Environ. Sci. Technoi. 1984, 18, 803-808
Effect of Sampling Temperature, Filter Material, and Sample Treatment on Combustlion Source Emission Test Results William J. Mitchell"
Quallty Assurance Dlvlslon, Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 2771 1 Charles L. Bruffey
PEDCo Environmental, Inc., Clnclnnatl, Ohlo 45246
rn Samplers that simultaneously measure particulate, HzSO4, and SO2 emissions were evaluated at two coal-fired power plants to determine how the following parameters affected the sampling results: probe and filter temperature, filter type and position, and sample treatment (desiccation, 2-propanol extraction, and oven heating). It was found that the higher the probe and filter temperature, the lower the particulate measurement and the higher the H2SO4 measurement. It was also found that borosilicate glass-fiber filter thimbles are not suitable for these sources because they retain H2S04. In-stack samplers with Alundum thimbles gave particulate and H2S04 results equivalent to out-of-stack filter samplers (operated at 160 "C) at the plant equipped with only an ESP but not at the one that followed its ESP with an SOz scrubber. Oven heating and extraction with 2-propanol were not always effective in removing H2S04collected with the particulate. The results emphasize how important it is to control accurately probe and filter temperature during sampling.
Introduction Stack sampling for particulate, H2S04, and SO, was conducted at two coal-fired power plants to determine if a single sampler could be used to simultaneously measure these three pollutants at this type of source. The candidate samplers evaluated employed a filter (in-stack or out-ofstack) followed by Smith-Greenberg impingers containing 2-propanol (IPA) and 3% H202. The four-sampler technique developed by Mitchell and Midgett (I) for evaluating the performance of stack sampling methods was employed, that is, four samplers simultaneously sampled at an isokinetic rate at essentially the same point in the stack. In each sampling period (sampling run) at least two of the samplers were operated with their glass-lined probe and out-of-stack filter maintained at the 160 "C specified in EPA regulations (2). These two samplers, designated as reference method 5 samplers (3) in this study, served as the control samplers against which the performance of the other two samplers were compared. In this way the effect of the following on the particulate, H2S04,and SO2 results was evaluated filter and probe temperature, filter material and location in the sampler (in-stack, out-of-stack), and sample treatment (ambient desiccation, heating, and extraction with IPA). In 12 of the 25 sampling runs the other two samplers were method 5 samplers with their probe and filter maintained at approximately the following temperatures (probe/filter, "C): 160/100,104/104,127/127, and 188/ 188. These sampling temperatures were selected to evaluate the separation of HzS04 from the particulate as a function of sampling temperature, stack moisture, and H2SO4 dew point. Also, these temperatures represent the temperature range that occurs in commercially available, glass-lined probes and filters with externaly mounted temperature sensors to maintain the probe and filter 0013-936X/84/0918-0803$01.50/0
temperature at 160 OC (4). In four of the other 25 runs all four samplers were reference method 5 type to determine its precision at these sources. In the last nine runs the other two samplers were equipped with in-stack filters to evaluate the applicability of this type of sampler. All method 5 samplers used a 90-mm diameter Reeve Angel 934 AH, high-titania, flat, glass-fiber filter for particulate collection. This filter was also used between the IPA-containing and the first H202-containing impingers to collect any H2S04that passed through the IPA. It was selected because it was nonreactive to both HzS04 and SO2 (5). The instack filters evaluated were (1)medium porosity Alundum ceramic filter, (2) Reeve Angel 934 AH, (3) 19 X 90 mm BGI Corp. TA-3 borosilicate glass-fiber thimble, and (4) a BGI Corp. TA-3 thimble treated with H2S04before use (to passify H2S04reactive sites). The Alundum ceramic filter was selected because of its ready availability and common use in particulate testing. The BGI Corp. borosilicate glass-fiber thimble was selected to determine if it irreversibly retained H2S04as reported by Peters and Adams (5) for the following borosilicate glass-fiber, flat filters: MSA 1106BH, Gelman Spectrograde, Gelman AE,S&S 810, and Reeve Angel 900 AI?. (In their study, Peters and Adams found that these filters absorbed H2S04from a particulate-free air stream maintained at a temperature 60 "C above the acid dew point!) Other glass-fiber filters such as the Gelman A (medium titania) and Whatman GF/A (high barium) were not evaluated in our study because they had previously been shown to react with H2S04(5) and because thimble filters were not available.
