Metal/metalloid (As, Cd and Zn) bioaccumulation in the earthworm Eisenia andrei under different scenarios of climate change

Abstract

This study aimed at assessing the effects of global warming (increasing air temperature and decreasing soil moisture content) on the bioaccumulation kinetics of As, Cd and Zn in the earthworm Eisenia andrei in two polluted soils (mine tailing and watercourse soil). Earthworms were exposed for up to 21 d under four climate conditions: 20 °C + 50% soil water holding capacity (WHC) (standard conditions), 20 °C + 30% WHC, 25 °C + 50% WHC and 25 °C + 30% WHC. Porewater metal/metalloid availability did not change in the mine tailing soil after the incubation period under the different climate conditions tested. However, in the watercourse soil, porewater Cd concentrations decreased from ∼63 to ∼32–41 μg L−1 after 21 d and Zn concentrations from ∼3761 to ∼1613–2170 μg L−1, especially at 20 °C and 50% WHC. In both soils, As and Zn showed similar bioaccumulation patterns in the earthworms, without major differences among climate conditions. Earthworm concentrations peaked after 1–3 d of exposure (in μg g−1 dry weight: As∼32.5–108, Zn∼704–1172) and then remained constant (typical pattern of essential elements even for As). For Cd the bioaccumulation pattern changed when changing the climate conditions. Under standard conditions, earthworm Cd concentrations increased to ∼12.6–18.5 μg g−1 dry weight without reaching equilibrium (typical pattern of non-essential elements). However when increasing temperature and/or decreasing soil moisture content the bioaccumulation pattern changed towards that more typical of essential elements due to increased Cd elimination rates (from ∼0.11 to ∼0.24–1.27 d−1 in the mine tailing soil, from ∼0.07 to ∼0.11–0.35 d−1 in the watercourse soil) and faster achievement of a steady state. This study shows that metal/metalloid bioaccumulation pattern in earthworms may change dependent on climate conditions.