College of Energy and Environment Shenyang Aerospace University, No.37 Daoyi southstreet, Shenbei new district, Shenyang 110122, China.
State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Ecotoxicol Environ Saf. 2021 Dec 20;227:112900. doi: 10.1016/j.ecoenv.2021.112900. Epub 2021 Oct 19.
Pentachlorophenol (PCP) is a common residual organic pollutant in paddy soil, and its harmful effects on soil ecosystems have been confirmed. Humic acid (HA) could act as an electron shuttle to promote the reductive dechlorination of PCP under anaerobic conditions. Humic-like substances produced by composting of kitchen waste were able to facilitate the reductive dechlorination of PCP during Fe(III) oxide reduction by iron-reducing bacteria. However, the effects of compost-derived HAs on reductive dechlorination of PCP in a paddy soil system with a high iron content have not been fully confirmed. The characteristics of HAs from different stages of composting during bio-dechlorination of PCP were still unclear. The functional components of compost-derived HAs, which are responsible for reductive dechlorination of PCP in different stages of composting, also need further investigation. In this study, we conducted a series of experiments on the Guangdong paddy soil system with high iron content (17.5 mg kg) to investigate the reductive dechlorination of PCP by HA in the early, middle, and later stages of food waste composting. The results showed that the middle- and late-stages of compost-derived HAs all promoted reductive dechlorination of PCP in the paddy system, but it was opposite in the early-stage. Significant differences were also presented in the components of HAs from different stages of composting. The early-stage compost-derived HAs contain numerous easy degradable components, it would inhibit the dechlorination of PCP by the changes of microbial metabolism in paddy soil. Compost-derived HAs in the middle composting stage showed the best reductive dechlorination effects on PCP. The reason might be that the compost-derived HAs in the middle composting stage could act both as electron donors and transfers. The electron transfer capacities (ETC) of middle-stage compost-derived HAs were significantly higher than those in the early and later composting stages. Compared with the natural HAs in the soil system, compost-derived HAs contained more chlorinated products with lower toxicities after the PCP degradation. This result mainly contributed to the detoxification and mineralization of PCP in the soil. These findings clarified the effects of compost-derived HAs on PCP bio-dechlorination in paddy soil with high iron content, identifying the optimal phase of compost-derived HA and providing a theoretical basis for the utilization of kitchen waste composting as a resource of HA.
五氯苯酚（PCP）是稻田土壤中常见的残留有机污染物，其对土壤生态系统的有害影响已得到证实。腐殖酸（HA）可以作为电子穿梭体，在厌氧条件下促进 PCP 的还原脱氯。厨余垃圾堆肥产生的类腐殖质物质能够促进铁还原菌还原三价铁氧化物时 PCP 的还原脱氯。然而，堆肥衍生的 HA 对高铁含量稻田土壤系统中 PCP 还原脱氯的影响尚未得到充分证实。在 PCP 生物脱氯过程中，不同堆肥阶段产生的 HA 的特性仍不清楚。负责堆肥不同阶段 PCP 还原脱氯的堆肥衍生 HA 的功能成分也需要进一步研究。在这项研究中，我们对高铁含量（17.5mg/kg）的广东稻田系统进行了一系列实验，以研究厨余垃圾堆肥中 HA 在早期、中期和后期对 PCP 的还原脱氯作用。结果表明，堆肥中后期产生的 HA 均促进了稻田系统中 PCP 的还原脱氯，但在早期则相反。不同堆肥阶段产生的 HA 的成分也存在显著差异。早期堆肥产生的 HA 含有大量易降解成分，会通过改变稻田土壤中的微生物代谢来抑制 PCP 的脱氯作用。堆肥中期产生的 HA 对 PCP 的还原脱氯效果最好。原因可能是堆肥中期产生的 HA 既可以作为电子供体，又可以作为电子传递体。堆肥中期产生的 HA 的电子传递能力（ETC）明显高于早期和后期堆肥阶段。与土壤系统中的天然 HA 相比，PCP 降解后堆肥产生的 HA 含有更多毒性较低的氯化产物。这一结果主要归因于 PCP 在土壤中的解毒和矿化。这些发现阐明了堆肥衍生的 HA 对高铁含量稻田土壤中 PCP 生物脱氯的影响，确定了堆肥衍生的 HA 的最佳阶段，并为利用厨余垃圾堆肥作为 HA 资源提供了理论依据。
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