Reliable Predictors of Arsenic Occurrence in the Southern Gulf Coast Aquifer of Texas

Kartik Venkataraman,John Lozano

doi:10.3390/geosciences8050155

Kartik Venkataraman, John Lozano

Open Access

https://doi.org/10.3390/geosciences8050155

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Journal: Geosciences	Publication Date: Apr 27, 2018
Citations: 1	License type: CC BY 4.0

Affiliation: Tarleton State University

Abstract

Arsenic contamination of groundwater in the Southern Gulf Coast Aquifer of Texas is a critical public health concern as much of the area is rural in nature with decentralized water supplies. Previous studies have pointed to volcanic deposits as the regional source of arsenic but no definitive or reliable predictors of arsenic maximum contaminant level (MCL) exceedance have been identified. In this study, we have studied the effect of various hydrogeochemical parameters as well as soil and land-use variables on arsenic MCL exceedance using logistic regression (LR) techniques. The LR models display good accuracy of 75% or higher but suffer from a high rate of false negatives, highlighting the challenges in capturing the spatial irregularities of arsenic in this region. Despite not displaying high statistical significance, pH appears to be an important variable in the LR models—its effect on arsenic exceedance is not clear and warrants further investigation. The results of the study also show that groundwater vanadium and fluoride are consistently the only significant variables in the models developed; the positive coefficients for both these elements indicates a common geogenic source for arsenic, fluoride and vanadium, corroborating the findings of earlier studies.

Highlights

Exposure to drinking-water supplies contaminated by arsenic has been widely-recognised as one of the most significant human health threats of the last few decades
It was determined that the following variables did not display any statistical significance to merit inclusion in the model development process: dissolved calcium, magnesium, sodium, chloride, sulphate, nitrate, selenium, soil organic matter (SOM), soil hydrologic group (SHG) and LULC
Univariate analysis of the explanatory variables showed that only aquifer stratigraphic unit, pH, fluoride and vanadium were significant at p < 0.25

Summary

Introduction

Exposure to drinking-water supplies contaminated by arsenic has been widely-recognised as one of the most significant human health threats of the last few decades. Asia [9,10,11,12,13], Latin and South America [14,15,16], Europe [17,18,19], as well as the United States [20,21,22,23,24] In many of these areas, the arsenic is geogenic in nature but human activities such as pumping and irrigation water return have been implicated in its release and migration from the parent source into groundwater.

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