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One pillar of the protection of groundwater established by the EU legislation is the “polluter pays principle”. Following this principle, the costs for the remediation of contaminated sites must be in charge of the responsible of the environmental crime. Compound Specific Isotope Analysis (CSIA), also known as “isotopic fingerprinting”, is a robust tool to apportion the source of groundwater contamination and eventually the polluter. The isotopic composition of the contaminant molecule may reflect the production process of a compound or the origin of the raw materials used in the production. Here we present the effective and decisive application of isotopic fingerprinting of carbon stable isotopes in the molecule of chlorinated hydrocarbons (chlorinated ethenes PCE-Perchloroethylene and TCE-Trichloroethylene) for the source apportionment in two contaminated sites in Italy, namely Ferrara (Emilia-Romagna region, Northern Italy) and Bussi sul Tirino (Abruzzo region, Central Italy). In both cases, industrial wastes from a production of chloromethanes, using methane and chlorine, were disposed illegally in unlined dumps resulting in a severe contamination of groundwater. The companies responsible for the contamination are different in the two sites but the production process is the same, resulting in a similar isotopic signature of the wastes. In both cases, the isotopic fingerprinting was critical to identify the chlorometane production as the source of contamination among other possible sources, despite two different hydrogeological settings (a large alluvial plain in the Ferrara site and a narrow valley with macroclastic alluvial deposits and travertines in the Bussi site). In both cases, PCE and TCE showed strongly depleted values of δ13C (isotopic ratio of the fraction of 13C respect to 12C isotopes of carbon) ranging between -87 and -65‰ for PCE and between -79 and -64‰ for TCE. The very depleted isotopic values are related to the use of methane in the production process instead of coal, this last one being commonly adopted in the synthesis of PCE and TCE for commercial use (e.g. for laundry of textiles or metal degreasing). The groundwater contamination in the two sites had serious implications in terms of sanitary risk due to vapour intrusion into residential buildings (Ferrara site) or water ingestion by local citizens (Bussi site) from a public water supply well field site serving about 300.000 inhabitants and affected for more than 20 years by the contamination (from the opening in 1984 to the decomissioning in 2007). In both cases, complex legal issues arose either below penal or civil jurisdiction and the isotopic fingerprinting was used as the most relevant proof in order to identify the polluters.

It is scientifically established that global warming induced by greenhouse gases, affecting the surface energy budget, can significantly alter the Earth's water cycle, with consequent modification of precipitation typology and regime. However, the net effects of these changes on the process of groundwater discharge are still uncertain at local scale. The lack of historical series of monitoring data, dating back to at least 60-100 years ago, is among the main drawbacks, with the rare exception of major karst springs exploited for public water supply. In hard rock aquifers, like those dominant in the Northern Apennines, the dynamic of spring outflow during the first half of the XX century is an absolute black-box. For this reason, it appeared noteworthy to analyze detailed monthly-based monitoring data, over the 1915-1920 time span, of the whole discharge of the Nadìa spring, one of the most productive spring in the Emilia-Romagna region, in low flow season, among those used for drinking water. Such data were reported in a century-old study functional to the drilling of a draining tunnel for water uptake. We present a comparison between the monthly regime of the spring discharge 100 years ago and a continuous monitoring performed by the authors during the 2020/2021 hydrological year, integrated with the total water uptaken in years 2018-2020. Nadìa spring discharges from an arenitic fractured aquifer deposited in a neritic setting above mainly clayey units acting as a permeability threshold. The abundance of calcite in the grains and cement of the arenite enhances corrosion and enlargement of fractures. In 2018-2021 the spring discharge range has been 80-50 L/s whereas in 1915-1920 it was 140-63 L/s. The two (ancient and recent) sets of data were compared with a focus on the evolution of precipitation, snow-fall and thermal regime.

The Nadìa spring is the second largest tapped spring in the Emilia Romagna Region (northern Italy), representing a strategic local source of drinking water, also in the perspective of future global changes. The spring flowrate ranges between 65 l/s in the recharge season and 45 l/s at the end of the low-flow season, when most of the other tapped springs in the region have flowrates lower than 5 l/s. Geological, geomorphological, hydrological and geochemical investigations were carried out in the spring watershed to unravel the factors causing this peculiarly high discharge. The spring arises at the base of a calcarenitic fractured aquifer (Pantano Formation, upper Burdigalian-lower Langhian) underlain by lower permeability units. Karst dissolution along structural discontinuities in the Pantano Formation has been suggested in the past as a possibility to account for the aquifer high permeability resulting in the high spring discharge. A continuous monitoring of the spring flowrate, temperature, electric conductivity and pH was conducted during the 2020-2021 hydrologic year. Hydrographs and chemographs indicated atypical karst flow dynamics. The time to halve the peak-discharge of the spring is between 20 and 50 days, lower than that of most springs of the Northern Apennines (> 50 days). This implies a higher average aquifer flow rate (around 10 m/day) compared to that typical of arenitic or turbiditic aquifers (around 1 m/day). Spring water samples collected once to twice a year since 2011 for the analysis of major ions revealed an obvious calcium-bicarbonate hydrochemistry that is consistent with the hypothesis of karst dissolution. However, the chemical variability over time expected in a karst system due to the drainage of different groundwater fractions (newly infiltrated vs. older groundwater) was not observed. Instead, the water chemical composition was exceptionally constant over time, suggesting that drainage occurs from a large, homogeneous reservoir. Water stable isotopes have been analyzed in 2021 revealing a composition close to that of the local winter precipitations and suggesting exceptional stability of the spring water composition over different seasons. An 80 m deep borehole has been drilled in the Pantano Formation 7 km away from the spring, documenting the occurrence of fractures with decimetric apertures as deep as 60-70 m below ground surface, which may be interpreted as the result of karst dissolution. In addition to the debatable karst aquifer hypothesis, geomorphological observations indicate the occurrence of depressed areas, of likely tectonic origin, in the aquifer overlying the spring, which may provide a favorable setting for concentrated infiltration and groundwater recharge. However, the hypothesis of concentrated recharge is in apparent contrast to the abovementioned stability of spring water chemical composition over time. A volume of the aquifer representing a reasonable reservoir for the spring has been identified based on spring flow recession analysis and a geo-structural model of the Pantano outcrop up-gradient to the spring. The structural-stratigraphic setting of the hypothesized reservoir includes the occurrence of fault-related fractures that cross-cut the low-dipping bedding of the calcarenites, possibly enhancing the local permeability and the drainage towards the Nadìa spring.

