Reactive Mercury Research Articles

Arctic atmospheric contaminants in NE Greenland: levels, variations, origins, transport, transformations and trends 1990–2001

This review is based on the results obtained from the Danish AMAP programme for the Arctic atmosphere during the 1990s. The purpose of the programme is to quantify the pollution, apportion source contributions, follow the trends, and identify midlatitude source areas and transport pathways. The project has been carried out in North Greenland as integrated monitoring, which is an interacting combination of field measurements and model calculations of atmospheric transport and transformation in the Northern Hemisphere. At the monitoring site at Station Nord the large and seasonally recurrent variations in the pollutant concentrations are testimony to the influence in this region of the phenomenon of Arctic Haze. These results can only be understood in terms of long range transport from distant pollution sources. The measurements also comprise a large number of particle-born elements. These results are used to build receptor models, which show that the ambient concentrations and their variations to a high degree can be explained by the influence of only four source types of both natural and anthropogenic nature. The challenging phenomena of atmospheric ozone and mercury depletion around Polar sunrise have been studied at Station Nord over several years. The results show that these two phenomena are closely connected, presumably through photochemical reactions with atmospheric halogens released from sea ice. A large-scale Eulerian model system for the Northern Hemisphere has been developed in this AMAP project. The validity of the model is illustrated by comparisons between measured and calculated air concentrations. The model has been used to calculate both the vertical distribution and the atmospheric depositions for several pollutants at various locations in Greenland and split into quantified contributions from different and geographically distant source areas. Mercury deposition estimates for the Northern Hemisphere are also presented. They show that the mercury depletion events are accompanied by very intense depositions to land and sea of reactive mercury that may seriously affect the Arctic ecosystems. Finally, measurement and model data are combined to demonstrate, despite considerable meteorological noise, that ambient air concentrations in North-eastern Greenland have decreased during the last decade. Quantified trends, attributable to emission reductions in distant source areas, are presented for several pollutants.

Distribution of Different Species of Mercury in Baihua Lake, Guizhou Province

均匀布点采集百花湖表层水样44个,对水样不同形态汞含量进行了分析,并现场测定水质参数。采用经典统计学与半变异函数拟合相结合的方法,研究了百花湖表层水中不同形态汞含量的空间变异性。根据半变异函数拟合的结果,在ArcGIS软件的支持下进行克立格插值,以此来揭示百花湖表层水中不同形态汞含量的空间分布规律。研究表明:百花湖表层水中的汞污染主要来自上游,随水体流动汞污染减少;但也有一些区域可能因富营养化而使颗粒态汞和总汞含量增加。;Forty-four surface water samples were collected in Baihua Lake, Guizhou Province.The different species of mercury and water quality parameters, such as reactive mercury, dissolved mercury, particulate mercury, were tested.The spatial variability of different species of mercury in the surface water of Baihua Lake were studied based on the mathematical statistics and Geostatistics methods (Kriging).On the basis of the models of semivariance fitness, we used ArcGIS software to proceed Kriging interpolator to reveal the distribution patterns of different species of mercuiy in the surface water of Baihua Lake.The results indicate that mercury contamination in the surface water of Baihua Lake is due to headwaters, then mercury contents will decrease with the direction of flowing water.But in the region of eutrophication, the contents of particulate mercury and total mercury increase.

Mercury in contaminated sediments and pore waters enriched in sulphate (Tagus Estuary, Portugal)

Three sediment cores, collected nearby the effluent of a chlor-alkali industry, were sliced in 0.5-cm layers and centrifuged for pore water extraction. Mercury, Fe and Mn were determined in the solids as total concentration, hydroxylamine extractable fraction and HCl extractable fraction. Sulphur was determined in the HCl extraction. Total and reactive mercury, chlorinity, S 2−, SO 4 2−, total Fe, and total Mn were measured in pore waters. The solids contained 3.0–60 nmol g −1 of total Hg and pore waters 70–5800 pM of total Hg and 1.8–76 pM of reactive mercury. Pore waters presented 2.3–94 times more sulphate than the overlying estuarine waters due to the input from the industry. In layers where hydroxylamine extractable Fe exhibited a broad maximum (precipitation of Fe-oxides) sulphate was reduced to S 2−. The competition between the high content of SO 4 2− and Fe(III) as electron acceptors, in chemical reactions occurring in the upper sediments, may explain the co-existence of S 2− and Fe-oxides in the same layers. Mercury was detected in the hydroxylamine extracts (20–29 nmolg −1) in the layers where Fe-oxides were formed, and reactive dissolved Hg showed minimum concentrations. The excess of sulphate in pore waters favoured the abundant Fe-oxides in the upper solid sediments, which appear to work as a barrier limiting the escape of mercury to the water column.

