AIRBORNE
POLLUTANTS - CURRENT & FUTURE ISSUES IN ENVIRONMENTAL MONITORING
SYNOPSIS AND
INTRODUCTION
With the ever
increasing sophistication in the technology and therefore cost of
environmental monitoring putting it out of reach, the need for
developing more cost effective and acceptable methods has to become an
international necessity if serious attempts are to be made to improve
health and the environment.
This paper examines
current trends and offers a cheaper alternative following development
and ongoing research monitoring.
With production
monitoring taking place at over 50 monitor stations Southern Africa wide
for periods up to three years, the monitoring technology is presented as
a working model.
THE AIMS OF MONITORING
Without a means of monitoring the
pollutant levels we cannot consider whether the condition of the
atmosphere or environ at any position is improving or getting worse. We
cannot ascertain with any degree of certainty if any place is starting
to become a health hazard before actually waiting for the health
deterioration patterns to set in without a means of monitoring the area.
It is perhaps an indictment of industry and governments that
irreversible damage to the health of a residential population or workers
is regarded as a time to consider " doing something about the
problem" or even only of an indication that "there may be a
problem".
We see the deterioration of urban,
industrial and residential areas to a point where the persons working
and living in the areas have to start dying of pollutant induced
cancers, chronic lung diseases and other consumptive causes before
actions are taken.
We have fortunately seen a great
improvement to direct working conditions with the present and draft
legislation covering the health of workers. Occupational hygiene is
becoming an integral aspect of every mine, ship, industry and to some
extent even within the agricultural industry. The gap between conditions
within the working place and the residential area now has to be
concentrated on to a degree never considered before and even if this
aspect has not been totally legislated or is not being adequately
policed, we now have to consider aspects of pollution very carefully if
we are to be accepted as suppliers to the developed nations or even as
recipients in a trade pact.
- In the near future mines will have
to prove that they
are monitoring their emission levels and are
doing
this to acceptable standards and that they are reducing
emissions in a structured systematic way.
- The science of determining the
effect or impact of
pollutants on the environment as well as the
health
of people and animals will similarly have to improve.
- In the same way, industry whether
local or aimed at
some export market will have to unify standards
and
monitor their emissions satisfactorily.
- Farming methods will also have to be
modified to limit
the creation of dust, the liberation of pesticides
where
these are used and to limit veld-burning operations.
- Finally, monitoring must be as
simple as possible, the
equipment cost should not be too expensive
and the
cost of running a programme as low as possible. In the
South
African or indeed the African context or other
developing areas it
is vital that as many persons as
possible can be trained to service
and run a monitoring
programme. A requirement for programmes to be
run by
scientists only is just not feasible.
MONITORING METHODS
As this paper outlines concepts
associated with airborne pollutants and concentrated on particulate
forms of airborne pollutants, we will not consider gasses although some
forms of fumes and vapour are considered in some detail, as these can
result in chemical reactions within the atmosphere, which manifest as
particulates.
With the above in mind it is important
to consider what has to be achieved before deciding on the method to be
used to carry out the monitoring. Integral to this thinking, the
following questions should be asked when embarking on a sampling
programme:
-
How does the pollutant cause a
problem?
-
What is the problem associated with
this pollutant?
-
If the pollutant settle out will it
be easier and more
representative to measure the fall-out settlement
or
should the airborne load be determined?
-
If the airborne load is determined,
can we accurately
determine where and under what conditions it will
settle out or precipitate or even whom it will affect?
-
Can a single means of monitoring be
used or is there
a necessity to employ a multiplicity of methods to
determine the pollutant load or concentration?
From the above questions it should then
be possible to determine if capture of the particulate must be achieved
within the airflow or to wait for the particulate to settle out before
capturing. To illustrate this important point further let us ask a
further question:
v Will the captured particulate
fall-out within the area where monitoring is required and thus cause a
problem or will it cause a problem while in suspension?
Generally the answer to this question
will tend to dictate how the particulate must be captured, enabling the
best method to be selected.
