Science | November 5th, 2018
In Search of Fingerprints for Atmospheric Pollution

Research determines markers to identify those responsible for the emission of iron-rich particles in cities

The contamination of the atmosphere by gases and solid particles affects not only human health in urban centers but also the ecosystem. The management of air quality depends on several actions including the establishment of quality standards, the regulation of the release of pollutants, and the monitoring of air quality in a given region.

Programs for air quality monitoring can point out levels of pollutants in the atmosphere and assess their compliance with standards set by legislation. However, they are not able to identify the individual contribution of each source responsible for the emission.

One of the tools used to control and reduce air pollution are mathematical models called source apportionment models. They allow to estimate, from the physical and chemical characteristics of the pollutants, the contribution coming from several sources. This is essential information in the identification and accountability of polluting sources by control and inspection agencies.

Despite this, some limitations of these models hinder their unambiguous application. This is because different sources may have very similar chemical profiles or, alternatively, different pollutant sources may be very close together. Thus, the transport of pollutants by the winds results in almost simultaneous deposition at a given location.

This effect, called collinearity of the sources, can decrease the sensitivity of the mathematical models, causing an incorrect evaluation of each contribution. One way around this problem is to stablish chemical markers that assign unique characteristics to sources.

Thus, Elson Silva Galvão and collaborators investigated [1] the particulate matter present in the atmosphere of the Greater Vitória Region, Brazil, to identify specific markers that could relate each component of the particulate material to specific sources.

Among the analyses, the researchers used the XRD1 beamline of the Brazilian Synchrotron Light Laboratory (LNLS). According to the group, the facilities were fundamental for the success of the research, since the X-ray diffraction technique allowed the identification of such markers. The study resulted in an unprecedented approach in the chemical characterization of atmospheric particles and in the identification of markers that can link these particles to their emission sources.

The results suggest that different chemical states of iron are related to very specific industrial processes associated to the steel industry. Other markers presented distinct signatures which allowed distinguishing vehicular and industrial sources, thus minimizing a generic interpretation of the emission sources.

According to the researchers, this work shows its importance not only for application in studies of air quality, but also the study of sediments and materials.

Figure: Industrial (Alpha-hematite and metallic iron) and vehicular (BaTiO3) markers in a sample of Total Suspended Particles (TSP) collected from the atmosphere of the Greater Vitória Region, Brazil.

Source: [1] Elson Silva Galvão, Jane Meri Santos, Ana Teresa Lima, Neyval Costa Reis Jr., Richard Michael Stuetz, Marcos Tadeu D’Azeredo Orlando, Resonant Synchrotron X-ray Diffraction determines markers for iron-rich atmospheric particulate matter in urban region. Chemosphere 212 (2018) 418-428. DOI: 10.1016/j.chemosphere.2018.08.111

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