US EPA Method 306a - Determination Of Chromium Emissions From Decorative And Hard Chromium Electroplating
AND CHROMIUM ANODIZING OPERATIONS
NOTE: This method does not include all of the specifications (e.g., equipment and supplies) and procedures (e.g., sampling and analytical) essential to its performance. Some material is incorporated by reference from other methods in 40 CFR Part 60, Appendix A and in this part. Therefore, to obtain reliable results, persons using this method should have a thorough knowledge of at least Methods 5 and 306. 1.0 Scope and Application.
1.1 Analyte. Chromium. CAS Number [7440-47-3]. 1.2 Applicability. 1.2.1 This method applies to the determination of
chromium (Cr) in emissions from decorative and hard chromium electroplating facilities, chromium anodizing operations, and continuous chromium plating at iron and steel facilities. The method is less expensive and less complex to conduct than Method 306. Correctly applied, the precision and bias of the sample results should be comparable to those obtained with the isokinetic Method 306. This method is applicable for the determination of air emissions under nominal ambient moisture, temperature, and pressure conditions.
2145 1.2.2 The method is also applicable to electroplating
and anodizing sources controlled by wet scrubbers. 1.3 Data Quality Objectives. 1.3.1 Pretest Protocol. 18.104.22.168 The pretest protocol should define and
address the test data quality objectives (DQOs), with all assumptions, that will be required by the end user (enforcement authority); what data are needed? why are the data needed? how will data be used? what are method detection limits? and what are estimated target analyte levels for the following test parameters.
22.214.171.124.1 Estimated source concentration for total chromium and/or Cr+6.
126.96.36.199.2 Estimated minimum sampling time and/or volume required to meet method detection limit requirements (Appendix B 40 CFR Part 136) for measurement of total chromium and/or Cr+6.
188.8.131.52.3 Demonstrate that planned sampling parameters will meet DQOs. The protocol must demonstrate that the planned sampling parameters calculated by the tester will meet the needs of the source and the enforcement authority.
184.108.40.206 The pre-test protocol should include information on equipment, logistics, personnel, process
2146 operation, and other resources necessary for an efficient
and coordinated performance test. 220.127.116.11 At a minimum, the pre-test protocol should
identify and be approved by the source, the tester, the analytical laboratory, and the regulatory enforcement authority. The tester should not proceed with the compliance testing before obtaining approval from the enforcement authority.
2.0 Summary of Method.
2.1.1 An emission sample is extracted from the source at a constant sampling rate determined by a critical orifice and collected in a sampling train composed of a Probe and impingers. The proportional sampling time at the cross sectional traverse points is varied according to the stack gas velocity at each point. The total sample time must be at least two hours.
2.1.2 The chromium emission concentration is determined by the same analytical procedures described in Method 306: inductively-coupled plasma emission spectrometry (ICP), graphite furnace atomic absorption spectrometry (GFAAS), or ion chromatography with a post- column reactor (IC/PCR).
2147 18.104.22.168 Total chromium samples with high chromium
concentrations (>35 Fg/L) may be analyzed using inductively coupled plasma emission spectrometry (ICP) at 267.72 nm.
NOTE: The ICP analysis is applicable for this method only when the solution analyzed has a Cr concentration greater than or equal to 35 Fg/L or five times the method detection limit as determined according to Appendix B in 40 CFR Part 136.
22.214.171.124 Alternatively, when lower total chromium concentrations (<35 Fg/L) are encountered, a portion of the alkaline sample solution may be digested with nitric acid and analyzed by graphite furnace atomic absorption spectroscopy (GFAAS) at 357.9 nm.
126.96.36.199 If it is desirable to determine hexavalent
chromium (Cr+6) emissions, the samples may be analyzed using an ion chromatograph equipped with a post-column reactor (IC/PCR) and a visible wavelength detector. To increase sensitivity for trace levels of Cr+6, a preconcentration system may be used in conjunction with the IC/PCR. 3.0 Definitions.
3.1 Total Chromium - measured chromium content that includes both major chromium oxidation states (Cr+3, Cr+6).
3.2 May - Implies an optional operation.
2148 3.3 Digestion - The analytical operation involving
the complete (or nearly complete) dissolution of the sample in order to ensure the complete solubilization of the element (analyte) to be measured.
3.4 Interferences - Physical, chemical, or spectral phenomena that may produce a high or low bias in the analytical result.
3.5 Analytical System - All components of the analytical process including the sample digestion and measurement apparatus.
3.6 Sample Recovery - The quantitative transfer of sample from the collection apparatus to the sample preparation (digestion, etc.) apparatus. This term should not be confused with analytical recovery.
4.1 Same as in Method 306, Section 4.0.
5.1 Disclaimer. This method may involve hazardous materials, operations, and equipment. This test method does not purport to address all of the safety issues associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to performing this test method.
2149 5.2 Chromium and some chromium compounds have been
listed as carcinogens although Chromium (III) compounds show little or no toxicity. Chromium is a skin and respiratory irritant. 6.0 Equipment and Supplies.
NOTE: Mention of trade names or specific products does not constitute endorsement by the Environmental Protection Agency.
6.1 Sampling Train. A schematic of the sampling train is shown in Figure 306A-1. The individual components of the train are available commercially, however, some fabrication and assembly are required.
6.1.1 Probe probe nozzle/tubing and Sheath.
188.8.131.52 Use approximately 6.4-mm (1/4-in.) inside diameter (ID) glass or rigid plastic tubing approximately 20 cm (8 in.) in length with a short 90 degree bend at one end to form the sampling probe nozzle. Grind a slight taper on the probe nozzle end before making the bend. Attach the probe nozzle to flexible tubing of sufficient length to enable collection of a sample from the stack.
184.108.40.206 Use a straight piece of larger diameter rigid tubing (such as metal conduit or plastic water pipe) to form a sheath that begins about 2.5 cm (1 in.) from the 90o bend on the probe nozzle and encases and supports the flexible tubing.
2150 6.1.2 Type S pitot tube . Same as Method 2, Section
6.1 (40 CFR Part 60, Appendix A). 6.1.3 Temperature Sensor. 220.127.116.11 A thermocouples.html">thermocouple, liquid-filled bulb
thermometer, bimetallic thermometer, mercury-in-glass thermometer, or other sensor capable of measuring temperature to within 1.5 percent of the minimum absolute stack temperature.
