19 research outputs found
Associations between fine particulate matter components and daily mortality in Nagoya, Japan
Background: Seasonal variation and regional heterogeneity have been observed in the estimated effect of fine particulate matter (PM2.5) mass on mortality. Differences in the chemical compositions of PM2.5 may cause this variation. We investigated the association of the daily concentration of PM2.5 components with mortality in Nagoya, Japan. Methods: We combined daily mortality counts for all residents aged 65 years and older with concentration data for PM2.5 mass and components in Nagoya from April 2003 to December 2007. A time-stratified case-crossover design was used to examine the association of daily mortality with PM2.5 mass and each component (chloride, nitrate, sulfate, sodium, potassium, calcium, magnesium, ammonium, elemental carbon [EC], and organic carbon [OC]). Results: We found a stronger association between mortality and PM2.5 mass in transitional seasons. In analysis for each PM2.5 component, sulfate, nitrate, chloride, ammonium, potassium, EC, and OC were significantly associated with mortality in a single-pollutant model. In a multi-pollutant model, an interquartile range increase in the concentration of sulfate was marginally associated with an increase in all-cause mortality of 2.1% (95% confidence interval, -0.1 to 4.4). Conclusions: These findings suggest that some specific PM components have a more hazardous effect than others and contribute to seasonal variation in the health effects of PM2.5
Approaches to the source evaluation of chlorinated polycyclic aromatic hydrocarbons in fine particles
Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) have been recognized as novel hazardous pollutants; however, the dominant sources remain unclear. This study investigates the occurrences of ClPAHs in five stages of size-segregated particles collected from an urban site and evaluates the sources and factors affecting the concentrations using organic and inorganic source tracers. ClPAHs are the most frequently detected in the finest particle fraction (less than 1.1 ”m; PM1.1), similar to polycyclic aromatic hydrocarbons (PAHs), hopanes, and levoglucosan (LEV). The concentrations of total ClPAHs in PM1.1 shows a significant correlation (p < 0.05) with those of total PAHs and specific hopanes but not to LEV and biogenic fatty acids; this suggests that ClPAHs dominantly originate from industrial activities and vehicular emissions. Heatmap analysis, including source tracers, is used to categorize the possible sources of ClPAHs into three types: ClPAH-specific sources, local industrial activities and vehicular emissions, and remote industrial activities. Furthermore, correlation network analysis is used to clarify the relationships between the pollutants
Optimisation of pre-treatment and ionisation for GC/MS analysis for the determination of chlorinated PAHs in atmospheric particulate samples
<div><p>Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) have been discovered to represent ubiquitous environmental pollutants in the last decade. In the present study, sample pre-treatment and ionisation conditions associated with the gas chromatography/mass spectrometry (GC/MS) analysis of ClPAHs were evaluated. The optimal pre-treatment of ambient air particulate samples was achieved using fractionation over silica gel with 10% dichloromethane in n-hexane as the eluent. The optimised condition of GC/MS with electron impact ionisation permitted analysis of all target ClPAHs. Not all target ClPAHs were detected using GC/MS with negative chemical ionisation, although this technique exhibited greater sensitivity for several of the compounds compared to electron impact ionisation. The analytical method was applied to the survey of ClPAHs in atmospheric particulate matter obtained close to an industrial site and in a standard sample of tunnel dust. Fourteen and eighteen species of ClPAHs were detected in the industrial air samples and tunnel dust, respectively, confirming the capability of the method. The compositions of ClPAHs were significantly different between air samples and tunnel dust. It suggests that alternative emission sources rather than vehicle exhaust could play a significant role in the air.</p></div
Light Absorption and ExcitationâEmission Fluorescence of Urban Organic Aerosol Components and Their Relationship to Chemical Structure
The
present study used a combination of solvent and solid-phase
extractions to fractionate organic compounds with different polarities
from total suspended particulates in Nagoya, Japan, and their optical
characteristics were obtained on the basis of their UVâvisible
absorption spectra and excitationâemission matrices (EEMs).
