Particle-into-liquid Sampler Research Articles

Factors contributing to elevated concentrations of PM2.5 during wintertime near Boise, Idaho

Wintertime chemical composition of water–soluble particulate matter with aerodynamic diameter less than 2.5μm (PM2.5) was monitored in the Treasure Valley region near Boise, Idaho. Aerosol was sampled using a Particle Into Liquid Sampler (PILS) and subsequently analyzed using ion exchange chromatography and a total organic carbon analyzer. During the two–month sampling campaign, the region experienced varying meteorological regimes, with an extended atmospheric stagnation event towards the end of the study. For all of the weather regimes, water–soluble PM2.5 was dominated by organic material, but particulate nitrate showed the greatest variation over time. These variations in particulate nitrate concentration were found to be dependent on the time of day, nitrogen oxides (NOX) concentrations, and relative humidity. The increases in particulate nitrate did not correlate with an equivalent molar increase of ammonium concentration, ruling out solid ammonium nitrate formation as the dominant source. Instead, our analysis using an online aerosol thermodynamic model suggests that the condensation of gas phase nitric acid was possible within the meteorological conditions experienced during the study. In running this model, atmospheric chemical and physical parameters close to those observed during the study were used as model input. The simulation was run for three different scenarios, representing the different meteorological regimes experienced during the study. From the simulation particulate nitrate concentration was highest during cold and humid nights. Currently this region is in attainment with the National Ambient Air Quality Standards (NAAQS) for PM2.5; however, with the projected increase in population and economic growth, and the subsequent increase in NOX emissions, these episodic increases in particulate nitrate have the potential of pushing the area to non–attainment status.

Real-Time Study of Particle-Phase Products from α-Pinene Ozonolysis and Isoprene Photooxidation Using Particle into Liquid Sampling Directly Coupled to a Time-of-Flight Mass Spectrometer (PILS-ToF)

A particle into liquid sampler (PILS) has been directly coupled to an accurate mass atmospheric ionization time-of-flight mass spectrometer (ToF) for use in the speciation of secondary organic aerosol (SOA) formed in the University of California—Riverside, College of Engineering–Center for Environmental Research and Technology (CE-CERT) atmospheric chambers. To this end, the PILS has been optimized for direct continuous injection into the ToF and the PILS-ToF system has been used to obtain real-time mass spectral traces of the particle phase products of atmospheric chamber reactions. The PILS-ToF system has been initially applied to SOA formed from α-pinene dark ozonolysis and isoprene photooxidation. The characterization of the PILS-ToF system includes experiments on the well understood α-pinene/O3 system, which verifies the performance of the tool. The PILS-ToF tool is then used to provide new insight into the chemical composition of the SOA formed from isoprene photooxidation. For the first time, time ...

Online determination of levoglucosan in ambient aerosols with particle-into-liquid sampler – high-performance anion-exchange chromatography – mass spectrometry (PILS–HPAEC–MS)

Abstract. Biomass burning, such as domestic heating, agricultural, and wild open-land fires, has a significant influence on the atmosphere at the global and, especially, at the local scale. Levoglucosan has been shown to be a good tracer for biomass burning emissions in atmospheric particulate matter, and several analytical techniques have been presented for the determination of levoglucosan from filter samples. In this paper, a novel combination of a particle-into-liquid sampler (PILS) to a high-performance anion-exchange chromatograph (HPAEC) with the detection by a mass spectrometer (MS) is presented for the online analysis of levoglucosan in ambient particles. The PILS–HPAEC–MS technique enables a fast online analysis of levoglucosan from the particulate samples. The method was tested at an urban background station in Helsinki, Finland, in winter 2011. A comparison with simultaneous levoglucosan measurements from filter samples by the HPAEC–MS was performed and it showed a good agreement between the online and offline methods. Additionally, the online levoglucosan data were compared with the biomass burning tracer fragments measured by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). As there were no local biomass burning sources close to the measurement station, online levoglucosan measurements revealed that most of the particles from biomass burning were either regionally distributed or long-range transported in the urban background of Helsinki. The average levoglucosan concentrations were relatively low (average 0.083 μg m−3) during the measurement campaign. The highest concentration peak measured for levoglucosan (1.4 μg m−3) seemed to originate from biomass burning in the Baltic countries, likely in Estonia, that was transported to Helsinki.

