Pollutants release characteristics and environmental risk assessment in long-term leaching process of stockpiled coal fly ash

doi:10.16085/j.issn.1000-6613.2025-0056

Abstract

Abstract:

To investigate the release characteristics and environmental impacts of pollutants from stockpiled coal fly ash, this study focused on the circulating fluidized bed coal fly ash from a power plant in Yulin, Shaanxi Province. The research explored the release patterns and environmental risks of Cr, Cu, As, Se, Mo, Ba, F^-, COD, and TN under the influence of rainfall. The results indicated that, the leaching rates of pollutants during the leaching process followed the order was Mo > Se > F^- > TN > As > Cu > Ba > COD > Cr. Mo had the highest release rate (77.74%) and Cr the lowest, which was related to its predominant as residual species in the coal fly ash. During the column leaching process, the concentration of F^- initially decreased, then increased, and eventually stabilized, while the concentrations of other pollutants generally decrease over time before stabilizing. Under different pH conditions, the release amounts of Cr, Cu, As, and Ba was highest at pH = 3, Se, COD, and TN at pH = 5, and Mo and F^- at pH = 7. Kinetic analysis showed that the release of Cr, Cu, Se, Mo, and Ba followed a second-order kinetic model, while F^-, COD, and TN fitted the Freundlich model. As followed a parabolic model at pH = 3 and the Freundlich model at pH = 5 and 7. Based on model fits, Se and F^- were predicted to exceed local soil background levels within five years. Risk assessment results indicated that the concentrations of As, Se, Mo, F^-, COD, and TN in the leachate exceeded the Class Ⅲ standard limits for surface water and groundwater. RAC evaluation showed that the risk of trace elements followed the order was Se > As > Mo > Cu > Ba > Cr, with Se posing a medium risk and the others a low risk. Potential ecological risk assessment indicated that As, Cu, and Cr pose minor ecological risks. Both methods showed consistent risk rankings for As, Cu, and Cr, with As > Cu > Cr. These findings provide a reference for understanding pollutants release and managing the environmental risks associated with coal fly ash.

Key words: stockpiled coal fly ash, leaching, heavy metals, environmental risk

摘要：

为研究堆存粉煤灰中污染物释放特征及其环境影响，以陕西榆林某电厂循环流化床粉煤灰为研究对象，探究了其在降雨影响下，污染物Cr、Cu、As、Se、Mo、Ba、F^-、COD、TN释放规律及其环境风险。结果表明，浸出过程中污染物浸出率为Mo>Se>F^->TN>As>Cu>Ba>COD>Cr，Mo浸出率最高（77.74%），Cr最低，主要以残渣态赋存有关。淋溶过程中，F⁻浓度呈先下降再上升后趋稳的规律，其余污染物均大致随时间逐渐降低后趋稳；不同pH条件下，Cr、Cu、As、Ba在pH=3，Se、COD、TN在pH=5，Mo、F^-在pH=7时释放量最高；动力学分析表明，Cr、Cu、Se、Mo、Ba的释放符合二级动力学方程，F^-、COD、TN符合Freundlich方程，As在pH=3时符合抛物线方程，在pH=5、7时符合Freundlich方程。根据拟合结果对污染物释放量进行预测，Se、F在5年内可能会超出当地土壤背景值。风险评估结果表明，浸出液中As、Se、Mo、F^-、COD、TN均超出地表水或地下水体Ⅲ类标准限值；RAC评估表明，微量元素风险依次为Se>As>Mo>Cu>Ba>Cr，Se为中等风险，其余为低风险，潜在生态风险评估表明As、Cu、Cr的潜在生态风险为轻微污染。两种方法对As、Cu、Cr的风险大小评价结果一致，均为As>Cu>Cr。本研究可为堆存粉煤灰的污染物释放与环境风险管理提供数据参考。

关键词: 堆存粉煤灰, 淋溶, 重金属, 环境风险

CLC Number:

X705

LU Yongqi, XIAO Jianing, DIE Qingqi, XU Siqi, HUANG Ruixiao, KONG Xiangrui, YANG Yufei. Pollutants release characteristics and environmental risk assessment in long-term leaching process of stockpiled coal fly ash[J]. Chemical Industry and Engineering Progress, 2025, 44(9): 5479-5490.

卢永琦, 肖嘉宁, 迭庆杞, 徐思琪, 黄瑞潇, 孔祥蕊, 杨玉飞. 堆存粉煤灰长期淋溶过程污染物释放特征与环境风险评估[J]. 化工进展, 2025, 44(9): 5479-5490.

