David M. Butterfield

Ambient air particulate matter PM10 and PM2.5: developments in European measurement methods and legislation.

The measure of airborne particulate matter PM10 is effectively defined for European regulatory purposes by the European Committee for Standardisation (CEN) standard EN 12341:1998 – a gravimetric filter-based method. However, compared with the reference methods written for other pollutants, specifically to address the needs of the Air Quality Directives, EN 12341 falls short in areas such as ongoing Quality Assurance and Quality Control. Also, scientific knowledge about PM has moved on considerably since 1998, so that we now realize that implementations of variations allowed within EN 12341:1998 can lead to substantial differences in results obtained. These issues were partially addressed within the CEN standard for PM2.5, EN 14907:2005, which, for example, included tighter control of the handling of sampled filters to reduce losses of semi-volatile material. CEN Technical Committee 264 Working Group 15 is currently revising EN 12341, and has the opportunity to improve the reference method further, for example by tighter specification of the filter material, or by changing the specification for the humidity at which the filters are brought to equilibrium. Any changes must, however, be considered in the context of the regulatory implications of the standard, so that improvements in scientific quality must be balanced with the effect of a step change in reference method, and with associated costs. The paper outlines the present position of the EN 12341 revision and recent changes to EU Air Quality legislation.

State of UK emissions monitoring of stacks and flues: an evaluation of proficiency testing data for SO2, NO and particulates

We report an examination of the UK stack testing industry’s proficiency for monitoring industrial emissions of SO2, NO and particulates from 2000 to 2011. Data were taken from three proficiency testing schemes run by the National Physical Laboratory (NPL), UK; Calibration Gas Scheme (gas bottle certified reference materials), Gas Measurement Scheme (using a Stack Simulator Facility to test the entire measurement system) and Particulate Scheme (foil shims and salt solutions—i.e., filter and probe washing simulants). In each round of each scheme, participants’ deviations from assigned value were normalised to an allowable deviation based on the required uncertainty for stack emission measurements stipulated in the European Union’s Industrial Emissions Directive. This normalisation produced a z-score and limits were set to define satisfactory, warning and unsatisfactory participant performance. As a function of time, it was found that across all schemes, the number of unsatisfactory/outlier scores decreased, evidencing an overall improvement in industry proficiency. With regard to the gas schemes, it was found that the industry had a poorer proficiency for SO2 than NO and that there was a distribution bias toward negative scores in the Gas Measurement scheme consistent with SO2 sample losses in drying units. It was evident that this industry bias was insufficient to force the vast majority of the industry outside of the satisfactory z-score limits; however, it was noted that this issue should be carefully monitored in the future.