Chlorinated ethene (CE) contaminants are widespread in groundwater, and the occurrence of vinyl chloride (VC), among others, is a well-known issue due to its mobility, persistence, and carcinogenicity. Human exposure to VC may occur through inhalation after soil vapor intrusion into buildings at sites with shallow underground contamination. Soil vapor intrusion risk is traditionally assessed through indoor air and sub-slab sampling (direct evidence) or soil gas and groundwater surveys (indirect evidence). Phytoscreening (sampling and analysis of tree trunk matrices) was proven as a cost-effective alternative technique to indirectly detect shallow underground contamination by higher chlorinated ethenes and subsequent vapor intrusion risk. However, the technique has appeared barely capable to screen for the lower chlorinated VC, likely due to its fugacity and aerobic bio-degradability, with only one literature record to date showing successful detection in trees. We applied phyto-screening at two sites with severe CE contamination nearby residential buildings caused by illegal dumping of chlorinated pitches from petrochemical productions. The two sites show variable amounts of VC in the shallow groundwater (1e2 to 1e4 mu g/L), posing potential sanitary risk issues. Former soil gas surveys did not detect VC in the vadose zone. At both sites, we sampled trunk micro-cores and trunk gas from poplar trees close to contaminated piezometers in different seasons. VC was detected in several instances, disproving the shared literature assumption of the inefficacy of phytoscreening towards this compound. Factors influencing the detectability of VC and other CEs in trees were analyzed through linear regressions. Two different conceptual models were proposed to explain the effective uptake of VC by trees at the two sites, i.e., direct uptake of contaminated groundwater at the first site and uptake of VC from an anoxic vadose zone at the second site. In planta reductive dechlorination of CEs is not expected based on current literature knowledge. Thus, the detection of VC in trunks would indicate its occurrence in the shallow underground, suggesting higher screening effec-tiveness of phytoscreening compared to soil gas; this has implications for indirect vapor intrusion risk assessment.

Applications and acceptance of phytoscreening, i.e., the use of trees as screening tools for underground contamination, are still limited in many countries due to the lack of awareness of application policies, the intrinsic qualitative nature of the technique, and the paucity of critical analyses on available data. To date, the conditions influencing the effectiveness of the technique have been descriptively discussed, yet rarely quantified. This review will contribute to filling this knowledge gap, shedding light on the most suitable approaches to apply phytoscreening. The focus was placed specifically on chlorinated ethene compounds since they are among the main organic contaminants in groundwater and have been the most studied in the field of phytoscreening. Chlorinated ethenes' behavior and biodegradation potential largely depend on their physicochemical properties as well as the hydrogeological features of the system in which they migrate. Besides, their fate and transport in surface ecosystems are still poorly understood. Here, phytoscreening data from sites contaminated by chlorinated ethenes were extracted from relevant literature to form a global-scale database. Data were statistically analyzed to identify the major drivers of variability in tree-cores concentration. Correlation between tree-core and groundwater concentration was quantified through Spearman's rank coefficients, whilst detectability potential was determined based on tree-cores showing non-detection of contaminants. The influence on such parameters of factors like contaminant properties, hydrogeology, tree features, and sampling/analytical protocols was assessed. Results suggest that factors controlling plant uptake and contaminant phytovolatilization regulate correlation and detectability, respectively. Conditions increasing the correlation (e.g., sites with shallow and permeable aquifers) are recommended for phytoscreening applications aimed at mapping and monitoring contaminant plumes, whereas conditions increasing detectability (e.g., sampling tree-cores near ground level) are recommended to preliminary screen underground contamination in poorly investigated areas.

