Primary Biological Aerosol Particles Research Articles

Source apportionment of the summer time carbonaceous aerosol at Nordic rural background sites

Abstract. In the present study, natural and anthropogenic sources of particulate organic carbon (OCp) and elemental carbon (EC) have been quantified based on weekly filter samples of PM10 (particles with aerodynamic diameter <10 μm) collected at four Nordic rural background sites [Birkenes (Norway), Hyytiälä (Finland), Vavihill (Sweden), Lille Valby, (Denmark)] during late summer (5 August–2 September 2009). Levels of source specific tracers, i.e. cellulose, levoglucosan, mannitol and the 14C/12C ratio of total carbon (TC), have been used as input for source apportionment of the carbonaceous aerosol, whereas Latin Hypercube Sampling (LHS) was used to statistically treat the multitude of possible combinations resulting from this approach. The carbonaceous aerosol (here: TCp; i.e. particulate TC) was totally dominated by natural sources (69–86%), with biogenic secondary organic aerosol (BSOA) being the single most important source (48–57%). Interestingly, primary biological aerosol particles (PBAP) were the second most important source (20–32%). The anthropogenic contribution was mainly attributed to fossil fuel sources (OCff and ECff) (10–24%), whereas no more than 3–7% was explained by combustion of biomass (OCbb and ECbb) in this late summer campaign i.e. emissions from residential wood burning and/or wild/agricultural fires. Fossil fuel sources totally dominated the ambient EC loading, which accounted for 4–12% of TCp, whereas <1.5% of EC was attributed to combustion of biomass. The carbonaceous aerosol source apportionment showed only minor variation between the four selected sites. However, Hyytiälä and Birkenes showed greater resemblance to each other, as did Lille Valby and Vavihill, the two latter being somewhat more influenced by anthropogenic sources. Ambient levels of organosulphates and nitrooxy-organosulphates in the Nordic rural background environment are reported for the first time in the present study. The most abundant organosulphate compounds were an organosulphate of isoprene and nitrooxy-organosulphates of α- and β-pinene and limonene.

Mass-spectrometric identification of primary biological particle markers and application to pristine submicron aerosol measurements in Amazonia

Abstract. The detection of primary biological material in submicron aerosol by means of thermal desorption/electron impact ionization aerosol mass spectrometry was investigated. Mass spectra of amino acids, carbohydrates, small peptides, and proteins, all of which are key building blocks of biological particles, were recorded in laboratory experiments. Several characteristic marker fragments were identified. The intensity of the marker signals relative to the total organic mass spectrum allows for an estimation of the content of primary biological material in ambient organic aerosol. The developed method was applied to mass spectra recorded during AMAZE-08, a field campaign conducted in the pristine rainforest of the central Amazon Basin, Brazil, during the wet season of February and March 2008. The low abundance of identified marker fragments places upper limits of 7.5% for amino acids and 5.6% for carbohydrates on the contribution of primary biological aerosol particles (PBAP) to the submicron organic aerosol mass concentration during this time period. Upper limits for the absolute submicron concentrations for both compound classes range from 0.01 to 0.1 μg m−3. Carbohydrates and proteins (composed of amino acids) make up for about two thirds of the dry mass of a biological cell. Thus, our findings suggest an upper limit for the PBAP mass fraction of about 20% to the submicron organic aerosol measured in Amazonia during AMAZE-08.

Lignin-Derived Phenols in Houston Aerosols: Implications for Natural Background Sources

Solvent-extractable monomeric methoxyphenols in aerosol samples conventionally have been used to indicate the influence of biomass combustion. In addition, the presence of lignin oxidation products (LOP), derived from the CuO oxidation of vascular plant organic matter, can help trace the source and inputs of primary biological particles in aerosols. Ambient aerosols (coarse and fine) collected in Houston during summer 2010 were analyzed by gas chromatography-mass spectrometry to characterize monomeric and polymeric sources of LOPs. This is the first time polymeric forms of the LOPs have been characterized in ambient aerosols. The absence or small concentrations of solvent-extractable monomeric LOPs and levoglucosan isomers point to the limited influence of biomass burning during the sampling period. The trace levels of anhydrosugar concentrations most likely result from long-range transport. This observation is supported by the absence of co-occurring lignin monomers that undergo photochemical degradation during transport. The larger concentration (142 ng m(-3)) of lignin polymers in coarse aerosols shows the relative importance of primary biological aerosol particles, even in the urban atmosphere. The LOP parameters suggest a predominant influence from woody tissue of angiosperms, with minor influence from soft tissues, gymnosperms, and soil organic matter.

