44 research outputs found
Légköri szerves aeroszol másodlagos keletkezési mechanizmusának tanulmányozása = Study on secondary organic aerosol formation
Munkánk során bemutattuk, hogy a másodlagos aeroszol keletkezési mechanizmusában a multifázisú folyamatok nagy jelentőséggel bírnak. Aromás modellvegyületekből hidroxilgyökkel történő reakció során, gyökös mechanizmussal, a kiindulási anyagoknál nagyobb molekulatömegű alkotók keletkeznek. Feltételezhető, hogy az oligomerizációs reakcióban néhány aromás gyűrű illetve a reakció során keletkező termék kapcsolódik össze. Kutatásaink eredményei alapján valószínűsíthető, hogy hasonló átalakulási folyamatok játszódhatnak le légköri aeroszolban is, melyek a légköri aeroszol kémiai tulajdonságait is befolyásolják. A légköri aeroszol humuszszerű anyagainak csoportjába tartozó szerves szulfát vegyületek keletkezési mechanizmusát tekintve feltételezhető, hogy azok a fotokémiai reakciók során keletkező anyagok kémiai reakcióval történő átalakulása után már meglevő aeroszol részecskék felületén képződnek. Ködkamra kísérletek során gyűjtött minták elemzésével kapott eredmények alapján feltételezhető, hogy humuszszerű anyagok másodlagos folyamatokban a növények által emittált illékony szerves anyagokból is keletkezhetnek. | It has been shown that multiphase processes represent an important yet previously overlooked formation mechanism of secondary organic aerosol. In the reaction of OH radicals with aromatic model compounds in the aqueous phase higher molecular weight compounds were found to form by radical reaction mechanisms. It was assumed that during the oligomerisation reactions a few aromatic ring and/or the reaction products form condensed structures. Based on our studies it can be hypothesized that similar reaction mechanisms might take place in atmospheric aerosols altering their chemical properties. It was shown that organosulphates, which are recently discovered and important SOA components and possibly part of atmospheric HULIS may form in surface reactions on pre-existing aerosols in chemical reactions with compounds formed in photochemical processes. Our results obtained from the analysis of samples collected from smog chamber experiments showed that humic-like substances might also be generated in secondary processes from volatile organic compounds emitted by the vegetation
Brown carbon absorption in the red and near-infrared spectral region
Black carbon (BC) aerosols have often been assumed
to be the only light-absorbing carbonaceous particles
in the red and near-infrared spectral regions of solar radiation
in the atmosphere. Here we report that tar balls (a specific
type of organic aerosol particles from biomass burning)
do absorb red and near-infrared radiation significantly. Tar
balls were produced in a laboratory experiment, and their
chemical and optical properties were measured. The absorption
of these particles in the range between 470 and 950 nm
was measured with an aethalometer, which is widely used to
measure atmospheric aerosol absorption.We find that the absorption
coefficient of tar balls at 880 nm is more than 10%
of that at 470 nm. The considerable absorption of red and
infrared light by tar balls also follows from their relatively
low absorption Ångström coefficient (and significant mass
absorption coefficient) in the spectral range between 470 and
950 nm. Our results support the previous finding that tar balls
may play an important role in global warming. Due to the
non-negligible absorption of tar balls in the near-infrared region,
the absorption measured in the field at near-infrared
wavelengths cannot solely be due to soot particles
Light absorption properties of laboratory-generated tar ball particles
Tar balls (TBs) are a specific particle type that is
abundant in the global troposphere, in particular in biomass
smoke plumes. These particles belong to the family of atmospheric
brown carbon (BrC), which can absorb light in the
visible range of the solar spectrum. Albeit TBs are typically
present as individual particles in biomass smoke plumes,
their absorption properties have been only indirectly inferred
from field observations or calculations based on their electron
energy-loss spectra. This is because in biomass smoke
TBs coexist with various other particle types (e.g., organic
particles with inorganic inclusions and soot, the latter emitted
mainly during flaming conditions) from which they cannot
be physically separated; thus, a direct experimental determination
of their absorption properties is not feasible. Very
recently we have demonstrated that TBs can be generated
in the laboratory from droplets of wood tar that resemble
atmospheric TBs in all of their observed properties. As a
follow-up study, we have installed on-line instruments to
our laboratory set-up, which generate pure TB particles to
measure the absorption and scattering, as well as the size
distribution of the particles. In addition, samples were collected
for transmission electron microscopy (TEM) and total
carbon (TC) analysis. The effects of experimental parameters
were also studied. The mass absorption coefficients of
the laboratory-generated TBs were found to be in the range
of 0.8–3.0m2
Atmospheric tar balls: aged primary droplets from biomass burning?
