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POLAR ORGANIC COMPOUNDS IN FINE PARTICLES FROM THE NEW YORK, NEW JERSEY, AND CONNECTICUT REGIONAL AIRSHED

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Impact/Purpose:

The three main goals of this project are: 1) to identify and measure the ambient abundances of polar organic compounds found as PM2.5 in the NY, NJ and CT regional airshed using Liquid Chromatography/Mass Spectrometry (LCMS) chemical analysis; 2) to measure and identify both known and potential secondary organic aerosol source markers found within the fine particle acidic organic fraction; and 3) to identify emissions of polar organic compounds from primary sources, including vehicular sources and wood combustion.

Description:

Five key scientific questions guiding this research were explored. They are given here with results generated from the project.
 
B.1.        How can polar organic compounds be measured in atmospheric fine particulate matter? Is there potential analytical equipment that could quantify the compounds without a derivatization technique?
The LCMS instrument we used for this study proved to be unreliable and was not designed for the analysis of low molecular-weight, negatively charged compounds such as organic acids (Mazurek 2008, NSF ATM Final Report Award #0120906, included as a supplement to this report). Also, HPLC UV-VIS analysis is not a comprehensive method for polar organic compounds extracted from atmospheric fine PM. Suitable chromophores within the analyte are necessary for quantitation with a UV/Vis detector).
 
B.1.1       HPLC Methods Development for Atmospheric Polar Organic Compounds
 
We developed two quantitative High Pressure Liquid Chromatography (HPLC) methods using UV-VIS detection and a monolithic silica column to separate and measure oxocarboxylic acids and carbonyl compounds as DNPH derivatives. Two peer-reviewed papers were generated by Hawley et al. Both were published in American Laboratory On-Line (ALOL). Significant outcomes follow.
 
The paper by Hawley and Mazurek (2008), entitled, "Oxocarboxylic Acids as DNPH Derivatives with a Monolithic Silica Column and UV-VIS Detection," reported a novel HPLC method for the analysis of oxocarboxylic acids. This is a compound class thought to represent a major group of secondary organic compounds formed in the atmosphere. We determined oxocarboxylic acids do form DNPH derivatives and can be detected by UV/VIS at the same wavelengths as carbonyl-DNPH compounds. There is no way to distinguish the UV/VIS response produced by oxocarboxylic and carbonyl-DNPH derivatives. Thereofre, current HPLC UV/VIS methods used to quantify carbonyl compounds in urban atmospheres and in emissions tests likely overestimate simple carbonyl concentrations because of the presence of oxocarboxylic acids. MS detection by either LC or GC would be needed to distinguish between the two compound classes and individual compounds within each class.
 
The paper by Hawley and Mazurek (2009), entitlted, "An Efficient Method for Atmospheric Carbonyl Compounds as 2, 4-DNPH-Carbonyl Derivatives with HPLC UV/VIS Detection," described a novel, efficient separation method for atmospheric carbonyl compounds.
 
Low molecular-weight carbonyl compounds such as C1-C7 aldehydes and ketones, are common in urban, suburban, and rural atmospheres. These compounds are measured routinely by state and federal air quality management agencies to monitor levels of ozone-forming precursors. A new ozone 8-hour primary standard was announced March 12, 2008, by the US EPA, reducing its concentration to 0.075 ppm. This requirement puts greater emphasis on routine monitoring of emissions of ozone precurosrs and on ambient levels of carbonyl compounds, especially in nonattainment regions in the U.S. Atmospheric carbonyl compounds orginate as primary emissions from anthropogenic and biogenic sources and are formed photochemically from the oxidation of hydrocarbons. Some carbonyls are toxic to living organisms and many are designated as Hazardous Air Pollutants (HAPs). The goal of this project task was to develop a fast, quantitative and inexpensive HPLC UV/VIS method for airborne aldehydes and ketones that improves existing standard methods.
 
