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

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.

A Special Issue of Geosciences: Groundwater Pollution

“…The spatial analyses of both horizontal and vertical distribution of compound-specific stable isotopes in an industrial site located in a coastal aquifer turned out to be pivotal to unravelling the main biogeochemical processes acting at the site [2]. Specifically, in this issue, advanced applications and discussion of geospatial and geostatistical tools in large-scale pollution studies are related to mapping, monitoring, and assessing the trends of widespread contaminants like nitrate [3] or arsenic using reliable predictors to forecast their geogenic or anthropogenic origin [4], or to map the risk and vulnerability of aquifers [5]. Finally, a case study from an historical dumpsite in South Africa with a long term monitoring of a leachate dissolved plume gives an overview of the impact of such activities on groundwater resources [6].…”