::Technical
Services - Ambient Air Monitoring
We
provide environmental monitoring that is simple, accurate, unobtrusive,
flexible and very economical. Our specialty is air pollution
and meteorological measurements with compact equipment designed,
for saturation monitoring studies. We make accurate measurements
for typically regulated air pollutants down to very low detection
limits using a self-contained, unobtrusive measurement package
mounted on existing utility poles or small tripods. We can also
provide on-site meteorology measurements (air temperature, relative
humidity), and work with local meteorological data providers
(wind speed and direction, atmospheric pressure) to give you
a snapshot of weather conditions during sampling. We then interpret
sampling results using met data, careful sampler placement, local
topological maps and air pollution modeling to give you an reliable
picture of air pollution impacts at time of sampling, as well
as a analysis of expected impacts.
We use Ogawa passive samplers, which have two screens (1,
2) forming a well defined diffusion path to a chemical absorbent
pad (3) held in a robust capsule (4) that is easily cleaned,
but can be quickly reloaded in a normal indoor environment.
Duplicate samples or two gases can be measured with each sampler.
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Although
these devices are not equivalent U.S. ambient air sampling
methods, they were developed and have been used by USEPA for
saturation monitoring in many urban settings in the US and
abroad. They provide extraordinarily accurate and precise data
for a range of gases (SO2, NO, NO2,
(NOx by difference), and O3).
We also use compact, battery-operated pump samplers for PM-10,
2.5 or TSP or bag samples for other gases (e.g., CO), yielding
time-integrated samples for periods as short as 8 hours or
as long as two weeks. Specialty gases are available as well.
We can execute pre- and post-construction monitoring, impact
studies, or establish long-term, routine monitoring programs
using your on-site personnel. The World Bank and other institutions
have accepted these monitoring methods to satisfy lending requirements.
Side
view of passive sampler in clip-on holder.
Two Samplers may be housed in an inverted cap rain screen
for outdoor use.
© Ogawa & Co. Inc., USA.
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::Passive
Sampler Operation
Ambient
Air Sampling is frequently performed using electro-optical
or gas chromatographic monitoring devices that provide continuous
pollutant measurements. This requires delicate and expensive
equipment maintained by highly trained technicians using expensive
and cumbersome calibration equipment and gases. For many purposes,
time-averaged 24-hour average (or longer) sampling techniques
suffice. Passive diffusion monitoring techniques can measure
24-hour average pollutant concentrations down to low part per
billion levels for many gases. Sample rate is controlled by
diffusion across the sampler, so there are no pumps or moving
parts, other than a sealed storage canister. This allows us
to collect extremely low cost but accurate samples in comparison
to electro-optical samplers. Samplers can also be worn unobtrusively
for personal monitoring studies or used indoors.
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::Particulate
Sampling
For Total, PM-10 or PM-2.5
Particulate
for PM10, PM2.5 or Total Particulate is collected onto 47mm filters.
These filters are gravimetrically analyzed for mass concentration.
They can also be analyzed by XRF, PIXE, NAA or IC if elemental
or ion analysis is also required. Stacked, treated filters may
sometimes be appropriate for simultaneous gas sampling. We sample
at 5 LPM using battery-operated, flow-controlled pumps with inertial
impactor heads to provide size selective particulate samples.
This compact and portable can be installed in virtually any accessible
location because there are no power supply requirements beyond
battery operation (solar backup available). The equipment is
quiet and suitable for unobtrusive indoor sampling.
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