Massimo Chiaradia

Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries.

This research first focuses on the spatial and temporal patterns of heavy metals from contrasting environments (highly polluted to deepwater sites) of Lake Geneva. The mercury (Hg) and lead (Pb) records from two deepwater sites show that the heavy metal variations before the industrial period are primarily linked to natural weathering input of trace elements. By opposition, the discharge of industrial treated wastewaters into Vidy Bay of Lake Geneva during the second part of the 20th century, involved the sedimentation of highly metal-contaminated sediments in the area surrounding the WWTP outlet pipe discharge. Eventually, a new Pb isotope record of sediments from Lake Lucerne identifies the long-term increasing anthropogenic lead pollution after ca. 1500, probably due to the development of metallurgical activities during the High Middle Ages. These data furthermore allows to compare the recent anthropogenic sources of water pollution from three of the largest freshwater lakes of Western Europe (lakes Geneva, Lucerne, and Constance). High increases in Pb and Hg highlight the regional impact of industrial pollution after ca. 1750-1850, and the decrease of metal pollution in the 1980s due to the effects of remediation strategies such as the implementation of wastewater treatment plants (WWTPs). However, at all the studied sites, the recent metal concentrations remain higher than pre-industrial levels. Moreover, the local scale pollution data reveal two highly contaminated sites (>100 μg Pb/g dry weight sediment) by industrial activities, during the late-19th and early-20th centuries (Lake Lucerne) and during the second part of the 20th century (Vidy Bay of Lake Geneva). Overall, the regional scale pollution history inferred from the three large and deep perialpine lakes points out at the pollution of water systems by heavy metals during the last two centuries due to the discharge of industrial effluents.

Different contamination styles of prehistoric human teeth at a Swiss necropolis (Sion, Valais) inferred from lead and strontium isotopes

Separate fractions of dentine and enamel of 12 individuals from the necropolis of Sion (Valais, Switzerland) have been analyzed for Pb and Sr isotope compositions. The individuals span a time period of more than 1 ka from ∼5.2 ka B.P. to ∼4.1 ka B.P. and include Middle Neolithic, Upper Neolithic, Bell Beaker and Old Bronze age civilizations. Individuals were buried either into or close to dolmens or into soil at 4 different sites on the alluvial fan of the Sionne stream, a tributary of the Rhone river. Isotopic composition of dentine and enamel pairs of the individuals indicate that teeth underwent post mortem contamination. Lead contamination is due to two different sources, petrol and natural Pb from soils. The preponderance of either petrol or natural Pb contamination in teeth depends on the burial sites. Differences in the content of Pb-retaining particles (organic matter, Fe-hydroxides, clay minerals), that depend largely on soil grain size, are suggested to be responsible for the differential Pb contamination at the investigated burial sites. Strontium contamination is stronger in individuals buried into or close to dolmens, which are made of calc-schist slabs. Despite post mortem contamination, both Pb and Sr isotopes have allowed the identification of an individuals enamel with isotopic compositions significantly different from those of the local substratum, suggesting his immigration to the Sion area from a geologically different region. This individual belongs to the Bell Beaker civilization, which is considered to have immigrated into Western Europe and the Mediterranean basin at the end of the Neolithic. Systematic differences between enamel and dentine isotopic compositions of all other individuals analyzed suggest that they assimilated in vivo Pb and Sr from an area nearby to that in which they were buried.

Crustal thickness control on Sr/Y signatures of recent arc magmas: an Earth scale perspective

Arc magmas originate in subduction zones as partial melts of the mantle, induced by aqueous fluids/melts liberated by the subducted slab. Subsequently, they rise through and evolve within the overriding plate crust. Aside from broadly similar features that distinguish them from magmas of other geodynamic settings (e.g., mid-ocean ridges, intraplate), arc magmas display variably high Sr/Y values. Elucidating the debated origin of high Sr/Y signatures in arc magmas, whether due to mantle-source, slab melting or intracrustal processes, is instrumental for models of crustal growth and ore genesis. Here, using a statistical treatment of >23000 whole rock geochemical data, I show that average Sr/Y values and degree of maturation (MgO depletion at peak Sr/Y values) of 19 out of 22 Pliocene-Quaternary arcs correlate positively with arc thickness. This suggests that crustal thickness exerts a first order control on the Sr/Y variability of arc magmas through the stabilization or destabilization of mineral phases that fractionate Sr (plagioclase) and Y (amphibole ± garnet). In fact, the stability of these mineral phases is function of the pressure at which magma evolves, which depends on crustal thickness. The data presented show also that high Sr/Y Pliocene-Quaternary intermediate-felsic arc rocks have a distinct origin from their Archean counterparts.