The method development approach used a C8 monolithic silica column was to separate the California Air Resources Board (CARB) 13-component carbonyl standard as 2, 4-DNPH-derivatives. Reduced retention times were seen (3.44 to 9.29 minutes) compared to United States Environmental Protection Agency Method 8315a (12 to 34 minutes) and California Air Resources Board Standard Operating Procedure MLD 104 (11.01 to 31.85 minutes). Multiple injections (n = 10; 0.5 to 18 ng per compound) produced consistent peak areas (standard deviation = 0.62-3.07) and retention times (standard deviation = 0.08-0.36). The r-squared values for calibration curves ranged from 0.980 to 0.999. Method detection limits (MDL) were found using two methods. The lowest MDL by either method corresponded to the C1 and C2 carbonyl standards (0.1 ng/mL to 1.5 ng/mL). The highest MDL were found for the C5 to C8 carbonyl compounds (2.2 ng/mL to 6.0 ng/mL). The monolithic silica c8 column HPLC method was shown to be an improved approach for the routine analysis of volatile C1 to C8 carbonyl compounds compared to the current standard US EPA HPLC methods for this class of regulated compounds. Given the 2008 US EPA Final Rule for ground-level ozone, increased surveillance will be necessary to monitor emission sources and ambient concentrations of airborne carbonyl compounds as ozone precurors. The monolithic silica column separates carbonyl compounds 60% faster than the current standard methods using multiple packed columns. The improved separation efficiency results in less costly sample analysis and reduces levels of waste mobile phsae, which must be disposed or incinerated as hazardous waste. This study suggests the need for updating the current federal protocol for airborne carbonyl compounds as DNPH-derivatives. Modern column technology offers clear advantages for efficient separation, precise and quantitative results.
 
B.1.2       GCMS Methods Development for Atmospheric Polar Organic Compounds
 
A mass selective detector (MS) is crucial for identifying and quantifying organic compounds in complex polar extract mixtures from the fine PM samples. Polar organic compounds can be measured effectively using GCMS, but requires a preanalysis derivatization step because of the low vapor pressure (boiling point) of low molecular weight organic acids. The derivatization reagent used in this study was BSTFA because it worked for all polar organic marker compounds of interest.
 
The BSTFA combines selectively with -OH and -COOH functional groups to produce trimethylsilyl (TMS) ethers. We refined an earlier version of the BSTFA conversion step and improved conversion efficiency and stability of the TMS ethers. The updated method for PM polar compounds provided stable, quantitative measurements for a suite of 31 polar organic marker, including smoke anhydrous sugars and phenols (e.g., levoglucosan), sterols (cholesterol, b-sitosterol, campesterol), n-alkanols, aromatic carboxylic acids, and aliphatic low-molecular weight oxocarboxylic acids and dicarboxylic acids.
 
B.2.          What is the contribution of wood smoke to the atmosphere in the New York City (NYC) area?
 
We completed GCMS analysis and marker quantitation of polar organic compounds as BSTFA derivatives from 24-hr integrated filter samples using dedicated Tisch 2 or 4- channel speciation samplers. Detils of the SOAP 2002-2003 study were published in McDow et al., (2008). In this STAR grant project, fifteen seasonal composites were generated from a full annual cycle of 24-hour filter samples collect in the NY area fine; Elizabeth, NJ (urban, NJ Turnpike Toll Plaza 13), Chester, NJ (rural, upwind low density residential); Flushing Queens, NYC (urban, high density residential); and Westport, CT (downwind, low density residential). Filters were collected according to the Speciation Trends Network (STN) schedule either as one-in-three day (SOAP 2002-2003). The filter composites were extracted with acetone/methylene chloride (1:1). One half of the extract was derivatized with N, O-bis(Trimethylsilyl)trifluoro-acetamide (BSTFA) and 1% trimethy-chlorosilane (TMS) to convert -OH and COOH groups to trimethylsilyl ethers and esters, respectively. Standard solutions for 31 polar marker compounds were prepared and analyzed as 5-point calibration series for both.
 
