Reconstructing temporal trends in heavy metal deposition: assessing the value of herbarium moss samples

The use of the herbarium moss archive for investigating past atmospheric deposition of Ni, Cu, Zn, As, Cd and Pb was evaluated. Moss samples from five UK regions collected over 150 years were analysed for 26 elements using ICP-MS. Principal components analysis identified soil as a significant source of Ni and As and atmospheric deposition as the main source of Pb and Cu. Sources of Zn and Cd concentrations were identified to be at least partly atmospheric, but require further investigation. Temporal and spatial trends in metal concentrations in herbarium mosses showed that the highest Pb and Cu levels are found in Northern England in the late 19th century. Metal concentrations in herbarium moss samples were consistently higher than those in mosses collected from the field in 2000. Herbarium moss samples are concluded to be a useful resource to contribute to reconstructing trends in Pb and Cu deposition, but not, without further analysis, for Cd, Zn, As and Ni.