# Historical copper mining contamination assessed using dendrochemical analysis in Southeastern Sweden

## TL;DR

This study uses tree rings to track historical copper contamination near an abandoned mine in Sweden, showing how environmental factors affect metal uptake.

## Contribution

The study demonstrates the potential of dendrochemical analysis for reconstructing historical heavy metal pollution trends.

## Key findings

- Tree rings showed increased accumulation of copper, nickel, and zinc near the abandoned copper mine.
- Temperature had a more consistent influence on metal uptake than precipitation.
- Dendrochemical methods revealed contamination patterns not captured by traditional soil sampling.

## Abstract

Heavy metal pollution from untreated or poorly managed mining waste is a major environmental concern, leading to the leaching of contaminants into surrounding ecosystems. Traditional monitoring methods are costly and limited in their ability to reconstruct historical contamination trends. Dendrochemical methods offer a promising alternative for assessing long-term pollution dynamics. This study investigates temporal patterns of copper (Cu), nickel (Ni), and zinc (Zn) accumulation in tree rings from 22 European aspens (Populus tremula) growing near an abandoned copper mining field in southeastern Sweden. Tree rings were analyzed using energy-dispersive X-ray fluorescence (ED-XRF), while corresponding soil samples were examined for heavy metal concentrations and pH. Considerable heterogeneity in Cu and pH was observed, with elevated Cu levels across the site. Although no significant correlations were found between soil and tree-ring metal concentrations, increased accumulation of Cu, Ni, and Zn was detected in the trees. Temperature showed a more consistent influence on metal uptake than precipitation. Anomalous uptake increased under warmer and wetter conditions but was absent during severe drought. This study emphasizes the potential of dendrochemical methods for monitoring historical pollution. It highlights the need to refine sampling strategies to better account for localized soil and climatic factors, thereby improving the reliability of dendrochemical methods in assessing pollution trends.