- Case Study -- Case Study -

VOC and RSC SamplingVOC and RSC Sampling

at Downtown Fire Hall for an Odour Event 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: Occasional odour complaints during cold winter days when atmosphere is stable.

• Objective: To investigate the potential sources of odours.

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).

AIC

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

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• 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 AMS

Rail y

ard

A

B, C

D, E

NPRI Sources Near Mirror

4 km approx.

Nevis Booster Compressor

7 km approx.

Nevis Gas Plant

RSC Results

• 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.

• 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.

• 21 minor VOC species

VOC Profiles

• 28 VOC species were detected

Total VOC = 7.3 ppb.

• 7 major VOC species

TolueneBenzene

Isobutane

Butane

Isopentane

Pentane

Freon-11

Downwind of rail yard, with active rail yard activities

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

Upwind of rail yard

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) .

Benzene

• 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

Toluene

• 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

• 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.

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

Minor VOC Species

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

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

Conclusion

• Major VOC species – Most VOCs were associated with multiple sources.

– Benzene: traffic emission and petroleum fuel combustion

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

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

• 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.

• SO2 conc. was maximum of the day – Potential link with diesel locomotive emission.

THC Time-Series Data (Fire Hall)

01:00

23:00

02:00

04:00 04:0004:00

23:00

0

1

2

3

4

5

6

7

8

THC

Conc

. (pp

m)

DATE

• 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)

• 2011 80% daily maximum was detected between 8 pm and 7 am• 2012 75% daily maximum was detected between 8 pm and 7 am.

Questions & Discussion