Biocidal products represent mixtures that might be released into the environment at application and continuously during service life. Concentration addition (CA) has been proposed as default model to calculate theoretical mixture toxicity. However, the suitability of CA for chronic toxicity towards soil organisms has so far rarely been evaluated and therefore needs further experimental evidence. The present study investigated the toxicity of a wood preservative product and the individual active substances (tebuconazole and IPBC) therein with the aim to evaluate the compliance with the CA prediction for the product. Folsomia candida was selected as test organism for this purpose using the endpoints reproduction and avoidance behaviour. Both endpoints were increasingly impacted by increasing concentrations of the wood preservative product as well as its active substances tested individually. The chronic effects of the product could be predicted by CA with less than 4-fold deviation, while the assessment for avoidance behaviour indicated a strong underestimation. This underestimation could not be attributed to the one known formulation additive, an organic solvent. Overall, the present study provides some more evidence that CA could be applied as default model for standard endpoints of soil organisms, but warns against using CA for behavioural responses.

杀菌产品代表混合物，这些混合物在使用时可能会释放到环境中，并且在使用寿命期间会不断释放。浓度添加（CA）已被提议作为计算理论混合物毒性的默认模型。但是，到目前为止，CA对土壤微生物的慢性毒性的适用性很少得到评估，因此需要进一步的实验证据。本研究调查了木材防腐产品和其中的单个活性物质（戊唑醇和IPBC）的毒性，目的是评估该产品对CA预测的符合性。念珠菌为此，使用终点繁殖和回避行为将其作为测试有机体。木材防腐产品及其活性物质的浓度不断增加，这两个端点受到的影响越来越大。CA可以预测产品的慢性影响，偏差小于4倍，而对规避行为的评估表明，该行为的严重低估了。这种低估不能归因于一种已知的配方添加剂有机溶剂。总体而言，本研究提供了更多证据，证明CA可以用作土壤生物标准终点的默认模型，但警告不要将CA用于行为反应。