Vulnerability Of Karst Aquifers Research Articles

Development of a hybrid Karst Aquifer Vulnerability map by using geospatial and statistical tools. The case study of Ziria aquifer in Northern Peloponnese

Aquifer vulnerability assessment constitutes a crucial tool for the protection and sustainable management of groundwater resources, particularly in complex karst aquifers. This study conducted a detailed comparative analysis of two tailored and widely used vulnerability mapping methodologies, COP and PaPRIKa, to evaluate their performance within a Mediterranean karst groundwater system. The methods were employed for the development of a hybrid vulnerability map after geospatial and statistical analysis. Both COP and PaPRIKa were applied using a combination of geological, hydrological, and geomorphological aquifer characteristics that can potentially influence its vulnerability to contamination. While COP predominantly assigned Low and Very Low vulnerability values across the study area, PaPRIKa identified the Moderate class as dominant, suggesting a finer sensitivity to karst-specific features. To address potential biases in PaPRIKa, a single-parameter sensitivity analysis was performed, leading to adjusted weights and the development of a modified version, PaPRIKa-Mod. A quantitative comparison of all three methods highlighted the varying degrees of consensus and discord, with PaPRIKa and its modification showing the highest consistency, suggesting robust methodological integrity. Conversely, the comparison of COP with either version of PaPRIKa revealed a lesser yet notable concordance, underscoring their capacity to be integrated and their potential to complement each other in vulnerability assessments. Finally, a hybrid vulnerability map was developed from the integration of similar vulnerability classes, attributing the most vulnerable setting prevailing across all methods. The methodological approach that was followed is adaptable and can provide significant insights for vulnerability estimations across different regions and methodological concepts.

Characterizing occurrence of emerging organic contaminants in Dinaric karst catchment of Jadro and Žrnovnica springs, Croatia

The occurrence of emerging organic contaminants (EOCs) was investigated in vulnerable Dinaric karst catchment of Jadro and Žrnovnica springs in Croatia, under varying flow conditions and across three different water resource types (groundwater, springs, and surface water). The maximal EOCs concentration in both springs were observed following autumn recharge events, while during peak discharge no detection above the limits of detection (LOD) was recorded due to dilution process. Contrarily to springs, groundwater from deep borehole exhibited highest total EOCs concentration under low flow conditions, underscoring the considerable karst aquifer vulnerability and its oligotrophic nature. The peak EOCs concentration in karstic Cetina River coincided with the river's lowest discharge. The highest mass flux of 1013 g/day was determined for very mobile pharmaceutical metformin detected in Cetina. The presence of potentially persistent to very persistent compounds, like DEET and 1H-benzotriazole, which exhibited highest detection frequencies across all sampling sites, was observed in association with varying hydrological conditions. Hypotheses regarding the occurrence of identified EOCs include surface contamination infiltrating directly through ponors and highly karstified areas, potential persistence in the epikarst and aquifer matrix, and site-specific contamination sources for compounds such as 1H-benzotriazole, gabapentin, and ketoprofen found in groundwater. To evaluate the risk of inadvertent human exposure to EOCs across various age groups, we utilized measured spring concentrations and calculated drinking water equivalent levels (DWEL), which ranged from 1.4 μg/L for cotinine to 503 mg/L for sucralose, both detected in Jadro spring. Although EOCs concentrations in ng/L are unlikely to pose a significant risk to healthy population, long-term exposure to EOCs mixture remains unknown. Given scarcity of research on EOCs in karst environments on both global and national levels, our study enhances comprehension of their occurrence and behaviour across different karst water resources that hold crucial importance for drinking water supply in regions like Dinarides.

