The formation and growth of atmospheric nanoparticles has been the subject of intense study in recent years. Although sulfuric acid and water have been recognized as key ingredients in new particle formation in the atmosphere, organic species are thought to contribute to the phenomenon. Among hundreds of organic species, amines have been recently proposed as candidates which play important roles in new particle formation. In this article, recent field, laboratory and computational studies on the effects of amines in the formation and growth of atmospheric nanoparticles are briefly reviewed.
Aerosol particles play an important role in radiation balance in the atmosphere by scattering and absorbing incident light. It has recently been suggested that some organic aerosols “brown carbon” can absorb solar radiation, especially at the shorter visible and UV wavelengths, and possibly contribute to the radiation balance and photochemical reactions. In this article, optical parameters and techniques to measure aerosol light absorption are briefly overviewed and recent laboratory and field studies on optical properties of brown carbon are reviewed in order to reveal its sources and contributions.
Over the past decade, considerable progress has been made in understanding sources and formation processes of water-soluble organic aerosol (OA) in the atmosphere. This review article discusses the current knowledge on chemical characteristics, formation processes, and physical properties of water-soluble OA. In particular, organic aerosols formed in cloud and aerosol water are suggested to contribute substantially to OA mass. The review emphasizes the important roles of water-soluble organics in secondary OA formation including aqueous-phase reactions through field and laboratory studies.
Cloud condensation nuclei (CCN) activity of aerosol particles is important in determining the cloud formation processes, their properties, and their fate. In particular, organic material (OM) occupies a significant portion of aerosol particles, while their CCN activity is still difficult to predict. This review focuses on CCN activity of OM. A theoretical background is provided based on the Köhler theory. CCN activities of pure compounds are summarized to provide a detail comparison with the theory and experiments, including the limitations in the current experimental procedures. It is discussed how recent advances in laboratory experiments improved our understanding on CCN activity of secondary OM. Observations are always necessary to understand atmospheric aerosol particles. CCN activity of OM derived from observations is also discussed. Finally, open questions for future research are provided.
In this manuscript, we briefly introduce X-ray absorption fine structure (XAFS: X-ray Absorption Fine Structure) as a speciation method of metal ions in aerosols. As an application, research on the Ca and Zn speciation related to their metal-oxalate complexes is introduced. Oxalic acid, one of the most dominant components of organic aerosols, has cooling effect on the Earth’s radiation budget by acting as cloud condensation nuclei (CCN) activator. However, it is uncertain whether the oxalic acid can exist as protonated form, dissociated form, or metal complexes in aerosols, though there is a large difference in their water-solubility. In this sense, XAFS is a powerful tool to quantify the amount of metal-oxalate complexes. As a result, Ca and Zn oxalates were observed in finer particles from Ca and Zn K-edge XAFS. Based on the total concentrations of oxalate, Ca, and Zn with speciation of Ca and Zn determined by XAFS, we found that Ca and Zn oxalate fractions reached about 20-80% of total oxalate in finer particles. Since Ca and Zn oxalates are highly insoluble, the results showed that the complexes cannot act as CCN activator and that the ability of oxalic acid as CCN activator must be evaluated by considering the formation of insoluble metal oxalate complexes.
We have developed a global simulation of secondary organic aerosol (SOA) in a chemistry-aerosol coupled climate model (MIROC-CHASER-SPRINTARS). In this study, the model considers SOA production from terpenes, isoprene, and aromatics in biogenic/anthropogenic emissions (103, 400, and 18 TgC yr-1, respectively). The simulated SOA concentrations are generally consistent with the observations in the tropics, but significantly underestimated in comparison with the observations in the mid-high latitudes in the northern hemisphere. The global SOA production is estimated at 25 Tg yr-1, mainly from isoprene oxidation with OH (～60%) and terpenes oxidation with O3 and NO3 (15 and 13%, respectively). This study also suggests that the past SOA changes due to the land use change (during the 20th century) can cause a very large positive radiative forcing (～0.4 W m-2) through direct and indirect effects.
