A two-parameter Weibull function to describe airborne dust particle size distributions

Autor: Ted M. Zobeck, Thomas W. Popham, Thomas E. Gill
Rok vydání: 1999
Předmět:
Zdroj: Earth Surface Processes and Landforms. 24:943-955
ISSN: 1096-9837
0197-9337
DOI: 10.1002/(sici)1096-9837(199909)24:10<943::aid-esp30>3.0.co;2-9
Popis: A number of mathematical distributions have been proposed for the description of the particle size distribution of unconsolidated sediments. However, few studies have mathematically described aeolian dust particle size distributions. RecentworkhasshownmathematicallyhowthesequentialfragmentationofmaterialsleadstoaWeibulldistribution.Since the breakage of aggregates by saltating grains is a primary mode of aeolian dust production, we test the hypothesis that the Weibull distribution may be used to describe airborne soil grains. Surface samples were collected from 52 sites including soils,dirtroadsandroadsideditchesintheSouthernHighPlainsofwestTexas.ThesamplesweretumbledintheLubbock dust generation, sampling and analysis system to generate a dust cloud. The particle size distribution of the dust was measuredinsitubylaserdiffractionandPM10concentrationwasdeterminedgravimetrically(PM10 = airborneparticulate matter with diameter10 m). This study demonstrated that the Weibull cumulative distribution function (c.d.f.) is an excellentchoicetodescribetheparticlesizedistributionofdustsuspendedfrommineralsediment.AWeibullc.d.f.usedto describethedustcloudsizedistribution,accountedfor94percentofthevariationinestimatesofparticles50mdiameter. The fraction of dust particles10 m diameter, as estimated using the Weibull, was not correlated to suspended PM10 concentration. However, the fraction of particles10m was correlated with properties of the sediment from which the airborne dust was derived. As clay content increased, the total amount of suspended dust increased and the fraction of suspendedparticles10minthedustclouddecreased.Analysesofvarianceshowednosignificantdifferences(P< 005)
Databáze: OpenAIRE
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