Evaluating Airborne Condensable Particulate Matter Measurement Methods in Typical Stationary Sources in China

The dry impinger method, the indirect dilution method, and the direct dilution method can be used to measure the condensable particulate matter (CPM) emissions. We tested these methods in determining the CPM emissions from typical stationary sources in China and found that the CPM concentrations measured by the dry impinger method are much higher than those measured by the two dilution methods regardless of the type of stationary source. The soluble gases (e.g., SO₂, HCl, and NH₃) partially absorbed by the impinger solutions are the main reason for the overestimation of the CPM concentrations. This is supported by detecting more water-soluble ions (e.g., SO₄^2-, Cl^-, and NH₄⁺) from the CPM collected using the dry impinger method. The positive biases of the CPM concentration and its water-soluble ions collected by the dry impinger method are larger under the conditions with high concentrations of soluble gases such as at the flue gas desulfurization inlet in coal-fired power plants. Comparing to the direct dilution method, the indirect dilution method can better capture the rapid dilution, cooling, and condensation of condensable gas precursors in the presence of filterable particulate matter and is recommended as the appropriate method for the CPM measurement in stationary sources.