No abstract

Studies including multiple isotope systems in aerosols promises unparalleled insights into sources and pathways of metals in the atmosphere. However, such studies remain rare because of the challenges associated with small sample sizes and low analyte masses of the target elements. Here, we present the first study combining accurate and precise determination of Pb, Cu and Zn isotopic ratios in aerosols and anthropogenic materials collected in São Paulo, Brazil. We use a sequential ion chromatography procedure with two different resins for the separation and purification of the analytes. Multi collector mass spectrometry is used for the accurate and precise determination of the isotope ratios. Long term analytical reproducibilities are ±0.035 for 206Pb/204Pb, ± 0.13‰ for δ65CuNIST and ±0.1‰ for δ66ZnJMC (±2σ). Accuracy is assessed using certified reference materials (CRM NIST 2783 aerossol, BRP-1 and others). We analyzed 57 source samples (road dust, tires, cement, road tunnel aerosol) and 113 aerosol samples collected between 2013 and 2015. The results for São Paulo are critically compared with previously published data from studies conducted in São Paulo, London and Barcelona. The key findings are: 1. The isotope signatures for Zn in tires (δ66ZnJMC = 0.16 ± 0.14, 2σ, n = 9) and road dust (δ66ZnJMC = 0.17 ± 0.19, 2σ, n = 13) are similar in São Paulo and London suggesting that this isotope system can be used as element specific tracers for non-exhaust traffic. 2. 206Pb/207Pb vs δ66ZnJMC and δ66ZnJMC vs δ65CuNIST multi-isotopic diagrams successfully separate wear off from cars including tires and brakes, car exhaust, industrial emissions and cement sources and improves the discrimination of air pollutant sources. 3. The source identification based on isotope ratios agrees source apportionement based on emissions inventory from these cities. 4. We present Pb, Cu and Zn isotopic data for the first time for the CRM NIST 2783 and BRP-1. These new data will enable future intercalibration and quality controls in other laboratories. Our study confirms that stable isotope ratio analysis have a great potential for element specific source characterization (e.g., separating non combustion traffic sources from combustion sources) for Cu, Zn and Pb. Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

Recent work has shown that variations in zinc (Zn) isotope ratios enable us to identify contamination sources in the terrestrial environment and uptake processes in higher plants. Here in this study, we demonstrate that this also holds true for mangrove forests, which play an important role in the biogeochemical cycling of metals in tropical coastal ecosystems and that are seriously threatened by anthropogenic pollution. To this end, we determined zinc concentration and isotope composition (expressed using the δ66Zn notation relative to the JMC 3-0749-L standard) in sediments and tree leaves collected from a mangrove close to Rio de Janeiro in Brazil. The δ66ZnJMC values of sediments vary between +0.36 and + 0.84‰ and fall on a mixing line between detrital terrestrial sources (characterized with δ66ZnJMC = +0.28 ± 0.12‰, 2σ) and metallurgical ore sources (δ66ZnJMC = +0.86‰ ±0.15‰, 2σ). Leaves of Laguncularia racemose, in contrast, showed δ66ZnJMC values ranging between +0.08 and + 0.23‰, suggesting that processes including uptake, translocation and bioavailability in the rhizosphere control the isotope composition of zinc in the mangrove plant. Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

have been numerous studies on the direct and indirect climatic effects of aerosols [Takemura et al., 2002;Zhang, 2008; Zhang 51 et al., 2010;Forkel et al., 2012; Scott et al., 2014; Cai et al., 2016;Yahya et al., 2017]. Most of studies of such effects in South 52America have focused on the Amazon rainforest, as smoke generated from biomass burning in the region can spread over 53 significant portions of the continent, having a considerable effect on direct and indirect radiative forcing [Bevan et al., 2009; 54 Artaxo et al., 2013; Moreira et al., 2017], as well as on human health [Alves et al., 2015; Alves et al., 2017; et al. [1994a; 1994b]. Nucleation processes are based on mathematical formulations described in Kulmala et al. 112[1998]; condensation processes are based on Binkowski and Shankar [1995] 167Performance statistics were calculated for the period from 19 August to 3 September (the first two days of each simulation 168 were considered spin-up time and were therefore discarded). In addition, spatial distributions of absolute and relative 169 differences between BBE and BASE and between 3BBE and BASE were employed to quantify and characterise the changes in 170 aerosol properties due to the inclusion of fire emissions. In this case, the differences are averaged over a five-day episode from 171 22 August to 26 August, as in this period prevailed meteorological conditions in terms of the transport of air pollutants from 172 fire regions. al., 2015]. To scale the top-down and bottom-up emissions into the 25 km and 5 km modelling domains, mass-conserving 212 emissions pre-processors anthro_emiss [Barth et al., 2015] and AAS4WRF [Vara-Vela et al., 2016;Vara-Vela et al., 2017] 213 were employed, respectively. Supplement Fig. S1 shows spatial distributions of CO emission rates in both domains. Table S1. Information on precipitation and AOD derived from satellite data were 306 considered in addition to in situ and lidar measurements throughout the evaluation of numerical simulations. Table 3 307 summarises the observational data sets used for model evaluation.308