Hydrogeological Aspects of the Municipal Water Supply of Albania: Situation and Problems

The municipal water supply, related mainly to the cities of Albania, began to develop in the second half of the 19th century and very intensively after 1945. Today, the reported mean water production for the cities, on average, is about 300 l/capita/d, including drinking and industrial water supplies. The territory of Albania has an uneven distribution of very heterogeneous aquifers conditioning often the difficulty of municipal water supply solutions. In this article, are analyzed and classified the hydrogeological aspects of the water supply sources of the settlements, which are summarized in five groups: (a) wells in alluvial intergranular aquifers; (b) karst springs; (c) wells in karst aquifers; (d) springs in fissured rocks; and (e) mixed water sources. For each group of the water supply sources, the main concerns regarding the quantity and quality problems are analyzed, facilitated by the description of a variety of representative examples of different situations. Based on the gained experience, important recommendations are given for the better understanding of hydrogeological aspects of water supply systems, related to the river water recharge areas, the seawater intrusion in coastal aquifers, and the high vulnerability of karst aquifers, as well as transboundary aquifers. However, the main problem of public water supply of Albania remains the poor management of water supply systems, which is reflected in the significant water losses, as well as the low public awareness of requests for sustainable use.

First Steps to understanding Intrinsic Vulnerability to Contamination of Karst Aquifers in Various South American and Caribbean Countries

Protecting groundwater in karst aquifers is extremely impor­tant. Vulnerability maps can greatly help proper decision mak­ing based on physical environmental attributes that influence how easily a contaminant applied to the land surface can reach groundwater due to anthropogenic activities, and the proper­ties of the contaminants. Methods for determining vulnerabil­ity based on the COST Action 620 Approach, when applied in the study area, may lead to contradictory results. The main purpose of this study is to provide an overview of academic research on intrinsic karst aquifer vulnerability methodologies applied in South American and Caribbean countries. Secondly, it describes studies related to karst aquifers that, in some cases, lack specific information on intrinsic vulnerability. The objec­tive is to encourage and to help develop specific methods for determining karst vulnerability in these regions. To achieve these purposes, a systematic literature review was conducted including studies conducted at institutions such as universities, national water institutes, and by geological services. Several methods have been used in the region such as COP, DRAS­TIC, RISK, EPIK, PI, PaPRIka, and the Slovene Approach. And some attempts have been made to develop a specific methodol­ogy that best suits the specificities of the region’s karst aqui­fers. South America and the Caribbean have almost 5 % of the world´s carbonate rocks. Some countries have large extensions of their territory covered by karst rocks, such as Peru, 15.4 %; Cuba, 67 %; and Mexico 25.29 %. Estimates indicate that more than 10 million people use water from karst systems in Mexico. In Cuba, 33 % of all available water volume originates from groundwater, and 91.51 % from karst aquifers. In Mexico, 13 studies have been conducted on the importance of karst aqui­fers, which mostly address the Yucatan Peninsula, followed by Brazil (9 studies), Cuba (5), Colombia (1) and Peru (1). Infor­mation about the theme is scarce in most of the other countries in the region. Some studies have incongruent results given the regional characteristics of tropical karst.

Contamination vulnerability assessment of the Bambuí karst aquifer, in the Terra Ronca region - Goiás, Brazil

Karstic environments are characterized as areas of intense rock dissolution, which allows the generation of several typical features, such as sinkholes, resurgences, caves, and dolines. The spatial distribution of these features is of great importance to identify the contamination vulnerability of karst aquifers and serve as a basis for the application of assessment methods. This study aimed to identify and classify the areas vulnerable to underground contamination in the karstic region of the Terra Ronca State Park (PETeR) and its surroundings. The method chosen was the COP, which assesses the physical conditions of the environment (relief, lithology, soils, precipitation, karst features, and vegetation) to determine the areas naturally vulnerable to contamination. The analyses were performed in a GIS environment. The results indicated five categories of areas vulnerable to groundwater contamination: Very High to High (3.14%), Moderate (16.21%), and Low to Very Low (80.62%). The Terra Ronca State Park was the analysis unit with the highest vulnerability in the region (9.91%), due to the concentration of karstic features in the area. The acquired results aim to help in the underground water resources conservation as well as the speleological patrimony.

