Abstract Large amounts of chemicals are released into soil environments due to human activities, thereby harming organisms and their habitats. Earthworms are important bioindicators for chemical risk assessments of soil ecosystems, but the question remains of how they respond to different patterns of pollution. Laboratory experiments in soil mesocosms were carried out to observe changes in the burrowing behaviour of two earthworm species (Aporrectodea caliginosa and Lumbricus terrestris) with regard to different spatial distributions of benzo(a)pyrene, cadmium and copper, using X-ray computed microtomography (μCT). This is, to our knowledge, the first contribution of μCT to study earthworm behaviour in heterogeneously multi-polluted soils. Columns (14 × 30 cm) were filled with a silt loam soil and packed to represent two scenarios of heterogeneous pollution: a) ‘binary’, containing polluted soil in the low half part and unpolluted soil on top; and b) ‘patches’, containing small portions of polluted soil randomly placed into an unpolluted matrix. Earthworms were introduced individually in the columns and left in climatic chambers for 7 weeks. μCT images revealed that earthworms avoided the polluted zones differently (e.g. A. caliginosa>L. terrestris, ‘binary’ configuration). Individuals of L. terrestris that entered polluted areas showed a lower burrowing activity (volume and length of the burrow system) than those that did not enter. The presence of ‘patches’ of polluted soil did not cause a reduction of the burrowing activity such as that found in the ‘binary’ columns, although earthworms showed avoidance. Our results indicate that pollutants had a greater effect on earthworms’ burrowing behaviour in the presence of larger portions of contaminated soil compared with small random ones. The more evident avoidance behaviour of A. caliginosa pinpoints its usefulness in toxicity bioassays based on avoidance patterns, but questions its use in assays based on bioaccumulation of pollutants in tissues, for which L. terrestris may perform better.

中文翻译：

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使用 X 射线显微断层扫描表征蚯蚓在异质污染土壤中的掘穴行为

摘要 由于人类活动，大量化学物质被释放到土壤环境中，从而危害生物及其栖息地。蚯蚓是土壤生态系统化学风险评估的重要生物指标，但问题仍然是它们如何应对不同的污染模式。使用 X 射线计算机显微断层扫描技术，在土壤中宇宙中进行了实验室实验，以观察两种蚯蚓（Aporrectodea caliginosa 和 Lumbricus terrestris）在苯并（a）芘、镉和铜的不同空间分布方面的穴居行为变化。 μCT）。据我们所知，这是 μCT 对研究非均质多污染土壤中蚯蚓行为的第一个贡献。柱子（14 × 30 cm）用粉砂壤土填充并填充以代表两种异质污染情况：a）“二元”，下半部分包含污染土壤，顶部包含未污染土壤；b) “补丁”，包含随机放置在未污染基质中的小部分污染土壤。蚯蚓被单独引入柱中并留在气候室中7周。μCT 图像显示蚯蚓以不同方式避开污染区（例如，A. caliginosa> L. terrestris，“二元”配置）。进入污染区域的 L. terrestris 个体比未进入的个体表现出较低的穴居活动（穴居系统的体积和长度）。受污染土壤“斑块”的存在并没有导致挖洞活动的减少，例如在“二元”柱中发现的挖洞活动，虽然蚯蚓表现出回避。我们的结果表明，与小的随机土壤相比，污染物对蚯蚓在较大部分受污染土壤中的挖洞行为有更大的影响。A. caliginosa 更明显的回避行为指出了它在基于回避模式的毒性生物测定中的有用性，但质疑它在基于组织中污染物的生物积累的测定中的使用，在这方面 L. terrestris 可能表现更好。