Total Gaseous Mercury Concentrations Research Articles

Aircraft measurements of atmospheric mercury over southern and eastern Germany

The concentration of atmospheric mercury was measured on 13 June 1996, during a level flight from Munich to Halle at an altitude of 900 m a.s.l. and back at 2500 m a.s.l. Measurements, corrected for pressure dependence of the instrument response, showed that, with the exception of the southernmost part of the return flight with higher concentrations, mercury was horizontally evenly distributed over a distance of 400 km. The total gaseous mercury (TGM) concentration at an altitude of 2500 m a.s.l. (in the free troposphere) was with 1.635±0.094 ng m −3 ( n=22) slightly lower than at 900 m a.s.l. (in the mixing layer) with 1.774±0.101 ng m −3 ( n=17). Higher TGM concentrations of 2.190±0.255 ng m −3 ( n=2) during the southernmost part of the flight south of Munich and of 2.321±0.133 ng m −3 ( n=8) at the summit of the mountain Wank was attributed to a different air mass. Substantially higher TGM concentrations were observed in the mixing layer downwind of a former chlor–alkali plant at Schkopau. From the downwind/upwind concentration difference and the prevailing wind conditions, a mercury emission of about 0.4 kg d −1 was estimated for the plant area.

International field intercomparison measurements of atmospheric mercury species at Mace Head, Ireland

Eleven laboratories from North America and Europe met at Mace Head, Ireland for the period 11–15 September 1995 for the first international field intercomparison of measurement techniques for atmospheric mercury species in ambient air and precipitation at a marine background location. Different manual methods for the sampling and analysis of total gaseous mercury (TGM) on gold and silver traps were compared with each other and with new automated analyzers. Additionally, particulate-phase mercury (Hg part) in ambient air, total mercury, reactive mercury and methylmercury in precipitation were analyzed by some of the participating laboratories. Whereas measured concentrations of TGM and of total mercury in precipitation show good agreement between the participating laboratories, results for airborne particulate-phase mercury show much higher differences. Two laboratories measured inorganic oxidized gaseous mercury species (IOGM), and obtained levels in the low picogram m -3 range.

Potential sources of atmospheric total gaseous mercury in the St. Lawrence River valley

The potential source contribution function (PSCF) has been used to study the source–receptor relationships for total gaseous mercury (TGM) found in air collected at two sites along the St. Lawrence River valley, namely at St. Anicet and Mingan. TGM concentrations have been measured with high time-resolution analysers (Tekran instrument). The source–receptor analyses have been applied with regards to the seasonality of TGM. Median TGM concentrations are significantly less ( χ 2: α=0.01) during the summertime than other periods at both sites. A total of 12 225 trajectory end-points for St. Anicet and 4480 trajectory end points for Mingan have been used to create potential source area maps. This study identifies preferred potential sources of TGM at St. Anicet during wintertime with strongest probability stretching from the Gulf of Mexico to the southern tip of Greenland. This pattern mimics, the North American anthropogenic Hg emission inventory. Furthermore, some Eurasian mercury air mass intrusions are suggested at Mingan during wintertime. The summertime period at Mingan points out some potential sources stretching from the american mid-west to the St. Lawrence River valley as well as areas around the southern tip of the Hudson Bay.

Simultaneous measurements of total gaseous mercury at four sites on a 800 km transect: spatial distribution and short-time variability of total gaseous mercury over central Europe

Over a distance of approximately 800 km simultaneous measurements of total gaseous mercury (TGM) were performed at four sampling sites between Stockholm and Berlin. The time resolution of mercury concentration measurements was 5 min. During the sampling period from 26 June to 7 July 1995, event sampling for precipitation was carried out using bulk samplers. In addition to the mercury data, the most common meteorological and air-quality parameters were determined. Comparing the TGM background concentrations at the four sites, a weak but statistically significant south-to-north declining TGM gradient was found. From the most southern sampling site to the northern most site median values of 1.93, 1.78, 1.53 and 1.54 ng m -3 TGM were detected. Compared with the median TGM concentration observed at the two Swedish sites, the regional background concentration near Berlin was elevated by about 25%. Whereas the 0.5 h average TGM concentration varies at the Swedish sampling sites in a very narrow range of only 0.69 ng m -3, a much broader range of 3.28 ng m -3 was observed at the southern sites. The increased TGM variability near Berlin was characterised by a diurnal cycle with a distinct maximum in the early morning hours (about 4:00 a.m.) before sun rise. The short time variability of the TGM concentration measured at the four sites on the south-to-north transect shows regional differences. A decreasing variability from the most southern to the most northern site became evident.

