The accurate measurement of the metals content of ambient air is increasingly important as the potential toxicological effects of a number of metal species are becoming better established. Additionally, UK and EU legislation specifies statutory legal limits for the concentrations of metal compounds in ambient air.
European directives require the reporting of four metals in the PM10 (particulates which are 10 micrometers or less) fraction of ambient air: Nickel (Ni), Arsenic (As), Cadmium (Cd) and Lead (Pb). In addition, NPL measures ambient levels of Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Copper (Cu), Zinc (Zn) and Selenium (Se). Accurate measurement of these elements is of importance due to their toxicological effects and legislative requirements; they are also routinely measured within national air quality networks.
NPL oversees sampling operations and performs all analyses in-house.
NPL manages the UK Heavy Metals Monitoring Network on behalf of the Environment Agency (EA) and the Department for Environment, Food and Rural Affairs (Defra). The Network comprises 25 sites located at rural, urban and industrial locations throughout the UK.
Ambient air samples are collected by sampling PM10 onto cellulose filters using Partisol samplers at a nominal flow rate of 1 m3/hour.
NPL has developed robust, UKAS accredited procedures for the determination of the metals listed above in the particulate phase by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Sampled filters are microwave-digested in a matrix of concentrated nitric acid and hydrogen peroxide prior to analysis.
Publications arising from Highlights of our recent research on the Metals Network include:
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