Delphine Foucher

Mercury isotope fractionation during volatilization of Hg(0) from solution into the gas phase

The objective of this work was to determine the magnitude of mercury isotope fractionation during volatilization of Hg(0) dissolved in aqueous solution to the gas phase and to develop a method for the precise determination of isotope ratios of gaseous Hg(0) by multi-collector ICP-MS. Hg(0) was generated in situ by reducing Hg(II) using SnCl2 and subsequently purged into a trapping solution. A 316 μM KMnO4 trapping solution, acidified by 0.9 M sulfuric acid, recovered 96.1 ± 4.0% of Hg (2 SD, n = 20). The observed δ202Hg of −0.049 ± 0.065‰ (2 SD, n = 17) relative to the initial Hg standard was not greater than the daily external precision of the isotope ratio measurement, which is typically <0.100‰ (2 SD). The volatilization experiments were conducted by reducing Hg(II) completely using SnCl2, letting the developed Hg(0) evaporate from solution and purging the Hg(0) vapor in the headspace over the solution into the trapping solutions. The concentration and isotope ratios of Hg in both the trapping solutions and the Hg(0) remaining in solution were measured at different time intervals. The kinetics of the volatilization was found to be a first order process. The pattern of isotope fractionation during volatilization followed a Rayleigh fractionation with an observed maximum δ202Hg value of 1.48 ± 0.07‰ (2 SD). Fractionation factors of 1.00044 and 1.00047 were obtained in two independent experiments. These results provide the first experimental proof for, and quantified the pattern and magnitude of, the Hg isotope fractionation during volatilization of Hg(0) from solution into the gas phase.

Tracing Mercury Contamination Sources in Sediments Using Mercury Isotope Compositions

Mercury (Hg) isotope ratios were determined in two sediment cores collected from two adjacent reservoirs in Guizhou, China, including Hongfeng Reservoir and Baihua Reservoir. Hg isotope compositions were also analyzed in a soil sample collected from the catchment of Hongfeng Reservoir and three cinnabar samples collected from the Wanshan Hg mine. Baihua Reservoir was contaminated with runoff from Guizhou Organic Chemical Plant (GOCP) when metallic Hg was used as a catalyst to produce acetic acid. Hongfeng Reservoir, located upstream of Baihua, receives Hg from runoff and atmospheric deposition. We demonstrated that delta(202)Hg values relative to NIST 3133 of sediment in Baihua Reservoir ranging from -0.60 to -1.10 per thousand were distinctively different from those in Hongfeng Reservoir varying from -1.67 to -2.02 per thousand. While sediments from both Baihua and Hongfeng Reservoirs were characterized by mass dependent variation (MDF), only Hongfeng Reservoir sediments were characterized by mass independent variation (MIF). Moreover, by using a binary mixing model, we demonstrated the major source of Hg in sediment of Hongfeng Reservoir was from runoff due to soil erosion, which was consistent with the conclusion obtained from a previous Hg balance study. This study demonstrates Hg isotope data are valuable tracers for determining Hg contamination sources in sediments.

Deposition of Mercury Species in the Ny-Ålesund Area (79°N) and Their Transfer during Snowmelt

Arctic snowpacks are often considered as temporary reservoirs for atmospheric mercury (Hg) deposited during springtime deposition events (AMDEs). The fate of deposited species is of utmost importance because melt leads to the transfer of contaminants to snowmelt-fed ecosystems. Here, we examined the deposition, fate, and transfer of mercury species (total Hg (THg) and methylmercury (MeHg)) in an arctic environment from the beginning of mass deposition of Hg during AMDEs to the full melt of the snow. Following these events, important amounts of THg were deposited onto the snow surface with concentrations reaching 373 ng.L(-1) and estimated deposition fluxes of 200-2160 ng.m(-2). Most of the deposited Hg was re-emitted to the atmosphere via photochemical reactions. However, a fraction remained stored in the snow and we estimated that the spring melt contributed to an input of 1.5-3.6 kg.year(-1) of THg to the fjord (i.e., 8-21% of the fjords THg content). A monitoring of MeHg in snow using a new technique (DGT sensors) is also presented.

High Precision Determination of Mercury Isotope Ratios Using Online Mercury Vapor Generation System Coupled with Multicollector Inductively Coupled Plasma-Mass Spectrometer

Abstract In this study, a method for high-precision measurement of Hg isotope ratios by multiple collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) with on-line Hg reduction technique was developed. The procedure was evaluated to obtain high-precision measurements that were good enough to significantly detect the anticipated small differences in Hg isotope compositions in natural samples. Typically, internal precision was better than 0.02% ° (1 RSE) on all Hg ratios investigated. The external reproducibility for standard NIST SRM3133 and UM-Almaden secondary solution, nature samples were 0.06% ° (2SD) and 0.10% ° (2SD) over a period of 7 months, respectively. The extent of fractionation has been investigated in a series of natural samples from different locations in China. The ratio 202 Hg/ 198 Hg expressed as δ values (per mil deviations relative to NIST SRM 3133 Hg standard solution) displayed differences from –3.48% ° to 0.633% ° . These results indicated a wide perspective application of tracing Hg in the environment.

