Traceable calibration methods for oxidised mercury

Because of its toxicity, regulations on the use and exposure limits for mercury are becoming even more stringent. For health and safety purposes, as well as for enforcement of regulations accurate measurements and hence calibrations are required. In recent years research has led to traceable calibration of elementary mercury (Hg0) concentrations, including the primary standard currently operational at VSL. However, mercury also occurs in oxidised forms (Hg2+) that are reactive and can be transformed into organic Hg species such as methylmercury (MeHg), which is very toxic and most prone to bioaccumulation in aquatic systems (Figure 1). Half of atmospheric mercury emissions are of natural origin whilst the rest are of anthropogenic sources, primarily from fossil fuel burning and other high-temperature industrial processes, such as cement clinker production, waste incineration, ore roasting and steel production.