The wood smoke molecular marker levoglucosan was quantified year round in the NYC area. In the fall and winter levoglucosan values reached a high of 189.47 ng/m3 in the late fall in Westport, CT making it one of the most abundant individual organic compounds quantified in fine PM. The estimated influence of wood smoke, based on emission factors, ranged from less than 1% OC from wood smoke to a high of 69% OC from wood smoke (fall season in Westport, CT). These results indicate seasonal fine PM concentrations could be reduced with the management of wood burning practices in the metropolitan NYC area.
 
Statistical analysis of the SOAP 2002-2003 molecular markers demonstrated seasonal variations of wood smoke at two sites (Westport, CT and Bronx, NY), meat charbroiling at only one site (Bronx, NY), and levulinic acid at three sites (Westport, CT, Bronx, NY and Pinnacle State Park, NY). When the samples were grouped as urban and rural areas for the 2002-2007 combined study period, the ANOVA results showed there was no spatial or seasonal trend in levoglucosan, total n-alkanols or levulinic acid. A significant finding was the wood smoke marker, levoglucosan, was higher for the NYC metropolitan and suburban sites than for the rural sites and was found year-round. Apparently, there are significant sources of wood smoke in the NYC metropolitan area (NY/NJ/CT 22-county PM2.5 nonattainment region) that persisted throughout the 2002-2003 sampling year.
 
Several urban sources of the levoglucosan marker include wood and biomass combustion, cardboard and paper, and charcoal barbeques for outdoor cooking. Emissions from wood-fired pizza ovens, outdoor vendor carts, and other commercial food preparation using wood-fired cooking sources are possibly a significant sources of the wood smoke in the NYC metropolitan area.  The levoglucosan, total n-alkanols, cholesterol, cis-pinonic acid and levulinic acid normalized to elemental carbon did show statistical differences between urban and rural sites, indicating the sites were influenced by local emission sources and meteorological conditions. 
Source tests on these urban examples of wood, paper, biomass, and charcoal should be conducted to determine emission profiles for the levoglucosan marker and other anhydrous sugars, and n-alkanols.
 
B.3.      Is meat charbroiling a significant cause of fine aerosols in the NYC area?
Meat charbroiling was found to have a higher influence in urban areas than in rural areas.  There was no seasonal distribution of cholesterol in the urban areas, therefore meat cooking appeared to be a constant source of fine PM to the urban sites. The estimated influence on fine aerosol OC was lower than 5%; this is the estimate of meat cooking only and does not include the influence of oils which may in turn increase the expected influence of cooking emissions on fine PM in this study area.
B.4.      What is the contribution of vegetative detritus to this highly urbanized area?
Biogenic sources were quantified in the urban and rural areas of this study using the n-alkanol and phytosterol markers.  These markers did show seasonal trends, with the highest concentrations occurring in the spring and fall.  The urban areas showed increases in the winter, which may be due to wood combustion for heating purposes.  There are no emission factors so an estimated influence on fine PM was not attainable.
B.5.      What secondary organic aerosol markers, found in smog chamber experiments, can be seen in urban and regional background sites in the northeastern United States?  What is the estimated primary versus secondary contribution based on molecular markers?
cis-Pinonic acid was found in the samples from the NYC area indicating biogenic oxidation products were present in the northeastern U.S. airshed.  The oxoacids were difficult to interpret.  Levulinic acid was found in many samples however it was unclear whether this compound is formed only in the atmosphere or if its presence is a combination of primary emissions and oxidation byproducts.  Levulinic acid is a low molecular-weight oxocarboxylic acid that is ubiquitous in biochemical metabolic pathways.  Thus, it is possible there are yet undetermined sources of this marker in the urban locations.  The remaining oxoacids were not quantifiable in the samples because it was not established the extent to which the oxoacids were soluble in the extraction solvents (acetone/ methylene chloride, 1:1) used for this research.  It is difficult to estimate primary and secondary emissions based only on the carboxylic acids studied in this project.  The concentration of cis-pinonic acid, a known secondary oxidation product, and levulinic acid, a suspected secondary oxidation product, were both lower than levoglucosan levels. 
 
