Hg Vapor Research Articles

Mercury Vapor Sorption and Amalgamation with a Thin Gold Film.

Understanding the amalgamation mechanisms between mercury and gold is of fundamental interest and importance to many mercury sensing applications. However, there is only limited and piecemeal discussion in the literature of the mechanisms by which Au-Hg amalgams are formed on thin Au films. Here, we present a comprehensive description of a series of morphological changes occurring in a thin polycrystalline Au film during Au-Hg amalgamation investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and atomic force microscopy (AFM). These microscopic investigations enable us to offer a coherent explanation for the features and the mechanisms of amalgamation of Hg with Au in the film. We also use an optical technique (fringes of equal chromatic order, FECO) to observe changes in optical thickness and reflectivity of the film. Amalgamation reactions in the film render it inhomogeneous, thus making optical techniques unsuitable as a method for quantitative monitoring of Hg vapor using Au films of this type.

Ultrasensitive determination of mercury in waters via photochemical vapor deposition onto quartz substrates coated with palladium nanoparticles followed by total reflection X-ray fluorescence analysis

We describe a method for ultrasensitive detection of mercury (Hg) by total reflection X-ray fluorescence following photogeneration of Hg vapor and trapping onto quartz substrates coated with nanostructured palladium. The nanostructured coating was characterized by transmission electron microscopy. Hg vapor was generated by online photo-UV reduction in the presence of acetic acid, which acts as a precursor for reducing species. Trapping of Hg occurred as a result of amalgamation. A trapping time of 30 min and an acetic acid concentration of 2 mol L−1 provided the best results. An enrichment factor of 127 and a limit of detection as low as 54 ng L−1 of Hg were achieved. The repeatability of the method (expressed as the relative standard deviation at a level of 1 μg L−1) was 3 %. The method was successfully applied to the determination of Hg in water samples spiked with 10 μg L−1 of Hg. Recoveries ranged from 96 to 101 %.

Mercury levels and estimated total daily intakes for children and adults from an electronic waste recycling area in Taizhou, China: Key role of rice and fish consumption

In order to assess the potential health risks of Hg pollution, total mercury (T–Hg) and methyl mercury (MeHg) concentrations were determined in air, dust, surface soil, crops, poultry, fish and human hair samples from an electronic waste (e-waste) recycling area in Taizhou, China. High concentrations of T–Hg and MeHg were found in these multiple matrices, and the mean concentration was 30.7ng/m3 of T–Hg for atmosphere samples, 3.1μg/g of T–Hg for soil, 37.6μg/g of T–Hg for dust, 20.3ng/g of MeHg for rice and 178.1ng/g of MeHg for fish, suggesting that the e-waste recycling facility was a significant source of Hg. The inorganic Hg (I–Hg) levels (0.84μg/g) in hair samples of e-waste workers were much higher than that in the reference samples. Pearson's correlation coefficients showed that strong positive correlations (p<0.01) between hair I–Hg and time staying in industrial area (r=0.81) and between MeHg and fish consumption frequency (r=0.91), imply that workers were mainly exposed to Hg vapor through long-time inhalation of contaminated air and dust, while other population mainly exposed to MeHg through high-frequency fish consumption. The estimated daily intakes of Hg showed that dietary intake was the major Hg exposure source, and Hg intakes from rice and fish were significantly higher than from any other foods. The estimated total daily intakes (TDIs) of MeHg for both children (696.8ng/(kg·day)) and adults (381.3ng/(kg·day)) greatly exceeded the dietary reference dose (RfD) of 230ng/(kg·day), implying greater health risk for humans from Hg exposures around e-waste recycling facilities.

