Influence of Soil Organic Matter Quality on Mercury Mobility and Methylation in Selected Forest Soils of the Czech Republic

This study investigates the interrelationships between soil organic matter (SOM) quality characteristics and key mercury species in two sites in Czech Republic under historical Hg contamination. SOM properties derived from DRIFT spectral analysis including the aromaticity index (iAR), potential wettability index (PWI), decomposability index (DI), and organic matter quality index (OMQ) along with additional SOM quantity and quality indicators were evaluated against several key Hg fractions (Total Hg (HgT), potentially mobilizable Hg (HgPM), potentially mobilizable Hg ions (Hg2+), methylmercury (MeHg), and water-soluble Hg (HgWS)). Neural network analysis revealed that type of horizon (organic or mineral) as well as SOM quality characteristics play an important role in Hg mobility and methylation processes. The results show the difference in relevant SOM quality properties that affect Hg mobility and methylation that can also be opposite based on the soil horizon type for the same soil, potentially forcing different pathways for the mobilization and methylation, and indicating that the state of transformation of organic matter and its quality characteristics along with the environmental conditions are some of the key attributes influencing mobility and methylation processes of Hg in the soil.