The history of mercury pollution near the Spolana chlor-alkali plant (Neratovice, Czech Republic) as recorded by Scots pine tree rings and other bioindicators.

We assessed >100years of mercury (Hg) pollution recorded in the tree rings of Scots Pine near a Czech chlor-alkali plant operating since 1941. Hg concentrations in tree rings increased with the launching of plant operations and decreased when Hg emissions decreased in 1975 due to an upgrade in production technology. Similar to traditional bioindicators of pollution such as pine needles, bark and forest floor humus, Hg concentrations in Scots Pine boles decreased with distance from the plant. Mean Hg in pine bole in the 1940s ranged from 32.5µg/kg Hg at a distance of 0.5km from the plant to 5.4µg/kg at a distance of >4.7km, where tree ring Hg was the same as at a reference site, and other bioindicators also suggest that the effect of the plant was no longer discernible. Tree ring Hg concentrations decreased by 8-29µg/kg since the 1940s at all study sites including the reference site. The lack of exact correspondence between changes at the plant and tree ring Hg indicated some smearing of the signal due to lateral translocation of Hg from sapwood to heartwood. Bole Hg concentrations reflected local and regional atmospheric Hg concentrations, and not Hg wet deposition.

The influence of sample drying procedures on mercury concentrations analyzed in soils.

Methods commonly used for soil sample preparation may be unsuitable for measuring Hg concentrations due to the possible loss of volatile Hg species when drying at higher temperatures. Here, the effects of freeze-drying, air drying at 25°C and oven-drying at 105°C on Hg concentrations in two soil types and three standard reference materials were tested. Two soils with different levels of Hg contamination and three reference materials were examined. A systematic decrease of Hg concentrations was observed in air-dried (24 %) and oven-dried (3 %) contaminated upland soils in comparison to freeze-dried control samples. The 105°C oven drying also led to loss of Hg from reference materials (5 %-8 % in comparison with the certified Hg concentration). Different results from the drying of sterilized reference materials and natural soils were probably related to the extent of microbiological activity, demonstrating the importance of this parameter in sample preparation for Hg analysis.

Spring snowmelt and mercury export from a forested catchment in the Czech Republic, Central Europe.

The annual output of filtered mercury (Hg) from Lesni potok catchment, a forested ecosystem in central Europe, was estimated at 0.87 µg m⁻². More than 70% of the annual mercury output flux occurred during the spring snowmelt period. The snowmelt period is the most important part of the hydrological year in central European forested ecosystems. Average filtered concentrations of mercury (17.8 ng L⁻¹) and DOC (10.5 mg L⁻¹) in the stream water during snowmelt were greater than average values for the rest of the hydrological year. Omitting frequent daily or bi-daily filtered mercury analysis during the snowmelt caused underestimation of the annual mercury output flux (0.79 µg m⁻²) and decreased the accuracy of flux calculations.

Effect of fire on pools of mercury in forest soil, Central Europe.

In year 2006, 17.9 ha of forest was burned during a forest fire at the Bohemian Switzerland National Park found in northern part of Czech Republic (CR), central Europe. Complete combustion of organic soil (4,039 t) on the burned area caused volatilization of 1.34 +/- 0.07 kg of Hg. Thus Hg emissions due to fire amounted to 75.1 g ha(-1). The average burned forested areas in CR for the period 2000-2006 were reported at 356 ha with estimated Hg emissions at 26.7 kg year(-1), while the average anthropogenic emissions in the same period amounted to 3 t year(-1). Thus estimated mean emissions of Hg from burned forest soil in the period 2000-2006 reached 1% of the annual anthropogenic Hg emissions.

Distribution and speciation of mercury in mine waste dumps.

Mine waste dumps of historic mercury mines represent environmental threat. In the central Czech Republic, Hg ores were mined at two sites for more than 150 years. Mine wastes collected from dumps near Hg mines were elevated in total Hg (up to 120 microg(-1)). Thermal-desorption method revealed that most of Hg (>80%) in studied waste material was present as cinnabar (HgS), that is relatively stable in soils and resistant to formation of highly toxic methyl-Hg. Nevertheless minor part (<14%) of total Hg was identified as mineral surface bound Hg, which might undergo methylation and thus represents potential long-term environmental risk.