Source apportionment of the carbonaceous aerosol in Norway – quantitative estimates based on <sup>14</sup>C, thermal-optical and organic tracer analysis

Abstract. In the present study, source apportionment of the ambient summer and winter time particulate carbonaceous matter (PCM) in aerosol particles (PM1 and PM10) has been conducted for the Norwegian urban and rural background environment. Statistical treatment of data from thermal-optical, 14C and organic tracer analysis using Latin Hypercube Sampling has allowed for quantitative estimates of seven different sources contributing to the ambient carbonaceous aerosol. These are: elemental carbon from combustion of biomass (ECbb) and fossil fuel (ECff), primary and secondary organic carbon arising from combustion of biomass (OCbb) and fossil fuel (OCff), primary biological aerosol particles (OCPBAP, which includes plant debris, OCpbc, and fungal spores, OCpbs), and secondary organic aerosol from biogenic precursors (OCBSOA). Our results show that emissions from natural sources were particularly abundant in summer, and with a more pronounced influence at the rural compared to the urban background site. 80% of total carbon (TCp, corrected for the positive artefact) in PM10 and ca. 70% of TCpin PM1 could be attributed to natural sources at the rural background site in summer. Natural sources account for about 50% of TCp in PM10 at the urban background site as well. The natural source contribution was always dominated by OCBSOA, regardless of season, site and size fraction. During winter anthropogenic sources totally dominated the carbonaceous aerosol (80–90%). Combustion of biomass contributed slightly more than fossil-fuel sources in winter, whereas emissions from fossil-fuel sources were more abundant in summer. Mass closure calculations show that PCM made significant contributions to the mass concentration of the ambient PM regardless of size fraction, season, and site. A larger fraction of PM1 (ca. 40–60%) was accounted for by carbonaceous matter compared to PM10 (ca. 40–50%), but only by a small margin. In general, there were no pronounced differences in the relative contribution of carbonaceous matter to PM with respect to season or between the two sites.

The intrinsic fluorescence spectra of selected pollen and fungal spores

Primary Biological Aerosol Particles (PBAP) are ubiquitous in the atmosphere and recently the measurement of their fluorescence properties, in real-time, have been used to discriminate biological (particularly pollen and fungal spores) from non-biological particles in ambient environments. In the laboratory study reported here, the fluorescence spectra of several types of PBAP have been measured at 370 nm excitation. By this means, instructive spectroscopic signatures have been obtained for the various botanical families and orders studied here. All the spore emission spectra were shown to closely resemble each other: they display peaks at 415 nm and broad continua between 450 and 500 nm. In comparison the pollen gave discriminating spectra. For example, the Betulaceae exhibit three distinctive and virtually identical features at 420 nm, 465 nm and 560 nm. The conifers (Pinus sylvestris, Picea abies and Taxus baccata) pollen also display these features although with differing relative intensity ratios compared to the Betulaceae. Importantly, the grasses not only show the common pollen spectral features but also a sharp band at 675–680 nm: this observation demonstrates the presence of chlorophyll-a. The latter fluorescence signal could, in principle, be used in the real-time atmospheric identification of grass pollen, which are known carriers of aeroallergens. A PCA analysis was also conducted on the obtained spectra and demonstrated that grass pollen were separable from the other samples under investigation.