Behaviour of airborne lead and temporal variations of its source effects in Geneva (Switzerland): comparison of anthropogenic versus natural processes

Lead isotope compositions of aerosols from two Geneva stations (city and country), monitored during one year, show the existence of two main lead sources, petrol and waste incineration. A third, subordinate source is represented by coal burning and is detectable in winter. This source is believed to be of local importance due to the very low coal consumption in Geneva. Lead contributions from the three sources have been apportioned using isotopic mixing equations. During summer, petrol contributes about 70% of the total lead in the city while the incinerator contributes 65% of the total lead in the country. During winter, coal burning provides in average 15% of the total lead in the city. Atmospheric lead concentrations are mainly controlled by wind speed. As expected, wind dilution is more effective on lead aerosols originating from sources situated farthest from the monitoring stations. Thus, incinerator lead contributions at the city station decrease linearly with wind speed in winter due to their transport from a longer distance than automotive emissions. Due to the same process, during summer petrol contributions are anticorrelated with wind speed at the country. Incinerator winter contributions in the city display greater variations than in summer, suggesting a seasonal meteorological regime which enhances the wind speed control on incinerator aerosol dilution. We relate this meteorological regime to the lower mixing height typical of the cold season. Isotope-based apportionments of lead sources and their statistical comparison with particulate matter and sulfur dioxide concentrations have also allowed a qualitative assessment of the impact of traffic and coal emissions on PM and SO2 levels at the two monitored sites.

Identification of secondary lead sources in the air of an urban environment

High precision lead isotopic data have been measured from particulates deposited on filters from two suburbs of Sydney (NSW, Australia) and gasoline from two main brands to evaluate the source of lead in air following the phasing out of leaded gasoline in Sydney in 1986 and a 25% reduction of lead in leaded gasoline in 1994. These measures have resulted in a 75% reduction of lead in Sydney air nowadays. Despite these positive figures, our results indicate that gasoline still accounts for more than 90% of the lead in the atmosphere of this city. However, when compared with an earlier investigation carried out in the period 1979–1981, our data show that a background source with a 206Pb/204Ph isotopic ratio higher than petrol has become detectable. We have used a best fitting mathematical procedure to identify the isotopic ratio and percentage contribution of this source to the air. The values that we have obtained are ∼ 18.2 and ∼7%, respectively, for the 206Pb204Pb ratio and the percentage contribution. Several local background sources are considered, including natural lead from soils, wood burning, coal burning in power stations and aircraft profellants. We also draw attention to the similarity of the background isotopic composition in Sydney air aid isotopic ratios measured in snows of Antarctica.

Identification of historical lead sources in roof dusts and recent lake sediments from an industrialized area: indications from lead isotopes

X-ray fluorescence and stable lead (Pb) isotopic analyses have been undertaken on dusts, known from microscopic investigation to contain significant quantities of industrially- and urban-derived particulate matter, present in the roof cavities of houses in the Illawarra region (N.S.W., Australia), with the objective of examining the historic record of Pb pollution. All investigated houses contained in excess of 250 micrograms g-1 Pb, with dwellings close to a copper smelter, in a large industrial complex including a major steelworks, containing higher (> 2500 micrograms g-1) Pb concentrations. The isotopic composition in the dusts, expressed here as 206Pb/204Pb, is relatively constant at 17.0, irrespective of dwelling age or distance from the industrial complex. Contamination of the dusts by Pb sourced from paint cannot explain the isotopic uniformity of the dust samples. Isotopic modelling indicates that the dusts contain Pb derived from the copper smelter, gasoline-air Pb and a minor contribution from coal-utilising sources. Lead loading was also investigated in the adjacent lagoon, which acts as a natural sink for particulate matter in the Illawarra region. Isotopic data and modelling indicate that one natural and four anthropogenic sources contribute to the Pb burden of this lagoon. The natural source consists of Permian rocks cropping out in the catchment area which have a 206Pb/204Pb of approximately 18.7. The suggested anthropogenic sources are an old disbanded base-metal (Pb) smelter (206Pb/204Pb approximately 16.2-16.3), the copper smelter (206Pb/204Pb approximately 17.9), gasoline-air derived Pb (206Pb/204Pb approximately 16.4-16.5) and industries utilising coal, for example the recently closed thermal coal-fired power station (206Pb/204Pb approximately 18.9). The relative contributions of the base-metal (mainly lead) smelter and gasoline-air Pb in the sediment can only be partly assessed due to the isotopic similarity of these sources. Likewise the natural background and coal source (e.g. power station) contributions can only be estimated from historical data. Age estimations for sediment cores, using 137Cs, provide some control on these assessments. Near surface sediments in the lagoon have a relatively constant 206Pb/204Pb of 17.6-17.7, irrespective of sample location. Isotopic calculations, together with records of particulate matter pollution emissions, indicate a link between the Pb in roof dusts (206Pb/204Pb approximately 17.0) and Pb contamination of the near surface (upper 20 cm) lagoonal sediments via a homogeneous, non-unique source of lead whose isotopic composition closely matches that of the dusts. Over the last 5 decades, atmospheric fallout of Pb-bearing particulate matter appears to have been the dominant pathway for addition of Pb to the lagoon and dwellings in the Illawarra region.