Human inorganic mercury exposure, renal effects and possible pathways in Wanshan mercury mining area, China

Rice can accumulate methylmercury (MeHg) and rice consumption is the main route of MeHg exposure for the local population in Guizhou, China. However, inorganic Hg (IHg) load in human body is not comprehensively studied in highly Hg polluted areas such as Hg mining areas. This study is designed to evaluate human IHg exposure, related renal effects and possible pathways in Wanshan Hg mining area, Guizhou, Southwest China. Residents lived within 3km to the mine waste heaps showed high Urine Hg (UHg) concentrations and the geometrical means (Geomean) of UHg were 8.29, 5.13, and 10.3μg/g Creatinine (Cr) at site A, D, and E, respectively. It demonstrated a gradient of UHg concentrations with the distance from the pollution sources. A significantly positive correlation between paired results for UHg concentrations and serum creatinine (SCr) was observed in this study, but not for UHg and blood urea nitrogen (BUN). There are significant increases of SCr in two quartiles with high UHg concentrations. The results indicated that human IHg exposure may cause impairment of renal function. By calculation of Probable Daily Intake from different routes, we found that dietary intake is the main pathway of IHg exposure for the local population, rather than inhalation of Hg vapor.

Human exposure and risk assessment associated with mercury contamination in artisanal gold mining areas in the Brazilian Amazon.

Mercury (Hg) contamination is an issue of concern in the Amazon region due to potential health effects associated with Hg exposure in artisanal gold mining areas. The study presents a human health risk assessment associated with Hg vapor inhalation and MeHg-contaminated fish ingestion, as well as Hg determination in urine, blood, and hair, of human populations (about 325 miners and 321 non-miners) from two gold mining areas in the Brazilian Amazon (São Chico and Creporizinho, Pará State). In São Chico and Creporizinho, 73 fish specimens of 13 freshwater species, and 161 specimens of 11 species, were collected for total Hg determination, respectively. The hazard quotient (HQ) is a risk indicator which defines the ratio of the exposure level and the toxicological reference dose and was applied to determine the threat of MeHg exposure. The mean Hg concentrations in fish from São Chico and Creporizinho were 0.83 ± 0.43 and 0.36 ± 0.33 μg/g, respectively. More than 60 and 22 % of fish collected in São Chico and Creporizinho, respectively, were above the Hg limit (0.5 μg/g) recommended by WHO for human consumption. For all sampling sites, HQ resulted from 1.5 to 28.5, except for the reference area. In Creporizinho, the values of HQ are close to 2 for most sites, whereas in São Chico, there is a hot spot of MeHg contamination in fish (A2-São Chico Reservoir) with the highest risk level (HQ = 28) associated with its human consumption. Mean Hg concentrations in urine, blood, and hair samples indicated that the miners group (in São Chico: urine = 17.37 μg/L; blood = 27.74 μg/L; hair = 4.50 μg/g and in Creporizinho: urine = 13.75 μg/L; blood = 25.23 μg/L; hair: 4.58 μg/g) was more exposed to mercury compared to non-miners (in São Chico: urine = 5.73 μg/L; blood = 16.50 μg/L; hair = 3.16 μg/g and in Creporizinho: urine = 3.91 μg/L; blood = 21.04 μg/L, hair = 1.88 μg/g). These high Hg levels (found not only in miners but also in non-miners who live near the mining areas) are likely to be related to a potential hazard due to exposure to both Hg vapor by inhalation and to MeHg-contaminated fish ingestion.

Comparison between Vapor Generation Methods Coupled to Atomic Absorption Spectrometry for Determination of Hg in Glycerin Samples

In this work, three vapor generation methods (photochemical vapor generation, cold vapor generation with NaBH4 or with SnCl2) coupled with atomic absorption spectrometry were compared for the analysis of mercury (Hg) in pure glycerin and residual glycerin from biodiesel production. For these methods, a simple sample treatment step was employed through a dilution with formic acid or water and all parameters used were optimized. The limits of detection for the methods PVG-CV AAS, CV AAS with NaBH4, and CV AAS with SnCl2, were 0.12, 0.11, and 0.04 μg L–1, respectively. Because no adequate certified reference material was available, the accuracy was evaluated by assessing the recoveries of Hg2+ spikes in all samples (84%–108.3%). When methods were compared, the PVG-CV AAS presented adequate sensitivity and simplicity, and provided a direct approach to the generation of Hg vapor from glycerin samples while promoting green chemistry. In addition, PVG-CV AAS provided limits of detection that are comparable to conventional methods for the determination of Hg by vapor generation.

