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1、 1 AS/NZS 4323.4:2009 Australian/New Zealand Standard TM Stationary source emissions Method 4: Area source samplingFlux chamber technique PREFACE This Standard was prepared by the Joint Standards Australia/Standards New Zealand Committee EV-007, Methods for the Examination of Air. It is Part 4 in a
2、series of Standards that provides methods for the sampling and analysis of stationary source emissions. The objective of this Standard is to provide parties interested in the sampling and monitoring of stationary source emissions with a flux chamber sampling technique for the determination of atmosp
3、heric contaminant emission rates from area sources, in particular, the determination of odour and hazardous air pollutants. Area sources include: (a) Landfill surfaces (e.g. working face, soil/compost/synthetic cover, clay capped and revegetated) of various ages. (b) Sewage treatment plant surfaces
4、(e.g. inlet channels, primary sedimentation tanks, aeration tanks, activated sludge tanks, clarifiers, sludge lagoons, sludge drying beds, facultative lagoons, anaerobic lagoons and dissolved air flotation tanks). (c) Composting surfaces (e.g. raw material stockpiles, compost windrows and final prod
5、uct stockpiles). (d) Sub-surface contaminated groundwater sources (e.g. floating petroleum layer affecting surface emissions). (e) Industrial sources (e.g. waste storage/disposal, sumps, surface spills, wastewater treatment plant surfaces and effluent disposal areas). (f) Agricultural sources (e.g.
6、feed lots, animal waste containments, crop preparation and residual crop treatment). (g) Contaminated/remediation sites. The assessment of environmental impacts associated with area sources relies on the ability to accurately measure the rate of atmospheric contaminants emitted from various liquid a
7、nd solid surfaces. For odour impact assessments, these sources have historically been difficult to quantify, partly due to the variability in odour analysis techniques (dynamic dilution olfactometry) used, prior to the publication of AS/NZS 4323.3, Stationary source emissions, Part 3: Determination
8、of odour concentration by dynamic olfactometry, and, more importantly, due to the range of sampling methods used in determining the area source emission rate. Techniques have included emission isolation flux chambers, wind tunnels, witches hats, source enclosures and downwind sampling/modelling tech
9、niques. AS/NZS 4323.3, while confirming the importance of odour sampling methodology, especially for area sources, excluded consideration of sampling, hence the need for a separate Standard. AS/NZS 4323.4:2009 AS/NZS 4323.4:2009 2 COPYRIGHT The term informative has been used in this Standard to defi
10、ne the application of the appendix to which it applies. An informative appendix is only for information and guidance. METHOD 1 SCOPE This Standard sets out area source sampling protocols to be followed when using a flux chamber for the determination of odour or other atmospheric contaminants. The me
11、thod provides a measure of area source odour and atmospheric contaminant flux emission rate, in units of ou.m/m.s and g/m.s, respectively. NOTE: Some indirect measurement techniques are described in Appendix A, however, they are for information only and do not form part of this Standard. 2 REFERENCE
12、D DOCUMENTS The following documents are referred to in this Standard: ISO Guide to the expression of uncertainty in measurement (ISO GUM) NATA Technical Note 8In-situ calibration of barometers Technical Note 19Liquid-in-glass thermometersSelection, use and calibration checks US EPA Measurement of ga
13、seous emission rates from land surfaces using an emission-isolation flux chamber. Users guide, EPA Contract No. 68-02-3889, Radian Corporation, February 1986 3 DEFINITIONS For the purpose of this Standard, the following definitions apply: 3.1 Area source A liquid or solid surface which emits odour o
14、r other inorganic or organic atmospheric contaminants. 3.2 Flux chamber An enclosure device consisting of an open cylindrical base, a sweep air supply line, perforated sweep air distribution system, outlet line and flotation device (for liquid surfaces), as a minimum. 3.3 Flux emission rate The atmo
15、spheric contaminant emission rate per unit surface area. 3.4 Odour Organoleptic attribute perceptible by the olfactory organ on sniffing certain volatile substances. The Standard is downloaded from Standard Sharing 3 AS/NZS 4323.4:2009 COPYRIGHT 3.5 Sweep air Air used to sweep the isolated solid or
16、 liquid surface and mix with the generated atmospheric contaminants. Sweep air should be dry, organic-free air equal to or better than commercial zero grade (less than 1 ppm total hydrocarbons as methane). 3.6 U95 A measurement uncertainty at a confidence interval of 95% according to ISO GUM. 4 PRIN