AIRBORNE
PARTICULATE CAPTURE
CYCLONIC
SEPARATION
As the amount of particulate to be
captured is very small and the particulate size is also likely to be
limited, it is unlikely that any form of cyclonic separation will
either be size selective or will be efficient enough to be of any
practical use.
Purpose designed micro-cyclones could
however be considered to establish particulate size distribution or to
guarantee that size selection takes place.
An example of the use of a
micro-cyclone is within the personnel gravimetric sampling train used
to establish the extent of respirable dust ingestion on a person
sampled for a period of time. In this example, the cyclone is used as
a method of removing any particulate of a size in excess of that
constituting respirable dust (+ about 8µm).
TOTAL
SPECTRUM DUST CAPTURE - GRAVIMETRIC SAMPLING
As with the above arrangement given
as an example, it is possible to capture the total spectrum of
airborne dust with the standard gravimetric dust sampling train
providing that precautions are taken to negate the possibility of wind
blown excessively sized particulate entering the sample - grits or
sand. With this type of arrangement it is also important that the
capture filter is permitted to catch the sample as evenly and
uniformly as possible to prevent increases in filtering velocities or
decreases in the sampling flow rate.
The illustrations - Figure A -
indicate the requirement of the sampling trains for both respirable as
well as the total spectrum dust capture rigs using standard
gravimetric dust sampling equipment available on a mine with added
precautionary requirements.
PM10
PARTICULATE MONITORING
The PM10 or sub 10µm particulate
capture sampling has been in general use for some time, constituting a
means of sampling potentially respirable particulates on a longer term
basis. The stipulation of monitoring sub 10µm particulate superseded
the original primary and secondary National Air Quality Standards (NAAQS)
for particulate matter (PM) which were promulgated in 1971 (EPA). The
original primary standards for PM, measured as total suspended
particulates or TSP, were 260-microgram µg/m3. The 24-hour average
was not to be exceeded more than once per year with an annual
geometric mean of 75µm/m3. The NAAQS was revised in 1987 with the
following criteria changed:
- TSP was replaced as an indicator
that included
particles with an aerodynamic diameter of less
than
10µm - PM10.
- The 24 hour primary TSP standard
was replaced
with a 24 hour PM10 standard of 150µm/m3.
- The annual primary TSP standard
was replaced
with an annual average PM10 standard of 50µm/m3.
- The secondary TSP standard was
replaced with
24 hour and annual PM10 standards identical in
all
respects to the primary standards.
Analysis from monitoring in the
United States as well as locally indicates that fugitive dust
constitutes about 90% of the PM10 emissions but as most monitoring is
undertaken by industry there is some loading of the fugitive dust
fraction due to the higher incidence of dust creation from process
requirements and materials or ore handling. Only a very small
percentage of this particulate manifests as very fine particulate,
which led to the requirement for PM2.5 monitoring for fume and smoke
particulate capture.
The Environmental Protection Agency
(EPA) revised the primary health based PM standards by adding a new
annual PM 2.5 standard set at 15µg/m3 and a new 24 hour PM 2.5
standard set at 65µg/m3 (July 1997). The PM10 standards were not
changed.
PM 2.5
PARTICULATE MONITORING
As already implied above, there was a
necessity to scrutinise specific health issues of respirable dusts and
fume and the PM 2.5 system was devised.
Of concern in the establishment of
both PM 10 and PM 2.5 programmes, especially the latter, there is a
degree of doubt as to the accuracy of the available equipment,
equating the means of air ingestion physiologically with that of the
monitor unit.
Much research went into building
pumps and monitoring rigs for PM 10 including aspiration rates, while
the 2.5 µm filter was achieved using an 0.45µm membrane filter in
addition to the 8.0 µm filter capturing the <10µm >8
particulate. The primary induced air was selected to contain only
10µm particulate with approved design impinger or cyclones.
Monitoring using the PM 10 and PM 2.5
methods utilises 24 hour sampling on each third consecutive day in
order to achieve a form of statistical acceptance. The labour
intensive nature of undertaking this operation together with the fact
that continuous monitoring is not undertaken as well as the high cost
factor leads to an unwieldy expensive system.