Experimental Section Test Sites and Test Design. Both plants burned coal containing 2.7% S and 15% ash. The stack gas composition at the sampling point for plant A, which controlled its emissions with an ESP, was 156 f 5 "C, 13% C02,5% 02,7% H20, 1700 ppm of SO2 and 40 mg of H2S04/m3 (acid dew point 130 f 5 "C). The stack gas composition for plant B, which controlled its emissions with an ESP and a disorbic lime scrubber (SO, control), was 90 f 7 "C, 12% CO,, 7% 02,11% H20, 900 ppm of SO,, and 30 mg of H2S04/m3(acid dew point 130 f 5 "C). The sampling schedule employed for the testing is shown in Table I. Sampling was 2 h at 0.018-0.023 m3/min. Pretest Filter Treatment. Before the initial tare weight was obtained, all filters to be used for particulate collection were heated in a muffle furnace for 3 h at the maximum temperature at which the sample would be conditioned: that is, 188 "C for test 1and 316 OC for tests 2 and 3. After heating a t 316 "C, the following average percent weight losses were observed Reeve Angel 934 AH, 0.05%; BGI TA-3, 0.35%; Alundum ceramic, 0.008%. Samplers equipped with BGI Corp. thimbles at plant A (test 1)collected considerably more apparent particulate
0 1984 American Chemical Society
Environ. Scl. Technol., Voi. 18, No. 10, 1984
803
Table I. Field Tests Designa test plant 1
A
T,
sampling runs
158
1,3,5,7 8,'lO
9,11
sampler 1, 2
sampler 3
M5/160 "C M5/104 "C M5/160 "C M5/127 "C M5/160 "C M5/188
sampler 4 M5/104 "C M5/127 "C M5/188 "C
"C 2,4,6 2
A
158
1,3
3
B
90
2,4 1,2,3,4
M5/160 M5/160 M5/160 M5/160
"C "C "C "C
BGI-U AL BGI-T M5/160
BGI-U RA934 BGI-U M5/160 "C
"C 5,6,7,9 8,lO
M5/160 "C M5/100 "C M5/16OoC AL
M5/100 "C AL
"Symbols: T,= stack temperature ("C); AL = Alundum thimble; BGI-T = BGI-TA3 thimble treated with H2S04before use; BGI-U = BGI-TAB thimble used without acid treatment; RA934 = Reeve Angel 934AH, 90-mm diameter: M5 = method 5 sampler.
than the Alundum thimble and the reference method 5 sampler. Thus, it was decided to treat some BGI TA-3 thimbles with 50% H2SO4 and repeat the testing to see if the BGI's excessive weight gain could be minimized. For this test (test 2) the filters were soaked in 50% H2S04for 2 h at 135 "C, soaked for 30 min in 100% IPA at 20 "C, soaked in distilled water for 30 min at 80 "C, and finally oven-dried for 16 h at 316 "C. This treatment, which is a modification of the Barton and McAdie procedure (6), resulted in an average weight loss of 3.5%, a value 10 times higher than that from heating at 316 OC (0.35%). Sampling Equipment. In test 1the 2 m long probes contained a heatable, glass liner with a thermocouple sealed in the liner at the probe exit to measure the probe temperature. In tests 2 and 3, an additional thermocouple was sealed in the liner at the probe midpoint to improve temperature measurement and control to within f 1 5 "C during sampling ( 4 ) . The 90-mm diameter Reeve Angel 934AH filter used for particulate collection in all method 5 type samplers (out-of-stack filter) was mounted in a glass filter holder and placed in a heatable box; the temperature was monitored by using a thermocouple located immediately behind the filter support frit. These filters were controlled to within f 5 OC of the target temperature during testing. All in-stack filters were housed in the appropriate 316 stainless steel filter holder. Because preliminary tests showed that the in-stack filter holders reached stack temperature in 8-10 min in the absence of sampling, each in-stack filter was placed in the stack for at least 10 min before sampling was initiated. The particulate-collecting portion of each sampler in 23 of the 25 sampling runs was followed by an empty impinger and then by an EPA reference method 8 impinger assembly. This latter sampler is composed of the following: an impinger containing 200 mL of IPA, an RA 934AH flat filter, and two impingers connected in series containing 200 mL of 3% H20zand an impinger containing silica gel (3). The empty impinger, the solution in the IPA impinger, and the filter were used to condense the stack gas moisture and to collect H2S04. The two H,O,-containing impingers were used to collect SOz. After sampling, the impinger section of each sampler was immediately purged with charcoal-filtered air for 15 min to move any SO, absorbed in the first two impingers into the Hz02impingers. To prevent the silica gel in the last impinger from caking and subsequently breaking the im804
