Figure S1: Influence of relative humidity on acetic acid fragmentation

Transcription

1 Supporting information for the article: Odorant emissions from intensive pig production measured by online Proton-Transfer-Reaction Mass Spectrometry Anders Feilberg *a, Dezhao Liu a, Anders P. S. Adamsen a, Michael J. Hansen a, Kristoffer E. N. Jonassen b a Department of Biosystems Engineering, Aarhus University, Blichers Allé 2, DK-883 Tjele, Denmark b Danish Agriculture & Food Council, Pig Research Centre, Axeltorv 3, DK-169 Copenhagen, Denmark * Corresponding author. Phone: (+45) anders.feilberg@agrsci.dk Contents: Uncertainty estimates Table S1: List of estimated sensitivities Table S2: Relative transmissions before/after measurements Table S3: Additional masses observed in scan mode Table S4: Quantitative measurements by TD-GC/MS Table S5: Additional compounds identified by GC/MS Table S6: Fragmentation patterns of selected compounds Table S7: Correlations with NH 3 and room temperature Figure S1: Influence of relative humidity on acetic acid fragmentation Figure S2: Acetic acid determined from m/z 43 + m/z 61 versus acetic acid determined from humidity and fragmentation-corrected m/z 61. S1

2 Figure S3-S6: Examples of concentration vs. time data for the whole measurement period Figure S7-8: Diurnally averaged emission data vs. time Figure S9-S1: Correlations of emissions vs. ventilation rate Figure S11A-B: Relationships of selected compounds and ventilation rate versus room temperature. This document contains 7 Tables, 11 Figures and 16 pages in total. S2

3 UNCERTAINTY ESTIMATES The uncertainty in absolute concentration of compounds for which gas standards and permeation tubes were available is due to the uncertainty in standard concentration, the uncertainty due to long term instrumental drift (estimated to be ±1% on average, see Table S5) and variation in repeatability. The uncertainty due to drifting can be eliminated by doing frequent calibrations on-site. By error propagation the overall uncertainty in concentration is determined to be within the range of ±1-2%. For compounds for which the sensitivity was calculated, the uncertainty is mainly due to a combination of the uncertainty in the rate constant, the uncertainty due to transmission factor drift (estimated to be within ±1%) and variation in repeatability. Calculated rate constants have previously been reported to agree with experimentally measured rate constants within an uncertainty of ±1-15% (1,2). By comparing experimental and calculated values for MT, DMS, acetone, acetic acid and phenol, the rate constant uncertainties are estimated to be in the range of ±4-23%. By error propagation, the overall uncertainty in concentration measurements based calculated sensitivity is estimated to be in the range of 1-26%. The error estimation is based on the assumption that compound assignment to mass is unambiguous. Additional uncertainty should therefore be considered for those compounds for which this is not the case, e.g. phenol. The primary ion (H 3 O + ) was not observed to be suppressed at the concentrations of NH 3 in the ventilation duct (typical levels of 1-6 ppm and a few periods with peak values of ~1 ppm) and the concentration measurements should therefore not be affected by NH 3. S3

4 Table S1. List of estimated sensitivities based on proton-transfer rate constants and transmissions relative to H 3 O +. Compound m/z k (cm 3 molecule -1 s -1 ) Sensitivity (ncps ppb -1 ) Methanethiol E-9 17 Acetone E Trimethylamine E-9 86 Acetic acid E Dimethyl sulfide E butanone E Propanoic acid E ,3-Butanedione E-9 7 Butanoic acid E Phenol E C5 carboxylic acids E Methylphenol E Indole E Ethylphenol E-9 98 Dimethyl trisulfide E Fragmentation of carboxylic acids were included in the calculations Table S2. Transmissions relative to m/z 21 before/after the field measurements for masses included in the transmission standard mixture. Higher masses (m/z > 146) are not relevant for this work and have been omitted. Mass Compound T(VOCH + )/T(H 3 O + ) (initial) T(VOCH + )/T(H 3 O + ) (after) % difference 79 Benzene Toluene Styrene C 8 -aromatics Chlorobenzene Trimethyl S4

