The vertical distributions of three heavy metals: Hg, Pb and Cd were determined in 3 cores sampled from two ombrotrophic bogs in the west of Ireland, one at Knockroe Co. Mayo, and the second at ...Letterfrack National Park, Co. Galway. Core chronologies were established using
210Pb dating techniques and were checked with fallout radionuclides from weapons testing. Variations were found in metal concentrations and cumulative inventories of each of the metals within each site and between the two sites. Maximum accumulation rates of the anthropogenically derived elements Hg, Pb, and Cd, were found in peat sediments dated between 1950 and 1970s at both sites.
Pb and Hg accumulation rates are slightly lower than those found in similar studies from remote sites in Europe. Hg accumulation rates are fairly similar to those found in peatlands in America. Unlike the Pb and Hg concentration profiles, the Cd concentration profiles at the Letterfrack site were dominated by a surface enrichment, thought to be due to biological cycling of Cd in the peat. However Cd accumulation rates calculated at the Knockroe site are lower than those observed in Eastern Europe. Local meteorological conditions at the sites chosen for this study may account for the lower concentrations profiles observed when compared with some of the European studies. The similarity between the timing of the increase in metal accumulation rates in peat bogs in Northern America and this study could indicate that long range transportation of trace metals from Northern America may be occurring. Lead accumulations in the surface peat sediments (1993–1996) were between 1.5–3.0
mg
m
−2
yr
−1 and 4–5
mg
m
−2
yr
−1 at Knockroe and Letterfrack, respectively. Mercury accumulation rates for the same period at Knockroe were found to be between 6–11
μg
m
−2
yr
−1, and between 19–24
μg
m
−2
yr
−1 at Letterfrack. A greater variation in surface Cd accumulation rates was observed at both sites, with surface layer accumulation rates varying from 25 to 50
μg
m
−2
yr
−1 at Knockroe and between 166 and 405
μg
m
−2
yr
−1 at Letterfrack. Higher metal concentrations were found at the Letterfrack site, which are most likely due to local sources and the history of the site.
Diffuse anthropogenic and naturally mercury‐enriched areas represent long‐lived sources of elemental mercury to the atmosphere. The Nevada Study and Tests of the Release of Mercury From Soils ...(STORMS) project focused on the measurement of mercury emissions from a naturally enriched area. During the project, concurrent measurements of mercury fluxes from naturally mercury‐enriched substrate were made September 1–4, 1997, using four micrometeorological methods and seven field flux chambers. Ambient air mercury concentrations ranged from 2 to nearly 200 ng m−3 indicating that the field site is a source of atmospheric mercury. The mean daytime mercury fluxes, during conditions of no precipitation, measured with field chambers were 50 to 360 ng m−2 h−1, and with the micrometeorological methods were 230 to 600 ng m−2 h−1. This wide range in mercury emission rates reflects differences in method experimental designs and local source strengths. Mercury fluxes measured by many field chambers were significantly different (p<0.05) but linearly correlated. This indicates that field chambers responded similarly to environmental conditions, but differences in experimental design and site heterogeneity had a significant influence on the magnitude of mercury fluxes. Data developed during the field study demonstrated that field flux chambers are ideal for assessment of the physicochemical processes driving mercury flux and development of an understanding of the magnitude of the influence of individual factors on flux. In general, mean mercury fluxes measured with micrometeorological methods during daytime periods were nearly 3 times higher than mean fluxes measured with field flux chambers. Micrometeorological methods allow for derivation of a representative mercury flux occurring from an unconstrained system and provide an assessment of the actual magnitude and variability of fluxes occurring from an area.
An intercomparison for sampling and analysis of atmospheric mercury species was held in Tuscany, June 1998. Methods for sampling and analysis of total gaseous mercury (TGM), reactive gaseous mercury ...(RGM) and total particulate mercury (TPM) were used in parallel sampling over a period of 4 days. The results show that the different methods employed for TGM compared well whereas RGM and TPM showed a somewhat higher variability. Measurement results of RGM and TPM improved over the time period indicating that activities at the sampling site during set-up and initial sampling affected the results. Especially the TPM measurement results were affected. Additional parallel sampling was performed for two of the TPM methods under more controlled conditions which yielded more comparable results.
An evaluation of mercury observations from North Sea coastal stations during 1995–2002 has been performed. The mercury data originate from EMEP/OSPAR stations in Ireland, Netherlands, Germany, Norway ...and Sweden where mercury in precipitation and Total Gaseous Mercury (TGM) have been measured. A decreasing trend in mercury wet deposition is observed. The decrease is sufficiently large to be significant considering measurement precision and appears to occur at all the studied sites. The reduction in deposition is 10–30% when comparing the two periods 1995–1998 and 1999–2002. The trend is likely to be due to emission controls in Europe. In contrast, no decreasing trend in TGM could be observed during the same time periods. A plausible explanation is that the TGM concentration measured in the OSPAR area to a larger extent than before is dominated by the hemispherical background concentration of TGM.