Environ. Sci. Technol., Vol. 18, No. 10, 1984
pinger, approximately 2 cm of glass wool was placed at the bottom of the impinger. In two of the 25 sampling runs the impingers contained 0.1 N HN03to collect and stabilize trace metal compounds that penetrated the particulate filter. Sample Recovery. Particulate filters were recovered and placed in labeled containers. All sample-exposed surfaces in front of the filters were rinsed with acetone, and the acetone was placed in a labeled container. The contents of the first two impingers and the filter between the IPA and first HzOzimpinger were placed in another container along with the IPA rinse of these impingers and of all sample-exposed surfaces located between them and the particulate filter. The contents of the third and fourth impingers were combined and placed in another container along with a H202rinse of the two impingers. Analysis. (1) Test I, Plant A. The acetone rinses were evaporated to dryness in tared beakers at ambient temperature, desiccated for 24 h, and weighed. All filters were desiccated at ambient temperature for 24 h and weighed. Desiccation and reweighing continued at 6-h intervals until either two consecutive weighings agreed within f 3 mg or it was apparent that no additional weight loss was occurring. Selected samples were then heated stepwise for 3-8 h in a muffle furnace at 160 and 188 "C. The samples were desiccated for at least 2 h after each heating and weighed at least twice, with at least 6 h between duplicate weighings. Particulate samples not so conditioned were soaked in 100 mL of 100% IPA; the IPA was then decanted after the particulate had settled, and the soaking was repeated once. The two IPA soakings were combined and diluted with water to 80% IPA by volume, and the sulfate content was determined by BaClO, titration (0.01 N) in the presence of thorin indicator as described in EPA reference method 8 (3). The IPA portion of the method 8 sampler (SO3, H2S04) was diluted with 100% IPA to yield an IPA concentration of 80% by volume; two aliquots were then analyzed by the BaClO,/thorin procedure. The H20zfraction (SO,) was diluted to 500 mL with distilled water. A 20-mL aliquot was then diluted to 100 mL with IPA and analyzed for by the BaClO,/thorin titration procedure. The impingers containing dilute HN03 were recovered, taken to dryness on a steam bath, digested at 80 OC in 50% H,S04/10% Hz02as described in EPA reference method 12 (3),diluted to volume, and analyzed for metals by flame atomic absorption. (2) Test 2, Plant A. The acetone rinses were evaporated to dryness in tared beakers at ambient temperature and desiccated along with the filters for 24 h, and then all samples were brought to constant weight as in test 1. All samples were then heated for 3 h at 160 "C, for 24 h at 188 OC, and then for 24 h at 316 OC with the samples brought to constant weight between heatings. The IPA portion of the sampler train was analyzed for sulfate as in the first test. The HzOzsamples were not analyzed. (3) Test 3, Plant B. A t the end of each day's testing all particulate samples were placed in a desiccator. In the morning, most of the particulate filters were tared and then sequentially heated for 24-h periods at 160,232, and finally 316 "C with the samples brought to constant weight between heatings. All probe rinses were taken to dryness at low heat (approximately 24 h), were weighed, and then most were immediately placed in the muffle furnace and subjected to the above heating procedure. However, to see if chemical reactions occurred between the particulate and any collected H2S04or absorbed SO2,four filters and their