Contamination of houses by workers occupationally exposed in a lead-zinc-copper mine and impact on blood lead concentrations in the families.

OBJECTIVE: To evaluate the pathway of leaded dust from a lead-zinc-copper mine to houses of employees, and the impact on blood lead concentrations (PbB) of children. METHODS: High precision lead isotope and lead concentration data were obtained on venous blood and environmental samples (vacuum cleaner dust, interior dustfall accumulation, water, paint) for eight children of six employees (and the employees) from a lead-zinc-copper mine. These data were compared with results for 11 children from occupationally unexposed control families living in the same city. RESULTS: The median (range) concentrations of lead in vacuum cleaner dust was 470 (21-1300) ppm. In the houses of the mine employees, vacuum cleaner dust contained varying higher proportions of mine lead than did airborne particulate matter measured as dustfall accumulated over a three month period. The median (range) concentrations of lead in soil were 30 (5-407) ppm and these showed no evidence of any mine lead. Lead in blood of the mine employees varied from 7 to 25 micrograms/dl and was generally dominated by mine lead (> 60%). The mean (SD) PbB in the children of the mine employees was 5.7 (1.7) micrograms/dl compared with 4.1 (1.4) micrograms/dl for the control children (P = 0.02). The PbB of all children was always < 10 micrograms/dl, the Australian National Health and Medical Research Council goal for all Australians. Some of the control children had higher PbB than the children of mine employees, probably from exposure to leaded paint as six of the eight houses of the control children were > 50 years old. In five of the eight children of mine employees > 20% of PbB was from the lead mine. However, in the other three cases of children of mine employees, their PbB was from sources other than mine lead (paint, petrol, background sources). CONCLUSIONS: Houses of employees from a lead mine can be contaminated by mine lead even if they are not situated in the same place as the mine. Delineation of the mine to house pathway indicates that lead is probably transported into the houses on the clothes, shoes, hair, skin, and in some cases, motor vehicles of the workers. In one case, dust shaken from clothes of a mine employee contained 3000 ppm lead which was 100% mine lead. The variable contamination of the houses was not expected given the precautions taken by mine employees to minimise transportation of lead into their houses. Although five out of the eight children of mine employees had > 20% mine lead in their blood, in no case did the PbB of a child exceed the Australian National Health and Medical Research Council goal of 10 micrograms/dl. In fact, some children in the control families had higher PbB than children of mine employees. In two cases, this was attributed to a pica habit for paint. The PbB in the children of mine employees and controls was independent of the source of lead. The low PbB in the children of mine employees may reflect the relatively low solubility (bioavailability) of the mine dust in 0.1 M hydrochloric acid (< 40 %), behaviour--for example, limited mouthing activity--or diet.

Gas-to-particle conversion of mercury, arsenic and selenium through reactions with traffic-related compounds? Indications from lead isotopes

