 0.006)). Our results suggest that Hg export from watersheds may be currently lagging behind atmospheric Hg deposition, in which case, Hg export would increase into the future, even as Hg deposition from the atmosphere stabilizes.

scholarly journals The spatial legacy of Australian mercury contamination in the sediment of the Molonglo River

Elem Sci Anth ◽  
2020 ◽  
Vol 8 ◽  
Author(s):  
Dylan Stinton ◽  
Larissa Schneider ◽  
Sara Beavis ◽  
Janelle Stevenson ◽  
William A. Maher ◽  
...  
Keyword(s):  
New South ◽  
Sediment Cores ◽  
New South Wales ◽  
Surficial Sediment ◽  
Mercury Contamination ◽  
Mine Site ◽  
Factors Influencing ◽  
South Wales ◽  
Chemical Factors ◽  
Physical And Chemical

Mercury (Hg) contamination is an environmental concern as a by-product of legacy mining in Australia. Here we investigate the spatial and temporal distribution of Hg in the Molonglo River system in New South Wales, Australia, and assess the physical and chemical factors influencing that distribution. Mercury concentrations in sediment cores were measured in conjunction with 210Pb and 137Cs dating to establish historical contamination. This was done at the source mine site of Captains Flat, New South Wales, and the system’s sink in Lake Burley Griffin, Australian Capital Territory. Additionally, surficial sediment Hg concentrations along the Molonglo River were analyzed to determine the spatial distribution of Hg. Analytical results showed the primary physical and chemical factors influencing Hg dispersion to be distance, total organic matter, and the presence of iron oxides and oxyhydroxides. The highest Hg concentrations were near the mine site at Captains Flat and decreased significantly with distance. Sediment core analyses in both Captains Flat and the lake showed reductions in Hg concentrations toward surficial sediment layers. It is suggested government-funded rehabilitation programs are playing a part in reducing the release of metal contamination.

Exposed facets dictate microbial methylation potential of mercury sulfide nanoparticles

2020 ◽  
Author(s):  
Li Tian ◽  
Wenyu Guan ◽  
Yunyun Ji ◽  
Xin He ◽  
Wei Chen ◽  
...  
Keyword(s):  
Contaminated Soils ◽  
Early Stage ◽  
Theoretical Calculations ◽  
Desulfovibrio Desulfuricans ◽  
Mercury Contamination ◽  
Nanocrystal Growth ◽  
Subsequent Effect ◽  
Microbial Methylation ◽  
Methylmercury Production ◽  
Exposed Facets

Abstract Methylmercury formation is the major concern of global mercury contamination. Accurate prediction of methylmercury production remains elusive due in part to the lack of mechanistic understanding of microbial methylation potential of particulate-phase mercury. Here we show that the methylation potential of nanoparticulate metacinnabar, which is formed during the early stage of mercury mineralization and is ubiquitous in contaminated soils and sediments, is determined by its exposed facets. Nanoparticulate metacinnabar with higher (111) content exhibits significantly greater affinity to the methylating bacterium Desulfovibrio desulfuricans ND132, leading to higher methylmercury production. This is likely attributable to the favored binding between the (111) facet and the protein transporter responsible for mercury cellular uptake prior to methylation. The (111) facet of metacinnabar tends to diminish during nanocrystal growth, but natural ligands alleviate this process by preferentially adsorbing to the (111) facet (verified with adsorption experiments using facet-engineered model materials coupled with theoretical calculations). This facet evolution of metacinnabar and its subsequent effect on mercury bioavailability explain the intriguing observation that methylation potential of nanoparticulate mercury is surface-area-independent. Our discovery provides new mechanistic insights for interfacial processes involved in nanoparticle−microorganism interactions that have important implications for understanding the environmental behavior of mercury and other nutrient or toxic elements associated with widely present crystalline nanoparticles.

Biogeochemical factors influencing net mercury methylation in contaminated freshwater sediments from the St. Lawrence River in Cornwall, Ontario, Canada

2011 ◽  
Vol 409 (5) ◽  
pp. 968-978 ◽  
Author(s):  
Mary-Luyza Avramescu ◽  
Emmanuel Yumvihoze ◽  
Holger Hintelmann ◽  
Jeff Ridal ◽  
Danielle Fortin ◽  
...  
Keyword(s):  
Mercury Methylation ◽  
Freshwater Sediments ◽  
Factors Influencing ◽  
Biogeochemical Factors ◽  
St Lawrence River

Factors influencing adhesive bonding at the bone/implant interface

1992 ◽  
Vol 50 (2) ◽  
pp. 1114-1115
Author(s):  
Julie A. Martini ◽  
Robert H. Doremus
Keyword(s):  
Electron Microscopy ◽  
Adhesive Bonding ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Bone Implant ◽  
Factors Influencing ◽  
Lr White ◽  
Transmission Electron ◽  
New Zealand White Rabbits ◽  
Scanning Electron

Tracy and Doremus have demonstrated chemical bonding between bone and hydroxylapatite with transmission electron microscopy. Now researchers ponder how to improve upon this bond in turn improving the life expectancy and biocompatibility of implantable orthopedic devices.This report focuses on a study of the- chemical influences on the interfacial integrity and strength. Pure hydroxylapatite (HAP), magnesium doped HAP, strontium doped HAP, bioglass and medical grade titanium cylinders were implanted into the tibial cortices of New Zealand white rabbits. After 12 weeks, the implants were retrieved for a scanning electron microscopy study coupled with energy dispersive spectroscopy.Following sacrifice and careful retrieval, the samples were dehydrated through a graduated series starting with 50% ethanol and continuing through 60, 70, 80, 90, 95, and 100% ethanol over a period of two days. The samples were embedded in LR White. Again a graduated series was used with solutions of 50, 75 and 100% LR White diluted in ethanol.

Factors Influencing Electrophysiologic Responsivity in Normal Adults

1965 ◽  
Vol 8 (4) ◽  
pp. 323-347
Author(s):  
Robert Goldstein ◽  
Benjamin RosenblÜt
Keyword(s):  
Conditioned Stimulus ◽  
White Light ◽  
Pure Tone ◽  
Alpha Rhythm ◽  
White Women ◽  
White Men ◽  
Inverse Relation ◽  
Factors Influencing ◽  
Electrodermal Responses ◽  
Normal Adults

Electrodermal and electroencephalic responsivity to sound and to light was studied in 96 normal-hearing adults in three separate sessions. The subjects were subdivided into equal groups of white men, white women, colored men, and colored women. A 1 000 cps pure tone was the conditioned stimulus in two sessions and white light was used in a third session. Heat was the unconditioned stimulus in all sessions. Previously, an inverse relation had been found in white men between the prominence of alpha rhythm in the EEG and the ease with which electrodermal responses could be elicited. This relation did not hold true for white women. The main purpose of the present study was to answer the following questions: (1) are the previous findings on white subjects applicable to colored subjects? (2) are subjects who are most (or least) responsive electrophysiologically on one day equally responsive (or unresponsive) on another day? and (3) are subjects who are most (or least) responsive to sound equally responsive (or unresponsive) to light? In general, each question was answered affirmatively. Other factors influencing responsivity were also studied.

Factors Influencing Pressure in the Portal Vein as Studied in the Intact Animal

1950 ◽  
Vol 16 (1) ◽  
pp. 194-210 ◽  
Author(s):  
Frederick W. Hoffbauer ◽  
Jesse L. Bollman ◽  
John L. Grindlay
Keyword(s):  
Portal Vein ◽  
Intact Animal ◽  
Factors Influencing
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