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The F'Kirina plain in eastern Algeria is an endorheic basin suffering water scarcity due to a combination of natural and man-made causes. Its hydrogeological system is complex as made by interconnected aquifers represented by Mesozoic, Cenozoic, and Quaternary lithological units. The combination of drought indicators and water level data shows that a groundwater drought affected the plain during the last 15 years, which reflects on current water quality. The reported geochemical analyses, including major ions and trace elements, indicate that the groundwater resource is suffering from salinization, mainly due to evaporation and leaching of soil salts, a process that is coupled with simultaneous cation-exchange effects. In this framework, we observe a geochemical evolution from the fresh Ca–HCO3 facies, typical of springs bordering the plain, towards more saline groundwater characterized by chloride/sulphate-rich facies in the middle of the plain approaching the sebka. However, geochemical diagrams indicate that in few wells salinization is also influenced by upraising of deep groundwater. The water isotopic composition of the F'Kirina plain samples suggests that they diversely record both recharge and evaporation components. Moreover, the most 18O and D depleted compositions among the investigated ground-waters suggest recharge contributions by comparatively higher elevation or the involvement of old (fossil) water components.

The water composition of the river Adige displays a Ca&ndash, HCO3 hydrochemical facies, mainly due to rock weathering. Nitrate is the only component that has increased in relation to growing anthropogenic inputs. The aim of this paper was to identify the origin of the dissolved components in this river and to establish the relationship between these components and critical zone processes within an evolving framework where climatic and human impacts are influencing the riverine system. In particular, emphasis is given to a wide spectrum of isotope data (&delta, 18O, &delta, 2H, &delta, 13C, &delta, 15N, &delta, 34S, 87Sr/86Sr, &delta, 11B), which is considered useful for determining water origin as well as natural and anthropogenic impacts on riverine geochemistry. Together with oxygen and hydrogen isotopes, which are strictly related to the climatic conditions (precipitation, temperature, humidity), the carbon, sulphur, strontium and boron signatures can describe the magnitude of rock weathering, which is in turn linked to the climatic parameters. &delta, 13CDIC varies regularly along the riverine profile between &minus, 4.5&permil, and &minus, 9.5&permil, and &delta, 34SSO4 varies regularly between +4.4&permil, and +11.4&permil, On the other hand, &delta, 15NNO3 shows a more scattered distribution between +3.9&permil, and +10.5&permil, with sharp variations along the riverine profile. 87Sr/86Sr varies between 0.72797 in the upper part of the catchment and 0.71068 in the lower part. &delta, 11B also shows a rough trend, with values approaching 7.6&permil, in the upper part and 8.5&permil, in the lower part. In our view, the comparatively low &delta, 34S, &delta, 11B, and high 87Sr/86Sr values, could be a proxy for increasing silicate weathering, which is a process that is sensitive to increases in temperature.

In the Main Ethiopian Rift (MER) area, rural populations often use water that exceeds the World Health Organization thresholds for fluoride (F&ndash, ) and arsenic (As), two elements that are hazardous for human health. In this study, twenty-nine water samples were collected from lakes and hot and cold springs in southern MER to investigate source(s) and health-risk of the F&ndash, and As contamination. According to major ion and trace element analyses, only cold spring water is safe for consumption, whereas hot spring water is the most contaminated. Leaching tests performed with the MER rhyolitic volcanic rocks and their weathered products (fluvio-lacustrine sediments) demonstrate that the main cause of the F&ndash, and As release is geogenic, i.e., not related to anthropogenic activities. The weathering of volcanic glass and minerals (apatites, clays, hydro-oxides) by CO2-bearing alkaline water induces the mobilisation of F&ndash, and As from solid to liquid phase. This process is particularly fast, when fluvio-lacustrine sediments are involved, and can be further enhanced by hot groundwater leaching. This study, investigating the distribution, sources, and mechanisms of F&ndash, and As release in MER water, could be of interest also for other sectors of the East African Rift and other similar volcano-tectonic settings.

The Sacca di Goro and Sacca di Scardovari are two coastal lagoons of the Po River delta facing the northern Adriatic Sea. They are sensitive ecosystems both from the naturalistic and socio-economic point of view, since they are included in a natural park and are high productivity shellfish sites. Bottom sediments from the two lagoons have been analysed for their textural and geochemical (major and trace elements by XRF) composition in order to identify natural backgrounds and anthropogenic inputs. OC, N and δ13COC data have been also carried out by EA-IRMS to highlight the association of heavy metals with inorganic or organic sedimentary components. Results show that abundances of siderophile (Cr, Ni, Co) heavy metals in samples from the two lagoons are generally in the range of those recorded in alluvial sediments from the neighbours and are associated with the finest (clayey) fraction. Among chalcophile heavy metals, Pb and Zn display significant enrichments relative to the local geochemical backgrounds suggesting anthropogenic sources. They appear to be preferentially associated with the sedimentary organic matter that, according to the isotopic composition, is mainly formed by the incorporation of different proportions of macroalgae and macrophytes that have a significant bioaccumulation capacity. Taking into consideration that the extent of the algal biomass is sensitive to anthropogenic pressure and climatic changes, the trace element budget of sediments from these lagoons has to be monitored in the future, also to assess the impact of heavy metals on shellfish production.