Atmospheric tar balls are particles of special morphology and composition
that are fairly abundant in the plumes of biomass smoke. These particles
form a specific subset of brown carbon (BrC) which has been shown to play a
significant role in atmospheric shortwave absorption and, by extension, climate
forcing. Here we suggest that tar balls are produced by the direct emission
of liquid tar droplets followed by heat transformation upon biomass burning.
For the first time in atmospheric chemistry we generated tar-ball particles
from liquid tar obtained previously by dry distillation of wood in an
all-glass apparatus in the laboratory with the total exclusion of flame
processes. The particles were perfectly spherical with a mean optical
diameter of 300 nm, refractory, externally mixed, and homogeneous in the
contrast of the transmission electron microscopy (TEM) images.
They lacked any graphene-like microstructure and
exhibited a mean carbon-to-oxygen ratio of 10. All of the observed
characteristics of laboratory-generated particles were very similar to those
reported for atmospheric tar-ball particles in the literature, strongly
supporting our hypothesis regarding the formation mechanism of atmospheric
tar-ball particles
Emission factors for PM10 and PAHs from illegal burning of different types of municipal waste in households
It is a common practice in the developing countries and in some regions of Europe that solid wastes
generated in the households (e.g. plastic beverage packaging and other plastic wastes, textile wastes, fibreboards,
furniture, tyres, and coloured paper waste) are burned in wood- or coal-fired stoves during the winter months. In
Europe, the types and volume of municipal waste burned in households is virtually unknown because these
activities are illegal and not recorded, with the exception of a few media reports or court cases. Even though particulate emissions from illegal waste burning pose an unprecedented hazard to human health due to the
combination of excessive emission factors (EFs) and uncontrolled chemical composition, there is scarce
information on the specific emission factors for PM10 and polycyclic aromatic hydrocarbons (PAHs) in the
scientific literature. In this work, controlled combustion tests were performed with 12 different types of
municipal solid waste and particulate emissions were measured and collected for chemical analysis. Absolute
emission factors for PM10 and PAHs as well as the benzo(a)pyrene toxicity equivalent of the latter are reported for the first time for the indoor combustion of 12 common types of municipal solid waste that are frequently burned in households worldwide
Sampling and characterization of resuspended and respirable road dust
AbstractUrban air quality is severely affected by traffic related particulate matter, including direct emissions from exhaust, brake pad, tire wear and road dust resuspended by vehicular motions. Deposited road dust can also be resuspended by wind force or other anthropogenic activities, and overall it may contribute up to 30% to urban PM10. A mobile resuspended road dust PM10 sampler was developed and constructed which simulates the effects of traffic or gusting winds on road surfaces and collects resuspended PM1−10 samples in a cyclone separator and PM1 samples on filters. The sampler was tested by collecting resuspended road dust at kerbside locations in Veszprém, Hungary. The collected PM1 and PM1−10 fractions were analysed by various analytical methods to show the potential of size-selective on-line sample collection combined with the chemical characterization of resuspended road dust. The main constituents of the resuspended road dust were crustal elements, and it was also possible to determine the mineral phase composition of PM1−10 dust which is generally not feasible from samples collected on filter substrate. The application of the sampling and analysis methods may facilitate the evaluation of resuspended road dust sources in cities as well as help constrain a better source apportionment of urban PM10