Mercury contaminations from gold mining using amalgamation technique in Xiaoqinling Region, Shanxi Province, PR China

In China, rudimentary procedures (gold extraction using amalgamation technique) are still used, especially in Xiaoqinling region of Shanxi Province. Gold was discovered in Tongguan County in Xiaoqinling region about 900 years ago, and almost every family has been involved in small-scale gold mining activities for a long time. This region lies in a semiarid zone, and gold mining activities are distributed along several streams that are up reaches of Yellow River. Every year about 120 t mercury are released into environment due to gold extracting, with 38.0% released into atmosphere, 62.0% into solid tailings and 0.003% into river directly with the tailing water. In this paper, different mercury species in water samples collected in this area were measured. The results indicated that the average dissolved mercury concentration in water was 0.74μg/l, varied from 0.11 to 3.10μg/l, and the particulate mercury concentrations were much higher (0.10∼258.62μg/l). In filtered water, the reactive mercury was predominant, ranged from 7.76% to 62.68%. A preliminary study indicated that the study area is seriously contaminated by mercury due to gold extraction activities, and further study is on-going to evaluate ecological and human health effects from mercury contamination in this area.

Mercury throughout polar sunrise 2002

Mercury depletion events (MDEs) are now a well-known phenomenon occurring in Polar Regions during the springtime. During these MDEs gaseous elemental mercury (GEM) is chemically transformed to less volatile mercury species (operationally defined as reactive gaseous mercury (RGM) and mercury associated with particles (PM)). Various measurement techniques have been employed to measure these different mercury species. However, it is still to be established what species of mercury are being measured in the Arctic air during depletion events. A study was undertaken in the spring of 2002 at Alert, Canada to investigate several techniques for the measurement of these reactive mercury species under Arctic conditions during polar sunrise. This study compared automated GEM, manual and automated RGM and PM measurement techniques as well as a method for total atmospheric mercury. Results showed that manual and automated sampling techniques compared reasonably well. Relative differences in RGM and PM concentrations over land and over the ocean were investigated. PM concentrations were consistently higher than RGM, with the same relative abundance at both sample sites. Additionally, flux measurements were undertaken, including chamber and micrometeorological methods.

The distribution and speciation of mercury in Wujiang river

Concentrations of reactive, dissolved, particulate and total mercury in water samples were determined at 41 locations throughout the Wujiang River Basin, China. The sampling campaign was carried out 15∼30 July 2002. During the collection of water samples for Hg analyses, other parameters were measured in situ (dissolved oxygen, pH, temperature and EC). The average concentration of the reactive mercury in surface water was 1.5 ng/L. The concentration of total mercury ranged from 10.9 to 329.6 ng/L, with a geometric mean of 44.4 ng/L, and the dissolved mercury was from 1.0 to 49.2 ng/L, with a geometric mean of 7.1 ng/L. The proportion of reactive to total mercury was typically less than 5%, and the particulate to total mercury, with 90% of values higher than 50%. The pilot study indicated that Wujiang River is contaminated by mercury in a certain extent.

Gaseous mercury exchange rate between air and water over Baihua reservir, Guizhou, China during cold season

Field measurement campaigns over lake water surface at Baihua reservoir in Guiyang, Southwestern China were conducted to measure mercury flux using a dynamic flux chamber technique coupled with automatic mercury vapor-phase analyzer from October 30 to November 4, 2001. The dynamic flux chamber is made of quartz glass, and has low blanks. Water samples were collected, and dissolved gaseous mercury (DGM), reactive and total mercury concentrations in water were measured using gold trap pre-concentration and AFS detection method. Meanwhile meteorological parameters, such as wind speed, wind direction, intensity of solar radiation, air and water temperature, and relative humidity were monitored using a portable weather station. Water surface is a net atmospheric mercury emission source even at cold season (autumn), and the average mercury emission rate is 3.0 ng/m 2 .h. We observed a strong correlation between wind speed and mercury emission rate, suggesting that strong wind facilitate mercury evaporation process from the water system during cold season. No significant correlations between Hg emission rate and solar radiation, water and air temperature were obtained.

