Aerossóis atmosféricos na Amazônia: composição orgânica e inorgânica em regiões com diferentes usos do solo
This work showed the complexity of the organic and inorganic composition of aerosol from Amazônia e its interactions with biogenic processes in the forest. We investigated the sources and processes that regulate the organic and inorganic components of aerosol particles from Amazônia based on long t...
| Autor principal: | Arana, Andréa Araújo |
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| Grau: | Tese |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/12978 http://lattes.cnpq.br/4909060809132531 |
| Resumo: |
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This work showed the complexity of the organic and inorganic composition of aerosol from
Amazônia e its interactions with biogenic processes in the forest. We investigated the sources and processes that regulate the organic and inorganic components of aerosol particles from Amazônia based on long term continuous measurements in two regions: one perturbed by
land use change, in Porto Velho/RO, and one of pristine tropical rainforest, Rebio
Cuieiras/AM. For the first time, the elemental concentration of the aerosol from Amazônia
was obtained using energy dispersive x-ray fluorescence – EDRF. A careful calibration and optimization of the EDXRF Epsilon 5, PANalytical, was performed. This task involved the
production of calibration standards for element P, besides the use of commercially available standards from MicroMatter. A new methodology was developed to calculate the detection limit for each element based on a non-linear fit of the standard deviation for different masses, and was compared to the usual method using the background noise in blank filter
measurements. Both methods gave similar detection limits, with higher values around 45 ng cm-2 (Na, Mg e Cd), most values below 10 ng cm-2, and some very low values as 3 ng cm-2 (P, S, Cl, K, Ca, Cr, Fe e Cu). A detailed and extensive comparison with other EDXRF spectrometers, one from Antwerp University and another from CETESB, and other analytical
methods, PIXE and Ion Chromatography, was performed. The comparison between PIXE
and EDXRF showed statistically significant regressions for most elements, as well as the
comparison with the other EDXRF, thus indicating that the calibration and fine-tuning of the LFA EDXRF were appropriate. The comparison with the Ion Chromatography from PUC-Rio
was used to quantify the particle self-attenuation corrections necessary for light elements.
About the seasonal variation of aerosol mass concentration at Rebio Cuieiras, the average
concentration was very low, 9.5 ± 4.7 μg m-3 (wet season) and 13.4 ± 4.9 μg m-3 (dry season),
with a very clear seasonal cycle. The equivalent BC showed a stronger seasonality with high concentrations in the fine mode, 0.57 ± 0.38 μg m-3, during the dry season, and very low, 0.05 ± 0.02 μg m-3, during the wet season. In Porto Velho, average PM10 was 8.8 ± 4.2 μg m-3 (wet) and 45 ± 42 μg m-3 (dry), but with mean values reaching as high as 200 μg m-3 as during the dry season of 2010, when EBC reached values of 3.6 ± 3.6 μg m-3. During the wet season,
the EBC average concentration was 0.5 ± 0.4 μg m-3. That means that, even in the absence of large scale biomass burning, land use change and local pollution interfere on the concentration of aerosol in anthropogenic impacted Amazon regions, as observed by Artaxo et al. (2013). For measuring the carbonaceous aerosols, the EUSAAR_2 was chosen after an
comparison exercise. For validating the measurements, a comparison with the University of Ghent, Belgium, was performed and showed that our calibration with sucrose, the
determination of the transit time and the data processing is correct. The average concentration of OC at Rebio Cuieiras was 6.3 ± 3.1 μg m-3 (dry) e 1.8 ± 0.7
μg m-3 (wet), and for EC it was
0.6 ± 0.3 μg m-3 (dry) and 0.18 ± 0.08 μg m-3 (wet). In general, our results indicate that this area is still pristine but with some impact of long range biomass burning transport during the dry season. At Porto Velho, the average OC concentration was 12 ± 5
μg m-3 (dry) and 5.0 ± 0.5 μg m-3 (wet), and for EC was 0.9 ± 0.5 μg m-3 (dry) e de 0.5 ± 0.3
μg m-3 (wet). The presence of anomalous brown carbon absorption was analyzed but it was not possible to quantify its presence in the atmospheric aerosol in the Amazon region. The increase in mean atmospheric concentrations of OC and EC from the wet to the dry season was studied for each volatility level. Results showed a higher increase of the OC2, OC3, EC2 and EC3
(intermediate volatility) at Rebio Cuieiras, while at Porto Velho there was a higher increase of OC1 and EC1, as it is more subject to fresh biomass burning. Using positive matrix
factorization and absolute principal factor analysis, a source apportionment of particulate
matter was performed. The novelty in this study was the inclusion of the organic and
inorganic components (and not only the elemental composition). The PMF analysis did not
show self-consistent results and, indeed, there is a scientific debate nowadays on |