Human health and ecological risk assessment of heavy metals in topsoil of different peatland use types

Abstract

Peatlands, known for their ability to retain and immobilize heavy metals due to unique waterlogged conditions and organic matter, face challenges when subjected to disturbances such as land use changes. These disruptions alter the organic matter, redox potential, and pH of the peatsoil, potentially influencing the migration, mobilization, and increased availability of stored heavy metals. Peatsoil samples from various peatland use types (improved and semi-natural grassland, forest, industrial cutaway bog) were collected to assess the human health and ecological risk associated with heavy metals (Cd, Cu, Hg, Pb, and Zn) in Co-Offaly, Ireland. Results reveal variations in heavy metal concentrations across peatland use types, with Cd, Hg, and Pb in improved and semi-natural grassland peatsoils exceeding the World Health Organization (WHO) permissible safety limits. Contamination factors (CF) were higher in improved grassland, especially for Cd and Pb, exceeding one. Hakanson potential ecological risk assessment indicates acceptable overall risk levels, though variations exist between improved grassland, unimproved grassland, forest, and industrial cutaway bog. Combined exposure routes (dermal, ingestion and inhalation routes) to all heavy metals do not exceed safe exposure levels (indicating low non-carcinogenic risks. However, the cancer risk (CR) exceeds acceptable thresholds across all use types, with higher CR in improved grassland, especially for children. Overall, the findings emphasize the need for careful consideration of heavy metal risks associated with land use changes in peatlands, particularly in the improved grassland areas.