The presented research highlights relationships between the climatic anomalies that occurred in northern Italy in 2015 and the water system of Po river. We investigated the effect of anomalous high temperature and paucity of meteoric precipitation on the Po river discharge and water geochemistry. The new geochemical data, carried out on river water sampled at Pontelagoscuro (close to the city of Ferrara) and in the delta, have been compared with an extended dataset collected since 2009. The comparison emphasizes that water samples of 2015 were characterized by a high electrical conductivity due to high concentrations of conservative ionic species (e.g. Na, Cl, SO4) and nutrients such as nitrate. Oxygen and hydrogen isotopes, particularly sensitive to the observed climatic changes, reveal in a δ18O-δD diagram evaporative trends (highlighted by displacement from the Meteoric Water Lines) with a magnitude that was not recorded in the last years. The monitoring is currently in progress to develop functions that relate geochemical parameters to the evolving meteo-hydrological conditions.

Glaciers are shrinking due to global warming, resulting in a diminishing contribution of ice and snowmelt to headwaters and subsequent consequences to freshwater ecosystems. Within this context, we tested whether water-stable isotopes are spatio-temporal tracers of (i) water in high altitude periglacial environments, being the isotopic signature of surface water inherited from the snow/icemelt, groundwater, and rainfall, and (ii) regional (year-specific) meteorological conditions, being the isotopic signature of precipitations affected by air temperature, humidity and aqueous vapour origin, ascribing stable isotopes to the list of &ldquo, essential climate variables&Prime, (ECVs). To this end, we investigated the ionic and isotopic composition (18O and 2H) of six high-altitude streams and one pond in the Italian Alps (Noce and Sarca basins) during the ablation season in 2018. Differences between habitat types (pond, kryal, rhithral, krenal) were detected. More negative values of 18O and 2H were recorded in the kryal and glacio-rhithral sites, dominated by ice and snowmelt, in early summer. Less negative values were recorded in these sites in late summer, as well as in the krenal sites, which were dominated by groundwater and rainfall inputs. The isotopic results also show that the complex alpine orography influences air masses and moisture, ultimately resulting in isotopic differences in the precipitations of neighboring but distinct catchments (Sarca and Noce basins). On average, less negative values were recorded in the Sarca basin, characterized by a higher contribution of precipitation of Mediterranean origin. In general, isotopic results of the entire water population appeared to be strongly influenced by the regional climatic anomaly of 2018, which was anomalously warm. Therefore, the study will provide additional information for the climate change debate, proposing water isotopes as ECVs for assessing change in a warmer future.

Strontium isotopic composition (Sr-87/Sr-86) of river water provides insight on the nature of rocks involved in the weathering processes and important constraints for reconstructing silicate versus carbonate weathering in large scale basins. New data, presented in the context of a geochemical map of the Po river basin, highlight that the Po river water evolves from the upper part of the catchment, where Sr-87/Sr-86 approaching 0.7097 relates to the weathering of igneous and metamorphic silicate rocks, to the middle part, where less radiogenic compositions (Sr-87/Sr-86 similar to 0.7089) are driven by the confluence of the tributaries draining Mesozoic carbonate rocks of the South Alpine domain and from inflow of Apennine streams characterized by less radiogenic Sr signatures due to weathering of marly sediments and mafic magmatic rocks. Down flow, the Sr isotopic compositions of Po river water rises at 0.7091 either by the confluence of the last Apennine tributary (Panaro, Sr-87/Sr-86 similar to 0.7095) and/or by the possible contribution from hyporheic exchanges. Po river isotopic signatures reveal slightly more radiogenic Sr-87/Sr-86 in comparison to other important Alpine river systems (e.g. Danube, Rhine and Rhone), likely suggesting that silicate rocks are comparatively contributing more weathering byproducts in the Po basin.

article i nfo Article history: Detailed petrological and geochemical investigations of an extensive sampling of mantle xenoliths from the Neogene-Quaternary Bir Ali diatreme (southern Yemen) indicate that the underlying lithospheric mantle consists predominantly of medium- to fine-grained (often foliated) spinel-peridotites (85-90%) and spinel-pyroxenites (10-15%) showing thermobarometric estimates in the P- Tr ange of 0.9-2.0 GPa and 900-1150 °C. Peridotites, including lherzolites, harzburgites and dunites delineate continuous chemical, modal and mineralogical variations compatible with large extractions of basic melts occurring since the late Proterozoic (~2 Ga, according to Lu-Hf model ages). Pyroxenites may represent intrusions of subalkaline basic melts interacting and equilibrated with the host peridotite. Subsequent metasomatism has led to modal changes, with evidence of reaction patches and clinopyroxene and spinel destabilization, as well as formation of new phases (glass, amphibole and feldspar). These changes are accompanied by enrichment of the most incompatible elements and isotopic compositions. 143 Nd/ 144 Nd ranges from 0.51419 to 0.51209 (eNd from +30.3 to �10.5), 176 Hf/ 177 Hf from 0.28459 to 0.28239 (eHf from +64.4 to

