Department of Agroenvironmental Chemistry and Plant Nutrition, Czech University of Life Sciences Prague (CULS), Kamýcká 129, 165 00, Prague, Czech Republic.
Department of Forest and Soil Sciences, University of Natural Resources and Life Sciences, Vienna (BOKU), Konrad Lorenz Straße 24, 3430, Tulln, Austria.
Environ Sci Pollut Res Int. 2019 Jul;26(20):20866-20878. doi: 10.1007/s11356-019-05430-5. Epub 2019 May 20.
The establishment of phytoextraction crops on highly contaminated soils can be limited by metal toxicity. A recent proposal has suggested establishing support crops during the critical initial phase by metal immobilization through soil amendments followed by subsequent mobilization using elemental sulphur to enhance phytoextraction efficiency. This 'combined phytoremediation' approach is tested for the first time in a pot experiment with a highly contaminated soil. During a 14-week period, relatively metal-tolerant maize was grown in a greenhouse under immobilization (before sulphur (S) application) and mobilization (after S application) conditions with soil containing Cd, Pb and Zn contaminants. Apart from the control (C) sample, the soil was amended with activated carbon (AC), lignite (Lig) or vermicompost (VC) all in two different doses (dose 145 g additive kg soil and dose 290 g additive kg soil). Elemental S was added as a mobilization agent in these samples after 9 weeks. Biomass production, nutrient and metal bioavailability in the soil were determined, along with their uptake by plants and the resulting remediation factors. Before S application, Cd and Zn mobility was reduced in all the AC, Lig and VC treatments, while Pb mobility was increased only in the Lig1 and VC1 treatments. Upon sulphur application, Fe, Mn, Cd, Pb and Zn mobility was not significantly affected in the C, AC and VC treatments, nor total Cd, Pb and Zn contents in maize shoots. Increased sulphate, Mn, Cd, Pb and Zn mobilities in soil together with related higher total S, Mn, Pb and Zn contents in shoots were observed in investigated treatments in the last sampling period. The highest biomass production and the lowest metal toxicity were seen in the VC treatments. These results were associated with effective metal immobilization and showed the trend of steady release of some nutrients. The highest remediation factors and total elemental content in maize shoots were recorded in the VC treatments. This increased phytoremediation efficiency by 400% for Cd and by 100% for Zn compared to the control. Considering the extreme metal load of the soil, it might be interesting to use highly metal-tolerant plants in future research. Future investigations could also explore the effect of carbonaceous additives on S oxidation, focusing on the specific microorganisms and redox reactions in the soil. In addition, the homogeneous distribution of the S rate in the soil should be considered, as well as longer observation times.
在高度污染的土壤上建立植物提取作物可能会受到金属毒性的限制。最近的一项建议建议，通过土壤改良在关键的初始阶段建立支持作物，通过添加元素硫来随后增强植物提取效率，从而实现金属固定化。这种“联合修复”方法首次在一个高度污染的土壤的盆栽实验中进行了测试。在 14 周的时间内，相对耐金属的玉米在温室中生长，在含有 Cd、Pb 和 Zn 污染物的土壤中进行固定化（在施用硫之前）和活化（在施用硫之后）条件下。除了对照（C）样品外，土壤中还添加了活性炭（AC）、褐煤（Lig）或蚯蚓粪（VC），剂量分别为 145 g 添加剂 kg 土壤和 290 g 添加剂 kg 土壤。在 9 周后，这些样品中添加了元素硫作为活化剂。测定了生物量产量、土壤中的养分和金属生物有效性，以及它们被植物吸收的情况，以及由此产生的修复因子。在添加硫之前，所有 AC、Lig 和 VC 处理都降低了 Cd 和 Zn 的迁移性，而只有 Lig1 和 VC1 处理增加了 Pb 的迁移性。添加硫后，C、AC 和 VC 处理中土壤中 Fe、Mn、Cd、Pb 和 Zn 的迁移性以及玉米地上部的总 Cd、Pb 和 Zn 含量均无显著变化。在最后一次采样期，在调查的处理中观察到土壤中硫酸盐、Mn、Cd、Pb 和 Zn 迁移性增加，以及地上部总 S、Mn、Pb 和 Zn 含量增加。在 VC 处理中观察到最高的生物量产量和最低的金属毒性。这些结果与有效的金属固定化有关，并显示出一些养分稳定释放的趋势。在 VC 处理中，玉米地上部的修复因子和总元素含量最高。与对照相比，Cd 的植物修复效率提高了 400%，Zn 的提高了 100%。考虑到土壤的极端金属负荷，在未来的研究中使用高度耐金属的植物可能会很有趣。未来的研究还可以探索碳素添加剂对 S 氧化的影响，重点关注土壤中的特定微生物和氧化还原反应。此外，还应考虑 S 率在土壤中的均匀分布以及更长的观测时间。