Abstract. Atmospheric aerosol is the primary source of cloud condensation nuclei (CCN). The microphysics and chemical composition of aerosols can affect cloud development and the precipitation process. Among studies conducted in Latin America, only a handful have reported the impact of urban aerosol on CCN activation parameters such as activation ratio (AR) and activation diameter (Dact). With over 20 million inhabitants, the Metropolitan Area of São Paulo (MASP) is the largest megacity in South America. To our knowledge, this is the first study to assess the impact that remote sources and new particle formation (NPF) events have on CCN activation properties in a South American megacity. The measurements were conducted in the MASP between August and September 2014. We measured the CCN within the 0.2–1.0 % range of supersaturation, together with particle number concentration (PNC) and particle number distribution (PND), as well as trace-element concentrations and black carbon (BC). NPF events were identified on 35 % of the sampling days. Combining multivariate analysis in the form of positive matrix factorization (PMF) with an aerosol profile from lidar and HYSPLIT model analyses allowed us to identify the main contribution of vehicular traffic on all days and sea salt and biomass burning from remote regions on 28 and 21 % of the sampling days, respectively. The AR and Dact parameters showed distinct patterns for daytime with intense vehicular traffic and nighttime periods. For example, CCN activation was lower during the daytime than during the nighttime periods, a pattern that was found to be associated mainly with local road-traffic emissions. A decrease in CCN activation was observed on the NPF event days, mainly due to high concentrations of particles with smaller diameters. We also found that aerosols from sea salt, industrial emissions, and biomass burning had minor effects on Dact. For example, nights with biomass burning and vehicular emissions showed slightly lower CCN activation properties than sea-salt, industrial and non-event nights. Our results show that particulate matter from local vehicular emissions during the daytime has a greater effect on CCN activation parameters than that from remote sources.

No abstract

Urban air pollution is a matter of concern due to its health hazards and the continuous population growth exposed to it at different urban areas worldwide. Nowadays, more than 55% of the world population live in urban areas. One of the main challenges to guide pollution control policies is related to pollutant source assessment. In this line, U.S. Environmental Protection Agency's Positive Matrix Factorization (EPA-PMF) has been extensively employed worldwide as a reference model for quantification of source contributions. However, EPA-PMF presents issues associated to source identification and discrimination due to the collinearities among the source tracers. Multi-Isotopic Fingerprints (MIF) have demonstrated good resolution for source discrimination, since urban sources are characterized by specific isotopic signatures. Source quantification based on total aerosol mass is the main limitation of MIF. This study reports strategies for PMF and MIF combination to improve source identification/discrimination and its quantification in urban areas. We have three main findings: (1) cross-validation of PMF source identification based on Pb and Zn isotopic fingerprints, (2) source apportionment in the MIF model for total PM mass, and (3) new insights into potential Zn isotopic signatures of biomass burning and secondary aerosol. We support future studies on the improvement of isotopic fingerprints database of sources based on diverse elements or compounds to boost advances of MIF model applications in atmospheric sciences.

The aim of this study is to discuss the concentration distribution, composition and possible sources of trace metals and 13 PAHs in topsoils of the University campus, in the city of São Paulo, the largest city of South America. Mineralogy and granulometry of topsoils (0-10 cm) samples, were determined and As,