Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, SE-39231 Kalmar, Sweden.
Research and Development, Novia University of Applied Sciences, FI-65200 Vaasa, Finland.
Sci Total Environ. 2022 Mar 20;813:151864. doi: 10.1016/j.scitotenv.2021.151864. Epub 2021 Nov 23.
Sediments along the Baltic Sea coast can contain considerable amounts of metal sulfides that if dredged and the spoils deposited such that they are exposed to air, can release high concentrations of acid and toxic metals into recipient water bodies. Two river estuaries in western Finland were dredged from 2013 to 2018 and the dredge spoils were deposited on land previously covered with agricultural limestone to buffer the pH and mitigate acid and metal release. In this study, the geochemistry and 16S rRNA gene amplicon based bacterial communities were investigated over time to explore whether the application of lime prevented a conversion of the dredge spoils into acid producing and metal releasing soil. The pH of the dredge spoils decreased with time indicating metal sulfide oxidation and resulted in elevated sulfate concentrations along with a concomitant release of metals. However, calculations indicated only approximately 5% of the added lime had been dissolved. The bacterial communities decreased in diversity with the lowering of the pH as taxa most similar to extremely acidophilic sulfur, and in some cases iron, oxidizing Acidithiobacillus species became the dominant characterized genus in the deposited dredge spoils as the oxidation front moved deeper. In addition, other taxa characterized as involved in oxidation of iron or sulfur were identified including Gallionella, Sulfuricurvum, and Sulfurimonas. These data suggest there was a rapid conversion of the dredge spoils to severely acidic soil similar to actual acid sulfate soil and that the lime placed on the land prior to deposition of the spoils, and later ploughed into the dry dredge spoils, was insufficient to halt this process. Hence, future dredging and deposition of dredge spoils containing metal sulfides should not only take into account the amount of lime used for buffering but also its grain size and mixing into the soil.
波罗的海沿岸的沉积物可能含有大量的金属硫化物，如果进行疏浚，并将疏浚物倾倒在暴露于空气中的地方，可能会将高浓度的酸和有毒金属释放到受纳水体中。芬兰西部的两个河口在 2013 年至 2018 年期间进行了疏浚，疏浚物被倾倒在以前覆盖有农业石灰的土地上，以缓冲 pH 值并减轻酸和金属的释放。在这项研究中，随着时间的推移，研究了地球化学和基于 16S rRNA 基因扩增子的细菌群落，以探讨石灰的应用是否阻止了疏浚物转化为产酸和释放金属的土壤。随着时间的推移，疏浚物的 pH 值降低，表明金属硫化物氧化，导致硫酸盐浓度升高，并伴随着金属的释放。然而，计算表明，只有约 5%的添加石灰已经溶解。随着 pH 值的降低，细菌群落的多样性减少，与极度嗜酸硫和某些情况下铁氧化的 Acidithiobacillus 物种最相似的分类群成为沉积物中占主导地位的特征属，因为氧化前沿向深处移动。此外，还鉴定出其他与铁或硫氧化有关的分类群，包括Gallionella、Sulfuricurvum 和 Sulfurimonas。这些数据表明，疏浚物迅速转化为类似于实际酸性硫酸盐土壤的强酸性土壤，而在倾倒疏浚物之前放置在土地上的石灰，以及后来在干燥的疏浚物中翻耕，不足以阻止这一过程。因此，未来的疏浚和金属硫化物疏浚物的倾倒不仅应考虑用于缓冲的石灰量，还应考虑其粒度和与土壤的混合。