The atmospheric cycling and air–sea exchange of mercury species in the South and equatorial Atlantic Ocean

Measurements of gas-, particle- and precipitation-phases of atmospheric mercury (Hg) were made in the South and equatorial Atlantic Ocean as part of the 1996 IOC Trace Metal Baseline Study (Montevideo, Uruguay to Barbados). Total gaseous mercury (TGM) ranged from 1.17 to 1.99 ng m −3, with a weighted mean of 1.61±0.09 ng m −3. These values compare well with Pacific Ocean data and earlier results from the Atlantic. The open-ocean samples recorded a distinctive inter-hemispheric gradient, which is consistent with a long-lived trace gas emitted to a greater extent from the Northern than from the Southern Hemisphere. Correlations with surface 222Rn measurements indicate an influence of regional terrestrial sources on open-ocean TGM concentrations. Total Hg in precipitation ranged from 10 to 99 pM (volume-weighted average: 17.8±2.9 pM). On average, about 72% of the total Hg was “reactive” (i.e., reducible by SnCl 2). The data showed an apparent rapid nonlinear decrease in concentration with event size (“washout curve”). The wet depositional flux was estimated at 18–36 nmol m −2 yr −1 (4–7 μg m −2 yr −1), which is slightly lower than that found in mid-continental locations of North America (6–12 μg m −2 yr −1). 210Pb analyses indicate a strong impact of particles on rain Hg concentrations. Particle-phase Hg (range 5–25 fmol m −3; mean 12±1 fmol m −3; 66% “reactive”) was comparable to values over the equatorial Pacific. The dry depositional flux is ca. 0.4 nmol m −2 yr −1, or 0.4–1.0% of the wet flux. Particle-phase Hg concentrations did not change significantly when African dust was present during sampling. However, the Hg/Al ratios were consistent with crustal values during the dust periods. The residence time of TGM was calculated to be 1.3–3.4 yr in this region, based on standing stock estimates. Incubation of rainwater added to surface seawater gave reduction rates [i.e., production of elemental Hg (Hg°); 1.6–4.3% d of total Hg added] comparable to additions of inorganic ionic standards, indicating that Hg +2 from precipitation is reduced in a similar manner in surface waters. Thus, precipitation-phase Hg is generally available for evasion to the atmosphere following deposition to the surface ocean, effectively enhancing the mobility and residence time of Hg at the Earth's surface.

Trends in atmospheric mercury concentrations at the summit of the Wank mountain, Southern Germany

Total gaseous mercury (TGM) has been monitored at the summit of the Wank mountain (1780 m a.s.l.) in the Bavarian Alps since March 1990. A statistical analysis of the data set until May 1996 consisting of 1670 individual TGM measurements shows a linear decrease of 0.169 ± 0.009 ng Hg m −3 yr −1, i.e. about 7% per year. The seasonal variation shows maximum TGM concentrations in March and minima in October–December. The frequency of occurrence of extremely high TGM concentrations and the amplitude of the seasonal variation decreased over the observation time. The observed decrease of the TGM concentration is in agreement with measurements in Scandinavia, indicating that the measurements at Wank are representative for the region of central and northern Europe. The decrease in TGM concentration of 23.3% between 1990 and 1994 was consistent with decreases of 20.4 and 21.2%, respectively, observed by us over the northern and the southern Atlantic Ocean. This and the observation of a decreasing trend in mercury wet deposition in the U.S.A. indicate the global significance of the TGM trends observed in Europe. Several causes may add up, but this 45% change in TGM concentrations observed over the period of 6 years cannot be plausibly explained without a substantial decrease of anthropogenic mercury emissions on both regional and global scales. Such decrease, however, is difficult to reconcile with most of the current anthropogenic emission inventories. This points to possible gaps in our understanding of the anthropogenic emission processes.

