Exploratory Analysis of Sediment Geochemistry to Determine the Source and Dispersion of Ba, Fe, Mn, Pb and Cu and in Chihuahua, Northern Mexico

Abstract

Exploratory Data Analysis (EDA) was applied to a sediment geochemistry data set (N = 2,584) within the Chihuahuan Desert in northern Mexico. Each data point contained information on the location, concentration of 19 elements, and lithology. A Box Plot analysis was applied to the data to determine mild and extreme anomaly thresholds. Anomaly maps revealed areas of concentration of anomalies as well as dispersion patterns for each element; Ba was the most mobile of the five elements and Pb the least. Specific potential sources of contamination were identified visually after superimposing anomalies with map layers of mines, urban centers and/or hydrology. The patterns revealed that mining was an important source of Pb, Fe, Mn and Ba contamination, while copper instead was associated to the presence of Tertiary volcanic rocks that abound in the western edge of the study area. Multi-element exploratory techniques yielded four principal components that accounted for 74% of total variance, exposing a strong association among Fe, Mn, P and Mg in PC1, Ca and Sr in PC2, Co, Cu, Cr, and Ni in PC3 and Pb in PC4. By identifying potential contaminant sources, EDA shed some light into the nature of the contamination, if natural or anthropogenic, a critical piece of information to impact assessment studies and best management plans.

Shallow Subsurface Stratigraphy Inferred from the Use of Vertical Electrical Soundings (VES) Survey in Central Chihuahua, Mexico

“…The El Sauz-Encinillas' aquifer (ESE), located 90 kilometers north of Chihuahua City, is an important source of water to its population. A spike in groundwater extraction from water wells within the area has led to degradation of water quality, rapid drawdowns, and change of groundwaters' flow direction [1]. Previous work in this aquifer was related to geology [2] [3] [4] [5], geophysics [6] [7] [8] [9] [10], hydrogeology [1] [11]- [16] and groundwater flow models [17] [18] [19].…”

“…A spike in groundwater extraction from water wells within the area has led to degradation of water quality, rapid drawdowns, and change of groundwaters' flow direction [1]. Previous work in this aquifer was related to geology [2] [3] [4] [5], geophysics [6] [7] [8] [9] [10], hydrogeology [1] [11]- [16] and groundwater flow models [17] [18] [19]. However, this work has focused mostly on the south-central portion of the ESE's aquifer, where most of wells are located.…”

Arsenic and Fluoride Variations in Groundwater of an Endorheic Basin Undergoing Land-Use Changes

“…In arid and semiarid regions of Mexico and nearby areas, these potentially toxic elements have been attributed mainly to its natural (geogenic) occurrence (Planer-Friedrich et al 2001;Gutiérrez et al 2009;Ortega-Guerrero 2009;Scanlon et al 2009;ReyesGómez et al 2013) and, in some cases, to environmental degradation generated by human activities, such as landuse change, presence of mine tailings, and presence of chemical and agricultural wastes (Alarcón-Herrera et al 2001a;Razo et al 2004;Armienta and Segovia 2008;Gutiérrez et al 2012).…”