In an effort to investigate both large-scale (spatial) and short/long-term (temporal) distribution characteristics of atmospheric mercury, we have combined and analyzed the Hg concentration data sets ...collected continuously by four different scientific groups for the areas and periods covering (1) America (three sites near the Canadian Great Lakes (CGL): 1997-2000), (2) Asia (Seoul, Korea (SEL): 1997-2002), (3) Arctic (Alert, Canada (ALT): 1995-2001), and (4) Europe (Mace Head, Ireland (MH): 1996-2002). The mean concentrations of Hg data from those widely dispersed monitoring stations were computed to be (1) 1.58 ± 0.23, 1.69 ± 0.32, and 1.93 ± 0.44 (three sites in CGL), (2) 5.06 ± 2.46 ng m^sup -3^ (SEL), (3) 1.55 ± 0.41 (ALT), and (4) 1.76 ± 0.31 (MH). Intersite relationships were investigated among all different stations using the data groups divided into different temporal intervals. The analysis of diurnal variation patterns of Hg indicated differences in regional source/sink characteristics, with increasing amplitudes of variability toward areas under the strong influence of anthropogenic sources. When the analysis was made over different seasons, the patterns contrasted greatly between the Arctic and the other areas. It was found that the relative enhancement of Hg concentrations was dominant during winter/spring in most areas due to direct or indirect influences of anthropogenic emissions. However, the pattern for the Arctic area was distinguished pronouncedly from others with the spring minimum and summer maximum both of which reflect the potent effects of mercury depletion phenomenon (MDP). By contrast, no long-term trend, either being an increase or decrease, was evident from any of the stations during each respective study period. Although our initial attempts to examine the distribution characteristics of Hg analyzed by different scientific groups were successful, we feel that these efforts should be continued further to extend the compatibility of the global database of Hg.PUBLICATION ABSTRACT
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.
Monitoring of total gaseous mercury (TGM) concentrations has been carried out at Mace Head on the west coast of Ireland and at Zingst on the southern shore-line of the Baltic Sea. We have used the ...continuous measurements to assess long-term trends and seasonal variations of TGM concentrations over the same time period. Between 1998 and 2004 the annually averaged TGM concentrations measured at Mace Head (1.72
ng
m
−3) and Zingst (1.66
ng
m
−3) remained fairly stable. At both stations we measured higher TGM levels during winter months and lower concentrations during summer months. We also observed an unexpected West to East gradient and found that the overall mean Mace Head TGM concentration was 0.06
ng
m
−3 higher than those of Zingst. For the January to June period, the Mace Head TGM values (6-year mean=1.75
ng
m
−3) are significantly elevated compared to the Zingst results (6-year mean=1.64
ng
m
−3). Since no local anthropogenic mercury sources exist near the Mace Head station, enhanced emission from the sea appears to provide the most probable explanation for the observed differences. Multiple regression analysis with the atmospheric mercury concentrations measured at Zingst were made with selected meteorological and air quality parameters (wind component, dew point, dust and NOx concentrations). The short-term variation in the TGM concentrations at Zingst shows a strong positive correlation with weather conditions and selected air quality parameters, making TGM a usable tracer of air masses originating from different source regions.
Six groups participated in an international study of springtime atmospheric mercury depletion events (AMDEs) at Ny-Ålesund in the Norwegian Arctic during April and May 2003 with the aim to compare ...analytical methods for measurements of atmospheric mercury species and study the physical and chemical processes leading to AMDEs. Five groups participated in the method comparison that was conducted at three different locations within Ny-Ålesund. Various automated and manual instrumentation were used to sample, measure and compare gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and mercury associated with particles (Hg-P). The concentration of GEM was reproducible during background conditions. For the first time using ambient air, the statistics associated with round robin test procedures were applied. This was found to be an appropriate tool to investigate the reproducibility of GEM measurements in ambient air. The precision for each group measuring GEM concentrations was found to be consistently good (within 5%). Five AMDEs were recorded during the study. Using four different methods, including single and replicate samples, all groups recorded higher values of RGM and Hg-P during AMDEs. The results show that measuring comparable atmospheric mercury species at both the same and different locations (within the Ny-Ålesund area) is difficult. Not only do site location and site characteristics create challenges when trying to intercompare results but there are difficulties, as well, in obtaining comparable results with similar sampling and analysis methods. Nevertheless, with our current procedures for atmospheric mercury identification we can differentiate with certainty between “high” and “low” concentration values of RGM and Hg-P.
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