D.    Statements addressing how the quality assurance requirements are being met, especially focusing on the assurance of data quality relevant to environmental measurements and data generation. 
The broader goal of this project was to bring new analytical instrumentation online to: 1) help identify the complex mixture of organic compounds associated with PM, and 2) permit easier detection and measurement of polar organic markers needed for source apportionment models (i.e., CMB 8.2).  We abandoned the LCMS analysis method because the instrument was not designed to measure quantitatively low molecular-weight organic acids.  It also broke down excessively.  We were UNABLE to obtain stable 5-point calibration curves over 4 years of constant evaluation using the LCMS APPI detector (includes additional 3-yr support from an NSF Atmospheric Chemistry Program, Award #0120906).  However, we produced two quantitative HPLC UV/VIS methods with good precision for the analysis of oxocarboxylic acids and carbonyl compounds.  Two methods papers were published. 
We adapted a GCMS method with BSTFA derivatization to quantify a broader group of polar organic markers.  Five-point calibrations were run throughout the study for the 31 target markers using the GCMS plus BSTFA method.  Consistent and reproducible results were obtained with low limits of detection.  The updated BSTFA method is described in papers in progress from this EPA STAR project.
E.      Results to date, emphasizing findings and their significance to the field, their relationship to the general goals of the award, their relevance to the Agency's mission, and their potential practical applications.  
The research tasks performed January 1, 2005 through December 31, 2009, produced new methods for detecting and measuring polar organic compounds associated with atmospheric fine particles.  Urban and rural differences were found comparing the abundances of 31 organic markers.  The Agency mission relevance of the project results are presented below.
This EPA STAR research project identified wood smoke as a major source of PM2.5 OC ambient mass concentrations in the regional NYC area using molecular marker analysis, emission mass ratios from source testing, and calculations of the predicted PM2.5, EC, and OC masses.  Our results confirm US EPA source emission estimates that wood smoke is a major source of PM2.5 concentrations in the NYC regional PM2.5 nonattainment counties.  At this time, wood smoke emissions from urban home heating activities and commercial food preparation activities and restaurants are unregulated sources.  This STAR project provides field evidence for wood smoke PM2.5 as a major contributor to fine particles in the NYC regional airshed.
 
E.1                 Seasonal and Spatial Concentrations of Wood-Smoke
The SOAP field study demonstrated year-round concentrations of levoglucosan.  The urban sites had the highest levoglucosan concentrations.  This finding suggests in addition to rural burning of wood, there were significant sources of wood smoke emissions in the SOAP urban study areas.  A search of Google for coal (571) and wood-fired (876) pizza oven restaurants near NYC resulted in over 1447 restaurants:

In addition to the coal and wood-fired pizza ovens, other restaurants may use wood fuels in food preparation as well as street vendors.  The number of the combined restaurant sources is not known for the study area.  As evaluation of the NY, NJ and CT state emissions inventories and SIPs would provide a better estimate for the source strength of the commercial cooking emissions of levoglucosan.  Outdoor wood-fired boilers also might have contribute to the rural loadings of levoglucosan throughout the year.  Residential home-heating using wood fuel may account for the higher concentrations of levoglucosan in the cooler seasons.  The highest levoglucosan concentration was found in Westport, CT in early fall 2002 and suggested high local emissions from residential heating. 

The NYC upwind Chester, NJ site and the downwind Westport, CT site were heavily influenced by PM2.5 emitted from wood and biomass combustion in the cool months.  Therefore, increased focus on residential wood smoke emission sources (fireplaces, stoves, outdoor wood boilers) and appropriate emissions reduction technologies would likely result in substantial improvements in fine particle concentrations for low ambient temperature periods.
 
