Air Hg Concentrations Research Articles

Soil-Air Mercury Flux near a Large Industrial Emission Source before and after Closure (Flin Flon, Manitoba, Canada).

Prior to its closure, the base-metal smelter in Flin Flon, Manitoba, Canada was one of the North America's largest mercury (Hg) emission sources. Our project objective was to understand the exchange of Hg between the soil and the air before and after the smelter closure. Field and laboratory Hg flux measurements were conducted to identify the controlling variables and used for spatial and temporal scaling. Study results showed that deposition from the smelter resulted in the surrounding soil being enriched in Hg (up to 99 μg g(-1)) as well as other metals. During the period of smelter operation, air concentrations were elevated (30 ± 19 ng m(-3)), and the soil was a net Hg sink (daily flux: -3.8 ng m(-2) h(-1)). Following the smelter closure, air Hg(0) concentrations were reduced, and the soils had large emissions (daily flux: 108 ng m(-2) h(-1)). The annual scaling of soil Hg emissions following the smelter closure indicated that the landscape impacted by smelter deposition emitted or re-emitted almost 100 kg per year. Elevated soil Hg concentrations and emissions are predicted to continue for hundreds of years before background concentrations are re-established. Overall, the results indicate that legacy Hg deposition will continue to cycle in the environment long after point-source reductions.

Application of tree rings [dendrochemistry] for detecting historical trends in air Hg concentrations across multiple scales

Tree rings are a useful long term monitor of climate change indicators and certain atmospheric constituents. Since we have no long-term historical record of air mercury (Hg) concentrations, and previous research demonstrates atmospheric uptake of Hg into vegetative biomass, we hypothesized that tree rings would be a useful archive for monitoring changes in local, regional, and global air Hg concentrations. We developed and tested a method for measurement of Hg in tree rings, and then investigated our hypothesis using species within the genus Pinus. Mercury concentrations declined along a coast-to-interior (California-to-Nevada, USA) gradient with highest mean concentrations (5.7 ng/g) at the coast, and lowest (<1.2 ng/g) at inland locations. Tree ring Hg concentrations recorded the impact of local sources and indicate increasing global concentrations over time. The data also indicate that concentrations are higher in areas impacted by marine air, and this suggests that the atmospheric chemistry is influencing assimilation. Future research should address species- and age-specific variation in the sensitivity of tree-ring samples as proxy data for atmospheric Hg concentrations. Tree rings show great potential as passive recorders of atmospheric Hg for long time periods (centuries to millennia) at time steps of ≤5 years.

Probabilistic meta-analysis of risk from the exposure to Hg in artisanal gold mining communities in Colombia

Colombia is one of the largest per capita mercury polluters in the world as a consequence of its artisanal gold mining activities. The severity of this problem in terms of potential health effects was evaluated by means of a probabilistic risk assessment carried out in the twelve departments (or provinces) in Colombia with the largest gold production. The two exposure pathways included in the risk assessment were inhalation of elemental Hg vapors and ingestion of fish contaminated with methyl mercury. Exposure parameters for the adult population (especially rates of fish consumption) were obtained from nation-wide surveys and concentrations of Hg in air and of methyl-mercury in fish were gathered from previous scientific studies. Fish consumption varied between departments and ranged from 0 to 0.3kgd−1. Average concentrations of total mercury in fish (70 data) ranged from 0.026 to 3.3μgg−1. A total of 550 individual measurements of Hg in workshop air (ranging from <DL to 1mgm−3) and 261 measurements of Hg in outdoor air (ranging from <DL to 0.652mgm−3) were used to generate the probability distributions used as concentration terms in the calculation of risk. All but two of the distributions of Hazard Quotients (HQ) associated with ingestion of Hg-contaminated fish for the twelve regions evaluated presented median values higher than the threshold value of 1 and the 95th percentiles ranged from 4 to 90. In the case of exposure to Hg vapors, minimum values of HQ for the general population exceeded 1 in all the towns included in this study, and the HQs for miner-smelters burning the amalgam is two orders of magnitude higher, reaching values of 200 for the 95th percentile. Even acknowledging the conservative assumptions included in the risk assessment and the uncertainties associated with it, its results clearly reveal the exorbitant levels of risk endured not only by miner-smelters but also by the general population of artisanal gold mining communities in Colombia.

