Temporal Variability in Ambient Mercury Concentrations in the Colorado Front Range

Atmospheric mercury (Hg), an airborne heavy metal, can be deposited into aquatic and terrestrial systems, potentially causing serious damage to ecosystems and human health. It is therefore important to understand the sources, chemical cycling, and fate of atmospheric mercury. This study looks at total gaseous mercury (TGM) concentrations collected at an urban, near-road site in Colorado Springs, CO from June - October, 2016 and at the Rocky Flats National Wildlife Refuge in Louisville, CO, from June - August, 2018. The 2016 data set reveals a significant diurnal pattern, with hourly average TGM concentrations reaching a maximum at 3:00 (1.91±0.34 ng/m³) and minimum at 13:00 (1.56±0.15 ng/m³). We also observe a seasonal pattern, with significantly higher average TGM concentrations in summer (June – August) than fall (September – October). In contrast, at Rocky Flats in summer 2018 we find that hourly-average concentrations peak at 13:00 (1.51±.11 ng/m³) and are lowest at 6:00 (1.40±0.10 ng/m³). In addition to TGM data, we use meteorological and chemical measurements to investigate the sources and processes behind atmospheric Hg concentrations in the Colorado Front Range.