Table 11. Precision of Reference Method 5 Sampler at Plant B as a Function of Conditioning Temperature (To)
T,,"C 20
160
232
316
range in probe/filter,
OCb
161-167/165-171 162-166/154-162 164-174/149-174 163-167/160-168
1
reference method 6 sampler," mg/m3 2 3
37.6 (25) 55.3 (13) 35.0 (32) 22.9' (22) 25.8 35.8 31.5 15.lC 25.4 34.9 26.9 12.5' 21.4 34.1 26.0 10.3c
52.9 (19) 42.8 (26) 60.gC(2) 19.8 (11) 19.7 34.9 34.4c 15.2 18.6 33.3 32.6c 11.2 15.6 33.4 29.1' 10.3
58.6 (a)* 56.4c (16)* 57.7 (2)* 33.8 (2)* 20.7* 40.4* 40.4* 24.8* 19.2* 40.3* 32.1* 13.1* 16.8* 37.3* 32.2* 12.1*
within run values 4
mean
S
51.OC(2) 52.6 (17)* 55.7 (20) 34.9 (2) 20.0c 41.4* 41.9 27.9 17.7c 33.6* 32.6 19.3 15.OC 31.4* 32.7 16.4
50.0 (14) 51.8 (18) 52.3 (14) 27.9 (9) 21.5 38.1 37.0 20.8 20.2 35.5 31.0 14.0 14.7 34.0 30.0 12.3
10.3 (10) 6.2 (6) 11.8 (15) 7.6 (9) 2.9 3.2 5.0 6.6 3.5 3.2 2.8 3.6 6.9 2.4 3.1 2.9
%
cv
21 (64) 12 (33) 22 (100) 27 (100) 13 8 13 32 17 9 9 26 46 7.6 10 24
Value in parentheses is amount of H2S04(in mg/m3) collected in IPA impinger. Range in average probe and filter temperature between all four samplers. Asterisk means that difference between probe midpoint and exit exceeded 15 "C. CThissample stored in desiccator for 7 days before initial weight obtained.
evaporated probe rinses were stored in the desiccator at room temperature for 7 days before being subjected to the heating procedure. The remaining eight filters were extracted with 100% IPA and after dilution to 80% P A , the IPA was analyzed for SO-: by using the BaC104titration procedure. The filters were then subjected to the above heating procedure to see if additional weight loss occurred. This was done to see if IPA effectively removed H2SO4 from the particulate. Due to the large volume of water collected during sampling, it was impossible to dilute the IPA samples to 80% by volume even with 100% IPA and still remain in the working range of the titration procedure. So, these samples were taken nearly to dryness at low heat, diluted to 100 mL with 80% IPA, and analyzed for SO-: by the BaC104 titration procedure. (Prior tests with HzS04-containing IPA solutions showed that H2SO4 was not lost under these conditions.) The H202samples were diluted with 100% IPA and analyzed for S042-as in the first test. Quality Assurance Procedure. All sampling equipment was calibrated before the test. The method 5 sampling consoles (meter boxes) were calibrated on site by using a critical orifice, and the thermocouples and nozzles were calibrated in the laboratory. All samplers and all pitot tube lines were leak checked before and after each sampling run. Field blanks were collected before each run by washing the probe and fiiter holder with acetone. Audit samples supplied by U.S. EPA, Research Triangle Park, NC, were used to confirm the accuracy of the sulfate analysis. The Method of Standard Additions (sample spiking) was employed to check for interferences on the sulfate analysis, and National Bureau of Standards traceable weights were used in all weighings.
Results and Conclusions Tables 11-IV present the particulate and corresponding H2SO4 concentrations (in parentheses) measured by each sampler. Table I1 presents the results from plant B (ESP/SOZscrubber) for the four sampling periods (runs) when all four samplers used out-of-stack filters (method 5) operated at reference method 5 conditions (160 OC for probe and filter). Also presented in Table I1 is the within-run, between sampler precision as estimated by the standard deviation, s, and the percent coefficient of variation, % CV (s/mean X loo), for the particulate and HzSO4 concentrations measured. The effect of heating on
