Historical Metal Research Articles

Reliability assessments of using different heavy metals from remote sediment records to reconstruct historical pollution.

Interpreting heavy metal variations in sedimentary records is an important approach to understand historical pollution. However, few studies have investigated the reliability of different heavy metals in sedimentary records for reconstructing historical pollution. This study retrieved two adjacent lakes' sediment cores from a remote area in North China and investigated their temporal changes in excessive metal fluxes. Combined with a novel index of the ratios of atmospheric emissions of anthropogenic metals to background metal values in lake sediments, the reliability and influencing factors of eight metals (Cr, Co, Ni, Cu, As, Zn, Cd, and Pb) in sediments to reconstruct historical pollution were studied. Vertical As variations in the sediments were controlled mainly by early diagenesis effects, although anthropogenic pollution might also have had an impact. Consequently, As profiles in lake sediment records are usually difficult to reflect historical pollution. (2) Among the eight metals, Zn, Cd, and Pb in both lakes have been affected mainly by human pollution and insignificantly by natural factors. Their excessive flux variations in the two records were highly consistent with the historical trend of economic/industrial development. Relatively, these three metals can reliably reflect historical pollution. (3) Compared with Zn, Cd, and Pb, Cr, Co, Ni, and Cu in the two lakes have been relatively less affected by anthropogenic pollution. During the period of relatively high anthropogenic metal emissions (post-∼1980), they could roughly reflect historical pollution in the region; however, during the period of relatively low emissions (before ∼1980), they appeared to exhibit no signs of pollution. This suggests the complexity of using them in remote records to reconstruct historical pollution. The importance of this study lies in its potential to provide critical guidance for the use of aquatic sediment records from relatively remote areas in reconstructing the historical metal pollution.

Hydrophysical Properties of Peat in Undisturbed and Smelter‐Impacted Peatlands: Implications for Moss Recovery, Drought and Wildfire

ABSTRACTPeatlands are critical for global climate regulation storing approximately 500 Gt of carbon and accounting for 33% of global soil organic carbon. Regionally, these ecosystems provide essential wildfire resilience and are important pollutant sinks but degradation puts these key ecosystem services at risk. Smelting operations in Sudbury, ON, Canada, released approximately 12 000 t of particulate copper and nickel into the atmosphere between 1883 and 1969. Toxic metal and sulphur deposition on peatlands from smelting activities caused the widespread decline of keystone peatland moss species (i.e., Sphagnum) and altered peat properties. The changes in peat hydrophysical properties due to historical metal contamination likely reduce peatland resilience to drought and wildfires, thereby increasing the potential for toxic heavy metal remobilisation; however, these peat properties changes have yet to be quantified. We determine 1) how historical smelter pollution impacts peat hydrophysical properties by measuring bulk density, saturated hydraulic conductivity and soil water retention in the upper 40 cm of both undisturbed (located ~160 km outside the deposition region) and smelter‐impacted peatlands, 2) use these data to explore the vulnerability of these peatlands to wildfires and drought and 3) assess the potential for natural Sphagnum moss recovery. Smelter‐impacted peat had a significantly higher bulk density, lower macroporosity and saturated hydraulic conductivity that drove large differences in modelled soil water tension profiles during simulated drying events. These differences in soil water tension and retention profiles resulted in the smelter‐impacted peat having a far greater proportion of the peat profile that would be susceptible to smouldering combustion than the undisturbed peat. Additionally, the smelter‐impacted peat properties likely contributed to the limited Sphagnum moss recovery, while concurrently increasing drought and wildfire risk. As such, we argue that contaminated peatland restoration is necessary to enhance Sphagnum moss recovery to mitigate toxic metal remobilisation risk from drought and wildfire.

Cleansing our waters: how riffle fish communities in the Spring River of Kansas responded to pollution legislation, mining remediation, and improved water quality.