18.104.22.168 The Temperature Sensor shall either be positioned near the center of the stack, or be attached to the pitot tube as directed in Section 6.3 of Method 2.
6.1.4 Sample Train Connectors.
22.214.171.124 Use thick wall flexible plastic tubing (polyethylene, polypropylene, or polyvinyl chloride) ~ 6.4- mm (1/4-in.) to 9.5-mm (3/8-in.) ID to connect the train components.
126.96.36.199 A combination of rigid plastic tubing and thin wall flexible tubing may be used as long as tubing walls do not collapse when leak-checking the train. Metal tubing cannot be used.
6.1.5 impingers. Three, one-quart capacity, glass canning jars with vacuum seal lids, or three Greenburg-Smith (GS) design impingers connected in series, or equivalent, may be used.
2151 188.8.131.52 One-quart glass canning jar. Three separate
jar containers are required: 1) the first jar contains the absorbing solution; 2) the second is empty and is used to collect any reagent carried over from the first container; and 3) the third contains the desiccant drying agent.
184.108.40.206 Canning Jar Connectors. The jar containers are connected by leak-tight inlet and outlet tubes installed in the lids of each container for assembly with the train. The tubes may be made of ~ 6.4 mm (1/4-in.) ID glass or rigid plastic tubing. For the inlet tube of the first impinger, heat the glass or plastic tubing and draw until the tubing separates. Fabricate the necked tip to form an orifice tip that is approximately 2.4 mm (3/32-in.) ID.
220.127.116.11.1 When assembling the first container, place the orifice tip end of the tube approximately 4.8 mm (3/16- in.) above the inside bottom of the jar.
18.104.22.168.2 For the second container, the inlet tube need not be drawn and sized, but the tip should be approximately 25 mm (1 in.) above the bottom of the jar.
22.214.171.124.3 The inlet tube of the third container should extend to approximately 12.7 mm (1⁄2-in.) above the bottom of the jar.
126.96.36.199.4 Extend the outlet tube for each container approximately 50 mm (2 in.) above the jar lid and downward
2152 through the lid, approximately 12.7 mm (1⁄2-in.) beneath the
bottom of the lid. 188.8.131.52 Greenburg-Smith impingers. Three separate
impingers of the Greenburg-Smith (GS) design as described in Section 6.0 of Method 5 are required. The first GS impinger shall have a standard tip (orifice/plate), and the second and third GS impingers shall be modified by replacing the orifice/plate tube with a 13 mm (1⁄2-in.) ID glass tube, having an unrestricted opening located 13 mm (1⁄2-in.) from the bottom of the outer flask.
184.108.40.206 Greenburg-Smith Connectors. The GS impingers shall be connected by leak-free ground glass “U” tube connectors or by leak-free non-contaminating flexible tubing. The first impinger shall contain the absorbing solution, the second is empty and the third contains the desiccant drying agent.
6.1.6 manometer. Inclined/vertical type, or equivalent device, as described in Section 6.2 of Method 2 (40 CFR Part 60, Appendix A).
6.1.7 Critical Orifice. The critical orifice is a small restriction in the sample line that is located upstream of the vacuum pump. The orifice produces a constant sampling flow rate that is approximately 0.021 cubic meters per minute (m3/min) or 0.75 cubic feet per minute (cfm).
2153 220.127.116.11 The critical orifice can be constructed by
sealing a 2.4-mm (3/32-in.) ID brass tube approximately 14.3 mm (9/16-in.) in length inside a second brass tube that is approximately 8 mm (5/16-in.) ID and 14.3-mm (9/16-in.) in length .
18.104.22.168 Materials other than brass can be used to construct the critical orifice as long as the flow through the sampling train can be maintained at approximately 0.021 cubic meter per minute (0.75) cfm.
6.1.8 Connecting Hardware. Standard pipe and fittings, 9.5-mm (3/8-in.), 6.4-mm (1/4-in.) or 3.2-mm (1/8-in.) ID, may be used to assemble the vacuum pump, console meter and other sampling train components.
6.1.9 Vacuum Gauge. Capable of measuring approximately 760 mm Hg (30 in. Hg) vacuum in 25.4 mm Hg (1 in. Hg) increments. Locate vacuum gauge between the critical orifice and the vacuum pump.
6.1.10 pump Oiler. A glass oil reservoir with a wick mounted at the vacuum pump inlet that lubricates the pump vanes. The oiler should be an in-line type and not vented to the atmosphere. See EMTIC Guideline Document No. GD- 041.WPD for additional information.
6.1.11 Vacuum pump. Gast Model 0522-V103-G18DX, or equivalent, capable of delivering at least 1.5 cfm at 15 in. Hg vacuum.
2154 6.1.12 Oil Trap/Muffler. An empty glass oil
reservoir without wick mounted at the pump outlet to control the pump noise and prevent oil from reaching the console meter.
6.1.13 By-pass Fine Adjust Valve (Optional). Needle valve assembly 6.4-mm (1/4-in.), Whitey 1 RF 4-A, or equivalent, that allows for adjustment of the train vacuum.
22.214.171.124 A fine-adjustment valve is positioned in the optional pump by-pass system that allows the gas flow to recirculate through the pump. This by-pass system allows the tester to control/reduce the maximum leak-check vacuum pressure produced by the pump.
126.96.36.199.1 The tester must conduct the post test leak check at a vacuum equal to or greater than the maximum vacuum encountered during the sampling run.
188.8.131.52.2 The pump by-pass assembly is not required, but is recommended if the tester intends to leak-check the 306A train at the vacuum experienced during a run.
6.1.14 console meter. An Equimeter Model 110 test meter or, equivalent with Temperature Sensor(s) installed (inlet/outlet) to monitor the meter temperature. If only one Temperature Sensor is installed, locate the sensor at the outlet side of the meter. The console meter must be capable of measuring the gaseous volume to within +2% of the true volume.
2155 NOTE: The Method 306 sampling train is also
commercially available and may be used to perform the Method 306A tests. The sampling train may be assembled as specified in Method 306A with the sampling rate being operated at the delta H@ specified for the calibrated orifice located in the meter box. The Method 306 train is then operated as described in Method 306A.
6.2 barometer. Mercury aneroid barometer, or other barometer equivalent, capable of measuring atmospheric pressure to within + 2.5 mm Hg (0.1 in. Hg).