Variations in Atmospheric Mercury Concentration in Kagoshima City During 2010 – 2012

The atmospheric mercury (Hg) concentration was determined during Aug. 2010 – Jun. 2012 in Kagoshima City and compared with values reported for 1996 – 2002. The average concentrations were 10.8 ng m−3, 13.4 ± 10.1 ng m−3, 5.52 ± 3.85 ng m−3 and 1.9 ± 0.5 ng m−3 for 1996 – 1997, 1997 – 1998, 1999 – 2002 and 2010 – 2012, respectively. The recent atmospheric Hg level in Kagoshima City was the same as the Japanese background levels. The Hg concentration was higher in the summer than other seasons and a significant correlation was obtained between the Hg concentration and the air temperature. These results suggested that the evaporation of Hg from surfaces according to temperature was an important factor to increase the Hg concentration in ambient air. On the other hand, the atmospheric Hg concentration could not be enhanced directly by the fumarolic activity of the Sakurajima volcano located in Kagoshima City. In this study, 3.5 ng m−3 (= mean + 3 standard deviation) was defined as a background level in the Kagoshima City. The days were observed to have higher values than the background level in Kagoshima City; there were 5 days during the investigation period. From the back-trajectory over China, it could be considered that the observed high concentration of Hg in air showed the possibility of long-range transportation from the East Asia region.

Evaluation of Potential Mercury Releases from Medical Isotope Waste

Mercuric (Hg) nitrate is used as a catalyst in the medical isotope production process at Atomic Energy of Canada Limited (AECL) Chalk River Laboratories (Chalk River, ON) to ensure consistent Mo-99 target dissolution. The subsequent high level radiological liquid waste is cemented into stainless-steel pails and shipped to a waste management area for long-term storage. Previous studies have confirmed that Hg tends to bind and precipitate I-131, thus minimizing its release to the environment. In order to assess the situation and evaluate the need for Hg monitoring, environmental media (vegetation, surface soil, groundwater, and air) surrounding this waste storage area were sampled and results were compared with applicable guidelines and/or background areas at AECL and other locations.Mercury in groundwater, surface soil, and vegetation were found to be below applicable environmental guidelines and comparable to background locations. Atmospheric Hg near waste storage was found to be elevated above background, but well below applicable guidelines for continuous monitoring. Concentrations of Hg in air also dissipated quickly and were comparable to background within 60 to 80 m from source.The atmospheric Hg monitor used in this study (TEKRAN 2537B) constitutes part of the custom-built portable TEAMS trailer that was designed to provide Chalk River Laboratories with the capability to measure, monitor and model Hg emissions, along with other radiological and non-radiological contaminants, for a wide range of situations. The trailer can also be easily re-configured to adapt to different monitoring needs.

Building upon the Conceptual Model for Soil Mercury Flux: Evidence of a Link Between Moisture Evaporation and Hg Evasion

Parameters known to influence mercury (Hg) release from soils include substrate and air Hg concentration, light, atmospheric oxidants, temperature, and soil moisture. However, for low Hg-containing soils, the influence of these parameters has been shown to vary across space and time. Here, we expand upon previous work by investigating whether soil–water evaporative loss, which integrates the influence of multiple parameters, could be applied for predicting Hg flux from soil with low Hg concentrations when bare and planted. To investigate our hypothesis, Hg flux was measured from three soil types (<100 ng Hg g−1). When these soils were saturated, flux was suppressed. Soil moisture evaporative stage was used to partition the parameters most important for controlling Hg flux as the soils dried. Classification and regression tree (CART) analyses showed that soil moisture was the most important parameter predicting Hg flux. Results also showed an important predictor for Hg flux was whether actual evaporation (E a) was equal to potential evaporation (E p) or E a < E p. Depending on evaporative stage, the parameters with the next highest correlation to Hg flux were light, temperature, and soil moisture evaporation rate. The presence of vegetation also influenced flux with lower Hg flux when the plants were transpiring. Results indicate for those developing models that estimate Hg flux from low Hg-containing soils, soil moisture and evaporative stage are useful tools for predicting flux.

