Chemical Composition of Quasi-ultrafine Particles and their Sources in Elderly Residences of São Paulo Megacity

ABSTRACT Atmospheric quasi-ultrafine particles (qUFP; PM<0.25) can cause harmful effects to human health, mainly to elderly people. Although not always considered, these effects can be mostly due to its chemical composition. The scope of this work is (i) to quantify the abundance of ions and trace elements in qUFP in elderly residences, (ii) to identify the sources of these qUFP and (iii) to estimate the respiratory deposition doses (RDD) of qUFP and black carbon (rBC), which is an important component of qUFP, to various parts of the respiratory tract. In order to evaluate the qUFP chemical composition in elderly residences in the Metropolitan Area of Sao Paulo (MASP), we collected qUFP by using a Personal Cascade Impactor Sampler (PCIS). We analysed ions by chromatography and trace elements by Energy Dispersive X-Ray Fluorescence. We identified the sources of qUFP by applying Positive Matrix Factorization. We calculated the RDD through an equation, which use the tidal volume of lung, the typical breath frequency, the deposition fraction and the mass concentration of different size fractions of a PM. We collected 60 samples from 59 residences between May 2014 and July 2015. The major of ions concentrations in qUFP were found to be SO42- and NH4+, and the major trace elements were Si and Fe. Some residences have a high concentration of the toxic heavy metals Cu, Ni, Pb and Cr. We found six dominant sources of the indoor qUFP: vehicular emission (57%), secondary inorganic aerosol (21%), soil and construction (7%), wall painting (7%), cooking (5%) and industry (3%). The maximum RDD of qUFP and rBC are in the tracheobronchial part. Our results show that vehicular emissions dominate the indoor qUFP concentrations and uptake in elderly residences in the MASP.