INTERACTION OF Cd AND Zn TOXICITY FOR FOLSOMIA CANDIDA WILLEM (COLLEMBOLA: ISOTOMIDAE) IN RELATION TO BIOAVAILABILITY IN SOIL

Abstract

Abstract-The use of toxicity tests in which each chemical is tested separately is inadequate for assessing the potential risk of complex mixtures of chemicals for soil ecosystems. In the present study, the effects of Cd and Zn, alone or in combination, on the survival, growth, and reproduction of the collembolan Folsomia candida were determined after 2, 4, and 6 weeks of exposure in an artificial soil. The water solubility of Cd in the soil was significantly increased by the presence of Zn, whereas Cd did not affect the water solubility of Zn. In spite of this, uptake of Cd or Zn in the animals was not affected by the presence of the other metal, suggesting that water solubility does not determine the uptake of these metals in F. candida. For both Cd and Zn, reproduction was the most sensitive parameter, with 50% effective concentration (EC50) values of 51 and 683 g/g dry soil, respectively, after 6 weeks. These values corresponded with internal concentrations of 44 g Cd/g and 97 g Zn/g dry body weight, respectively, while corresponding water-soluble EC50s were 0.13 g Cd/g and 14 g Zn/g dry soil, respectively. Although a proper comparison of the effects of mixtures of the metals with the effects of the individual metals was sometimes hampered by the nonsimilarity of dose-response relationships, it may be concluded that the effects of the mixture of Cd and Zn on the growth of F. candida are antagonistic (EC50 significantly greater than 1.0 toxic unit), while the effects on reproduction are additive (EC50 ϭ 1.0 toxic unit). Similar conclusions could be drawn for EC50s expressed on the basis of total and water-soluble soil concentrations as well as on the basis of internal concentrations in the animals. Analysis of the combined effects of Cd and Zn at the 10% effective concentration level did not change these conclusions.

Ecotoxicity of cadmium in a soil collembolan-predatory mite food chain: Can we use the 15N labeled litter addition method to assess soil functional change?

“…This result is in good agreement with published results (EC50 of F. candida reproduction 28e780 mg Cd kg À1 ) using the single species test (Crommentuijn et al, 1997;van Gestel and Mol, 2003;Bur et al, 2010;. The above-mentioned data show that EC50 values of F. candida reproduction based on total Cd vary widely in different studies and differences in soil properties may be an important contributory factor.…”

Life cycle responses of the midge Chironomus riparius to polycyclic aromatic compound exposure

“…For the acridone data the logistic fit was not possible, and a Weibull curve was used instead. To determine at which PAC concentrations emergence was significantly delayed, EMt 50 values for the different test concentrations were compared to the solvent control value using generalised likelihood ratio tests (Van Gestel and Hensbergen, 1997). For phenanthridone, the comparison was done using the lowest concentration.…”

“…For all compounds except anthracene, concentrations at which effects on emergence time of the tested compounds appeared were more than one order of magnitude higher than total SPAH concentrations measured in lake sediments from the USA (Van Metre and Mahler, 2005). Concentrations of azaarenes and other heterocyclic PACs are nearly never monitored in the field, but estimated to be up to 10% of the total PAC concentration in the sediment (Neilson, 1998).…”

“…Smaller amounts of PACs are generated in natural processes, like volcanism and forest fires (Neilson, 1998). Because of their hydrophobicity, PACs tend to accumulate in sediments and soils, which act not only as a sink, but also as a source of PACs for benthic organisms (Wilcke, 2000;Van Metre and Mahler, 2005). In sediment cores from 38 urban and reference lakes across the United States, total sediment SPAH concentrations (SPAH ¼ sum of 13 homocyclic PACs used for the consensus-based sediment quality guidelines in the USA) ranged from 0.5 to 10 mg/kg (Van Metre and Mahler, 2005).…”

“…Because of their hydrophobicity, PACs tend to accumulate in sediments and soils, which act not only as a sink, but also as a source of PACs for benthic organisms (Wilcke, 2000;Van Metre and Mahler, 2005). In sediment cores from 38 urban and reference lakes across the United States, total sediment SPAH concentrations (SPAH ¼ sum of 13 homocyclic PACs used for the consensus-based sediment quality guidelines in the USA) ranged from 0.5 to 10 mg/kg (Van Metre and Mahler, 2005).Populations of benthic invertebrates are exposed to a variety of PACs in the sediment, but little is known about their chronic effects, since research has mainly focused on acute exposure (Bleeker et al, 1998; Neilson, 1998;Wiegman et al, 2001). During such acute high-dose exposures PACs act mainly by narcosis (Neilson, 1998) …”