On the sensitivity of particle size to relative humidity for Los Angeles aerosols

McMurry, Peter H.; Stolzenburg, Mark R.

doi:10.1016/0004-6981(89)90593-3

Cited by 279 publications

(184 citation statements)

References 22 publications

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“…Although the growth of particles with increasing relative humidity can depend strongly on particle material and size (McMurry and Stolzenburg, 1989 ), in some conditions the water uptake is a more simple function of relative humidity (Richards et al, 1999 ).…”

Section: Discussionmentioning

confidence: 99%

Photometrically measured continuous personal PM2.5 exposure: Levels and correlation to a gravimetric method

Lanki¹,

Alm²,

Ruuskanen

et al. 2002

J Expo Sci Environ Epidemiol

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There is evidence that hourly variations in exposure to airborne particulate matter ( PM ) may be associated with adverse health effects. Still there are only few published data on short -term levels of personal exposure to PM in community settings. The objectives of the study were to assess hourly and shorter -term variations in personal PM 2.5 exposure in Helsinki, Finland, and to compare results from portable photometers to simultaneously measured gravimetric concentrations. The effect of relative humidity on the photometric results was also evaluated. Personal PM 2.5 exposures of elderly persons were assessed for 24 h every second week, resulting in 308 successful measurements from 47 different subjects. Large changes in concentrations in minutes after cooking or changing microenvironment were seen. The median of daily 1 -h maxima was over twice the median of 24 -h averages. There was a strong significant association between the two means, which was not linear. Median ( 95th percentile ) of the photometric 24 -h concentrations was 12.1 ( 37.7 ) and of the 24 -h gravimetric concentrations 9.2 ( 21.3 ) g / m 3 . The correlation between the photometric and the gravimetric method was quite good ( R 2 = 0.86 ). Participants spent 94.1% of their time indoors or in a vehicle, where relative humidity is usually low and thus not likely to cause significant effects on photometric results. Even outdoors, the relative humidity had only modest effect on concentrations. Photometers are a promising method to explore the health effects of short -term variation in personal PM 2.5 exposure.

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Section: Discussionmentioning

confidence: 99%

Photometrically measured continuous personal PM2.5 exposure: Levels and correlation to a gravimetric method

Lanki¹,

Alm²,

Ruuskanen

et al. 2002

J Expo Sci Environ Epidemiol

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“…This multi-investigator study involved a comprehensive characterization of aerosol chemical characteristics, with a particular emphasis on organic speciation. In the present paper we utilize data from the tandem differential mobility analyzer (TDMA) [McMurry and Stolzenburg, 1989] to infer relative humidity-dependent water content for particles of several sizes, and data from several sampling systems to infer the sizedependent aerosol composition. In the SEAVS study, atmospheric particles were dried to approximately 5 + 2% RH (RH1) before entering DMA1.…”

Section: Methodsmentioning

confidence: 99%

“…The method consists of calculating the difference, as a function of the organic mass fraction, between water content measured using the tandem differential mobility analyzer (TDMA) technique [McMurry and Stolzenburg, 1989] and water estimated for the inorganic fraction of the aerosol. Whereas Saxena et al [1995] focused on relationships between organic mass fractions and "excess" water for RH=80-88%, we have ventured to estimate complete water activity curves (RH=5-85%) for organics measured during SEAVS.…”

Section: Introductionmentioning

confidence: 99%

Estimation of water uptake by organic compounds in submicron aerosols measured during the Southeastern Aerosol and Visibility Study

Dick¹,

Saxena²,

McMurry³

2000

J. Geophys. Res.

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190

176

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Abstract. In situ measurements of size-dependent water uptake by atmospheric particles made with a tandem differential mobility analyzer (TDMA) and size-resolved chemical composition of aerosol samples collected with cascade impactors in the Smoky Mountains have been examined in order to ascertain the influence of organic carbon compounds on aerosol hygroscopicity. Particles were dried to -5 % relative humidity (RH) before entering the TDMA, leading us to believe that salts of ammonium and sulfate were in crystalline states for relative humidities below their expected deliquescent points. TDMA-measured water content was found to be in excess of the sulfate-associated water modeled using laboratory data for binary aqueous solutions and the method of Zdanovskii-Stokes-Robinson for multicomponent solutions over a wide range of humidities (RH=5-85%). Furthermore, excess water was observed to increase in proportion to the organic fraction of mass associated with each examined size in the range 0.05 to 0.4 gm. These data are used to obtain an empirical relationship between the amount of water associated with particulate organics and relative humidity. This analysis shows that organic-associated water content is considerably less than that of sulfate compounds, on a volume basis, for high RH, but comparable or greater for low RH. These results are consistent with laboratory data for water absorption by a range of organics vis-h-vis ammonium salts of sulfate.

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“…For a well-characterized particle distribution, Chakrabarti et al and Sioutas et al provide empirical evidence of pDR adherence to theoretical trend regarding sensitivity of scattering signal to relative humidity. However, strong dependence of humidity-induced distortion of the optical signal on particle size and composition precludes applying a theoretically-derived humidity correction where the particles of interest are not physically and chemically well-characterized (McMurry and Stolzenburg, 1989), such as rural kitchens in which several fuels as well as tobacco are burned, humidity conditions can fall below 30% and often peak above 90%, and diurnal particle concentrations can range from o50 mg/m 3 to several thousand mg/m 3 .…”

Section: Scope Of This Papermentioning

confidence: 99%

Field performance of a nephelometer in rural kitchens: effects of high humidity excursions and correlations to gravimetric analyses

Fischer¹,

Koshland²

2006

J Expo Sci Environ Epidemiol

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Rural kitchens of solid-fuel burning households constitute the microenvironment responsible for the majority of human exposures to health-damaging air pollutants, particularly respirable particles and carbon monoxide. Portable nephelometers facilitate cheaper, more precise, time-resolved characterization of particles in rural homes than are attainable by gravitational methods alone. However, field performance of nephelometers must contend with aerosols that are highly variable in terms of chemical content, size, and relative humidity. Previous field validations of nephelometer performance in residential settings explore relatively low particle concentrations, with the vast majority of 24-h average gravitational PM 2.5 concentrations falling below 40 mg/m 3 . We investigate relationships between 24-h gravitational particle measurements and nephelometric data logged by the personal DataRAM (pDR) in highly polluted rural Chinese kitchens, where gravitationally determined 24-h average respirable particle concentrations were as high as 700 mg/m 3 . We find that where relative humidity remained below 95%, nephelometric response was strongly linear despite complex mixtures of aerosols and variable ambient conditions. Where 95% relative humidity was exceeded for even a brief duration, nephelometrically determined 24-h mean particle concentrations were nonsystematically distorted relative to gravitational data, and neither concurrent relative humidity measurements nor use of robust statistical measures of central tendency offered means of correction. This nonsystematic distortion is particularly problematic for rural exposure assessment studies, which emphasize upper quantiles of time-resolved particle measurements within 24-h samples. Precise, accurate interpretation of nephelometrically resolved short-term particle concentrations requires calibration based on short-term gravitational sampling.

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On the sensitivity of particle size to relative humidity for Los Angeles aerosols

Cited by 279 publications

References 22 publications

Photometrically measured continuous personal PM2.5 exposure: Levels and correlation to a gravimetric method

Photometrically measured continuous personal PM2.5 exposure: Levels and correlation to a gravimetric method

Estimation of water uptake by organic compounds in submicron aerosols measured during the Southeastern Aerosol and Visibility Study

Field performance of a nephelometer in rural kitchens: effects of high humidity excursions and correlations to gravimetric analyses

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