The effect of sub-zero temperature cycling on the flux of mercury from soils
Mercury flux from frozen soils has been shown to increase during periods of temperature change in past field-experiments. Due to the nature of these experiments, the influence of individual environmental parameters on the flux of mercury during periods of changing temperature could not be identified. This research isolates both soil temperature and soil moisture content at subzero temperatures in order to determine the effect of both on mercury flux. The completed research observed the flux of total gaseous mercury from frozen soils in a dynamic flux chamber and scientific grade freezer using a Tekran 2537a mercury analyzer. Additionally, soil temperature, air temperature and relative humidity were recorded during experimentation. It was found that mercury flux from soils was suppressed significantly over some temperature ranges below 10°C. This research also found that periods of rapid positive change in soil temperature resulted in a significant increase in mercury flux from frozen soils. This effect, which saw spikes in mercury flux approach levels seen at room temperature, is proposed to be a result of physical changes in the soil during temperature change. This effect was exaggerated at lower temperatures and was found to be most prevalent at soil moisture contents around 60% of field capacity.