High-resolution multi-parameter monitoring of microbial water quality and particles at two alpine karst springs as a basis for an early-warning system

Karst aquifers are important resources for drinking water supply and are very vulnerable to contamination. Microbial concentrations at karst springs, in particular, often vary quickly over a short period of time. In this study, the response of microbial water quality and particle-size distribution of two alpine karst springs to rainfall events was investigated to test and validate parameters that can be used as early-warning systems for fecal contamination. At both investigated karst springs, total organic carbon, particle-size distribution (especially small particle fractions), and particle load show a good correlation to the fecal indicator bacteria E. coli and can therefore be used as a real-time indicator of fecal contamination at the investigated springs. In addition to conventional bacterial determination methods, the β-D-glucuronidase activity, which can be measured in near real-time, was used as a novel indicator parameter for fecal contamination. At the event scale, the β-D-glucuronidase (GLUC) activity shows a good correlation to E. coli and can be used as an additional real-time indicator of fecal contamination. For the studied springs, when they show two peaks in turbidity and small particles, these two parameters are suitable for an early warning system because the bacterial contamination occurs during the secondary peak of these parameters. These results highlight the vulnerability of karst aquifers and demonstrate the applicability of advanced measurement techniques in detecting fecal contamination in real-time, which is especially important given the time-consuming nature of conventional bacterial detection methods.

First application of the Integrated Karst Aquifer Vulnerability (IKAV) method – potential and actual vulnerability in Yucatán, Mexico

Abstract. Groundwater vulnerability maps are important decision support tools for water resource protection against pollution and helpful in minimizing environmental damage. However, these tools carry a high subjectivity along the multiple steps taken for the development of such maps. Additionally, the theoretical model on which they are based does not consider other important parameters, such as pollutant concentration or pollutant residence time in a given section of the aquifer, solely focusing on the theoretical travel time of a pollutant particle from a release point towards a target. In this work, an integrated methodology for the evaluation of potential (intrinsic) and actual vulnerability is presented. This integrated method, named Integrated Karst Aquifer Vulnerability (IKAV), was developed after the analysis of several study cases around the world and the application of multiple intrinsic groundwater vulnerability methods in a selected study area. Also, a solute transport model served as the basis to define additional parameters for vulnerability analysis for areas severely affected by anthropogenic practices. However, the focus of the transport model must not be mistaken to be hazards and risk mapping. A defined workflow and several criteria for parameters and attributes selection, rating and weighting, and vulnerability classification are presented here. The first application of the IKAV method was carried out in the Yucatán karst, demonstrating to be a reliable method for vulnerability estimation. Results demonstrated the scope of the IKAV method in highlighting important regional conditions, minimizing the subjectivity, and expanding the analysis of vulnerability.

Hydrogeochemistry of karst groundwater for the environmental and health risk assessment: The case of the suburban area of Chongqing (Southwest China)

Karst groundwater is a vital resource for drinking, living and irrigation purposes in karst agricultural areas of the world. Due to the vulnerability of karst aquifers, surface pollutants are easily transferred to the subsurface and make karst groundwater be deteriorated, thereby restricting the rational exploitation of karst groundwater resource. In view of this, 49 karst groundwater samples were collected from spring (SW) and underground river (URW) sites in the suburban area of Chongqing City and analyzed for various hydrochemical components. Particularly, the karst groundwater quality was comprehensively uncovered by combining characteristics of hydrogeochemical evolution and health risks caused by nitrate and fluoride. The results revealed that the karst groundwater was slightly alkaline in nature and the water types were mainly characterized by Ca-HCO3 accounting for 93.88% of the total samples due to the heavy dissolution of carbonate rock. The relatively high concentrations of Na+, SO42− and NO3− up to 271.88 mg/L, 277.94 mg/L and 56.94 mg/L were over the corresponding maximum acceptable limits for drinking water, which can be predominately attributed to the emissions of industrial park, dissolution of gypsum and pyrite and excessive application of chemical fertilizers. Although agricultural activities were stopped and chemical fertilizers were no longer applied during the sampling period, long-term application of fertilizers have a persistent adverse effect on the karst groundwater NO3−. The pollution index of the karst groundwater (PIG) revealed that the low pollution and potential pollution zones were noticed in the northwestern parts of the study area. With respect of the SW, all the total hazard index (HI) values were below 1 suggesting no significant health risk. On the contrary, HI values of 0.11–1.16 for adults, 0.15–1.61 for children and 0.17–1.83 for infants in the URW indicated significant noncarcinogenic health risks. Particularly, infants and children were more vulnerable to karst groundwater NO3− than adults. Furthermore, the noncarcinogenic health risks of karst groundwater can be mainly attributed to NO3−, confirmed by the higher contribution ratio (66.55%) to the HI values. Therefore, special and targeted measures need to be taken to decrease the NO3− concentration in agricultural area.

