Tissue-specific barium accumulation in five conifer species: a 40-year dendrochemical assessment from a polluted...

Heavy metal pollution is one of the most crucial issues threatening human and environmental wellness today. Barium (Ba), a widely used heavy metal, is one of the most hazardous for the environment and human wellness as all of its compounds are toxic. Therefore, monitoring and reducing Ba pollution is one of the priority study topics. This research aims to identify the most proper plant species for monitoring and mitigating both Ba sources as pollutants and Ba pollution. We examined 40-year-old Cedrus atlantica, Pseudotsuga menziesii, Pinus pinaster, Picea orientalis, and Cupressus arizonica trees grown in Düzce, which is among the five most unclean towns in Europe. Ba concentration was determined in annual tree rings and compared based on tree species, tree tissue, direction, and tree age. The most elevated Ba concentrations were generally obtained in the outer bark and the west direction in all tree species. Results revealed that agricultural activities led to a significant rise in Ba pollution and that all species had limited Ba allocation in their wood. As a result, the change in Ba pollution could be monitored using all of these species. It is concluded that the most proper tree species for sinking Ba pollution is P. orientalis, which accumulated the most Ba in wood.