Ambient Air Mercury Concentrations at The Geysers

Abstract

From June 19 to December 16,1986, PG&E conducted ambient air mercury measurements at six stations downwind of the Geysers in Lake County. The stations were located in populated areas on the eastern side, within the geothermal field at worst case locations, and adjacent to geothermal plants and old mercy mining facilities. The mercury measurements were taken for 24 hours on a sixty day cycle. The lower detection limit of this technique was approximately 1 ng/m3 (nanogram per cubic meter) of air. Overall, the ambient levels of gaseous mercury were low. The average was 5.8 ng/m3 for the test period, with a maximum concentration of 23.6 ng/m3. These data are similar to the estimated average atmospheric levels worldwide 10 ng/m3. A statistically significant relationship was determined to exist between ambient mercury and air temperature. A correlation was also evident between rainfall and a decrease of mercury concentration during the testing period.