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.

Outdoor air pollution is considered as the most serious environmental problem for human health, associated with some million deaths worldwide per year. Cities have to cope with the challenges due to poor air quality impacting human health and citizen well-being. According to an analysis in the framework of this study, the annual mean concentrations of tropospheric ozone (O₃) have been increasing by on average 0.16 ppb year⁻¹ in cities across the globe over the time period 1995–2014. Green urban infrastructure can improve air quality by removing O₃. To efficiently reduce O₃ in cities, it is important to define suitable urban forest management, including proper species selection, with focus on the removal ability of O₃ and other air pollutants, biogenic emission rates, allergenic effects and maintenance requirements. This study reanalyzes the literature to i) quantify O₃ removal by urban vegetation categorized into trees/shrubs and green roofs; ii) rank 95 urban plant species based on the ability to maximize air quality and minimize disservices, and iii) provide novel insights on the management of urban green spaces to maximize urban air quality. Trees showed higher O₃ removal capacity (3.4 g m⁻² year⁻¹ on average) than green roofs (2.9 g m⁻² year⁻¹ as average removal rate), with lower installation and maintenance costs (around 10 times). To overcome present gaps and uncertainties, a novel Species-specific Air Quality Index (S-AQI) of suitability to air quality improvement is proposed for tree/shrub species. We recommend city planners to select species with an S-AQI>8, i.e. with high O₃ removal capacity, O₃-tolerant, resistant to pests and diseases, tolerant to drought and non-allergenic (e.g. Acer sp., Carpinus sp., Larix decidua, Prunus sp.). Green roofs can be used to supplement urban trees in improving air quality in cities. Urban vegetation, as a cost-effective and nature-based approach, aids in meeting clean air standards and should be taken into account by policy-makers.

Wood is one of the extensively used goods on the earth due to its large accessibility and usage in a wide range of human life. When woods are exposed to aquatic media, leachates are generated which may affect the quality of water and damage aquatic life into which they are discharged. This research seeks to evaluate the toxicity of linden (Tilia cordata), larch (Larix decidua) from the Czech Republic, cedrela (Cedrela odorata) and emire (Terminalia ivorensis) from Ghana wood leachates to two aquatic organisms (Desmodesmus subspicatus and Lemna minor). In algal and duckweed toxicity tests, these plants were exposed to different concentrations of wood leachate with nutrient medium creating concentration rates, 20, 30, 45, 67, and 100% v/v. High concentration of phenols and heavy metals may have contributed to toxicity. It was observed that the various wood leachates were inhibitory to the growth rate of algae and duckweed with emire exhibiting the highest toxicity with IC₅₀ of 30.04% and 28.58% and larch the lowest toxicity with IC₅₀ of 51.18% and 49.57% in relation to growth rate and chlorophyll respectively, hence indicating confirmed and potential toxicity of the various wood leachates to the aquatic organisms.

Phytoextraction of Cd is a growing biotechnology although we currently know few Cd hyperaccumulators, i.e., plant species able to accumulate at least 0.1 mg Cd g⁻¹ dry weight in aerial organs. Owing their deep root system and high biomass, trees are more and more preferred to herbaceous species for phytoextraction. Assuming that conifers could be relevant models under cold climates, we investigated cadmium tolerance of the hybrid larch Larix × eurolepis Henry (Larix decidua × Larix kaempferi) and the efficiency of this species to store this metal. In vitro grown larches were chosen in order to reduce time of exposure and to more rapidly evaluate their potential efficiency to accumulate Cd. One-month-old plantlets were exposed for 2 and 4 weeks to 250 and 500 μM Cd. Results showed that they tolerated a 4-week exposure to 250 μM Cd, whereas the content of photosynthetic pigment strongly dropped in plantlets growing in the presence of 500 μM Cd. In the presence of 250 μM Cd, shoot growth slightly decreased but photosynthetic pigment and total soluble carbohydrate contents were not modified and no lipid peroxidation was detected. In addition, these plantlets accumulated proline, particularly in shoots (two to three times more than control). In roots, Cd concentration in the intracellular fraction was always higher than in the cell wall fraction contrary to shoots where Cd concentration in the cell wall fraction increased with time and Cd concentration in the medium. In shoots, Cd concentration was lower than in roots with a ratio of 0.2 after 4 weeks of exposure but stayed around 0.2 mg g⁻¹ dry weight, thus a value higher than the threshold requested for Cd hyperaccumulators. Hybrid larch would thus be a relevant candidate for field test of Cd phytoextraction.