Nitrate vulnerability of karst aquifers and associated groundwater-dependent ecosystems in the Baltic region

Groundwater pollution by agrochemicals such as nitrogen fertilizers can cause complex biogeochemical transformations to take place in groundwater-dependent ecosystems. To explore the interaction between nitrogen load and groundwater-dependent, spring-fed ecosystems, a study was conducted in Latvia in an area of suspected high nitrate (NO3−) vulnerability due to its geological settings. A map of NO3− vulnerability along the margins of the carbonate aquifer in Latvia is presented. The map is based on a conceptual model that was developed during an extensive case study involving hydrological, hydrochemical, and habitat investigation of springs discharging from a karst aquifer and spring-fed ecosystems. Areas that should be prime targets for restricting fertilizer application are highlighted on the map. Although the case study revealed increased nitrogen pollution (up to 51 mg L−1, standard deviation of 9 mg L−1, in the springs discharging from the karst aquifer), no clear evidence of adverse effects due to NO3− pollution on the groundwater-dependent ecosystems using biotic indicators was found, highlighting the resilience of spring-fed ecosystems against high nitrogen inputs. In the case study, downstream groundwater-dependent ecosystems retained 70% of the reactive nitrogen during the vegetation season, but only a small proportion during the cold season. Thus, NO3− pollution can be partly mitigated by restoring wetlands along valley slopes where natural groundwater discharge takes place. The conceptual model developed for groundwater NO3− vulnerability is applicable to other areas in the Baltic region and other places with similar climatic and geological conditions.

Karst Aquifer Vulnerability Assessment (KAVA) Method—A Novel GIS-Based Method for Deep Karst Aquifers

Karst aquifers in the Dinaric karst are very rich with groundwater and are a very important resource for public water supply. The characteristics of the Dinaric karst are the lack, or very thin layer, of covering deposits, large amounts of precipitations, high groundwater velocities, very deep groundwater flow with a lot of faults and fault zones, pits to groundwater, concentrated sinking and large karst springs, making them extremely vulnerable to all anthropogenic influences, which are very quickly transmitted to the aquifer. Numerous multiparameter methods have been developed in the last 20 years to determine the level of vulnerability of aquifers. Each of them has its own specifics and is well adapted to the climate and region for which it was developed. The Karst Aquifer Vulnerability Assessment (KAVA) method was developed in accordance with all the characteristics of the deep karst aquifers of the Dinaric karst and tested on several basins in the area. It was developed as a part of the Global Environment Facility United Nations Environmental Programme – the Mediterranean Action Plan Strategic Partnership for the Mediterranean Sea Large Marine Ecosystem (GEF UNEP/MAP MedPartnership Project). This paper presents the KAVA method and its application to two characteristic karst basins of the Dinaric karst: the Novljanska Žrnovnica spring catchment area and the Bakar Bay catchment area.

Bibliometric analysis of research progress on karst groundwater pollution

The hydrological conditions in karst areas are complex. Due to the special karst structure, the surface and aquifers are closely connected through surface karsts, sinkholes, etc., making the karst aquifers vulnerable to pollution. In recent years, human activities and climate change have also exacerbated this phenomenon. Understanding the key knowledge and research status of karst groundwater pollution is an important prerequisite for subsequent research. Based on the CiteSpace software, this paper analyzed the related papers on karst groundwater pollution in the core database of Web of Science, intending to sort out the research results in this field and explore potential research hotspots. Analysis results show that: (1) In recent years, the number of publications and citations in this field has gradually increased, and there is a large space for research and development; (2) The United States, China, Germany are the countries that have contributed the most in this field. The number of research results in this field supported by the National Natural Science Foundation of China is in a leading position in the world; (3) The identification and protection of the vulnerability of karst aquifers, modeling of groundwater flow and pollutant migration are the main research directions. Water chemical analysis, tracer experiment and numerical modeling are the main research methods in this field; (4) The migration of organic micro-pollution, the trace of groundwater flow, the distribution of biodiversity and control factors, the characterization of karst conduits and the simulation of conduit flow, and the development of new tracer isotope fractions are potential development directions and breakthrough points in this field. In general, the research on karst groundwater pollution in the future is inseparable from the cross-integration of various disciplines, the mutual verification of multiple methods, and the introduction of new technological methods.

