Assessing Tree Species for Monitoring and Mitigating Strontium Pollution in Urban Environments

Abstract

Air pollution, particularly heavy metal contamination, has emerged as a critical global issue, posing significant human and environmental health risks over the past century. Strontium (Sr), a highly hazardous heavy metal, even at small concentrations, is classified as a priority contaminant by international organizations due to its potential adverse effects. This study aimed to specify the most appropriate plant species for observing and mitigating Sr contamination. Samples were collected from Pseudotsuga menziesii (Douglas fir), Tilia tomentosa (Silver linden), and Fraxinus excelsior (European ash or common ash) growing in Düzce, Türkiye, one of the five most unclean towns in European countries according to the 2021 World Air Pollution Report. Variations in Sr concentrations over the past 60 years were analyzed based on tree species, tree organs, direction, and age group. The findings reveal that these species are unsuitable as biomonitors for tracking Sr pollution trends. However, all three species demonstrated the ability to accumulate significant levels of Sr in their wood, making them viable candidates for phytoremediation efforts. Among the species studied, European ash trees were the most effective in reducing Sr contamination, with the highest Sr accumulation in wood (11.36 mg/kg).