{'fraction_non_alphanumeric': 0.010869565217391304, 'fraction_numerical': 0.0, 'mean_word_length': 5.214723926380368, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 1, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Development of a Reference Standard for Particulate Matter Mass in Ambient Air

Particulate matter (PM) in ambient air is composed of many chemical species of varying vapor pressures. A direct mass measurement of PM mass on filters is the basis of regulatory PM reference methods. The loss of semi-volatile PM mass collected on filters and filter sampling artifacts can produce nonquantifiable biases in reference method measurements depending on the thermodynamic history of the filter; therefore, a reference method cannot be considered a scientific reference standard. A new technique is introduced which has the potential to overcome the difficulties inherent in PM mass measurement and holds the promise of the measurement of PM mass as it exists in ambient air at ambient temperature. While comprehensive laboratory and field studies of the instrument and its components are needed to fully characterize the system, preliminary data have been obtained to provide a basic proof of concept for the technique.