5 benzenes Table S3. Additional masses (lower limit thresholds:.2 ppb v ; k av = cm -3 molecule -1 s -1 ) observed in daytime full-scan measurements with compound assignments, concentration ranges and potential interferences. Mass Contributing compounds Concentration range(ppb v ) Comment 33 Methanol 2 4 ~2% from O 16 O Alcohols (fragments) 1 2 See Table S4 42 Acetonitrile.5 1 Tentative 1 44 Acetic acid (C 13 -isotope) See Table 1, main article ~2.5% of mass Acetaldehyde Dimethylamine or ethylamine.5 4 Tentative 1 47 Ethanol + formic acid 1 5 See Discussion, main article 51 Methanethiol (S 34 -isotope) See Table 1, main article 58 TMA fragment See Table 1, main article 62 Acetic acid (C 13 -isotope) See Table 1, main article ~2% of mass Unknown.2 2 Likely to contain nitrogen 69 3-Methylbutanal (fragment).5 1 Contribution from isoprene? 72 Butanoic acid (C 13 -isotope) See Table 1, main article ~4.5% of mass Unknown.2.5 Likely to contain nitrogen 76 Propanoic acid (C 13 -isotope) See Table 1, main article ~3% of mass Propanethiol.2.5 Tentative 1 79 Benzene + DMDS fragment Terpenes (fragment) Hexanal (fragment) Butanoic acid (C 13 -isotope) See Table 1, main article ~4.5% of mass Toluene Furfural C 5 acids (C 13 isotope) See Table 1, main article ~6% of mass Benzaldehyde.5 2 Contribution from C 8 aromatics 11 4MP (C 13 isotope) See Table 1, main article 117 Hexanoic acid Not confirmed by GC/MS screenings or other previous measurements S5

6 Table S4. Comparison of quantitative measurements by TD-GC/MS (3 replicates per date) and PTR- MS (averaged for the sampling period) for three days during the campaign. All results are presented as average (in ppb) ± 1 standard deviation based on replicates (TD-GC/MS) or consecutive measurements (PTR-MS). June 2 June 9 June 23 Compound (Ions for PTR-MS) Acetic Acid (m/z ) Propanoic acid (m/z ) C 4 -acids (m/z ) C 5 -acids (m/z ) 2,3-butanedione (m/z 86) PTR-MS TD-GC/MS PTR-MS TD-GC/MS PTR-MS TD-GC/MS 112.6± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±.4 3.4±1.8.9±.1 1.±.6 1.3±.1 1.5±1.2.9±.1 1.6±1.5 Phenol (m/z 95) 1.39±.3.9±.2.55±.4 1.4±.4.89±.6 1.4±.5 4-Methylphenol (m/z 19) 4-Ethylphenol (m/z 122) Indole (m/z 118) 3.1±.3 5.3± ±.3 8.± ±.3 8.8±4.5.26±.2.4±.2.37±.2.4±.3.36±.2.5±.2.1±.1.2±.1.14±.1.1±.1.12±.1.2±.1 3-methyl-1Hindole (m/z 132).21±.2.9±.7.34±.4.1±.1.24±.4.2±.1 1 Includes dimethyl disulfide S6

7 Table S5. Compounds identified by TD-GC/MS with approximate concentration levels estimated by comparison with compounds for which the method was calibrated by standards. Concentration ranges are estimated by comparison with quantified compounds included in Table S2. Compound Molecular weight Estimated concentration range (ppb) 2 Dimethyl sulfide Dimethyl disulfide Ethanol Propanol Propanol Butanol Pentanol methyl-1-butanol Acetone Butanone Nonanal Trimethylamine C 1 -terpenes Acetonitrile Benzonitrile Benzene Toluene C 8 -aromatics Styrene Partly originates from oxidation of methanethiol during sampling. 2 Potential sorbent tube breakthrough of the most volatile compounds has been disregarded. S7

8 Table S6. Fragmentation of selected compounds based on direct PTR-MS headspace analyses of pure standards. PTR-MS fragments are shown as ions with contributions (in percent) relative to highest peak. Settings including E/N-values were similar to other measurements. Compound Molecular weight PTR-MS fragmentation Dimethyl disulfide (1), 79 (32), 97(1) 1-Propanol (1), 42(4), 43(91), 44(4), 61(1) 2-Propanol (1), 42(5), 43(98), 44(4), 61(2) 1-Butanol (1), 41(29), 58(5), 43(2) 1-Pentanol (1), 42(4), 43(94), 44(4), 57 (14), 71(52), Hexanal (1), 11(7), 84(6), 55(94), 56(5), 45(18) Table S7. Linear orthogonal regression data for correlations between selected compound emissions measured by PTR-MS and 1) emissions of NH 3 and 2) room temperature (normal regression, hourly averaged). Compound NH 3 correlation data T room R 2 Slope Intercep t R 2 H2S MT Acetone TMA Acetic acid DMS Propanoic acid Butanoic acid C 5 acids Methylphenol Ethylphenol S8

