Enrico Dinelli

Geochemical and mineralogical variations as indicators of provenance changes in Late Quaternary deposits of SE Po Plain

Combined geochemical and mineralogical characterisation of mudstone-prone successions can provide suitable indicators of sediment provenance. A case study from the Late Quaternary depositional sequence of southeastern Po Plain shows that major changes in geochemical and mineralogical composition can be ascribed to changes in sediment dispersal patterns occurring during the last 30 ka in response to fluctuating sea level. The Po River, with a mixed contribution from the Alpine and Apenninic chains and its southern tributaries flowing from the Apennines, acted as the major feeders for the study area during the Late Quaternary. Chromium (and nickel) among trace elements, and serpentine (and dolomite) among minerals appear as the major provenance indicators for the study succession, allowing distinction of an Apenninic (chromium- and serpentine-poor) province from a mixed Alpine–Apenninic, Po-related (chromium- and serpentine-rich) province. The relatively low Cr/Al2O3 and serpentine/silicate ratios recorded in sediments of late Pleistocene age (<30 ka BP), which accumulated at the last glacial maximum, suggest that during lowstand times and early stages of transgression, the southeastern Po Plain was beyond the Po River influence, being fed uniquely by rivers of Apenninic provenance. Increasing Cr/Al2O3 and serpentine/silicate ratios, recorded within back-barrier transgressive deposits (8–10 ka BP) in the Comacchio and Ravenna sectors, reflect a major change in sediment supply taking place during the Holocene, when partially barred environments largely connected with the open sea became established in the study area, and Po-derived detritus was delivered to estuaries and lagoons by littoral drift. Maximum chromium and serpentine values are recorded at peak transgression and during the following sea-level highstand (6 ka BP–Present) when sediment supply exceeded the rate at which new accommodation space was created, leading to extensive Po-delta progradation. The drop in Cr/Al2O3 and serpentine/silicate ratios recorded in some cores at top of the Holocene succession reflects the local reestablishment, behind the prograding Po-delta complexes, of an alluvial plain drained by rivers of Apenninic provenance as a result of distributary channel switching and delta lobe abandonment. Geochemical and mineralogical analyses show negligible compositional variations between Pleistocene and Holocene deposits landward of the line of maximum marine incursion especially close to the basin margin. In these instances, sample composition throughout the entire stratigraphic succession clearly suggests an ongoing supply from the adjacent Apenninic chain. Comparison with sand compositional analyses from major sand bodies of the same stratigraphic succession highlights the complementary but fundamental role of geochemical and mineralogical characterisation of clays for provenance research.

The concept of compositional data analysis in practice - Total major element concentrations in agricultural and grazing land soils of Europe

Applied geochemistry and environmental sciences invariably deal with compositional data. Classically, the original or log-transformed absolute element concentrations are studied. However, compositional data do not vary independently, and a concentration based approach to data analysis can lead to faulty conclusions. For this reason a better statistical approach was introduced in the 1980s, exclusively based on relative information. Because the difference between the two methods should be most pronounced in large-scale, and therefore highly variable, datasets, here a new dataset of agricultural soils, covering all of Europe (5.6 million km(2)) at an average sampling density of 1 site/2500 km(2), is used to demonstrate and compare both approaches. Absolute element concentrations are certainly of interest in a variety of applications and can be provided in tabulations or concentration maps. Maps for the opened data (ratios to other elements) provide more specific additional information. For compositional data XY plots for raw or log-transformed data should only be used with care in an exploratory data analysis (EDA) sense, to detect unusual data behaviour, candidate subgroups of samples, or to compare pre-defined groups of samples. Correlation analysis and the Euclidean distance are not mathematically meaningful concepts for this data type. Element relationships have to be investigated via a stability measure of the (log-)ratios of elements. Logratios are also the key ingredient for an appropriate multivariate analysis of compositional data.

TEPHRA LAYERS IN LATE QUATERNARY SEDIMENTS OF THE CENTRAL ADRIATIC SEA

Abstract Magnetic susceptibility curves of ten cores, collected in the western Adriatic shelf and in the Mid-Adriatic Deep, allowed us to recognize thirty tephra layers whose age, based on physical and biostratigraphic data, encompass a time interval ranging from less than 70 ka to the Present. Chemical features of the tephra, defined by SEM–EDS analyses performed on glass shards, indicate alkaline affinity, mainly with K/Na>1, and trachytic compositions with two minor benmoreitic and phonolitic groups. These characteristics are consistent with Campanian and subordinate Etnean provenances. Because of chemical and age constraints the glass shards can be referred to six tephra layers already described in the literature, such as C20, C14 (Citara/Ischia), C10 (Campanian Ignimbrite), C2/NYT (Neapolitan Yellow Tuff), AMS/PF (Agnano Monte Spina/Phlegrean Fields) from Campanian area, and Y1 from Etna volcano, indicating an age ranging from about 70 to 4 ka. AMS/PF and C2/NYT, dated 4.4 and 12.3 ka respectively, are the most widespread tephra beds in the study cores. The occurrence of AMS/PF, never recorded in marine sequences up to now, represents a very good marker for Holocene Adriatic sediments; C2/NYT already recorded in the central Tyrrhenian Sea, in lacustrine sediments from southern Italy and in the Campanian area, is a good stratigraphic marker for inter-sea and sea–land correlations. Y1 tephra, dated 14.2 ka, also occurs in on-land sediments of central Italy and in marine sediments from the Tyrrhenian and Ionian seas: it now represents one of the most widespread stratigraphic markers in the central Mediterranean region.

