What we do ...

The Atmospheric Chemistry Group advances, applies, and disseminates fundamental chemical and isotopic metrology, standards, and data relevant to atmospheric measurements. Our fundamental efforts support national and international atmospheric measurement programs so that decisions made by industry and government on atmospheric issues may be based on a sound scientific basis. Uncertainties in atmospheric measurement data, due to limitations in measurement techniques and methods, quality assurance, and national/international traceability mechanisms, pose the technical challenges that we help to address.

A primary focus is on the carbon metrology of airborne particulate matter (PM), especially that size fraction (PM2.5) linked with human respiratory and pulmonary health effects. Airborne PM is highly complex and variable in nature, and the specific chemical-morphological factors responsible for the health effects are unknown. For these reasons, PM is the only recognized atmospheric pollutant that lacks a definitive chemical identity. This situation has led to the development of a large number of measurement techniques for PM analytes, with intercomparisons generally exhibiting poor reproducibility across techniques and methods — mainly because of a lack of effective standardization mechanisms. Existing PM standard materials are not representative of many modern PM samples, and are also lacking in certified values for many carbonaceous analytes. We are developing new PM standard materials, and augmenting existing ones, with value assignments for carbonaceous fractions relevant to the PM measurement communities.

Another activity involves the advancement of metrology to help measure the sources of hydrocarbon precursors to urban and regional ozone episodes, and to measure specific chemical contaminants such as benzene and other volatile organic compounds (VOCs). The apportionment of natural sources of VOCs (e.g., vegetative emissions) versus anthropogenic sources (e.g., industrial emissions) based on chemical and isotopic measurements is crucial for the formulation of effective control policies. Both the Environmental Protection Agency (EPA) and the American Petroleum Institute, a professional organization serving the interests of the petroleum and motor vehicle industries, have supported this work.

Many other activities are described in this Website. A few projects relate outside of atmospheric chemistry — these are special assignments within the NIST mission that take advantage of our unique mix of technical expertise. Please feel free to peruse through these pages and learn more about us.