消化和热干化污泥中多氯联苯和二(口恶)英风险评估

Risk Assessment of PCBs and PCDD/Fs in Digested Sludge and Thermal Drying Sludge

采用同位素稀释法的高分辨气相色谱-质谱仪测定了厌氧消化污泥和热干化污泥中多氯联苯(PCBs)及二(口恶)英(PCDD/Fs)的浓度,并结合发光菌急性毒性实验,评估了厌氧消化污泥和热干化污泥的生态风险。结果表明,二(口恶)英类多氯联苯(DL-PCBs)和PCDD/Fs的毒性当量(TEQs,以干泥计)为1.50~32.50 pg/g,低于欧盟设定的限值(100 pg/g)。其中,PCB 28和PCB 118分别是指示性PCBs(I-PCBs)和DL-PCBs中浓度最高的物质。热干化污泥中的PCB 28及PCB 180浓度均与I-PCBs浓度呈显著正相关(P<0.05)。厌氧消化污泥中的PCDD/Fs组成变化较大,在样品S1~S6中,八氯代二苯并呋喃(OCDF)的浓度最高,占比为66.2%~88.9%,其余样品中八氯代二苯并二(口恶)英(OCDD)的浓度占比最大。污泥龄是影响PCDD/Fs浓度的主要因素。与厌氧消化污泥不同,热干化污泥均以OCDD为主。发光菌急性毒性实验结果表明,厌氧消化污泥和热干化污泥的水溶液在15min时对费氏弧菌的半数有效浓度(EC_(50))分别为76.3和30.4 g/L,30 min时分别为21.6和12.5 g/L。热干化污泥对费氏弧菌的抑制率高于厌氧消化污泥,与TEQs_((DL-PCBs+PCDD/Fs))的结果相反,表明在评估污泥生态风险时,单一的化学物质分析不能全面反映污泥的生态风险,需要综合考虑多种因素。

This paper determined the concentrations of polychlorinated biphenyls(PCBs)and dioxins(PCDD/Fs)in anaerobic digestive sludge and thermal drying sludge by isotope‑dilution high‑resolution gas chromatography‑tandem high‑resolution mass spectrometry,and assessed their the ecological risk by acute toxicity test of photoluminescence bacteria.The toxic equivalents(TEQs)of dioxin‑like PCBs(DL‑PCBs)and PCDD/Fs ranged from 1.50 pg/g to 32.50 pg/g(measured in dry sludge),which were lower than the standard value of 100 pg/g set by the European Union.Among them,PCB 28 and PCB 118 were the most abundant substances in indicative PCBs(I‑PCBs)and DL‑PCBs,respectively.The concentrations of PCB 28 and PCB 180 in thermal drying sludge were significantly positively correlated with the concentration of I‑PCBs(P<0.05).The composition of PCDD/Fs in anaerobic digestive sludge varied greatly.Octachlorodibenzofuran(OCDF)had the highest concentration in samples S1-S6,accounting for 66.2%-88.9%,while octachlorodibenzodioxin(OCDD)had the highest concentration in other samples.Sludge age was the main factor affecting the concentration of PCDD/Fs.Different from anaerobic digestive sludge,OCDD was dominant in the thermal drying sludge.The results of acute toxicity test showed that the 50%effective concentrations(EC_(50))of anaerobic digestive sludge and thermal drying sludge against Vibrio fischeri were 76.3 g/L and 30.4 g/L at 15 min and 21.6 g/L and 12.5 g/L at 30 min,respectively.The inhibition rate of thermal drying sludge against Vibrio fischeri was higher than that of anaerobic digestive sludge,which was contrary to the results of TEQs(DL‑PCBs+PCDD/Fs).Therefore,a single chemical analysis could not fully reflect the ecological risk of sludge,and multiple factors should be comprehensively considered.