Figures/Tables 19

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步骤	重金属提取形态	提取方法
1	弱酸提取态	加入40mL 0.11mol/L的HOAc，于25℃、180r/min下水平振荡16h
2	可还原态	剩余残渣中加入40mL 0.5mol/L的NH₂OH·HCl，调节pH=2，于25℃、180r/min下水平振荡16h
3	可氧化态	剩余残渣中加入10mL 30% H₂O₂，室温下消解1h，后放入85℃水浴锅消解1h，加入50mL 1mol/L的NH₄Ac，pH=2，于25℃、180r/min下水平振荡16h
4	残渣态	剩余残渣转入消解管中，依次添加4mL HNO₃、1mL HCl、1mL HF、1mL H₂O₂，转入微波消解仪中消解

步骤	重金属提取形态	提取方法
1	弱酸提取态	加入40mL 0.11mol/L的HOAc，于25℃、180r/min下水平振荡16h
2	可还原态	剩余残渣中加入40mL 0.5mol/L的NH₂OH·HCl，调节pH=2，于25℃、180r/min下水平振荡16h
3	可氧化态	剩余残渣中加入10mL 30% H₂O₂，室温下消解1h，后放入85℃水浴锅消解1h，加入50mL 1mol/L的NH₄Ac，pH=2，于25℃、180r/min下水平振荡16h
4	残渣态	剩余残渣转入消解管中，依次添加4mL HNO₃、1mL HCl、1mL HF、1mL H₂O₂，转入微波消解仪中消解

	指标	方法	仪器
固相	金属元素	《固体废物金属元素测定电感耦合等离子体质谱法》（HJ 766—2015）	电感耦合等离子体质谱仪（Agilent 7500a，安捷伦公司，美国）
	氟化物	《固体废物氟的测定碱熔-离子选择电极法》（HJ 999—2018）	离子计（PXSJ-227L，上海雷磁）
	TOC	《土壤有机碳的测定重铬酸钾氧化-分光光度法》（HJ 615—2011）	紫外可见分光光度计（TU-1901）
	TN	《元素分析仪分析方法通则》（JY/T 0580—2020）	元素分析仪（德国Elementar Vario MACRO cube）
液相	F^-	《水质无机阴离子（F^-、Cl^-、NO₂^-、Br^-、NO₃^-、PO₄^2-、SO₃^2-、SO₄^2-）的测定离子色谱法》（HJ 84—2016）	离子色谱仪（ICS3000，美国戴安）
	COD	《水质化学需氧量的测定快速消解分光光度法》（HJ/T 399—2007）	紫外可见分光光度计（TU-1901）
	TN	《水质总氮的测定碱性过硫酸钾消解紫外分光光度法》（HJ 636—2012）	紫外可见分光光度计（TU-1901）

	指标	方法	仪器
固相	金属元素	《固体废物金属元素测定电感耦合等离子体质谱法》（HJ 766—2015）	电感耦合等离子体质谱仪（Agilent 7500a，安捷伦公司，美国）
	氟化物	《固体废物氟的测定碱熔-离子选择电极法》（HJ 999—2018）	离子计（PXSJ-227L，上海雷磁）
	TOC	《土壤有机碳的测定重铬酸钾氧化-分光光度法》（HJ 615—2011）	紫外可见分光光度计（TU-1901）
	TN	《元素分析仪分析方法通则》（JY/T 0580—2020）	元素分析仪（德国Elementar Vario MACRO cube）
液相	F^-	《水质无机阴离子（F^-、Cl^-、NO₂^-、Br^-、NO₃^-、PO₄^2-、SO₃^2-、SO₄^2-）的测定离子色谱法》（HJ 84—2016）	离子色谱仪（ICS3000，美国戴安）
	COD	《水质化学需氧量的测定快速消解分光光度法》（HJ/T 399—2007）	紫外可见分光光度计（TU-1901）
	TN	《水质总氮的测定碱性过硫酸钾消解紫外分光光度法》（HJ 636—2012）	紫外可见分光光度计（TU-1901）

成分	质量分数/%	成分	质量分数/%
SiO₂	54.23±0.35	K₂O	2.14±0.04
Al₂O₃	19.84±0.72	MgO	1.03±0.01
Fe₂O₃	8.59±0.18	Na₂O	1.15±0.03
CaO	8.13±0.35	Cl	0.13±0.01
SO₃	3.08±0.1	P₂O₅	0.54±0.02
TiO₂	1.53±0.04	MnO	0.09±0.02