Relationships between metal (Cu, Zn, Pb, Cd, Hg, As, Se) concentrations and lead isotope compositions of Geneva aerosols for the period October 1996–September 1997 are investigated. Lead in Geneva is contributed by petrol, waste incineration and, only in winter, coal. Lead and copper during summer and copper and zinc during winter correlate positively with the lead isotope signature of the incinerator suggesting derivation of relevant amounts of these metals from such source. On the contrary, three volatile metals (Hg, As, Se), which can be present in the atmosphere as gaseous compounds at significant levels, display an anomalous strong correlation with the isotope signature of traffic-lead in summer. These metals are unlikely to be contributed by automotive combustion and their most probable summer source is also represented by waste incineration. We suggest that the correlation of Hg, As and Se with automotive lead could unveil conversion of these volatile metals from the gaseous to the particulate phase in concomitance with increasing concentration of traffic-related compounds of which lead isotopes are a valid tracer. Hg, As and Se do not correlate directly with traffic-related gases (e.g. CO, NOx, O3, THC) while they do correlate only with automotive lead. This is probably due to an atmospheric residence time more similar to traffic-generated lead aerosols than to automotive gases. It has been suggested elsewhere that gaseous mercury can be transformed to the particulate phase through atmospheric reactions with traffic-related oxidants like ozone. Our data might indicate that similar processes are responsible for the gas-to-particle conversion not only of gaseous Hg, but also of As and Se in the atmosphere of Geneva.

Geochemical and Sr–Nd–Pb–O isotope composition of granitoids of the Early Cretaceous Copiapó plutonic complex (27°30′S), Chile

Early Cretaceous plutonic rocks exposed south of Copiapo form part of the Coastal Batholith of northern Chile. These rocks intrude arc- derived volcanic and volcaniclastic rocks and marine limestones that were deposited in the Early Cretaceous Atacama backarc basin. The Copiapo plutonic complex consists mainly of calc-alkaline, medium- to coarse-grained diorite, granodiorite, tonalite, monzodiorite, and quartz monzonite. The plutonic rocks are subalkaline to alkaline, metaluminous, magnetite-series, volcanic arc, I-type granitoids. Batholithic magmas are a heat, potential fluid, metal, and sulphur source for the hydrothermal iron oxide-rich Cu–Au mineralization in the Candelaria- Punta del Cobre district. Ore-related hydrothermal alteration affected large portions of the Copiapo complex. The least altered batholithic rocks have initial 87Sr/86Sr of 0.703070–0.703231; initial 143Nd/144Nd of 0.512733–0.512781; and 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb of 18.428–18.772, 15.550–15.603, and 38.127–38.401, respectively. The d18O values for these rocks range from þ6.9 to þ8.6‰. Isotope signatures and trace element distributions suggest that the magmas are mantle derived. A subduction fluid-modified mantle source may explain the geochemical characteristics of the Copiapo complex. The ascent of magmas occurred along deep-rooted structures without significant crustal contamination, though minor contamination by relatively young (e.g. Jurassic) igneous rocks during ascent is possible. Intrusive rocks with high-K to shoshonitic characteristics probably represent residual liquids of less evolved magmas. The regional geologic context suggests that the plutons of the Copiapo complex were emplaced at a relatively shallow crustal level of 2–3 km. q 2003 Elsevier Ltd. All rights reserved.

Supra-subduction zone magmatism of the Neyriz ophiolite, Iran: constraints from geochemistry and Sr-Nd-Pb isotopes

The Neyriz ophiolite along the northeast flank of the Zagros fold-thrust belt in southern Iran is an excellent example of a Late Cretaceous supra-subduction zone (SSZ)-related ophiolite on the north side of the Neotethys. The ophiolite comprises a mantle sequence including lherzolite, harzburgite, diabasic dikes, and cumulate to mylonitic gabbro lenses, and a crustal sequence comprising a sheeted dike complex and pillow lavas associated with pelagic limestone and radiolarite. Mantle harzburgites contain less CaO and Al2O3, are depleted in rare earth elements, and contain spinels that are more Cr-rich than lherzolites. Mineral compositions of peridotites are similar to those of both abyssal and SSZ- peridotites. Neyriz gabbroic rocks show boninitic (SSZ-related) affinities, while crustal rocks are similar to early arc tholeiites. Mineral compositions of gabbroic rocks resemble those of SSZ-related cumulates such as high forsterite olivine, anorthite-rich plagioclase, and high-Mg# clinopyroxene. Initial εNd(t) values range from +7.9 to +9.3 for the Neyriz magmatic rocks. Samples with radiogenic Nd overlap with least radiogenic mid-ocean ridge basalts and with Semail and other Late Cretaceous Tethyan ophiolitic rocks. Initial 87Sr/86Sr ranges from 0.7033 to 0.7044, suggesting modification due to seafloor alteration. Most Neyriz magmatic rocks are characterized by less radiogenic 207Pb/204Pb (near the northern hemisphere reference line), suggesting less involvement of sediments in their mantle source. Our results for Neyriz ophiolite and the similarity to other Iranian Zagros ophiolites support a subduction initiation setting for its generation.