Estimation of aquifer recharge is key to effective groundwater management and protection. In mountain hard-rock aquifers, the average annual discharge of a spring generally reflects the vertical aquifer recharge over the spring catchment. However, the determination of average annual spring discharge requires expensive and challenging field monitoring. A power-law correlation was previously reported in the literature that would allow quantification of the average annual spring discharge starting from only a few discharge measurements in the low-flow season, in a dry summer climate. The correlation is based upon the Maillet model and was previously derived by a 10-year monitoring program of discharge from springs and streams in hard-rock aquifers composed of siliciclastic and calcareous turbidites that did not have well defined hydrogeologic boundaries. In this research, the same correlation was applied to two ophiolitic (peridotitic) hard-rock aquifers in the Northern Apennines (Northern Italy) with well-defined hydrogeologic boundaries and base-outflow springs. The correlation provided a reliable estimate of the average annual spring discharge thus confirming its effectiveness regardless of bedrock lithology. In the two aquifers studied, the measurable annual outputs (i.e. sum of average annual spring discharges) could be assumed equal to the annual inputs (i.e. vertical recharge) based on the clear-cut aquifer boundaries and a quick groundwater circulation inferable from spring water parameters. Thus, in such setting, the aforementioned correlation also provided an estimate of the annual aquifer recharge allowing the assessment of coefficients of infiltration (i.e. ratio between aquifer recharge and total precipitation) ranging between 10 and 20%.

Questo documento presenta le Linee Guida per la gestione sostenibile delle venute d’acqua e del calore geotermico nelle gallerie, elaborate dal Gruppo di Lavoro GESTAG (GEstione SosTenibile delle Acque nelle Gallerie), istituito il 20/06/2012 dal Comitato Italiano dell’Associazione Internazionale degli Idrogeologi. Il documento affronta e descrive obiettivi, metodi e casi di studio, ciascuno dei quali richiede di adottare misure tecniche di vario tipo, illustrate nei capitoli seguenti, come studi idrogeologici, modelli predittivi degli impatti, soluzioni tecnologiche di contenimento del drenaggio e di captazione, recupero e valorizzazione delle risorse intercettate, monitoraggi. Sono affrontati anche i così detti temi non tecnici, come la comunicazione, poiché è ormai noto che l’accettabilità sociale di una galleria influenza direttamente la sua sostenibilità economica e finanziaria, per gli effetti che può avere sui tempi di realizzazione e sui costi delle compensazioni. Sulla base delle diverse esperienze dei componenti del Gruppo di Lavoro GESTAG, si è optato per una suddivisione in 11 temi principali, in particolare, in ciascuno dei capitoli successivi a quello introduttivo vengono trattati rispettivamente: Capitolo 2: l’importanza del ritorno di esperienza proveniente da gallerie già scavate, le banche dati disponibili e i criteri di analisi dei dati pregressi; Capitolo 3: come realizzare lo studio idrogeologico di una galleria, la relazione con il modello geologico, le metodiche da adottare nelle differenti fasi del progetto, che sono state distinte in ante-operam, in corso d’opera e post-operam; Capitolo 4: il tema degli impatti che il drenaggio in galleria può avere sull’ambiente circostante, le analisi che devono essere svolte e gli strumenti da adottare per la gestione del rischio, infine gli interventi per la mitigazione degli impatti; Capitoli 5 e 6: le metodiche di progettazione per la valorizzazione rispettivamente delle acque drenate in galleria e del calore; Capitolo 7: i prodotti chimici che vengono utilizzati in fase di scavo per il sostegno e il miglioramento del terreno, e la loro compatibilità con l’utilizzo delle acque drenate; Capitolo 8: i criteri di monitoraggio delle acque in un progetto di galleria; Capitolo 9: la comunicazione, il rapporto con i territori e l’analisi di casi pregressi, nonché una guida sulle buone pratiche da adottare; Capitolo 10: una panoramica sulla normativa europea ed italiana in tema di valutazione di impatto ambientale, monitoraggio e scarichi delle acque drenate; Capitolo 11: la bibliografia ragionata inerente l’argomento trattato, che include pubblicazioni tecnico scientifiche, normative di riferimento e risorse web.

In an aquifer-aquitard system in the subsoil of the city of Ferrara (Emilia-Romagna region, northern Italy) highly contaminated with chlorinated aliphatic toxic organics such as trichloroethylene (TCE) and tetrachloroethylene (PCE), a strong microbial-dependent dechlorination activity takes place during migration of contaminants through shallow organic-rich layers with peat intercalations. The in situ microbial degradation of chlorinated ethenes, formerly inferredby the utilization of contaminant concentration profiles and Compound-Specific Isotope Analysis (CSIA), was here assessed using Illumina sequencing of V4 hypervariable region of 16S rRNA gene and by clone library analysis of dehalogenase metabolic genes. Taxon-specific investigation of the microbial communities catalyzing the chlorination process revealed the presence of not only dehalogenating genera such as Dehalococcoides and Dehalobacter but also of numerous other groups of non-dehalogenating bacteria and archaea thriving on diverse metabolisms such as hydrolysis and fermentation of complex organic matter, acidogenesis, acetogenesis, and methanogenesis, which can indirectly support the reductive dechlorination process. Besides, the diversity of genes encoding some reductive dehalogenases was also analyzed. Geochemical and 16S rRNA and RDH gene analyses, as a whole, provided insights into the microbial community complexity and the distribution of potential dechlorinators. Based on the data obtained, a possible network of metabolic interactions has been hypothesized to obtain an effective reductive dechlorination process.