Metal pollution from mining is a threat to lotic fishes, although legislation that requires improved water quality and provides funding for remediation has been enacted to combat this stressor. The Spring River in southeastern Kansas historically received inputs of cadmium, copper, lead, and zinc that reduced the prevalence of several sensitive and imperiled fishes. Long-term reductions in these toxic metals have occurred since the 1990's because of management activities, but presently it is unknown how riffle fish communities responded to improved water quality. As such, the objective of our research was to quantify changes in riffle fish community structure between 1993-1995 and 2019-2021 using a before-after-control-impact (BACI) study design. Responses were quantified with univariate analyses to examine the interactive effects of time period (i.e., historical versus contemporary), pollution tolerance classification (i.e., intolerant, moderately-intolerant, moderately-tolerant, and tolerant), and site position (i.e., above versus below the most severe historical metal pollution inputs) on relative abundance, occupancy, and species richness of riffle fishes. We used multivariate analyses to examine temporal changes in community structure above and below pollution inputs. Our findings indicated that intolerant fish species relative abundance increased between the historical and contemporary time periods throughout the Spring River. Occupancy of all fishes increased over time in the formerly metal contaminated portion of the Spring River, becoming similar to values in the reference reach. Changes in species richness depended on site position and pollution tolerance, as temporal increases of intolerant and moderately intolerant species richness were most pronounced in the lower Spring River below historical metal pollution inputs. Multivariate analyses revealed a significant interaction between time period and site position, as there was a shift in community structure over time in the lower reach that was less pronounced in the upper reach. Most of the intolerant species that increased in prevalence are of high conservation priority, thus our research suggested that legislation enacted to improve water quality produced a ripple effect that stimulated the recovery of imperiled fish species.

Entangled social movements: extractivism and water justice in El Salvador

ABSTRACT El Salvador’s 2017 national metal mining ban and contentious 2021 water law seemingly represent distinct cases of social movement victory and failure. However, this study deploys relational methodologies to examine how El Salvador’s anti-metal mining and water justice movements emerged together, became partially separated, and remained thoroughly entangled. The concept of social movement entanglement builds on and extends dominant notions of relationality in social movement studies by emphasizing processes of intra-relation, mutual constitution and becoming-with. Rather than study how separate movements interact, investigating entanglement highlights how social movements become separated and remain entangled through acts of material and discursive politics. Examining the entangled origins, mobilizations, and outcomes of El Salvador’s anti-metal mining and water justice movements shows how these movements were neither the same nor distinct. Salvadorans bearing the brunt of water injustices lived these movements as one struggle. However, to pass the historic metal mining ban required anti-mining activists to distance their social movement goals and discourses from the more politically contentious and legally complex water law. Vitally, the strategic separation of these movements led to their further entanglement, as the historic ban informed, reinforced, and legitimized transformations within the water justice movement. From their origins to their evolving presents, El Salvador’s water and mining politics have remained entangled. Such entanglements implicate social movement theory, methodology and praxis in El Salvador and beyond and center the power-relations that shape what counts as social movement success and failure, and whose interests and environments are worth fighting for.

Reconstruction of Historical Metal Backgrounds in Lacustrine Environments of China Using an Anodonta woodiana "Specimen Bank".

Anodonta woodiana samples from Xidong Water Works and Mashan in Taihu Lake, Yiyang near Dongting Lake, and Taiping Harbor in Gehu Lake preserved in a "specimen bank" established for the "Freshwater Mussel Watch" monitoring program were used to determine the historical metal backgrounds from different waters in the present study. The elements Co, Ni, Mo, Cd, Al, Cr, Mn, Fe, Cu, Zn, As, Ba, and Pb were determined using A. woodiana from four lacustrine sites. The results showed that Al, Cr, Mn, Fe, Cu, Zn, As, Ba, and Pb were all detected, whereas Co, Ni, Mo, and Cd were below the detection limits of 0.0165, 0.0106, 0.0189 and 0.0182µg kg- 1, respectively. In particular, A. woodiana was noted to be an unusual Mn hyperaccumulator (ranged from 5124.09 to 13015.47µg g- 1). The results of discriminant analysis showed that the four water samples could be accurately separated. This difference has the potential to infer the background difference of heavy metal pollution in different lacustrine habitats.

