The effect of counterion and percolation on the toxicity of lead for the springtail Folsomia candida in soil

Abstract

In standard soil toxicity tests, heavy metals are amended as water-soluble salts. The role of the counterion in metal salt toxicity is scarcely looked into. In this study, we assessed the contribution of nitrate and chloride to the toxicity of lead to Folsomia candida in a natural standard soil. Both lead salts were tested according the standard test protocol as well as after percolation of the soil with deionized water. Lead nitrate was more toxic than lead chloride for survival as well as reproduction. Percolation proved to be an effective method to remove counterions from the soil. Survival of F. candida increased for both metal salts when percolation was included. Percolation reduced the reproduction toxicity of lead, the effect of which was largest for the nitrate salt. In percolated treatments, the nitrate and chloride lead salts did not differ in toxicity. It is concluded that counterions contribute to metal toxicity and that nitrate is more toxic to F. candida than chloride.

Assessment of the bioavailability and toxicity of lead polluted soils using a combination of chemical approaches and bioassays with the collembolan Folsomia candida

“…This was also shown by Bongers et al [25]. At total soil concentrations of 406-49,200 mg/kg dw, a fairly constant bioaccumulation factor (BAF) for F. candida of 0.04-0.06 was calculated [14], also supporting the linear increase in body concentrations with increasing exposure level.…”

“…Joosse and Verhoef [33] also noticed no significant effect of Pb on the growth of the collembolan Orchesella cincta. Since total Pb concentrations in F1 and F3 soils were very close to the LC50 value (2900 mg/kg dw) reported for collembolans [25], mortality in these most polluted forest soils might also be related to Pb contamination.…”

“…A Pb concentration of 1312 mg/kg dw may cause extinction of populations of F. candida [35]. Bongers et al [25] found an EC50 reproduction for F. candida of 1900 mg Pb/kg dw. Nursita et al [32] were not able to determine an EC50 reproduction for F. candida at soil Pb concentrations up to 3000 mg/kg dw.…”

Modelling the effects of copper on soil organisms and processes using the free ion approach: Towards a multi-species toxicity model

“…Clearly these 424 side effects of dosing with a soluble metal salt may be confounding a rigorous 425 analysis of protective effects; future studies need to consider how such side effects 426 might be minimised, for example by leaching the soil following dosing and prior to 427 toxicity testing (e.g. Bongers et al, 2004;Oorts et al, 2007;Smolders et al, 2009;Li 428 et al, 2010). 429…”

Lead toxicity thresholds in 17 Chinese soils based on substrate-induced nitrification assay

“…Aging processes and loss of excess salts by leaching may contribute much to this discrepancy (Oorts et al, 2006a). Therefore, leaching after metal addition has been proposed as an agreed approach to reduce the chemical artifacts of the spiking procedure (e.g., salt effect, increased metal solubility) that can decrease the ecological relevance of soil toxicity assays (Schwertfeger, 2011;Smolders et al, 2009;Oorts et al, 2006aOorts et al, , 2007Bongers et al, 2004;Stevens et al, 2003). The effects of leaching on Pb ECx values in soils require further study on a larger scale before leaching is used as a standard protocol in soil toxicity assays.…”