Elemental analysis of tree leaves by total reflection X-ray fluorescence: New approaches for air quality monitoring Fabjola Bilo a , Laura Borgese a, b, * , Rogerta Dalipi a , Annalisa Zacco a, b , Stefania Federici a , Matteo Masperi a , Paolo Leonesio a , Elza Bontempi a, b , Laura E. Depero a, b a Chemistry for Technologies Laboratory, INSTM and Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy b SMART Solutions s.r.l., Italy highlights graphical abstract  Elemental analysis of tree leaves is performed for air quality monitoring.  TXRF analysis is performed on leaves from 6 tree species and 11 urban parks.  Metals from anthropogenic sources contribute to differentiation of washed and unwashed samples.  The novel SMART STORE method for sample preparation allows direct TXRF analysis.  Advantages of the two sample prep- aration procedures are presented and discussed. article info Article history: Received 20 January 2017 Received in revised form 20 March 2017 Accepted 21 March 2017 Available online 22 March 2017 Handling Editor: R Ebinghaus Keywords: TXRF Tree leaves Heavy metals Air monitoring Bio-indicators SMART STORE abstract This work shows that total reflection X-ray fluorescence (TXRF) is a fast, easy and successful tool to determine the presence of potentially toxic elements in atmospheric aerosols precipitations on tree leaves. Leaves are collected in eleven parks of different geographical areas of the Brescia city, Northern Italy, for environmental monitoring purposes. Two sample preparation procedures are considered: mi- crowave acid digestion and the novel SMART STORE method for direct analysis. The latter consists in sandwiching a portion of the leaf between two organic foils, metals free, to save it from contamination and material loss. Mass composition of macro, micro and trace elements is calculated for digested samples, while relative elemental amount are obtained from direct analysis. Washed and unwashed leaves have a different composition in terms of trace elements. Differentiation occurs according to Fe, Pb and Cu contributions, considered as most representative of air depositions, and probably related to anthropogenic sources. Direct analysis is more representative of the composition of air precipitations. Advantages and drawbacks of the presented methods of sample preparation and TXRF analysis are discussed. Results demonstrate that TXRF allows to perform accurate and precise quantitative analysis of digested samples. In addition, direct analysis of leaves may be used as a fast and simple method for screening in the nanograms range. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Atmospheric pollution is one of the biggest problems of urban * Corresponding author. Chemistry for Technologies Laboratory, INSTM and Department of Mechanical and Industrial Engineering, University of Brescia, Bres- cia, Italy. E-mail address: laura.borgese@unibs.it (L. Borgese). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere http://dx.doi.org/10.1016/j.chemosphere.2017.03.090 0045-6535/© 2017 Elsevier Ltd. All rights reserved. Chemosphere 178 (2017) 504e512