Toxicity evaluation of fly ash by Microtox®

Abstract

Fly ash samples from a cooling tower were extracted after incinerating plastic solid waste (PSW) and organic liquid waste (OLW) by n-Hexane or dichloromethane/n-Hexane mixtures to evaluate the toxicity. The metal and PCDD/Fs were analyzed by ICP OES and HRGC/HRMS, respectively. The toxicity of the extracted fly ash was evaluated by Microtox®. The results showed the environmental risk factor (ERF) of Hg in PSW fly ash was the highest compared to other metals, by more than 60%. Additionally, the acute toxicity tests of the fly ash showed that dichloromethane/n-hexane extracts were all very toxic, except for the PSW-1 obtained through Soxhlet extraction following the column clean-up procedure. The n-Hexane extracts for OLW-1 obtained through Soxhlet extraction following the column clean-up procedure were extremely toxic. There were no significant relationships among the concentrations of the regulated heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn), PCDD/Fs concentration and the TU values in the toxicity test. Furthermore, the results of the statistical analysis showed that there were significant differences in the results of the Microtox test with regard to the solvents, solutes and various extraction methods. However, it is remains a complicated process to differentiate between the various compounds in order to produce accurate results with regard to acute toxicity in the fly ash, and thus this issue warrants further investigation. © Taiwan Association for Aerosol Research.