Biochar inhibited hydrogen radical-induced Cd bioavailability in a paddy soil
Biochar inhibited hydrogen radical-induced Cd bioavailability in a paddy soil
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DOI：
10.1016/j.scitotenv.2023.164521
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发表时间：
2023-06-15
影响因子：
9.8
通讯作者：
Rinklebe，Jorg
中科院分区：
文献类型：
--
作者：
Li，Taige;Li，Wenjing;Rinklebe，Jorg
氢（H·）自由基是产生羟基（OH·）自由基的一条新途径，它促进了硫化镉（CdS）的溶解，从而促进了镉在水稻土中的溶解。在土壤培养试验中，淹水水稻土中Cd的生物有效性随通气时间的延长而增加，通气时间为3d时Cd的生物有效性增加了8.44%。首次在曝气土壤污泥中观察到H·自由基。随后在电解实验中证实了CdS溶解与自由基的关联。通过电子顺磁共振分析证实了电解水中存在H·和OH·自由基。在添加CdS的体系中，电解水使可溶性Cd ~（2+）浓度提高了60.92倍，而自由基清除剂的加入使可溶性Cd ~（2+）浓度降低了43.2%。这证实了自由基可以导致CdS的氧化溶解。在紫外光照射下，富里酸和邻苯二酚体系均产生H·自由基，表明土壤有机碳可能是H·和OH·自由基的重要前体。施用生物质炭除吸附外，还通过其他机制使土壤DTPA-Cd含量降低22- 56%.首先，生物炭猝灭自由基，使电解水中CdS的溶解减少23.6%，其中生物炭的-C-OH被氧化为C双键O。其次，生物炭促进Fe/S还原菌，从而损害CdS溶解，证实了土壤有效Fe 2+和DTPA-Cd浓度之间的反向相关性。在接种希瓦氏菌MR-1的土壤中也出现了类似的现象。本研究为镉的生物有效性研究提供了新的思路，并为生物炭修复镉污染水稻土提供了可行的措施。
Herein, hydrogen (H·) radical was observed as a new pathway to produce hydroxyl (OH·) radicals that promoted cadmium sulfide (CdS) dissolution and thus Cd solubility in paddy soils. In soil incubation experiments, the bioavailable Cd concentrations in flooded paddy soils were increased by 8.44 % as the soil was aerated for 3d. For the first time, the H· radical was observed in aerated soil sludge. The association of CdS dissolution with free radicals was thereafter confirmed in an electrolysis experiment. Both H· and OH· radicals in electrolyzed water were confirmed by the electron paramagnetic resonance analysis. In the system with CdS, water electrolysis increased soluble Cd2+concentration by 60.92 times, which was compromised by 43.2 % when the radical scavenger was introduced. This confirmed the free radicals can lead to oxidative dissolution of CdS. The H· radical was generated in systems with fulvic acid or catechol irradiated by ultraviolet lights, indicating soil organic carbon could be an important precursor for H· and OH· radicals. Biochar application decreased soil DTPA-Cd by 22–56 % invoking mechanisms besides adsorption. First, biochar quenched radicals and reduced CdS dissolution by 23.6 % in electrolyzed water in which -C-OH of biochar was oxidized to Cdouble bondO. Second, biochar boosted Fe/S-reducing bacteria and thus compromised CdS dissolution, as affirmed by a reversal correlation between soil available Fe2+and DTPA-Cd concentrations. A similar phenomenon occurred inShewanella oneidensisMR-1-inoculated soils. This study provided new insights into the bioavailability of Cd and offered feasible measures to remediate Cd-contaminated paddy soils with biochars.