Biocleaning of historical metal artworks: innovative green gels amended with microbial derivatives

The research study is aimed to design innovative bio-gel formulations able to tackle altered historical metal artworks in a green and sustainable perspective. The target of the research is the removal of undesired or altered materials of both inorganic (i.e., corrosion and tarnishing) and organic nature (i.e., protective coatings). The designed gel systems are initially assessed on mock-ups. Iron-, copper- and silver-based substrates, chosen as mostly present in historical metal collections, are chemically aged to form corrosion on the surface. Alternatively, they are coated with organic protectives (i.e., acrylic and nitrocellulose varnish) that are mostly used for indoor metal care. After multi-modal analytical assessment to check the action and safety of the gels on the metal mock-ups, the developed solutions are applied on real cases, thanks to the strong and fruitful collaboration with curators and conservators of metal artworks.

Quantitative analysis of copper alloys by means of portable X-ray fluorescence: A comparison between analysis of shavings and surfaces

The investigation of the alloy composition is a key point for studying archaeological and historical metal artefacts. Portable X-ray fluorescence is the most commonly used technique to perform non-invasive alloy analysis. Nevertheless, quantitative results are usually not reliable when metal surface is covered by either corrosion or patination layers. In such cases, micro samples, representative of the bulk alloy, have to be taken. Shavings samples are a good compromise between representativeness and degree of invasiveness when the purpose of the analysis is to obtain accurate quantitative data. This work aims at evaluating and comparing accuracy and precision of X-ray Fluorescence quantitative data obtained by performing analysis on the surface and on shavings of certified reference materials. Results point out that quantitative data obtained from surface and shavings samples have comparable accuracy and precision if a suitable calibration model using certified reference materials in the same form, i.e. surface or shavings, is applied. Repeatability tests were also carried out using the same certified reference materials. Results proved repeatable within 5% for all the detected elements. Uncertainties are slightly higher for shavings with respect to surface measurements. Two case studies concerning an archaeological and a Renaissance bronze artefacts are also discussed.

A circular economy approach to drinking water treatment residue management in a catchment impacted by historic metal mines

Drinking water treatment residues (DWTR) from mining areas which remove and contain potentially toxic elements (PTE) could still potentially be used as a soil amendment to restore contaminated sites in the same catchment, thus eliminating waste and reducing the chemical and physical mobility of the pollutants. To assess this restorative and regenerative approach to DWTR management, field and pot trials were established with soils from a historic Pb–Zn mine site in the North East of England, amended with either local DWTR or the nearest available municipal green waste compost (GWC). Soils from the mine site were found to have very low levels of nutrients and very high levels of PTE (Pb and Zn > 13, 000 mg/kg). The perennial grass species Phalaris arundinacea, known for many ecosystem service benefits including soil stabilization, was used throughout this study. The application of the BCR sequential extraction to soils amended with the DWTR in the pot trials found a significant decrease in the bioavailability of Pb and Cu (p < 0.05) after plant growth when compared with an unamended control. The field trial involved 648 pre-grown grass plants planted-out into mine soils amended with either DWTR, GWC or a mixture (MIX) of the two, all at rates of 25–30% w/w. Both amendments and the MIX had significant positive effects on biomass production compared to the unamended control in the following order GWC > MIX > DWTR (p < 0.05). Results of the elemental analysis of biomass from the field trial were generally ambiguous and did not reflect the decreased bioavailability noted in the pot trials using the BCR procedure. Pot trials, however, showed increases in plant growth and decreases in concentrations of Cr, Cu, Pb and Zn in above ground biomass following the application of both amendments. Further work should involve the testing of a mixture of DWTR and other soil amendments to enhance plant growth. The success of these trials should provide confidence for those working in drinking water treatment and catchment management to reuse the waste residues in a circular economy and a sustainable way that could improve water quality over time.

Are crucible steel ingots isotopically homogenous? AMS radiocarbon measurements on ingots from Telangana, India

Radiocarbon analysis is increasingly used to directly date archaeological and historical metal objects, ranging from low-carbon bloomery iron to steel and cast iron. However, little is known about the isotopic homogeneity of iron-carbon alloys, particularly relating to the formation of primary cementite during crystallisation. Here, we present 14C measurements for five crucible steel ingots and one crucible steel object from Telangana in south-central India. Two of the ingots were analysed twice. The results show a very wide scatter of 14C dates, far exceeding the expected age range for this assemblage. The repeat analysis of one of the ingots gave also widely different results, indicating a fundamental problem with the 14C analysis of crucible steel. We discuss the various factors that could have influenced the measured isotopic values, including variability in raw material, sampling contamination, and fractionation during the cleaning of the metal in hot acid leading to excessive sample mass losses prior to the extraction of carbon from the metal. We argue that mass-dependant fractionation of the different carbon isotopes between austenite and cementite during solidification of the ingot, and subsequent selective dissolution of one metal phase over the other, led to a distortion of the 14C signature to seemingly older ages. We recommend further research to explore the compound-specific isotopic signature of high-carbon iron alloys and the effect of selective corrosion on such material, to reduce potential errors in 14C dating of steel and cast iron.