The deep seated xenolith association exhumed in the Pliocenic volcano of Tallante (Betic Cordillera, Spain) includes protogranular mantle peridotites, felsic (metasedimentary) crustal rocks, as well as cumulus igneous rocks such as norites and amphibole (+/- phlogopite)-clinopyroxenites. The whole xenolith suite equilibrated at the same pressure (0.7-0.9 GPa) representing the local crust-mantle boundary (MOHO) characterized by extreme lithological heterogeneity. This heterogeneity resulted from orogenic processes that induced the juxtaposition of crustal rocks (variably depleted in fusible components) within mantle domains including metasomes, as it is commonly observed in orogenic mantle massifs of the Mediterranean area. In this contribution, we report new mineral compositions of igneous parageneses recorded in these xenoliths, and we present Sr-Nd isotope data on both igneous and metasedimentary xenoliths that integrate those from the literature. Sr-Nd isotopes coherently indicate a restitic character of the metasedimentary xenoliths, which according to model ages were affected by partial melting in Paleozoic times. Sr-Nd isotopic errorchrons on the igneous xenoliths, on the other hand, qualitatively indicate Tertiary ages, which are corroborated by U-Pb zircon datings of one norite xenolith and two composite xenoliths having zircon-bearing norite veinlets. The new data are discussed proposing that MOHO lithologies of Tallante could provide significant source compositions for the genesis of the Neogene volcanics of the Betic area, which included calcalkaline lavas as well as more potassic products such as lamproites. (C) 2015 Elsevier B.V. All rights reserved.

Po River Delta is situated in the Padania Plain at the confluence with the Adriatic Sea. Since the second half of the nineteenth century, human activities have been focused on the reclamation of wetlands, in order to use them for agricultural purposes. Nowadays these reclaimed soils are mainly used to cultivate cereals and horticultural crops. The mail problem related to this kind of soils is their capability to retain heavy metals. These can be transferred to the cultivations and to the humans, being in some cases very dangerous. It is therefore fundamental to investigate the amount of heavy metals present in reclaimed soils and that which could be transferred to the plants. With this aim, a reclaimed soil that has been used for sorghum cultivation was chosen as test field. Heavy metal concentrations of the soil, the rhizosphere and the seeds, as well as the roots and some aerial parts of the sampled sorghum were measured, respectively. High Cr and Ni concentrations were detected in the soil and rhizosphere samples, related to their natural availability due to the presence of chlorite and serpentine in these soils. On the contrary in the seeds, micronutrients such as Zn and Cu have higher concentrations with respect to Cr and Ni, but all the metals (except Cd) are below the national admitted limits. Metals classified as non-essential for humans (As, Cd, Cr, Ni) are scarcely absorbed by the plant, and their average concentrations decreased according to this pathway: soil > rhizosphere > root > aerial parts > seed. Cd, Zn and As are richer in the rhizosphere with respect to the bulk soil. © 2017, Springer-Verlag GmbH Germany., This work has been supported by EC LIFE+ funding to ZeoLIFE project (LIFE + 10 ENV/IT/000321).

This paper demonstrates that geochemistry is useful for the identification of sediment origin and provenance in alluvial plains characterised by a complex hydrographic evolution. The study is focused on the northeastern Padanian plain (Italy), an area primarily characterised by sedimentary contributions from the two largest Italian river systems (Po and Adige), which intimately interacted during the last millennia. X-ray fluorescence analyses of 120 soils and alluvial sediments define three diverse geochemical affinities that have distinctive siderophile/chalcophile elemental ratios. The sample group characterised by high Ni/Zn and Cr/Pb values conforms to modern Po River sediments, whereas a second group showing low Ni/Zn and Cr/Pb values conforms to the geochemical signature of modern Adige River sediments. A third sample group defines a “transitional” affinity that represents a geochemical mixture of Po (70%) and Adige (30%) sedimentary end-members. Based on these geochemical features, it is possible to distinguish alluvial sediments of the Po River basin (Ni/Zn > 1.0 and Cr/Pb > 4.2) from those of the Adige River basin (Ni/Zn