Cross sensitivity effects of volatile organic compounds on a SAW-based elemental mercury vapor sensor

The detection of anthropogenic elemental mercury (Hg0) is the first step for evaluating the efficiency of mercury removal technologies implemented in many industrial processes. In order to determine the feasibility of a Hg0 vapor sensor for real world applications, it is very important to study the cross sensitivity performance of the sensor toward Hg0 vapor in the presence of common gas species present in industrial effluents. In this paper, we report the cross-sensitivity effect of several common VOCs; Ethylmercaptan (EM), Dimethyl Disulfide (DMDS) and Methyl Ethyl Ketone (MEK) on a surface acoustic wave (SAW) based sensor, when measuring low concentrations (<400ppbv) of Hg0 vapor at operating temperatures of 35 and 75°C. The sensor response magnitudes toward the tested Hg0 vapor concentrations (calibration curve) were found to follow the Langmuir extension isotherm at both operating temperatures (R2>0.98) indicating that the developed sensor is well designed to detect low concentrations of Hg0 vapor. In fact, the limit of detection (LOD) of the developed sensor toward Hg0 vapor was found to be ∼2.6 and ∼1ppbv at 35 and 75°C, respectively, which are well below the current threshold exposure limit set by the World Health Organization (5.6ppbv). Moreover, the sensor showed excellent repeatability (95±1%) at both operating temperatures. When tested for its selectivity toward Hg0 vapor in the presence of other gaseous species, the sensor exhibited a loss in response magnitude of only up to 7%; thus indicating the sensor has excellent selectivity toward Hg0 vapor and can potentially be used for online monitoring of low concentrations of Hg0 vapor within industrial processes and stack effluents.

Nanosphere Monolayer on a Transducer for Enhanced Detection of Gaseous Heavy Metal

This study reports for the first time that polystyrene monodispersed nanosphere monolayer (PS-MNM) based Au (Au-MNM) and Ag (Ag-MNM) nanostructures deposited on quartz crystal microbalance (QCM) transducers can be used for nonoptical based chemical sensing with extremely high sensitivity and selectivity. This was demonstrated by exposing the Au-MNM and Ag-MNM based QCMs to low concentrations of Hg(0) vapor in the presence interferent gas species (i.e., H2O, NH3, volatile organics, etc.) at operating temperatures of 30 and 75 °C. At 30 °C, the Au-MNM and Ag-MNM based QCMs showed ∼16 and ∼20 times higher response magnitude toward Hg(0) vapor concentration of 3.26 mg/m(3) (364 parts per billion by volume (ppbv)) relative to their unmodified control counterparts, respectively. The results indicated that the extremely high sensitivity was not due to the increased surface area (only 4.62 times increase) but due to their long-range interspatial order and high number of surface defect formation which are selectively active toward Hg(0) vapor sorption. The Au-MNM and Ag-MNM also had more than an order of magnitude lower detection limits (<3 ppbv) toward Hg(0) vapor compared to their unmodified control counterparts (>30 ppbv). When the operating temperature was increased from 30 to 75 °C, it was found that the sensors exhibited lower drift, better accuracy, and better selectivity toward Hg(0) vapor but at the compromise of higher detection limits. The high repeatability (84%), accuracy (97%), and stability of Au-MNM in particular make it practical to potentially be used as nonspectroscopic based Hg(0) vapor sensor in many industries either as mercury emission monitoring or as part of a mercury control feedback system.

Selective detection of elemental mercury vapor using a surface acoustic wave (SAW) sensor.