The concentration and distribution of different mercury species in the water columns of BaiHua reservoir

Three study sites were selected at the upper, middle and down reach of the Baihua Reservoir and the water samples from different depth were collected in June 8 to 9, 2002. Dissolved gaseous mercury (DGM), reactive and total mercury concentrations in water profiles were measured by trap pre-concentration and CVAFS detection method. The results indicated, as a whole, the concentrations of all mercury species at the three sites gradually decreased along the water flow direction, and the highest concentration site presented in the upper stream (HuaQiao) of the reservoir. In water column (except bottom water), the highest average total and reactive mercury concentrations are 35.9 ng/L and 5.7 ng/L, respectively. Total mercury concentrations in bottom water reach 807-1963 ng/L. Sediments are potential mercury source to water column of the reservoir. A preliminary study indicted that Baihua Reservoir is seriously contaminated in terms of mercury due to mercury discharge from Guizhou Organic Chemical Plant (GOCP). It is essential to carry out further study on mercury cycling in Baihua Reservoir to evaluate ecological effects from mercury contamination.

Mercury speciation into tropospheric clouds

Cloud water has been sampled at the Puy De Dome (France) for mercury determination. The analysis of these samples gave us concentrations from about 10 to 50 ng/L and from about 0.8 to 3.5 ng/L for total mercury (Hg T ) and for reactive mercury (Hg R ) respectively. In a previous study based on analysis of Total Gaseous Mercury in the interstitial phase of clouds, mercury concentrations in cloud water were estimated to be around 1 μg/L. Comparing this assumption with our measurements, we suggest that Hg° could be the principal mercury species in cloud water. A kinetic study, which compares reduction and oxidation processes, supports our hypothesis. Assuming our assumption to be true, precipitation is likely to contribute significantly to elemental mercury deposition.

Effect of Organic Matter on Determination of Reactive Mercury in Contaminated Waters

Dissolved reactive mercury was determined in water samples from Ria da Aveiro, a coastal lagoon contaminated by mercury. Concentrations increased with acid dilution to a maximum of 193% in samples containing organic matter with high aromaticity, as inferred from absorbances at 250, 280 and 365 nm. Laboratory experiments with potassium hydrogenoftalate and humic acids solutions proved the influence of aromaticity in complexing mercury, how acid dilution protonates the aromatic Hg-complexes and consequent release of labile forms of mercury to solution. On the basis of these results it is proposed that natural waters from mercury contaminated ecosystems should be analysed without dilutions, otherwise additional studies should be performed to access the protonation of mercury organic complexes.

Mercury Cycling in Lake Gordon and Lake Pedder, Tasmania (Australia). II: Catchment Processes

The sources and concentrations of total mercury (total Hg) and methylmercury (MeHg) in the upper catchment of the Lake Gordon/Lake Pedder system in Tasmania, Australia were investig- ated. The catchment area, which contains over 50% wetlands, is located in a temperate region with no obvious point sources of mercury. Surface waters in the region had concentrations of total Hg ranging from 1.2 to 14.4 ng L −1 and MeHg from <0.04 to 1.4 ng L −1 . MeHg concentrations were seasonally dependent, with the highest concentrations occurring in summer. Sediments/soils in the catchment had concentrations of total Hg ranging from 4.0 to 194 ng g −1 and MeHg from <0.02 to 20.1 ng g −1 . The low concentrations of total Hg confirmed that this region is pristine as regards to mercury and has no geological enrichment of total Hg. The highest total Hg and MeHg concentrations in both sediment/soils and waters were found in bogs whereas the lowest concentrations typically occurred on the wetland plains. MeHg concentrations in bog and swamp sediments were correlated with the organic matter content (r = 0.942, P < 0.001). Acid volatile sulfide (AVS) measurements indicate that in most sediments AVS was greater than total Hg. Given the high reactivity of inorganic mercury and sulfide, this suggests that most of the particulate mercury in sediments is present as mercuric sulfide. The yield of MeHg from the catchment was estimated to be 3.2 mg ha −1 yr −1 and is higher than published rates measured in non-contaminated temperate catchments in the northern hemisphere. The higher yield was attributed to the generally warmer climatic conditions that favour net methylation and the relatively high rainfall (2-3 m yr −1 ) of the region, which supplies reactive inorganic mercury to the active zones of mercury methylation and also flushes MeHg from the catchment.

On the analysis of mercuric nitrate in flue gas by GC-MS

Recent research has demonstrated that in a simulated flue gas stream containing NO(2) and SO(2) elemental mercury is initially captured on a carbon or manganese oxide sorbent. After approximately an hour, however, mercury breaks through relatively rapidly, and the volatile form of mercury emitted is an oxidized species. The volatile mercury species emitted from a granular MnO(2) sorbent was trapped in an impinger containing cold acetonitrile. Subsequent evaporation of 95% of the acetonitrile in a Kuderna-Danish apparatus and gas chromatography (GC) of the concentrate resulted in a single mercury-containing GC peak at 5.5 min; the retention time and mass spectrum of this compound matched exactly those of a standard mercury(II) nitrate hydrate, Hg(NO(3))(2).H(2)O dissolved in acetonitrile. The volatile mercury component analyzed from injection of this standard solution was shown to be a form of methylmercury that is produced in the GC column by reaction of the highly reactive mercury nitrate with the methylsiloxane GC phase. Because the on-column derivatization reaction seems to be unique to mercury nitrate, the GC-MS (gas chromatography-mass spectroscopic) analysis provides strong evidence for identification of the trapped oxidized mercury species as mercury nitrate although, because the nitrate becomes detached from the mercury atom in the on-column reaction, the identity is not proven.

