Methods for the analysis of major components of particulate matter and metals

The main aim of this work package is to establish traceable validated methods for the analysis of major components of particulate matter such as elemental and organic carbon (EC/OC), total carbon, anions and cations, together with major metals (arsenic, cadmium, mercury, nickel), in order to meet the data quality objectives of current regulation within Directive 2008/50/EC (on ambient air quality) and 2004/107/EC (on metals and polycyclic aromatic hydrocarbons). The supplementary aims are to complement these methods with additional analyses for organic carbon that provide additional scientific value with information relating to the sources of the material, and to develop an alternative to the existing reference method for metals.

Monitoring of the major components of particulate matter and metals is dependent on the traceability of the measurements, ensuring stability over time so that trends can be evaluated, comparability between locations so that spatial variation can be properly assessed, regardless of the measurement method used, and allowing uncertainties to be rigorously determined and kept as low as possible. However, there are currently three areas where full traceability is not ensured, and where the currently used methods are not always comparable to other monitoring systems (such as EMEP), are the measurements of OC and EC in Task 2.1, ions in Task 2.2, and metals in PM in Task 2.3. The Air Quality Directive’s data quality objective for metals measurements, for example, is 40 %, and the aim is for measurements to achieve 30 %. This is particularly important for the challenge of defining what is meant by OC in the air quality context, which will be addressed by spectroscopic techniques in Task 2.2, and to metals analysis in Task 2.3, where the existing reference ICPMS analysis methods will be complemented by XRF methods. The analytical capabilities developed in Tasks 2.1 and 2.2 will be used to characterise the PM developed in WP1.

The samples used for the refinement of the analytical techniques within this work package will come from a variety of sources. Primarily they will be obtained from at least two national air quality monitoring networks, which typically use only part of the sampled filter for their own analysis covering at least four sites at different seasons of the year. This will ensure that the samples are representative of real world conditions, while also providing supplementary data from the analyses carried out by the network operators.


Task 2.1: Analysis of EC/OC and total carbon in PM

The 3 aims of this task are, firstly, to develop EC/OC measurements, that allow regulatory objectives to be met using reference methods, and ensure traceability with reduce uncertainties; secondly, for the related quantity Total Carbon (TC, which is the sum of EC and OC), to improve calibration techniques so that uncertainties of TC are lower than those for EC and OC individually; and thirdly, to carry out supplementary investigations that will help end users make better use of these measurements, in the areas of speciation of organic compounds and in the characterisation of wood smoke. Target uncertainties for TC will be 6 %, compared to typical current values of 10 %.

Measurements of the OC and EC content of particulate samples collected on quartz filters are very commonly made and feature in legislation such as the European Ambient Air Quality Directive and a standardised method is soon to be published as EN 16909. The metric TC is, in principle, simply the sum of the OC and EC components. However, the standard pays relatively little attention to the accuracy of the TC measurement, which is the quantity directly measured. Instead EN 16909 focusses on the specific thermal-optical procedures used to split the TC result into its two components. The black carbon metric (a measure of soot-like material determined by its optical absorption) is related to the elemental carbon metric, as they should have similar concentrations in μg/m3. There is a separate EMPIR project addressing the metrology of black carbon 16ENV02. There will be informal links between the two projects, which contain several partners in common.

This task will bring NMI capabilities to the measurements through NMI participation in comparisons. In addition, PTB and BAM, NTUA, METAS and UPO will measure the carbonaceous chemical species and related mass deposition in size-fractionated (e.g. by a cascade impactor) PM samples using XAFS. Results will be compared with those from standard EC/OC techniques so that sources of variation in the standard techniques can be identified.


Task 2.2: Analysis of anions and cations in PM

The aim of this task is to meet regulatory objectives using reference methods for the anions sulphate, nitrate and chloride, and the cations sodium, potassium, calcium, magnesium and ammonium, as required by legislation, to ensure traceability to SI by the involvement of NMIs, and to determine and reduce uncertainties from the current value of around 30 % to around 20 % with independent validation.

Anions and cations are important metrics to understand secondary inorganic aerosol formation, and to measure primary ionic PM such as sea salt. The accurate measurement of such natural sources is particularly important since legislation allows them to be subtracted from a Member State’s PM concentrations. Standard methods in this area, based on ion chromatography, and developed within CEN TC 264 WG 34, are close to being published, but full SI traceability is needed.

The task will concentrate on the development of facilities at NMIs, and bringing these capabilities to end users through participation in comparisons.


Task 2.3: Analysis of metals in PM

The aims of this task are to meet regulatory objectives for reference methods the analysis of metals in PM, specifically ICP-MS, and to ensure traceability and reduce uncertainties from the current value of around 40 % to around 25 %. In addition, to investigate the non-reference method XRF, in order to provide independent chemical and physical traceability chains, and to extend the range of metals analysed beyond those required for regulation.

The presence of heavy metals in ambient PM can have a number of toxic effects. Generally, the smaller the size and greater the solubility of the PM, the higher the toxicity through mechanisms of oxidative stress and inflammation, prompted by the redox chemistry of these heavy metals. Exposure to heavy metals in the air is capable of causing a variety of human health effects, ranging from cardiovascular and pulmonary inflammation to cancer and damage of vital organs. Deposition of metals causes contamination of crops for human and animal consumption, for example leafy vegetables are particularly vulnerable to arsenic, lead and mercury. Contemporary research into air pollution is revealing that the metallic components of PM are contributing significantly to adverse health effects, even at the low concentrations found in ambient air. Further details of health effects are given in the 2013 WHO REVIHAAP report: “Review of evidence on health aspects of air pollution”.