Mercury release flux and its influencing factors at the air-water interface in paddy field in Chongqing, China

The exchange of mercury (Hg) across the air-water interface is an important part of Hg biogeochemical cycle. Mercury fluxes across the air-water interface in paddy fields were measured by a Dynamic Flux Chamber (DFC) coupled with a Lumex® multifunctional mercury analyzer RA-915+ at two sites (Chengjiang (CJ) and Caoshang (CS)) in Beibei, Chongqing, China in 2008. The results showed that mercury emission followed a power-law relationship with solar radiation and air temperature, and it increased exponentially with water temperature at both sites. Mercury emission was mainly influenced by the solubility of gaseous elemental Hg, photo-thermal effect, electron activity (Eh) and air Hg concentrations. Solar radiation made the greatest direct contribution to mercury emission during the daytime (0.80), with an 83.60% contribution, whereas at nighttime the water temperature (0.72) contributed to 71.65% of emissions. The temperature gradient between water and air might also influenced mercury emission across the air/water interface at nighttime. These findings suggest that paddy fields could act as a significant source of atmospheric mercury, and it can contribute significantly to the atmospheric mercury in a local region.

Investigating sources of gaseous oxidized mercury in dry deposition at three sites across Florida, USA

Abstract. During 2009–2010, the State of Florida established a series of air quality monitoring stations to collect data for development of a statewide total maximum daily load (TMDL) for mercury (Hg). At three of these sites, located near Ft. Lauderdale (DVE), Pensacola (OLF), and Tampa Bay (TPA), passive samplers for the measurement of air Hg concentrations and surrogate surfaces for measurement of Hg dry deposition were deployed. While it is known that Hg in wet deposition in Florida is high compared to the rest of the United States, there is little information on Hg dry deposition. The objectives of the work were to: (1) investigate the utility of passive sampling systems for Hg in an area with low and consistent air concentrations as measured by the Tekran® mercury measurement system, (2) estimate dry deposition of gaseous oxidized Hg, and (3) investigate potential sources. This paper focuses on Objective 3. All sites were situated within 15 km of 1000 MW electricity generating plants (EGPs) and major highways. Bi-weekly dry deposition and passive sampler Hg uptake were not directly correlated with the automated Tekran® system measurements, and there was limited agreement between these systems for periods of high deposition. Using diel, biweekly, and seasonal Hg observations, and ancillary data collected at each site, the potential sources of Hg deposited to surrogate surfaces were investigated. With this information, we conclude that there are three major processes/sources contributing to Hg dry deposition in Florida, with these varying as a function of location and time of year. These include: (1) in situ oxidation of locally and regionally derived Hg facilitated by mobile source emissions, (2) indirect and direct inputs of Hg from local EGPs, and (3) direct input of Hg associated with long range transport of air from the northeastern United States. Based on data collected with the surrogate surface sampling system, natural background dry deposition for Florida is estimated to be 0.03 ng m−2 h−1. Deposition associated with mobile sources is 0.10 ng m−2 h−1 at TPA and DVE, and 0.03 ng m−2 h−1 at OLF. Long range transport contributes 0.8 ng m−2 h−1 in the spring. At DVE ~0.10 ng m−2 h−1 is contributed directly or indirectly from local point sources. We also suggest based on the data collected with the Tekran® and passive sampling systems that different chemical forms of GOM are associated with each of these sources.