Metal distributions in plants growing on copper mine spoils in Northern Apennines, Italy: the evaluation of seasonal variations

Abstract Mine spoil dump material and plants were sampled from the pyrite-chalcopyrite mining area of Vigonzano (Northern Apennines, Italy). Mine spoils have high concentrations of Fe, Mg, Cu, Cr, Co and Ni, and are characterized by moderately to strongly acid environmental conditions. Water leaching tests indicate the following order of extraction: Zn≥Cu>Ni>Fe≥Cr. The plants Silene armeria (Caryophyllaceae) Salix spp. (Salicaceae) and Populus nigra (Salicaceae) were sampled at 4 different growing stages to evaluate seasonal variations in metal concentrations. The results indicate that metal concentrations increase with plant ageing, the highest concentrations being observed in leaves. Low specific diversity in the mine spoil area is the result of severe environmental conditions, but some plants can tolerate high concentrations without sign of stress. Silene armeria is widespread in the Vigonzano mine spoil area and is actually able to tolerate high metal concentrations (up to 504 μg/g Cu, 174 μg/g Zn, 127 μg/g Ni and 138 μg/g Cr), extremely high when compared to those of a S. armeria population from an unpolluted site. The variations of BAC (Biological Accumulation Coefficient) for the plants growing on the Vigonzano mine spoil area indicates that Zn is the element most easily absorbed by plants. An absorption sequence Zn > Co > Cu > Ni > Fe > Cr can be generalized for plants growing on the mine spoil area indicating the importance of soil solution composition in plant absorption.

Natural and anthropogenic SO4 sources in the Arno river catchment, northern Tuscany, Italy: a chemical and isotopic reconnaissance

Abstract The δ 34 S isotope signature of aqueous SO 4 2− in the main river Arno and principal tributaries was investigated along with major ion chemistry in order to check the pollution effects in the water network of a heavily industrialized and densely urbanized catchment extending in Tuscany over an area of 8228 km 2 from the Apennine Ridge to the Tyrrhenian Sea. Major towns include Florence and Pisa. Analyses are presented for 29 water samples from the Arno river and 36 water samples from the tributaries, all collected in 1996–1997 during low flow hydrologic conditions. Samples from the Arno are distributed from source to mouth and those from tributaries upstream from the confluence points. The Arno river solutes consist mainly of Ca 2+ and HCO 3 − , but the proportions of Na + , Cl − and SO 4 2− increase downstream, in keeping with the basically anthropogenic origin of the latter. The δ 34 S(SO 4 2− ) signature also increases downstream, with the most depleted values in the source zone. The seawater ingression into the river is documented by distinctly higher chemical and isotopic parameters at about 13 km from the mouth. In general, the tributaries behave similarly to the Arno for both their chemical and isotopic compositions, with increasing δ 34 S, Na + , Cl − and SO 4 2− downstream. The δ 34 S of SO 4 2− in natural inputs is estimated to range approximately between −15 and +4‰ from oxidation of pyrite disseminated in country rocks, and between +15 and +23‰ from dissolution of evaporites, whereas the δ 34 S of anthropogenic SO 4 2− should be variable within the range 1–8‰.

Geochemistry of Oligocene–Miocene sandstones of the northern Apennines (Italy) and evolution of chemical features in relation to provenance changes

Integrated petrographic and geochemical criteria for provenance determination in clastic sedimentary rocks are applied to four flysch formations of Oligocene–Miocene age in the northern Apennines (Italy). Major and trace element geochemistry of 60 sandstones for the Macigno Formation, Monte Modino Formation, Monte Cervarola Formation, and Marnoso-arenacea Formation is presented. Geochemical criteria of discrimination based on element ratios (Y/Ni, Cr/V, Rb/Sr and Cu/Al2O3) allow distinction of the Macigno, Modino, Cervarola and Marnoso-arenacea. The differing geochemical features of the four flysch formations suggest a decrease of ultramafic and metamorphic supply and increase of carbonate and intrusive rock fragments from Macigno to Cervarola, and a sharp increase of carbonate/siliciclastic ratio at the transition to the Marnoso-arenacea Formation. All this provides significant insights and additional constraints about the chronostratigraphic evolution of sediment supply in the northern Apennines foredeep from Oligocene to Tortonian times: the decrease of detritus supply from the Adriatic Plate and the increase in felsic detritus from the Alps become apparent after the Oligocene–Miocene transition; the carbonate influx from E and SW starts from the Lower Miocene; the increasing importance of the Apennine Chain input, with the recycling of turbiditic successions and rocks from Ligurian units, is testified by the geochemical features of the Marnoso-arenacea Formation. On the whole, the applicability of the geochemical techniques to clastic sedimentary rocks is confirmed, but also the complementary character of petrographic and geochemical methods in provenance and evolution studies is emphasized.