6.2.1 A preliminary check of the barometer shall be made against a mercury-in-glass reference barometer or its equivalent.
6.2.2 Tester may elect to obtain the absolute barometric pressure from a nearby National Weather Service station.
184.108.40.206 The station value (which is the absolute barometric pressure) must be adjusted for elevation differences between the weather station and the sampling location. Either subtract 2.5 mm Hg (0.1 in. Hg) from the station value per 30 m (100 ft) of elevation increase or add the same for an elevation decrease.
220.127.116.11 If the field barometer cannot be adjusted to agree within 0.1 in. Hg of the reference barometric, repair
2156 or discard the unit. The barometer pressure measurement
shall be recorded on the sampling data sheet. 6.3 Sample Recovery. Same as Method 5, Section 6.2
(40 CFR Part 60, Appendix A), with the following exceptions: 6.3.1 Probe-Liner and Probe-probe nozzle Brushes. Brushes
are not necessary for sample recovery. If a Probe brush is used, it must be non-metallic.
6.3.2 Wash Bottles. Polyethylene wash bottle, for sample recovery absorbing solution.
6.3.3 Sample Recovery Solution. Use 0.1 N NaOH or 0.1 N NaHCO3, whichever is used as the impinger absorbing solution, to replace the acetone.
6.3.4 Sample Storage Containers.
18.104.22.168 glass Canning Jar. The first canning jar container of the sampling train may serve as the sample shipping container. A new lid and sealing plastic wrap shall be substituted for the container lid assembly.
22.214.171.124 Polyethylene or glass Containers. Transfer the Greenburg-Smith impinger contents to precleaned polyethylene or glass containers. The samples shall be stored and shipped in 250-mL, 500-mL or 1000-mL polyethylene or glass containers with leak-free, non metal screw caps.
6.3.5 pH Indicator Strip, for Cr+6 Samples. pH indicator strips, or equivalent, capable of determining the
2157 pH of solutions between the range of 7 and 12, at 0.5 pH
increments. 6.3.6 Plastic Storage Containers. Air tight
containers to store silica gel. 6.4 Analysis. Same as Method 306, Section 6.3.
7.0 Reagents and Standards.
NOTE: Unless otherwise indicated, all reagents shall conform to the specifications established by the Committee on Analytical Reagents of the American Chemical Society (ACS reagent grade). Where such specifications are not available, use the best available grade. It is recommended, but not required, that reagents be checked by the appropriate analysis prior to field use to assure that contamination is below the analytical detection limit for the ICP or GFAAS total chromium analysis; and that contamination is below the analytical detection limit for Cr+6 using IC/PCR for direct injection or, if selected, preconcentration.
7.1.1 Water. Reagent water that conforms to ASTM Specification D1193 Type II (incorporated by reference see 63.14). All references to water in the method refer to reagent water unless otherwise specified. It is recommended that water blanks be checked prior to preparing the sampling reagents to ensure that the Cr content is less than three (3) times the anticipated detection limit of the analytical method.
7.1.2 Sodium Hydroxide (NaOH) Absorbing Solution, 0.1 N. Dissolve 4.0 g of sodium hydroxide in 1 liter of water to obtain a pH of approximately 8.5.
7.1.3 Sodium Bicarbonate (NaHCO3) Absorbing Solution, 0.1 N. Dissolve approximately 8.5 g of sodium bicarbonate in 1 liter of water to obtain a pH of approximately 8.3.
7.1.4 Chromium Contamination.
126.96.36.199 The absorbing solution shall not exceed the QC criteria noted in Method 306, Section 7.1.1 (< 3 times the instrument detection limit).
188.8.131.52 When the Cr+6 content in the field samples exceeds the blank concentration by at least a factor of ten (10), Cr+6 blank levels < 10 times the detection limit will be allowed.
2159 NOTE: At sources with high concentrations of acids
and/or SO2, the concentration of NaOH or NaHCO3 should be > 0.5 N to insure that the pH of the solution remains at or above 8.5 for NaOH and 8.0 for NaHCO3 during and after sampling.
7.1.3 Desiccant. Silica Gel, 6-16 mesh, indicating type. Alternatively, other types of desiccants may be used, subject to the approval of the Administrator.
7.2 Sample Recovery. Same as Method 306, Section
7.3 Sample Preparation and Analysis. Same as Method 306, Section 7.3.
7.4 glassware Cleaning Reagents. Same as Method 306, Section 7.4.
7.5 Quality Assurance Audit Samples.
7.5.1 It is recommended, but not required, that a performance audit sample be analyzed in conjunction with the field samples. The audit sample should be in a suitable sample matrix at a concentration similar to the actual field samples.
7.5.2 When making compliance determinations, and upon availability, audit samples may be obtained from the appropriate EPA regional Office or from the responsible
2160 enforcement authority and analyzed in conjunction with the
field samples. NOTE: The responsible enforcement authority should be
notified at least 30 days prior to the test date to allow sufficient time for the audit sample to be delivered. 8.0 Sample Collection, Recovery, Preservation, Holding Times, Storage, and Transport.
NOTE: Prior to sample collection, consideration should be given as to the type of analysis (Cr+6 or total Cr) that will be performed. Deciding which analysis will be performed will enable the tester to determine which appropriate sample recovery and storage procedures will be required to process the sample.
8.1 Sample Collection. 8.1.1 Pretest Preparation. 184.108.40.206 Selection of Measurement Site. Locate the
sampling ports as specified in Section 11.0 of Method 1 (40 CFR Part 60, Appendix A).
220.127.116.11 Location of Traverse Points.
18.104.22.168.1 Locate the traverse points as specified in Section 11.0 of Method 1 (40 CFR Part 60, Appendix A). Use a total of 24 sampling points for round ducts and 24 or 25 points for rectangular ducts. Mark the pitot and sampling Probe to identify the sample traversing points.
2161 22.214.171.124.2 For round ducts less than 12 inches in
diameter, use a total of 16 points. 126.96.36.199 Velocity Pressure Traverse. Perform an
initial velocity traverse before obtaining samples. The Figure 306A-2 data sheet may be used to record velocity traverse data.