Characteristics, sources and water-solubility of ambient submicron organic aerosol in springtime in Helsinki, Finland

In this study the characteristics, sources and water-solubility of submicron organic aerosol (OA) were investigated in Helsinki, Finland. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was used to determine the submicron non-refractory aerosol components nitrate, sulfate, ammonium, chloride and organics between April 9 and May 8, 2009. The concentrations of the major water-soluble ions and water-soluble organic carbon (WSOC) were measured by a particle-into-liquid sampler (PILS) combined with a total organic carbon (TOC) analyzer and two ion chromatographs (IC) between April 25 and May 28, 2009. Parallel measurements of the submicron particulate matter (PM1), organic carbon (OC), black carbon (BC), meteorological quantities and trace gases were used to complement and validate the AMS and PILS-TOC-IC data.Sources or atmospheric processes affecting the organic aerosol were investigated by applying the Positive Matrix Factorization (PMF) analysis to the high-resolution mass spectra of the HR-ToF-AMS organics. All together seven factors were needed to describe the variation in the obtained dataset. The factors consisted of two different types of low-volatility oxygenated OA (LV-OOA), local and long-range-transported (LRT) biomass burning OA (BBOA), semi-volatile OA (SV-OOA), hydrocarbon-like OA (HOA), and one local source (coffee roastery). These factors were interpretable and could be connected to specific sources or chemical characteristics (biomass burning, traffic, biogenic emissions, oxidized long-range-transported aerosols, marine-processed aerosols and nearby industrial activity) of ambient aerosols. In order to study the organic fraction and PMF factors further, the elemental ratios OM:OC, O:C, H:C and N:C were calculated. The value of the OM:OC ratio varied between 1.4 and 2.1. A high OM:OC ratio (1.5–2.1) was observed for the highly-oxidized and water-soluble fraction, whereas this ratio was clearly lower (1.2–1.4) for local and fresh sources such as traffic. Two different factors representing local and long-range-transported biomass burning were observed. Local biomass burning emissions had a lower OM:OC ratio, indicating that this factor was less aged and had a different source area compared with the LRT BBOA. The water-solubilities of the OA factors were studied by investigating the correlation between these factors and WSOC and by reconstructing the concentration of water-soluble particulate organic matter (WSPOM) from the OA factors. The reconstructed WSPOM had a good correlation with the measured concentration of WSPOM.

Microfluidic electrochemical sensor for on-line monitoring of aerosol oxidative activity.

Particulate matter (PM) air pollution has a significant impact on human morbidity and mortality; however, the mechanisms of PM-induced toxicity are poorly defined. A leading hypothesis states that airborne PM induces harm by generating reactive oxygen species in and around human tissues, leading to oxidative stress. We report here a system employing a microfluidic electrochemical sensor coupled directly to a particle-into-liquid sampler (PILS) system to measure aerosol oxidative activity in an on-line format. The oxidative activity measurement is based on the dithiothreitol (DTT) assay, where, after being oxidized by PM, the remaining reduced DTT is analyzed by the microfluidic sensor. The sensor consists of an array of working, reference, and auxiliary electrodes fabricated in a poly(dimethylsiloxane)-based microfluidic device. Cobalt(II) phthalocyanine-modified carbon paste was used as the working electrode material, allowing selective detection of reduced DTT. The electrochemical sensor was validated off-line against the traditional DTT assay using filter samples taken from urban environments and biomass burning events. After off-line characterization, the sensor was coupled to a PILS to enable on-line sampling/analysis of aerosol oxidative activity. Urban dust and industrial incinerator ash samples were aerosolized in an aerosol chamber and analyzed for their oxidative activity. The on-line sensor reported DTT consumption rates (oxidative activity) in good correlation with aerosol concentration (R(2) from 0.86 to 0.97) with a time resolution of approximately 3 min.

