Factors controlling Mn and Zn contents in leaves of silver and downy birch in acidified soils of Central Europe and Norway.

In Central European mountain forests, foliar element concentrations (FECs) of manganese (Mn) in silver birch (Betula pendula Roth) are occasionally approximately 5000 mg kg-1 and can represent stress for these plants. Factors controlling the Mn FECs in silver birch in Central Europe and downy birch (Betula pubescens Ehrh.) in Norway have not yet been fully deciphered. In this study, the Central European silver birch specimens were sampled in 2022. The samples were analysed by X-ray fluorescence spectroscopy. Norwegian data were obtained from the literature. Mn FECs are commonly negatively correlated with magnesium and, in certain areas, with potassium. Mn FECs are simultaneously elevated with zinc (Zn), likely because of soil acidification and anthropogenic emissions. Mn FECs in birch were previously thought to be related to altitude, which was assigned to (i) downslope washes of Mn or (ii) the historical load of acid emissions. The highest Mn FECs in silver birch were found in the Harz Mountains, Germany, and have been attributed to historical atmospheric contamination and the abundance of soils on felsic silicic rocks poorly buffering acid rains. The historical emission load from iron and steel production was hypothesised to be the cause of elevated Mn and Zn FECs in the Beskid Mountains, Czech Republic. Mn FECs in birch can be used to map historical soil acidification caused by industrial emissions. Zn FECs in birches can reflect soil contamination by this element.

Reconstructing atmospheric Hg levels near the oldest chemical factory in central Europe using a tree ring archive.

The Chemical Factory in Marktredwitz (CFM) is known as the oldest chemical factory in Germany (1778-1985), and from the beginning of the 20th century focused primarily on the production of mercury (Hg) compounds. Due to extensive pollution, together with employee health issues, the CFM was shut in 1985 by a government order and remediation works proceeded from 1986 to 1993. In this study, tree ring archives of European Larch (Larix decidua Mill.) were used to reconstruct changes of air Hg levels near the CFM. Mercury concentrations in larch boles decreased from 80.6 µg kg-1 at a distance of 0.34 km-3.4 µg kg-1 at a distance of 16 km. The temporal trend of atmospheric Hg emissions from the CFM reconstructed from the tree ring archives showed two main peaks. The first was in the 1920s, with a maximum tree ring Hg concentration 249.1 ± 43.9 µg kg-1 coinciding with when the factory had a worldwide monopoly on the production of Hg-based seed dressing fungicide. The second peak in the 1970s, with a maximum tree ring Hg concentration of 116.4 ± 6.3 µg kg-1, was associated with a peak in the general usage and production of Hg chemicals and goods. We used the tree ring record to reconstruct past atmospheric Hg levels using a simple model of Hg distribution between the larch tree rings and atmosphere. The precision of the tree ring model was checked against the results of air Hg measurements during the CFM remediation 30 years ago. According to the tree ring archives, the highest air Hg concentrations in the 1920s in Marktredwitz were over 70 ng m-3. Current air Hg levels of 1.18 ng m-3, assessed in the city of Marktredwitz, indicate the lowest air Hg in the past 150 years, underscoring the effective remediation of the CFM premises 30 years ago.

Uptake of Cd, Pb, U, and Zn by plants in floodplain pollution hotspots contributes to secondary contamination.

Willows, woody plants of genus Salix common in floodplains of temperate regions, act as plant pumps and translocate the Cd and Zn in the soil profiles of uncontaminated and weakly contaminated floodplains from the sediment bulk to the top strata. We suggest this process occurs because the Cd and Zn concentrations in willow leaves exceed those in the sediments. Senescing foliage of plant species common in floodplains can increase the Cd and Zn ratios as compared to other elements (Pb and common 'lithogenic elements' such as Al) in the top strata of all floodplains, including those that have been severely contaminated. The top enrichment is caused by the root uptake of specific elements by growing plants, which is followed by foliage deposition. Neither the shallow groundwater nor the plant foliage shows that Cd, Zn, and Pb concentrations are related to those in the sediments, but they clearly reflect the shallow groundwater pH, with the risk element mobilised by the acidity that is typical for the subsurface sediments in floodplains. The effect that plants have on the Pb in floodplains is significantly lower than that observed for Cd and Zn, while U can be considered even less mobile than Pb. Groundwater and plant leaves can contribute to secondary contamination with Cd and Zn from floodplain pollution hotspots, meaning that plants can accumulate these elements on the floodplain surface or even return them back to the fluvial transport, even if bank erosion would not occur. For Pb and U at the sites studied, these risks were negligible.

Experimental in situ transformation of Pb smelter fly ash in acidic soils.

Soils in the vicinity of nonferrous metal smelters are often highly polluted by inorganic contaminants released from particulate emissions. We used a technique with double polyamide experimental bags (1-µm mesh) to study the in situ transformation of fly ash (FA) from a secondary Pb smelter in acidic soil profiles. Between 62 and 66% of the FA dissolved after one year's exposure in the soils, leading to complete dissolution of primary caracolite (Na(3)Pb(2)(SO(4))(3)Cl) and KPb(2)Cl(5), with formation of secondary anglesite (PbSO(4)), minor PbSO(3), and trace carbonates. Release of Pb was pH-dependent, whereas not for Cd and Zn. Significant amounts of metals (mainly Cd and Zn) partitioned into labile soil fractions. The field data agreed with laboratory pH-static leaching tests performed on FA, which was washed before the experiment to remove soluble salts. This indicates that appropriate laboratory leaching can accurately predict FA behavior in real-life scenarios (e.g., exposure in soil).