Acute toxicity test for terrestrial hazard assessment with exposure of Folsomia candida to pesticides in an aqueous medium

The present study sought to quantify the components of a biotic ligand model (BLM) for the effects of Cd on Folsomia candida (Collembola). Assuming that soil porewater is the main route of exposure and to exclude the effects of soil particles on metal availability, animals were exposed for 7 d to different Cd concentrations between 0.1 mM and 100 mM in simplified soil solutions at different Ca concentrations (0.2 mM, 0.8 mM, 3.2 mM, and 12.8 mM) or at different pH (5.0, 6.0, and 7.0). Higher Ca concentrations decreased the toxicity of Cd (adult survival) in test solutions, whereas toxicity was slightly lower at pH 7 and 6 than at pH 5, suggesting a mitigating effect of Ca and to a lesser extent pH on Cd toxicity to F. candida. Internal Cd concentrations in the animals increased with increasing exposure level but were significantly reduced by increasing Ca concentrations and were not significantly affected by pH. By using Langmuir isotherms, binding constants for Cd, Ca, and protons and the fraction of binding sites occupied by Cd were calculated and used to predict effects of Cd on survival. Predicted toxicity showed a good agreement with measured responses when Ca and pH were used as separate factors or combined together. The present study shows indications of protective effects of Ca but less of protons on the toxicity and uptake of Cd in F. candida on exposure to simplified soil solutions, which can be described using the principles of a biotic ligand model.

Section: Introductionmentioning

confidence: 99%

Influence of Ca and pH on the uptake and effects of Cd in Folsomia candida exposed to simplified soil solutions

Ardestani

Ortiz²,

Gestel³

2013

“…This shows the applicability of aqueous solutions for exposing this organism as described by Houx et al [16] and Ronday and Houx [19]. In these studies, it was shown that F. candida can survive for at least 8 d in saline water (0.5 g synthetic sea salt and 0.3 g KH 2 PO 4 per liter tap water at pH 5.7) and can move about on the water surface [16,19].…”

Section: Animal Performance and Solution Compositionmentioning

confidence: 89%

Toxicodynamics of copper and cadmium inFolsomia candidaexposed to simulated soil solutions

Ardestani¹,

Gestel²

2013

To improve our understanding of metal bioavailability to soil-living invertebrates, the effect of porewater composition on the toxicodynamics of copper and cadmium in Folsomia candida (Collembola) was investigated. Assuming that porewater is the main exposure route, F. candida was exposed to simulated soil solutions of different composition. Toxicity of copper was slightly lower in a calcium-only solution than in a multication solution. With increasing copper concentrations from 0.005 mM to 1.37 mM, internal copper concentrations similarly increased in both exposure solutions, suggesting that a single cation nutrient solution is suitable for testing F. candida. In the second experiment, animals were exposed for 7 d to copper and cadmium in simplified soil solutions with different calcium (0.2 mM, 0.8 mM, 3.2 mM, 12.8 mM) and pH (5.0, 6.0, 7.0) levels. The median lethal concentration (LC50) values decreased with time in both the calcium and pH series. A hormetic-type effect was observed for copper in the second test, as well as in the calcium-only solution in the first experiment. Because of stronger hormesis, LC50s for copper were higher at lower calcium concentrations. For cadmium, LC50 values were higher at higher calcium concentrations, suggesting competition of calcium with the free cadmium ion. Toxicity of cadmium increased with decreasing pH, while copper was more toxic at intermediate pH. The results show that a toxicodynamics approach can help to improve the interpretation of metal toxicity to soil invertebrates, taking into account soil solution properties.

“…The springtail Folsomia candida (Willem) was selected as the test organism. This species has been found to be sensitive to a range of pesticides [11]. Folsomia candida was bred in our laboratory at 23ЊC on a mixture of the three natural soils used in the test.…”

Section: Test Organismmentioning

confidence: 99%

Persistence and toxicological effects of pesticides in topsoil: Use of the equilibrium partitioning theory

Ronday

Kammen-Polman

Dekker

et al. 1997

Three parameters for indicating toxicologic risk of pesticides to soil organisms were compared: the traditional total content parameter, the equilibrium partitioning approach, and the pore‐water concentration parameter. The relevance of each parameter was tested using different soil types and prolonged chemical–soil contact time by relating the results to bioavailability as measured in toxicity tests. The pesticide concentration measured in the soil pore water could be shown to correspond strongly with toxicologic effects on the soil organism Folsomia candida, irrespective of soil type and chemical–soil contact time. This relationship is predicted by the equilibrium partitioning theory and so this aspect of the theory could be validated in this study for pesticides in soil. However, the theory's assumption of equilibrium (which implies that the bioavailable fraction of the chemical is constant with time and can be calculated using one particular soil to pore‐water partition coefficient) could not be justified in this study. Although organic matter normalization reduced soil‐to‐soil differences, it did not account for the time‐related decrease in bioavailability that was found in two of the four soil–chemical combinations investigated. As a consequence, pore‐water concentrations calculated from chemical content measurements in soil and a partition coefficient obtained in short‐term laboratory experiments may not be a good estimate for sorption or toxicologic effects on a longer term. The suggestion is made to measure the concentration of chemical in pore water directly and to use water‐only toxicity values as a basis for soil quality criteria.