DOI: 10.17632/zddh4r2bbm.1
title: Data for: Levels, spatial distribution, risk assessment and sources of environmental contamination vectored by road dust in a Caribbean mid-size city revealed by chemical and C and N stable isotope compositions

description: Road dust sampling
A total of 31 road dust samples were collected from the main paved roads of Cienfuegos city by sweeping an area of about 1.0mx0.5m from pavement edges using a plastic dustpan and brushes. The sampling was conducted on July 20, 2016 (wet season) under sunny and windless conditions and with no rain having occurred during the three days prior to sampling. All samples were stored and labeled in self-sealed polyethylene bags and immediately brought back to the laboratory for preparation and analysis. In the laboratory, samples were dried at 45ºC, passed through a 50 µm sieve and stored in polyethylene bags until further analysis.

Chemical analysis
Concentrations of 49 major and trace elements were conducted on the road dust samples using inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7500a). An aliquot (50 mg) of each road dust sample was digested with HF, H2O2, HNO3 and HCl (3:3:4:1 mL) in a closed microwave digestion system (CEM Co., Mars X press). A multi-element solution (Li, Sc, Y, In, Bi) was added to the sample and indium was used as the internal standard for further determination by ICP-MS. Mercury (Hg) concentrations were determined by atomic absorption spectrometry (AAS) using a Mercury Analyzer (MA-2000 Series, Nippon) on a second 50 mg road dust sample.
Quality assurance of the analytical results was controlled by repeated analysis of the certified reference materials (CRMs) CTA-FFA1 and 0217-CM-73007 for major and trace elements and Hg, respectively. In addition, several samples (from sites 01, 05, 12 and 16) were analyzed in duplicate, yielding an average RSD below 8%.

Total carbon, total nitrogen and stable C and N isotopes analysis
Concentrations of the total carbon (TC) and total nitrogen (TN) and their corresponding stable isotope compositions (δ13C and δ15N) were determined using an Elemental Analyzer (Vario MICRO Cube, Elementar, Hanau, Germany) coupled to an Isotope Ratio Mass Spectrometer (IsoPrime 100, Cheadle, UK) operating in continuous flow mode. Inorganic carbon (carbonate) was not removed prior to the isotope analysis. For the analysis, about 4 mg of road dust were packed into a tin capsule and introduced into the EA autosampler. Isotope compositions are expressed as δ13C and δ15N values, which represent the relative difference expressed in per mil ‰ between the isotope ratio of the sample and that of a standard (Pee Dee Belemnite (PDB) for carbon and atmospheric N2 for nitrogen).

The analytical quality control was performed by routinely analysis of interspersed international carbon and nitrogen isotope standards (IAEA, Vienna, Austria) and the interlaboratory-calibrated algae reference material 1452 B (University of Barcelona). We also ran several samples in duplicate. The obtained reproducibility was &lt;0.2‰ for C and &lt;0.3‰ for N isotope compositions. Similarly, analytical uncertainties for TC and TN concentrations were within 2 and 3% of the reported values, respectively.