the particulate concentrations measured is also shown in this table. Table I11 presents concentrations measured in the other 12 runs in which all four samplers were of the method 5 design (heated, out-of-stack filter). This table shows the effect of probe and filter sampling temperature on the particulate and H2S04(in parentheses) values. Table IV presents similar data for those runs where two samplers were equipped with in-stack filters. Tables I11 and IV also show the average temperature maintained in the probe and filter holder for each sampler. Because probe and filter sampling temperatures were critical variables in this study, these temperatures were continuously monitored and adjusted during sampling to keep them within the target range. Filter holder temperature rarely varied more than f 5 OC during a sampling run, and average probe temperature rarely varied less than *lo "C. However, certain probe liners consistently showed a 15-25 "C temperature gradient between the midpoint and exit temperature sensors throughout a run. These latter probes, identified by an asterisk in Tables 11-IV, were operated whenever possible to maintain an average temperature within the target range. Unfortunately, these nonhomogeneous temperature profiles are common in glass-lined probes (4). Tables V and VI show the effect of heating on the particulate concentrations for the method 5 (Table V) and in-stack (Table VI) samplers, respectively. The values in these tables represent the average concentration measured by each type of sampler. If one of the samples in a pair was missing, one of the values for the opposite pair in that run was arbitrarily excluded for the purpose of calculating the average. This was done because the mean concentrations sometimes varied widely from run to run. (The number of values used to construct each average is shown in parentheses in these two tables.) The values in Table I1 (reference method 5 sampler followed by a dry impinger and method 8 impingers) show that the precision (% CV) obtained with this combination sampler is considerably worse than the precision associated with the individual samplers. For example, the average % CV for the particulate measurement after ambient desiccation in this study (20%) is 3 times larger than that observed in tests at a municipal incinerator (1, 7). Similarly the average % CV for the H2S04measurement in this study (75%) is 3 times larger than that observed in tests Environ. Sci. Technol., Voi. 18, No. 10, 1984
805
Table 111. Effect of Sampling Temperature on Out-of-Stack Sampler Particulate and HzSOl Measurements sampling
reference Method 5 sampleP probelfilter, O C b
mg/m3
1
156
3
159
5
157
7
161
-1 166 -1156 1251166 1861153 1351163 1841156 1361163 1881152
22.6 (29) 19.3c (26) 44.1 (34) 36.P (44) 26.7 (35) 19.2c (44) 42.5 (37) 23.7c (52) 29.4 (37)
-1 105 -1105 1061104 104/107 1231101 118/105 1061102 100/111
78.5 (10) 78.7c (5) 114 (13) 114c (11) 71.9 (6) 73.3c (6) 91.5 (10) 95.3c (61 89.6 (8)
8
159
10
162
1611163 1621160 1621160 1621154
24.8 (41) 16.3 (39) 21.9 (60) 21.1 (59) 21.0 (50)
1271128 1281133 1291133 1271128
43.3 (22) 74.4 (11) 52.6 (44) 87.5 (16) 64.5 (23)
9
152
1711157 1481164 1841153 1591157
27.3 d 20.7 36.0 28.0
-1-
d 14.6 18.8
38.5c (22) 43.3 (11) 25.4 (24) 21.7 (27) 24.7 (30) 21.2 (36) 20.7 (16) 21.1 (121 25.4 (22)
136*/91 136199 170*/98 160*/ 128 1591111 160*/96 1521113 1691101
run
1A
156
11
3B
other method 5 samplern
T,,O C
test
5
94
6
88
7
91
9
83
1671168 1751177 163*/160 1601172 178*/165 1831163 160*/161 1661160
probelfilter,
OCb
2481175 191/190 2491174
mg1m3
11.0 14.8 d 49.0 (2) 40.8 (8) 24.1 (25) 85.9 (3) 102.4 (3) 40.7 (1) 46.1 (1) 55.6 (6)
'Value in parentheses is amount of HzSOl (in mg/m3) collected in the IPA Impinger. In sampling runs 9 and 11the impingers contained "OB. bAverageprobe and filter temperature for sample. Asterisk means that difference between probe midpoint and exit exceeded 15 O C . cValue not used in calculating average shown in Table V. Sample lost because of equipment failure or breakage.