Mantle xenoliths from Pliocene-Quaternary volcanic diatremes in the Azrou area (Middle Atlas, Morocco) include protogranular to porphyroclastic spinel lherzolites with superimposed metasomatic textures involving pyroxenes and spinel as the main reacting phases. Thermobarometric estimates on these xenoliths show pressure ( P )–temperature ( T ) equilibrium conditions in the range 1.1–1.4 GPa and 900–1090 °C. Bulk rocks have flat heavy rare earth element (HREE) patterns (0.6–2.2 times chondrite) and are variably enriched in light REE (LREE; La N /Yb N between 1.1 and 15.6). The constituent clinopyroxenes are characterized by flat HREE distributions (5.1–11.9 times chondrite) and variable LREE enrichment with La N /Yb N from 0.4 to 25, which generally conform to the bulk rock chemistry. Trace elements characteristics of the metasomatised clinopyroxenes suggest that the metasomatasing agents were highly alkaline carbonate-rich melts such as nephelinites/melilitites or, as extreme, silico-carbonatites. Sr–Nd isotopic composition analyses carried out on clinopyroxene separates yield 87 Sr/ 86 Sr = 0.70243–0.70335, 143 Nd/ 144 Nd = 0.51273–0.51325. The helium isotope composition of olivines ranges from 6.2 to 6.8 R a . These values, coupled with the radiogenic lead isotopic composition available in the literature, suggest that the Middle-Atlas lithospheric mantle interacted with HIMU-like metasomatic components. These are in turn related to local mantle upwellings along pre-existing tectonic lineaments – located at the northern border of the West African Craton – that were reactivated as far-field foreland reaction of the Africa-Europe collisional system.

Purpose This paper investigates soils and sediments from the eastern Padanian Plain (northern Italy) in order to delineate the physiographic evolution of the area. Materials and methods We present new geochemical, mineralogical and textural analyses of alluvial sediments collected from a 13-m-deep section located a few kilometres south of Ferrara. The chronology of the related depositional events is provided from 14C dating of tree trunks buried at depths of ca. 9 m and organic matter from the underlying horizons. Results and discussion The data indicate that (1) the upper part of the sequence (down to depths of 9 m) includes sediments characterized by low nickel–chromium (Ni–Cr) concentrations ascribed to the alluvial deposits of the river Reno, deposited in the last 400 years; (2) buried soils (depths of 9–10.5 m) developed on Ni–Cr-rich sediments related to the river Po; and (3) the deeper facies (depths of 10.5–13 m) are CaCO3-free and characterized by higher amounts of organic carbon, sulphur and arsenic, reflecting episodic lacustrine/marsh environments. These wetlands probably developed in the area during the Iron and Roman ages, persisting up to the Middle Ages. Conclusions The data provide a contribution to the understanding of the evolution of the river network during the last 3,000 years and provide insights on the related paleohydrological framework that can be useful for geographical and historical reconstructions of the area. Results highlight the importance of investigating alluvial sediments to elucidate (1) fluctuations of environmental conditions and (2) anthropogenic impacts on the natural landscape.

Po is the main Italian river and the δ18O and δ2H of its water reveal a similarity between the current meteoric fingerprint and that of the past represented by groundwater. As concerns the hydrochemisty, the Ca–HCO3 facies remained constant over the last 50 year, and only nitrate significantly increased from less than 1 mg/L to more than 10 mg/L in the 1980s, and then attenuated to a value of 9 mg/L. Coherently, δ13CDIC and δ34SSO4 are compatible with the weathering of the lithologies outcropping in the basin, while extremely variable δ15NNO3 indicates contribution from pollutants released by urban, agricultural and zootechnical activities. This suggests that although the origin of the main constituents of the Po river water is geogenic, anthropogenic contributions are locally significant. Noteworthy, the associated aquifers have the same nitrogen isotopic signature of the Po river, but are characterized by significantly higher NO– 3 concentration. This implies that aquifers’ pollution is not ascribed to inflow of current river water, and that the attenuation of the nitrogen load recorded in the river is not occurring in the aquifers, due to their longer water residence time and delayed recovery from anthropogenic contamination.

This contribution was preliminarily presented with an oral communication during the “Water Day 2015” conference organized in Rome the 20th of March 2015 by the Accademia Nazionale dei Lincei. It implements a recent paper that studied the Po river water from the Alpine springs toward the Adriatic Sea (Marchina et al. Environ Sci Pollut Res 22, 5184–5203, 2015), specifically focussing on its deltaic part. The new geochemical analyses are useful to evaluate the extent of salinization (due to mixing with sea-water) and to monitor the flux of nutrients that are conveyed by the river toward the coastal environment. The paper also contains oxygen/hydrogen water isotopes that represent a snapshot of the current climatic conditions to be compared with the literature data and with the future composition to set up a hydro-archive that should be updated to evaluate on-going climatic changes. Moreover, the paper reports preliminary nitrogen isotopes composition of Po river water that trace the impact of human activities, to be monitored in the future to understand possible on-going pollutions. We conclude that geochemical researches on Po river should consider with particular attention the delta because it is an extremely fragile ecosystem where biogeochemical variations are more relevant.