Environmental geochemistry of an active Hg mine in Xunyang, Shaanxi Province, China

Abstract The Xunyang Hg mine (XMM) situated in Shaanxi Province is an active Hg mine in China. Gaseous elemental Hg (GEM) concentrations in ambient air were determined to evaluate its distribution pattern as a consequence of the active mining and retorting in the region. Total Hg (HgT) and methylmercury (MeHg) concentrations in riparian soil, sediment and rice grain samples (polished) as well as Hg speciation in surface water samples were measured to show local dispersion of Hg contamination. As expected, elevated concentrations of GEM were found, ranging from 7.4 to 410 ng m −3 . High concentrations of HgT and MeHg were also obtained in riparian soils, ranged from 5.4 to 120 mg kg −1 and 1.2 to 11 μg kg −1 , respectively. Concentrations of HgT and MeHg in sediment samples varied widely from 0.048 to 1600 mg kg −1 and 1.0 to 39 μg kg −1 , respectively. Surface water samples showed elevated HgT concentrations, ranging from 6.2 to 23,500 ng L −1 , but low MeHg concentrations, ranging from 0.022 to 3.7 ng L −1 . Rice samples exhibited high concentrations of 50–200 μg kg −1 in HgT and of 8.2–80 μg kg −1 in MeHg. The spatial distribution patterns of Hg speciation in the local environmental compartments suggest that the XMM is the source of Hg contaminations in the study area.

Ambient Air Particulate and Particulate-Bound Hg (Hg[p]) Concentration: Dry Deposition Study Using a Cold Vapor Atomic Fluorescence Spectrometry (CVAFS) Analyzer in Westin Park, Taiwan

Ambient air particulate-bound Hg (Hg[p]) concentrations, dry deposition and dry deposition velocity were measured using a cold vapor atomic fluorescence spectrometry (CVAFS) analyzer in the spring season (between March 2011 to June 2011) at the Westin Park sampling site, in Sha-Lu central Taiwan. The results indicated that the highest ambient air Hg(p) concentrations total suspended particles (TSP) occurred in April (0.050 ng/m3) while the lowest ambient air Hg(p) concentrations in TSP occurred in March (0.011 ng/m3). Moreover, the results showed that the highest Hg(p) dry deposition occurred in June (0.019 ng/m2*min), while the lowest ambient air Hg(p) dry deposition occurred in March (0.002 ng/m2*min). In addition, the results also showed that the highest and lowest dry deposition velocity for ambient air Hg(p) occurred in June (2.46 cm/sec) and May (0.18 cm/sec), respectively. Finally, the average highest and lowest dry deposition velocity for ambient air particulates occurred in March (9.010 cm/sec) and April (2.09 cm/sec), respectively.

Testing the use of passive sampling systems for understanding air mercury concentrations and dry deposition across Florida, USA

This paper describes the use of passive sampling systems and surrogate surfaces for monitoring atmospheric mercury (Hg) concentrations and dry deposition, respectively, in Florida,USA. Although this area has been reported to have low air concentrations, wet deposition values, reported by the Mercury Deposition Network, are some of the highest in the United States, and little is known about the magnitude of dry deposition to the region. To address this uncertainty, dry deposition of gaseous oxidized mercury (GOM) was estimated based on data collected using surrogate surfaces and through the application of a dry deposition model that utilized Tekran® Mercury Analyzer data for three sites (Davie near Fort Lauderdale, Tampa and Pensacola) over a year (July 2009-July 2010). Passive sampler systems for monitoring GOM and total gaseous mercury (TGM) concentrations were also deployed. In general, higher surrogate surface deposition, and GOM and TGM passive sampler uptake were observed at the DVE location. Across all sites, empirically derived dry deposition was higher than that determined using modeled values. Tekran® Instrument derived GOM concentrations, as well as modeled deposition rates, followed the same seasonal and spatial patterns as that measured by the samplers, however there were some spatial and temporal trends captured by the samplers that were not seen in the Tekran® derived data. Results indicate that these samplers may be applied to identify spatial and temporal trends in air Hg concentrations and potential deposition at sites with low and fairly constant GOM concentrations as reported by the Tekran® system (2–8pgm-3). When viewed collectively, trends in sampler and Tekran® derived data also suggest the potential for different forms of GOM in air. Using empirical and modeled values, dry deposition in Florida during the year of this study could account for 1.5 to 14% of total annual Hg deposition (wet+dry).