Field observations of total gaseous mercury behaviour: Interactions with ozone concentration and water vapour mixing ratio in air at a rural site

Total Gaseous Mercury (TGM) data (n = 5125) measured from September 9 to November 30, 1994 in Southern Quebec with an automatic TGM analyser (Tekran®) are used to study the behaviour of TGM with ozone and the water vapour mixing ratio. Results show, as a whole, no straight-forward correlation between TGM and ozone concentrations. A significant correlation between TGM and water vapour mixing ratio was measured. Some back reduction of Hg(II) to Hgo in the aqueous phase and subsequent evaporation of Hg0 according to Henry's Law is expected. The latter correlation seems to be partly ozone dependent since under ‘clean conditions’ (ozone > 30 ppbv) the slope of TGM vs the water vapour mixing ratio is twice that during ‘polluted conditions’ (ozone > 30 ppbv) which suggests some compensation effects under polluted conditions (counteracting the back-reduction of Hg(II) to Hgo in the aqueous phase). Oxidation of TGM by ozone during high moisture conditions (water vapour mixing ratio ∼14g/kg) seems to appear at the threshold ozone concentration ⩾ 30 ppbv.

Determination of atmospheric mercury during the North sea experiment

Total gaseous mercury (TGM) and rainwater were collected on board of two research vessels (F. S. ALKOR and R.V. BELGICA) positioned 200 km apart in the center of the North Sea during the North Sea Experiment, September 1991. On the F. S. ALKOR (up-wind ship) TGM concentrations ranged from 0.7 to 2.6 ng·m−3 with an average of 1.5 ng m−3 and on the R. V. BELGICA (down-wind ship) TGM ranged from 0.7 to 1.9 ng·m−3 with an average of 1.2 ng·m−3. An average 20% decrease is observed from the up-wind to the down wind ship. which may largely be affected by entrainment into the free troposphere. An overall removal (entrainment) velocity of 0.95 cm·s−1 was calculated for the whole experiment. The average removal velocity was 0.5 cm·s−1 for dry periods and varied between 1 to 5 cm·s−1 during rain events. Rainwater concentrations varied between 5 and 25 ng·1−1. Based on these data an annual wet deposition flux of 1.08 ng Hg cm−2 yr1− was estimated for the North Sea.

Indication of change in global and regional trends of atmospheric Mercury concentrations

In 1992 we reported an indication of global increase of atmospheric mercury concentrations obtained from the measurements of total gaseous mercury (TGM) over the Atlantic Ocean during five ship cruises between 1977 and 1990 [Slemr and Langer, 1992]. The observed rate of concentration increase and its implications were consistent with previous measurements and the trends derived from analyses of dated peat bog and lake sediment records. To avoid uncertainties from the intermittent character of ship measurements and to obtain more detailed information about this trend, we have continuously monitored TGM concentrations at the summit of the Wank mountain (1780 m a.s.l.) near Garmisch‐Partenkirchen in southern Germany since March 1990. These measurements and the results of another cruise in 1994 indicate a significant change in the trend of global TGM concentration, with a decrease of about 22% in the years between 1990 and 1994. This decrease is most likely the result of reduction in coal consumption and control measures taken in the OECD countries.

Mercury-cycling in surface waters and in the atmosphere ? Species analysis for the investigation of transformation and transport properties of mercury