At least one South African
manufactured unit is available to compete against imported models.
FALL-OUT PARTICULATE
MONITORING
The monitoring of fall-out dust
establishes the degree to which airborne particulate is precipitated out
and then has an opportunity of exposure to human beings, animals or
plant life. This monitoring further establishes a means of studying the
movement of most sizes of dust including particulate of a size exceeding
10µm, which constitutes nuisance fugitive dust. This larger dust
particulate poses the greatest local area influence.
Fall-out monitoring also has the
advantage of offering a continuous means of monitoring, negating the
need to estimate how representative the results are.
For a greatly decreased cost, multiple
position monitoring can take place, forming a good network of monitor
station in preference to only one or two.
Full direction monitoring indicates
from which direction the emission is imported and use of multiple units
can establish patterns of import and export dust, which is extremely
useful in establishing dust sources. Continuous monitoring offers a far
greater chance of detecting very low pollutant concentrations.
With the origins of monitoring having
been established with the American Standard Test method (ASTM 1739D)
there have been several developments in the field and improvements to
the original open bucket collection methodology. At least two production
units employing the ASTM 1739 method are available locally with both
offering merits and demerits.
The system offers an opportunity of
sampling airborne precipitant particulate as well as soluble airborne
particulate prevalent at the coast and offers with minimal effort, the
means of indicating both values from each sample.
The system also offers the potential of
biological monitoring.
The system is acceptable in terms of
ISO 14001 standards.
CONTINUOUS
PARTICULATE LASER COUNT MONITORING
With the continuous developments
occurring with laser scan technology, several portable instruments offer
instantaneous readings of particulate concentration. Once a means of
recording the values has been added, the resulting data is of use in
establishing area dust concentrations. While such instruments can record
much of the information that will enable a good monitoring programme to
be run, they only offer a grab sample at best before being transported
to the next sampling position where further samples need to be taken. As
the instrumentation is expensive, simultaneous multiple sampling is not
achieved, leading to doubt about the representivity of the results.
Monitoring positions and the equipment
needs to be secure to guard against loss of expensive equipment, rending
the method even more costly.
Most units are humidity sensitive,
which could possibly limit the use under certain conditions.
Chemical and physical quantitative
analysis of dust is not possible with this method.
FALL-OUT MONITORING -
PARTICULATE DUST
DustWatch®
MONITORING SYSTEM
The DustWatch monitor
units form an inexpensive means of monitoring fall-out dust with a
minimal maintenance requirement, low sample loss rate, no supervision
requirements and all-wind velocity particulate classification to
prevent grits and sand capture at high wind velocities. The
directionality of sampling encompasses a narrow angle offering
increased direction accuracy. As the sample represents a continuous
sample taken over an extended time period, the collected material can
be subjected to qualitative and quantitative chemical and physical
analysis in addition to microscopic organics recognition scanning.
The unit is not
affected by rainfall and samples are not lost under abnormal weather
conditions.
The units offer
fall-out monitoring of either two or four incoming prevailing wind
directions simultaneously, offering many monitoring options:
FIGURE
1 Import ambient
dust from upwind of a monitoring site together with a corresponding
export dust towards the same area.
FIGURE
1 Four bucket
units can thus indicate the imported dust from four different incoming
sources.
FIGURE
1 Two units
located on opposite sides of a site will indicate the imported
precipitation arriving at the site as well as the corresponding export
from the site in both directions.
FIGURE
1 By
extrapolating the import result from one unit with the export result
from the second unit, an indication of the exact generated dust can be
made. The undertaking can then establish exactly how much of the
exported dust they are responsible for.
FIGURE
1
FIGURE
1 Two or more
units can be positioned in line at regular intervals to ascertain the
exact extent of dust precipitation from a dump or other dust producing
feature or operation, enabling a detailed precipitation model to be
prepared.
SAMPLE CAPTURE AND
ASSESSMENT
In order to capture and retain the
precipitant dust, the capture buckets are partly filled with a capture
medium to which an algaecide has been added.
Once the sample bucket has been
retrieved the sample is filtered to remove any large +0.50mm organic
particles or insects, which do not constitute dust.