Mercury emissions from natural surfaces highly impacted by human activities in Guangzhou province, South China

Abstract In situ measurements of mercury (Hg) exchange fluxes between natural surfaces and atmosphere were carried out at 14 sampling sites in Guangdong province, southern China, which is the most populated and industrialized area in China. It is found Hg fluxes varied significantly from different landscapes. The average fluxes of Hg from agricultural bare soils, dry paddy soils, and wet paddy fields were in the ranges of 18.2–135, 2.7–14.2, and 1.4–22.8 ng m −2 h −1 , respectively. Average fluxes for bare soil and forest soil were 135 and 6.6 ng m −2 h −1 , respectively. We did not observe significant correlations between Hg fluxes and soil Hg concentrations for all the sampling sites, and this is probably due to the different soil utilizations at the sampling sites. Dry paddy soils and wet paddy fields exhibited relatively lower Hg fluxes than other agricultural soils. Dry paddy soils had low soil porosity which might minimize the interface of soil to the atmosphere. Besides, low penetrations of solar radiation and relevant biotic activities in dry paddy soils might also result in low air Hg concentrations in soil pool which in turn result in minimal diffusions of Hg to the atmosphere. Hg fluxes from wet paddy fields were mainly controlled by soil Hg concentrations, which affected the Hg contents of above water layer and could also release Hg 0 through the water layer to the atmosphere. It was also found that sites close to large anthropogenic point sources exhibited relatively higher emission fluxes, indicating potential of Hg reemissions from historical deposited Hg from anthropogenic sources.

Potential Indoor Air Exposures and Health Risks from Mercury Off-Gassing of Coal Potential Indoor Air Exposures and Health Risks from Mercury Off-Gassing of Coal

Coal combustion products (CCPs), including coal fly ash (CFA) and flue gas desulfurization (FGD) gypsum, have gained accepted use as substitutes for traditional substances in building materials. Because of the presence of mercury (Hg) in CCP materials, some concerns have been raised regarding the potential for Hg to off-gas from building materials into indoor air. Risk assessment offers a well-accepted, objective framework in which to determine whether such off-gassing could result in human exposures of health concern. We thus conducted a screening-level human health risk assessment to estimate worst-case inhalation risks from indoor air exposures to Hg for multiple CCP utilization scenarios: (1) FGD-gypsum wallboard used in a school classroom or home, and (2) CFA concrete blocks used in a school classroom. For CFA concrete, published experimental data for Hg emissions during dry curing of concrete were used to calculate a high-end emission rate, and based on extrapolation of these data, an emission rate considered to be more representative of long-term emissions. For wallboard, Hg emission rates were estimated using published data from flux chamber experiments measuring Hg volatilization from FGD-gypsum wallboard samples. Together with the estimated emission rates and conservative values for other parameters (e.g., building characteristics, exposure conditions), a steady-state indoor air model was used to predict indoor air Hg concentrations. Even for parameters intended to overstate potential exposures, predicted indoor air Hg concentrations were typically below background indoor Hg levels. Additionally, estimated Hg air concentrations were well below established inhalation toxicity criteria (noncancer hazard quotients \[HQs\] ranged from 0.00004 to 0.016). Based on our findings, we conclude that potential indoor air Hg exposures associated with the use of CCPs in concrete and wallboard building materials in either classroom settings or residential homes are associated with negligible human health risks.

Field controlled experiments of mercury accumulation in crops from air and soil

Field open top chambers (OTCs) and soil mercury (Hg) enriched experiments were employed to study the influence of Hg concentrations in air and soil on the Hg accumulation in the organs of maize (Zea mays L.) and wheat (Triticum aestivum L.). Results showed that Hg concentrations in foliages were correlated significantly (p < 0.05) with air Hg concentrations but insignificantly correlated with soil Hg concentrations, indicating that Hg in crop foliages was mainly from air. Hg concentrations in roots were generally correlated with soil Hg concentrations (p < 0.05) but insignificantly correlated with air Hg concentrations, indicating that Hg in crop roots was mainly from soil. No significant correlations were found between Hg concentrations in stems and those in air and soil. However, Hg concentrations in upper stems were usually higher than those in bottom stems, implying air Hg might have stronger influence than soil Hg on stem Hg accumulation.