Characterization of Saccharides in Size-fractionated Ambient Particulate Matter and Aerosol Sources: The Contribution of Primary Biological Aerosol Particles (PBAPs) and Soil to Ambient Particulate Matter

Size-fractionated (equivalent to ambient PM2.5 and PM10) local soil, plant, and spore samples were collected in the Sonoran Desert near Phoenix, AZ and measured for saccharide content with the goal of characterizing ambient particulate matter sources including soil and primary biological aerosol particles (PBAPs) from plants and fungi. Different saccharide compositions were observed among soil, plant, and spore samples and between PM2.5 and PM10 fractions. The total measured nonlevoglucosan saccharide content relative to PM mass in ambient aerosols collected in a Phoenix suburb (Higley) was much higher compared to the local soil samples but much lower compared to the PBAP. The enrichment of saccharides from two saccharide-dominated PM source factors resolved by a positive matrix factorization model is also higher than the saccharide content in the size-fractionated local soil samples, but lower than that measured in the size-segregated PBAP samples. This indicates that ambient concentration of particulate saccharides at Higley was dominated by contributions from PBAPs directly injected into the atmosphere from plants and spores rather than from soil and associated biota. Our results also suggest the contribution to the fine size fraction of ambient PM from the primary biologically derived sources may be greater than previously acknowledged.

Measurements and comparison of primary biological aerosol above and below a tropical forest canopy using a dual channel fluorescence spectrometer

Abstract. Aerosol particle size distributions were measured below and above a tropical rainforest canopy in Borneo, Malaysia, in June/July 2008 using the WIBS-3: a single particle dual channel fluorescence spectrometer. Material in the size range 0.8–20 μm was characterized according to optical equivalent diameter (DP), morphology and fluorescence at 310–400 nm and 400–600 nm following excitation at 280 nm and 370 nm respectively. Particles fluorescent after both excitations are likely to be fluorescent primary biological aerosol particles (FBAP). Measured FBAP number concentration (NFBAP) at both sites exhibited clear diurnal cycles. The largest variability was observed in the understorey, where NFBAP reached a minimum of 50–100 L−1 in late morning. In mid afternoon it exhibited strong transient fluctuations as large as 4000 L−1 that were followed by sustained concentrations of 1000–2500 L−1 that reduced steadily between midnight and sunrise. Above the canopy FBAP number ranged from 50–100 L−1 during the daytime to 200–400 L−1 at night but did not exhibit the transient enhancements seen in the understorey. The strong FBAP fluctuations were attributed to the release of fungal spores below the canopy and appeared to be linked to elevated relative humidity. The mean FBAP number fraction in the size range 0.8 μm

Fluorescent biological aerosol particle concentrations and size distributions measured with an Ultraviolet Aerodynamic Particle Sizer (UV-APS) in Central Europe

Abstract. Primary Biological Aerosol Particles (PBAPs), including bacteria, spores and pollen, are essential for the spread of organisms and disease in the biosphere, and numerous studies have suggested that they may be important for atmospheric processes, including the formation of clouds and precipitation. The atmospheric abundance and size distribution of PBAPs, however, are largely unknown. At a semi-urban site in Mainz, Germany we used an Ultraviolet Aerodynamic Particle Sizer (UV-APS) to measure Fluorescent Biological Aerosol Particles (FBAPs), which provide an estimate of viable bioaerosol particles and can be regarded as an approximate lower limit for the actual abundance of PBAPs. Fluorescence of non-biological aerosol components are likely to influence the measurement results obtained for fine particles (<1 μm), but not for coarse particles (1–20 μm). Averaged over the four-month measurement period (August–December 2006), the mean number concentration of coarse FBAPs was ~3×10−2 cm−3, corresponding to ~4% of total coarse particle number. The mean mass concentration of FBAPs was ~1μg m−3, corresponding to ~20% of total coarse particle mass. The FBAP number size distributions exhibited alternating patterns with peaks at various diameters. A pronounced peak at ~3 μm was essentially always observed and can be described by the following campaign-average lognormal fit parameters: geometric mean diameter 3.2 μm, geometric standard deviation 1.3, number concentration 1.6×10−2 cm−3. This peak is likely due to fungal spores or agglomerated bacteria, and it exhibited a pronounced diel cycle (24-h) with maximum intensity during early/mid-morning. FBAP peaks around ~1.5 μm, ~5 μm, and ~13 μm were also observed, but less pronounced and less frequent. These may be single bacterial cells, larger fungal spores, and pollen grains, respectively. The observed number concentrations and characteristic sizes of FBAPs are consistent with microscopic, biological and chemical analyses of PBAPs in aerosol filter samples. To our knowledge, however, this is the first exploratory study reporting continuous online measurements of bioaerosol particles over several months and a range of characteristic size distribution patterns with a persistent bioaerosol peak at ~3 μm. The measurement results confirm that PBAPs account for a substantial proportion of coarse aerosol particle number and mass in continental boundary layer air. Moreover, they suggest that the number concentration of viable bioparticles is dominated by fungal spores or agglomerated bacteria with aerodynamic diameters around 3 μm rather than single bacterial cells with diameters around 1 μm.