Evaluation of Composition-Dependent Collection Efficiencies for the Aerodyne Aerosol Mass Spectrometer using Field Data

In recent years, Aerodyne aerosol mass spectrometers (AMS) have been used in many locations around the world to study the size-resolved, nonrefractory chemical composition of ambient particles. In order to obtain quantitative data, the mass or (number) of particles detected by the AMS relative to the mass (or number) of particles sampled by the AMS, i.e., the AMS collection efficiency (CE) must be known. Previous studies have proposed and used parameterizations of the AMS CE based on the aerosol composition and sampling line relative humidity. Here, we evaluate these parameterizations by comparing AMS mass concentrations with independent measurements of fine particle volume or particle-into-liquid sampler (PILS) ion chromatography measurements for 3 field campaigns with different dominant aerosol mixtures: (1) acidic sulfate particles, (2) aerosol containing a high mass fraction of ammonium nitrate, and (3) aerosol composed of primarily biomass burning emissions. The use of the default CE of 0.5 for all c...

Enhanced sulfate formation on ozone-exposed soot

Gas phase experiments were conducted to examine the heterogeneous oxidation of sulfur dioxide on methane soot in the presence of ozone and water vapor. The enhanced formation of sulfate at atmospheric pressure was confirmed by the use of a particle-into-liquid sampler (PILS) coupled with ion chromatography (IC). Due to the ozone oxidation, multilayer adsorption of sulfur dioxide on soot, as well as sulfate formation and physisorption on secondary surface layer sites was observed. The ozone exposure also caused the soot to become hydrophilic, due to the formation of sulfuric acid and also likely the formation of carboxyl groups on the surface. For the soot and sulfur dioxide concentrations used, the sulfate yield increased with ozone levels, but no increase was observed at ozone concentrations above 2600 ppm.

Case Study of Water-Soluble Metal Containing Organic Constituents of Biomass Burning Aerosol

Natural and prescribed biomass fires are a major source of aerosols that may persist in the atmosphere for several weeks. Biomass burning aerosols (BBA) can be associated with long-range transport of water-soluble N-, S-, P-, and metal-containing species. In this study, BBA samples were collected using a particle-into-liquid sampler (PILS) from laboratory burns of vegetation collected on military bases in the southeastern and southwestern United States. The samples were then analyzed using high resolution electrospray ionization mass spectrometry (ESI/HR-MS) that enabled accurate mass measurements for hundreds of species with m/z values between 70 and 1000 and assignment of elemental formulas. Mg, Al, Ca, Cr, Mn, Fe, Ni, Cu, Zn, and Ba-containing organometallic species were identified. The results suggest that the biomass may have accumulated metal-containing species that were re-emitted during biomass burning. Further research into the sources, dispersion, and persistence of metal-containing aerosols, as well as their environmental effects, is needed.