The sample is then filtered through a
wet strength nitro-cellulose filter of pore size 1.0µm, which is
weighed both before filtration and again after desiccation of the
filtrate and filter. The mass of captured filtrate is thus determined.
Should the soluble chlorides in
coastal samples be required, a known volume of the filtrate water is
desiccated and the resulting salts weighed. By calculation the mass of
solubles can be determined.
As the cross-sectional area of each
collection bucket is known, the precipitation rate per m2 can be
determined by calculation and the result indicated in any units to the
time weighting preferred.
As most standards require the results
to be reflected on a Milligram/day/square metre basis it is preferable
to report results in this format.
SAMPLE ANALYSIS
While it is possible to ash each
sample to determine the exact carbon or organic constituent, this is a
lengthy process and should rather be dispensed with in favour of
microscopic analysis that will permit the analyst to determine the
following:
The type of recognisable organic
particulate and pollens present, their size as compared to 5µm
graticle spacing and an estimate of the amount of organic matter. A
range of magnifications from 80 to 150 is ideal and an old Konimeter
microscope and stage provides an ideal combination of specifications.
An estimate of the percentage of respirable particulate can also be
made. A cursory scan for fibrous material can be undertaken.
If all of the samples taken over an
extended period (say 1 year) are combined to make up to four composite
samples for each monitoring unit or station, these can be analysed for
a variety of elements as a "finger print" operation. There
is usually enough sample, once all of the filters are ashed, to make
up a pellet for further analysis. Such quantitative analysis could
include:
The latter option permits 36 and 39
element packages to be run on an XRF spectrometer with major elements
analysed and reported on as oxides using an energy dispersive X-ray
analyser.
A further ICP ME 46A or M analysis
can be used in a qualitative capacity but the method has limitation as
sample masses in excess of 20g are needed.
Finally for metal recognition with
very small samples, the AAGEOBM method utilising flame AAS analysis
can be considered.
All of this detailed analysis can be
undertaken by several laboratories that specialise in assay, soil
sampling and environmental analysis at various prices.
PRESENTATION &
EXTRAPOLATION OF THE RESULTS
As each sampling period will produce
results, these can be added to the previous data and the ongoing
hyperbolic trend indicated. Once a year's results have been plotted it
is possible to overlay the monthly results as these become available
in order to compare the monthly results with of the corresponding
month a year earlier. Similarly annual trend lines can be compared.
The hyperbolic trend curve will thus
indicate the degree of improvement or deterioration on an ongoing
basis.
A mobile unit can be used to monitor
on an ad-hoc basis any area not adequately covered by fixed monitors.
The units can also be used for area investigations.
Trend graphs can be plotted from the
programme (Microsoft Excel based) that we have developed to chart
results from the forty odd units under our direct supervision.
In the same way that units on both
sides of an installation or dust source will indicate the degree of
export of dust, so units along the same geographical bearing can be
assessed to establish how dust is lifted from one source to be
deposited further along the line and then a further dust source
replenishes the load to be deposited elsewhere. In investigations of
this type "finger printing" of certain characteristics is
required to establish the true extent of travel of the particulate and
how dilution occurs over distance.
While we do not advocate that all
mines or industrial concerns need to go to the limits outlined above,
it is worth considering that the units installed around an undertaking
may provide extremely valuable information that could be of use in
research work.
NETWORKING
As described above the consideration
of networking the directional particulate movement can provide
extremely valuable information for research of the following nature:
The encroachment of desertification
in dry arid areas.
Cross contamination in multi product
open stockpiles.
The health effects of crop spraying
and the re-exposure of persons during other operations involved with
the sprayed crops - reaping, ploughing or burning the stubble.
The incidence of allergens and
ongoing pollen counts, which have proved valuable in warning small
community susceptible persons of pending high pollen counts is
extremely valuable involving only an additional scrutiny of the
samples.
Cross contamination of industrial
concerns that may be exporting dust towards each other.
Finally, much research is being
carried out on intercontinental sub-micronic dust migration and
African red dust is resulting in the death and destruction of sea
corals off the Florida Coast (USA).