Mass spectral characterization of submicron biogenic organic particles in the Amazon Basin

Submicron atmospheric particles in the Amazon Basin were characterized by a high‐resolution aerosol mass spectrometer during the wet season of 2008. Patterns in the mass spectra closely resembled those of secondary‐organic‐aerosol (SOA) particles formed in environmental chambers from biogenic precursor gases. In contrast, mass spectral indicators of primary biological aerosol particles (PBAPs) were insignificant, suggesting that PBAPs contributed negligibly to the submicron fraction of particles during the period of study. For 40% of the measurement periods, the mass spectra indicate that in‐Basin biogenic SOA production was the dominant source of the submicron mass fraction, contrasted to other periods (30%) during which out‐of‐Basin organic‐carbon sources were significant on top of the baseline in‐Basin processes. The in‐Basin periods had an average organic‐particle loading of 0.6 μg m−3 and an average elemental oxygen‐to‐carbon (O:C) ratio of 0.42, compared to 0.9 μg m−3 and 0.49, respectively, during periods of out‐of‐Basin influence. On the basis of the data, we conclude that most of the organic material composing submicron particles over the Basin derived from biogenic SOA production, a finding that is consistent with microscopy observations made in a concurrent study. This source was augmented during some periods by aged organic material delivered by long‐range transport.

Saccharide composition in atmospheric particulate matter in the southwest US and estimates of source contributions

Saccharide compositions were measured in ambient particulate matter (PM) samples collected at four sites in Eastern Texas and Central Arizona in an effort to assess the contribution from biomass burning, atmospheric entrainment of soil, and primary biological aerosol particles (PBAPs) in regions with different climate patterns and ecosystems. In spite of the concentration difference, samples from the four study sites showed similar saccharide composition and seasonal variation, with the only exception being trehalose, likely resulting from the influence of local climatic conditions. Comparison of samples at the Arizona site showed different saccharide enrichment patterns between PM2.5 and PM10, which is consistent with their proposed sources as determined by a correlation analysis between observations. A positive matrix factorization (PMF) model was used to resolve three saccharide-related source factors and their relative source contributions to ambient PM using saccharides as tracers. Both the correlation and PMF model results indicate a stronger influence from local biogenic sources on aerosol saccharides at the rural sites than the urban site in Texas, and a greater impact from the PBAP and other biologically derived sources for PM collected in the Arizona location. This paper will provide the first analysis of saccharides in both fine and coarse PM in two US regions with dramatically different climates and ecosystem and provide a characterization of the ambient aerosol sources.

Atmospheric budget of primary biological aerosol particles from fungal spores

The contribution of primary biological aerosol particles (PBAP) to the global budget of organic aerosol is poorly understood. Concentrations of mannitol, a biotracer for fungal spores, are used here to constrain the first global model (GEOS‐Chem) simulation of PBAP from fungi. Emissions are driven by leaf area index and atmospheric water vapor concentrations and are empirically optimized based on the geographical and seasonal variability of observed mannitol concentrations. Optimized global emissions total 28 Tg yr−1, with 25% of that total emitted as fine mode (PM2.5) aerosol. Fungal spores contribute 23% of total primary emissions of organic aerosol, or 7% of the fine‐mode source. Annual mean simulated surface concentrations of PBAP over vegetated regions range from 0.1–0.7 μgm−3 (PM2.5) and 0.4–3.0 μgm−3 (PM10), with the highest concentrations in the tropics, where PBAP may be the dominant source of organic aerosol. Further validation is required to reduce the substantial uncertainties on this budget.