Mercury fluxes from air/surface interfaces in paddy field and dry land

Abstract In order to provide insight into the characteristics of Hg exchange in soil/water–air surface from cropland (including paddy field and dry land), Hg fluxes were measured in Chengjiang. Mercury fluxes were measured using the dynamic flux chamber method, coupled with a Lumex® multifunctional Hg analyzer RA-915 + (Lumex Ltd., Russia). The Hg fluxes from paddy field and dry land were alternatively measured every 30 min. Data were collected for 24–48 h once per month for 5 months. Mercury fluxes in both fields were synchronously measured under the same conditions to compare Hg emissions between paddy field and dry land over diurnal and seasonal periods and find out what factors affect Hg emission on each surface. These results indicated that air Hg concentrations at the monitoring site was double the value observed at the global background sites in Europe and North America. The Hg release fluxes were 46.5 ± 22.8 ng m −2 h −1 in the warm season, 15.5 ± 18.8 ng m −2 h −1 in the cold season for dry land, and 23.8 ± 15.6 ng m −2 h −1 in the warm season, 6.3 ± 11.9 ng m −2 h −1 in the cold season for paddy field. Solar radiation is important in the emission of Hg over both sites. Hg exchange at the soil/air and water/air interfaces showed temporal variations. The amount of Hg emission from dry land was higher than that from the paddy field, and the emission in daytime was higher than that at night. Moreover, Hg emissions from land covered by crops, was lower than that for bare land.

Mercury contamination and its potential health effects in a lead–zinc mining area in the karst region of Guangxi, China

Mercury contamination of the environment is of worldwide concern because of its global presence and its potent neurotoxicity. Mining, smelting and the electronics industry are the main sources of Hg pollution. However, few studies have been performed to investigate systemic Hg contamination in metal mining regions. In this study, concentrations of Hg in air, farmland soil, and crops were measured in a Pb–Zn mining area in the karst region of Guangxi, China. Key factors that could affect Hg distribution, such as the fate of waste ore and waste residue, were analyzed. Geo-statistical methods were adopted to analyze the characteristics of spatial structure and distribution of Hg. The results show that Hg contamination in this region is serious. The total mercury (T-Hg) content is far higher than the Level II Limit Value of Chinese Soil Standards of 0.30 mg kg−1, showing obvious directional characteristics from WNW to ESE. Highest Hg concentrations were found in the WNW portion of the study area. The contamination of paddy soil is higher than that in dry farmland soil. The vertical distribution of T-Hg and its decrease with depth suggest that the important sources are waste water irrigation and the improper disposal of the waste ore and waste rock. The T-Hg concentrations in the agricultural products examined exceed the Chinese tolerance value (0.02 mg kg−1 for rice and 0.01 mg kg−1 for vegetables), indicating the seriousness of the problem. The ecological environment and the safety of food grown in this mining area are being affected, with the result that human health is possibly being affected.

Laboratory Investigation of Hg Release from Flue Gas Desulfurization Products

Flue gas desulfurization (FGD) is a process applied to remove acid deposition precursors from the coal combustion air stream. This process also removes mercury (Hg) resulting in accumulation of this element in FGD produced solids. This project investigated Hg release from FGD materials to the air and water. Hg concentrations in the synthetic leaching precipitation procedure extracts, designed to simulate rainwater pH conditions, were in general <10 ng L(-1). Unlike coal fly ash, which has been found to adsorb Hg from the air, FGD materials were found to release Hg to the air over time with the addition of water a dominant environmental factor promoting release. The chemistry of the atmosphere to which the FGD materials were exposed (i.e., air Hg concentration and presence of oxidants), as well as that of the material (i.e., salts removed), was found to influence the magnitude of emissions. Although this work showed a component of the Hg captured by the FGD process could be released to the air under laboratory conditions, the potential for release under disposal and beneficial use conditions needs to be determined.