188.8.131.52.1 To demonstrate that the flow rate is constant over several days of testing, perform complete traverses at the beginning and end of each day's test effort, and calculate the deviation of the flow rate for each daily period. The beginning and end flow rates are considered constant if the deviation does not exceed 10 percent. If the flow rate exceeds the 10 percent criteria, either correct the inconsistent flow rate problem, or obtain the Administrator’s approval for the test results.
184.108.40.206.2 Perform traverses as specified in Section 8.0 of Method 2, but record only the )p (velocity pressure) values for each sampling point. If a mass emission rate is desired, stack velocity pressures shall be recorded before and after each test, and an average stack velocity pressure determined for the testing period.
220.127.116.11 Verification of Absence of Cyclonic flow. Check for cyclonic flow during the initial traverse to verify that it does not exist. Perform the cyclonic flow
2162 check as specified in Section 11.4 of Method 1 (40 CFR Part
60, Appendix A). 18.104.22.168.1 If cyclonic flow is present, verify that
the absolute average angle of the tangential flow does not exceed 20 degrees. If the average value exceeds 20 degrees at the sampling location, the flow condition in the stack is unacceptable for testing.
22.214.171.124.2 Alternative procedures, subject to approval of the Administrator, e.g., installing straightening vanes to eliminate the cyclonic flow, must be implemented prior to conducting the testing.
126.96.36.199 Stack Gas Moisture Measurements. Not required. Measuring the moisture content is optional when a mass emission rate is to be calculated.
188.8.131.52.1 The tester may elect to either measure the actual stack gas moisture during the sampling run or utilize a nominal moisture value of 2 percent.
184.108.40.206.2 For additional information on determining sampling train moisture, please refer to Method 4 (40 CFR Part 60, Appendix A).
220.127.116.11 Stack temperature Measurements. If a mass emission rate is to be calculated, a Temperature Sensor must be placed either near the center of the stack, or attached to the pitot tube as described in Section 8.3 of Method 2. Stack temperature measurements, shall be recorded before and
after each test, and an average stack temperature determined for the testing period.
18.104.22.168 Point Sampling Times. Since the sampling rate of the train (0.75 cfm) is maintained constant by the critical orifice, it is necessary to calculate specific sampling times for each traverse point in order to obtain a proportional sample.
22.214.171.124.1 If the sampling period (3 runs) is to be completed in a single day, the point sampling times shall be calculated only once.
126.96.36.199.2 If the sampling period is to occur over several days, the sampling times must be calculated daily using the initial velocity pressure data recorded for that day. Determine the average of the )p values obtained during the velocity traverse (Figure 306A-2).
188.8.131.52.3 If the stack diameter is less than 12 inches, use 7.5 minutes in place of 5 minutes in the equation and 16 sampling points instead of 24 or 25 points. Calculate the sampling times for each traverse point using the following equation:
Minutesatpointn' )patPointn X5min. ( )p)avg
Where: n =
)pavg = NOTE:
Sampling point number. Average pressure differential across pitot tube, mm H2O (in. H2O). Average of )p values, mm H2O (in. H2O). Convert the decimal fractions for minutes to
seconds. 184.108.40.206 Pretest Preparation. It is recommended, but
not required, that all items which will be in contact with the sample be cleaned prior to performing the testing to avoid possible sample contamination (positive chromium bias). These items include, but are not limited to: sampling Probe, connecting tubing, impingers, and jar containers.
220.127.116.11.1 Sample train components should be: 1) rinsed with hot tap water; 2) washed with hot soapy water; 3) rinsed with tap water; 4) rinsed with reagent water; 5) soaked in a 10 percent (v/v) nitric acid solution for at least four hours; and 6) rinsed throughly with reagent water before use.
18.104.22.168.2 At a minimum, the tester should, rinse the Probe, connecting tubing, and first and second impingers twice with either 0.1 N sodium hydroxide (NaOH) or 0.1 N sodium bicarbonate (NaHCO3) and discard the rinse solution.
2165 22.214.171.124.3 If separate sample shipping containers are
to be used, these also should be precleaned using the specified cleaning procedures.
126.96.36.199 Preparation of Sampling Train. Assemble the sampling train as shown in Figure 306A-1. Secure the probe nozzle-liner assembly to the outer sheath to prevent movement when sampling.
188.8.131.52.1 Place 250 mL of 0.1 N NaOH or 0.1 N NaHCO3 absorbing solution into the first jar container or impinger. The second jar/impinger is to remain empty. Place 6 to 16 mesh indicating silica gel, or equivalent desiccant into the third jar/impinger until the container is half full (~ 300 to 400 g).
184.108.40.206.2 Place a small cotton ball in the outlet exit tube of the third jar to collect small silica gel particles that may dislodge and impair the pump and/or gas meter.
220.127.116.11 Pretest Leak-Check. A pretest leak-check is recommended, but not required. If the tester opts to conduct the pretest leak-check, the following procedures shall be performed: 1) place the jar/impinger containers into an ice bath and wait 10 minutes for the ice to cool the containers before performing the leak check and/or start sampling; 2) to perform the leak check, seal the probe nozzle using a piece of clear plastic wrap placed over the end of a
2166 finger and switch on the pump; and 3) the train system leak
rate should not exceed 0.02 cfm at a vacuum of 380 mm Hg (15 in. Hg) or greater. If the leak rate does exceed the 0.02 cfm requirement, identify and repair the leak area and perform the leak check again.
NOTE: Use caution when releasing the vacuum following the leak check. Always allow air to slowly flow through the probe nozzle end of the train system while the pump is still operating. Switching off the pump with vacuum on the system may result in the silica gel being pulled into the second jar container.
18.104.22.168 Leak-Checks During Sample Run. If, during the sampling run, a component (e.g., jar container) exchange becomes necessary, a leak-check shall be conducted immediately before the component exchange is made. The leak-check shall be performed according to the procedure outlined in Section 22.214.171.124 of this method. If the leakage rate is found to be < 0.02 cfm at the maximum operating vacuum, the results are acceptable. If, however, a higher leak rate is obtained, either record the leakage rate and correct the sample volume as shown in Section 12.3 of Method 5 or void the sample and initiate a replacement run. Following the component change, leak-checks are optional, but are recommended as are the pretest leak-checks.
2167 126.96.36.199 Post Test Leak Check. Remove the Probe
assembly and flexible tubing from the first jar/impinger container. Seal the inlet tube of the first container using clear plastic wrap and switch on the pump. The vacuum in the line between the pump and the critical orifice must be >15 in. Hg. Record the vacuum gauge measurement along with the leak rate observed on the train system.