Photo-induced formation of dissolved gaseous mercury in coastal and offshore seawater of the Mediterranean basin

The first measurements on the daily trend of dissolved gaseous mercury (DGM) concentration determined in coastal and offshore waters of the Mediterranean basin are reported. Marked daily behaviour tracking solar radiation has been observed at the coastal sampling station with DGM values ranging from 11.0 to 38.9 pg/l. Contrary to these observations the DGM values in offshore water samples (11.9–20.0 pg/l) were independent of the sampling time, thus identifying the absence of higher levels during the hours of maximum insolation. The availability of Hg 2+ substrate necessary for the photo-reaction processes of DGM formation has been evaluated by measuring the reactive mercury concentration. In offshore waters the lower DGM concentrations are attributable to the substrate as a limiting factor. The highest concentration of DOC measured in coastal seawater with respect to the offshore one could moreover enhance the reaction rates of DGM production through the formation of inorganic mercury complexes and weaker organic associations.

Atmospheric mercury concentrations: measurements and profiles near snow and ice surfaces in the Canadian Arctic during Alert 2000

Gaseous elemental mercury (GEM) concentration measurements were made during the Alert 2000 campaign in Alert, Nunavut, Canada, between February and May 2000. GEM exhibits dramatic mercury depletion events (MDE) concurrently with ozone in the troposphere during the Arctic springtime. Using a cold regions pyrolysis unit, it was confirmed that GEM is converted to more reactive mercury species during the MDEs. It was determined that on average 48% of this converted GEM was recovered through pyrolysis suggesting that the remaining converted GEM is deposited on the snow surfaces. Samples collected during this campaign showed an approximate 20 fold increase in mercury concentrations in the snow from the dark to light periods. Vertical gradient air profiling experiments were conducted. In the non-depletion periods GEM was found to be invariant in the air column between surface and 1–2 m heights. During a depletion period, GEM was found to be invariant in the air column except at the surface where a noticeable increase in the GEM concentration was observed. Concurrent ozone concentration profiles showed a small gradient in the air column but a sharp decrease in ozone concentration at the surface. Other profile studies showed a 41% average GEM concentration difference between the interstitial air in the snow pack and ∼2 m above the surface suggesting that GEM is emitted from the snow pack. Further profile studies showed that during MDEs surface level GEM exhibits spikes of mercury concentrations that were over double the ambient GEM concentrations. It is thought that the solar radiation may reduce reactive mercury that is deposited on the snow surface during a MDE back to its elemental form which is then increasingly released from the snow pack as the temperature increases during the day. This is observed when wind speeds are very low.

Levels of Reactive Mercury and Silver in Sediments from the Port of Ensenada, Baja California, Mexico

Levels of Reactive Mercury and Silver in Sediments from the Port of Ensenada, Baja California, Mexico

Levels of reactive mercury and silver in sediments from the port of Ensenada, Baja California, Mexico.

Levels of reactive mercury and silver in sediments from the port of Ensenada, Baja California, Mexico.

Formation of artifact methylmercury during extraction from a sediment reference material.

We examined monomethylmercury (MMHg) in sediment reference material IAEA-405 and sediments from Long Island Sound. MMHg was extracted by both aqueous distillation and leaching with dilute solutions of nitric acid. MMHg was formed from both ambient and added inorganic mercury in extracts of IAEA-405 by either technique. Artifact MMHg in IAEA-405 was related linearly with ambient reactive mercury (HgR) in leachates having > 1.2 M acid, but little or no artifact was measured in less acidic extracts. Addition of potassium chloride enhanced extraction of HgR from LAEA-405 but had no effect on artifact MMHg for each leachate molarity tested. Mercury methylation occurred in solution and was a function of both the availability of HgR and a methylation potential, being limited by HgR in less acidic solutions (0.5-1.2 M) and by the methylation potential in more acidic ones (> 1.2 M). Formation of artifact MMHg in Long Island Sound sediments was inconclusive, but additions of inorganic mercury demonstrated that a potential exists. A potential for abiotic mercury methylation seems always present in sediment, and the availability of HgR appears to control MMHg production under environmental conditions. Abiotic methylation of mercury may occur in environs where the reactivity of inorganic mercury is enhanced, such as river-seawater mixing zones.