The thermal field of Porretta Terme, located in the Alto Reno Terme municipality (Bologna), has always raised interest for its peculiar waters since ancient times. Indeed, the use of the springs dates back to the I-II century A.D. and perhaps even in the Etruscan period. Porretta’s thermal tradition has developed over the centuries. First regulation, issued in 1936, allowed to cultivate the mineral deposit and its natural gas in a 740 000 acres wide land. The thermal waters, a public good, are indeed ruled by specific laws which control their use through a grant where the Public Authority makes the licensee, usually a private, follow a series of accomplishments aimed at not damaging the quantitative and qualitative characteristics (R.D. July 29, 1927 n. 1443). Fourteen thermo-mineral springs out of the nineteen located in the given land are currently exploited. They are divided into two groups, which differentiate either for the chemical properties of the waters and their topographic location. The first group of springs, called salt-bromoiodic, with higher salinity and temperature, is located in the upper part of Porretta along the Rio Maggiore, a tributary on the left bank of the Reno River. This is the portion of the deposit that has been studied. The second group of springs, called sulphurous, characterized by lower temperatures and salinity, is located south-east Porretta on the left side of the Reno River. These thermo-mineral water resources appear to be very worthy and need particular care and protection. By using the results of past research, the essential bibliography of which has been edited in the end-notes, the aim was to develop the hydrogeological parameters of the aquifer that feeds the thermo-mineral sources, identify and understand the conceptual model of the groundwater circulation system, also detecting the interference between the different sources in the area examined. This type of research, which is usually applied to aquifers in sedimentary and granular soils, can be considered original. Indeed, an exhaustive hydrodynamic parameterization of a fractured thermal aquifer system such as that of Porretta has never been conducted. The collection of observational data on the hydrological regime and on the chemical composition of hot waters during the six months of field surveys, which confirmed the substantial constancy of the values over time, was also remarkable.

This essay discusses the need for, advantages and challenges of integrating the scientific disciplines of ecology and hydrogeology in the study of groundwater-dependent ecosystems (GDEs). We provide a definition for ecohydrogeology as “a unifying, synthetic field of study integrating the approaches from the ecological and hydrogeological sciences in the study of groundwater (GW)-related ecosystems, habitats, and organisms to advance science, stewardship, and policy”. We selected specific case studies to illustrate first how hydrogeological approaches can favour in-depth understanding and modelling of springs and crenobiontic (spring-dependent) species distribution, assemblage composition and organization. Second, this essay also examines how taxa and assemblages serve as bioassays and ecosystem indicators to infer hydrogeological aspects of GW flow and discharge, as well as quantitative and qualitative human impacts. We consider both types of features and parameters as ecohydrogeological indicators. The examples presented include topics related to springs and other GDE geomorphological types and classification, GW quality influences on crenobiont distribution, phreatophyte (= plant species the roots of which reach to and into the water table) ecophysiology in relation to water table depth, and flow variability in karstic systems, to nutrient dynamics in relation to dinoflagellate blooms in GDE montane lakes. Conceptual approaches that integrate ecology with hydrogeology include the investigation of GDE distribution and ecology, groundwater-surface water (GW-SW) interactions, and the development of the discipline of ecohydrology. Despite widespread applications, the scientific community still lacks a complete or effective integration of the principles described in the fields of groundwater hydrogeology with ecology, ecophysiology, and environmental biology. Springs are aquatic-wetland-riparian habitats that link shallow subsurface-surface processes and assemblages, often functioning as biodiversity hotspots, ecotones, keystone, and refugial ecosystems, for which coordination between studies of hydrogeology and ecology are both obvious and essential. Over the past century, springs ecosystem ecology has been largely ignored by hydrologists, and, conversely, hydrogeology has been under-emphasized by ecologists. Recent global recognition of the extraordinary biodiversity and socio-cultural significance of springs, coupled with their globally highly threatened conservation status, stimulated this inquiry into how to better integrate hydrogeology with springs ecosystem ecology. Acknowledging the highly threatened status of springs ecosystems around the world, there is an urgent need to integrate and invigorate the union of these disciplines into ecohydrogeology, the study of groundwater-dependent organisms, habitats, ecosystems, and management policy.

This study investigates for the first time the integrity of multiple stacked aquitards with different degrees of contaminant degradation. Aquitard integrity was assessed in a contaminated, multi-layered, alluvial aquifer-aquitard system (Ferrara, northern Italy). The system was contaminated by mixed organic contaminants of industrial origin (mostly chlorinated ethenes) that were illegally disposed in an urban dump four to five decades ago. High spatial resolution profiles of hydraulic head, geochemistry and chlorinated hydrocarbon concentrations were determined through the multi-layered system via discrete interval sampling of continuous cores and multilevel groundwater sampling, at three locations aligned along a transect adjacent to the buried waste to a maximum depth of 53 m below the water table. The profiles revealed that the two shallow aquitards had low integrity with respect to impeding downward migration of dense non-aqueous phase liquid (DNAPL), and provided little protection to the underlying aquifers against DNAPL contamination due to preferential pathways through imperceptible fractures and/or permeable micro-beds. However, both aquitards inhibited downward DNAPL migration to some extent due to DNAPL retention along its flow paths and accumulation at lower permeability interfaces, with decreasing peak concentrations at the top of successively deeper aquitard units. Moreover, both aquitards enhanced contaminant biodegradation due to the occurrence of organic rich sub-layers, influencing the contaminant plume composition, mobility and fate in the underlying and overlying aquifers. The deepest aquitard showed evidence of DNAPL accumulation at the top and slow diffusion-dominated transport consistent with 40 years of transport, suggesting higher integrity compared to the two shallower aquitards. However, the occurrence of micro-fractures and/or discontinuities in the aquitard upgradient under the dump (source) is the most likely explanation for contamination of the deepest aquifer. Analytical 1-D simulations of the diffusion profiles in the deepest aquitard revealed that DNAPL contamination down to the top of this aquitard occurred with minimal delay after DNAPL waste disposal began. The results highlight the necessity of high-resolution vertical profiling for assessing the presence of imperceptible features relevant to DNAPL migration and integrity of individual aquitards affecting organic contaminant source zone mass and phase distributions over decades.