188.8.131.52.1 If the leak rate does not exceed 0.02 cfm, the results are acceptable and no sample volume correction is necessary.
184.108.40.206.2 If, however, a higher leak rate is obtained (>0.02 cfm), the tester shall either record the leakage rate and correct the sample volume as shown in Section 12.3 of Method 5, or void the sampling run and initiate a replacement run. After completing the leak- check, slowly release the vacuum at the first container while the pump is still operating. Afterwards, switch-off the pump.
8.1.2 Sample Train Operation.
220.127.116.11 Data Recording. Record all pertinent process and sampling data on the data sheet (see Figure 306A-3). Ensure that the process operation is suitable for sample collection.
2168 18.104.22.168 Starting the Test. Place the Probe/probe nozzle
into the duct at the first sampling point and switch on the pump. Start the sampling using the time interval calculated for the first point. When the first point sampling time has been completed, move to the second point and continue to sample for the time interval calculated for that point; sample each point on the traverse in this manner. Maintain ice around the sample containers during the run.
22.214.171.124 Critical flow. The sample line between the critical orifice and the pump must operate at a vacuum of > 380 mm Hg (>15 in. Hg) in order for critical flow to be maintained. This vacuum must be monitored and documented using the vacuum gauge located between the critical orifice and the pump.
NOTE: Theoretically, critical flow for air occurs when the ratio of the orifice outlet absolute pressure to the orifice inlet absolute pressure is less than a factor of 0.53. This means that the system vacuum should be at least > 356 mm Hg (> 14 in. Hg) at sea level and ~ 305 mm Hg (~ 12 in. Hg) at higher elevations.
126.96.36.199 Completion of Test.
188.8.131.52.1 Circular Stacks. Complete the first port traverse and switch off the pump. Testers may opt to perform a leak-check between the port changes to verify the
2169 leak rate however, this is not mandatory. Move the sampling train to the next sampling port and repeat the sequence. Be
sure to record the final console meter reading after completing the test run. After performing the post test leak check, disconnect the jar/impinger containers from the pump and meter assembly and transport the Probe, connecting tubing, and containers to the sample recovery area.
184.108.40.206.2 Rectangle Stacks. Complete each port traverse as per the instructions provided in 220.127.116.11.1.
NOTE: If an approximate mass emission rate is to be calculated, measure and record the stack velocity pressure and temperature before and after the test run.
8.2 Sample Recovery. After the train has been transferred to the sample recovery area, disconnect the tubing that connects the jar/impingers. The tester shall select either the total Cr or Cr+6 sample recovery option. Samples to be analyzed for both total Cr and Cr+6 shall be recovered using the Cr+6 sample option (Section 8.2.2).
NOTE: Collect a reagent blank sample for each of the total Cr or the Cr+6 analytical options. If both analyses (Cr and Cr+6) are to be conducted on the samples, collect separate reagent blanks for each analysis.
8.2.1 Total Cr Sample Option.
2170 18.104.22.168 Shipping Container No. 1. The first jar
container may either be used to store and transport the sample, or if GS impingers are used, samples may be stored and shipped in precleaned 250-mL, 500-mL or 1000-mL polyethylene or glass bottles with leak-free, non-metal screw caps.
22.214.171.124.1 Unscrew the lid from the first jar/impinger container.
126.96.36.199.2 Lift the inner tube assembly almost out of the container, and using the wash bottle containing fresh absorbing solution, rinse the outside of the tube that was immersed in the container solution; rinse the inside of the tube as well, by rinsing twice from the top of the tube down through the inner tube into the container.
188.8.131.52 Recover the contents of the second jar/impinger container by removing the lid and pouring any contents into the first shipping container.
184.108.40.206.1 Rinse twice, using fresh absorbing solution, the inner walls of the second container including the inside and outside of the inner tube.
220.127.116.11.2 Rinse the connecting tubing between the first and second sample containers with absorbing solution and place the rinses into the first container.
2171 18.104.22.168 Position the probe nozzle, Probe and connecting
plastic tubing in a vertical position so that the tubing forms a "U".
22.214.171.124.1 Using the wash bottle, partially fill the tubing with fresh absorbing solution. Raise and lower the end of the plastic tubing several times to allow the solution to contact the internal surfaces. Do not allow the solution to overflow or part of the sample will be lost. Place the probe nozzle end of the Probe over the mouth of the first container and elevate the plastic tubing so that the solution flows into the sample container.
126.96.36.199.2 Repeat the Probe/tubing sample recovery procedure but allow the solution to flow out the opposite end of the plastic tubing into the sample container. Repeat the entire sample recovery procedure once again.
188.8.131.52 Use approximately 200 to 300 mL of the 0.1 N NaOH or 0.1 N NaHCO3 absorbing solution during the rinsing of the Probe probe nozzle, Probe liner, sample containers, and connecting tubing.
184.108.40.206 Place a piece of clear plastic wrap over the mouth of the sample jar to seal the shipping container. Use a standard lid and band assembly to seal and secure the sample in the jar.
220.127.116.11.1 Label the jar clearly to identify its contents, sample number and date.
2172 18.104.22.168.2 Mark the height of the liquid level on the
container to identify any losses during shipping and handling.
22.214.171.124.3 Prepare a chain-of-custody sheet to accompany the sample to the laboratory.
8.2.2 Cr+6 Sample Option.
126.96.36.199 Shipping Container No. 1. The first jar container may either be used to store and transport the sample, or if GS impingers are used, samples may be stored and shipped in precleaned 250-mL, 500-mL or 1000-mL polyethylene or glass bottles with leak-free non-metal screw caps.
188.8.131.52.1 Unscrew and remove the lid from the first jar container.
184.108.40.206.2 Measure and record the pH of the solution in the first container by using a pH indicator strip. The pH of the solution must be >8.5 for NaOH and >8.0 for NaHCO3. If not, discard the collected sample, increase the concentration of the NaOH or NaHCO3 absorbing solution to 0.5 M and collect another air emission sample.
220.127.116.11 After measuring the pH of the first container, follow sample recovery procedures described in Sections 18.104.22.168 through 22.214.171.124.
