Page 250 - Fundamentals of Air Pollution

Transmissometer Long path extinction Measurement over medium Calibration problems; single Areas experiencing periodic
coefficient (b M) view path (10-25 km); wavelength; equivalent to mixed general haze,
measures total extinction, point measurement in medium to short viewing
scattering and absorption; areas with long view distance areas with
unaffected by clouds, paths (50-100 km); significant absorption
night limited applications to (&*)
date still under
development
Photography Visual quality, plume blight, Related to perception of Sensitive to lighting Complement to human
color, contrast (limited) visual quality; conditions; degradation observation, instrumental
documentation of vista in storage; contrast methods; areas with
conditions measurement from film frequent plume blight,
subject to significant discoloration
errors
Particle samplers Particles Permit evaluation of causes Not always relatable to Complement to visibility
of impairment visual air quality; point measurements
measurement
Hi vol. TSP Large data base, amenable Does not separate sizes; Not useful for visibility sites
to chemical analysis; sampling artifacts for
coarse particle analysis nitrate, sulfate; not
automated
Cascade impactor Size-segregated particles Detailed chemical, size Particle bounce, wall losses; Detailed studies of
(more than two stages) evaluation labor intensive scattering by particles
<2ptm
Dichotomous and fine Fine particles (<2.5 /Am) Size cut enhances Some large-particle Complement to visibility
particle samplers (several coarse particles (2.5-15 resolution, optically penetration; 24 hr or measurement, source
fundamentally different /u,m) inhalable particles important aerosol longer sample required in assessment for general
types) (0-15 /am) analysis, low artifact clean areas for mass haze, ground-level
potential, particle bounce; measurement; automated plumes
amenable to automated version relatively
compositional analysis; untested in remote
automated versions locations
available; large networks
under development
Source: U.S. Environmental Protection Agency, "Protecting Visibility," EPA 450/5-79-008. Office of Air Quality and Standards, Research
Triangle Park, NC, 1979.