UC Santa Cruz

Mercury, a highly toxic heavy metal, remains of global concern due to its capacity to cause significant harm to human health and the environment. Mercury (Hg) can travel long distances within the atmosphere, bioaccumulate in living organisms, and act as a potent neurotoxin. Mercury contamination remains a prevalent issue due to historic mining practices, as it was once mined for various industrial applications and for its ability to form a gold amalgam. Large amounts of mine waste, also known as calcines, remain at historic mercury mines, representing significant sources of Hg emissions to the local environment through wet and dry atmospheric deposition. Even though the presence of mercury contamination at these abandoned mines has been documented, there is a notable gap in our understanding of how mercury emissions from mine waste can contaminate the environment through atmospheric transport. This study aims to investigate the spatial and temporal environmental impacts of Hg emissions and determine atmospheric pathways of contamination from mine waste at the New Almadén Mining District (NAMD) and the Sulphur Bank Mercury Mine (SBMM) in Northern California. However, traditional methods of monitoring atmospheric mercury present challenges due to the high cost of equipment and the temporal and spatial variability of air pollution. So, in this study, we employed lichen as a bioindicator of atmospheric mercury emissions due to its abundance in the study area, low cost, and past success in using lichen to record Hg. Measuring total mercury concentrations across various lichen species and locations at the NAMD and the SBMM allowed us to identify Hg emission hotspots and provide valuable insights into the spatial and temporal distribution of Hg in a contaminated environment. The concentration of total mercury in lichen samples reached 45 ppm at the Sulphur Bank Mercury Mine, indicating significant levels of contamination in historic calcine processing areas.