Interactions of cadmium and zinc impact their toxicity to the earthworm Aporrectodea caliginosa

Abstract

Individual and binary mixture effects of Cd and Zn on mortality of the earthworm Aporrectodea caliginosa were investigated in one soil type. Mutual, systemic interactions of Cd and Zn were assessed over a broad range of concentration combinations. Exposures were expressed as measured total concentrations in soil, porewater concentrations, and CaCl(2)-extractable concentrations. The Cd-Zn and Zn-Cd interactions in soil were estimated by comparing partition coefficients (K(d)) of one metal in the presence and absence of the second metal. Simple patterns of mixture toxicity (additive, antagonistic, or synergistic) were evaluated by the toxic unit approach. The more complex patterns (dose ratio dependent or dose level dependent) were quantified by the MIXTOX model. The partitioning of Cd and Zn between soil and pore water was affected neither by their concentration nor presence of the other metal, and metal partitioning remained linear at all exposure levels tested. The effect of the Cd and Zn mixtures on mortality of A. caliginosa was mainly antagonistic, and the magnitude of antagonism (1.1- 2.7 toxic units) was dependent upon both the relative concentrations of Cd and Zn and the concentration magnitudes. Interactions of both metals occurred at the organism level and were manifested in terms of effects (28-d median lethal concentrations). The present study highlights the importance of identifying the relative influence of various interactions from external exposure to internal assimilation in evaluating mixture toxicity.

Interaction between nickel and cobalt toxicity in Enchytraeus crypticus is due to competitive uptake

“…It should be noted that both the concentration addition model and the independent action model in their standard form do not consider mixture interactions in estimating mixture toxicity. However, mixture components may interact at various levels: 1) exposure level, 2) uptake level, and 3) target level . Identifying interactions at relevant levels will therefore help to explain differences in interaction patterns that occur between different exposure media and between different test organisms.…”

Earthworms and Soil Pollutants

“…The binary mixture effects of cadmium and zinc on the mortality of Aporrectodea caliginosa were also investigated by Qiu et al . [14]. They reported that the effects of the cadmium and zinc mixtures on the mortality of Aporrectodea caliginosa were mainly antagonistic, and the magnitude of the antagonism was dependent upon both the relative concentrations of cadmium and zinc and their concentration magnitudes.…”

Delineating the dynamic uptake and toxicity of Ni and Co mixtures in Enchytraeus crypticus using a WHAM-FTOX approach

“…Traditional ecotoxicological studies were often performed for a certain endpoint after a fixed exposure time (Lock and Janssen, 2002;Qiu et al, 2011), while toxicity may vary with time. For instance, Utgikar et al (2004) and Baas et al (2007), investigating the mixture toxicity of Zn and Cu to Vibrio fischeri and of Cu and Cd to Folsomia candida, respectively, found that the toxicity of these metal mixtures increased with exposure time.…”