2173 NOTE: Since particulate matter is not usually present
at chromium electroplating and/or chromium anodizing facilities, it is not necessary to filter the Cr+6 samples unless there is observed sediment in the collected solutions. If it is necessary to filter the Cr+6 solutions, please refer to the EPA Method 0061, Determination of Hexavalent Chromium Emissions from Stationary Sources, Section 7.4, Sample Preparation in SW-846 (see Reference 5) for procedure.
8.2.3 Silica Gel Container. Observe the color of the indicating silica gel to determine if it has been completely spent and make a notation of its condition/color on the field data sheet. Do not use water or other liquids to remove and transfer the silica gel.
8.2.4 Total Cr and/or Cr+6 Reagent Blank.
126.96.36.199 Shipping Container No. 2. Place approximately 500 mL of the 0.1 N NaOH or 0.1 N NaHCO3 absorbing solution in a precleaned, labeled sample container and include with the field samples for analysis.
8.3 Sample Preservation, Storage, and Transport.
8.3.1 Total Cr Option. Samples that are to be analyzed for total Cr need not be refrigerated.
8.3.2 Cr+6 Option. Samples that are to be analyzed for Cr+6 must be shipped and stored at 4o C (~40o F).
2174 NOTE: Allow Cr+6 samples to return to ambient
temperature prior to analysis. 8.4 Sample Holding Times. 8.4.1 Total Cr Option. Samples that are to be
analyzed for total chromium must be analyzed within 60 days of collection.
8.4.2 Cr+6 Option. Samples that are to be analyzed for Cr+6 must be analyzed within 14 days of collection. 9.0 Quality Control.
9.1 Same as Method 306, Section 9.0.
10.0 Calibration and Standardization.
NOTE: Tester shall maintain a performance log of all calibration results.
10.1 pitot Tube. The Type S pitot tube assembly shall be calibrated according to the procedures outlined in Section 10.1 of Method 2.
10.2 Temperature Sensor. Use the procedure in Section 10.3 of Method 2 to calibrate the in-stack Temperature Sensor.
10.3 metering System.
10.3.1 Sample Train console meter calibration. calibrations may be performed as described in Section 16.2 of Method 5 by either the manufacturer, a firm who provides calibration services, or the tester.
2175 10.3.2 console meter calibration Coefficient (Ym).
The meter calibration coefficient (Ym) must be determined prior to the initial use of the meter, and following each field test program. If the console meter is new, the manufacturer will have specified the Ym value for the meter. This Ym value can be used as the pretest value for the first test. For subsequent tests, the tester must use the Ym value established during the pretest calibration.
10.3.3 calibration Orifice. The manufacturer may have included a calibration orifice and a summary spreadsheet with the meter that may be used for calibration purposes. The spreadsheet will provide data necessary to determine the calibration for the orifice and meter (standard cubic feet volume, sample time, etc.). These data were produced when the initial Ym value was determined for the meter.
10.3.4 Ym meter Value Verification or meter calibration.
10.3.4.1 The Ym meter value may be determined by replacing the sampling train critical orifice with the calibration orifice. Replace the critical orifice assembly by installing the calibration orifice in the same location. The inlet side of the calibration orifice is to be left open to the atmosphere and is not to be reconnected to the sample train during the calibration procedure.
10.3.4.2 If the vacuum pump is cold, switch on the pump and allow it to operate (become warm) for several minutes prior to starting the calibration. After stopping the pump, record the initial console meter volume and meter temperature.
10.3.4.3 Perform the calibration for the number of minutes specified by the manufacturer's data sheet (usually 5 minutes). Stop the pump and record the final console meter volume and temperature. Subtract the start volume from the stop volume to obtain the Vm and average the meter temperatures (tm).
10.3.5 Ym Value Calculation. Ym is the calculated value for the console meter. Calculate Ym using the following equation:
Ym ' Where:
Pstd Tm Vm(std),mfg Tm
17.64 Vm Pbar
= Barometric pressure at meter, mm Hg, (in. Hg).
= Standard absolute pressure,
tm = Tm =
Metric = 760 mm Hg. English = 29.92 in. Hg. Average console meter temperature,EC, (EF). Absolute average console meter temperature, Metric EK = 273 + tm (EC). English ER = 460 + tm(EF). Standard absolute temperature, Metric = 293 EK. English = 528 ER. Volume of gas sample as measured (actual) by console meter, dcm,(dcf). Volume of gas sample measured by manufacture’s calibrated orifice and console meter, corrected to standard conditions (pressure/temperature) dscm (dscf). console meter calibration factor, (dimensionless).
10.3.6 Ym Comparison. Compare the Ym value provided by the manufacturer (Section 10.3.3) or the pretest Ym value to the post test Ym value using the following equation:
Ym (manufacturer)s or pretest value)
Ym (post&test value)
2178 10.3.6.1 If this ratio is between 0.95 and 1.05, the
designated Ym value for the meter is acceptable for use in later calculations.
10.3.6.1.1 If the value is outside the specified range, the test series shall either be: 1) voided and the samples discarded; or 2) calculations for the test series shall be conducted using whichever meter coefficient value (i.e., manufacturers's/pretest Ym value or post test Ym value) produces the lowest sample volume.
10.3.6.1.2 If the post test console meter Ym value differs by more than 5% as compared to the pretest value, either perform the calibration again to determine acceptability or return the meter to the manufacturer for recalibration.
10.3.6.1.3 The calibration may also be conducted as specified in Section 10.3 or Section 16.0 of Method 5 (40 CFR Part 60, Appendix A), except that it is only necessary to check the calibration at one flow rate of ~ 0.75 cfm.
10.3.6.1.4 The calibration of the console meter must be verified after each field test program using the same procedures.
NOTE: The tester may elect to use the Ym post test value for the next pretest Ym value; e.g., Test 1 post test Ym value and Test 2 pretest Ym value would be the same.
2179 10.4 barometer. Calibrate against a mercury
barometer that has been corrected for temperature and elevation.
10.5 ICP Spectrometer calibration. Same as Method 306, Section 10.2.
10.6 GFAA Spectrometer calibration. Same as Method 306, Section 10.3.
10.7 IC/PCR calibration. Same as Method 306, Section
11.0 Analytical Procedures.
NOTE: The method determines the chromium concentration in μg Cr/mL. It is important that the analyst measure the volume of the field sample prior to analyzing the sample. This will allow for conversion of μg Cr/mL to μg Cr/sample.
