tailieunhanh - Monitoring Control and Effects of Air Pollution Part 7

Tham khảo tài liệu 'monitoring control and effects of air pollution part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Source Apportionment Applying Material Balance and Receptor Models in the MAMC 111 Figure 1 shows graphically the apportionment of considering the three sources mentioned above obtained with PCA for the different sites. In all cases the most important contributor to was the mobile sources with more than 45 of the total mass followed by secondary aerosols. Pedregal had the lowest contribution of soil. It is important to highlight that the results from Merced Pedregal and Xalostoc represent only the apportionment of PM measured in March 2003 that is part of the warm dry season in the MAMC whereas the measurements in Azcapotzalco were carried out during two years so Fig. 1. Source apportionment results from PCA at the four sites 7. UNMIX model The UNMIX model is a refined multivariate receptor model that uses a new transformation method based on the self-modeling curve resolution technique toderive meaningful factors. UNMIX incorporates user-specified non-negativity constraints and edge-finding algorithms to derive a physically reasonable apportionment of source contributions Henry 2001 Poirot et al. 2001 . The edges are constant ratios among chemical components that are detected in multi-dimensional space. The edges detected by this model are translated into source profile abundances. This model does not require a previous knowledge about emission sources although it is necessary a big number of measurements to estimate the different factors as well as the magnitude of their contributions Chen et al. 2002 Hellén et al. 2003 . UNMIX try to solve the problem of the chemical species mixture with the assumption that the data of each sample has a lineal combination of an unknown number of sources which contributes with an unknown mass concentration to the total mass. Another assumption is that all values are positive 0 . UNMIX uses the singular value decomposition SVD method to estimate the source number by reducing the dimensionality of data space m to

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