Modeling intrinsic vulnerability of complex karst aquifers: modifying the COP method to account for sinkhole density and fault location

This study investigates a method of karst-aquifer vulnerability modeling that modifies the concentration-overburden-precipitation (COP) method to better account for structural recharge pathways through noncarbonate rocks, and applies advancements in remote-sensing sinkhole identification. Karst aquifers are important resources for human and agricultural needs worldwide, yet they are often highly complex and have high vulnerability to contamination. While many methods of estimating intrinsic vulnerability of karst aquifers have been developed, few methods acknowledge the complication of layered karst aquifer systems, which may include interactions between carbonate and noncarbonate rocks. This paper describes a modified version of the COP method applied to the Kaibab Plateau, Arizona, USA, the primary catchment area supplying springs along the north side of the Grand Canyon. The method involves two models that, together, produce higher resolution and greater differentiation of vulnerability for both the deep and perched aquifers beneath the Kaibab Plateau by replacing the original sinkhole distance parameter with sinkhole density. Analyses indicate that many karst regions would benefit from the methodology developed for this study. Regions with high-resolution elevation data would benefit from the incorporation of sinkhole density data in aquifer vulnerability assessments, and deeper semi-confined karst aquifers would benefit greatly from the consideration of fault location.

First Steps into an Integrated Karst Aquifer Vulnerability Approach (IKAV). Intrinsic Groundwater Vulnerability Analysis of the Yucatan Karst, Mexico

Karst groundwater vulnerability maps are important tools for the development of groundwater management and protection strategies. However, current methodologies do not always match regional characteristics and parameter adaptations are necessary. In addition, other important processes such as dilution and aquifer residence time are not included in vulnerability analysis for the complications of evaluating two or more criteria simultaneously. The integrated karst aquifer vulnerability approach (IKAV) project aims to develop an integrated approach to include these parameters and estimate global change implications in current and future scenarios. As a first step, intrinsic vulnerability methodologies are studied in order to highlight important parameters and the congruence with regional characteristics of the Yucatan karst. Results demonstrate agreement between methods for the evaluation of high and very high vulnerabilities and their relation with fissures and dolines. Moderate vulnerabilities are assigned to more than 50% of the area. However, moderate vulnerabilities, assigned to the coastal area and the Southern hill, are highly questionable. Intrinsic features affecting moderate classes vary according to the method. Parameter sensitivity analysis and overlap analysis demonstrate the influence of depth to the unsaturated zone, soils, precipitation, and slope on moderate values. Therefore, such parameters must be re-evaluated and discretized according to the characteristics of the study area to match Yucatan regional characteristics.

Estimating Pollutant Residence Time and NO3 Concentrations in the Yucatan Karst Aquifer; Considerations for an Integrated Karst Aquifer Vulnerability Methodology

Karst aquifers are a major source of drinking water with intrinsic features that increase the pollution risk from anthropogenic and natural impacts. In Yucatan, Mexico, groundwater is the sole source of drinking water, also acting as receptor of untreated wastewater due to the low regional coverage of sewer systems. To protect karst groundwater, vulnerability methodologies are widely used. Worldwide, multiple karst vulnerability schemes have been developed and tested; however, none of these consider pollutant residence time or pollutant concentration as core parameters to estimate vulnerability. This work aims to define important considerations regarding the behavior of nitrates (NO3) in a real scenario, to be included in a new integrated vulnerability method. This work has two main objectives: to set up a groundwater model to depict as close as possible the groundwater behavior of the Yucatan karst system, and to introduce a transport model to estimate the behavior of a pollution plume. Model outcomes suggest that pollutants have a short residence time, reaching the coast in the north after 3 years. Well fields are also affected by pollution at variable NO3 concentrations. Results can be further discretized to establish a base and to include these parameters as part of a new integrated groundwater vulnerability approach.