Photolytic processing of secondary organic aerosols dissolved in cloud droplets

The effect of UV irradiation on the molecular composition of aqueous extracts of secondary organic aerosol (SOA) was investigated. SOA was prepared by the dark reaction of ozone and d-limonene at 0.05-1 ppm precursor concentrations and collected with a particle-into-liquid sampler (PILS). The PILS extracts were photolyzed by 300-400 nm radiation for up to 24 h. Water-soluble SOA constituents were analyzed using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) at different stages of photolysis for all SOA precursor concentrations. Exposure to UV radiation increased the average O/C ratio and decreased the average double bond equivalent (DBE) of the dissolved SOA compounds. Oligomeric compounds were significantly decreased by photolysis relative to the monomeric compounds. Direct pH measurements showed that acidic compounds increased in abundance upon photolysis. Methanol reactivity analysis revealed significant photodissociation of molecules containing carbonyl groups and the formation of carboxylic acids. Aldehydes, such as limononaldehyde, were almost completely removed. The removal of carbonyls was further confirmed by the UV/Vis absorption spectroscopy of the SOA extracts where the absorbance in the carbonyl n→π* band decreased significantly upon photolysis. The effective quantum yield (the number of carbonyls destroyed per photon absorbed) was estimated as ∼0.03. The total concentration of peroxides did not change significantly during photolysis as quantified with an iodometric test. Although organic peroxides were photolyzed, the likely end products of photolysis were smaller peroxides, including hydrogen peroxide, resulting in a no net change in the peroxide content. Photolysis of dry limonene SOA deposited on substrates was investigated in a separate set of experiments. The observed effects on the average O/C and DBE were similar to the aqueous photolysis, but the extent of chemical change was smaller in dry SOA. Our results suggest that biogenic SOA dissolved in cloud and fog droplets will undergo significant photolytic processing on a time scale of hours to days. This type of photolytic processing may account for the discrepancy between the higher values of O/C measured in the field experiments relative to the laboratory measurements on SOA in smog chambers. In addition, the direct photolysis of oligomeric compounds may be responsible for the scarcity of their observation in the field.

Laboratory and Field Testing of an Automated Atmospheric Particle-Bound Reactive Oxygen Species Sampling-Analysis System

In this study, various laboratory and field tests were performed to develop an effective automated particle-bound ROS sampling-analysis system. The system uses 2′ 7′-dichlorofluorescin (DCFH) fluorescence method as a nonspecific, general indicator of the particle-bound ROS. A sharp-cut cyclone and a particle-into-liquid sampler (PILS) were used to collect PM2.5 atmospheric particles into slurry produced by a DCFH-HRP solution. The laboratory results show that the DCFH and H2O2 standard solutions could be kept at room temperature for at least three and eight days, respectively. The field test in Rochester, NY, shows that the average ROS concentration was 8.3 ± 2.2 nmol of equivalent H2O2 m−3 of air. The ROS concentrations were observed to be greater after foggy conditions. This study demonstrates the first practical automated sampling-analysis system to measure this ambient particle component.

Identification of chemistry-dependent artifacts on gravimetric PM fine readings at the T1 site during the MILAGRO field campaign

As part of the MIRAGE (MILAGRO) study conducted 7–30 March 2006 in Mexico City and its Metropolitan Area (MCMA), fine particulate matter (PM2.5) was collected using two Tapered Element Oscillating Microbalance (TEOM) systems, and a Partisol instrument at the T1 super-site (Tecamac, State of Mexico). Inorganic analysis was performed on filter-based (PM1, PM2.5-URG) measurements also collected at this site. Measurements from the gravimetric (TEOMs, Partisol) and URG systems were inter-compared with chemical speciation measurements using a Particle Into Liquid Sampler (PILS) and Thermal Optical methods. Mass and chemical balances applied over the first part of the study (11–22 March) showed that a TEOM using a device (SES) which reduces particle-bound water and retains a fraction of semi-volatile compounds (SVM) gives readings ∼30% larger than a conventional TEOM. In the second part of the study (26–30 March), the loss of SVM during TEOM-heated filter collection (both systems) represented a significant fraction of PM2.5 mass due to changes in particle composition. Overall, when nonvolatile nitrate dominated (i.e., when associated with crustal species and not NH4+) and/or sulfate dominates (SO42−/NO3− molar ratio is >1), PM2.5 mass readings are in agreement with those reported for the T1 site if TEOM is using a SES device. However, when volatile nitrate dominates (i.e., NH4NO3) or SO42−/NO3− molar ratio is <1, a larger fraction is lost from both TEOMs (with or without the SES device). Under the latter regime, uncertainties are large and gravimetric losses may reach 30%–50%. The gravimetric PARTISOL instrument recorded lower readings under all of the aforementioned conditions with differences versus TEOMs decreasing with increasing RH. These findings call for a careful characterization of such volatilization biases to improve current PM (PM10, PM2.5) measurements/networks, especially in alkaline-rich environments that can favor such biases. With regards to PM1 and PM2.5 filter-based measurements, findings are: 1) crustal-related elements are important features in the PM2.5–1 size fraction; 2) a factor of ∼2 overestimation of SO42− concentrations is recorded on substrates during PM collection and 3) main elements of a typical urban aerosol size distribution are concentrated in the 1 μm (versus 2.5 μm) size fraction.