Methylmercury speciation in the dissolved phase of a stratified lake using the diffusive gradient in thin film technique.

The diffusive gradient in thin film (DGT) technique was successfully used to monitor methylmercury (MeHg) speciation in the dissolved phase of a stratified boreal lake, Lake 658 of the Experimental Lakes Area (ELA) in Ontario, Canada. Water samples were conventionally analysed for MeHg, sulfides, and dissolved organic matter (DOM). MeHg accumulated by DGT devices was compared to MeHg concentration measured conventionally in water samples to establish MeHg speciation. In the epilimnion, MeHg was almost entirely bound to DOM. In the top of the hypolimnion an additional labile fraction was identified, and at the bottom of the lake a significant fraction of MeHg was potentially associated to colloidal material. As part of the METAALICUS project, isotope enriched inorganic mercury was applied to Lake 658 and its watershed for several years to establish the relationship between atmospheric Hg deposition and Hg in fish. Little or no difference in MeHg speciation in the dissolved phase was detected between ambient and spike MeHg.

Quantification of 226Ra at environmental relevant levels in natural waters by ICP-MS: Optimization, validation and limitations of an extraction and preconcentration approach

Radium (Ra) at environmental relevant levels in natural waters was determined by ICP-MS after an off-line pre-concentration procedure. The latter consisted of Ra selective elution from potential interfering elements (i.e. other alkaline earth cations: Ba2+, Sr2+, Ca2+, Mg2+) on a series of two different ion exchange resins (AG50W-X8 and Sr-resin). The overall analytical method was optimized according to the instrumental performance, the volume of water sample loaded on resins, and the sample salinity. Longer acquisition time (up to 150 s) was required to ensure stable measurement of Ra by ICP-MS at ultra trace level (1.0pgL-1). For a synthetic groundwater spiked with Ra at 10.0pgL-1, the analytical procedure demonstrated efficient separation of the analyte from its potential interfering elements and a complete recovery, independent of the sample volume tested from 10 up to 100mL. For synthetic seawater spiked at a level of 10.0pgL-1 of Ra, the total load of salts on the two resins should not exceed 0.35g in order to ensure a complete separation and recovery of Ra. The method was validated on natural waters (i.e. groundwater, freshwater and seawater samples) spiked with Ra at different levels (0.0, 0.5, 1.0 and 5.0pgL-1). Absolute Ra detection limits were determined at 0.020pgL-1 (0.73mBqL-1) and 0.12pgL-1 (4.4mBqL-1) respectively for 60.0mL of freshwater sample and for 10.0mL of seawater.

Low level exposure to manganese from drinking water and cognition in school-age children

HighlightsMeasured Mn in drinking water, childrens saliva, hair, and toe nails.Assessed neurodevelopment in children.Mn concentrations in drinking water are very low.Higher toe nail Mn associated with poorer Performance IQ scores only in girls.Higher Mn in water associated with better Performance IQ scores only in boys. Background: Manganese (Mn) is an element found in the environment and certain geographic areas have elevated concentrations in soil and water du to natural conditions or anthropic activities. A growing body of data suggests that exposure to manganese in drinking water could be neurotoxic. Objective: Firstly, we aimed to examine the association between exposure to manganese from drinking water and cognition in children consuming well water. Secondly, we also aimed to examine the relation between cognition and manganese concentrations in childrens hair, nail, and saliva. Methods: A total 259 children from 189 households consuming well water were included in the present study (ages 5.9 to 13.7 years). We assessed childrens cognition with the WISC‐IV, and we used five indicators of manganese exposure: concentration in tap water, intake from the consumption of water divided by childs weight, manganese concentration in childrens hair, toe nail, and saliva. We used General Estimating Equation analysis to assess the relation between manganese exposure indicators and IQ scores, adjusting for potential confounders, and taking into account family clusters. Results: Drinking water manganese concentrations were generally low, with 48% of children consuming water <5 &mgr;g/L, 25% >50 &mgr;g/L, and 4% >400 &mgr;g/L. Results differed by sex. In girls, higher manganese concentration in water, hair, and toe nail were associated with poorer Performance IQ scores but this was significant only for toe nail (for a 10‐fold increase in manganese, &bgr;: −5.65, 95% CIs: −10.97, −0.32). Opposite associations were observed in boys, i.e., better Performance IQ scores with higher manganese concentration hair, toe nail, and water, the latter being significant (&bgr;: 2.66, 95% CIs: 0.44, 4.89). Verbal IQ scores did not seem to be associated with manganese exposure indicators. Conclusions: Drinking water manganese levels were considerably lower than in previous studies reporting neurotoxic effects. There was no clear indication of an association between exposure to manganese and cognitive development in this sample of school‐age children although the data suggest there might be sex‐specific associations. Given the low levels of exposure and sex‐specific associations, a larger sample size would have been required to increase the statistical power and better characterize the relations.