Table IV. Comparison of Out-of-Stack (Reference Method 5) and In-Stack Sampler Measurements reference method 5 results' test
run
T,,O C
1A
2
158
4
159
6
159
1
162
3
157
2A
2 4
3B
162 161
8
87
10
86
probelfilter,
mg/m3
OCb
probelfilter,
-1162 -1159 1571164 1611159 1581162 1561159
28.2 (33) 17.3 (41) 37.0 (-) 47.1 (-) 20.5 (46) 26.2 (33) 29.4 (38)
-1158 -1 158 -1159 -1159 -1159 -1159
1561157 189*/167 1611157 1631156
57.4 (43) 52.4 (34) 35.4 (32) 39.3 (25) 46.1 (34)
1621162 1591162 1611157 1561157
1641163 1701162 1661163 1671160 1621170 1711164 1581160 1641162
46.9 47.4 36.2 37.6 42.0
in-stack samDler results' BGI-T, mg/m3 mg/m3
BGI-U,
~
OCb
17.0 (26) 25.7 (29) 31.7 (22) -'(18) 24.8 (24)
RA934, w/m3
37.7 (28) 40.7 (22) 55.7 (-) 66.0 (-1 42.1 (38) 40.0 (26) 47.0 (28) 53.0 (33) 53.4 (41) 24.7 (29) 38.9 (31)
27.9 (28) 40.7 (34)
55.3 (29)
(-)
(25) (33) 31) (30)
AL, mg/m3
1721162 1511161 1621161 65/87 158187 166186 142186
71.0 (19) 48.2 (28) 66.0 (16) 68.5 (18)
51.8 (28) 43.0 (10) 52.5 (8) 61.7 (8) 69.V (11) 52.4 (10)
OValue in parentheses is amount of H2S04(in mg/m3) collected in IPA impinger. bAverage probe and filter temperature for sample. Asterisk means that difference between probe midpoint and exit exceeded 15 O C . In test 1A the temperature of the in-stack filter probe was not recorded. In-stack filter is assumed to be at stack temDerature. Value not used in Calculating average.
at a sulfuric acid plant (8). However, the precision in the SO2measurement (plant A,3.9% CV) and plant B (1.5% CV) compares favorably with the 3% CV obtained for method 8 at the sulfuric acid plant (8). Thus, although 808
Envlron. Scl. Technol., Vol. 18, No. 10, 1984
the combination sampler will not yield precise H2S04 concentrations, it may be possible to use it to simultaneously measure particulate and SO2. The results of this study demonstrate how important
Table V. Effect of Conditioning Temperature on Method 5 Samples Collected at Different Temperatures (mg/mJ) condi- reference test/ tioning method 5 other method 5, mg/m3 plant temp, O C 160 O C " 100 O C " 104 O C " ' 130 O C " 190 O C " 1A
20 160 188 20 160 188 20 160 188
3B
20 160 232 316
29.4 (4) 19.6 14.9 21.0 (4) 14.5 12.8 28.0 (3) 17.9 15.1 25.4 (7) 14.9 15.6 13.0
89.6 (4) 37.1 17.1 64.5 (4) 31.0 20.7 14.8 (3) 11.9 11.0 55.6 (7) 26.3 24.5 22.9
" Approximate filter and probe temperature during sample collection. Table VI. Effect of Conditioning Temperature on Reference Method 5 and In-Stack Sampler Particulate Concentrations (mg/ms) condiav tioning reference test temp, "C method 5 1A
2A
3B
20 160 188 20 160 188 316 20 160 188 316 20 160 232 316
29.4 (6) 17.9 14.9 46.1 (4) 40.2 37.6 36.6 42.0 (4) 37.0 35.0 34.1 24.8 (3) 19.0 17.0 15.7
average in-stack sampler results BGI-U BGI-T AL RA934 47.0 (6) 40.5 38.3 38.9 (2) 36.9 34.5 34.5
40.7 (2) 38.8 37.1 36.9
68.5 (2) 51.7 (2) 47.8 58.6 41.2 55.5 53.4 33.8 52.4 (3) 35.0 33.8 32.0
it is to accurately monitor and control the temperature of the method 5 sampler at combustion sources where H2S04 is present in the stack gas. The concentrations measured here and elsewhere ( 4 ) demonstrate the inability of the present heatable sampling probe design to maintain this type of temperature control and to provide a uniform temperature profile in the probe. Note, for example, that in those tests in which all samplers were reference method 5 (Table 11,test 3B) certain samplers collected considerably less particulate and more H2S04 than the other samplers in that run. This occurred despite the fact that all probes and filters were operated at a temperature 30 "C above the acid dew point. Further, the samples with the low particulate result lost proportionally less weight on heating (Table 11). Inspection of the method 5 type sampler data in Tables 11-V shows that as the probe and filter temperature increased, the amount of sulfate measured in the IPA impinger portion of the sampler increased. That this material was H2S04 and not a volatile inorganic sulfate (e.g., (NH4)2S04)is shown by ion chromatographic analyses of selected IPA samples from test 1. These analyses, conducted on samples taken to near dryness on a steam bath and then reconstituted with water, found that S042-was the only ion present in significant quantities. The data in Tables IV and VI show that at the ESP only plant (plant A) the Alundum thimble and RA 934AH flat
