DISTRIBUTION OF MERCURY IN THE ATMOSPHERE OVER IDRIJA, SLOVENIA

Idrija mine, the second largest mercury mine in the world, was in use since 1490. More than 107 000 tons of Hg were produced in its five cen turies of history until 1990 when production was reduced to a few hund red kilos per year. The average recovery rate of mercury has been esti mated to 73%; much of the remaining 27% was dissipated into the enviro nment. In spite of present minimal levels of production, and only a fe w days of smelter operation per year, a real time survey with a mercur y Zeeman analyser in a car showed relatively high mercury concentratio ns in the air. Amounts of 300-4000 ng Hg m(-3) have been round around both the major sources of mercury vapour, the smelter and mine ventila tion shaft-while the amounts at the Old Place, at the City Museum, and near the Nikova-Idrijca confluence are of the order of 50 ng m(-3). P olluted air will be transported from those sources to a degree which d epends on the weather conditions, mainly the direction and intensity o f the wind. The high mercury contents in the air are not only due to a nthropogenic sources (smelter and the ventilation shaft, dumps and sme lter slag used in construction), but may also partly be natural as in the Front area, where the outcropping bedrock contains native mercury.