Isotope and trace element compositions of silver-bearing ores in the Balkans as possible metal sources in antiquity

Ore deposits in the Balkan Peninsula were intensively mined for silver and other metals in the Roman and medieval periods. Coinage mainly issued by tribal groups between the early 5th and the end of the 3rd century BCE provides indirect evidence that silver extraction predates the Roman conquest of the region. However, identification of centers of past metal production and reconstruction of large-scale silver fluxes can only be achieved using a comprehensive geochemical database of potential ores. Here, we present high-precision Pb–Ag–S isotope data and trace element systematics for 128 ore samples from 36 mineralizations from the Balkans as well as one semi-reacted ore from a settlement site (=archaeological sample) and one andesite analyzed as a whole-rock and as a K-feldspar separate. Each ore site was selected for its geological characteristics and documented or assumed historical and/or archaeological significance.The reported data reconstruct the formation of ore bodies from large pre-existing Pb stocks derived from upper crustal sources, modified by tectonic and metasomatic processes, and eventually remobilized by magmatic activity. Lead isotope maps establish distinct isotopic domains which are linked to geological characteristics and enable an enhanced assessment of potential metal sources in provenance studies. Silver isotopes underscore the importance of hypogene ores of hydrothermal origin comprising galena or sulfosalt minerals as the main silver carrier phases and they can circumscribe ore deposits to those actually used as bullion sources of ancient coinage. We show that the Ag isotope signatures and the silver content of the argentiferous galena-rich ores in the Kopaonik and Zletovo districts (Serbia, Kosovo, and North Macedonia), combined with field evidence for historical metal production and geographical considerations, make them the most likely sources of silver which could have been used for coinage issued by mints in the interior of the Balkans.

Determining dangerous chemicals on the surface of metallic historical artefacts

The problem is to determine the threat of chemical damage to a person upon his contact with historical artifacts from metals. For this purpose, experimental studies of the process of accumulation of chemicals on the surface of historical metal products were carried out. The objects of this study were 3 samples of historical cold weapons selected from the museum fund, as well as samples from modern sheet steel. The blades of museum objects were rubbed with a special ash-free swab, which was burned, and the chemical composition of the residue was determined. This makes it possible to obtain data on compounds from a significant surface area. A list of chemical elements that accumulate on the surface of metallic historical artifacts over time has been established. Theoretically, the possibility of the appearance on the surface of historical artifacts made of iron of such chemical elements as Mercury, Barium, Stibium, Phosphorus, Plumbum (Lead), Thallium, Chromium, Selenium, Cadmium has been theoretically proven. This can pose a threat to the health of museum workers and collectors who are in daily contact with such items. The results of the experiment are provided with samples of modern steel, which, in order to accelerate the process of elimination of impurity elements, warmed up for 3 hours in a muffle furnace at a temperature of 700 °C. The surface of these samples was studied using an electron microscope, and local emission analysis of the chemical composition was carried out. The obtained results confirm the process of elimination of ions of individual chemical elements from the metal in the process of its heating. We can observe the release of Al, Si, S, K, Ca, Cu ions to the surface. Based on the results obtained, plots are built that describe the change in the chemical composition of the metal surface throughout the history of existence. The use of the author's method of testing makes it possible to study the problem of safety of handling historical monuments in general. The results of the study are important for establishing the authenticity of metallic historical artifacts and assessing possible risks in contact with them.

