Briefing on Roxana Air Quality Study (RAQS)

Li Du, Jay Turner Washington University in St. Louis

Measurements Summary

• Air Toxics gases – 58 Volatile organic compounds (VOCs) and 13 carbonyl compounds – Methods: EPA TO-15 (VOCs), EPA TO-11A (carbonyls) – NATTS protocol and analytical lab

• PM2.5 speciation – gravimetric mass, 5 water soluble ions, 33 metals and carbon fractions – STN (CSN) protocol and analytical lab – additional in-house PM2.5 speciation for select elements by ICP-MS

Parameter(s) Frequency Start Date Analysis Lab

Air Toxics gases 1-in-6 day 06/08/2012 ERG

PM2.5 speciation 1-in-6 day 06/08/2012 RTI

H2S/SO2 5-minute Aug 2010 N/A

Meteorology 5-minute Sep 2010 N/A

RAQS Data in Context

• Compare RAQS data to City of St. Louis Blair Street station data (NATTS site, STN site)

• Both sites could have local influences, so difference represents the minimum local contribution at the higher concentration site

HOMOGENEOUS HETEROGENEOUS

Roxana > Blair Blair >Roxana

Carbon tetrasulfide Acrolein Acetylene

1,3,5-Trimethylbenzene n-Octane 1,3-Butadiene **

Chloromethane Propylene Methyl Isobutyl Ketone

Dichlorodifluoromethane Benzene Dichloromethane

Trichlorotrifluoroethane Ethylbenzene Chloroform

Dichlorotetrafluoroethane m,p-Xylene Trichlorofluoromethane

Propionaldehyde Toluene Valeraldehyde **

Hexaldehyde o-Xylene Crotonaldehyde **

1,2,4-Trimethylbenzene Acetaldehyde **

1,2-Dichloroethane Butyraldehyde

Benzaldehyde Formaldehyde**

Tolualdehyde ** Acetone

2-Butanone

Acetonitrile***

Spatial Variability*: Roxana vs. Blair

* Categorization using a Wilcoxon paired signed-rank test on the concentration distributions. Significance at the 95th percent confidence level. Compounds marked with (**) were homogeneous using a Kruskal-Wallis test. *** Dramatic change in concentration time series. Will confirm with ERG.

Excludes data collected at Roxana from June 2012 through December 2012 because of measurement artifacts for the carbonyls data

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Solid line: expected concentration at Roxana Dashed line: expected concentration at Blair Street (downtown St. Louis)

Benzene Toluene

n-Octane Propylene

Roxana excess = median of (Roxana minus Blair Street difference distribution) Regional contribution = median (Roxana) – Roxana excess

Spatial Variability: Roxana vs. Blair Estimate of local source contribution at Roxana,

assuming Blair Street represents regional contribution

Propylene Toluene Benzenem,p-Xyleneo-Xylene1,2,4-TrimethylbenzeneEthylbenzenen-OctaneBenzaldehydeTolualdehydes1,2-Dichloroethane

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Regional contributionRoxana excess

PM2.5 mass - Roxana

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Solid line: Roxana winds Dashed line: Lambert winds

PM2.5 mass is relatively homogeneous in the St. Louis region.

No directional pattern was observed at Roxana indicating no major sources.

Rare Earth Element (REEs) in PM2.5

• REEs (lanthanum and cerium in particular) are enriched in catalysts used in fluidized catalytic crackers (FCC)

• REEs exist in the crustal materials, such as soil and rock • REEs in the ambient PM2.5 could serve as tracers for refinery

FCC emissions – Method first proposed and demonstrated by the Chellam

group at University of Houston

• A manuscript was submitted on the topic to Science of the Total Environment.

The La/Ce ratios were bounded by the average ratio obtained from local soil at the low edge Higher La/Ce ratios indicate mixed sources from local soil and possibly FCC emissions

• PM2.5 samples collected every 1 in 6 day were analyzed in the lab for Rare Earth Elements (REEs) – La and Ce in particular

• Local soil samples were resuspended and analyzed following the same protocol as PM2.5 samples to establish the profiles of REEs in the soil.

PM2.5 samples (open circles)

Lanthanum and Cerium in PM2.5

Soil La/Ce ratio within 200 km of Roxana = 0.507 ± 0.049 (Data by USGS)

Nonparametric Wind Regression (NWR) on La, Ce and La/Ce La

La/Ce

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2012 For comparison… 1-hour SO2 NAAQS is 75 ppb (3-year average of annual 99th percentile)

Hourly SO2 at Roxana

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Nonparametric wind regression analysis indicates contributions from the main operation area (southeast) and the sulfur recovery unit (southwest).

2013 2014

Summary I Trends for gaseous air toxics compounds… • Modestly elevated concentrations for aromatics and other

petroleum related compounds were observed at Roxana compared to Blair Street

• Assuming Blair concentrations are representative of urban- and larger-scale concentrations, at Roxana local sources contribute up to 40% of the measured concentration (for those compounds that show higher concentration at Roxana)

• Wind regression results show evidence of aromatics and other petroleum related compounds from the direction of the refinery, not so for other compound classes (aldehydes, halogenated hydrocarbons, etc.)

Findings on PM… • Wind regression shows consistency between high

La/Ce ratio periodically observed at Roxana and bearings of refinery unit operations. No exceptional emission events were observed.

• PM2.5 shows no significant local source contributions and agrees with the urban and larger-scale contributions.

• SO2 hourly average concentrations well below the NAAQS standards

Summary II

Non parametric wind regression analysis (NWR) • can identify the bearings of potential

emission sources • calculate the expected concentration at

a receptor site based on wind direction data

• use a Gaussian kernel to create a weighted average of concentration for each wind direction window

• Confidence intervals can be used to identify whether the concentration peaks are real for stable emission sources

Wind rose was created from the meteorological data collected at Roxana on the sampling days only

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Principal component analysis on air toxics data at Roxana suggests four possible categories: • aldehydes; • aromatics, n-octane and propylene; • halogentated hydrocarbons; and • mixture.

Time series of factor scores on four categories identified by PCA

Principal Component Analysis on Air Toxics Gases at Roxana

Principal component analysis on air toxics data at Blair suggests four possible categories : • aldehydes; • aromatics, n-octane and propylene; • halogenated hydrocarbons; and • Mixture.

Time series of factor scores on four categories identified by PCA

Principal Component Analysis on Air Toxics Gases at Blair Street

halogenated hydrocarbons

Nonparametric Wind Regression on PCA Scores

Blair Roxana

Similar patterns at Blair and Roxana suggest regional sources dominate Lack of directional features support ubiquitous presence of these

compounds Consistent during the time period of interest

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aldehydes

Nonparametric Wind Regression on PCA Scores

Blair Roxana

Pattern shows consistency between the elevated concentrations and southerly wind in the summer

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aromatics, …

Nonparametric Wind Regression on PCA Scores

Blair Roxana

Patterns consistent with refinery contributions at Roxana. No directional pattern observed at Blair Street.

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