Differentiation of Surface Water and Groundwater in a Karst System Using Anthropogenic Signatures

Benjamin Maas,Joe Honings,Eric Peterson,Prince Oware,Andrew Watson,Ian Rusthoven,Andrew Oberhelman

doi:10.3390/geosciences9040148

Benjamin Maas, Joe Honings + Show 5 more

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https://doi.org/10.3390/geosciences9040148

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Abstract

Surface water–groundwater interaction within a karstic system enhances contaminant transport, making karst aquifers susceptible to anthropogenic practices. Contaminated waters related to agricultural and animal husbandry in northwestern Illinois (USA) prompted this investigation. Six streams and five springs were sampled for 16 parameters to assess anthropogenic influences. Statistical analyses revealed differences in 13 of 16 parameters between the stream and spring waters. Rock–water interaction was identified as the dominant mechanism defining the chemistry for both waters, which were classified as Ca-Mg HCO3. Elevated nitrate as nitrogen (NO3-N), chloride (Cl−), sodium, and potassium concentrations indicate that human activities have influenced the quality of both water types. All streams and springs had NO3-N concentration exceeding background levels, with concentrations ranging from 2.9 to 14.5 mg/L and 2.9 to 30.1 mg/L, respectively. NO3-N/Cl relationships at individual locations showed elevated concentrations of NO3-N due to fertilizers, while the spring waters were influenced by manure, septic effluent, or mixed sources. The presence of coliform supports the likelihood of animal or human waste influences on waters. Dissimilarities within their chemical fingerprints can be traced to aid in differentiating sources within the waters.

Highlights

About 17% of the Earth’s surface is covered by carbonate rocks [1] and between 7%–10% of theEarth’s surface is considered karst [1,2]
Total dissolved solids (TDS) and Cl-HCO3 vs. TDS relationships of the world’s major surface waters, Gibbs [53] identified the dominant mechanisms controlling the water chemistry: atmospheric precipitation—chemistry is controlled by the ions sourced from precipitation; rock-water interaction—chemistry is controlled by dissolved ions from the rocks and soils of their basin; and evaporation-crystallization—chemistry is controlled by the concentration of ions as water evaporates from the source
While there there were werestatistical statisticaldifferences differencesininthe the spring and stream water quality parameters, While spring and stream water quality parameters, the the similar water type, calcium-magnesium bicarbonate, highlights water–rock interaction as the similar water type, calcium-magnesium bicarbonate, highlights water–rock interaction as the controlling process defining the geochemistry of the stream and spring waters

Summary

Introduction

About 17% of the Earth’s surface is covered by carbonate rocks [1] and between 7%–10% of theEarth’s surface is considered karst [1,2]. The dissolution develops a high secondary porosity and permeability in the rock, allowing the karst unit to serve as an aquifer. Numerous studies have examined the impact that humans have on karst areas (e.g., [4,5,6,7,8,9,10,11,12]) These studies highlight possible sources of pollutants, including the application of fertilizers and pesticides to fields [6,13,14], road salt [15], leaky septic systems [16,17], and wastewater [10,18,19]. 2.5 mg/L [5,6,16], with concentrations above that level indicative of anthropogenic influences [26].

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