A few hydrogeological studies have been carried out worldwide in peridotite aquifer systems, despite their wide distribution. The ophiolites are one of the main groundwater reservoir within the northern Apennines (Italy). This paper suggests the graphical solution to set the hydrogeological map of heterogeneous, multi-layered ophiolitic aquifers mapped on large scale (1:1600). The site investigation area is an ophiolite outcrop of the External Ligurian of the northern Apennines: the Mountain Prinzera rock complex area (44°38′30′′N, 10°5′E; Parma Province, Emilia-Romagna Region). The hydrogeological characteristics of the tested aquifer system do not allow setting a hydrogeological map by applying usual graphical approaches. The hydrogeological map in such complex aquifer systems will show the classic hydrogeological data but must put in evidence above all (i) the main heterogeneities of the system, from the hydraulic point of view and (ii) the modifications of groundwater scenarios and pathways over time. The hydrogeological database of Mt Prinzera aquifer was managed in ESRI ArcGIS 10.0 software.

Hard rock aquifers (or discontinuous aquifers) are commonly intended as igneous or metamorphic rocks with very low primary porosity and a significant however discontinuous and strongly anisotropic secondary porosity (i.e. fractures) due to tectonic stresses and weathering. In some cases, the term “hard rock aquifer” is well suited also for sedimentary fractured rocks. This is the case of the turbiditic formations in the Northern Apennines (Italy), that represent the most valuable groundwater reservoir in the region. In such cases, the quantification of water resources hosted in the hard rock aquifers becomes of paramount importance. We propose a method to quantify the effective recharge occurring within a spring recharge area in a hard rock aquifer setting when only spring discharge monitoring during the low flow season (summer) is available. An empirical relationship was found between the average annual discharge of a spring and its average summer discharge, starting from a large database of 11 hydrologic years of discharge monitoring on more than 80 springs. Such relationship is linear on a log-log scale and changes according to the Maillet’s recession coefficient. The average annual flow rate obtained from summer monitoring data (i.e. the average summer discharge and the Maillet coefficient) is considered as a proxy of the effective recharge occurring within the spring recharge area. The proposed method was tested both in turbiditic and ophiolitic hard rock aquifers in the Northern Apennines in different hydrologic years, providing an overall accuracy in the range of ±15% with respect to the actual annual average spring discharges. Thus, this is a promising tool to support the application of hydrologic balances in hard rock aquifers. However, further tests should be carried out in different hard rock aquifer settings in order to form a basis for more realistic expectations about the overall validity of the method.

International audience; Tetrachloroethene and trichloroethene are typical by-products of the industrial production of chloromethanes. These by-products are known as "chlorinated pitches" and were often dumped in un-contained waste disposal sites causing groundwater contaminations. Previous research showed that a strongly depleted stable carbon isotope signature characterizes chlorinated compounds associated with chlorinated pitches whereas manufactured commercial compounds have more enriched carbon isotope ratios. The findings were restricted to a single case study and one element (i.e. carbon). This paper presents a multi-element Compound-Specific Stable Isotope Analysis (CSIA, including carbon, chlorine and hydrogen) of chlorinated aliphatic contaminants originated from chlorinated pitches at two sites with different hydrogeology and different producers of chloromethanes. The results show strongly depleted carbon signatures at both sites whereas the chlorine and the hydrogen signatures are comparable to those presented in the literature for manufactured commercial compounds. Multi-element CSIA allowed the identification of sources and site-specific processes affecting chloroethene transformation in groundwater as a result of emergency remediation measures. CSIA turned out to be an effective forensic tool to address the liability for the contamination, leading to a conviction for the crimes of unintentional aggravated public water supply poisoning and environmental disaster.

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 50 years 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 (b−60‰) suggesting production lines which have used depleted methane for synthesis. The other source had typical carbon isotope compositions of N−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.

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.

Water inflows are a major challenge in tunnelling and particularly difficult to predict in geological settings consisting of heterogeneous sedimentary rock formations with complex tectonic structure. For a high-speed railway line between Bologna and Florence (Italy), a series of seven railway tunnels was drilled through turbiditic formations, ranging from pelitic rocks with thin arenitic layers over sequences including thick-bedded sandstone to calcareous rocks showing chemical dissolution phenomena (karstification). The tunnels were built as draining tunnels and caused significant impacts, such as drying of springs and base-flow losses at mountain streams. A comprehensive hydrological monitoring programme and four multi-tracer test were done, focusing on four sections of the tunnel system. The tracer tests delivered unprecedented data on groundwater flow and transport in turbiditic aquifers and made it possible to better characterize the differential impacts of tunnel drainage along a geological gradient. The impact radius is 200 m in the thin-bedded sequences but reaches 2.3-4.0 km in calcareous and thick-bedded arenitic turbidites. Linear flow velocities, as determined from the peaks of the tracer breakthrough curves, range from 3.6 m/day in the thin-bedded turbidites to 39 m/day in the calcareous rocks (average values from the four test sites). At several places, discrete fault zones were identified as main hydraulic pathways between impacted streams and draining tunnels. This case shows that ignoring the hydrogeological conditions in construction projects can cause terrible damage, and the study presents an approach to better predict hydraulic impacts of draining tunnels in complex sedimentary rock settings.

