Exceeding of Henry's Law by Hydrogen Peroxide Associated with Urban Aerosols
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- 作者：Chuautemoc Arellanes ; Suzanne E. Paulson ; Philip M. Fine ; Constantinos Sioutas
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：August 15, 2006
- 年：2006
- 卷：40
- 期：16
- 页码：4859 - 4866
- 全文大小：198K
- 年卷期：v.40,no.16(August 15, 2006)
- ISSN：1520-5851
文摘
Simultaneous measurements of gas- and aerosol-phasehydrogen peroxide (H2O2) have been made at two sites inLos Angeles, one near the Pacific coast at the Universityof California at Los Angeles (UCLA), and the other in downtownLos Angeles with close proximity to a heavily traveledfreeway (freeway site). At both the freeway and UCLA sites,gas-phase H2O2 levels were similar, averaging 1.17 ± 1.0and 1.05 ± 0.6 ppb, respectively. The particle-associatedH2O2 in both fine (PM2.5) and coarse (>PM2.5) modeswas higher at the freeway site, as compared to UCLA, bya factor of 2. However, when aerosol-phase H2O2 isnormalized to particle mass loadings, the fine-mode H2O2levels are very similar at the two sites: 0.42 ± 0.3 and 0.58± 0.3 ng H2O2/
g particle mass at the freeway andUCLA sites, respectively. The normalized coarse-modeH2O2 levels were significantly higher at the freeway sitethan at UCLA, 1.05 ± 0.3 and 0.51 ± 0.3 ng/g, respectively.Estimating aerosol liquid water content on the basis ofrelative humidity and aerosol mass, a calculated equivalentH2O2 in aerosol liquid water averages 70 mM, more than2 orders of magnitude higher than concentrations predictedby gas-particle partitioning (Henry's law), which averages0.1 mM. This indicates that the sampled particles arecapable of generating H2O2 in aqueous solution. Thesecorresponding aqueous-phase H2O2 concentrations in aerosolliquid water exceed levels that have been observed toproduce cellular damage to lung epithelial cells in laboratoryexperiments by at least 3 orders of magnitude. Althoughmost measurements of H2O2 in particles were made usingan extraction solution adjusted to pH 3.5, a set ofmeasurements indicates that H2O2 from fine-mode particlesextracted in the physiologically relevant pH range 5-7.5also generate H2O2 with only slightly lowered efficiency;coarse-mode H2O2 production dropped by 75% at theupper end of this range. Finally, a small set of measurementswas performed to investigate the degree to which therecently developed Versatile Aerosol Concentrator EnrichmentSystem (VACES) affects H2O2 levels in concentratedambient aerosols. The VACES appeared to a have minimalimpact on particulate H2O2.
g particle mass at the freeway andUCLA sites, respectively. The normalized coarse-modeH2O2 levels were significantly higher at the freeway sitethan at UCLA, 1.05 ± 0.3 and 0.51 ± 0.3 ng/g, respectively.Estimating aerosol liquid water content on the basis ofrelative humidity and aerosol mass, a calculated equivalentH2O2 in aerosol liquid water averages 70 mM, more than2 orders of magnitude higher than concentrations predictedby gas-particle partitioning (Henry's law), which averages0.1 mM. This indicates that the sampled particles arecapable of generating H2O2 in aqueous solution. Thesecorresponding aqueous-phase H2O2 concentrations in aerosolliquid water exceed levels that have been observed toproduce cellular damage to lung epithelial cells in laboratoryexperiments by at least 3 orders of magnitude. Althoughmost measurements of H2O2 in particles were made usingan extraction solution adjusted to pH 3.5, a set ofmeasurements indicates that H2O2 from fine-mode particlesextracted in the physiologically relevant pH range 5-7.5also generate H2O2 with only slightly lowered efficiency;coarse-mode H2O2 production dropped by 75% at theupper end of this range. Finally, a small set of measurementswas performed to investigate the degree to which therecently developed Versatile Aerosol Concentrator EnrichmentSystem (VACES) affects H2O2 levels in concentratedambient aerosols. The VACES appeared to a have minimalimpact on particulate H2O2.