Quantifying emissions of primary biological aerosol particle mass in Europe

Atmospheric concentration measurements of tracers for primary biological aerosol particles (PBAPs) have been used to obtain estimates of their release into the atmosphere. Emission flux data of surrogate compounds, for which concurrent concentration measurements were available, were used to quantify the release of PBAPs as PM 10 mass. Results indicate fungal spores to be the most important contributors. One other main source is plant debris. Area-based emission rates of 24 kg km −2 and year (range 6–90) have been assessed. Results scaled for Europe indicate a contribution of PBAPs to PM 10 concentrations in the low percentage range, with a maximum in summer when concentration levels are small. This is consistent with the range of measurements. Despite of the large uncertainties, results contribute to clarify the potential contribution of biological particles to global load of particle mass.

Ambient aerosol concentrations of sugars and sugar-alcohols at four different sites in Norway

Abstract. Sugars and sugar-alcohols are demonstrated to be important constituents of the ambient aerosol water-soluble organic carbon fraction, and to be tracers for primary biological aerosol particles (PBAP). In the present study, levels of four sugars (fructose, glucose, sucrose, trehalose) and three sugar-alcohols (arabitol, inositol, mannitol) in ambient aerosols have been quantified using a novel HPLC/HRMS-TOF (High Performance Liquid Chromatography in combination with High Resolution Mass Spectrometry – Time of Flight) method to assess the contribution of PBAP to PM>sub>10 and PM2.5. Samples were collected at four sites in Norway at different times of the year in order to reflect the various contributing sources and the spatial and seasonal variation of the selected compounds. Sugars and sugar-alcohols were present at all sites investigated, underlining the ubiquity of these highly polar organic compounds. The highest concentrations were reported for sucrose, reaching a maximum concentration of 320 ng m−3 in PM10 and 55 ng m−3 in PM2.5. The mean concentration of sucrose was up to 10 times higher than fructose, glucose and the dimeric sugar trehalose. The mean concentrations of the sugar-alcohols were typically lower, or equal, to that of the monomeric sugars and trehalose. Peak concentrations of arabitol and mannitol did not exceed 30 ng m−3 in PM10, and for PM2.5 all concentrations were below 6 ng m−3. Sugars and sugar-alcohols were associated primarily with coarse aerosols except during wintertime at the suburban site in Elverum, where a shift towards sub micron aerosols was observed. It is proposed that this shift was due to the intensive use of wood burning for residential heating at this site during winter, confirmed by high concurrent concentrations of levoglucosan. Elevated concentrations of sugars in PM2.5 were observed during spring and early summer at the rural background site Birkenes. It is hypothesized that this was due to ruptured pollen.

Organic compounds present in the natural Amazonian aerosol: Characterization by gas chromatography–mass spectrometry