Concentrations of As, Be, Cr, Hg, Mn, and Ni in ambient air at four urban locations in Japan

The metal concentrations of As, Be, Cr, Hg, Mn, and Ni in ambient air were measured at four sites in Japan from October 1997 to March 2006. The mean metal concentration data measured from the four sites (K1, K2, M, and Y) are found on the order of Mn > Cr-Ni > As > Hg > Be. The concentrations of Mn with the highest mean value were fairly variable across four sites such as 45.9 +/- 42.8 (K1), 25.6 +/- 19.4 (K2), 22.5 +/- 19.7 (M), and 25.4 +/- 19.8 ng m(-3) (Y). In contrast, the concentrations of Be with the lowest mean value were less variable across four sites with means of 0.03 to 0.04 ng m(-3). Inspection of the seasonal patterns indicates the peak occurrence of most metals during spring, although relative dominance during winter is seen at the most polluted area (K1). Evaluation of long-term patterns indicates that the noticeably high values of metals in the early stage of study reduced gradually across the years, although the metal concentration levels in most areas were affected significantly by anthropogenic activities. However, efforts to control pollution levels seemed to gradually contribute to a decrease in metal concentration levels of all study sites through the years.

Monitoring mercury in two South African herbaria

Mercury [Hg] emissions from old plant collections treated with mercuric chloride (HgCl 2) may present a high health risk for staff working in certain herbaria. The present study evaluated Hg concentrations in ambient air, plant specimens and biological samples from staff working in the Pretoria National Herbarium (PRE) and the H.G.W.J. Schweickerdt Herbarium (PRU), University of Pretoria. Biological samples from a group of 15 people exposed to HgCl 2 in herbaria and a non-exposed control group of five people were studied. Additionally, plant samples from herbarium specimens treated and non-treated with HgCl 2 were analysed. Plant materials treated with HgCl 2 had persistent high concentrations of Hg in the range of 114–432 µg g − 1 , whereas untreated materials were in the range of 0.20–0.45 µg g − 1 . The HgCl 2-treated plant specimens induced elevated concentrations of Hg into the herbarium rooms near storage cabinets, where up to 1 μg m − 3 of Hg was measured in the air of both herbaria. However, no significant difference in mean Hg concentrations in hair was found between herbarium workers and members of the control group, 0.46 and 0.64 µg g − 1 respectively ( p 0.05, Student's t-test). For both groups, Hg concentrations were lower than that indicated by the World Health Organization [WHO] for non-exposed adults, namely 2 µg g − 1 . The mean concentration of total Hg in urine from the mercury-exposed herbarium group, 2.28 µg g − 1 creatinine, was significantly higher than in the control group, 1.05 µg g − 1 of creatinine. For both populations, the concentrations of Hg in their urine were below the threshold Hg values set by the WHO, i.e., 5 µg g − 1 creatinine. We concluded that there was no strong response by individual herbarium staff from long-term exposure to Hg concentrations in the range of 0.28–1.1 μg m − 3 .

Sensitivity of the global atmospheric cycle of mercury to emissions

Abstract A systematic investigation of the impact of current uncertainties in Hg emissions from specific source categories on global air Hg concentrations is presented. First, the uncertainties in different emission source categories are discussed and then the results of a base simulation and three sensitivity simulations conducted with a global chemical transport model for mercury (CTM-Hg) are presented. The total Hg emissions in the four scenarios range from 6600 to 9400 Mg/a. The sensitivity studies investigate the impact of the range in uncertainty in natural emissions, emissions of previously deposited Hg, and anthropogenic emissions both in China and worldwide, while taking into account constraints imposed by available data (current/pre-industrial emission ratio of 2–4). In one case, natural emissions and emissions of previously deposited Hg were changed to represent a mid point of the range of values found in the literature. This lead to a 16% increase in background emissions, i.e., natural emissions and emissions of previously deposited Hg combined. Increasing natural emissions by 16% or Chinese anthropogenic emissions by 100% yielded atmospheric Hg concentrations comparable with those measured across the globe without any changes to the atmospheric chemistry. Increasing natural emissions and emissions of previously deposited Hg by 16% and all anthropogenic emissions by 100% as compared to the base scenario yielded atmospheric Hg concentrations that were not compatible with measurements and changes in the chemical behavior of Hg in the atmosphere would be required to yield results that are consistent with observed Hg concentrations. The current uncertainty in total Hg emissions at the global scale is placed at about a factor of two.