The river Elbe has been one of the most contaminated rivers with regard to mercury for many years. In 1991 a length-profile has been measured for mercury and methylmercury (CH3Hg+) from Obristvi, Czech Republic, to the German bight. Total mercury has been measured by cold vapor atomic absorption spectrometry (CVAAS). The organo mercury compounds have been separated by high performance liquid chromatography (HPLC) connected on-line to an atomic fluorescence spectrometer (AFS) by a continuous flow-system. Total mercury up to 120 mg Hg+/kg and CH3Hg+ concentrations up to 130 μg CH3 Hg+/kg could be detected in special sites. The formation of CH3Hg+ in sediments can be caused besides the methylation of mercury, by sulphate reducing or methanogenic bacteria and transmethylation reactions with organometals. Atmospheric mercury concentrations have been measured at three different European sites. Samples have been collected on goldcoated glass balls or on quartz wool, respectively. After thermal desorption mercury has been determined using the two step amalgamation technique with AFS detection. Compared to natural background concentrations of total gaseous mercury (TGM), slightly increased levels could be detected at a rural site in Germany. This increase can probably be explained by long-range transport processes. Within the vicinity of a inactivated mercury production plant high concentrations of up to 13.5 ng/m3 particle associated mercury (Hgpart) have been detected. Consequently, dry deposition of mercury in the particulate form can intensify the total deposition flux close to Hg-emitting sources.

Baseline atmospheric mercury studies at Ross Island, Antarctica

The first extended baseline studies of total gaseous mercury (TGM) and dimethylmercury (DMM) in Antarctica are reported. Mean TGM concentrations of 0.52, 0.60 and 0.52 ng m−3 were obtained for three consecutive years at the southern tip of Ross Island (77°S). The levels of DMM in Antarctica are less than 10% of the TGM, and frequently fall below the limit of detection. These results represent the lowest TGM concentrations recorded globally and extend into polar regions the observation of a decrease in atmospheric mercury concentration with increasing latitude.

Baseline concentration and speciation of atmospheric mercury at baring head (41°S), New Zealand

Abstract Baseline atmospheric mercury measurements were made at Baring Head (41°S) in New Zealand. Total gaseous mercury (TGM) concentrations varied between 0.42 and 1.69 ng m‐3, exhibiting a mean value of 0.84 ± 0.31 ng m‐3. The speciation was dominated by inorganic mercury (mean concentration 0.57 ng m‐3). The dimethylmercury (DMM) contribution ranged from 3 to 81% of the TGM. The occasionally high DMM loading was interpreted to result from contamination from the nearby city of Wellington, indicating that TGM values presented here are upper estimates for pristine air. Nonetheless, the atmospheric mercury data presented here are very low in relation to other baseline measurements.

Distribution, speciation, and budget of atmospheric mercury

Total gaseous mercury (TGM) concentrations over the Atlantic Ocean and over Central Europe were measured repeatedly in the years 1978–1981. The latitudinal TGM distribution showed a pronounced and reproducible interhemispherical difference with higher TGM concentrations in the Northern Hemisphere. TGM was found to be vertically well mixed within the troposphere. The TGM concentration seems to increase with time at a rate of 10±8%/yr in the Northern and 8±3%/yr in the Southern Hemisphere. Measurements of mercury speciation showed that elemental mercury is the main TGM component contributing more than 92% and 83% of TGM in marine and continental air, respectively. The tropospheric mercury burden was calculated to be 6×109g. The interhemispheric distribution and temporal and spatial variability of TGM imply a tropospheric residence time of TGM of about 1 yr. Sink strengths calculated independently from the measured mercury concentration on particles and in rainwater are consistent with the above figures.

High-altitude meteorological research station to be set up in the Himalayan ranges

Diurnal and seasonal variation of atmospheric Total Gaseous Mercury (TGM) were studied for the first time in a high altitude station, Kodaikanal, India. To achieve this, an automated continuous mercury vapour analyzer was used in the study area between November, 2012 and September, 2013. In this pilot study the annual mean atmospheric TGM concentration was found to be 1.53 ng/m3, with a range from 0.83 to 3.25 ng/m3 and with a lognormal frequency distribution pattern. The mean seasonal concentration of TGM was found to be in the following order: summer > winter > northeast monsoon > southwest monsoon. Significant temporal differences in the TGM concentrations indicated strong environmental control regulated by seasonal changes in this high altitude rural area. The study further revealed that the day time TGM concentration was strongly modified by solar radiation, evaporation and rainfall. Moreover, this is the first study in the Indian subcontinent with continuous monitoring of the temporal changes of TGM and its relation to other micrometeorological factors.