Monica A. Mazurek

ORGANIC TRACERS FROM WILD FIRE RESIDUES IN SOILS AND RAIN/RIVER WASH-OUT

The molecular compositions and alteration products of the major organic components in soils and litter subjected to controlled or wildfire burning, and subsequent erosion by rain and river transport have been determined by GC-MS. The major compound groups imparted to soils include n-alkanoic acids, n-alkanes, n-alkanols, phytosterols, and terpenoids. Biomarker tracer analysis indicates that organic compounds remain as internal lipid components of char and heavy particles and are deposited onto soil during wildfire and prescribed burning. The process of rain erosion and river transport releases some of these internal components into the surroundings where they are further subjected to biological alteration. The distributions and abundances ofhomologous compound series coupled with biomarker tracer analysis provides a chemical fingerprint which is useful for identifying the single or multiple plant species contributing organic matter by both thermal (burning) and biological processes. Such fingerprints are useful for tracking soils which are transported in the atmosphere by wind as suspended particles in dust storms and on land by rain erosion to rivers.

Speciation and Atmospheric Abundance of Organic Compounds in PM2.5 from the New York City Area. I. Sampling Network, Sampler Evaluation, Molecular Level Blank Evaluation

This study demonstrates an approach for evaluating a molecular level sampling and analysis protocol for organic marker compounds at the high picogram m−3 (ppt) to low nanogram m−3 (ppb) mass concentrations in urban and background receptor sites. The Speciation of Organics for Apportionment of PM2.5 in the New York City Area (SOAP) project was conducted from May 2002 to May 2003 at four sites in New York City, New Jersey, and Connecticut. Its chief objectives were to expand the chemical characterization of organic compounds and to estimate the source contributions of carbonaceous fine particles at urban and background monitoring sites. Two major challenges were faced in order to successfully implement the SOAP sampling network. First, collection of adequate fine PM mass was necessary for successful quantitation of organic marker compounds. Second, sufficiently low blank levels were required for each marker compound for accurate identification and quantitation needed for source-receptor modeling. Initial field tests of representative samplers designed for sampling PM chemical species indicated insufficient sample mass collection, unless analytical sensitivity for organic markers could be greatly improved. Adequate PM mass was collected using a Tisch TE-1202 sampler that operated at a much higher flow rate (113 lpm). Preliminary field tests also revealed unacceptably high travel blank levels for n-alkanes and carboxylic acids. The mass of organic marker compounds observed on travel blank filters was reduced significantly by shipping filters in sealed filter holders. Further evaluation of the Tisch TE-1202 sampler also demonstrated the sampler was free of organic components and impactor grease upstream of the filter. These features also reduced the contribution of carbonaceous species to system blanks and therefore, to the total mass collected. As a result, blank levels for hopanes, PAHs, and dicarboxylic acids were below limits of detection (LOD), and n -alkanes (C25 to C32), n-alkanoic acids (C12, C14, C16, and C18), and phthalic acid exhibited acceptable low levels in all SOAP blanks ranging from 1 to 10 times the limit of detection for each compound class. Overall, adequate sample mass and sufficiently low blank levels were achieved successfully with the SOAP fine particle collection protocol.

Sequential derivatization of polar organic compounds in cloud water using O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride, N,O-bis(trimethylsilyl)trifluoroacetamide, and gas-chromatography/mass spectrometry analysis

Cloud water samples from Whiteface Mountain, NY were used to develop a combined sampling and gas chromatography-mass spectrometric (GCMS) protocol for evaluating the complex mixture of highly polar organic compounds (HPOC) present in this atmospheric medium. Specific HPOC of interest were mono- and di keto-acids which are thought to originate from photochemical reactions of volatile unsaturated hydrocarbons from biogenic and manmade emissions and be a major fraction of atmospheric carbon. To measure HPOC mixtures and the individual keto-acids in cloud water, samples first must be derivatized for clean elution and measurement, and second, have low overall background of the target species as validated by GCMS analysis of field and laboratory blanks. Here, we discuss a dual derivatization method with PFBHA and BSTFA which targets only organic compounds that contain functional groups reacting with both reagents. The method also reduced potential contamination by minimizing the amount of sample processing from the field through the GCMS analysis steps. Once derivatized only gas chromatographic separation and selected ion monitoring (SIM) are needed to identify and quantify the polar organic compounds of interest. Concentrations of the detected total keto-acids in individual cloud water samples ranged from 27.8 to 329.3ngmL(-1) (ppb). Method detection limits for the individual HPOC ranged from 0.17 to 4.99ngmL(-1) and the quantification limits for the compounds ranged from 0.57 to 16.64ngmL(-1). The keto-acids were compared to the total organic carbon (TOC) results for the cloud water samples with concentrations of 0.607-3.350mgL(-1) (ppm). GCMS analysis of all samples and blanks indicated good control of the entire collection and analysis steps. Selected ion monitoring by GCMS of target keto-acids was essential for screening the complex organic carbon mixtures present at low ppb levels in cloud water. It was critical for ensuring high levels of quality assurance and quality control and for the correct identification and quantification of key marker compounds.