“…Napa et al (2017) analyze heavy metals that have been accumulated in the soil organic horizon of coniferous forests during the peak of oilshale usage period from 1960 to 1990 in the Baltic region. The study demonstrated that heavy metal concentrations in the soil organic horizon and fine roots were strongly correlated, and thus, fine roots and their associated mycelia in the soil retain heavy metals in forest biogeochemical cycle for unexpectedly long periods.…”