Uptake of lead and zinc from soil by blackberry plants (Rubus fruticosus L. agg.) and translocation from roots to leaves

• Pb and Zn in soil ofa the Innerste floodplain exceed precautionary limits. • Concentrations of Pb and Zn in soils and blackberries are positively correlated. • Uptake and translocation of Pb and Zn are reduced at higher soil levels. • R. fruticosus is a useful bioindicator but unsuited for phytoremediation. Heavy metals transported by rivers are deposited in sediments and floodplains, and floodplain soils act as both sinks and sources of these metals. The Innerste River is contaminated by historical metal ore mining, processing, and smelting in the Harz Mountains (Germany). Our study compared the uptake of lead (Pb) and zinc (Zn) in wild blackberries ( Rubus fruticosus L. agg.) growing within and outside the Innerste floodplain in a downstream area. The potential of blackberries as bioindicators and for phytoremediation of soils polluted by Pb and Zn was assessed based on bioconcentration factors (BCF) and the intra-plant mobility of the two metals based on translocation (TF) factors. Concentrations of Pb and Zn were significantly higher in soils and blackberry plants from the Innerste floodplain compared to adjacent non-flooded area, while soil pH and organic matter content did not differ significantly between the two zones. Mean concentrations (mg/kg d.w.) of Pb (1457.2) and Zn (1365.2) in the regularly flooded soils far exceeded the precautionary limits of the German Federal Soil Protection and Contaminated Sites Ordinance. Concentrations of both heavy metals in blackberry roots and leaves increased with their levels in soil. Except for BCF Root Pb, BCFs and TFs decreased exponentially with increasing heavy metal concentration in soil and roots, respectively. This indicates that the uptake of Pb and Zn by R. fruticosus and their translocation within the plant are reduced at higher soil levels of both heavy metals. BCF < 1 were determined for both heavy metals and a TF < 1 for Pb. Only blackberries growing outside the floodplain showed a TF > 1 for Zn. Our results indicate that blackberries can be used as bioindicators of soil contamination by Pb and Zn. Regarding their uptake characteristics, blackberries constitute excluders rather than accumulators, and are thus unsuited for phytoremediation.

Tuning the electronic structure and hydrophilicity of Prussian-blue type catalysts by incorporation of alklypyrazinium bromides, for enhanced activity

Prussian blue (PB) type material, a historical metal coordination material, is widely used in batteries, catalyst, and for energy storage. However, the scarcity of active sites and its immutable structure limit further applications. Herein, we propose a ligand substitution strategy to tune the electronic structure and hydrophilicity of the PB-type material, involving Fe(CN)5 as a cyanide precursor, to catalyze epoxidation of olefins. The catalytic performance can be significantly promoted for styrene oxide in the presence of a CoFe PB analog that includes decylpyrazinium bromide (named CoFe-10). Kinetic studies on styrene epoxidation with CoFe-10 show a low activation energy of 27.2 kJ/mol. In addition, mechanistic investigation, coupled to electron paramagnetic resonance (EPR) measurements, suggests that the CoOOC(CH3)3 adduct is the reactive species for epoxidation of styrene. This study provides an effective strategy to synthesize unprecedented PB-type material and extend its application.

Factors influencing lead, mercury and other trace element exposure in birds from metal mining areas

Non-ferrous metal mining is considered one of the largest sources of toxic metal released to the environment and may threaten ecosystems, notably biota. We explored how birds that inhabit non-ferrous metal mining sites are exposed to mercury, lead, and other trace elements by analyzing their feathers and verifying which factors may influence element concentrations in feathers. We sampled a total of 168 birds, representing 26 species, with different feeding habits and migration patterns in a non-polluted reference site and two historical metal mining areas: Almadén, which is considered one of the most heavily mercury-contaminated sites worldwide, and the Sierra Madrona mountains where lead has been mined since ancient times. The quantification of aluminum (Al), arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), selenium (Se), thorium (Th), thallium (Tl), uranium (U), vanadium (V) and zinc (Zn) was performed by inductively coupled plasma mass spectrometry (ICP-MS). Feather analysis revealed contamination by Hg and Pb, in Almadén and Sierra Madrona, respectively. We found that granivorous birds had the lowest feather Hg levels compared to those found in omnivorous, insectivorous, and piscivorous species, whereas feather Pb was about twice as high in granivores and omnivores, than in insectivorous and piscivorous birds. We also found differences among study sites in 13 elements and confirmed the influence of feather age, migratory patterns of the birds, and external deposition of elements, on metal concentrations in the feathers. Our results highlight that despite the cessation of metal mining in the study areas, local avifauna are being exposed to Hg and Pb from abandoned mines and old tailings sites, indicating that appropriate measures are needed to protect biota from overexposure to these toxic metals.