Assessment of saliva, hair and toenails as biomarkers of low level exposure to manganese from drinking water in children

HighlightsMeasured Mn in drinking water, childrens saliva, hair and toenails.Mn concentrations in drinking water are very low.Mn in hair and toenail reflect reasonably well Mn exposure from drinking water.Mn in saliva correlates less strongly to Mn in drinking water. ABSTRACT We evaluated hair, toenails, and saliva (whole and supernatant) as biomarkers of exposure to manganese (Mn) in 274 school age children (6–13 years) consuming well water in southeastern New Brunswick, Canada. Mn concentrations in tap water ranged from <0.03 to 1046 &mgr;g L−1 (geometric mean 5.96 &mgr;g L−1). The geometric mean of Mn intake resulting from the consumption of water was 0.25 (0–34.95) &mgr;g kg−1 day−1. Both Mn concentration in water and Mn intake were significantly correlated with Mn in hair (r = 0.60 and r = 0.53, respectively), Mn in toenail (r = 0.29 and r = 0.37 respectively) and to a lesser extent with Mn in saliva supernatant (r = 0.14 and r = 0.18, respectively). Mn in whole saliva did not correlate with Mn in water or Mn intake. Both Mn in hair and Mn in toenail allowed to discriminate the most exposed group from the least exposed group, based on Mn in water and Mn intake from water. In this group of children with low level Mn exposure, Mn concentrations in hair, and toenails reflected reasonably well Mn exposure from drinking water, whereas Mn content in saliva correlated less strongly.

Exposure to low environmental concentrations of manganese, lead, and cadmium alters the serotonin system of blue mussels

Serotonin plays a crucial role in mussel survival and reproduction. Although the serotonin system can be affected by metals, the effects of environmental concentrations of metals such as manganese (Mn), lead (Pd), and cadmium (Cd) have never been studied in blue mussels. The present study aimed to determine the effects of exposure to Mn, Pb, or Cd on serotonin levels, monoamine oxidase (MAO) activity, and serotonin transporter (SERT) levels in the blue mussel Mytilus edulis. Mussels were exposed in vivo to increasing and environmentally relevant doses of Mn (10-1000 nM; 0.5-50 μg/L), Pb (0.01-10 nM; 0.002-2 μg/L), or Cd (0.01-10 nM; 0.001-1 μg/L) for 28 d. Serotonin levels, MAO activity, and SERT expression were analyzed in the mussel mantle. Expression of SERT protein was significantly decreased, by up to 81%, following Mn, Pb, or Cd exposure. The activity of MAO in females was almost 2-fold higher, versus males, in nonexposed control mussels. In mussels exposed to 0.1 nM of Pb (0.02 μg/L), MAO activity was increased in males and decreased in females. In Cd-exposed mussels, a sex-dependent, inverted nonmonotonic pattern of MAO activity was observed. These results clearly indicate that low environmental concentrations of Mn, Pb, and Cd affect the serotonin system in blue mussels. Environ Toxicol Chem 2018;37:192-200.

Radium geochemical monitoring in well waters at regional and local scales: an environmental impact indicator-based approach

To assess radium (226Ra) as a potential indicator of impact in well waters, we investigated its behavior under natural conditions using a case study approach. 226Ra geochemistry was investigated in 67 private wells of southeastern New Brunswick, Canada, a region targeted for potential shale gas exploitation. Objectives were to i) establish 226Ra baseline in groundwater; ii) characterize 226Ra spatial distribution and temporal variability; iii) characterize 226Ra partitioning between dissolved phase and particulate forms in well waters; and iv) understand the mechanisms controlling 226Ra mobility under natural environmental settings. 226Ra levels were generally low (median = 0.061 pg L-1, or 2.2 mBq L-1), stable over time, and randomly distributed. A principal component analysis revealed that concentrations of 226Ra were controlled by key water geochemistry factors: the highest levels were observed in waters with high hardness, and/or high concentrations of individual alkaline earth elements (i.e. Mg, Ca, Sr, Ba), high concentrations of Mn and Fe, and low pH. As for partitioning, 226Ra was essentially observed in the dissolved phase (106 ± 19%) suggesting that the geochemical conditions of groundwater in the studied regions are prone to limit 226Ra sorption, enhancing its mobility. Overall, this study provided comprehensive knowledge on 226Ra background distribution at local and regional scales. Moreover, it provided a framework to establish 226Ra baselines and determine which geochemical conditions to monitor in well waters in order to use this radionuclide as an indicator of environmental impact caused by anthropogenic activities (e.g. unconventional shale gas exploitation, uranium mining, or nuclear generating power plants).