filter (when used in the in-stack position) measured on the average partculate and H2S04concentrations that agreed quite well with the out-of-stack sampler. However, as would be expected from the work of Peters and Adams (5) the borosilicate glass-fiber thimble (BGI) measured a particulate concentration considerably higher than that for reference method 5 and a H2S04concentration lower than reference method 5 (see Table IV, test 1A). Treating this thimble with H2S04(BGI-T) decreased these differences in both the particulate and H2S04measurements (Table IV, test 2A), but it was still necessary to heat the BGI-T sample above 188 "C before close agreement was obtained (Table VI, test 2A). In contrast, heating the untreated BGI thimble at 316 "C was not effective in removing the difference in the particulate catch (Table VI, test 2A). At plant B (ESP and scrubber) the in-stack filter sampler (Alundum ceramic filter) measured particulate concentrations considerably higher and H2SO4 concentrations considerably lower than reference method 5 (Table IV, test 3B). Further, heating the in-stack samples to 316 "C did not remove these differences. The results of this study also showed the following: (1) Heating the sample at the sampling temperature specified in the regulation may not completely compensate for cases in which the method 5 probe and filter were operated at temperatures below those specified in the regulation. For example, heating plant A method 5-type particulate samples collected at 104 and 130 OC for 8 h at 160 "C did not bring them into agreement with the reference method 5 samples (Table V, test 1A). Heating the samples to 316 "C,however, did improve the agreement dramatically. On the other hand, large differences between plant B method 5 samples collected at 100 "C and those collected at 160 "C still existed when the samples were heated to 316 "C (Table V, test 3B). (2) Extraction of particulate samples by IPA has been suggested as a means to remove collected H2S04. However, the results from this study show that this extraction technique was not suitable for samples from either plant, but for different reasons. For example, when reference method 5 samples from plant A were extracted with IPA, the average weight of sulfate extracted was 22 mg whereas corresponding reference method 5 samples when heated at 232 "Cwithout extraction lost 44 mg. Similarly, when out-of-stack filter samples collected at 104 "C were extracted with IPA, the average weight of sulfate recovered was 140 mg whereas corresponding samples when heated at 232 "C without extraction loss 220 mg. (The presence of water of hydration with the H2S04may explain the 2-fold difference observed here, but there is no basis to assume that the amount of water would remain constant from plant to plant.) Further, out-of-stack filter samples collected at approximately 100 O C at plant B yielded only 4.3 mg of sulfate after IPA extraction but then lost 39 mg when heated at 232 "C. The amount lost from these extracted samples on heating (39 mg) compares closely with the 33 mg lost when analogous samples collected at 160 "Cwere heated to 232 O C without P A extraction. At plant B the large difference between the H2SO4 collected in the out-of-stack samplers operated at 160 O C (22 mg) and those operated at the lower temperature (6 mg) indicate that H2SO4 was collected with the particulate in these latter samplers (Table 111, test 2B). (3) Plant B particulate samples collected by reference method 5 and stored for 7 days before being heated were not statistically different from samples heated within 16 h of collection. Thus, if adsorbed SO2, sulfite material, or H2SO4 reacted with the basic particulate to yield an inEnviron. Sci. Technol., Vol. 18, No. 10, 1984
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Environ. Sci. Technol. 4984, 18, 808-810
organic sulfate, the reaction occurred either during sampling or shortly after sampling was completed (Table 11). (4) Analysis of the dilute “OB solutions from test 1, runs 9 and 11, detected only minor quantities of three transition metals: Cr (1 pg/m3), Mn (1pg/m3), and Ni (16 pg/m3). The values for all metals were the same for both the 160 and 188 “C samplers and represent only 0.02-0.6% of the total particulate catch. Overall, the results indicate that the Alundum ceramic thimble and the Reeve Angel 934AH filter may be suitable substitutes for reference method 5 when coal-fired power plant stacks with temperatures near the 160 “C sampling temperature specified in the regulations (2) are sampled. They also show that these two in-stack filters should not be used at scrubber-equipped sources and that borosilicate glass-fiber