Challenges and Limitations of Karst Aquifer Vulnerability Mapping Based on the PaPRIKa Method—Application to a Large European Karst Aquifer (Fontaine de Vaucluse, France)

Aquifer vulnerability maps can improve groundwater management for sustainable anthropogenic development. The latest update of karst aquifer vulnerability mapping is named: the Protection of Aquifers base on Protection, Rock type, Infiltration and KArstification (PaPRIKa). This multi-criteria assessment method is based on a weighting system whose criteria are selected according to the aquifer under study. In this study, the PaPRIKa method has been applied in the Fontaine de Vaucluse karst aquifer using the novel plugin for Quantum Geographic Information System (QGIS) software. The Fontaine de Vaucluse karst aquifer is the largest European karst hydrosystem with a catchment area that measures approximately 1162 km 2 . Four thematic maps were produced according to the criteria of protection, rock type, infiltration, and karst development. The plugin expedites the weighting system test and generates the final vulnerability map. At a large scale the vulnerability map is globally linked with primary geomorphological units and at the local scale is mostly affected by karst features that drive hydrodynamics. In conclusion, the novel QGIS plugin standardizes the application of the PaPRIKa method, saves time and prevents user omissions. The final vulnerability map provides useful contributions that are most relevant to groundwater managers and decision-makers. We highlight the sensibility of the vulnerability map to the weighting system and validation issues of the vulnerability map are raised.

Nitrate transport in a karst aquifer: Numerical model development and source evaluation

Protecting karst aquifers from nitrate contamination is an issue of global concern due to the inherent vulnerability of karst aquifers to contamination and the negative health effects of elevated nitrate levels. Hydrological and transport models were developed to assess nitrate transport within a karstic aquifer located in an area with both semi-arid and sub-humid climate conditions. Groundwater flow through the aquifer matrix and conduits was simulated with CFPv2, an experimental version of the Conduit Flow Process (CFP) version of the MODular FLOW (MODFLOW) groundwater model. Nitrate transport was simulated with the experimental Conduit Mass Transport Three-Dimensional Model (CMT3D). The hydrologic calibration of the steady-state model was successful based on a scaled Root Mean Squared Error (RMSE) of 4.9% for hydraulic heads and percent errors of 3.0% and 6.6% for the two major springs in the area. Performance of the transient hydrologic model exceeded the performance of the existing Equivalent Porous Media (EPM) model with a scaled RMSE of 2.2% and springflow errors of 1.5% and 2.8% for the major springs. Similarly, nitrate calibration was successful with all Percent Bias (PBIAS) values between ±25%. Additional calibration statistics including a two-tailed t-test indicated successful calibration. The CMT3D model corroborates prior research findings that anthropogenic sources as well as biogenic wastes are important sources of nitrate to the aquifer. The methodology used in this study represents an additional tool for watershed managers to address nitrate contamination within karst aquifers.

A new approach for using GIS to link infiltration BMPs to Groundwater Pollution Risk

ABSTRACTThis research analyzed the efficiency of the BMP Siting Tool developed by the US Environmental Protection Agency and the Grey-to-Green Decision Support Tool. Both tools were used in conjunction with ArcGIS 10.1 to obtain cartographic data illustrating suitable sites for bioswales and infiltration basins in Hillsborough County, Florida. The data were integrated with the Karst Aquifer Vulnerability Index (KAVI) groundwater vulnerability model. The BMP Siting Tool sited 2.80% of all bioswales and 27.89% of all infiltration basins above vulnerable areas identified by the KAVI. Alternatively, 21.66% of all bioswales and 9.62% of all infiltration basins sited by the Grey-to-Green Decision Support Tool were above vulnerable areas. The results of this analysis prompted the proposal of a supplemental framework unique to each tool’s weakness. The idea behind the supplemental framework is to determine the most suitable sites for stormwater BMPs by refining the current siting framework to better respect groundwater integrity.