High-Resolution Electrospray Ionization Mass Spectrometry Analysis of Water-Soluble Organic Aerosols Collected with a Particle into Liquid Sampler

This work demonstrates the utility of a particle-into-liquid sampler (PILS), a technique traditionally used for identification of inorganic ions present in ambient or laboratory aerosols, for the analysis of water-soluble organic aerosol (OA) using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). Secondary organic aerosol (SOA) was produced from 0.5 ppm mixing ratios of limonene and ozone in a 5 m(3) Teflon chamber. SOA was collected simultaneously using a traditional filter sampler and a PILS. The filter samples were later extracted with either water or acetonitrile, while the aqueous PILS samples were analyzed directly. In terms of peak abundances, types of detectable compounds, average O/C ratios, and organic mass to organic carbon ratios, the resulting high-resolution mass spectra were essentially identical for the PILS and filter based samples. SOA compounds extracted from both filter/acetonitrile extraction and PILS/water extraction accounted for >95% of the total ion current in the ESI mass spectra. This similarity was attributed to high solubility of limonene SOA in water. In contrast, significant differences in detected ions and peak abundances were observed for pine needle biomass burning organic aerosol (BBOA) collected with PILS and filter sampling. The water-soluble fraction of BBOA is considerably smaller than for SOA, and a number of unique peaks were detectable only by the filter/acetonitrile method. The combination of PILS collection with HR-ESI-MS analysis offers a new approach for molecular analysis of the water-soluble organic fraction in biogenic SOA, aged photochemical smog, and BBOA.

High time-resolution chemical characterization of the water-soluble fraction of ambient aerosols with PILS-TOC-IC and AMS

Abstract. A particle-into-liquid sampler (PILS) was coupled with a total organic carbon analyzer (TOC) and two ion chromatographs (IC) to enable high time-resolution measurements of water-soluble ions and water-soluble organic carbon (WSOC) by a single sampling and analytical set-up. The new high time-resolution measurement system, the PILS-TOC-IC, was able to provide essential chemical and physical information about fast changes in composition, concentrations and likely sources of the water-soluble fraction of atmospheric aerosol. The concentrations of major water-soluble ions and WSOC were measured by the PILS-TOC-IC system from 25 April to 28 May 2009. The data of the PILS-TOC-IC setup was compared with the data from the High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) data measured from 25 April to 8 May 2009. The measured water-soluble particulate organic matter (WSPOM) concentration varied typically from 0.10 to 8.8 μg m−3 (on average 1.5 μg m−3). The WSPOM contributed on average 51% to particulate organic matter (POM) measured with the AMS. The correlation between the data of all the online measurement devices (AMS, PILS-TOC-IC, semicontinuous EC/OC carbon analyzer and TEOM) was excellent. For sulfate, nitrate and ammonium the correlations between the PILS-TOC-IC and AMS were 0.93, 0.96 and 0.96, respectively. The correlation between WSPOM and POM was also strong (r = 0.88). The identified sources of WSPOM were long-range transported biomass burning and secondary organic aerosol (SOA) formation. WSPOM and oxalate produced in biomass burning were clearly correlated with carbon monoxide.