While PM10 and PM 2.5 monitoring is
proving valuable in establishing the local content of air, PM10
devices ensuring the directional sampling are not producing conclusive
results and are subject to local site vagaries without the back-up of
extensive fall-out directional dust networks.
FALL-OUT MONITORING
(SOLUBLE POLLUTANTS)
THE MONITORING
CONCEPT & ASSESSMENT
The assessment of soluble compounds
that are arrested during the capture of fall-out particulate can be
quantified if these are thought to be an issue. At the coast the
incidence of dissolved chlorides (NaCl) could play a part in loading a
particulate result and should the actual captured soluble compounds
need to be quantified, this can be undertaken by desiccating a known
volume of the remaining catch media and weighing the residue. This can
then be related to the actual volume of the catch media remaining
after filtration of the sample.
When chlorides have to be assessed
the algaecides Sodium Hypochlorite or Potassium Permanganate should be
omitted and a shorter catch period used to prevent the build-up of
algae in the sample.
Analysis of the catch media for other
compounds can also be undertaken using wet chemistry techniques to
ascertain the presence of any other soluble compounds, iron salts and
the like.
PRESENTATION AND
EXTRAPOLATION OF THE RESULTS
Soluble compounds do not usually play
a major part in the quantification of particulate sampling inland and
we normally do not include the result after initially commenting on
the conditions.
In cases where monitor units are
located close to the sea we usually undertake a quantification
exercise during the peak summer months and again during the middle of
winter to ascertain the mass migration of salt. Each of these values
is then considered to be constant. The weighted averages are then
included in the import values.
NETWORKING
There is little value in networking
the results of the solubles mass as these masses fall off rapidly with
an increase in distance from the sea or saline waters' edge. On the
West Coast we interestingly note that traces of salt are found only in
the seaward samples, indicating that the salt laden air precipitates
quickly. Correspondingly, a unit located about 2.0 km from the sea
line only has a salt content during the peak onshore wind season.
FALL-OUT MONITORING
(BIOLOGICAL AGENTS)
THE MONITORING
CONCEPT
Although our research in this field
has indicated some early promising results we need to do a lot more
work to achieve a measure of confidence in our biological agent
monitoring.
Our early research followed attempts
to monitor the movement of airborne bacteria from composting plants
and manure dumps, as we considered that there might be some migration
especially during the dry Western Cape summer months.
As we were hoping to keep any
bacteria alive for as long as possible, we could not use any
algaecides in the catch media; we elected to use sterile filtered
water and leave the catch buckets out for shorter periods of time.
Once the buckets were filtered to
remove any insoluble particulate we cultured the catch media water in
an attempt to locate saprophytes or other bacteria colonies.
Approximately 60% of the samples yielded colonies of some sort of
bacteria.
When the catch media was dosed with
diluted culture nutrient the positive results were considerably higher
at over 75%. In most cases buckets facing away from the installations
had no trace of colony development.
We have as yet not identified any
coliform bacteria but our research programme in this regard will
continue during 2002.
LABORATORY WORK
CO-ORDINATION
The biological analysis work requires
careful co-ordination and the micro-biologist should be thoroughly
briefed before a similar programme is considered as their input in the
research is critical especially with regard to the preparation of the
sampling buckets and catch media, which must only be decanted into
sterile buckets at the last minute to prevent inadvertent
contamination.
The DustWatch monitor unit in each
case is also thoroughly cleaned and disinfected for the above reason.
PROJECTS EARMARKED
FOR FURTHER RESEARCH
We hope to undertake a dust
dispersion exercise during 2002 concentrating on the effects of
topography and vegetation on the actual settlement rates noted. This
will form a valuable dispersion model for future work on rock dumps.
The sampling for biological agents
needs a lot more work and we hope to achieve definite results within
2002. As part of our research into the movement of bacteria we hope to
be monitoring agents emanating from a coastal seal colony as well as
the existing work on monitoring the composting facilities already
commented on.
We hope to become part of an
intercontinental research project quantifying and capturing African
dust export in an international venture.
