Data for: Pollution monitoring in two urban areas of Cuba by using Tillandsia recurvata (L.) L. and top soil samples: spatial distribution and sources
Samples of T. recurvata were collected in 5 and 4 sites of Santa Clara and Cienfuegos, respectively. Four sampling campaigns were carried out between 2015 and 2016: in Santa Clara, samples were collected in November 2015 and March, June and September 2016; while in Cienfuegos sampling campaigns took place in June and December 2015, and June and September 2016. The monitoring sites at both cities were located in roads or highways with high level of vehicular traffic (sites 1 and 3 in Cienfuegos and 2, 3 and 4 in Santa Clara) and in parks surrounded by busy roads (sites 2 and 4 in Cienfuegos and 1 and 5 in Santa Clara). At each sampling site, composite samples, made up of 3 to 6 plants from the same tree or nearby trees, were taken at a height of 2 m or higher in order to minimize resuspension of soils and particles from roads. Top soils samples (0-5 cm of roadside or parks soils) were collected in the same sampling places at the same time. Additionally, three composite samples of T. recurvata were collected in the Botanic Garden of Cienfuegos (site 5 in Figure 1) in September 2016 and considered as the control site (no soil samples were taken at this site). All samples were stored and labeled in self-sealed polyethylene bags and immediately taken to the laboratory for preparation. Unwashed samples of T. recurvata and top soils were oven-dried at 45˚C to constant weight, grounded and passed through a 250 µm sieve. The fraction <250 µm was stored in polyethylene bags until further analysis. Concentrations of 46 major and trace elements were determined using inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7500a). About 0.25 g (dry weight) of epiphytic plant and top soils samples were digested in a closed microwave digestion system (CEM Co., Mars X press) using 9 mL of concentrated nitric acid and 12 ml aqua regia, respectively. A multi-element solution (Li, Sc, Y, In, Bi) was added to each sample and used as internal standards for further analysis by ICP-MS. Mercury concentrations were determined by atomic absorption spectrometry using a Mercury Analyzer (MA-2000 Series, Nippon) on 50 mg of sample. Soil samples from the 4th sampling campaign were not measured by ICP-MS due to technical issues. For the quality control of the analytical procedure, a pine needle sample from the 15th ICP Forests ring test and the interlaboratory reference material M2-Pleurozium Schreberi were used for T. recurvata. For top soils, the certified reference materials Soil 0217-CM-73007 and 0217-CM-7003 (Silty Clay Loam) were used. In both cases, these QC samples, one blank (only reagents) and one duplicated sample were measured every ten samples. Elemental recovery from reference materials were in the range 76-101% with a relative standard deviation (RSD) <7% for epiphytic plants and 74-115% with RSD<9% for top soils. Here, the heavier lanthanoids (Dy to Lu) showed lower recoveries in the range 47-63% (RSD<6%). The RSD from duplicated samples were <10%.