Antlers of European roe deer (Capreolus capreolus) as monitoring units to assess lead pollution in a floodplain contaminated by historical metal ore mining, processing, and smelting in the Harz Mountains, Germany

Lead concentrations in hard antlers of adult European roebucks (Capreolus capreolus) were analyzed to assess lead exposure of roe deer roaming the floodplain of the Innerste River, a river system contaminated due to historical metal ore mining, processing, and smelting in its upper reaches. Antler lead concentrations of roebucks culled in the period 1939–2018 within or close to the Innerste floodplain ranged between <0.17 mg Pb/kg (limit of detection) and 51.5 mg Pb/kg (air-dry weight). Median lead concentration in antlers of roebucks culled within the floodplain was 11.1 mg Pb/kg, compared to 2.3 mg Pb/kg in antlers of bucks culled in the floodplain vicinity (P < 0.01). Sampling year had no significant effect on antler lead concentrations (P = 0.748). Lead isotope ratios of antlers from the Innerste downstream area (206Pb/207Pb: 1.179–1.181; 208Pb/206Pb: 2.083–2.085) fell within the range of those reported for hydrothermal vein deposits from the upper catchment area of the Innerste River in the Harz Mountains. Our study demonstrates the long-lasting impact of the historical metal ore mining, processing, and smelting in the Harz Mountains on lead pollution in floodplains of rivers draining this area and the lead exposure of wild herbivores inhabiting the floodplains. Furthermore, it highlights the suitability of roe deer antlers for monitoring environmental lead levels and the usefulness of lead isotope signatures in antlers for source apportionment of lead pollution.

Historical records of trace metals in two sediment cores of Jiaozhou Bay, north China

To investigate the long-term effects of urbanization and industrialization on coastal trace metal contamination, two sediment cores, Q21 (representing 1965–2018) and Q23 (representing 1986–2018), collected from the adjacent coasts of the east old town and west new area of Qingdao were analyzed. Although the concentrations of As, Cd, Co, Cr, Cu, Ni, Pb, Sc, and Zn were higher in Core Q21, the increasing trends in their concentrations and contamination levels were more obvious in Q23, especially since the 2000s. Moreover, the urbanization rates of the new area (1978–2017) were significantly positively correlated with the historical metal concentrations in Q23. Affected by the rapid socio-economic development in the new area, the combined excessive concentrations of the eight metals (excluding Sc) increased faster in Q23 (0.14–78.4 mg/kg) than Q21 (0.58–45.3 mg/kg). Overall, the sediment Core Q23 experienced higher trace metal contamination and ecological risks than Core Q21.

Variegated extractivism: Rescaling El Salvador's anti-metal mining and pro-extractive politics

Latin America's commitment to extractive development unifies governments of all political stripes. Recent scholarship describes this common will to extract as a continental extractive consensus. Yet empirical research increasingly shows exceptions to this consensus, citing mining bans, moratoriums and other restrictions to extractive development. Through an examination of El Salvador's historic metal mining ban in 2017, and ongoing commitment to non-metal mining extractivism, this paper examines how these seemingly contradictory trends emerge together. A cross-sectoral analysis of gold, limestone, and sugarcane extractive developments unearths El Salvador's variegated (anti)extractive geographies and highlights the scalar politics inherent in extractive politics. Rather than contradictory, the extractive consensus and alternatives to extractivism mutually constitute one another in El Salvador. Beyond adding theoretical complexity to understandings of extractive development and socio-ecological change more broadly, this analysis highlights the continued struggle over water, livelihoods, and meanings of extractivism in El Salvador.