DustWatch MONITORS
THE UNIT DESIGN
AND OPERATION
The DustWatch system was developed as
an affordable means of providing practical monitoring with features
not available in the market place. While they are robustly constructed
and early models have now been in the harshest environments for nearly
three years with minimal signs of major corrosion. Other units in
operation at corrosive plants have not been as fortunate and while
early primed and painted models definitely lack the protection of
powder coated units. We have standardised on the later units but we do
note that even the corroded earlier units still operate satisfactorily
and some have been painted as a refurbishment exercise.
The design of the selector disk
emulates the operation of an aircraft wing; a feature working at wind
velocities exceeding 3.0 m/s. The feature results in diversion of any
particulate larger than 0.5mm that is wind driven at 3.0 m/s or more
over the selector opening. This feature also minimise the capture of
grits while the wind is blowing. The collected dust and particulate
thus only occurs when the wind velocity falls to a point where
precipitation is possible. Under extremely quiet conditions the very
fine dust fractions are precipitated as well.
The collection height has been
selected with several features in mind. The lifting of +500µm
material in a 3.0 m/s wind velocity can only in a rare aerodynamic
form achieve a height of about 2.0 m. The bucket lips are positioned
at 2.2m.
The buckets can be reached for ease
of handling by persons of 1.5m or taller. The elevating support cradle
locks in position, protecting the buckets from theft or pilfering to a
degree.
The selector disk runs on a 318
stainless steel shaft running in a nylon or Vesconite bushing for a
longer trouble-free life with a minimum possibility of binding and
maintenance. The disc is also dynamically balanced to minimise
rotation bias.
DIRECTION
MONITORING
In a twin bucket unit the angle of
divergence at which the incoming dust laden wind can be collected is
about 14° while on the 4-bucket units there is a possibility of
vector loading of two buckets with bisecting winds. Site tests on
single bucket collection supports the vector calculations and thus we
have accepted the criteria as representative.
Practical tests in areas of known
emission have yielded analytical results supporting the vector
calculations as a second means of verification. The degree of accuracy
exceeded 85% on all of the tests carried out.
The accuracy exceeds that of any
other directional sampling system available as many monitor an angle
of 180° divergence with the twin bucket arrangement.
PARTICLE SIZE
SELECTION
As already outlined above, the
selector disk achieves the upper size limit of 100µm classification.
While we have not ashed a composite
sample of results yet in order to obtain a laser scan particulate size
analysis, we hope to carry out such an exercise shortly. In the
meanwhile an assessment of particulate sizing can be obtained by
examining each filter under the microscope eyepiece graticle, which is
graded in 5 to 10µm gridlines for size recognition.
COMPLIANCE WITH
STANDARDS AND CODES OF PRACTICE
As already mentioned, the entire
concept meets the requirements of ASTM D1739 but this does not cater
for wind direction so we have retained the fundamentals of the
standard, including the recommended maxima applicable.
In order to meet the requirements of
ISO 14001 stipulated monitoring the entire monitoring regimen has to
be presented together with standard procedures, manuals, reporting
format and traceable documentation. Assistance and detailed operator
and assessment training is available and accompanies the purchase of a
system.
World Bank standards have similar
requirements and the package offered has met these requirements as
well.
The Chief Pollution Control Officer
of the Department of the Environment and Tourism has accepted
monitoring results based on fall-out monitoring and has specified
limits based on those applicable in the USA.
The Department of Minerals and
Energy, while applying strict occupational hygiene standards outlined
in the requirements of the MHSA 1996, have on many occasions
sanctioned DustWatch monitoring in line with the Chief Pollution
Control officers requirements, especially when exported dust has
become as issue.
The PM10 and PM 2.5 monitoring
concentrated on by the American EPA has been specifically used to
monitor urban populations and is not designed to assess potential
import/export dust situations at a local level.
In our opinion no South African
manufactured PM 10 or PM 2.5 units meet the EPA standards as outlined
in the Federal Register 40 CFR parts 53 and 58.
