Alessandro Gargini

Groundwater Pollution and Quality Monitoring Approaches at the European Level

The authors investigate the sources and processes of groundwater contamination and their assessment within the Drivers-Pressures-State-Impact-Response (DPSIR) framework. Naturally occurring substances, trace elements, radionuclides, nutrients, and salt (sodium chloride) are reviewed with emphasis on the assessment of the natural background load. Some synthetic substances are also considered, these being petroleum hydrocarbons, chlorinated aliphatics, pesticides and organic-waste contaminants. Newly emerging contaminants cannot be described within the DPSIR; therefore monitoring approaches and indicators of contamination are discussed in order to propose improved monitoring plans that combine physical, chemical and biological indicators and combine science with policy.

A stable isotope approach for source apportionment of chlorinated ethene plumes at a complex multi-contamination events urban site.

The stable carbon isotope composition of chlorinated aliphatic compounds such as chlorinated methanes, ethanes and ethenes was examined as an intrinsic fingerprint for apportionment of sources. A complex field site located in Ferrara (Italy), with more than 50years history of use of chlorinated aliphatic compounds, was investigated in order to assess contamination sources. Several contamination plumes were found in a complex alluvial sandy multi-aquifer system close to the river Po; sources are represented by uncontained former industrial and municipal dump sites as well as by spills at industrial areas. The carbon stable isotope signature allowed distinguishing 2 major sources of contaminants. One source of chlorinated aliphatic contaminants was strongly depleted in ¹³C (<-60‰) suggesting production lines which have used depleted methane for synthesis. The other source had typical carbon isotope compositions of >-40‰ which is commonly observed in recent production of chlorinated solvents. The degradation processes in the plumes could be traced interpreting the isotope enrichment and depletion of parent and daughter compounds, respectively. We demonstrate that, under specific production conditions, namely when highly chlorinated ethenes are produced as by-product during chloromethanes production, ¹³C depleted fingerprinting of contaminants can be obtained and this can be used to track sources and address the responsible party of the pollution in urban areas.

Toward operational methods for the assessment of intrinsic groundwater vulnerability: A review

ABSTRACT Assessing the vulnerability of groundwater to adverse effects of human impacts is one of the most important problems in applied hydrogeology. At the same time, many of the widespread vulnerability assessment methods do not provide physically meaningful and operational indicators of vulnerability. Therefore, this review summarizes (i) different methods used for intrinsic vulnerability assessment and (ii) methods for different groundwater systems. It particularly focuses on (iii) timescale methods of water flow as an appropriate tool and (iv) provides a discussion on the challenges in applying these methods. The use of such physically meaningful indices based on timescales is indispensable for groundwater resources management.

Analysis of Compound-Specific Chlorine Stable Isotopes of Vinyl Chloride by Continuous Flow–Isotope Ratio Mass Spectrometry (FC–IRMS)

A new method for determining compound-specific chlorine stable isotope was developed for vinyl chloride (VC). The analysis is carried out on a continuous flow–isotope ratio mass spectrometer (CF–IRMS) with special collectors for m/z 64 and 62. The precision of this technique is better than ± 0.16‰ (1σ) for pure phase gas injection and headspace solid phase microextraction (SPME) injection. The new methodology was tested in a confined sandy aquifer contaminated with VC located near the city of Ferrara, northern Italy. The VC isotopic signatures (37Cl and 13C) showed that the VC is not a primary manufactured compound and is a byproduct of production of petrochemicals in the Ferrara region during the 1970s and 1980s. The isotope data also suggested VC is attenuated by biodegradation along the groundwater flow system. The development of compound-specific isotope analysis (CSIA) for VC offers a new tool for fingerprinting sources and processes that affect VC in groundwater.

A global review on ambient Limestone-Precipitating Springs (LPS) : Hydrogeological setting, ecology, and conservation

Springs are biodiversity hotspots and unique habitats that are threatened, especially by water overdraft. Here we review knowledge on ambient-temperature (non-geothermal) freshwater springs that achieve sufficient oversaturation for CaCO3 -by physical CO2 degassing and activity of photoautotrophs- to deposit limestone, locally resulting in scenic carbonate structures: Limestone-Precipitating Springs (LPS). The most characteristic organisms in these springs are those that contribute to carbonate precipitation, e.g.: the mosses Palustriella and Eucladium, the crenophilous desmid Oocardium stratum, and cyanobacteria (e.g., Rivularia). These organisms appear to be sensitive to phosphorus pollution. Invertebrate diversity is modest, and highest in pools with an aquatic-terrestrial interface. Internationally, comprehensive legislation for spring protection is still relatively scarce. Where available, it covers all spring types. The situation in Europe is peculiar: the only widespread spring type included in the EU Habitat Directive is LPS, mainly because of landscape aesthetics. To support LPS inventorying and management to meet conservation-legislation requirements we developed a general conceptual model to predict where LPS are more likely to occur. The model is based on the pre-requisites for LPS: an aquifer lithology that enables build-up of high bicarbonate and Ca(2+) to sustain CaCO3 oversaturation after spring emergence, combined with intense groundwater percolation especially along structural discontinuities (e.g., fault zones, joints, schistosity), and a proper hydrogeological structure of the discharging area. We validated this model by means of the LPS information system for the Emilia-Romagna Region (northern Italy). The main threats to LPS are water diversion, nutrient enrichment, and lack of awareness by non-specialized persons and administrators. We discuss an emblematic case study to provide management suggestions. The present review is devoted to LPS but the output of intense ecological research in Central Europe during the past decades has clearly shown that effective conservation legislation should be urgently extended to comprise all types of spring habitats.