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 Ca2 + 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.

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.

The occurrence of vinyl chloride (VC) is often a main concern at sites contaminated with chlorinated solvents due to its high degree of toxicity and carcinogenicity. VC occurrence in aquifers is most often related to the degradation of higher chlorinated ethenes or ethanes and it is generally detected in plumes along with parent contaminants. However, specific combination of stratigraphic, hydrogeologic and geochemical conditions can enhance the degradation of parents and lead to the formation of plumes almost entirely composed of VC (i.e. VC-only plumes). This paper investigates the causes of VC-only plumes in the aquifers below the city of Ferrara (northern Italy) by combining multiple lines of evidence. The City of Ferrara is located on an alluvial lowland, built by the River Po, and is made up of alternating unconsolidated sandy aquifer and silt-clay aquitard deposits of fluvial origin. This region has been strongly impacted by prior industrial activities, with the occurrence of chlorinated compounds at several sites. VC-only plumes with uncertain source location were found at two contaminated sites. The source zone of a third plume composed of chloroethenes from PCE to VC was investigated for high resolution depositional facies architecture and contaminant distribution (contaminant concentration and Compound Specific Isotope Analysis – CSIA). The investigation suggested that degradation of PCE and TCE takes place during contaminant migration through peat-rich (swamp) layers related to the Holocene transgression, which locally act as a “reactor” for stimulating degradation with the accumulation of VC in the strongly reducing environment of the peat. Regional-scale stratigraphic architecture showed the ubiquitous occurrence of swamp layers at distinct stratigraphic levels in the investigated system and their apparent linkage to the in situ creation of the VC-only plumes.

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.

We examined how hydrology influenced water chemistry, vegetation, nutrient status, aboveground net primary production (ANPP) and litter decomposition rates in two peatlands on the South-Eastern Alps of Italy. One of the peatlands had a modest hydraulic gradient and prevalently acted as a recharge system, although there were short phases of vertical flow reversal during dry periods. This peatland was, therefore, prevalently fed by rainwater and was covered by bog-like vegetation, mainly hummocks and scrubs with a ground layer rich in Sphagnum mosses. The other peatland presented a steeper hydraulic gradient, with the surface being fed by mineral water either by surface runoff and by vertical, upwards directed ground-water flow. Compared to the bog-dominated peatland, the pore water was less acidic and richer in telluric cations. More than half of the peatland surface was covered by fen meadows. Nitrogen (N) content in the vegetation was very similar in the two peatlands, while phosphorus (P) concentration was lower in the fen-dominated site. Contrary to our expectations, ANPP did not differ significantly between the two sites while litter decomposition rates were significantly lower in the fen-dominated peatland, presumably because of P limitation of decomposers. This suggests that the development of ombrogenous peatlands in this region need not be due to increased accumulation of peat during succession from mineralwater-fed to rainwater-fed conditions.

Summary A multi-layered aquifer system (eastern Po plain, northern Italy) was investigated by means of isotopic data, with the goal of quantifying groundwater recharge from different sources and assessing the intrinsic vulnerability of aquifers to surface sources of contamination. The geology of the area is based on a stratigraphic alternation of several sandy aquifers and silty–clayey aquitards, down to a maximum depth of 200 m b.g.s. Water isotopes (δ 18 O, δ 2 H), and hydrochemical analyses were performed on groundwater samples collected from a regional network of 70 boreholes distributed on an area of almost 2000 km 2 . In addition to the regional sampling, detailed vertical isotopic profiling was performed in one location by means of groundwater and sediment samples collected through the whole sequence of aquifers and aquitards. Water isotopes indicated mixing from different sources of recharge (i.e., vertical recharge, Po river, deeper aquifers). Mixing calculations were used to quantify the contributions to the aquifers from the different sources. The vertical profiling allowed for integrating and validating the interpretations at a regional scale. The recharge pattern defined for the different aquifers was translated into an index of hydrogeologic interconnections with the surface, which represents a physically based proxy of the intrinsic vulnerability of the aquifers to surficial sources of contamination. The investigated setting can be considered to be representative of many other anthropized and groundwater demanding plain settings around the world. Thus, the proposed method represents a valuable approach for such settings both for recharge quantification (e.g., to be used as input for numerical modeling) and for a physically based assessment of the intrinsic vulnerability.

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.

