If Trees Could Talk - Dendrochemistry, a Promising Method for Understanding Pollution History

Abstract: Heavy metal pollution presents a significant environmental challenge in the Anthropocene era, and understanding pollution history is crucial to address historical pollution and implementing effective mitigation measures. This study stands among a few comprehensive dendrochemical investigations that utilized an extensive dataset and energy dispersive X-ray fluorescence (EDXRF) technique to reconstruct the contamination history of As, Cd, Cu, Ni, Pb, and Zn, with a focus on Cu. Twenty-two samples from European aspen (Populus tremula) and 15 soil samples were collected from an abandoned copper mine in Åtvidabergs municipality, with the aim to evaluate dendrochemistry as a method to investigate contamination history. Soil samples exhibit high variability in contamination levels and pH over short distances, revealing a complex soil pollution picture and a poor correlation between heavy metal concentration in soil and tree-ring concentration. Concurrently, significantly higher tree-ring concentrations and variances are observed in the averaged dendrochemical profile and in individual samples, in the following order: Cu > Ni > As > Zn > Pb > Cd . Correlations with first difference and detrended data show a weak relationship with short-term climatic variations. However, a collective signal of increased dendrochemical anomalies during climatic conditions favoring high water flow is evident, suggesting dendrochemistry as a potential alternative for the reconstruction of past hydrological variations. Dendrochemical methods and European aspen demonstrates potential for recording environmental changes. Nevertheless, lower trace element concentrations in samples from the mines compared to the unpolluted site highlight limitations. For dendrochemistry to become a reliable tool for environmental investigations, future research should refine approaches for grouping climatic variables, understand the effects of different water sources on trace element uptake, and explore various plant parts to obtain a more accurate picture of historical contamination events. It is also essential to examine the high variability within the Populus genus. Addressing these challenges will contribute to establishing dendrochemistry as a valuable tool for understanding historical pollution events and their ecological impacts. Ultimately, this research will shape future mitigation and restoration efforts for ecosystems impacted by anthropogenic activities and pollution.