Distribution of particulate and reactive mercury in surface waters of Swedish forest lakes — an empirically based predictive model

The partition coefficient ( K d) expresses the ratio between particulate bound and dissolved metals. In lake dynamic modelling, it is used to distribute the total load between the dissolved and particulate routes of lake transport. An empirically based model for prediction and evaluation of a modified partition coefficient for mercury (Hg) in lake water has been developed using field data from 25 Swedish lakes. As a substitute for dissolved Hg determined by filtration, this study uses the easy reducible (or reactive) proportion of Hg in water samples and the modified partition coefficient is here denoted K d *. The model relates K d * for Hg to the best correlating of several lake specific environmental variables, resulting in an r 2-value of 0.69. K d * was found to decrease with increasing suspended particulate matter (SPM) concentration, iron concentration (Fe) and ratio of lake to drainage area ( a/ADA). Interpretations of the model parameters were discussed in light of the clusters of statistically and functionally related variables they represent. The negative correlation between K d * and SPM is possibly due to the particle concentration effect, which seems to be valid also for the definition used here for the partition coefficient. For K d the particle concentration effect is often explained by an exponential relationship between colloids and SPM which results in relatively more colloid bound metals at low SPM concentrations. The fraction of colloid bound metals is counted with the ‘dissolved’ fraction which decreases the K d. Influences of spurious correlations on the relationship between K d * and SPM have been assessed and found to contribute to the statistical correlation. The negative correlation with iron can also be accounted for by Hg association with small particles (iron/manganese oxides and hydroxides, possibly in association with humic matter). The influence of the morphometric factor a/ADA is probably due to differences in K d * with different Hg transport paths (direct deposition on the lake surface is believed to decrease K d *). The model was tested using stability tests, which indicated that other related variables could replace the given model parameters. The model parameter interpretations, in terms of clusters of related variables would, however, have been similar.

Storage of natural water samples for total and reactive mercury analysis in PET bottles

Poly(ethylene terephthalate) (PET) bottles used in commercially available mineral water were compared to Teflon bottles for sampling and storage of river water samples prior to mercury determination. The metal concentration was in the range 0.3–2.0 ng L−1 for the reactive species, and in the range 1–9 ng L−1 for total mercury. A paired t-test showed no significant difference in the results for both reactive (p = 0.011) and total Hg (p = 0.024). Storage time was studied for PET bottles, using synthetic samples spiked with 10 ng L−1 Hg2+ ions, using two different types of preservation: (a) by freezing at −18 °C, and (b) by the addition of BrCl solution. Both procedures yielded the same results up to the 14th day of storage (ANOVA, p = 0.72 for BrCl and p = 0.12 for freezing). The freezing procedure proved to be more suitable for longer storage times, i.e., up to 40 d (significance level of 0.03, ANOVA).

Speciation of mercury in sediments of the Seine estuary (France)

Although the parameters regulating mercury methylation in sediments are fairly well known, conditions controlling the formation and mobilization of methylmercury in aquatic sediments are still poorly understood. In this work the environmental factors governing the distribution and behaviour of total mercury and methylmercury within the Seine estuary have been assessed through the analysis of sediment cores. Box-cores taken at coastal, estuarine and riverine locations in the period 1994–1997 were analysed for bulk sediment and porewater total mercury and methylmercury concentrations, as well as a number of other chemical variables. Levels of total mercury in sediment (300–1000 ng g−1) were found to be uniform all over the estuary and did not show significant temporal or spatial variations. On the contrary, the distribution of methylmercury was distinct from that of its inorganic form since it displayed seasonal and spatial variability. Maximum methylmercury concentrations (up to 6 ng g−1) and percentages (up to 2%) were obtained at the estuarine location with peak loading just below the sediment surface and a decreasing level in the deeper layers. As total mercury and methylmercury were nor correlated, the temporal and spatial behaviour of methylmercury appeared to reflect variations in salinity, redox potential and the sulphate reduction rate. Low concentrations of reactive mercury, but very high total mercury levels, were measured in the porewaters (10–400 ng l−1), with maximum values at the sediment/water interface. In spite of a high proportion of organically complexed dissolved mercury, methylmercury in porewaters was mainly below the detection limit of the method (2 ng l−1). From mercury speciation in the solid phase and dependence of its dissolved fraction on iron and manganese in porewater, the source and distribution of mercury in porewaters are discussed. Copyright © 1999 John Wiley & Sons, Ltd.