The Adige River flows from the Eastern Alps to the Adriatic Sea and the understanding of its fluvial dynamics can be improved by geochemical and O-H isotopic investigation. The most negative isotopic compositions are recorded close to the source (δ(18)O between -14.1 and -13.8 ‰, δD between -100.3 and -97.0 ‰), and δD and δ(18)O values generally increase downstream through the upper part (UP, the mountainous sector), stabilizing along the lower part (LP, the alluvial plain) of the river with δ(18)O between -12.4 and -11.8 ‰, δD between -86.9 and -83.7 ‰. The isotopic variations along the stream path (δ(18)O-δD vs distance from the source) depict subparallel distributions for all the investigated periods, with less negative values recorded in winter. Total dissolved solids (TDS) concentration shows the lowest value (

Isotope analyses of lavas from the Hyblean Plateau (SE Sicily) provided first order constraints for the characterization of the relative magma sources, contributing to a better understanding of the tectono-magmatic evolution of the northernmost part of the African plate. To integrate this research, we are currently studying ultramafic xenoliths of mantle provenance exhumed by the Hyblean alkaline volcanics. These mainly consist of anhydrous spinel-facies peridotites and subordinate pyroxenites/websterites. The paragenesis of the latter is extremely variable in terms of modal proportions and mineral composition, with clinopyroxene composition ranging from Cr-diopside to Al-augite, and variable amount of spinel ± garnet. New Sr-Nd isotopic analyses carried out on hand-picked (and leached) clinopyroxenes indicate that peridotites have 87Sr/86Sr ranging from 0.70288 to 0.70309, and 143Nd/144Nd from 0.51287 to 0.51292. This Sr-Nd isotopic fingerprint approaches that of the HIMU mantle end-member, regionally referred as EAR (European Astenospheric Reservoir) to emphasize a connection with a sub-lithospheric metasomatic component ubiquitous throughout Europe, the Mediterranean area and North Africa. The Sr-Nd analyses of pyroxenites also reveal an EAR affinity, but are slightly distinct from those of peridotites. They display 87Sr/86Sr ranging between 0.70305–0.70326 and 143Nd/144Nd between 0.51292–0.51299, overlapping the composition typical of the Hyblean alkaline lavas. This possibly implies that pyroxene-rich domain significantly contributed to the genesis of the Hyblean magmas. Therefore, the presented Sr-Nd isotopic ratios suggest that the role of the pyroxene-rich mantle portions was more important than commonly considered in the petrogenetic models of Hyblean magmas. This scenario would be coherent with recent evidences highlighting the importance of pyroxenites (together with peridotites) as contributing sources to basalt generation.

The mantle xenoliths included in Quaternary alkaline volcanics from the Manzaz-district (Central Hoggar) are proto-granular, anhydrous spinel lherzolites. Major and trace element analyses on bulk rocks and constituent mineral phases show that the primary compositions are widely overprinted by metasomatic processes. Trace element modelling of the metasomatised clinopyroxenes allows the inference that the metasomatic agents that enriched the lithospheric mantle were highly alkaline carbonate-rich melts such as nephelinites/melilitites (or as extreme silico-carbonatites). These metasomatic agents were characterized by a clear HIMU Sr–Nd–Pb isotopic signature, whereas there is no evidence of EM1 components recorded by the Hoggar Oligocene tholeiitic basalts. This can be interpreted as being due to replacement of the older cratonic lithospheric mantle, from which tholeiites generated, by asthenospheric upwelling dominated by the presence of an HIMU signature. Accordingly, this rejuvenated lithosphere (accreted asthenosphere without any EM influence), may represent an appropriate mantle section from which deep alkaline basic melts could have been generated and shallower mantle xenoliths sampled, respectively. The available data on lherzolite xenoliths and alkaline lavas (including He isotopes, Ra

The Cornia Plain alluvial aquifer, in Tuscany, is exploited intensely to meet the demand for domestic, irrigation and industrial water supplies. The B concentration of groundwater, however, is often above the European limit of 1 mg L(-1), with the result that exploitation of these water resources requires careful management. Boron and Sr isotopes have been used as part of a study on the origin and distribution of B dissolved in groundwater, and indirectly as a contribution to the development of appropriate water management strategies. The geochemistry of the Cornia Plain groundwater changes from a HCO(3) facies in the inland areas to a Cl facies along the coastal belt, where seawater intrusion takes place. The B concentration of groundwater increases towards the coastal areas, while the (11)B/(10)B ratio decreases. This indicates that there is an increasing interaction between dissolved B and the sediments forming the aquifer matrix, whose B content is in the order of 100 mg kg(-1). Adsorption-desorption exchanges take place between water and the sediment fine fraction rich in clay minerals, with a net release of B from the matrix into the groundwater, and a consequent delta(11)B shift from positive to negative values. The aquifer matrix sediments therefore seem to be the major source of B dissolved in the groundwater. The groundwater-matrix interactions triggered by the ionic strength increase caused by seawater intrusion can also be detected in the Ca-Na ion exchanges. Dissolved Sr follows a trend similar to that of Ca, while the (87)Sr/(86)Sr ratio is equal to that of the exchangeable Sr of the aquifer matrix and therefore does not change significantly. These results have helped to define a new strategy for groundwater exploitation, with the final objective of reducing B concentration in the water extracted from the aquifer.

