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. 2026 Mar 6;14(3):226.
doi: 10.3390/toxics14030226.

The Levels, Speciation, and Influencing Factors of Mercury in MSWI Fly Ashes of a High Geological Background Area

Liangliang Yang  1   2 , Li Tang  3 , Qingfeng Wang  4 , Guangyi Sun  2 , Peng Liu  5 , Tianrong He  1 , Zhonggen Li  2   4
Affiliations

The Levels, Speciation, and Influencing Factors of Mercury in MSWI Fly Ashes of a High Geological Background Area

Liangliang Yang et al. Toxics. .

Abstract

Fly ash (FA) captures most mercury (Hg) in the waste stream during municipal solid waste incineration (MSWI), and the content and speciation of Hg in MSWI fly ash (MSWI-FA) have a significant impact on the ecological environment. In this study, 245 fly ash samples were collected from 18 MSWI facilities in Guizhou Province, a fragile karst area with a high Hg background in Southwest China. The results indicate that total Hg ranged from 0.52 to 444 mg/kg among samples, while the geometric means varied from 0.85 to 223.33 mg/kg for different incinerators, with a weighted geometric mean of 22.14 mg/kg, more than double the national average. Substantial temporal variability in Hg content suggested intermittent inputs of Hg-rich waste into the MSW stream. While positive correlations (p < 0.05) were observed between Hg and chlorine, potassium, and cadmium, the moderate to low R2 values indicate that Hg enrichment is a complex multi-factor system influenced by heterogeneous waste compositions and transient thermochemical conditions. Speciation analysis revealed that most of the Hg exists in its elemental form (F4), constituting over 80% of the total Hg. However, the water-soluble fraction (F1) and the ion-exchangeable fraction (F2) each reached up to 26-29% in some samples, indicating substantial environmental mobility. These findings demonstrate that MSWI-FA in Guizhou contains elevated Hg levels, posing considerable ecological and environmental risks. Enhancing the classification and management of Hg-containing waste in MSW is critical to mitigating the environmental risks of fly ash, particularly in karst ecological areas.

Keywords: MSWI-FA; distribution patterns; influencing factors; mercury; speciation.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure A1
Figure A1
Correlation between Hg and other elements in incineration fly ash.
Figure A1
Figure A1
Correlation between Hg and other elements in incineration fly ash.
Figure 1
Figure 1
Spatial distribution of the 18 investigated MSWI plants and major mercury mines in Guizhou Province, Southwest China.
Figure 2
Figure 2
Boxplot of Hg concentrations in fly ash from different incineration plants with more than five samples per facility.
Figure 3
Figure 3
Temporal variation in Hg concentrations in MSWI-FA from the six selected incinerators (#9–#14).
Figure 4
Figure 4
Correlations between Hg and potassium (K), chlorine (Cl), sodium (Na), and cadmium (Cd) in MSW-FA (the (left) column shows the data while the (right) column shows the data excluding plant #11).
Figure 5
Figure 5
Speciation of Hg in different MSWI-FA samples. (Suffixes ‘a’ and ‘b’ (e.g., #4a, #4b) denote different representative samples collected from the same incineration facility at different sampling intervals).
See this image and copyright information in PMC

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