Color as a New Proxy Technique for the Identification of Road Dust Samples Contaminated with Potentially Toxic Elements: The Case of Mérida, Yucatán, México

Abstract

The design of proxy techniques is an innovative tool to monitor the potentially toxic elements of pollution in road dust. This study evaluated the use of road dust color as a proxy methodology to identify samples contaminated with presumably contaminating elements. FRX determined the concentrations of Fe, Ti, Rb, Sr, Y, Cu, Zn, and Pb in eighty-five road dust samples. The appliance of the RGB system and the Munsell color cards identified five color groups of road dust samples. The discriminant analysis validated these groups by colorimetric indices and presumably contaminating elements. The “very dark gray” color of road dust contains the highest concentrations of Pb, Cu, Zn, and Y. The redness and saturation rates showed high correlations with presumably contaminating elements in “dark gray” and “very dark gray” color samples. The color of road dust, as a proxy technique, allows identifying samples contaminated with presumably contaminating elements.

Heavy Metal Contamination (Cu, Pb, Zn, Fe, and Mn) in Urban Dust and its Possible Ecological and Human Health Risk in Mexican Cities

“…Only in the case of Morelia inductively coupled plasma optical emission spectroscopy (ICP-OES) was used. The details of the methodology can be consulted in previous studies: CDMX (Delgado et al, 2019), Ensenada (Cortés et al, 2015), SLP (Aguilera et al, 2019), Mérida (Aguilar et al, 2021). We selected the heavy metals that were measured for all the cities, those metals were copper (Cu), lead (Pb), zinc (Zn), manganese (Mn), and iron (Fe).…”

“…In Mérida, Cu, Zn, and Pb have been associated with vehicular traffic, because the highest concentrations have been found in the historic center and on primary roads. When observing the dust particles under a microscope, spherical particles of anthropic origin with these associated metals were found (Aguilar et al, 2021).…”

“…On the other hand, it is necessary to establish a monitoring system for heavy metals in the dust of the streets, soils, and plants of Mexican cities, as well as pollution indicators with proxy characteristics (easy analysis and low cost) that allow the analysis of thousands of dust samples to identify the sites of high concentration of heavy metals. In this sense, magnetic (Sánchez-Duque et al, 2015;Aguilera et al, 2020) and colorimetric (Cortés et al, 2015;Sanleandro et al, 2018;Aguilar et al, 2021) techniques are promising.…”

“…Diagnoses of contamination by heavy metals in urban dust have been carried out in some of these cities of Mexico. In Mérida and Ensenada the color of urban dust has proved to be an indicator of heavy metal pollution, dark colors are more polluted than light ones (Cortés et al, 2015;Aguilar et al, 2021). In San Luis Potosí, the highest concentrations of heavy metals in urban dust have been related to the metallurgical complex and the industrial park (Aguilera et al, 2019); and heavy metals in soils could also be an important pathway of exposure (Perez-Vazquez et al, 2015;Pérez-Vázquez et al, 2015), indeed metal concentrations have been identified in children (Flores-Ramírez et al, 2018).…”

Las Granjas Porcinas en Zonas De Karst: ¿cómo Pasamos De La Contaminación a La Sustentabilidad?

“…Contiene pequeñas cantidades de otros minerales como óxidos de hierro de color rojo y silicatos, entre otros. Las partes menos duras de la caliza se solubilizan y es allí donde se van formando numerosas grietas, hoyos, dolinas, uvalas y en general diferentes longitudes y tamaños de conductos que llevan el agua de lluvia hasta el acuífero, alimentándolo durante la época de lluvias (Aguilar et al, 2021).…”