The detection of elemental mercury (Hg(0)) within industrial processes is extremely important as it is the first major step in ensuring the efficient operation of implemented mercury removal technologies. In this study, a 131 MHz surface acoustic wave (SAW) delay line sensor with gold electrodes was tested towards Hg(0) vapor (24 to 365 ppbv) with/without the presence of ammonia (NH3) and humidity (H2O), as well as volatile organic compounds (VOCs) such as acetaldehyde (MeCHO), ethylmercaptan (EM), dimethyl disulfide (DMDS) and methyl ethyl ketone (MEK), which are all common interfering gas species that co-exist in many industrial applications requiring mercury monitoring. The developed sensor exhibited a detection limit of 0.7 ppbv and 4.85 ppbv at 35 and 55 °C, respectively. Furthermore, a repeatability of 97% and selectivity of 92% in the presence of contaminant gases was exhibited by the sensor at the chosen operating temperature of 55 °C. The response magnitude of the developed SAW sensor towards different concentrations of Hg(0) vapor fitted well with the Langmuir extension isotherm (otherwise known as loading ratio correlation (LRC)) which is in agreement with our basic finite element method (FEM) work where an LRC isotherm was observed for a simplified model of the SAW sensor responding to different Hg contents deposited on the Au based electrodes. Overall, the results indicate that the developed SAW sensor can be a potential solution for online selective detection of low concentrations of Hg(0) vapor found in industrial stack effluents.

Determining the Optimum Exposure and Recovery Periods for Efficient Operation of a QCM Based Elemental Mercury Vapor Sensor

In recent years, mass based transducers such as quartz crystal microbalance (QCM) have gained huge interest as potential sensors for online detection of elemental mercury (Hg0) vapor from anthropogenic sources due to their high portability and robust nature enabling them to withstand harsh industrial environments. In this study, we determined the optimal Hg0exposure and recovery times of a QCM based sensor for ensuring its efficient operation while monitoring low concentrations of Hg0vapor (&lt;400 ppbv). The developed sensor was based on an AT-cut quartz substrate and utilized two gold (Au) films on either side of the substrate which functions as the electrodes and selective layer simultaneously. Given the temporal response mechanisms associated with mass based mercury sensors, the experiments involved the variation of Hg0vapor exposure periods while keeping the recovery time constant following each exposure and vice versa. The results indicated that an optimum exposure and recovery periods of 30 and 90 minutes, respectively, can be utilized to acquire the highest response magnitudes and recovery rate towards a certain concentration of Hg0vapor whilst keeping the time it takes to report an accurate reading by the sensor to a minimum level as required in real-world applications.

Silver/gold core/shell nanowire monolayer on a QCM microsensor for enhanced mercury detection

The formation of a silver nanowire monolayer (Ag NWML) galvanically replaced with gold (Au) directly on the electrodes of a quartz crystal microbalance (QCM) transducer for non-spectroscopic based elemental mercury (Hg0) vapor sensing is reported in this study.

An ultrastable Zr metal–organic framework with a thiophene-type ligand containing methyl groups

An ultrastable metal–organic framework can remain intact in pH = 0 to 12 solutions and boiling water, attributed to the steric hindrance and electronic effect of methyl groups as well as strong Zr–O bonds. This MOF exhibits good adsorption and sensing performance for Hg0 vapor because of the presence of thiophene.

Investigations into a thiol-impregnated CaCO3-based adsorbent for mercury removal: a full factorial design approach

We demonstrated removal of Hg0 vapor by adsorbing it on thiol-impregnated calcium carbonate and assessed the significance of temperature and thiol mass in Hg0 removal.