We intensively monitored gas and aerosol compositions near a national road, Route 463, in Saitama, Japan in March 2010. Submicron aerosol composition was measured with a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a multi-angle absorption photometer (MAAP). Gas-phase measurements were performed with a typical chemiluminescence instrument for detecting NOX and a proton transfer reaction mass spectrometer (PTR-MS) for volatile organic compounds (VOCs). NOX concentrations were highly correlated with black carbon (BC) concentrations (r=0.919, n=223, p<0.01) near the road; in contrast, NOX were poorly correlated with organic aerosol (OA) concentrations (r=0.439, n=184, p<0.1). HR-ToF-AMS measurements facilitated the determination of organic-mass-to-carbon ratio (average 1.36, range 1.25-1.50) and oxygen-to-carbon (O/C) ratio (average 0.18, range 0.08-0.29). This study also demonstrates the utility of chemical mass balance (CMB) analysis with SOA and POA mass spectra as source data to determine the apportionment of secondary OA (SOA) and primary OA (POA) within OA and the source contributions. Positive matrix factorization (PMF) analysis apportioned oxygenated OA (OOA) and hydrocarbon-like OA (HOA) within the OA samples. The SOA/OA and OOA/OA ratios obtained by these two models were 34% and 43%, respectively. These results indicate that not only traffic-related sources but also SOA, including aged OA, contributed substantially to OA concentrations observed at the roadside.
Recently, prevalence of Japanese cedar pollinosis has been increasing, and it is observed highly in the Kanto area of Japan. As a cause of the high prevalence in Kanto area, we focused attention on 3-nitrotyrosines contained in allergen protein that cause the immune reactions and enhance an immunogenicity of allergen proteins. In this study, we measured the size distribution of airborne Cry j 1 concentrations and the relative quantities of airborne Cry j 1 containing 3-nitrotyrosine; and evaluated an apoptosis inducibility of 3-nitrotyrosine for HeLa cell. Cry j 1 were highly observed as fine particles (≦1.1 µm) in the urban atmosphere of Saitama city, Japan. We succeeded for the first time in detecting Cry j 1 containing 3-nitrotyrosine in the urban atmosphere as the probable evidence of chemical modification of Cry j 1 by air pollutants. Cry j 1 that exists in the particle sizes smaller than 7.0 µm contained higher probabilities of 3-nitrotyrosine residues compared with Cry j 1 in the particle sizes larger than 7.0 µm. Moreover, we clarified that 3-nitrotyrosine induces HeLa cell (epidermoid cell) apoptosis. From these results, it is suggested that further investigations are needed for the behavior and health effect of Cry j 1 and Cry j 1 containing 3-nitrotyrosine in respirable particles.
This study is aimed at finding the sterilization effect of electrostatic atomized water particles. We selected Serratia marcescens as a target bacteria,since it causes nosocomminal infections and opportunistic infections. We observed morphological changes of Serratia marcescens using a transmission electron microscope (TEM) after exposure to Electrostatic Atomized Water Particles. It was found that the electrostatic atomized water particles can inactivate Serratia marcescens at a high efficiency (98.7%) within 90 minutes. We observed that the outer membrane of Serratia marcescens is seriously damaged by the exposure to electrostatic atomized water particles for 90 minutes. Further study is needed to clarify what action of the electrostatic atomized water particles causes this morphological change in Serratia marcescens.
Generation of sulfuric acid from air containing SO2 and the growth of sulfuric acid aerosol are an important process in the formation of atmospheric aerosol. In this study, laboratory experiments on photo-oxidation of SO2 and generation of secondary sulfuric acid aerosol were carried out. Numerical model on the growth of binary component aerosol of water and sulfuric acid was also developed. The model calculation of generation and growth of secondary sulfuric aerosol was conducted by coupling the aerosol growth model with both overall reaction model of generation of sulfuric acid from SO2 and parameterized homogeneous binary nucleation model. As expected, the present model calculation underestimated the particle growth because the condensation and evaporation of water vapor were not included. However, the model calculations successfully explained the decrease in number concentration and increase in particle size at longer residence time qualitatively.
Measurement of cleanliness recovery performance in non-unidirectional cleanrooms is described in ISO14644-3 (2005). However, evaluated results sometimes differ due to the selection of measuring points. In this work, the method to select proper points to perform the cleanliness recovery test was proposed. Distribution of airflow and local ventilation efficiency in various types of cleanrooms were simulated using CFD technique, and the relationship between local airflow speed and SVE3 (the 3rd. Scale for Ventilation Efficiency) was studied. As a result, proper evaluation was achieved when the measuring points at which airflow speed did not exceed 20% of supply air velocity were selected. Through study of various types of cleanrooms, this method was found to be applicable to most types of non-unidirectional cleanrooms, but not applicable to vector flow cleanrooms.