Characterization of soluble iron in urban aerosols using near‐real time data

We present the first near‐real time (12 min) measurements of fine particle (PM2.5) water soluble ferrous iron (WS_Fe(II)) measured in two urban settings: Dearborn Michigan, and Atlanta, Georgia. A new approach was used to measure WS_Fe(II) involving a Particle‐into‐Liquid Sampler (PILS) coupled to a liquid waveguide capillary cell (LWCC) and UV/VIS spectrometer. We found no clear diurnal trends in WS_Fe(II) at any urban site studied. High temporal variability, however, was observed at all urban sites, where concentrations often changed from the method limit of detection (4.6 ng m−3) to approximately 300 to 400 ng m−3, lasting only a few hours. These transient events predominately occurred during times of low wind speeds and appeared to be from local sources or processes. In Atlanta, several WS_Fe(II) events were associated with sulfate plumes, and highest WS_Fe(II) concentrations were found in plumes of highest apparent aerosol acidity. At all locations studied, WS_Fe(II) was poorly correlated (R2 &lt; 0.34) with light‐absorbing aerosol, indicating no direct linkage between mobile source emissions and enhanced WS_Fe(II) concentrations. WS_Fe(II) measured within a prescribed forest‐burn was strongly correlated with water soluble potassium (R2 = 0.88; WS_Fe(II)/WS_K = 15 mg/g), pointing to biomass burning as a source of WS_Fe(II); however, peak concentrations within the fire were low compared to transient events observed at the urban sites. Overall, WS_Fe(II) temporal trends for these urban sites consisted of low background concentrations with periodic short duration transient events that appear to be linked to unique industrial emissions or atmospheric processing of industrial emissions that form WS_Fe(II).

Chemical characterization of water‐soluble organic carbon aerosols at a rural site in the Pearl River Delta, China, in the summer of 2006

Online measurements of water‐soluble organic carbon (WSOC) aerosols were made using a particle‐into‐liquid sampler (PILS) combined with a total organic carbon (TOC) analyzer at a rural site in the Pearl River Delta region, China, in July 2006. A macroporous nonionic (DAX‐8) resin was used to quantify hydrophilic and hydrophobic WSOC, which are defined as the fractions of WSOC that penetrated through and retained on the DAX‐8 column, respectively. Laboratory calibrations showed that hydrophilic WSOC (WSOCHPI) included low‐molecular aliphatic dicarboxylic acids and carbonyls, saccharides, and amines, while hydrophobic WSOC (WSOCHPO) included longer‐chain aliphatic dicarboxylic acids and carbonyls, aromatic acids, phenols, organic nitrates, cyclic acids, and fulvic acids. On average, total WSOC (TWSOC) accounted for 60% of OC, and WSOCHPO accounted for 60% of TWSOC. Both WSOCHPI and WSOCHPO increased with photochemical aging determined from the NOx/NOy ratio. In particular, the average WSOCHPO mass was found to increase by a factor of five within a timescale of ∼10 hours, which was substantially larger than that of WSOCHPI (by a factor of 2–3). The total increase in OC mass with photochemical aging was associated with the large increase in WSOCHPO mass. These results, combined with the laboratory calibrations, suggest that significant amounts of hydrophobic organic compounds (likely containing large carbon numbers) were produced by photochemical processing. By contrast, water‐insoluble OC (WIOC) mass did not exhibit significant changes with photochemical aging, suggesting that chemical transformation of WIOC to WSOC was not a dominant process for the production of WSOC during the study period.