Total Mercury Determination in Petroleum Green Coke and Oily Sludge Samples by Cold Vapor Atomic Fluorescence Spectrometry

A fast, simple and reliable method for Hg determination in green coke and oily sludge samples by atomic fluorescence spectrometry is described. Microwave digestion and extraction procedures were evaluated for highly complex samples of coke and oily sludge. The concentrations of SnCl2 and HCl to promote Hg vapor, were optimized, as well as the concentration of KMnO4, to stabilize the Hg2+ before the atomic vapor formation. Accuracy of the method was evaluated through certified reference material, for green coke, and comparison with cold vapor atomic absorption spectrometry (CV AAS), for oily sludge. Recovery tests were also performed. Limits of detection and quantification were 0.8 and 2.6 µg kg−1, respectively. Ten green coke and nine sludge samples were analysed and Hg concentrations in coke are very low, between 0.005 and 0.065 mg kg−1, but oily sludge samples have high concentrations, ranging from 42.5 to 376.6 mg kg−1, requiring careful management.

The development of AgCl-H&lt;SUB align="right"&gt;2Ti&lt;SUB align="right"&gt;2O&lt;SUB align="right"&gt;5 nanowires composite as a room temperature sensor for the detection of element mercury

A highly sensitive and selective element Hg sensor has been developed by using AgCl-H2Ti2O5 (ATO) nanowires composite as a room temperature sensing material. The AgCl-H2Ti2O5 nanowires composite is prepared by combining hydrothermal and photoreduction chlorination route. The H2Ti2O5 nanowires exhibit a nest meso-architecture network with AgCl nanoparticles attached on the nanowires. The element Hg sensing performance of ATO composite sensor was investigated. The sensor shows good sensitivity, selectivity, fast response and recovery sensing features to large concentrations range of element Hg vapour.

Mercury hair levels and factors that influence exposure for residents of Huancavelica, Peru.

Between 1564 and 1810, nearly 17,000 metric tons of mercury (Hg) vapor was released to the environment during cinnabar refining in the small town of Huancavelica, Peru. The present study characterizes individual exposure to mercury using total and speciated Hg from residential samples, total Hg in hair, and self-reported questionnaire data regarding factors influencing exposure (e.g., frequency of fish consumption, occupation). Total Hg concentrations in hair from 118 participants ranged from 0.10 to 3.6µg/g, similar to concentrations found in the USA and lower than concentrations in other Hg-exposed populations around the world. Pearson's correlation coefficients for data in this study suggest that there is a positive correlation between concentrations of total Hg in hair and concentrations of total Hg in adobe bricks, dirt floors, and surface dust; however, these correlations are not statistically significant. Results of a one-way analysis of variance (ANOVA) identified that total Hg concentrations in hair were significantly related to gender (p<0.001), living in a neighborhood where smelters were previously located (p=0.021), smoking status (p=0.003), frequency of house cleaning (p=0.019), and frequency of fish consumption (p=0.046). These results highlight the need for further studies to better characterize Hg exposure in Huancavelica, particularly as related to residential contamination. A comprehensive analysis of residential Hg contamination and exposure in Huancavelica will guide the development and implementation of mitigation and remediation strategies in the community to reduce potential health risks from residential Hg exposure.

Pollution indexing and health risk assessments of trace elements in indoor dusts from classrooms, living rooms and offices in Ogun State, Nigeria

Heavy metals are known to have a negative impact on human health especially children through oral ingestion. Total metal concentrations were determined in indoor dust from 19 locations consisting of classrooms, living rooms and offices in Ogun State, Nigeria. Digestion and instrumentation reproducibility were validated using certified reference materials (BCR 723 (Road Dust), NIST 2711a (Montana Soil) and NIST SRM 1640e (Trace element in water)). The measured and certified values showed good agreement. Potential threat levels using geo-accumulation (Igeo) and human health risk for both children and adult were assessed. The mean Igeo levels for the classified and probable carcinogens is in the order Cd (4.84)>Cr (3.28)>Pb (2.61)>Ni(2.48)>As (1.64) while other elements are in the order Zn (5.41)>Ba (4.86)>Sr (4.38)>Zn (4.27)>V (3.24)>Cu (3.14)>Hg (2.61)≈TI (2.61). For human health risk, ingestion was the main route of exposure followed by dermal uptake and inhalation. Hazard index values for all studied metals were lower than the safe level of 1 while Hg vapor exhibited the highest risk value (0.13) in the case of children. The carcinogenic risk for As, Cd, Co, Cr, Ni and Pb were all within the acceptable level (10−4–10−6), but there was potential carcinogenic risk posed by Cr for both adults and children.