E.2                 Meat Cooking Emissions Source Strength
In the 2002-2003 field sampling campaign, the percent of OC from cholesterol generally was higher at the urban sites compared to the background and upwind sites.  Chester, NJ had OC contributions from meat charbroiling near 0% OC because cholesterol was not detected in fine PM samples from the site.  Westport, CT showed an increase in the spring when 0.5% of the OC was estimated to be from meat charbroiling.  Elizabeth, NJ had seasonal variations in the percent of OC mass due to meat cooking.  The highest percent was in the fall with over 3%.  Queens, NY, the urban site, typically had the highest percent OC from meat cooking operations.  This was due to the highest density number of restaurants at this site. 
Fine PM emitted from commercial cooking sources currently is not regulated.  Better quantitative information on the regional source strength from emissions tests and improved emission inventory analysis should be considered as a management strategy for the NYC metropolitan nonattainment counties.  Local emissions from cooking activities dominated the SOAP urban receptor sites and were seen at a fairly constant level over the annual study period.  The SOAP rural upwind site (Chester, NJ) had below detection levels of cholesterol.
Based on the SOAP 2002-2003 study, cholesterol can be considered a reliable molecular marker for urban air masses.  This simplifies studies of air mass trajectories and long-range transport from megacity regions such as NYC.
 
E.3            Secondary Organic Compounds
We were unable to make significant progress on the conundrum of secondary organic compounds.  One outlying question concerned the oxoacid target compounds (“secondary” OC).  These compounds might not have been fully soluble in acetone:dichloromethane (1:1) extraction solvent.  Therefore, continued work on the oxoacids and similar multifunctional low molecular-weight compounds is a near-term focus for the ambient PM2.5 samples in the NYC area.  We have received funding from the NY State Energy Research and Development Authority (NYSERDA) to extract the remaining portions of the ambient filters in a more polar solvent, such as methanol, and quantify the low molecular weight, highly oxidized acids.  Our tests of the solubility of oxalic acid, a low molecular weight highly oxidized acid, also indicated this highly polar compound was not soluble in the 50/50 dicholoromethane/acetone solvent mixture used to extract the filters for GCMS analysis.  Therefore, a portion of the secondary organic compounds could have remained on the filters during this extraction step. 
A mass balance of the highly polar organic compounds (i.e., soluble in methanol or water) is needed to quantify the oxoacids and low molecular-weight dicarboxylic acids (e.g., oxalic acid).  This step will be useful in determining the levels of primary versus secondary emissions in the NYC metropolitan area.  GCMS analysis of oxoacids with derivatization techniques other than BSTFA can be studied further to quantify oxoacids in the NYC area. 
Further testing is necessary for biogenic sources to determine compounds, for example levulinic acid.  Levulinic acid was discovered year round in quantifiable levels.  Determining whether levulinic acid can be directly emitted into the atmosphere, as opposed to produced in the atmosphere, is an important distinction if the influence of SOAs on air quality is to be determined.  Source emission tests on domestic and industrial solid waste combustion could identify and confirm tracers from this category.  Large wastewater and solid waste facilities in the NYC area could be adversely impacting air quality and releasing low molecular weight organic acids into the atmosphere.  Determining molecular markers for this waste processing facilities, then reevaluating these samples for those markers would provide additional information that could be used to improved air quality management strategies in the NYC metropolitan regional airshed.  
 
E.4             Organic molecular marker ambient concentrations
The databases generated from the SOAP 2002-2003 field study will be published as Excel files on the Rutgers RuCORE web site supported by the Rutgers Libraries [http://rucore.libraries.rutgers.edu/].  These will be permanent archives and available through open public access. 

Record Details:

Record Type:PROJECT( ABSTRACT )
Start Date:01/01/2005
Completion Date:12/31/2007
Record ID: 175927