The relationship between their optical characteristics and chemical
structures was investigated based on high-resolution aerosol mass
spectra (HR-AMS spectra), soft ionization mass spectra and Fourier
transform infrared (FT-IR) spectra. The major light-absorption organics
were less polar organic fractions, which tended to have higher mass
absorption efficiencies (MAEs) and lower wavelength dependent Ă
ngstroÌm
exponents (Ă
) than the more polar organic fractions. Correlation
analyses indicate that organic compounds with O and N atoms may contribute
largely to the total light absorption and fluorescence of the organic
aerosol components. The extracts from the aerosol samples were further
characterized by a classification of the EEM profiles using a PARAFAC
model. Different fluorescence components in the aerosol organic EEMs
were associated with specific AMS ions and with different functional
groups from the FT-IR analysis. These results may be useful to determine
and further classify the chromophores in atmospheric organic aerosols
using EEM spectroscopy
Four- and Five-Carbon Dicarboxylic Acids Present in Secondary Organic Aerosol Produced from Anthropogenic and Biogenic Volatile Organic Compounds
To better understand precursors of dicarboxylic acids in ambient secondary organic aerosol (SOA), we studied C4âC9 dicarboxylic acids present in SOA formed from the oxidation of toluene, naphthalene, α-pinene, and isoprene. C4âC9 dicarboxylic acids present in SOA were analyzed by offline derivatization gas chromatographyâmass spectrometry. We revealed that C4 dicarboxylic acids including succinic acid, maleic acid, fumaric acid, malic acid, DL-tartaric acid, and meso-tartaric acid are produced by the photooxidation of toluene. Since meso-tartaric acid barely occurs in nature, it is a potential aerosol tracer of photochemical reaction products. In SOA particles from toluene, we also detected a compound and its isomer with similar mass spectra to methyltartaric acid standard; the compound and the isomer are tentatively identified as 2,3-dihydroxypentanedioic acid isomers. The ratio of detected C4âC5 dicarboxylic acids to total toluene SOA mass had no significant dependence on the initial VOC/NOx condition. Trace levels of maleic acid and fumaric acid were detected during the photooxidation of naphthalene. Malic acid was produced from the oxidation of α-pinene and isoprene. A trace amount of succinic acid was detected in the SOA produced from the oxidation of isoprene
Organic Molecular Tracers in PM2.5 at Urban Sites during Spring and Summer in Japan: Impact of Secondary Organic Aerosols on Water-Soluble Organic Carbon
To understand the characteristics of secondary organic aerosols (SOAs) and estimate their impact on water-soluble organic carbon (WSOC) in urban areas in Japan, we measured 17 organic tracers using gas chromatographyâmass spectrometry from particulate matter with an aerodynamic diameter smaller than 2.5 ÎŒm collected at five urban sites in Japan during spring and summer. Most anthropogenic, monoterpene-derived, and isoprene-derived SOA tracers showed meaningful correlations with potential ozone in both these seasons. These results indicate that oxidants play an important role in SOAs produced during both seasons in urban cities in Japan. WSOC was significantly affected by anthropogenic and monoterpene-derived SOAs during spring and three SOA groups during summer at most of the sites sampled. The total estimated secondary organic carbons (SOCs), including mono-aromatic, di-aromatic, monoterpene-derived, and isoprene-derived SOCs, could explain the WSOC fractions of 39â63% in spring and 46â54% in summer at each site. Notably, monoterpene-derived and mono-aromatic SOCs accounted for most of the total estimated SOCs in both spring (85â93%) and summer (75â82%) at each site. These results indicate that SOAs significantly impact WSOC concentrations during both these seasons at urban sites in Japan
Four- and Five-Carbon Dicarboxylic Acids Present in Secondary Organic Aerosol Produced from Anthropogenic and Biogenic Volatile Organic Compounds
To better understand precursors of dicarboxylic acids in ambient secondary organic aerosol (SOA), we studied C4–C9 dicarboxylic acids present in SOA formed from the oxidation of toluene, naphthalene, α-pinene, and isoprene. C4–C9 dicarboxylic acids present in SOA were analyzed by offline derivatization gas chromatography–mass spectrometry. We revealed that C4 dicarboxylic acids including succinic acid, maleic acid, fumaric acid, malic acid, DL-tartaric acid, and meso-tartaric acid are produced by the photooxidation of toluene. Since meso-tartaric acid barely occurs in nature, it is a potential aerosol tracer of photochemical reaction products. In SOA particles from toluene, we also detected a compound and its isomer with similar mass spectra to methyltartaric acid standard; the compound and the isomer are tentatively identified as 2,3-dihydroxypentanedioic acid isomers. The ratio of detected C4–C5 dicarboxylic acids to total toluene SOA mass had no significant dependence on the initial VOC/NOx condition. Trace levels of maleic acid and fumaric acid were detected during the photooxidation of naphthalene. Malic acid was produced from the oxidation of α-pinene and isoprene. A trace amount of succinic acid was detected in the SOA produced from the oxidation of isoprene
Chemical Structural Characteristics of HULIS and Other Fractionated Organic Matter in Urban Aerosols: Results from Mass Spectral and FT-IR Analysis
The
chemical characteristics of complex organic matter in atmospheric
aerosols remain poorly understood. Water-insoluble organic matter
(WISOM) and water-soluble organic matter (WSOM) in the total suspended
particulates collected in the city of Nagoya in summer/early autumn
and winter were extracted using multiple solvents. Two fractions of
humic-like substances, showing neutral and acidic behavior (HULIS-n
and HULIS-a, respectively), and the remaining highly polar part (HP-WSOM)
were fractionated from WSOM using solid phase extraction. The chemical
structural characteristics and concentrations of the organic matter
were investigated using mass spectrometry and Fourier transform infrared
(FT-IR) spectroscopy. WISOM and HULIS-n had low O/C ratios (0.1 and
0.4, respectively) and accounted for a large fraction of the organics
in aerosols (70%). HULIS-a and HP-WSOM had higher O/C ratios (0.7
and 1.0, respectively), and their concentrations in summer and early
autumn were on average âŒ2 times higher than those in winter.
The mass spectrum and FT-IR analyses suggest the following: (1) WISOM
were high-molecular-weight aliphatics (primarily C<sub>27</sub>âC<sub>32</sub>) with small proportions of âCH<sub>3</sub>, âOH,
and Cî»O groups; (2) HULIS-n was abundant in aliphatic structures
and hydroxyl groups (primarily C<sub>9</sub>âC<sub>18</sub>) and by branched structures; (3) HULIS-a and HP-WSOM contained relatively
large amounts of low-molecular-weight carboxylic acids and alcohols
(primarily C<sub>4</sub>âC<sub>10</sub>); and (4) WISOM and
HULIS-n were relatively abundant in amines and organic nitrates