Rural continental aerosol properties and processes observed during the Hohenpeissenberg Aerosol Characterization Experiment (HAZE2002)

Abstract

Abstract. Detailed investigations of the chemical and microphysical properties of rural continental aerosols were performed during the HAZE2002 experiment, which was conducted in May 2002 at the Meteorological Observatory Hohenpeissenberg (DWD) in Southern Germany. The online measurement data and techniques included: size-resolved chemical composition of submicron particles by aerosol mass spectrometry (AMS); total particle number concentrations and size distributions over the diameter range of 3 nm to 9 μm (CPC, SMPS, OPC); monoterpenes determined by gas chromatography- ion trap mass spectrometry; OH and H2SO4 determined by atmospheric pressure chemical ionization mass spectrometry (CIMS). Filter sampling and offline analytical techniques were used to determine: fine particle mass (PM2.5), organic, elemental and total carbon in PM2.5 (OC2.5, EC2.5, TC2.5), and selected organic compounds (dicarboxylic acids, polycyclic aromatic hydrocarbons, proteins). Overall, the non-refractory components of submicron particles detected by aerosol mass spectrometry (PM1, 6.6±5.4 μg m−3, arithmetic mean and standard deviation) accounted for ~62% of PM2.5 determined by filter gravimetry (10.6±4.7 μg m−3). The relative proportions of non-refractory submicron particle components were: 11% ammonium, 19% nitrate, 20% sulfate, and 50% organics (OM1). In spite of strongly changing meteorological conditions and absolute concentration levels of particulate matter (3–13 μg m−3 PM1), OM1 was closely correlated with PM1 (r2=0.9) indicating a near-constant ratio of non-refractory organics and inorganics. In contrast, the ratio of nitrate to sulfate was highly dependent on temperature (14–32°C) and relative humidity (20–100%), which could be explained by thermodynamic model calculations of NH3/HNO3/NH4NO3 gas-particle partitioning. From the combination of optical and other sizing techniques (OPC, AMS, SMPS), an average refractive index of 1.40–1.45 was inferred for the measured rural aerosol particles. The average ratio of OM1 to OC2.5 was 2, indicating a high proportion of heteroelements in the organic fraction of the sampled rural aerosol. This is consistent with the high ratio of oxygenated organic aerosol (OOA) over hydrocarbon-like organic aerosol (HOA) inferred from the AMS results (4:1), and also with the high abundance of proteins (~3%) indicating a high proportion of primary biological material (~30%) in PM2.5. Moreover, the low abundance of PAHs (<1 ng m−3) and EC (<1 μg m−3) in PM2.5 confirm a low contribution of combustion emissions, which are usually also major sources for HOA. Slightly enhanced HOA concentrations indicating fresh anthropogenic emissions were observed during a period when air masses were advected from the densely populated Po Valley, Italy. Detection of several secondary organic aerosol compounds (dicarboxylic acids) and their precursors (monoterpenes) confirmed the finding that secondary aerosol from natural sources was an important aerosol constituent. A sharp decrease of the short lived monoterpenes indicated that during night-time the measurement station was isolated from ground emission sources by a stable inversion layer. Nighttime values can therefore be regarded to represent regional or long range transport. New particle formation was observed almost every day with particle number concentrations exceeding 104 cm−3 (nighttime background level 1000–2000 cm−3). Closer inspection of two major events indicated that ternary H2SO4/H2O/NH3 nucleation triggered particle formation and that condensation of both organic and inorganic species contributed to particle growth.

Aerosol layers from the 2008 eruptions of Mount Okmok and Mount Kasatochi: In situ upper troposphere and lower stratosphere measurements of sulfate and organics over Europe

“…The m/z 44/OA ratio increases from 0.16 ± 0.003 (0.69 ± 0.022, equivalent O/C) in the free troposphere to 0.21 ± 0.004 (0.88 ± 0.019, equivalent O/C) in the upper troposphere and lower stratosphere, where m/z 29 makes up 45%, and m/z 44 contributes 21% to the total organic mass. Although the contribution of m/z 29 is higher than observed in other data, such organic mass spectra can be identified with the type “OOA‐1” [ Lanz et al , 2007; Ulbrich et al , 2009] or “LV‐OOA” (low‐volatile OOA) [ Jimenez et al , 2009] and similar mass spectra have been observed in the free troposphere before [ Hock et al , 2008]. In the volcanic aerosol layer, the ratio is slightly lower with 0.16 ± 0.003 (0.69 ± 0.021, equivalent O/C).…”

Characterization of aerosol associated with enhanced small particle number concentrations in a suburban forested environment

“…In a more polluted atmosphere near Pittsburgh, PA, ammonium and sulfate contributed the majority of condensable mass during the early stages of growth events; however, photochemically produced secondary organic aerosol (SOA) contributed significantly to growth during later stages of these events [Zhang et al, 2004[Zhang et al, , 2005. In contrast, Hock et al [2008] observed a growth event in rural southern Germany with significant mass contribution from aerosol nitrate.…”

High diversity of fungi in air particulate matter

“…atmospheric aerosol ͉ bioaerosol ͉ DNA analysis ͉ fungal spores R ecent studies have shown that fungal spores and other biological particles can account for large proportions of aerosol particle mass in pristine rainforest air as well as in rural and urban environments (1)(2)(3)(4)(5). For example, fungal spores were found to account for up to 45% of coarse particle mass (Ͼ1 m) in tropical rainforest air and up to 4-11% of fine particle mass (Յ2.5 m) in urban and rural air (3).…”