filters should not be used at either source. Finally, until the required improvements to the probe temperature profile and temperature control are made, it seems prudent to report method 5 particulate results from these plants at two temperatures: after ambient desiccation and after heating for 3-24 h at the sampling temperature specified in the regulation. While this approach would not completely compensate for errors in the probe and filter sampling temperatures, it could identify instances where an unusually high or low particulate value (in a series of tests) was caused by an undetected malfunction or calibration error in the heating systemts). Of course, if this approach was used, the filter should be conditioned before use at the highest temperature at which the sample will be conditioned. Registry No. SO2, 7446-09-5; H2S04, 7664-93-9; alumina,
10,85-88. (2) U.S. Environmental Protection Agency. Code of Federal Regulations, Title 40, Part 60, Subparts D and Da. (3) U.S. Environmental Protection Agency. Code of Fereral Regulations, Title 40, Part 60, Appendix A, Reference Methods. (4) Peters, E. T.; Adam, J. W. “Evaluation of Stationary Source Particulate Measurement Methods: Gas Temperature Control During Method 5 Sampling”; U.S. Environmental Protection Agency: Research Triangle Park, NC, 1979; EPA-600/2-79-115, Vol. 111, (available from the National Technical Information Service, Springfield, VA, as Report P B 300336). (5) Peters, E. T.; Adams, J. W. “Sulfur Oxides Interaction with Filters Used for Method 5 Stack Sampling. Workshop Proceedings on Primary Sulfate Emissions from Combustion Sources: Measurement Technology”; U.S. Environmental Protection Agency: Research Triangle Park, NC, 1978; EPA-600/9-78-020a, Vol. I, pp 199-202 (complete report available from the National Technical Information Service, Springfield, VA, as Report P B 287436). (6) Barton, S. C.; McAdie, H. G. Environ. Sci. Technol. 1970, 4, 769-770. (7) Hamil, H.; Thomas, R. “Collaborative Study of Particulate Emission Measurements by EPA Methods 2,3, and 5 Using Paired Particulate Sampling Trains (Municipal Incinerators)”; U.S. Environmental Protection Agency: Research Triangle Park, NC, 1976; EPA 600/4-76-014 (available from National Technical Information Service, Springfield, VA, as Report P B 252-028/6). (8) Mitchell, W. J.; Midgett, M. R.; Suggs, J. C. a t o m . Environ. 1979, 13, 179-182.
1344-28-1.
Literature Cited (1) Mitchell, W. J.; Midgett, M. R. Environ. Sci. Technol. 1976,
Received for review July 29,1983. Revised manuscript received May 10,1984. Accepted May 16,1984. This work was supported through EPA Contract 68-02-3737.
NOTES Linear Correlation between Photolysis Rates and Toxicity of Polychlorinated Dibenzo-p-dioxins Andrew Mamantov U.S. Environmental Protection Agency, Offlce of Pestlcldes and Toxic Substances, Washington, DC 20460
rn Linear correlations have been detected between the photolysis half-lives of polychlorinated dibenzo-p-dioxins (in n-hexadecane solution) and (a) the LD50 values (of guinea pigs and chick embryo, r = 0.98) and (b) the relative biological potency values (derived from ED50 values, rat hepatoma cell, r = -0.7 to -0.8). These correlations are surprising in view of the wide disparity between a photolysis reaction and a biological end point. It is difficult to avoid considering the possibility of a common or related reactive intermediate in the photolysis reaction and the biological end point.
Introduction The polychlorinated dibenzo-p-dioxins (PCDDs) are members of the large class of halogenated aromatic com808
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pounds. The mechanism of biological activity and toxicity of the PCDDS has not been entirely elucidated (1). Other halogenated aromatic compounds, structurally related to the PCDDs, include the polyhalogenated biphenyls, biphenyl ethers, dibenzofurans, azobenzenes, azoxybenzenes, and naphthalenes which also elicit varying degrees of toxicity. This has led several groups of investigators to postulate a similar mechanism of toxicity for these compounds (1-3). It is generally accepted that PCDDs bind to a biological receptor, a hepatic cytosolic protein in the cytoplasm of the target cells. This complex is transported into the nucleus where it activates a set of genes representing the locus. These genes aryl hydrocarbon hydroxylase (A”) produce messenger RNAs that direct the synthesis of cytochromes P-450 and P-448.
Not subject to U.S. Copyright. Published 1984 by the American Chemical Society