17、CIPLE Gaseous emissions are collected from an isolated surface area using a flux chamber. The surface gaseous emissions are swept through the flux chamber and outlet line, at a known sweep air flow rate. The atmospheric contaminants of interest are sampled from the chamber exit gases, either continu
18、ously or discretely. The flux emission rate is calculated based on the surface area isolated, the sweep air flow rate and the atmospheric contaminant concentration measured. Flux chamber designs are based on continuous stirred tank reactor theory. 5 APPARATUS 5.1 Enclosure device The enclosure devic
19、e shall be of a design such as a US EPA emission isolation flux chamber (US EPA, 1986). NOTE: The US EPA flux chamber is described in Appendix B. Available validation studies have been restricted to non-aerated surfaces. The apparatus on which the majority of data has been published, and extensive v
20、alidation studies conducted, is the US EPA emission isolation flux chamber. The assumption for flux chamber measurements is that the determined emission rate is representative of the total area source, both spatially and temporally. It is also assumed that the test procedure itself does not signific
21、antly influence the emission rate of the source under investigation. For this reason the apparatus used shall have undergone validation studies to establish appropriate equipment test protocols. Flux chamber designs are based on continuous stirred tank reactor theory. Consequently the introduced swe
22、ep air is well mixed with the surface emissions to air. The sweep air flow rate is much greater than the source emission flow rate (assumed to be zero under normal circumstances). The relatively low flow rates allow the use of compressed air cylinders as the source of sweep air. The flux chamber sha
23、ll be constructed from stainless steel or other suitably inert material (e.g. US EPA flux chamber acrylic dome). When an alternative enclosure device design to the US EPA emission isolation flux chamber is used, it shall have undergone similar validation studies. The effect of changes in the followi
24、ng chamber operating parameters on method accuracy and atmospheric contaminant recovery efficiency shall be evaluated, as a minimum, to enable the establishment of the following optimal operating parameters: (a) Sweep air flow rate/velocity. (b) Static pressure. (c) Insertion depth. (d) Sample colle
25、ction rate. AS/NZS 4323.4:2009 4 COPYRIGHT If a flux chamber is considered to be equivalent to the US EPA emission isolation flux chamber, data shall be available to demonstrate that theoretical and measured residence times shall agree within 2.5%. All such apparatus shall meet the following criteri
26、a: (i) Materials of construction are odour free and easily cleaned. (ii) Materials of construction minimize gaseous phase adsorption. (iii) Recoveries from standards are essentially 100%. (iv) Precision is typically better than 70% relative standard deviation. (v) Accuracy is typically better than 3
27、0%. (vi) System blank concentrations are less than the required area source sampling protocol method limit of detection, or less than the method limit of detection in the case of odour. 5.2 Flow rate control device A device that has one or more adjustment controls, to vary the flow rate of sweep air
28、 through the enclosure device. 5.3 Flow rate measurement device 5.3.1 Traceable reference standard flow measuring device With a U95 of 2% at the operating flow rate. 5.3.2 A traceable transfer standard flow measuring device With a U95 of 5% at the operating flow rate. May be used for field applicati
29、ons. The transfer standard device shall be calibrated against a reference standard device on a two yearly basis. 5.4 Temperature measurement device A traceable thermometer with a U95 of 0.5C and a resolution of 0.1C. The thermometer shall be checked against a reference standard thermometer at 0C (ic
30、e point), or at one point in the working range, on a six monthly basis (NATA Technical Note 19). 5.5 Static pressure measurement device An inclined liquid manometer, or equivalent (e.g. an electronic manometer, or a diaphragm- type pressure differential sensor with a direct reading gauge), capable o
31、f measuring pressure differentials down to 2 Pa with a U95 of 2 Pa. 5.6 Barometer A traceable barometer with a U95 of 0.5 kPa. The barometer shall be checked on a six-monthly basis, at one point against barometric pressure measured at an appropriately located meteorological station (NATA Technical N
32、ote 8). Alternatively, barometric pressure may be determined from measurements taken at an appropriately located meteorological station, with the pressure corrected for differences in elevation between the sampling site and the meteorological station (NATA Technical Note 8). 5.7 Timing device A stop
33、watch or other timing device, capable of measuring elapsed time with a U95 of 1% and a resolution of 0.1 second. The timing device shall be checked against the recorded time signal, over a minimum period of one hour, on a six-monthly basis. The Standard is downloaded from Standard Sharing 5 AS/NZS