In Northern Apennines, landslides involving weak rocks such as clay shales are widespread and often cause damage to public infrastructure and private properties. These landslides, mostly classifiable as earthflows, generally exhibit continuous slow movements, with temporary increases of velocity controlled both by groundwater and rainfall regime. Although the relationship between precipitation, groundwater flow and displacement rate is evident, its quantitative description remains problematic. We use piezometric and slope movement continuous monitoring to investigate the groundwater flow system in the vicinity of the contact between clay shales and overlying more permeable units, where the village of Lizzano in Belvedere is located. Our aim is to describe the groundwater flow and its relation to slope deformation in order to simulate the effect of possible drainage measures both on piezometric levels and expected displacement rates. Timing and magnitude of piezometric responses at different depths are related to observed deformations and used to calibrate a transient 3D groundwater flow model. Groundwater modeling validates the conceptual hydrogeological scheme and allows simulation of the impact of surface and deep drainages on piezometric levels. Results indicate that horizontal drains are more effective than infiltration reduction measures, both in terms of drawdown and time effectiveness of action. Simulated hydraulic heads are then used to produce a probabilistic prediction of the expected displacement rates by means of an empirical method. In the case of Lizzano in Belvedere, according to our results, the lowering of hydraulic heads operated by horizontal drains can reduce the velocity of slope movements from centimeters per year to millimeters per year.

A modelling study on a multi-layered confined/unconfined alluvial aquifer system was performed to quantify surface water/groundwater interactions. The calibrated groundwater flow model was used to forecast climate change impacts by implementing the results of a downscaled A1B model ensemble for the Po river valley. The modelled area is located in the north-western portion of the Ferrara Province (Northern Italy), along the eastern bank of the Po river. The modelling procedure started with a large scale steady state model followed by a transient flow model for the central portion of the domain, where a telescopic mesh refinement was applied. The calibration performance of both models was satisfactory, in both drought and flooding conditions. Subsequently, forecasted rainfall, evapotranspiration and Po river stage at 2050, were implemented in the calibrated large scale groundwater flow model and their uncertainties discussed. Three scenarios were run on the large scale model: the first simulating mean hydrological conditions and the other two simulating one standard deviation above and below the mean hydrological conditions. The forecasted variations in groundwater/Po river fluxes are relevant, with a general increase of groundwater levels due to local conditions, although there are large uncertainties in the predicted variables.

To investigate the role of pore water pressures in the stability of a streambank, a series of tensiometers and piezometers was installed in a bank of the Sieve River, Tuscany, Italy. Fluvial entrainment at the bank toe was monitored by repeated cross-profiling, erosion pins and marked pebbles. Fluctuations in matric suction measured at the tensiometers reflected the overall response of pore water pressures to rainfall, evapotranspiration, rising and drawdown of the river stage, and variations in water table. An expression was derived for the safety factor with respect to mass movement of the upper bank, incorporating the failure criterion for unsaturated soils and the normal Mohr–Coulomb criterion for saturated conditions. Variations in matric suction have important effects on the stability of the streambank. During low-flow periods, the shear strength term due to the matric suction allows the bank to remain stable at a steep angle. However, during rainfall and flow events, reduction in matric suction and increase in unit weight of the material from vertical and lateral infiltration may be sufficient to trigger a mass failure, without development of significant positive pore water pressures. During the rising limb of high-flow events, the factor of safety increases as a consequence of the stabilizing confining pressure of the water in the river, despite a reduction in matric suction. During drawdown in the river, when the suction values are still low and the confining pressure in the river decreases to zero, the factor of safety falls to lower values than those experienced prior to the runoff event. Measurements of fluvial entrainment reveal that, although the processes, mechanisms and the frequency of retreat of basal and upper bank zones differ significantly, the amount of retreat at the bank toe due to fluvial erosion is comparable to that of the upper portion of the bank due to mass failure. Copyright © 1999 John Wiley & Sons, Ltd.

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.

This case study deals with a severe groundwater contamination by chlorinated ethenes and ethanes beneath the urbanized area of via Caretti, immediately to the east of the ancient historical center of the city of Ferrara (Emilia-Romagna region, northern Italy). Based on the concentrations as measured in the groundwater and conventional risk modeling, the contamination potentially poses a serious threat to on-site receptors (inhabitants) by indoor and outdoor vapor inhalation. The sources of contamination are two unlined waste dumps located inside abandoned clay quarries and filled, during the 1960’s-70’s, by a mixture of urban solid wastes and chlorinated pitches originated from the chloromethanes distillation process of nearby petrochemical plants. The area is located in the eastern and lowest sector of the Padana plain, a few kilometers southward of the Po river. The underground stratigraphy consists of alternating alluvial sand and silty-clayey layers that form a multi-aquifer system with alternance of three sandy permeable layers, down to about 50 m depth below ground level (b.g.l.), with low permeability aquitards. Contaminants occurrence in the aquifers, soil gas and indoor air were determined by a multi-step investigation approach based upon state of the art techniques. Contaminant plumes of mainly vinyl chloride (VC) occur in the two shallowest aquifers and have migrated up to a maximum distance of 500 m from the source below the houses of via Caretti. VC concentrations in the first aquifer attain a peak of about 1x103 μg/L (with a maximum value at the source of more than 2x104 μg/L); concentrations of about one order of magnitude higher were detected in the upper confined aquifer with an absolute peak of more than 1x105 μg/L. In addition high concentrations of perchloroethene (PCE), trichloroethene (TCE), dichloroethene DCE (1,1 and cis-1,2), 1,1,2,2-TeCA (tetrachloroethane) and chloromethanes were detected in both aquifers. Indoor air measurements were performed by means of sorption tubes by combining active and passive techniques, in two different sampling campaigns in the ground floor and the first floor of the buildings. Seasonal measurements of groundwater concentrations were also performed at four piezometers located in close proximity to the houses. Two different analytical models for risk assessment (Tier II) were applied with available site-specific data to predict indoor air concentrations and estimate risks for adult and children as receptors. In contrast to such severe concentrations in groundwater and to results of Tier II human health risk assessment based on analytical models, low and spotty evidence of contaminated vapors was found either in soil or in indoor gas and no direct relationship with subsoil conditions resulted. The occurrence of fine grained sediments (clays and silts) over the shallowest aquifer appears to block vapor intrusion and protect the residents from direct exposure by inhalation. Alternatively, biodegradation processes occurring at the interface between the saturated and the (oxygen rich) unsaturated zone may be capable of reducing the fluxes of contaminant that could potentially reach receptors. Detailed process and modeling studies are needed to elucidate these phenomena and improve site investigation tools and risk models.