An integrated approach including geochemical analyses and geophysical investigations, aimed at characterizing the chemical composition of leachate and at highlighting the extent and magnitude of the plume in terms of spatial distribution is presented. The reason for the specific induced polarisation behaviour over landfills was not well understood. In this work we propose an explanation for this behaviour, which is being used to detect the presence of possible leaks and to track and delimit the pollution plume for several years. As a case study the example of an abandoned municipal solid waste landfill, located in Comacchio County, NE Italy, is presented, where the operative conditions for any resistivity monitoring method were to be excluded because of the high salinity of the phreatic aquifer.

This geochemical study is focused on the easternmost part of the Po River alluvial plain in Northern Italy, which is interested by widespread agricultural activities, investigating a reclaimed sector of the Province of Ferrara, known as "Valle del Mezzano" (Mezzano Low Land, hereafter reported as MLL) characterized by peat-rich soils. The chemical-mineralogical characterization of these reclaimed soils is important to compare the local geochemical backgrounds with those recorded in other sectors of the River Po plain and to monitor if the observed concentration exceeds critical thresholds. The reported analyses include (a) measurement of the soil salinity, (b) nutrient evaluation, (c) major and trace element concentrations carried out on bulk soils, (d) tests of metal extraction with both aqua regia and EDTA to highlight the distinct elemental mobility and (e) phyto-toxicological measurement of heavy metal concentrations in plants (Lactuca sativa acephala) grown on the studied soils. The results indicate (1) high soil salinity, often with drastic increase of sodium and chloride along the soil profiles, (2) high nitrogen content (in part related to anthropogenic activities) on superficial horizons and nitrate decrease along the soil profiles and (3) comparative enrichments in heavy metals with respect to other soils of the province, which indicate that peat deposits are effective in trapping metals from anthropogenic sources. This, in turn, implies potential geochemical risks for the agricultural activities. In this regard, specific concerns are related to the high nickel and arsenic content of MLL soils due to the mobility of these elements and their attitude to be taken up by plants.

This study investigates the mechanisms of arsenic (As) and other naturally occurring contaminants (F(-), U, V, B, and Mo) mobilization from Quaternary sedimentary aquifers of the Main Ethiopian Rift (MER) and their enrichment in the local groundwater. The study is based on systematic measurements of major and trace elements as well as stable oxygen and hydrogen isotopes in groundwater, coupled with geochemical and mineralogical analyses of the aquifer rocks. The Rift Valley aquifer is composed of rhyolitic volcanics and Quaternary lacustrine sediments. X-ray fluorescence (XRF) results revealed that MER rhyolites (ash, tuff, pumice and ignimbrite) and sediments contain on average 72 wt. % and 65 wt. % SiO2, respectively. Petrographic studies of the rhyolites indicate predominance of volcanic glass, sanidine, pyroxene, Fe-oxides and plagioclase. The As content in the lacustrine sediments (mean = 6.6 mg/kg) was higher than that of the rhyolites (mean: 2.5 mg/kg). The lacustrine aquifers of the Ziway-Shala basin in the northern part of MER were identified as high As risk zones, where mean As concentration in groundwater was 22.4 ± 33.5 (range of 0.60-190 μg/L) and 54% of samples had As above the WHO drinking water guideline value of 10 μg/L. Field As speciation measurements showed that most of the groundwater samples contain predominantly (~80%) arsenate-As(V) over arsenite-As(III) species. The As speciation together with field data of redox potential (mean Eh = +73 ± 65 mV) and dissolved-O2 (6.6 ± 2.2 mg/L) suggest that the aquifer is predominantly oxidative. Water-rock interactions, including the dissolution of volcanic glass produces groundwater with near-neutral to alkaline pH (range 6.9-8.9), predominance of Na-HCO3 ions, and high concentration of SiO2 (mean: 85.8 ± 11.3 mg/L). The groundwater data show high positive correlation of As with Na, HCO3, U, B, V, and Mo (R(2)0.5; p0.001). Chemical modeling of the groundwater indicates that Fe-oxides and oxyhydroxides minerals were saturated in the groundwater, suggesting that the As reactivity is controlled by adsorption/desorption processes with these minerals. The data show that As and other oxyanion-forming elements such as U, B, Mo, and V had typically higher concentrations at pH~8, reflecting the pH-dependence of their mobilization. Based on the geochemical and stable isotope variations we have established a conceptual model for the occurrence of naturally occurring contaminants in MER groundwater: 1) regional groundwater recharge from the Highland, along the Rift margins, followed by lateral flow and water-rock interactions with the aquifer rocks resulted in a gradual increase of the salinity and naturally occurring contaminants towards the center of the valley; and (2) local δ(18)O-rich lake water recharge into adjacent shallow aquifers, followed by additional mobilization of As and other oxyanion-forming elements from the aquifer rocks. We posit that the combined physical-chemical conditions of the aquifers such as oxidizing state, Na-HCO3 composition, and pH~8 lead to enhanced mobilization of oxyanion-forming elements from Fe-oxides and consequently contamination of local groundwater. These geochemical conditions characterize groundwater resources along the Eastern African Rift and thus constitute a potential threat to the quality of groundwater in larger areas of Eastern Africa.