34、4323.4:2009 COPYRIGHT 6 CALIBRATION Calibration of all apparatus used for area source sampling shall be conducted in accordance with the schedule contained in Table 1. TABLE 1 CALIBRATION SCHEDULE Apparatus Interval Flow rate measurement device 2 years Static pressure measurement device (liquid) 3 y
35、ears Static pressure measurement device (electronic) 1 year Barometer (aneroid) 6 months (Note 1) Thermometer (liquid in glass) 6 months (Note 2) Thermocouple/electronic thermometer 6 months (Note 2) Timing device 6 months (Note 3) NOTES: 1 Single point check against reference barometer. 2 Check at
36、ice point, or at one point in the working range, against a reference thermometer. 3 Test aurally against the recorded time message (speaking clock). Two measurements, separated by a minimum of 1 hour, are required. 7 SAMPLING PROCEDURE A summary of flux chamber operating parameters is given in Table
37、 2. TABLE 2 OPERATING PARAMETERS Item US EPA chamber Soil penetration depth (mm) Minimal Sweep air flow (L/min) 5 Sweep air velocity (m/s) 5.1 Equilibration time (min) 24 Pressure (Pa) 2 Sample flow rate (L/min) 2.5 max. The following procedures shall be applied when conducting an area source sampli
38、ng program: (a) All connecting tubing (sweep air supply line; sample lines) shall be constructed from PTFE, or PTFE lined. (b) Sweep air flow rate shall be monitored. The flow rate measurement device shall be calibrated in accordance with Clause 6. (c) Where possible, programme site tests shall coin
39、cide with calm wind conditions. (d) Establish area source emission rate zones for subsequent sampling, either through visual observation or screening measurements (e.g. methane at landfill surface). Record visual observations or screening test data. NOTE: For guidance on sampling of highly variable
40、emission sources refer to US EPA (1986). (e) Measure and record area of each emission zone. AS/NZS 4323.4:2009 6 COPYRIGHT (f) Site tests shall be programmed such that the potential for contamination is minimized (e.g. lowest to highest concentration source). (g) Position the flux chamber in the des
41、ignated area source zone in the following manner: (i) For solid surfaces, select a flat area. As far as practicable do not disturb the surface. If necessary use dry odour-free packing sand to seal between the chamber outer rim and the solid surface. (ii) For liquids, use flotation devices to locate
42、the chamber such that the outer rim just penetrates the surface. NOTE: The chamber may be equipped with a skirt of PTFE sheet, allowing waves to pass through, such that liquid surface roughness is not limited within the chamber. (h) Connect the sweep air supply, set the sweep air flow rate by measur
43、ement on the chamber inlet and allow the equipment to purge for the appropriate equilibration period (refer Table 2). (i) As a minimum, measure soil/liquid and air temperature, both inside and outside the chamber, and the chamber pressure, when the purge cycle has been completed. Other parameters th
44、at can be recorded include barometric pressure, wind speed, wind direction, rainfall, soil moisture content, and soil type. (j) Collect sample or monitor the atmospheric contaminant of interest, utilizing the appropriate technique (refer Appendix C), over a sample period less than 30 min. Ensure sam
45、ple flow rate does not exceed 50% of the sweep air flow rate. A minimum of 10% of the sampling points or once per sampling day, whichever is the greater, should be sampled as replicates (minimum of 2), where discrete sampling techniques are used. NOTES: 1 Appendix C provides guidance on atmospheric
46、containment sampling. 2 Replicates should be collected over the minimum time period possible to minimize source temporal variation. (k) Remove chamber and clean surfaces that have been in contact with the area source. Back flush the sample line for a period of 2 min. NOTE: Cleaning compounds selecte
47、d should take account of the atmospheric contaminants under investigation. (l) Relocate chamber to the next area source zone and repeat Items (g) to (k). (m) Conduct field blank equipment tests for each atmospheric contaminant of interest by placing the flux chamber on a clean stainless steel surfac
48、e, PTFE surface or carbon filtered water, and sample in accordance with the proposed area source sampling protocol. When sampling for odour, the blank test result shall be less than the dynamic olfactometer limit of detection. When sampling for other atmospheric contaminants, the blank test result s
49、hall not exceed the required area source sampling protocol method limit of detection. Field blanks shall be collected from the chamber at a minimum frequency of once per sampling day or 10% of the number of area source samples, whichever is the greater. NOTES: 1 High aeration rates may cause pressure effects due to exit restrictions. 2 The most accurate direct measurement technique involves total enclosure, sufficient ventilation to prevent fugitive emissions, and point source emission measurement technique