Assessment of groundwater recharge processes through karst vadose zone by cave percolation monitoring

AbstractRecharge processes of karst aquifers are difficult to assess given their strong heterogeneity and the poorly known effect of vadose zone on infiltration. However, recharge assessment is crucial for the evaluation of groundwater resources. Moreover, the vulnerability of karst aquifers depends on vadose zone behaviour because it is the place where most contamination takes place. In this work, an in situ experimental approach was performed to identify and quantify flow and storage processes occurring in karst vadose zone. Cave percolation monitoring and dye tracing were used to investigate unsaturated zone hydrological processes. Two flow components (diffuse and quick) were identified and, respectively, account for 66% and 34% of the recharge. Quickflow was found to be the result of bypass phenomenon in vadose zone related to water saturation. We identify the role of epikarst as a shunting area, most of the storage in the vadose zone occurring via the diffuse flow component in low permeability zones. Relationship between rainfall intensity and transit velocity was demonstrated, with 5 times higher velocities for the quick recharge mode than the diffuse mode. Modelling approach with KarstMod software allowed to simulate the hybrid recharge through vadose zone and shows promising chances to properly assess the recharge processes in karst aquifer based on simple physical models.

Evaluation of occurrence of NO3–, Coliform and atrazine in a karst aquifer, Colombo, PR

ABSTRACT The vulnerability of karst aquifers to contamination by agrochemical compounds was studied. Such contamination occurs due to its geomorphological structure. Despite the fact, aquifers are important to provide potable water, there is a lack of research about karst aquifers in Brazil. The aim of this study was to evaluate the occurrence of nitrates, fecal coliform bacteria and atrazine in shallow and deep wells in the karst aquifer in the State of Paraná, which is affected by agricultural activities. This study was conducted in an intensive agricultural area located inside the basin of the Upper Iguassu/Ribeira in the Municipality of Colombo, Paraná in Brazil. The sampling campaigns were carried out between 2014 and 2015 in fifteen shallow wells and seven deep wells. Nitrates, total and fecal coliforms and atrazine were analyzed. Nitrates were found in higher concentration in all shallow wells, ranging from 0.14 mg L-1 and 40.22 mg L-1. In deep wells, the lower concentrations were between 1.24 mg L-1 e 17.86 mg L-1. The analysis of total and fecal coliforms showed the bias for nitrates. Atrazine was detected in five shallow wells and in four deep wells. Physico-chemical characteristics of atrazine as well as fractures of the karstic aquifer and high hydraulic conductivity can be considered as determining factors in the fate of pesticides.

Source, variability, and transformation of nitrate in a regional karst aquifer: Edwards aquifer, central Texas

Many karst regions are undergoing rapid population growth and expansion of urban land accompanied by increases in wastewater generation and changing patterns of nitrate (NO3−) loading to surface and groundwater. We investigate variability and sources of NO3− in a regional karst aquifer system, the Edwards aquifer of central Texas. Samples from streams recharging the aquifer, groundwater wells, and springs were collected during 2008–12 from the Barton Springs and San Antonio segments of the Edwards aquifer and analyzed for nitrogen (N) species concentrations and NO3− stable isotopes (δ15N and δ18O). These data were augmented by historical data collected from 1937 to 2007. NO3− concentrations and discharge data indicate that short-term variability (days to months) in groundwater NO3− concentrations in the Barton Springs segment is controlled by occurrence of individual storms and multi-annual wet-dry cycles, whereas the lack of short-term variability in groundwater in the San Antonio segment indicates the dominance of transport along regional flow paths. In both segments, longer-term increases (years to decades) in NO3− concentrations cannot be attributed to hydrologic conditions; rather, isotopic ratios and land-use change indicate that septic systems and land application of treated wastewater might be the source of increased loading of NO3−. These results highlight the vulnerability of karst aquifers to NO3− contamination from urban wastewater. An analysis of N-species loading in recharge and discharge for the Barton Springs segment during 2008–10 indicates an overall mass balance in total N, but recharge contains higher concentrations of organic N and lower concentrations of NO3− than does discharge, consistent with nitrification of organic N within the aquifer and consumption of dissolved oxygen. This study demonstrates that subaqueous nitrification of organic N in the aquifer, as opposed to in soils, might be a previously unrecognized source of NO3− to karst groundwater or other oxic groundwater systems.