【国外标准】 Standard Test Method for Determination of Gaseous and Particulate Polycyclic Aromatic Hydrocarbons in Ambient Air (Collection on Sorbent-Backed Filters with Gas Chromatographic/Mass Spectrometric Analysis)

5.1 Polycyclic aromatic hydrocarbons (PAH) as defined by this test method are compounds made up of two or more fused aromatic rings.5.2 Several PAH are considered to be probable human carcinogens.5.3 PAH are emitted in the atmosphere primarily through wood or fossil fuel combustion.5.4 Two- and three-ring PAH are typically present in urban air at concentrations ranging from 10 to several hundred nanograms per cubic metre (ng/m3); those with four or more rings are usually found at concentrations of a few ng/m3 or lower.5.5 PAH span a broad spectrum of vapor pressures (for example, from 1.1 × 10–2 kPa for naphthalene to 2 × 10–13 kPa for coronene at 25 °C). Table 1 lists some PAH that are frequently found in ambient air. Those with vapor pressures above about 10–8 kPa will be present in the ambient air substantially distributed between the gas and particulate phases. This test method will permit the collection of both phases. However, particulate-phase PAH will tend to be lost from the particulate filter during sampling due to desorption and volatilization.(A) Many of these compounds sublime.5.5.1 The distribution between phases depends on ambient temperature, humidity, types and concentrations of PAH and particulate matter, and residence time in the air. PAH, especially those having vapor pressures above 10–8 kPa, may vaporize from particulate filters during sampling. Consequently, a back-up vapor trap must be used for efficient sampling.5.6 Separate analyses of the filter and vapor trap will not reflect the original atmospheric phase distributions and should be discouraged.1.1 This test method2 specifies sampling, cleanup, and analysis procedures for the determination of polycyclic aromatic hydrocarbons (PAH) in ambient air.1.2 This test method is designed to collect both gas-phase and particulate-phase PAH and to determine them collectively.1.3 This test method is a high-volume sampling (100 to 250 L/min) method capable of detecting PAH at sub-nanograms per cubic metre (ng/m3) concentrations with sampling volumes up to 350 m3 of air.1.4 This test method has been validated for sampling periods up to 24 h.1.5 Precision and bias under normal conditions can be expected to be ±35 to 50 %.1.6 This test method describes a sampling and analysis procedure for PAH that involves collection from air on a combination fine-particle filter and sorbent trap and subsequent analysis by gas chromatography/mass spectrometry (GC/MS).1.7 The range of this test method is approximately 0.05 to 1000 ng/m3 of air sampled.1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. See also Section 8 for additional safety precautions.1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.