TWO, FOUR AND
MULTIPLE BUCKET DustWatch® UNITS
We have already outlined both the
twin and four bucket units manufactured at present as product units.
While we are considering a six bucket
unit as a research unit we note that the entire unit has become
exponentially larger and more expensive and we are already concerned
that the over lap between buckets is likely to compromise the vector
principle, further negating any advantages that further points may
offer.
Under such circumstances we prefer to
install two 4-bucket units with one monitoring the bisection
directions effectively indicating 8 incoming wind directions.
In one instance we have manufactured
a prototype 3-bucket unit with the buckets located on the prevailing
wind directions to customise the unit. Results have been most
successful.
LABORATORY
ASSESSMENT
While we have already covered the
outside agency laboratory work that can be done we offer experience
and some good tips to improve the efficiency of the monitoring
programme.
WEIGHING &
MASS DETERMINATIONS
The five or six decimal gram micro
balances that are available on the mine for personnel gravimetric dust
sampling are adequate for any filter weighing.
Masses are taken in mg where possible
as results are indicated in milligram units.
With the use of wet strength
cellulose filter material, the moisture absorption associated with the
filters is minimal providing there is at least a 12-hour
acclimatisation period.
Desiccation should ideally be
undertaken under ambient conditions, as accelerated desiccation over a
warmer tray will result in severe curling of the filter and cracking
of the filtrate.
While an allowance of 48 hours is
usually made, it is possible to gauge the point at which total
desiccation has occurred. Up to this point a filter will lose mass on
a continuous basis showing a steadily declining mass while on the
balance pan indicating that evaporation of moisture is still
occurring. Once the filter reaches parity with atmospheric conditions
masses become static.
STORING FILTERS
As all environmental assessment
filters are 47mm Ř, the Ř47 petri slides usually used for the
storage and handling of gravimetric dust sampling filters can be used.
Once all of the information on
filters has been captured and the filters examined microscopically
these can be stored as composites in disposable Ř 65 petri's, which
are considerably cheaper and hold up to about 50 or more filters
before there is any difficulty closing the lid.
Multi-elemental scans can be
conducted annually to a composite sample made up of all of each of the
north, south, east and west filters of a single unit to obtain finger
prints of the annual input or ambient dust.
Storage after this stage will
constitute a mine or industry policy decision.
IN-HOUSE SERVICING
OR CONTRACTING OUT
While most mining and larger
industrial concerns have elected to run sampling and monitoring
programmes themselves following the initial training and equipping of
in-house laboratories, most local concerns have chosen to contract out
the entire programme to our laboratory.
Concerns running their own programmes
can be audited periodically.
In the West coast and Cape Peninsula
areas we run programme for many concerns - changing buckets,
recovering the samples, assessments and the preparation of detailed
reports.
In remote areas where access is a
problem, our clients change their own buckets, decanting the filtrate
and water into 2 litre re-useable PVC bottles with seal caps. These
samples are couriered down to our Piketberg laboratory where the
assessments and monthly reports are prepared.
We anticipate appointing part time
agents in areas where the throughput can justify the services. The
agents will undertake bucket preparation, changing buckets, and
filtrate capture before sending the filters to our laboratory by
courier service for final assessment in addition to maintenance of the
monitoring equipment.
DESIRABLE TRENDS AND
MONITORING DEVELOPMENTS
In order to establish monitoring of
environmental dust and pollution it is necessary to develop technologies
that are simple and cheap and can be operated by unsophisticated
communities rather than high tech solutions costing millions to
implement with high levels of technical skill and training to operate.
It is pointless developing technologies that 5% of the world can afford
and can run. Let us rather develop acceptable monitoring technology that
90% of the world can afford and can run. The remaining 10% who cannot
even afford this technology can be subsidised by those nations that have
the means. The high tech technology can be used to establish the finer
points of determinations.
We are currently designing and
developing technologies for passive monitoring of PM 10 particulates and
hope to achieve commercially available production units that will meet
the approval of the EPA within two years. With units of this type,
monitoring will - in common with the DustWatch - offer particulate
capture without the use of electronics, electrical energy and power
supplies, enabling the monitors to be positioned anywhere without the
necessity for mains power, battery systems, solar or wind generated
power installations. This, we feel, will meet the criteria mentioned in
the paragraph above and permit greater monitoring where it is required.
