Study on pollution characteristics and environmental risk of coal coking residues

The tar slag, coal tar, ammonium sulfate tar, coke powder and residual sludge were collected from a coal coking enterprise. The concentrations and different ring distribution of 16 priority controlled polycyclic aromatic hydrocarbons (PAHs) were analyzed by gas chromatography-mass spectrometry (GC-MS), and 8 heavy metals were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Meanwhile, the environmental risks of coal coking residues were analyzed by calculating the BaP equivalent toxicity concentration and the potential ecological risk index of heavy metals. The results showed that the total PAHs concentrations of five residues ranged from 0.94 mg/kg to 238 367 mg/kg, with the order of coal tar > tar slag > ammonium sulfate tar > coke powder > residual sludge, and the concentrations of highly mutagenic and carcinogenic compounds in tar slag, coal tar and ammonium sulfate tar exceeded the limits of Identification Standards for Hazardous Wastes- Identification for Toxic Substance Content (GB 5085.6—2007). The concentration of Zn in tar slag, coal tar, coke powder and residual sludge was the highest, and ammonium sulfate tar had the highest concentration of As. The BaP equivalent toxic concentration of the five residues was 0.31-9 586.96 mg/kg, and coal tar, tar slag and ammonium sulfate tar had higher cancer risk. Hg had the highest potential environmental risk among the five residues, and all the five residues had a strong potential ecological risk to the soil.