Arsenic, Cadmium, and Thallium Content in the Plants Growing in Close Proximity to a Zinc Works - Long-Term Observations

The paper comprises an analysis of the As, Cd, and Tl content in two plant species (Agrostis capillaris and Betula pendula) commonly growing in the vicinity of the Miasteczko Slaskie Zinc Works, in the period of 1998-2018. In 2018, the As, Cd, and Tl content (in mg/kg) in the grasses was 1.10-1.68, 3.14-19.05, and 0.53-5.96, respectively, i.e. lower by 50-70%, compared to the year 1998. The As, Cd, and Tl content (in mg/kg) in birch leaves at the same time point was 0.74-1.54, 4.65-32.44, and 0.80-7.57, respectively, i.e. lower by 10-80%, compared to values found 20 years earlier. In all grass and birch leaf samples collected in 1998 and 2018, the content of the studied elements exceeded the so-called natural levels. The 1998 content of As, Cd, and Tl in the plants was due to the settling of dust containing industrial pollutants and reached 77-96%. After 20 years, the contribution of this source of pollution was considerably lower, reaching 63-79%. The performed analyses demonstrated the following mean contents of the analyzed elements in dust: 243 mg As/kg, 1113 mg Cd/kg, and 44 mg Tl/kg, which confirms the hypothesis on the major role of dust in the current soil and plant pollution. In all the habitats analyzed, a significant decrease of the transfer factor (TF) was found for As and Cd in 2018, compared to 1998. For Tl, a different observation was made. In three out of four analyzed habitats, TF decreased over the two decades studied, whereas in the remaining habitat, TF was higher in 2018 than in 1998 both for the grasses and for the birch leaves. Over the past 20 years, the most polluted area changed as well, from the land located closest to the zinc works, in the direction aligned with the most common winds, to the areas subject to the most intense settling of pollutants carried by the wind from unsecured heaps and industrial waste storage areas.