Gold nanospikes based microsensor as a highly accurate mercury emission monitoring system.

Anthropogenic elemental mercury (Hg0) emission is a serious worldwide environmental problem due to the extreme toxicity of the heavy metal to humans, plants and wildlife. Development of an accurate and cheap microsensor based online monitoring system which can be integrated as part of Hg0 removal and control processes in industry is still a major challenge. Here, we demonstrate that forming Au nanospike structures directly onto the electrodes of a quartz crystal microbalance (QCM) using a novel electrochemical route results in a self-regenerating, highly robust, stable, sensitive and selective Hg0 vapor sensor. The data from a 127 day continuous test performed in the presence of volatile organic compounds and high humidity levels, showed that the sensor with an electrodeposted sensitive layer had 260% higher response magnitude, 3.4 times lower detection limit (~22 μg/m3 or ~2.46 ppbv) and higher accuracy (98% Vs 35%) over a Au control based QCM (unmodified) when exposed to a Hg0 vapor concentration of 10.55 mg/m3 at 101°C. Statistical analysis of the long term data showed that the nano-engineered Hg0 sorption sites on the developed Au nanospikes sensitive layer play a critical role in the enhanced sensitivity and selectivity of the developed sensor towards Hg0 vapor.

Recent Developments in the Study of the Surface-Stability of Platinum and Platinum-Iridium Mass Standards

We review developments in the study of the stability of platinum-iridium standard weights, in particular the kilogram prototypes manufactured from alloy supplied by Johnson Matthey in the 1880s that still stand at the heart of the International System of Units (abbreviated SI from the French: Systeme international d’unites). The SI has long since moved on from length standards based on physical artefacts fabricated from this alloy, but the SI unit of mass is still defi ned in this way, as the mass of a real physical object. The stability of these reference masses has been a concern since the 1930s, with mass loss or gain at the surface being the principal concern. In recent years X-ray photoelectron spectroscopy (XPS) has been particularly valuable in elucidating the types of contamination present and the mechanism by which contamination takes place. While direct studies on the International Prototype Kilogram are understandably diffi cult, at Newcastle University we have examined the surfaces of six Pt mass standards also manufactured in the mid-19th century, using XPS to identify contamination chemically. XPS shows a signifi cant quantity of mercury on the surfaces of all six. The most likely source of Hg vapour is the accidental breakage of thermometers and barometers, and the mechanism of contamination may be similar to the poisoning of platinum group metal (pgm) catalysts by Hg, an effect known for almost a century.

Efficient Hg Vapor Capture with Polysulfide Intercalated Layered Double Hydroxides

We report detailed studies showing that the novel layered polysulfide compounds Sx-LDH (Sx2–, polysulfides, x = 2, 4, 5; LDH, Mg–Al layered double hydroxides) can capture efficiently large quantities of mercury (Hg0) vapor. During the adsorption process, the interlayer polysulfides [Sx]2– react with Hg0 through their S–S bond to produce HgS. The structure of Sx-LDH before and after Hg-adsorption was characterized with X-ray diffraction, vibration spectroscopy, and scanning electron microscopy. The presence of adsorbed Hg was verified by weight gain, inductively coupled plasma atomic emission spectroscopy and X-ray photoelectron spectroscopy. Despite their relatively low surface areas, the S2-LDH, S4-LDH, and S5-LDH samples show excellent Hg capture capacities of 4.9 × 105, 7.4 × 105, and 1.0 × 106 μg/g, respectively, corresponding to 50–100% adsorption rates by weight, highlighting the potential of these materials in natural gas purification. The Hg-capture efficiency and mechanism in Sx-LDH are supported...