As part of the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA)‐Cooperative LBA Airborne Regional Experiment (CLAIRE) 2001 campaign in July 2001, separate day and nighttime aerosol samples were collected at a ground‐based site in Amazonia, Brazil, in order to examine the composition and temporal variability of the natural “background” aerosol. We used a high‐volume sampler to separate the aerosol into fine (aerodynamic diameter, AD < 2.5 μm) and coarse (AD > 2.5 μm) size fractions and quantified a range of organic compounds in methanolic extracts of the samples by a gas chromatographic‐mass spectrometric technique. The carbon fraction of the compounds could account for an average of 7% of the organic carbon (OC) in both the fine and coarse aerosol fractions. We observed the highest concentrations of sugars, sugar alcohols, and fatty acids in the coarse aerosol samples, which suggests that these compounds are associated with primary biological aerosol particles (PBAP) observed in the forest atmosphere. Of these, trehalose, mannitol, arabitol, and the fatty acids were found to be more prevalent at night, coinciding with a nocturnal increase in PBAP in the 2–10 μm size range (predominantly yeasts and other small fungal spores). In contrast, glucose, fructose, and sucrose showed persistently higher daytime concentrations, coinciding with a daytime increase in large fungal spores, fern spores, pollen grains, and, to a lesser extent, plant fragments (generally >20 μm in diameter), probably driven by lowered relative humidity and enhanced wind speeds/convective activity during the day. For the fine aerosol samples a series of dicarboxylic and hydroxyacids were detected with persistently higher daytime concentrations, suggesting that photochemical production of a secondary organic aerosol from biogenic volatile organic compounds may have made a significant contribution to the fine aerosol. Anhydrosugars (levoglucosan, mannosan, galactosan), which are specific tracers for biomass burning, were detected only at low levels in the fine aerosol samples. On the basis of the levoglucosan‐to‐OC emission ratio measured for biomass burning aerosol, we estimate that an average of ∼16% of the OC in the fine aerosol was due to biomass burning during CLAIRE 2001, indicating that the major fraction was associated with biogenic particles.

Primary biological aerosol particles at the high alpine site of Jungfraujoch/Switzerland

Primary biological aerosol particles at the high alpine site of Jungfraujoch/Switzerland

The size distribution of primary biological aerosol particles in cloud water on the mountain Kleiner Feldberg/Taunus (FRG)

During the field campaign, FELDEX 95 cloud water samples were collected and the insoluble particles were analysed by single particle analysis in order to determine the content of primary biological aerosol particles (PBAP). It is found that 25% of the total insoluble particles are biological ones. During cloud events with increasing wind velocity, the concentration of biological particles also increases. Anthropogenic influence leads to a higher amount of both total and biological particles. Within the size distribution, the percentage of biological particles decreases with increasing radius.

The size distribution of primary biological aerosol particles in the multiphase atmosphere

Primary biological aerosol particles are a ubiquitouscomponent of the atmospheric aerosol and have greatimportance within the whole atmosphere. Besides theireffect on air hygiene (i.e. causing allergic diseases), theycontribute to cloud and rain development. They amountto almost 25% of the total number of aerosolparticles both in dry air and in cloudwater. They showno seasonal variation in concentration but incomposition.

Seasonal variation of primary biological aerosol particles in the remote continental region of Lake Baikal/Siberia

During a complete year (April 1996–April 1997) impactor measurements were performed in the remote continental region of Lake Baikal/Siberia and were analysed by single-particles analysis to determine the content of primary biological aerosol particles. The results show an amount of 20% of the number concentration and almost 30% of the volume concentration that were biological, with no seasonal variation. Distinct differences were seen looking at the giant particles ( r>2 μm), where strong phenological variations were seen within the size distributions.

The size distribution of marine atmospheric aerosol with regard to primary biological aerosol particles over the South Atlantic Ocean

The marine atmosphere is characterized by particles which originate from the ocean and by those which reached the air by advection from the continent. The bubble-burst mechanism produces both sea salt as well as biological particles. The following article describes the determination of the size distribution of marine aerosol particles with special emphasis on the biological particles. Th data were obtained on three cruises with the German Research Vessel “METEOR” crossing the South Atlantic Ocean. The measurements showed that biological particles amount to 17% in number and 10% in volume concentration. Another type of particle became obvious in the marine atmosphere, the biologically contaminated particle, i.e. particles which consist partly (approximately up to one-third) of biological matter. Their concentration in the evaluated size class ( r>2 μm) is higher than the concentration of the pure biological particles. The concentrations vary over about one to two orders of magnitude during all cruises.

Seasonal variation of primary biological aerosol particles in the remote continental region of lake baikal/sibiria

Seasonal variation of primary biological aerosol particles in the remote continental region of lake baikal/sibiria