By A. Sanchez, F. Bautista, R. Cejudo, A. Goguichaishvili, J. Reyes, F. Solis and J. Morales

Many studies have shown that the magnetic increase in urban dust is related to the heavy metal pollution. Urban dust contains heavy metals circulating in the atmosphere of the cities. The skin contact, oral intake, and breathing of urban dust is related to serious health problems such as cancer. Chronic exposure of the population to urban dust is a public health problem. The objective of this work was the assessment of pollution using the magnetic increase in urban dusts.

Assessments of magnetic increase on urban dust samples collected on different surfaces, mostly paved and unpaved roads, were performed in order to evaluate the environmental contamination in Mexicali City (medium-sized city on the Mexico-USA border). Rock and mineral magnetic techniques consisted of systematic measurements of mass-specific magnetic susceptibility and isothermal remanent magnetization at 0.7 T.

Magnetic increase was estimated by comparing magnetic concentration for each sample relative to reference value obtained from the site with almost no human activity also known as conservation area in the suburb of town. Additional magnetic parameters as the S-200 ratio and Curie temperatures were used to identify predominant magnetic carriers.

Sánchez-Duque et al._Figura2

Figure 1. Magnetic susceptibility and Saturation Isothermal Remanent Magnetization in urban dust from divers soil urban uses
Sánchez-Duque et al._Figura6

Figure 2. Map of the mangnetic increace as pollution indicator.

Geostatistical analysis and interpolation techniques (experimental variogram and ordinary Kriging, respectively) were carried out in order to determine the spatial distribution of magnetic enhancement and relative levels of environmental contamination.

The results indicate that impure magnetic is the main mineral in most studied samples, other results are:

  1. The background values of the magnetic signal is located in the Conservation Area
  2. At sites with different levels of pollution, the magnetic signal was dominated by non-stoichiometric magnetite and grain coarse. Particles are essentially anthropogenic combustion product.
  3. The highest level of the magnetic increase occurred in areas of high traffic as well as in industrial, commercial and services areas.
  4. In the map we show the most polluted areas in which it should take remedial action.

Paper

Sánchez-Duque, A., F. Bautista, A. Gogichaishvili, R. Cejudo-Ruiz, J. Reyes-López, F. Solís-Domínguez  y J. Morales-Contreras. 2015. Evaluación de la contaminación ambiental a partir del aumento magnético en polvos urbanos – Caso de estudio para la ciudad de Mexicali, México. Revista Mexicana de Ciencias Geológicas, http://satori.geociencias.unam.mx/en_prensa/SanchezDuque-ENPRENSA.pdf