Mercury Vapour Measurements
Measurement of mercury in the environment is of growing importance due to its high toxicity. Recent European legislation requires the UK Government to monitor the mercury content of ambient air - NPL is responsible for carrying out these measurements at 13 locations around the UK as part of the UK Heavy Metals Monitoring Network.
Vapour phase mercury is sampled, by use of a pump, onto adsorption tubes (see diagram). The air is passed through a filter to remove particulates before entering the tube, where it is adsorbed onto gold-coated silica. The tubes are analysed at NPL using an atomic fluorescence spectrometer and the results used to determine the average concentration of mercury in ambient air at each of the monitoring locations.
NPL is also actively engaged in mercury vapour research areas such as:
- The development of novel calibration methodologies for mercury vapour measurement.
- The investigation of procedures to decrease the uncertainty of ambient mercury vapour measurements.
- Studying effects of cross interferences and adsorption tube degradation on ambient mercury vapour measurements.
In addition, NPL plays a leading role in the European working group CEN TC264 WG25 which is currently developing a standard method for mercury vapour measurement in ambient air.