Zhang Zhiguo, Cai Weiqing, Hu Youbiao, Yang Ke, Zheng Yonghong, Fang Chao, Ma Chengnan, Tan Yuning
School of Earth and Environment, Anhui University of Science and Technology, Huainan, China.
Institute of Energy, Hefei Comprehensive National Science Center, Hefei, China.
Front Chem. 2022 Jul 22;10:932133. doi: 10.3389/fchem.2022.932133. eCollection 2022.
In order to promote and broaden the utilization of fly ash as a resource, the fly ash from a 2,660-MW coal-fired power plant in Huainan (China) was investigated. The physical and chemical properties of fly ash were characterized by scanning electron microscopy, energy spectrum analysis, and XRD. The content and different forms of the heavy metals Cd, Cr, Cu, Co, and Ni were determined by acid digestion, oscillation leaching, and Tessier five-step extraction. The effect of pH, temperature, and particle size on the leached amount of heavy metals was studied. Finally, the ecological risk index was calculated for each heavy metal the risk assessment coding (RAC) method and Hakanson ecological risk assessment method, allowing the ecological risk of fly ash to be determined under different environmental conditions. Results showed that the average concentrations of Cd, Cr, Co, and Ni were all below the risk screening values reported for environmental pollutants (pH > 7.5). Under varying pH, temperature, and particle size conditions, the leached amounts (oscillation leaching) were below the soil risk screening values for agricultural land in China. An RAC-Cd value of >50% indicates a high ecological risk, while the RAC values of Co and Ni were between 10 and 30%, indicating a medium ecological risk, and the RAC values of Cr and Cu were <10%, indicating a low ecological risk. With increasing pH, the potential ecological risk index (RI) decreased, with a maximum RI of 59.62 observed at pH 2.8. With increasing temperature, the potential ecological RI increased initially to a maximum of 27.69 at 25°C and then decreased thereafter. With increasing particle size, the ecological RI decreased, with the highest RI of 4.06 occurring at <0.075 mm. The Hakanson ecological RI value was below 150, indicating a slight ecological risk. Therefore, fly ash can be considered as a soil additive and conditioner that is suitable for use in the improvement of reclamation soil in coal mining subsidence areas.
为了促进和扩大粉煤灰作为一种资源的利用，对中国淮南一座266万千瓦燃煤电厂的粉煤灰进行了研究。通过扫描电子显微镜、能谱分析和XRD对粉煤灰的物理和化学性质进行了表征。采用酸消解、振荡浸出和Tessier五步提取法测定了重金属Cd、Cr、Cu、Co和Ni的含量及不同形态。研究了pH值、温度和粒径对重金属浸出量的影响。最后，采用风险评估编码（RAC）法和Hakanson生态风险评估法计算了各重金属的生态风险指数，从而确定了不同环境条件下粉煤灰的生态风险。结果表明，Cd、Cr、Co和Ni的平均浓度均低于环境污染物报告的风险筛选值（pH>7.5）。在不同的pH值、温度和粒径条件下，浸出量（振荡浸出）均低于中国农业用地土壤风险筛选值。RAC-Cd值>50%表示生态风险高，而Co和Ni的RAC值在10%至30%之间，表示中等生态风险，Cr和Cu的RAC值<10%，表示低生态风险。随着pH值的升高，潜在生态风险指数（RI）降低，在pH值为2.8时观察到最大RI为59.62。随着温度的升高，潜在生态RI最初升高，在25°C时达到最大值27.69，然后随后降低。随着粒径的增加，生态RI降低，在<0.075毫米时出现最高RI为4.06。Hakanson生态RI值低于150，表明生态风险轻微。因此，粉煤灰可被视为一种土壤添加剂和改良剂，适用于煤矿塌陷区复垦土壤的改良。
