Humus samples as an indicator of long-term anthropogenic input - A case study from southern Finland

According to the results presented here, the humus element concentrations are more strongly affected by atmospheric inputs than by the lithogenic contribution, which is opposite to the case for the topsoil samples. The topsoil element distribution maps clearly show a strong relationship with the bedrock geology, such as the relationship of the Ni distribution with the Ni-Co-Cu metallogenic area of the Tampere Region, while the element distributions in humus show a strong correlation with the anthropogenic impact of known deposition from local pollution sources. No long-range transport was clearly identified, but point sources, such as the Pori-Harjavalta smelters, and more densely populated and industrialized areas, such as the city of Tampere and the coastline from the city of Porvoo to the capital region of Helsinki, cause locally high anomalies in humus concentrations, even many years after the reduction of industrial inputs. Further humus samples should be collected with a sufficient sampling density close to city centers and industrialized areas in order to improve knowledge of element concentrations in humus and anthropogenic inputs to the topmost layer of the ground surface, as well as potential risks to the environment and human health.