新疆煤田火区多环芳烃土壤污染生态风险评估与治理策略

Ecological risk assessment and remediation strategies for soil contamination by polycyclic aromatic hydrocarbons in Xinjiang Coal Fire Zones

  • 摘要: 煤田火灾是全球性生态灾害,不仅造成煤炭资源损失,同时还释放大量多环芳烃(PAHs)等有机污染物威胁区域生态安全。因此,以新疆准东煤田为研究区,选取6处火区的28组土壤样品,系统分析了16种优控PAHs的污染特征、组成谱型与毒性生态风险。结果表明:3类火区总PAHs污染水平呈现显著梯度变化,复燃火区PAHs质量分数总和(w(ΣPAHs))为180~203 219 µg/kg,以中低环组分为主体,但少量样品出现高环PAHs(如BaP、DahA)的同步增强,导致毒性当量呈数量级跃升。未治理火区w(ΣPAHs)为1 055~28 204 µg/kg,污染背景较高,裂隙带、冒气点等局部区域存在高环PAHs富集现象,生态风险显著高于周边。已治理火区w(ΣPAHs)降至395 µg/kg,污染负荷大幅削减,但少量高毒单体(如BaP)仍有残留。污染成因解析表明,w(Fla)/w(Fla+Pyr)值稳定指向燃烧源,火区PAHs主要来源于煤/生物质燃烧;w(Ant)/w(Ant+Phe)值普遍偏低,则是焦油受到了挥发—迁移—冷凝沉积过程中的环境影响。生态风险评估结果表明,煤田火区土壤中PAHs的总体生态风险较高。其中,复燃火区与未治理火区的风险尤为严峻,而已治理火区亦存在长期残留风险。毒性当量分析结果表明,中低环PAHs组分构成毒性基础,高毒高环PAHs的局部增强导致了样品毒性提高。针对3类火区提出了分类指导下精准施策的差异化治理方法,复燃火区聚焦源头控制与局部深度清除,采用地质封堵与微波辅助热解等技术遏制PAHs二次释放;未治理火区需保证火灾治理和复燃防控,在煤火治理过程中结合生物炭等修复技术降低整体土壤污染水平;已治理火区以长期监测与生态修复为核心,持续削减毒性残留风险。研究结果为煤田火区有机污染风险管控与生态修复提供了科学依据与技术支撑。

     

    Abstract: Coal fires are a global ecological disaster, leading not only to the loss of coal resources but also to the release of large amounts of organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), threatening regional ecological security. In the Zhundong coalfield, 28 soil samples from six fire zones are collected. These samples are systematically analyzed for the pollution characteristics, compositional patterns, and toxic ecological risks of 16 priority-controlled PAHs. The results show that significant gradient variations in PAH pollution levels are observed among the three types of fire zones. In the re-ignited fire zones, the total concentration of PAHs ranges from 180 to 203 219 µg/kg, with low- and medium-ring components being dominant. However, a simultaneous enhancement of high-ring PAHs (e.g., BaP, DahA) is observed in a few samples, leading to an order-of-magnitude increase in toxic equivalency. In the untreated fire zones, w(ΣPAHs) ranges from 1 055 to 28 204 µg/kg, indicating a high pollution background. Localized enrichment of high-ring PAHs is found in areas such as fracture zones and gas venting points, resulting in significantly higher ecological risks than those in surrounding areas. In the treated fire zones, w(ΣPAHs) is reduced to 395 µg/kg, indicating a substantial decrease in pollution load, although small amounts of highly toxic monomers (e.g., BaP) remain. Analysis of pollution sources reveals that the w(Fla)/w(Fla+Pyr) ratio consistently indicates a combustion source, suggesting that PAHs in the fire zones mainly originate from coal/biomass combustion. The generally low w(Ant)/w(Ant+Phe) ratio is attributed to the influence of volatilization–migration–condensation deposition processes on tar. The ecological risk assessment shows that the overall ecological risk of PAHs in coalfield fire zone soils is relatively high. Among them, the risks in re-ignited and untreated fire zones are particularly severe, while treated fire zones still exhibit long-term residual risks. The toxic equivalency analysis indicates that low- and medium-ring components form the baseline toxicity, while local enhancement of highly toxic high-ring PAHs leads to increased toxicity in certain samples. A differentiated management approach guided by classification is proposed: in re-ignited fire zones, focus is placed on source control and localized deep removal, using technologies such as geological sealing and microwave-assisted pyrolysis to inhibit secondary PAHs release. In untreated fire zones, fire control and re-ignition prevention are prioritized, and remediation techniques such as biochar application are integrated during coal fire treatment to reduce the overall soil pollution level. For treated fire zones, long-term monitoring and ecological restoration are emphasized to continuously reduce residual toxicity risks. These findings provide scientific evidence and technical support for organic pollution risk control and ecological restoration in coalfield fire zones.

     

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