9 ) 12 1 Concentration (ppb Relative humidity (%) Figure S1. Measurements of a diluted acetic acid standard generated from a permeation device as a function of relative humidity ( : m/z 43 (fragment ion); : m/z 61 (protonated parent molecule); : m/z 43 + m/z 61). m/z 43 + m/z 61 (ppb) y = 1.41x R 2 = m/z 61 corrected (ppb) Figure S2. Plot of of acetic acid concentration quantified by summing m/z 43 and m/z 61 versus acetic acid concentration quantified by correcting m/z 61 for humidity and fragmentation according to the data presented in Figure S1. All field data is included (n=6374). S9

10 Concentration (ppb) Date H2S concentration (ppb) Figure S3. Outlet concentrations of H 2 S (full black line), acetic acid (dashed line) and butanoic acid (grey line). 25 Concentration (ppb) Date S1

11 Figure S4. Outlet concentrations of trimethylamine (grey line) and methanethiol (black line). Concentration (ppb) Date Figure S5. Outlet concentrations of dimethyl sulfide (grey line) and 4-methylphenol (black line) C5 acids (ppb) Date 1,8 1,6 1,4 1,2 1,8,6,4,2 3-methyl-1H-indole (ppb) S11

12 Figure S6. Outlet concentrations of C 5 -acids, pentanoic acid and 3-methylbutanoic acid (grey line) and 3-methyl-1H-indole (black line) VR (m3 h -1 ); Emission (mg h -1 ) Emission, MT/4MP (mg h -1 ) Date Figure S7. Examples of temporal variation in emissions from the pig section during a one-month period presented as 24-hour average values for H 2 S ( ), MT ( ), BA ( ) and 4MP (Δ) together with daily averaged ventilation rates (VR; ). Emission (mg h -1 ) Date Emission (mg h -1 ) S12

13 Figure S8. 24h-averaged emission rates. Left y-axis: C 5 acids ( ) and DMS ( ). Right y-axis: 4- ethylphenol ( ) and 3-methyl-1H-indole (Δ) R 2 =, Emission (mg h -1 ) R 2 =, Emission (mg h -1 ) 1 R 2 =, Ventilation rate (m 3 h -1 ) Figure S9. Diurnally averaged emission data versus diurnally averaged ventilation rates for the period from June 6 to June 25 shown for selected compounds. Left y-axis: Propanoic acid ( ) and C 5 -acids ( ). Right y-axis: 4-ethylphenol (Δ). Full lines represent linear regressions of the data. S13

14 6 5 R 2 =.5 Emission (mg h -1 ) R 2 =.77 R 2 = Ventilation rate (m 3 h -1 ) Figure S1. Diurnally averaged emission data versus diurnally averaged ventilation rates for the period from June 6 to June 25 shown for selected compounds: Acetone ( ), trimethylamine ( ) and dimethyl sulfide (Δ). Full lines represent linear regressions of the data. S14

15 4-Methylphenol emission (mg hour -1 ) A R 2 = Ventilation rate (m 3 hour -1 ) Methanethiol emission (mg hour -1 ) B Temperature (Celsius) 3 25 R 2 = R 2 =.16 5 Acetic acid emission (mg hour -1 ) Temperature (Celsius) Figure S11A-B. Variation of ventilation rate ( ) as a function of room temperature together with variations of selected compounds as a function of temperature. Compounds: Acetic acid ( ), MT ( ), and 4MP (Δ). All data are hourly averaged values. Full lines represent linear regressions of the data. S15

16 Literature Cited 1. Hewitt, C. N.; Hayward, S.; Tani, A. The application of proton transfer reaction-mass spectrometry (PTR-MS) to the monitoring and analysis of volatile organic compounds in the atmosphere. Journal of Environmental Monitoring. 23, 5 (1), Lindinger, W.; Hansel, A.; Jordan, A. Proton-transfer-reaction mass spectrometry (PTR-MS): on-line monitoring of volatile organic compounds at pptv levels. Chemical Society Reviews. 1998, 27 (5), S16