Use of Field Measurements of Mercury Vapour Emissions from soil in risk assessment procedure for a polluted site

In a Tier 2 application of the RBCA (Risk Based Corrective Action) procedure for polluted sites, the application of common analytical volatilization models may lead to an overestimation of vapour emissions. The use of site-specific parameters of soil and specifically measured physico-chemical parameters of contaminants are sometimes not able to mitigate this overestimation. The present note describes the results of measurements of mercury vapour emission from soil at an actual contaminated italian site. Several surveys were carried out over one year, in order to take into account possible seasonal variations. Both the vapour flux from soil and the concentration in open air were measured by means of open dynamic flux chambers (FC) and through direct measurements in outdoor air, respectively. For a given investigation point, the predictions of volatilization models were compared with direct measurements. The actual emissions were found to be significantly lower than those estimated by the models, seasonal variation did not cause high differences among measured concentration and flux values. The use of an experimentally determined soil-water partition coefficient helped in obtaining a less unrealistic output of the model and information about the effect of using default parameters can be retrieved by combining results from both FC and direct measurements in outdoor air.