Modelling the fate of styrene in a mixed petroleum hydrocarbon plume

Severe petroleum hydrocarbon contamination (styrene and the BTEX compounds: benzene, toluene, ethylbenzene and the isomers of xylene) from leaking sewers was detected in a Quaternary aquifer below a chemical plant in the Padana Plain, Italy. From 1994, active pump and treat remediation has been employed. The site is bordered by canals which, in combination with variable pumping rates and groundwater flow directions, control groundwater levels. In this study we sought to determine the fate of styrene at the site within a mixed styrene/BTEX plume where the hydraulic boundaries induced strong seasonal variations in flows. In order to determine the fate of styrene, detailed field investigations provided intensive depth profile information. This information was then incorporated into a staged flow and reactive transport modelling. Three sets of measurements were obtained from sampling multilevel samplers (MLSs) under different hydraulic conditions at the site. These included measurements of BTEX, styrene, all major ions, pH and redox potential. A three-dimensional transient flow model was developed and calibrated to simulate an unconfined sandy aquifer with a variable flow field. Subsequently a reactive, multi-component transport model was employed to simulate the fate of dissolved BTEX and styrene along a selected flow line at the site. Each petroleum hydrocarbon compound was transported as independent species. Different, kinetically controlled degradation rates and a toxicity effect were simulated to explain the observed, selective degradation of pollutants in groundwater. Calibration of the model was accomplished by comparison with the three different sets of measurements obtained from the MLS devices. The results from various scenarios show that the detailed simulation of geochemical changes can be very useful to improve the sites conceptual model.

Groundwater Modeling of Fractured Aquifers in Mines: The Case Study of Gavorrano (Tuscany, Italy)

In this paper, we describe the hydrogeological problems related to the closure of the mine at Gavorrano (Tuscany, Italy). The geological and geo-structural settings of the Gavorrano area affect the groundwater flow systems and their chemical composition; hence, the settings also affect the chance and modalities to rehabilitate and re-utilize these water resources. This paper reports the results of studies, analyses of existing data and the consequent implementation of preliminary numerical models with particular reference to the effects of controlled water recovery and the complex measures required for stopping dewatering. The study incorporates recent data and the available historical records in an analysis of the hydrodynamic impact of water recovery and an assessment of the consequences of water recovery for water resources restoration. The applied numerical simulations have been demonstrated to be a promising and effective tool for planning and managing the future applications of groundwater recovery in the Gavorrano mining area. Using these applications, it will be possible to implement mitigation measures and types of re-use that consider thermal, chemical and discharge features.

Does groundwater protection in Europe require new EU-wide environmental quality standards?

The European Groundwater Directive could be improved by limiting the scopes of the Annexes I and II to the manmade and natural substances, respectively, and by defining a common monitoring protocol. The changes in the European landuse patterns, in particular the urban sprawl phenomena, obscure the distinction between the point and diffuse sources of contamination. In the future more importance will be given to the household contamination. Moreover, the agricultural environment could be used for developing new conceptual models related to the pharmaceuticals.

A conceptual hydrogeological model of ophiolitic aquifers (serpentinised peridotite): The test example of Mt. Prinzera (Northern Italy)

&NA; The main aim of this study is the experimental analysis of the hydrogeological behaviour of the Mt. Prinzera ultramafic massif in the northern Apennines, Italy. The analysed multidisciplinary database has been acquired through (a) geologic and structural survey; (b) geomorphologic survey; (c) hydrogeological monitoring; (d) physico‐chemical analyses; and (e) isotopic analyses. The ultramafic medium is made of several lithological units, tectonically overlapped. Between them, a low‐permeability, discontinuous unit has been identified. This unit behaves as an aquitard and causes a perched groundwater to temporary flow within the upper medium, close to the surface. This perched groundwater flows out along several structurally controlled depressions, and then several high‐altitude temporary springs can be observed during recharge, together with several perennial basal (i.e., low altitude) springs, caused by the compartmentalisation of the system because of high‐angle tectonic discontinuities.

A decision tree tool supporting the assessment of groundwater vulnerability

The Water Framework Directive and Groundwater Directive aim at preserving and improving the groundwater status. Groundwater bodies are classified as being or not being at risk of failing to meet these objectives. Those at risk are subject to more precise risk assessment where the concept of vulnerability is considered in the pathway part of the source–pathway–receptor scheme. However, no further details on implementation strategies are provided. In order to support groundwater managers and decision-makers in implementation of programs protecting groundwater, a systematic operational approach based on a decision tree is proposed, which leads the user through the stages of vulnerability assessment. First, a problem has to be formulated related to a threatening of the quantitative and/or qualitative status of a groundwater body. Next, the stated problem needs to be related to the intrinsic or specific vulnerability. Methods used for the intrinsic vulnerability assessment belong to two categories: subjective rating and objective methods. Method selection depends primarily on: data availability, knowledge and available resources. A key issue is the lag time associated with transport between a source/event of contamination and the water body. This lag time is primarily controlled by the temporal scale of water flow. It provides information about flow processes and at the same time also about timescales required for the implementation of strategies. Effects of any measures taken cannot be observed immediately but at the earliest after these estimated lag times emphasizing the need to also proactively safeguard groundwater resources and preserve their good status.