Temporal evolution of acid mine drainage (AMD) leachates from the abandoned tharsis mine (Iberian Pyrite Belt, Spain)

Acid mine drainage (AMD) due to the mining of sulfide deposits is one of the most important causes of water pollution worldwide. Remediation measures, especially in historical abandoned mines, require a deep knowledge of the geochemical characteristics of AMD effluents and metal fluxes, considering their high spatial and temporal evolution, and the existence of point and diffuse sources with a different response to rainfall events. This study investigates the temporal variations and hydrogeochemical processes affecting the composition of main AMD sources from the Tharsis mines (SW Spain), one of most important historical metal mining districts in the world. To address this, a fortnightly-monthly sampling was performed during two years in the main AMD sources and streams within the mine site covering different hydrological conditions. A seasonal pattern was observed linked to hydrological variations; higher pollutant concentrations were observed during the dry season (maximum values of 4,6 g/L of Al, 11,8 g/L of Fe, and 67 g/L of sulfate) and lower ones were observed during the rainy periods. Stream samples exhibited a negative correlation between electrical conductivity (EC) and flow, while positive values were observed in AMD sources, where groundwater fluxes were predominant. High flow also seems to be the main driver of Pb fluxes from AMD sources, as the concentration of Pb in waters increased notably during these events. The precipitation of secondary Fe minerals may limit the mobility of As and V, being retained in the proximity of mine sites. The concentration of Zn in waters seems to be controlled by the original grade in the metal deposit from which the waste is generated, together with the age of these wastes. The pollutant load delivered by the Tharsis mines to the surrounding water courses is very high; e.g., mean of 733 ton/yr of Al or 2757 ton/yr of Fe, deteriorating the streams and reservoirs downstream.

Heavy metal concentrations in floodplain soils of the Innerste River and in leaves of wild blackberries (Rubus fruticosus L. agg.) growing within and outside the floodplain: the legacy of historical mining activities in the Harz Mountains (Germany)

We studied heavy metal levels in floodplain soils of the Innerste River in northern Germany and in the leaves of wild blackberries (Rubus fruticosus L. agg.) growing within and in adjacent areas outside the river floodplain. Heavy metal contamination of the Innerste floodplain is a legacy of historical metal ore mining, processing, and smelting in the Harz Mountains. The heavy metal (Cd, Pb, Zn, Cu, Ni, and Cr) contents of previously studied soil samples from eleven floodplain sites along the Innerste River were re-analyzed statistically, and the levels of these metals in blackberry leaves were determined at five sites. Mean concentrations in the floodplain soils were elevated by factors of 4.59 to 28.5 for Cd, 13.03 to 158.21 for Pb, 5.66 to 45.83 for Zn, and 1.1–14.81 for Cu relative to the precautionary limits for soils stipulated by the German Federal Soil Protection and Contaminated Sites Ordinance. Cadmium, Pb, Zn, Cu, and Ni levels in floodplain soils decreased markedly downstream, as did the concentrations of Cd, Zn, and Ni in the leaves of blackberries from within the floodplain. Levels of Cd, Pb, and Zn in leaves of blackberries from within the floodplain significantly exceeded those of specimens from outside the floodplain. The findings of our study highlight the potential of wild blackberry as a biomonitor of soil pollution by Cd, Pb, and Zn and corroborate the massive heavy metal contamination of floodplain soils along the Innerste River observed in previous studies.

Nondestructive Microanalysis of Thin-Film Coatings on Historic Metal Threads.

A new standards-based scanning electron microscopy with the energy-dispersive X-ray spectrometry (SEM-EDS) quantification method was used to analyze the thin-film coating of an 18th century French textile decorated with metal threads in variable pressure conditions. This analytical technique can allow for nondestructive quantitative characterization of the near surface of cultural heritage objects small enough to be placed in an SEM chamber that may contain corrosion products, without applying a conductive coating. A multivoltage analysis consisting of measurements taken at a series of electron beam energies was obtained and input into a film thickness and composition (FTC) computational model to characterize a layered Au on Ag reference material, in addition to a historic metal thread. Using the FTC computation, the thread coating was determined to be an alloy ≈ 80% Au 20% Ag on a nominally pure Ag substrate, and this composition matches a minimum gold standard allowed for goods around the time of manufacture. The computed gilding thicknesses range from single digit nm to 300 nm depending upon surface inhomogeneities formed during the production of the thread. Interaction volumes and X-ray spectra generated by Monte Carlo modeling are consistent with the measured gilding thicknesses and compositions. Validation of the FTC-computed gilding composition and thickness variations were obtained by cross-sectional analysis.