Biomonitoring of heavy metals in tree vegetation in the city of Saltillo

Abstract

Heavy metal contamination is a serious problem worldwide and in some regions of Mexico. In cities, this is mainly due to residues or waste from industry and vehicle flow. This study focuses on determining the concentration of heavy metals (Cd, Cr, Pb and V) in tree species leaves (Pinus halepensis Mill., Cupressus sempervirens L. and Prosopis spp.). These species were selected with the purpose of being used as environmental quality bioindicators in the city of Saltillo, Coahuila, Mexico. 15 sampling points were established, of which 13 points were randomly distributed in the city of Saltillo and two points outside the urban area. Sampling was carried out in July 2019 (summer period). The heavy metal content was determined by the inductively coupled plasma optical emission spectroscopy (ICP-OES) technique. Interactions between species-site factors with respect to heavy metal concentrations were tested, which were determined by the averages obtained between the samples and their duplicates. It is highlighted that the species factor C. sempervirens resulted in the highest concentration of heavy metals in Cd, Pb and V, as well as P. halepensis in Cr. Points 3, 4, 12 and 15 resulted in the highest concentrations of the metals analysed, these points are located in the southeast and central areas of the city of Saltillo. The use of tree species as heavy metal bioindicators in the city of Saltillo can be a viable tool for monitoring environmental quality.