미국 St. Louis Supersite에서의 준 실시간 PM2.5에 대한 기여도 추정 및 지역 규모 오염원의 위치 파악

In this study, 1-hour integrated <TEX>$PM_{2.5}$</TEX> mass and chemical composition concentrations were monitored at the St. Louis-Midwest Supersite in Illinois. Time-resolved samples were collected one week in each of June 2001 (22 June to 28 June), November 2001 (7 November to 13 November), and March 2002 (19 March to 25 March). A total of 427 samples were collected by CAMM (continuous ambient mass monitor) and 15 compounds were analyzed by AAS, PILS (particle-into-liquid sampler), and TOT (thermal optical transmittance) method. PMF was applied to identify the sources and apportion the <TEX>$PM_{2.5}$</TEX> mass to each source for highly time resolved data. In addition, the nonparametric regression (NPR) was applied to identify the predominant directions of local sources relative to wind direction. Also, this study performed compare the NPR analysis and location of actual local point sources at the St. Louis area. The PMF modeling identified nine sources and the average mass was apportioned to gasoline vehicle, road dust, zinc smelter, copper production, secondary sulfate, diesel emission, secondary nitrate, iron+steel, and lead smelter, respectively. These results suggested that this study results will be help for <TEX>$PM_{2.5}$</TEX> source apportionment studies at similar metropolitan area, establish <TEX>$PM_{2.5}$</TEX> standard, and establish effective emissions reduction strategies in Korea.

New Technique for Online Measurement of Water-Soluble Fe(II) in Atmospheric Aerosols

A prototype instrument has been developed for online analysis of water-soluble Fe(II) (WS_Fe(II)) in atmospheric aerosols using a particle-into-liquid-sampler (PILS), which concentrates particles into a small flow of purified water, coupled with a liquid waveguide capillary cell (LWCC) and absorbance spectrophotometryto detect iron-ferrozine colored complexes. The analytical method is highly precise (<3% RSD), and the overall measurement uncertainty and limit of detection for the complete PILS-LWCC system are estimated at 12% and 4.6 ng m(-3), respectively. The online measurements compared well with those of 24 h integrated filter samples collected at two different sampling sites (n=27, R2 = 0.82, slope 0.90 +/- 0.08, and intercept 3.08 +/- 1.99 ng m(-3)). In urban Atlanta, fine particle WS_Fe(II) concentrations measured every 12 min exhibited large variability, ranging from below the detection limit (4.6) to 370 ng m(-3) during a 24 day period in June 2008. This instrument provides new capabilities for investigating the sources and atmospheric processing of fine particle WS_Fe(II) and may prove useful in studies ranging from effects of particle WS_Fe(II) on human health to effects of particle WS_Fe(II) on atmospheric chemistry and ocean biogeochemistry.

Comprehensive airborne characterization of aerosol from a major bovine source

Abstract. We report an extensive airborne characterization of aerosol downwind of a massive bovine source in the San Joaquin Valley (California) on two flights during July 2007. The Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter probed chemical composition, particle size distribution, mixing state, sub- and supersaturated water uptake behavior, light scattering properties, and the interrelationship between these parameters and meteorology. Total PM1.0 levels and concentrations of organics, nitrate, and ammonium were enhanced in the plume from the source as compared to the background aerosol. Organics dominated the plume aerosol mass (~56–64%), followed either by sulfate or nitrate, and then ammonium. Particulate amines were detected in the plume aerosol by a particle-into-liquid sampler (PILS) and via mass spectral markers in the Aerodyne C-ToF-AMS. Amines were found to be a significant atmospheric base even in the presence of ammonia; particulate amine concentrations are estimated as at least 14–23% of that of ammonium in the plume. Enhanced sub- and supersaturated water uptake and reduced refractive indices were coincident with lower organic mass fractions, higher nitrate mass fractions, and the detection of amines. The likelihood of suppressed droplet growth owing to kinetic limitations from hydrophobic organic material is explored. After removing effects associated with size distribution and mixing state, the normalized activated fraction of cloud condensation nuclei (CCN) increased as a function of the subsaturated hygroscopic growth factor, with the highest activated fractions being consistent with relatively lower organic mass fractions and higher nitrate mass fractions. Subsaturated hygroscopic growth factors for the organic fraction of the aerosol are estimated based on employing the Zdanovskii-Stokes Robinson (ZSR) mixing rule. Representative values for a parameterization treating particle water uptake in both the sub- and supersaturated regimes are reported for incorporation into atmospheric models.

