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- Case Study - VOC and RSC Sampling at Downtown Fire Hall for an Odour Event. Introduction. Response: - Three-month monitoring during the winter 2010-2011. - Canister sampling when odour was perceived. Problem:

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- Case Study -

VOC and RSC Sampling

at Downtown Fire Hall for an Odour Event


  • Response:

    - Three-month monitoring during the winter 2010-2011.

    - Canister sampling when odour was perceived.

  • Problem:

    Occasional odour complaints during cold winter days when atmosphere is stable.

  • Objective:

    To investigate the potential sources of odours.

Data at crescent heights station
Data at Crescent Heights Station

  • Atmosphere conditions:

    - Temperature: -17°C, increasing from midnight of -22°C.

    - Wind: Low wind speed ~3-4 km/hr from SW direction.

    - Upwind sources: CPR rail yard and downtown business/traffic

  • Air Pollutants:

    - SO2: 3 ppb, maximum of the day (baseline conc. <1 ppb).

    - Locomotive diesel contains higher sulphur (max 500 mg-S/kg) than

    on-road diesel fuel (max 15 mg-S/kg).

    - Normal conc. pattern for the other pollutants (NOx, CO, THC, O3, PM2.5).

06:22 am: 3 ppb, max. of the day


Fire hall canister sample
Fire Hall Canister Sample

  • Canister Sample Information:

    - A grab sample was collected.

    - 06:22 am January 31, 2013 when an odour was perceived.

    - Sample was analyzed for

    Reduced sulphur compounds (RSC), and

    Volatile organic compounds (VOC).

  • Limitation:

    - Small sample size, n = 1.

    - Sample did not detect a unique signature species.

Data analysis
Data Analysis

  • Approach:

    - Compare to the Mirror rail yard study (AESRD, 2011).

    - Mirror is located approx. 50 km NE of Red Deer.

  • Advantages using Mirror data:

    - Simple flat terrain, few emission sources near Mirror.

    - The program collected both upwind & downwind samples.

    - Rail yard activities information was recorded.

Mirror study overview
Mirror Study Overview

Rail yard

B, C


D, E

Mirror AMS

Npri sources near mirror
NPRI Sources Near Mirror

Nevis Gas Plant

4 km approx.

Nevis Booster Compressor

7 km approx.

Rsc results
RSC Results

  • 22 RSC species were analyzed

  • – Only carbonyl sulphide(COS) conc. >DL; conc = 0.7 ppb.

  • – The conc. slightly higher than typical background of 0.5 ppb.

  • COS properties

    – Typical sulphide odour, like a rotten egg smell

    – Most abundant sulphur compound naturally present in atmosphere.

    – Anthropogenic sources:

    fuel combustion,

    petroleum processing,

    grain fumigation,

    fish processing.

Voc profiles
VOC Profiles

 Upwind of rail yard

 Downwind of rail yard, with active rail yard activities

 Downwind of the south rail yard, but little activities in this section

  • 28 VOC species were detected

  • Total VOC = 7.3 ppb.


  • 21 minor VOC species


  • 7 major VOC species






Major voc species
Major VOC Species

  • The major VOC species may be attributed to multiple sources

    - Detected in most samples (active & minimal yard activities)

    - Conc. not apparently higher for samples with active rail yard activities upwind (B,C vs. D,E) .


  • A higher benzene conc. in the Fire Hall sample than Mirror’s

    - In Canada, vehicle emission accounts for >80% of benzene in an urban area.

    - Traffic volume: City of Medicine Hat > Hamlet of Mirror

    - Other petroleum fuel combustion is another potential source of benzene.

2 ppb

<0.3 ppb


  • Similar concentrations (0.2 to 0.4 ppb) in all samples

    - Railyard operation might not be the sole emission source of toluene.

    - Toluene is a naturally occurring component of crude oil and petroleum.

    - Major anthropogenic sources in Alberta are O&G operation and cement manufacturing.

Isobutane butane freon 11
Isobutane, Butane, Freon-11

  • Only detected in the samples downwind of rail yards

    - Potential link with rail yard activities.

    Butane & isobutane: refrigerant, aerosol propellant, fuel blending.

    Freon-11: refrigerant, aerosol propellant.

Minor voc species
Minor VOC Species

Although low concentration, some species present a trend with wind pattern and rail yard activities.

Five species were detected in the samples when wind was from both active and less active rail yard.

Only methylcyclohexane was detected in the sample upwind of rail yard.


  • The VOC/RSC data did not find a unique signature specie

  • Major VOC species

  • – Most VOCs were associated with multiple sources.

  • – Benzene: traffic emission and petroleum fuel combustion

  • Minor VOC species

  • – Potential link with rail yards for a number of species.

  • SO2 conc. was maximum of the day

  • – Potential link with diesel locomotive emission.

  • In comparison with the 2010-2011 winter study (continuous monitoring)

  • – From source identification perspective, the timing evidences detected in the 2010-2011 study is more unique than VOC speciation.

Thc time series data fire hall
THC Time-Series Data (Fire Hall)

  • The timing evidence is unique from source identification perspectives

  • - few sources in downtown area operate actively during this period of time.

Timing for daily max thc ch station
Timing for Daily Max THC (CH Station)

  • 2011  80% daily maximum was detected between 8 pm and 7 am

  • 2012  75% daily maximum was detected between 8 pm and 7 am.