11.1 Analysis. Refer to Method 306 for sample preparation and analysis procedures. 12.0 Data Analysis and Calculations.
12.1 Calculations. Perform the calculations, retaining one extra decimal point beyond that of the acquired data. When reporting final results, round number of figures consistent with the original data.
12.2 Nomenclature. A = Cross-sectional area of stack, m2 (ft2).
d = D = ER =
F = L =
MCr = Ms =
2180 Water vapor in gas stream, proportion by
volume, dimensionless (assume 2 percent moisture = 0.02). pitot tube coefficient; “S” type pitot coefficient usually 0.840, dimensionless.
Concentration of Cr in sample solution, μg Cr/mL. Concentration of Cr in stack gas, dry basis, corrected to standard
conditions μg/dscm (gr/dscf). Diameter of stack, m (ft). Digestion factor, dimensionless. Approximate mass emission rate, mg/hr (lb/hr).
Dilution factor, dimensionless. Length of a square or rectangular duct, m (ft). Total Cr in each sample, μg (gr). Molecular weight of wet stack gas, wet basis, g/g-mole, (lb/lb-mole); in a nominal gas stream at 2% moisture the value is 28.62. Barometric pressure at sampling site, mm Hg (in. Hg).
tm = Tm =
2181 Absolute stack gas pressure; in this case,
usually the same value as the barometric pressure, mm Hg (in. Hg). Standard absolute pressure: Metric = 760 mm Hg.
English = 29.92 in. Hg. Average stack gas volumetric flow, dry, corrected to standard conditions, dscm/hr (dscf/hr). Average console meter temperature,EC (EF). Absolute average console meter temperature: Metric EK = 273 + tm (EC). English ER = 460 + tm(EF). Average stack temperature,EC (EF).
Vaf = Vbd =
Vbf = Vm =
VmL = Vm(std) =
vs = W =
2182 Absolute average stack gas temperature:
Metric EK = 273 + ts (EC). English ER = 460 + ts(EF). Standard absolute temperature: Metric = 293 EK.
English = 528 ER. Volume of sample aliquot after digestion (mL). Volume of sample aliquot after dilution (mL). Volume of sample aliquot submitted to digestion (mL). Volume of sample aliquot before dilution (mL). Volume of gas sample as measured (actual, dry) by console meter, dcm (dcf). Volume of impinger contents plus rinses (mL). Volume of gas sample measured by the console meter, corrected to standard conditions (temperature/pressure), dscm (dscf). Stack gas average velocity, calculated by Method 2, Equation 2-9, m/sec (ft/sec). Width of a square or rectangular duct, m (ft).
= console meter calibration factor, (dimensionless).
= Velocity head measured by the Type S pitot tube , cm H2O (in. H2O).
= Average of )p values, mm H2O (in. H2O). 12.3 Dilution Factor. The dilution factor is the
ratio of the volume of sample aliquot after dilution to the volume before dilution. The dilution factor is usually calculated by the laboratory. This ratio is derived by the following equation:
F ' Vaf Eq. 306A-4 Vbf
12.4 Digestion Factor. The digestion factor is the ratio of the volume of sample aliquot after digestion to the volume before digestion. The digestion factor is usually calculated by the laboratory. This ratio is derived by the following equation.
D ' Vad Eq. 306A-5 Vbd
12.5 Total Cr in Sample. Calculate MCr, the total μg Cr in each sample, using the following equation:
MCr ' VmLCSFD
12.6 Dry Gas Volume. Correct the sample volume measured by the console meter to standard conditions (20EC, 760 mm Hg or 68NF, 29.92 in. Hg) using the following equation:
V 'V Y Tstd Pbar ' K V Y Pbar
m(std) m m T
P 1 m m T mstd m
Where: K1 = Metric units - 0.3855 EK/mm Hg.
English units - 17.64 ER/in. Hg. 12.7 Cr Emission Concentration (CCr). Calculate CCr,
the Cr concentration in the stack gas, in μg/dscm (μg/dscf) on a dry basis, corrected to standard conditions, using the following equation:
CCr ' MCr Vm(std)
NOTE: To convert μg/dscm (μg/dscf) to mg/dscm (mg/dscf), divide by 1000.
12.8 Stack Gas Velocity. 12.8.1 Kp = Velocity equation constant:
Metric Kp ' 34.97 m (g/g&mole)(mm Hg) 1/2 sec (EK)(mm H2O)
2185 English Kp ' 85.49 ft (lb/lb&mole)(in. Hg) 1/2
sec (ER)(in. H2O) 12.8.2 Average Stack Gas Velocity.
vs ' KpCp( )p)avg
' 34.97 Cp ( )p)avg
12.9 Cross sectional area of stack.
A' Bd2 or A'LW Eq. 306A-10 4
12.10 Average Stack Gas Dry Volumetric flow Rate.
NOTE: The emission rate may be based on a nominal stack moisture content of 2 percent (0.02). To calculate an emission rate, the tester may elect to use either the nominal stack gas moisture value or the actual stack gas moisture collected during the sampling run.
Volumetric flow Rate Equation:
Qstd ' 3600(1&Bws)vs A
Where: 3600 = Conversion factor, sec/hr.
Qstd '62,234vs A( Ps ) Ts(avg)
NOTE: To convert Qstd from dscm/hr (dscf/hr) to dscm/min (dscf/min), divide Qstd by 60.
12.11 Mass emission rate, mg/hr (lb/hr): ER ' Ccr X Qstd X 10&3 (mg/hr) Eq. 306A-13
ER ' Ccr X Qstd X 1.43 X 10&4 (lb/hr) Eq. 306A-14
13.0 Method Performance. 13.1 Range. The recommended working range for all of
the three analytical techniques starts at five times the analytical detection limit (see also Method 306, Section 13.2.2). The upper limit of all three techniques can be extended indefinitely by appropriate dilution.
2187 13.2.1 Analytical Sensitivity. The estimated
instrumental detection limits listed are provided as a guide for an instrumental limit. The actual method detection limits are sample and instrument dependent and may vary as the sample matrix varies.
188.8.131.52 ICP Analytical Sensitivity. The minimum estimated detection limits for ICP, as reported in Method 6010A and the recently revised Method 6010B of SW-846 (Reference 1), are 7.0 μg Cr/L and 4.7 μg Cr/L, respectively.
