FIGURE 4-1 Ammonia concentrations (averaged over a 68-m path) measured near a dairy wastewater lagoon. Method used was an ultraviolet differential optical absorption spectroscopy technique with a detectability limit of 1 ppb and a time resolution of 0.6 second.

SOURCE: Reprinted from Mount et al., 2002, with permission from Elsevier Science.

effects, the time course of concentrations inhaled is important; for PM, health effects also depend on the physical, chemical, and biological characteristics of the particulate material. Concentrations of odorants are important, but measurement and understanding of their health effects are still in their infancy.

CALIBRATION, SAMPLING, AND CONCENTRATION MEASUREMENTS

The substances of interest in this report run the gamut from the most accurately measured atmospheric trace gases, with a long history of precise calibra-



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