Development of nanometer aerosol measurement technology
Date
2011-07-19
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Abstract
Aerosooliosakeste teket nukleatsiooni teel ja nende järgnevat kasvu on jälgitud kõikjal maailmas. Tekkinud osakesed on algselt nanomeetri suurused, kuid võimelised kasvama ja seejärel osalema pilvetekkes, muutma kiirgusbilanssi ja lõpuks mõjutama Maa kliimat. Samuti võivad nano-osakesed mõjuda inimeste tervisele.
Aerosooliosakeste tekke uurimise vastu on suur huvi, kuid nanomeetrisuuruste osakeste mõõtmine atmosfääris on keerukas.
Osakeste tekke uurimiseks sobib hästi nanomeeter-aerosooli ja õhuioonide spektromeeter (NAIS, välja töötatud AS Airel, Eesti). Seade kasutab elektrilise aerosooli spektromeetria põhimõtet, et mõõta nii elektriliselt laetud osakeste (aero-ioonide) või ka laadimata osakeste suurusspektreid. Spektromeeter on suuteline töötama kaua hooldusvabalt väga erinevates keskkondades -- nii reostunud kesklinnast, kui ka kaugetes metsades. Seade on väljatöötatud aeroioonide spektromeetri (AIS) baasil.
NAIS tööpõhimõte seisneb aersooli laadimises unipolaarses koroona ioonide väljas ja paralleelses elektrilises liikuvusanalüüsis. NAIS-il on kaks paljukanalilist elektrilist liikuvusanalüsaatorit, üks positiivsete ja teine negatiivsete laengute detekteerimiseks. Aerosool klassifitseeritakse ja mõõdetakse mõlemas analüsaatoris samaaegselt, kummaski 21 elektromeetriga. Seade mõõdab ioonide (laetud osakeste, klasterioonide) liikuvusjaotust vahemikus 3.2 – 0.0013 cm/V/s ja aerosooliosakeste suurusjaotust vahemikus 2.0 – 40 nm. Hetkel on üle maailma käigus üle kümne NAIS mõõteseadme.
Väitekiri põhineb NAIS spektromeeter arendusel. Kirjeldatakse seadme matemaatilisi ja tehnilisi põhimõtteid. Tutvustatakse uut edasiarendatud NAIS mudelit – nn. “Lendav NAIS”', mis on suuteline sooritama mõõtmisi lennukilt laias kõrgustevahemikus. Uue seadme parandatud töökindlus, paindlikkus ja mõõtmiskiirus tulevad kasuks ka tavapärastel “maistel” atmosfäärimõõtmistel.
Formation of aerosol by the nucleation of particles and their subsequent growth has been observed in the atmosphere almost everywhere around the world. The formed particles, initially of nanometer size, may grow further, participate in cloud formation, influence the radiation balance and ultimately climate. On local scales, these particles can affect atmospheric visibility and human health. There is a growing interest in studying new particle formation. However, it is difficult to measure aerosol particles in the size range of a few nanometers under atmospheric conditions. An instrument that is well suited for such measurements is the Nanometer aerosol and Air Ion Spectrometer (NAIS, developed by Airel Ltd., Estonia) which uses the principle of electrical aerosol spectrometry to measure the size distributions of naturally charged particles (ions) of both polarities as well as uncharged particles. The NAIS has been specifically designed for atmospheric nanometer aerosol monitoring. It can operate for long periods in a wide range of ambient conditions from polluted downtown to remote forest. It is based on the Air Ion Spectrometer (AIS). The NAIS uses unipolar corona charging and parallel electrical mobility analysis. The instrument contains two identical multichannel electrical mobility analyzer columns: one for positive, one for negative ions. The aerosol is synchronously mobility-classified in the mobility analyzers and measured with an array of 21 electrometers per column. The NAIS measures the distribution of ions (charged particles and cluster ions) in the electric mobility range from 3.2 to 0.0013 cm/V/s and the distribution of aerosol particles in the size range from 2.0 to 40 nm. There are more than ten NAIS instruments in use today around the world. The thesis focuses on the development of the NAIS. The mathematical and technical principles of the instrument are presented. An updated version of the instrument is introduced – the so called “Airborne NAIS”, which is capable of operating on board an aircraft at varying altitudes. The better reliability, adaptability and measurement speed improve regular ground based measurements as well.
Formation of aerosol by the nucleation of particles and their subsequent growth has been observed in the atmosphere almost everywhere around the world. The formed particles, initially of nanometer size, may grow further, participate in cloud formation, influence the radiation balance and ultimately climate. On local scales, these particles can affect atmospheric visibility and human health. There is a growing interest in studying new particle formation. However, it is difficult to measure aerosol particles in the size range of a few nanometers under atmospheric conditions. An instrument that is well suited for such measurements is the Nanometer aerosol and Air Ion Spectrometer (NAIS, developed by Airel Ltd., Estonia) which uses the principle of electrical aerosol spectrometry to measure the size distributions of naturally charged particles (ions) of both polarities as well as uncharged particles. The NAIS has been specifically designed for atmospheric nanometer aerosol monitoring. It can operate for long periods in a wide range of ambient conditions from polluted downtown to remote forest. It is based on the Air Ion Spectrometer (AIS). The NAIS uses unipolar corona charging and parallel electrical mobility analysis. The instrument contains two identical multichannel electrical mobility analyzer columns: one for positive, one for negative ions. The aerosol is synchronously mobility-classified in the mobility analyzers and measured with an array of 21 electrometers per column. The NAIS measures the distribution of ions (charged particles and cluster ions) in the electric mobility range from 3.2 to 0.0013 cm/V/s and the distribution of aerosol particles in the size range from 2.0 to 40 nm. There are more than ten NAIS instruments in use today around the world. The thesis focuses on the development of the NAIS. The mathematical and technical principles of the instrument are presented. An updated version of the instrument is introduced – the so called “Airborne NAIS”, which is capable of operating on board an aircraft at varying altitudes. The better reliability, adaptability and measurement speed improve regular ground based measurements as well.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
atmosfäärifüüsika, aerosoolid, nanoosakesed, aeroioonid, spektomeetrid, atmospheric physics, aerosols, nanoparticles, air ions, spectometres