sampling the environment Flashcards
4 particulate sampling techniques
Filters
impactors
dry cyclones
wetted wall cyclones
3 gas sampling techniques
absorption
adsorption
Condensation
4 key air sampling questions
Why are you sampling
what are you sampling
where are you sampling
how long are you sampling for
7 main analytes
aural
bio
chem
magnetic
optical
radiological
thermal
define an analyte
a substance who’s chemical constituents are being identified and measured
what is the prerequisite for detection of a stimulus?
must be present in sufficient CONCENTRATION or INTENSITY so it can be DETECTED and DIFFERENTIATED from the environment
4 routes of entry to the human body
respiratory
percutaneous
ocular
ingestions
2 features of the air we breathe
Highly diverse
Ambient aerosol
Define highly diverse
already contains bacteria, viruses and toxins
infections are from an aerosol route
Define ambient aresol
contains naturally occurring aerosolised particles
physically identical to threat particles
present at continually fluctuating levels
6 particulate sampling techniques
filtration
impingement/impaction
sedimentation
precipitation
thermal
electrostatic
4 stages of air sampling
pre-separator
filter/collection media
airflow controller
pump
Features of PM10 high volume air sampler
Flow rate between 1-1.7 m^3/min
size selective inlet allow for particles of pre determined range to be captured on a quartz filter (usually less than 10 microns and filter paper determines the minimum size)
filter weighted before and after use to determine the mass of particulates caught
controlled by mass flow controller or volumetric flow controller
types of filter (8)
glass fibre
quartz fibre
borosilicate fibre
cellulose and mixed cellulose esters (MCE)
PTFE PM 2.5
Glass fibre tape
Andersen impactor filters
Polycarbonate filter
Concentration calculation
concentration = mass of pollutant / volume of air
gravimetric concentration formula
SP = (Wf-Wi)/V(T) x 10^6
SP = mass concentration of suspended particulate
Wf = final weight of filter
Wi = initial volume of filter
V(T) = total volume of air sampled
10^6 = conversion of g to ug
Define aerodynamic diameter of a particle
a sphere, whose density is 1 g cm^-3 which settles in still air at the same velocity as the particle in question
Define Mass Median Aerodynamic Diameter
is defined as the diameter at which 50% of the particles by mass are larger and 50% are smaller.
Define Geometric Standard Deviation (GSD)
is a measure of the spread of an aerodynamic particle
size distribution. Typically calculated as follows:
GSD = (d84 /d16)^1/2
where d84 and d16 represent the diameters at which 84% and 16% of the aerosol mass are contained, respectively, in diameters less than these diameters.
Types of air sampler
Cyclone
3 piece cassette
swirling aerosol collector
AGI 30
Slit sampler
Andersen sampler