The volcano of Tallante (Pliocene) in the Betic Cordillera (Spain) exhumed a heterogeneous xenolith association, including ultramafic mantle rocks and diverse crustal lithologies. The latter include metagabbroids and felsic rocks characterized by quartz-rich parageneses containing spinel ± garnet ± sillimanite ± feldspars. Pressure–temperature estimates for felsic xenoliths overlap (at 0.7–0.8 GPa) those recorded by the mantle-derived peridotite xenoliths. Therefore, we propose that an intimate association of interlayered crust and mantle lithologies characterizes the crust–mantle boundary in this area. This scenario conforms to evidence provided by the neighbouring massifs of Ronda and Beni Bousera (and by other peri-Mediterranean deep crust/mantle sections) where exhumation of fossil crust–mantle boundary reveals that this boundary is not sharp. The results are discussed on the basis of recent geophysical and petrological studies emphasizing that in non-cratonic regions the crust–mantle boundary is often characterized by a gradational nature showing inter-fingering of heterogeneous lithologies. Silica-rich melts formed within the crustal domains intruded the surrounding mantle and induced metasomatism. The resulting hybrid crust–mantle domains thus provide suitable sources for exotic magma types such as the Mediterranean lamproites.

A comprehensive tectono-magmatic model based on new geochemical and field data is discussed in order to highlight the significance of the high-TiO2 bimodal picrite basalt/rhyolite association in the north-eastern sector of the Ethiopian Plateau, which is considered to be the axial zone of the 30 Ma Continental Flood Basalt activity related to the Afar plume (Beccaluva et al., 2009). In this area the volcanic sequence consists of approximately 1700 m of high TiO2 (4–6.5%) picrite basalts, covered by rhyolitic ignimbrites and lavas, with an average thickness of 300 m, which discontinuously extend over an area of nearly 13,500 km2 (ca. 3600 km3). Petrogenetic modelling, using rock and mineral chemical data and phase equilibria calculations by PELE and MELTS, indicates that: 1) picrite basalts could generate rhyolitic, sometimes peralkaline, residual melts with persistently high titanium contents (TiO2 0.4–1.1%; Fluorine 0.2–0.3%; H2O 2–3%; density ca. 2.4) corresponding to liquid fractions 9–16%; 2) closed system fractional crystallisation processes developed at 0.1–0.3 GPa pressure and 1390–750 °C temperature ranges, under QFM fO2 conditions; 3) the highest crystallisation rate – involving 10–13% of Fe–Ti oxide removal – in the temperature range 1070–950 °C, represents a transitory (short-lived) fractionation stage, which results in the absence of erupted silica intermediate products (Daly gap). The eruption of low aspect ratio fluorine-rich rhyolitic ignimbrites and lavas capping the basic volcanics implies a rapid change from open- to closed-system tectono-magmatic conditions, which favoured the trapping of parental picrite basalts and their fractionation in upwardly zoned magma chambers. This evolution resulted from the onset of continental rifting, which was accompanied by normal faulting and block tilting, and the formation of shallow – N–S elongated – fissural chambers parallel to the future Afar Escarpment. The eruption of large volumes of rhyolitic magmas generated from underlying picrite basalts appears to be a common geological process acting in most plume-related LIP, which in turn is related to the inversion of the stress regime from regional extension lithosphere doming to localised continental rifting.

Water samples from cold and geothermal boreholes, hot springs, lakes and rivers were analyzed for δD, δ18O and 87Sr/86Sr compositions in order to investigate lake water–groundwater mixing processes, water–rock interactions, and to evaluate groundwater flow paths in the central Main Ethiopian Rift (MER) of the Ziway–Shala basin. Different ranges of isotopic values were recorded for different water types: hot springs show δ18O −3.36 to +3.69 and δD −15.85 to +24.23, deep Aluto-Langano geothermal wells show δ18O −4.65 to −1.24 and δD −12.39 to −9.31, groundwater wells show δ18O −3.99 to +5.14 and δD −19.69 to +32.27, whereas the lakes show δ18O and δD in the range +3.98 to +7.92 and +26.19 to +45.71, respectively. The intersection of the Local Meteoric Water Line (LMWL: δD = 7 δ18O + 11.2, R2 = 0.94, n = 42) and the Local Evaporation Line (LEL: δD = 5.63δ18O + 8, n = 14, R2 = 0.82) was used to estimate the average isotopic composition of recharge water into the basin (δD = −5.15 and δ18O = −2.34). These values are depleted if compared with the modern-day average precipitation, presumably indicating paleo-groundwater components recharged during previous humid climatic phases. The measured stable isotope values indicate that the geothermal wells, some of the hot springs and groundwater wells mainly consist of meteoric water. The Sr isotopic signatures in all waters are within the range of the Sr isotopic composition of the rift basalts and rhyolites. The variability of Sr isotopic data also pinpoints complex water–rock interaction and mixing processes in groundwater and surface water. The 87Sr/86Sr ratio ranges from 0.70445 to 0.70756 in the hot springs, from 0.70426 to 0.70537 in two deep geothermal wells, and from 0.70673 to 0.70721 in the rift lakes Ziway, Langano, Shala and Awasa. The radiogenic composition recorded by the lakes indicates that the input water was predominantly affected by progressive interaction with rhyolitic volcanics and lacustrine sediments. There is a change in MER water composition between the recharge-infiltration zone (surrounding highlands) and the discharge areas, from depleted δD, δ18O and less radiogenic Sr isotope compositions to enriched δD, δ18O and more radiogenic Sr isotope compositions. Isotope analyses are therefore useful in providing further understanding of the hydrologeological processes occurring within a productive aquifer and the surface water system.

