Mercury in municipal solids waste incineration (MSWI) fly ash in China: Chemical speciation and risk assessment

Mercury (Hg) in municipal solid waste incineration fly ash attracts much attention for its potential risk in environment and human health. In this work, Hg in fly ashes collected from 15 cities over China was surveyed in terms of speciation, leaching behavior and health risk assessment. In general, total Hg (HgT) concentration was 1-24 mg kg−1, where fly ash in esten cities had higher HgT concentration. After systemic research, several conclusions were obtained: (1) the amount of strongly-complexed Hg was 65-94% of HgT, which was consistent with the sequential inspection result, indicating that Hg predominantly bonded to Fe oxide or Hg(I); (2) the Hg leaching test together with principal component analysis (PCA) showed that leaching level of Hg was lower than 0.2 mg/L of the USEPA regulatory limitation. This suggests that the dominating strongly-complexed Hg in HgT could probably not be leached out; (3) moreover, the health risk assessment of fly ash for workers was performed according to the main exposure pathway inhalation of mercury vapor and resuspended particles. As a result, the total non-carcinogenic risk values (HQtotal) of Hg ranged from 0.02 to 0.75, far from the “safe” threshold of 1. Therefore, our results provide the further understanding of Hg contamination level in fly ash, which is important to the fly ash management in China.