Banda Maria Fezile, Matabane Dithobolong Lovia, Munyengabe Alexis
Tshwane University of Technology, Faculty of Science, Department of Chemistry, Pretoria, 0001, Private Bag X680, South Africa.
Heliyon. 2024 Nov 30;10(23):e40741. doi: 10.1016/j.heliyon.2024.e40741. eCollection 2024 Dec 15.
Coal fly ash (CFA) is a predominant waste by-product of coal combustion which is disposed of in open ash dams that utilize large pieces of land. This waste material is classified as a hazardous substance in South Africa as well as in other countries due to its fine particles that are easily blown to the atmosphere and the unacceptable levels of heavy metals and persistent organic pollutants. Contaminants in CFA can pollute surface and ground water, agricultural sites, soil and therefore pose risks to the health of humans and the environment. More than 500 million tons of CFA is produced yearly and over 200 million tons remain unused globally. The production will continue due to high consumer energy demands, especially in countries with heavy reliance on coal for power generation. Despite a significant progress made on the application of phytoremediation approach for decontamination of polluted sites, there is very limited evidence for its potential in the rehabilitation of CFA dumps. Low organic carbon, microbial activities and availability of nutrients including nitrogen contribute to restricted plant growth in CFA, and therefore converting ash dumps to barren lands devoid of vegetation. Leguminous plant species can fix atmospheric nitrogen through symbiotic association with bacteria. Therefore, their intercropping mixture development can improve the chemistry of the substrate and facilitate nutrients availability to the companion plants. This approach can enhance the performance of phytoremediation and promote sustainable practices. The paper provides an overview of the ongoing burden of CFA disposal and discusses the ecological and economic benefits of using legumes, aromatic and bioenergy plants. We identify knowledge gaps to establishing vegetation in ash dumping sites, and provide insights to encourage continued research that will enhance the applicability of phytoremediation in restoration programs.
煤粉煤灰（CFA）是煤炭燃烧产生的主要废弃物副产品，通常被倾倒在占用大片土地的露天灰坝中。由于其细小颗粒容易被吹到大气中，以及重金属和持久性有机污染物含量超标，这种废料在南非和其他国家都被归类为有害物质。CFA中的污染物会污染地表水和地下水、农业用地及土壤，因此对人类健康和环境构成风险。每年产生的CFA超过5亿吨，全球仍有超过2亿吨未被利用。由于消费者对能源的高需求，特别是在严重依赖煤炭发电的国家，其产量还将继续增加。尽管在应用植物修复方法净化污染场地方面取得了重大进展，但关于其在修复CFA堆场方面的潜力的证据非常有限。低有机碳、微生物活性以及包括氮在内的养分有效性导致CFA中植物生长受限，从而使灰堆场变成没有植被的荒地。豆科植物物种可以通过与细菌的共生关系固定大气中的氮。因此，开发它们的间作混合物可以改善基质的化学性质，并促进伴生植物获得养分。这种方法可以提高植物修复的性能并促进可持续实践。本文概述了CFA处置带来的持续负担，并讨论了使用豆类、芳香植物和生物能源植物的生态和经济效益。我们确定了在灰堆场建立植被方面的知识空白，并提供见解以鼓励持续研究，从而提高植物修复在恢复项目中的适用性。
