Departamento de Ciencia y Tecnología Agraria, E.T.S. de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, Cartagena, 30203, Murcia, Spain.
Department of Biology & CESAM, Campus Universitário de Santiago, University of Aveiro, 3810-193, Aveiro, Portugal.
J Environ Manage. 2018 Oct 1;223:554-565. doi: 10.1016/j.jenvman.2018.06.055. Epub 2018 Jun 28.
This study aimed to assess the effectiveness of biochar from sewage sludge -BSS- and from pruning trees -BPT- (addition dose of 6% d.w.) to immobilise metals in acidic (pH ∼ 4.7) and basic (pH ∼ 7.4) mine soils under variable flooding conditions, and to determine biochar influence on plant (Sarcocornia fruticosa -Sf-) growth and metal uptake. BSS had lower pH (∼8.2 vs. ∼ 9.8), CaCO (∼71 vs. ∼ 85 g kg), total organic carbon (∼354 vs. ∼ 656 g kg) and higher water soluble organic carbon (WSOC ∼ 0.15 vs ∼ 0.06 mg kg) than BPT. PVC columns (15 × 30 cm) were prepared with the following treatments (n = 4): 1) no Biochar-no Sf; 2) no Biochar-Sf; 3) BSS-no Sf; 4) BSS-Sf; 5) BPT-no Sf; 6) BPT-Sf. Changes in water table level (WL) were simulated for 303 days with tap water (upper 0-15 cm alternating flooding-drying conditions, lower 15-30 cm always underwater). The pH, redox potential (Eh), temperature and porewater WSOC, Zn, Cd and Pb concentrations were regularly measured, and plants were removed at the end and length, fresh weight and metal concentrations in tissues measured. In the basic soil, there were no consistent evidences that BSS and BPT were effective decreasing porewater metal concentrations and reducing metal uptake in plants. Sf contributed to mobilise Zn, and in less extent Cd, in the upper soil layer, regardless of the type of biochar, and this effect increased with aging. In the acidic soil, BSS and BPT were effective increasing the pH and decreasing porewater metals. BSS increased its efficiency with aging, which can be mainly attributable to the more reduced conditions that induced (lower Eh values) due to its higher WSOC content. Biochar was effective hindering metal mobilisation by Sf and reducing plant's metal uptake (e.g. reduction in roots: ∼7 fold for Zn, ∼19-fold for Cd and ∼ 2-fold for Pb). BSS was more effective promoting Sf growth (fresh weight) than BPT. Therefore, in relation with the use of biochar from sewage sludge and from pruning trees as soil amendments under flooding-non flooding conditions, we can conclude that it can be a useful option in acidic mine soils for decreasing water soluble metals and improving plant growth. However, in basic mine soils, we have no evidences to support the advantages of using these two types of biochar as amendments. Hence, the use of biochar in metal-polluted wetlands has environmental implications that must be planned for each specific case in order to optimize the positive aspects (wetland as sinks of pollutants) and reduce the drawbacks (wetland as source of pollutants).
本研究旨在评估来自污水污泥的生物炭（BSS）和修剪树木的生物炭（BPT）（添加量为 6%干重）在不同淹没条件下固定酸性（pH∼4.7）和碱性（pH∼7.4）矿山土壤中金属的有效性，并确定生物炭对植物（Sarcocornia fruticosa-Sf-）生长和金属吸收的影响。BSS 的 pH 值较低（∼8.2 对∼9.8），碳酸钙（∼71 对∼85 g kg），总有机碳（∼354 对∼656 g kg）和较高的水溶性有机碳（WSOC∼0.15 对∼0.06 mg kg）低于 BPT。用以下处理方法制备了 PVC 柱（15×30 cm）（n=4）：1）无生物炭-无 Sf；2）无生物炭-Sf；3）BSS-无 Sf；4）BSS-Sf；5）BPT-无 Sf；6）BPT-Sf。用自来水模拟了 303 天的地下水位（WL）变化（上 0-15 cm 交替淹水-干燥条件，下 15-30 cm 始终水下）。定期测量 pH 值、氧化还原电位（Eh）、温度和孔隙水 WSOC、Zn、Cd 和 Pb 浓度，并在结束时取出植物，测量植物的长度、鲜重和组织中的金属浓度。在碱性土壤中，没有一致的证据表明 BSS 和 BPT 能够有效降低孔隙水中金属的浓度，并减少植物对金属的吸收。Sf 有助于在上层土壤中使 Zn 更具流动性，在较小程度上使 Cd 更具流动性，无论生物炭的类型如何，这种效应都会随着老化而增加。在酸性土壤中，BSS 和 BPT 能有效提高 pH 值并降低孔隙水中的金属。BSS 随着老化而提高其效率，这主要归因于由于其较高的 WSOC 含量而导致的更还原的条件（更低的 Eh 值）。生物炭能有效阻止 Sf 对金属的迁移并减少植物对金属的吸收（例如，根中减少：Zn 减少约 7 倍，Cd 减少约 19 倍，Pb 减少约 2 倍）。BSS 比 BPT 更有效地促进 Sf 的生长（鲜重）。因此，关于在淹水-非淹水条件下将来自污水污泥和修剪树木的生物炭用作土壤改良剂，我们可以得出结论，在酸性矿山土壤中，它可以是一种减少水溶性金属和改善植物生长的有用选择。然而，在碱性矿山土壤中，我们没有证据支持使用这两种类型的生物炭作为改良剂的优势。因此，生物炭在金属污染湿地中的使用具有环境影响，必须针对每个具体情况进行规划，以优化其积极方面（湿地作为污染物的汇），并减少其缺点（湿地作为污染物的源）。