The central Main Ethiopian Rift suffers a severe water quality problem, characterized by an anomalously high fluoride (F) content that causes an endemic fluorosis disease. The current study, conducted in the Ziway–Shala lakes basin, indicates that the F content exceeds the permissible limit for drinking prescribed by the World Health Organization (WHO; 1.5 mg/l) in many important wells (up to 20 mg/l), with even more extreme F concentration in hot springs and alkaline lakes (up to 97 and 384 mg/l respectively). The groundwater and surface water from the highlands, typically characterized by low total dissolved solids (TDS) and Ca (Mg)–HCO3 hydrochemical facies, do not show high F content. The subsequent interaction of these waters with the various rocks of the rift valley induces a general increase of the TDS, and a variation of the chemical signature towards Na–HCO3 compositions, with a parallel enrichment of F. The interacting matrixes are mainly rhyolites consisting of volcanic glass and only rare F-bearing accessory minerals (such as alkali amphibole). Comparing the abundance and the composition of the glassy groundmass with other mineral phases, it appears that the former stores most of the total F budget. This glassy material is extremely reactive, and its weathering products (i.e. fluvio/volcano-lacustrine sediments) further concentrate the fluoride. The interaction of these “weathered/reworked” volcanic products with water and carbon dioxide at high pH causes the release of fluoride into the interacting water. This mainly occurs by a process of base-exchange softening with the neo-formed clay minerals (i.e. Ca–Mg uptake by the aquifer matrix, with release of Na into the groundwater). This is plausibly the main enrichment mechanism that explains the high F content of the local groundwater, as evidenced by positive correlation between F, pH, and Na, and inverse correlation between F and Ca (Mg). Saturation indices (SI) have been calculated (using PHREEQC-2) for the different water groups, highlighting that the studied waters are undersaturated in fluorite. In these conditions, fluoride cannot precipitate as CaF2, and so mobilizes freely without forming other complexes. These results have important implications for the development of new exploitation strategies and accurate planning of new drilling sites.

The present-day northern Apennines represent an area where two different orogenic cycles took place. The most ancient is the Alpine Orogeny, initiated with a south- to south-eastward subduction of oceanic lithosphere (Early Cretaceous to Late Eocene phase), followed by continental collision. The younger is referred to the Apennines Orogeny, characterized by a west- to north-westward oceanic lithosphere subduction started from Late Eocene and still active in the southernmost sectors of Italy (Calabrian Arc). In this framework, during the Early Oligocene, an ~ 800 m thick conglomeratic succession extremely rich in volcanic material (up to ~ 90% in volume) was deposited in the Northern Apennines, forming the Aveto-Petrignacola Formation (APF). The volcanic fraction of this succession is made up of basaltic andesites, andesites and dacites, with minor rhyolites, basalts and gabbros found as pebbles ~ 0.001-0.5 m3 in size. Petrographic, mineral chemical, major and trace element analyses, as well as Sr-Nd-Pb isotopic ratios are compatible with calc-alkaline magmatism generated as a consequence of metasomatic modifications related to the subduction of oceanic lithosphere. The large spectrum of lithologies is compatible with processes of fractional crystallization of the main phases observed in thin sections. However, the large range of isotopic ratios (87Sr/86Sr = 0.7044-0.71013; 143Nd/144Nd = 0.51278-0.51223; 206Pb/204Pb = 18.44-18.83; 207Pb/204Pb = 15.55-15.67; 208Pb/204Pb = 38.05-38.85) suggests the presence of heterogeneous mantle sources, possibly coupled with interaction of melts with crustal rocks at shallow depth. On the basis of field geology constraints, we propose that the subduction-related geochemical and mineralogical characteristics of the APF volcanic rocks reflect ancient modifications of their mantle sources, lacking any evidence for a genetic link with the Apennine subduction system. Subduction-related metasomatism of APF mantle sources likely occurred during the older south-east dipping subduction of the Alpine Tethys under Northern Adria (present day Northern Italy). ⺠We identify the presence of abundant subduction-related igneous activity in N Apennines. ⺠This activity is related to the extinct Alpine subduction system rather than to the coeval Appennine subduction system. ⺠The detached Alpine oceanic slab is able to metasomatize the Adriatic mantle also 10-15 Myr after the end of the subduction. ⺠These results indicate the care needed when handling geochemical data without geological constraints.