College of Natural Resources and Environment, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou 510642, China.
Key Laboratory of Arable Land Conservation in South China, Ministry of Agriculture People's Republic of China, Guangzhou 510642, China.
Environ Sci Pollut Res Int. 2020 Sep;27(27):33446-33457. doi: 10.1007/s11356-019-05055-8. Epub 2019 Apr 10.
Soil-exchangeable aluminum (Al) has toxic effects on living organisms in acidic soils. Earthworm presence and activity can alter soil pH, which has a significant influence on Al toxicity. However, the effects of earthworms on soil Al toxicity and fractions are still largely unknown. This laboratory study focused on the effects of three earthworm species (endogeics Pontoscolex corethrurus and Amynthas robustus, anecis Amynthas aspergillum) on soil acidification, Al fraction distribution, and base cation release. Three native earthworm species and a soil (latosolic red soil) collected from a botanical garden in South China were incubated under laboratory conditions. After 40 days of incubation, six Al fractions in soil, namely exchangeable (Al), weakly organically bound (Al), organically bound (Al), amorphous (Al), Al occluded in crystalline iron oxides (Al), and amorphous aluminosilicate and gibbsite (Al) fractions, were extracted using a sequential procedure. Soil pH; organic carbon; total nitrogen; total Al (Al); exchangeable K, Na, Ca, Mg contents; and CEC were determined as well. Compared to control soil, pH values increased by 0.79, 0.41, and 0.57 units in casts in the presence of P. corethrurus, A. robustus, and A. aspergillum, and 0.70, 0.32, and 0.50 units in non-ingested soil, respectively. Compared to control soil, the 61.7%, 30.7%, and 36.1% of Al contents in casts and 68.5%, 25.9%, and 39.0% of Al in non-ingested soil significantly decreased with the addition of P. corethrurus, A. robustus, and A. aspergillum, respectively. Moreover, compared to control soil, the 78.7%, 37.7%, and 40.1% of exchangeable Ca and 12.3%, 24.7%, and 26.8% of exchangeable Mg contents in casts significantly increased with the presence of P. corethrurus, A. robustus, and A. aspergillum, respectively. Soil treated with P. corethrurus had higher soil pH values, exchangeable Ca contents, and lower Al than those with A. robustus and A. aspergillum. Results of principal component analyses showed that P. corethrurus, A. robustus, and A. aspergillum casts and non-ingested soil differ for soil pH, Al fractions, and exchangeable base cations release. These results indicate that earthworms, especially P. corethrurus, can reduce soil Al toxicity, increase soil pH, and affect the release of exchangeable base cations.
土壤交换性铝（Al）对酸性土壤中的生物具有毒性。蚯蚓的存在和活动会改变土壤 pH 值，这对 Al 毒性有重大影响。然而，蚯蚓对土壤 Al 毒性和形态的影响在很大程度上仍不清楚。本实验室研究重点关注三种蚯蚓物种（内栖 Pontoscolex corethrurus 和 Amynthas robustus、表栖 Amynthas aspergillum）对土壤酸化、Al 形态分布和基础阳离子释放的影响。三种本地蚯蚓物种和从中国南方植物园采集的土壤（高沙土）在实验室条件下进行培养。培养 40 天后，使用连续程序提取土壤中六种 Al 形态，即可交换（Al）、弱有机结合（Al）、有机结合（Al）、无定形（Al）、被结晶铁氧化物包裹的 Al（Al）以及无定形的铝硅酸盐和水铝石（Al）形态。同时还测定了土壤 pH 值、有机碳、总氮、总 Al（Al）、可交换 K、Na、Ca、Mg 含量以及 CEC。与对照土壤相比，P. corethrurus、A. robustus 和 A. aspergillum 存在时，其粪便中的 pH 值分别增加了 0.79、0.41 和 0.57 个单位，未被摄入土壤中的 pH 值分别增加了 0.70、0.32 和 0.50 个单位。与对照土壤相比，P. corethrurus、A. robustus 和 A. aspergillum 处理后，粪便中 61.7%、30.7%和 36.1%的 Al 含量以及未被摄入土壤中的 68.5%、25.9%和 39.0%的 Al 含量显著降低。此外，与对照土壤相比，P. corethrurus、A. robustus 和 A. aspergillum 存在时，粪便中 78.7%、37.7%和 40.1%的可交换 Ca 和 12.3%、24.7%和 26.8%的可交换 Mg 含量显著增加。用 P. corethrurus 处理的土壤 pH 值、可交换 Ca 含量和 Al 含量均高于用 A. robustus 和 A. aspergillum 处理的土壤。主成分分析的结果表明，P. corethrurus、A. robustus 和 A. aspergillum 的粪便和未被摄入的土壤在土壤 pH 值、Al 形态和可交换基础阳离子释放方面存在差异。这些结果表明，蚯蚓，特别是 P. corethrurus，可以降低土壤 Al 毒性、提高土壤 pH 值并影响可交换基础阳离子的释放。
