UK metals network

Accurate measurement of metals

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.

UKAS Accredited Analysis

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

Publications arising from Highlights of our recent research on the Metals Network include:

• Temperature dependence of Hg vapour mass concentration at saturation in air: new SI traceable results between 15 and 30 °C. Quétel, C R; Zampella, M; Brown, R J C
  Trends in Analytical Chemistry, 2016, 85B, 81–88.
• Determination of beryllium in ambient air quality filter samples. Sharon L Goddard, Richard J C Brown, Baljit K Ghatora (Kingston University). Atmospheric Environment, 2016, 147, 320-329
• Ten years of mercury measurement at urban and industrial air quality monitoring stations in the UK. Richard J C Brown, Sharon L Goddard, David M Butterfield, Andrew S Brown, Chris Robins, Chantal L Mustoe, Elizabeth A McGhee: Atmospheric Environment, 2015, 109, 1-8
• UK concentrations of chromium and chromium (VI), measured as water soluble chromium, in PM₁₀. Richard J C Brown, Sivan Van Aswegen, William R Webb, Sharon L Goddard: Atmospheric Environment, 2014, 99, 385-391.
• Interlaboratory comparison exercise for the determination of As, Cd, Ni and Pb in PM₁₀ in Europe
  Gerboles, M; Brown, R J C; et al
  Atmospheric Environment, 2011, 45, 3488-3499
• Comparison of estimated annual emissions and measured annual ambient concentrations of metals in the United Kingdom 1980-2007
  Brown, R J C
  Journal of Environmental Monitoring, 2010, 12, 665-671
• Twenty-five years of nationwide ambient metals measurement in the United Kingdom: concentration levels and trends
  Brown, R J C, Yardley, R E, Muhunthan, D, Butterfield, D M, Williams, M, Woods, P T, Brown, A S, Goddard S L
  Environmental Monitoring and Assessment, 2008, 142, (1-3), 127-140