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 site's conceptual model. © 2008 Elsevier B.V. All rights reserved.

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.

Turbidites crop out extensively in the Northern Apennine mountains (Italy). The huge amounts of groundwater drained by tunnels, built for the high speed railway connection between Bologna and Florence, demonstrate the aquifer-like behaviour of these units, up to now considered as aquitards. A conceptual model of groundwater flow systems (GFS) in fractured aquifers of turbidites is proposed, taking into account both system natural state and the perturbation induced by tunnel drainage. Analysis of hydrological data (springs, streams and tunnel discharge), collected over 10 years, was integrated with analysis of hydrochemical and isotopic data and a stream-tunnel tracer test. Hydrologic recession analysis of undisturbed conditions is a key tool in studying turbiditic aquifer hydrogeology, permitting the discrimination of GFS, the estimation of recharge relative to the upstream reach portion and the identification of springs most vulnerable to tunnel drainage impacts. The groundwater budgeting analysis provides evidence that the natural aquifer discharge was stream-focused through GFS, developed downslope or connected to main extensional tectonic lineaments intersecting stream beds; now tunnels drain mainly active recharge groundwater and so cause a relevant stream baseflow deplenishment (approximately two-thirds of the natural value), possibly resulting in adverse effects on local ecosystems.

Vinyl chloride (VC) groundwater contamination around the city of Ferrara, Italy, is rather widespread and has created a serious environmental problem in this highly urbanized region. The paper discusses recent data derived from a geochemical and isotopic fingerprinting study carried out at the Pandora site, which is characterized by the existence of a long VC plume, and at the Caretti site where high concentrations of chlorinated compounds, including VC, occur. Data was also collected at an unconfined aquifer under¬neath a major petrochemical plant. The isotopes data show that the unusual negative δ13C values observed in the VC at both sites (Pandora –43 and –65‰; Caretti: –62 and –72‰) could not be attributed to reductive dechlorination of manufactured primary PCE or TCE. Unusual negative δ13C values for PCE and TCE also characterise the impacted aquifer beneath the petrochemical plant and the Caretti site. Based on the industrial history of the region, which includes production of PVC and chloromethanes (ClM), it is postulated that contamination in the Ferrara region is linked to wastes originating from the production of chloromethanes. The primary organic compound used in ClM production is methane, which is strongly depleted in 13C similar to the values observed in VC, PCE and TCE at the investigated sites. It is also postulated that the contamination is linked to dumping of industrial waste in the abandoned lagoons used by the sugar industry and in clay pits associated with the clay industry.

The paper deals with a sandy confined aquifer of alluvial origin contaminated by vinyl chloride and located in the Po Valley immediately to the south of the Po River and 5 km to the north of the city of Ferrara (northern Italy). The investigation identified, inside a mainly urbanized area, a plume with a length of 1.7 km and a maximum width of 0.3 km with vinyl chloride (VC) concentrations of up to more than 11 000 ppb and total absence of other chlorinated ethanes, ethenes, and ethylene. To optimize the VC analysis, short-term low-flow purging using peristaltic and inertial pumps were used to collect samples.

Pore water pressures (positive and negative) were monitored for four years (1996–1999) using a series of tensiometerpiezometers at increasing depths in a riverbank of the Sieve River, Tuscany (central Italy), with the overall objective of investigating pore pressure changes in response to flow events and their effects on bank stability. The saturated/unsaturated flow was modelled using a finite element seepage analysis, for the main flow events occurring during the four-year monitoring period. Modelling results were validated by comparing measured with computed pore water pressure values for a series of representative events. Riverbank stability analysis was conducted by applying the limit equilibrium method (Morgenstern-Price), using pore water pressure distributions obtained by the seepage analysis. The simulation of the 14 December 1996 event, during which a bank failure occurred, is reported in detail to illustrate the relations between the water table and river stage during the various phases of the hydrograph and their effects on bank stability. The simulation, according to monitored data, shows that the failure occurred three hours after the peak stage, during the inversion of flow (from the bank towards the river). A relatively limited development of positive pore pressures, reducing the effective stress and annulling the shear strength term due to the matric suction, and the sudden loss of the confining pressure of the river during the initial drawdown were responsible for triggering the mass failure. Results deriving from the seepage and stability analysis of nine selected flow events were then used to investigate the role of the flow event characteristics (in terms of peak stages and hydrograph characteristics) and of changes in bank geometry. Besides the peak river stage, which mainly controls the occurrence of conditions of instability, an important role is played by the hydrograph characteristics, in particular by the presence of one or more minor peaks in the river stage preceding the main one. Copyright © 2004 John Wiley & Sons, Ltd.