184.108.40.206 GFAAS Analytical Sensitivity. The minimum estimated detection limit for GFAAS, as reported in Methods 7000A and 7191 of SW-846 (Reference 1), is 1.0 μg Cr/L.
220.127.116.11 IC/PCR Analytical Sensitivity. The minimum detection limit for IC/PCR with a preconcentrator, as reported in Methods 0061 and 7199 of SW-846 (Reference 1), is 0.05 μg Cr+6/L.
13.2.2 In-stack Sensitivity. The in-stack sensitivity depends upon the analytical detection limit, the volume of stack gas sampled, and the total volume of the impinger absorbing solution plus the rinses. Using the analytical detection limits given in Sections 18.104.22.168, 22.214.171.124, and 126.96.36.199; a stack gas sample volume of 1.7 dscm; and a total liquid sample volume of 500 mL; the
2188 corresponding in-stack detection limits are 0.0014 mg
Cr/dscm to 0.0021 mg Cr/dscm for ICP, 0.00029 mg Cr/dscm for GFAAS, and 0.000015 mg Cr+6/dscm for IC/PCR with preconcentration.
NOTE: It is recommended that the concentration of Cr in the analytical solutions be at least five times the analytical detection limit to optimize sensitivity in the analyses. Using this guideline and the same assumptions for impinger sample volume and stack gas sample volume (500 mL and 1.7 dscm, respectively), the recommended minimum stack concentrations for optimum sensitivity are 0.0068 mg Cr/dscm to 0.0103 mg Cr/dscm for ICP, 0.0015 mg Cr/dscm for GFAAS, and 0.000074 mg Cr+6/dscm for IC/PCR with preconcentration. If required, the in-stack detection limits can be improved by either increasing the sampling time, the stack gas sample volume, reducing the volume of the digested sample for GFAAS, improving the analytical detection limits, or any combination of the three.
13.3.1 The following precision data have been reported for the three analytical methods. In each case, when the sampling precision is combined with the reported analytical precision, the resulting overall precision may decrease.
2189 13.3.2 Bias data is also reported for GFAAS.
13.4 ICP Precision.
13.4.1 As reported in Method 6010B of SW-846 (Reference 1), in an EPA round-robin Phase 1 study, seven laboratories applied the ICP technique to acid/distilled water matrices that had been spiked with various metal concentrates. For true values of 10, 50, and 150 μg Cr/L; the mean reported values were 10, 50, and 149 μg Cr/L; and the mean percent relative standard deviations were 18, 3.3, and 3.8 percent, respectively.
13.4.2 In another multilaboratory study cited in Method 6010B, a mean relative standard of 8.2 percent was reported for an aqueous sample concentration of approximately 3750 μg Cr/L.
13.5 GFAAS Precision. As reported in Method 7191 of SW-846 (Reference 1), in a single laboratory (EMSL), using Cincinnati, Ohio tap water spiked at concentrations of 19, 48, and 77 μg Cr/L, the standard deviations were ±0.1, ±0.2, and ±0.8, respectively. Recoveries at these levels were 97 percent, 101 percent, and 102 percent, respectively.
13.6 IC/PCR Precision. As reported in Methods 0061 and 7199 of SW-846 (Reference 1), the precision of IC/PCR with sample preconcentration is 5 to 10 percent; the overall precision for sewage sludge incinerators emitting 120 ng/dscm of Cr+6 and 3.5 μg/dscm of total Cr is 25 percent
2190 and 9 percent, respectively; and for hazardous waste
incinerators emitting 300 ng/dscm of Cr+6 the precision is 20 percent. 14.0 Pollution Prevention.
14.1 The only materials used in this method that could be considered pollutants are the chromium standards used for instrument calibration and acids used in the cleaning of the collection and measurement containers/labware, in the preparation of standards, and in the acid digestion of samples. Both reagents can be stored in the same waste container.
14.2 Cleaning solutions containing acids should be prepared in volumes consistent with use to minimize the disposal of excessive volumes of acid.
14.3 To the extent possible, the containers/vessels used to collect and prepare samples should be cleaned and reused to minimize the generation of solid waste. 15.0 Waste Management.
15.1 It is the responsibility of the laboratory and the sampling team to comply with all federal, state, and local regulations governing waste management, particularly the discharge regulations, hazardous waste identification rules, and land disposal restrictions; and to protect the
2191 air, water, and land by minimizing and controlling all
releases from field operations. 15.2 For further information on waste management,
consult The Waste Management Manual for Laboratory Personnel
and Less is Better—Laboratory Chemical Reduction, available from the American
Department of Government Relations and 16th Street NW, Washington, DC 20036. 16.0 References.
Management for Waste
Chemical Society's Science Policy, 1155
1. F.R. Clay, Memo, impinger Collection Efficiency - Mason Jars vs. Greenburg-Smith impingers, Dec. 1989.
2. Segall, R.R., W.G. DeWees, F.R. Clay, and J.W. Brown. Development of Screening Methods for Use in Chromium Emissions Measurement and Regulations Enforcement. In: Proceedings of the 1989 EPA/A&WMA International Symposium- Measurement of Toxic and Related Air Pollutants, A&WMA Publication VIP-13, EPA Report No. 600/9-89-060, p. 785.
3. Clay, F.R., Chromium Sampling Method. In: Proceedings of the 1990 EPA/A&WMA International Symposium- Measurement of Toxic and Related Air Pollutants, A&WMA Publication VIP-17, EPA Report No. 600/9-90-026, p. 576.
4. Clay, F.R., Proposed Sampling Method 306A for the Determination of Hexavalent Chromium Emissions from Electroplating and Anodizing Facilities. In: Proceedings
2192 of the 1992 EPA/A&WMA International Symposium-Measurement of
Toxic and Related Air Pollutants, A&WMA Publication VIP-25, EPA Report No. 600/R-92/131, p. 209.
5. Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, SW-846, Third Edition as amended by Updates I, II, IIA, IIB, and III. Document No. 955-001- 000001. Available from Superintendent of Documents, U.S. Government Printing Office, Washington, DC, November 1986. 17.0 Tables, Diagrams, flowcharts, and Validation Data.
Figure 306A-1. Method 306A Sampling Train.
Figure 306A-2. Velocity Traverse and Point Sample Time Calculation Sheet.
Figure 306A-3. Chromium Constant Sampling Rate Field Data Sheet.