Semi-continuous measurement of PM 2.5 ionic composition at several rural locations in the United States

To improve understanding of the nature and variability of the ionic fraction of atmospheric fine aerosol particles in non-urban environments, one to two month measurement campaigns were conducted at several rural locations in the United States. Study sites included Yosemite National Park (NP) (July–September 2002), Bondville, Illinois (February 2003), San Gorgonio Wilderness Area, California (April and July 2003), Grand Canyon National Park, Arizona (May 2003), Brigantine National Wildlife Refuge (NWR), New Jersey (November 2003), and Great Smoky Mountains National Park, Tennessee (July/August 2004). PM 2.5 ion composition was measured at 15 min intervals using a Particle-Into-Liquid-Sampler (PILS) coupled to two ion chromatographs. Comparisons of PILS measurements with parallel traditional 24 h denuder/filter-pack measurements reveal generally good agreement between the two techniques for major species, although PILS measurements of PM 2.5 NH 4 + are biased low by approximately 4–20%. High time resolution PILS aerosol concentration measurements provide better estimates of the range of aerosol concentrations at the rural locations than the 24 h integrated filter data. Ratios of peak 15 min to 24 h nitrate concentrations, for example, ranged from 1.7 at Brigantine NWR to 7.0 at Great Smoky Mountains NP. A strong influence of diurnal upslope/downslope transport patterns was observed on aerosol concentrations at several locations, including Yosemite NP, San Gorgonio Wilderness Area, and Great Smoky Mountains NP, with peak concentrations typically occurring during afternoon upslope transport. High time resolution aerosol composition measurements also provide new insight into relationships between individual aerosol species and the influence of environmental conditions on aerosol composition. Observations at several locations revealed important information about mechanisms of particle nitrate formation. At Yosemite and Grand Canyon National Parks, for example, evidence was observed for reaction of nitric acid or its precursors with sea salt or soil dust. Observations from several sites also revealed the importance of aerosol acidity (Great Smoky Mountains NP, Bondville) and temperature/humidity (San Gorgonio) on fine particle ammonium nitrate formation.

Interference of organic signals in highly time resolved nitrate measurements by low mass resolution aerosol mass spectrometry

Highly time resolved measurements of nitrate in ambient aerosols were conducted by an Aerodyne Quadrupole Aerosol Mass Spectrometer (Q‐AMS or simply AMS) and a particle‐into‐liquid sampler (PILS) coupled to ion chromatography from field intensives at two sites: an urban site in New York City (Queens College; QC) for wintertime (22 January to 5 February 2004) and a rural site in southwestern New York state (Pinnacle State Park; PSP) for summertime (18 July to 6 August 2004). In this study, we report that in rural atmospheres the inorganic nitrate signal from Q‐AMS may contain significant interferences from organic signals. Analysis of the QC data indicates a good agreement between the PILS‐nitrate and AMS‐nitrate measurements (R2 = 0.94; linear regression slope = 1.05). In addition, the m/z 30 and m/z 46 (two dominant ion fragments in nitrate mass spectrum) signals tightly correlate at QC (R2 = 0.98) and have an average ratio similar to that determined in the laboratory for NH4NO3 (m/z 30/m/z 46 = 2.4). In contrast, at the PSP site the correlation between PILS‐ and AMS‐nitrate was poor (R2 = 0.34), the AMS reported nitrate values were substantially higher, and the m/z 30 to m/z 46 ratios were generally much larger than 2.4. These observations, together with evaluations by aerosol phase ion balance, indicate that the AMS m/z 30 signals at PSP have been strongly influenced by organic compounds that also produce signals at m/z 30, e.g., organic nitrates (NO+), oxygenated organics (CH2O+), hydrocarbon‐like organics (C2H6+), and nitrogen‐containing organic compounds (CH4N+).