DUST MONITORING
ECONOMICS USING FALL-OUT TECHNIQUES
VALUE FOR MONEY
With the cost of equipment minimised
by mass production techniques, the cost of monitor units within the
DustWatch range are between 12 and 15% of the cost of other
electrically driven fall-out monitoring systems produced within South
Africa. Imported units cost considerably more due to the high $/Rand
exchange rate.
Assessment laboratory equipment is
largely available on individual mines and additional equipment is
manufactured locally or imported.
Sample capture filter material is
imported but is inexpensive due to high volume purchases and imports
directly from the manufacturer.
Various algaecides can be used
successful and most are available commercially in bulk at a minimal
cost.
While distilled water is desirable
for capture media preparation most installations are being operated
extremely effectively using oxidation/reduction sub-micronic
filtration techniques at a fraction of the cost of producing distilled
water. With multiple units in the field the changing of buckets can be
staggered to allow for the purchase of smaller filter units to
undertake the water filtration and to optimise labour utilisation.
A Microsoft Excel based assessment
programme to run the monitoring and generate reports is also available
and offers additional time savings.
TRAINING
As already outlined it is necessary
for field assistants and air quality analysts to be trained in the
techniques involved with the servicing and maintenance of the monitor
units as well as the assessment work and report preparation if the
monitoring has to be run within the ISO 14001 standards.
As part of the training exercise, the
optimisation of monitor positioning is covered at length to enable the
concern to find the best location for sampling units. Our training
engineer also instructs all parties in the preparation of buckets,
calculation and report preparation in addition to a technical
background on the need for monitoring. He will normally install and
optimise the assessment programme to suit the mine requirements and
train your staff.
A detailed standard procedure manual
is made available to all trained personnel as well as a certificate of
attendance at the training sessions.
JUSTIFICATION AND
PUBLIC RELATIONS
Many of the monitoring programmes
have been started in an effort to appease lobby groups or as a means
of defense from threatened legal action. In many cases the results
have initially proved just how bad emission levels from the various
concerns were.
As action was undertaken at the
various offending dust creation points, so improvements have been
quantifiable. The monthly reports have been made available at open day
meetings and in some instances monitors have even been welcomed on
adjacent properties as lobby groups are recruited to assist the
undertakings by addressing issues of veld burning and ploughing
techniques to minimise dust.
The long term monitoring has in at
least one instance been instrumental in locating unsuspected sources
of airborne pollutant generation as well as being a deterrent against
the use of unscheduled pesticides in the agricultural areas.
With the present research being
undertaken in the biological field we can hypothesise that monitoring
biological emissions from fish factories, process meal and other mills
will be possible as the "smells" can be quantified.
Similarly composting installations
can be monitored simultaneously for both particulate export as well as
potential biological agent export.
The monitoring of slimes dams and
dumps is already showing some successful results and long term
moisture/rain influence research is showing dependable results,
enabling timeous spraying to be undertaken.
In conclusion we note that monitoring
can result in public relations value in addition to ensuring a social
responsibility and improving conditions to workers and staff. The
international sales "bottom line" will also be of
inestimable value.
We believe the cost is worth it.
REFERENCES
- Federal register Part 1V - 40 CFR
Parts 53 & 58
- Revised requirements for Designation
of Reference
and Equivalent Methods for PM 2.5 and Ambient Air
Quality Surveillance for Particulate Matter - Final Rule
- EPA Revised Particulate Matter
Standards - Fact sheets
- Air Quality Criteria for Particulate
Matter -
EPA 600/P - 95/001af
- DustWatch fall-out dust monitoring,
sampling and
assessment procedure manual - DustWatch CC
- ASTM D1739 - American Standard Test
Method
- Strategy for Landfill Designs in
Arid Regions -
Anwar Al-Yagout & Frank Townsend ASCE
- Numerous routine reports &
investigative reports
How
does vegetation affect fall-out dust?