Different mechanisms account for enhanced copper resistance in Silene armeria ecotypes from mine spoil and serpentine sites

The resistance to excess Cu was evaluated in solution culture in three ecotypes of Silene armeria from different origin, a garden soil (Cadriano), a serpentine site (Prinzera) and a Cu mine spoil (Vigonzano). Root elongation and viability staining of root tip cells were used as indicators for Cu resistance. The Cu resistance increased in the order Cadriano <Prinzera<Vigonzano. Renewal of the root cap in Prinzera and enhanced border cell production in Vigonzano in response to excess Cu provided a more efficient protection of the root tip meristem than in Cu sensitive Cadriano. The enhanced Cu resistance in Prinzeracould not be attributed to high soil Cu acting as a natural selection factor at the serpentine site. In PrinzeraCu exclusion from roots and shoots probably was a consequence of root impermeabilization causing reduced radial water and ion flux in roots. In contrast, the high Cu resistance in the mine spoil ecotype, Vigonzano, was due to both reduced Cu uptake and higher tissue tolerance of Cu.

Different types of fine-grained sediments associated with acid mine drainage in the Libiola Fe–Cu mine area (Ligurian Apennines, Italy)

Abstract Different types of fine-grained chemical precipitates were characterized in the surroundings of the pyrite-chalcopyrite mine of Libiola (Northern Italy). Both water chemistry and sediment composition were used to investigate metal mobility near the mine area. Local drainage waters were very acidic (with a pH as low as 2.5) and were rich in dissolved metals (Fe, Al, Cu, Zn, Mn, Ni). Sediments associated with low pH water (pH

Chemistry and sulfur isotopic composition of precipitation at Bologna, Italy

Individual and monthly precipitation samples from the polluted atmosphere of Bologna (Emilia-Romagna province) were collected during March 1996 to May 1997 and analyzed for major ions in solution and S isotopes in dissolved SO4. Weighted mean enrichment factors relative to seawater are found to be 1.0 for Na, 15.2 for K, 105 for Ca, 3.3 for Mg, 17.3 for SO4 and 663 for HCO−3. Very good positive correlations are observed for the Ca2+–Mg2+–HCO−3–SO2−4–NO−3 system, indicating that dissolution of Ca (±Mg)-carbonate particles by H2SO4 and HNO3 from combustion of oil and gas is a major process controlling the chemical composition of rain and snow. Na+ and Cl− in monthly precipitation derive essentially from sea spray, but the contribution of Na+ from continental sources is appreciable in a number of individual rains. NH+4 appears to be on average more abundant in spring and summer precipitation, its main sources being microbial activity in soils and application of fertilizers. K+ is probably of continental origin from soil dust. The S isotopic composition of SO4 is systematically positive, with mean δ34S values of +3.2±1.6‰ (n=40) in individual precipitation and +2.8±1.4‰ (n=12) in monthly precipitation. These isotopic compositions are interpreted in terms of a dominant contribution of S from anthropogenic emissions and subordinate contributions from biogenic and marine sources. Pollutant SO4 is estimated to have a δ34S value in the range +2.5 to +4.5‰, whereas a distinctive δ34S of −4.5‰ or lower indicates SO4 from oxidation of biogenic gases. The isotopic and chemical compositions of SO4 do not depend on wind direction, thus testifying to a mostly local source for pollutant S in the Bologna atmosphere.

Influence of the Ca/Mg ratio on Cu resistance in three Silene armeria ecotypes adapted to calcareous soil or to different, Ni- or Cu-enriched, serpentine sites

This hydroponic study addresses the influence of low (0.3) and high (4.0) Ca/Mg molar ratios on Cu resistance of Silene armeria ecotypes from different habitats: a calcareous soil (ecotype Cadriano), a Ni-rich serpentine site (ecotype Prinzera), and an acid Cu-mine spoil soil containing serpentinite (ecotype Vigonzano). Under control conditions, without excess Cu, only Cadriano was negatively affected by the low Ca/Mg ratio. Under both low and high Ca/Mg ratios Cu resistance followed the order Vigonzano more more than Prinzera > Cadriano. More efficient Cu exclusion accounted for enhanced Cu resistance in Prinzera. The low Ca/Mg ratio increased Cu uptake in Prinzera but did not worsen toxicity effects; i.e. the plants had higher internal Cu effect concentrations. In Vigonzano Cu resistance was enhanced by the low Ca/Mg ratio. This was due only in part to better Cu exclusion. Magnesium-induced tolerance to higher Cu tissue concentrations appears to be in ecotypes from serpentine and acid mine spoils, but not in plants from calcareous soil, the exposure to low Ca/Mg ratio favours internal detoxification of Cu by means of more efficient chelation and compartmentation.