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PubMed2003

Electrochemical metal speciation analysis of chemically heterogeneous samples: the outstanding features of stripping chronopotentiometry at scanned deposition potential.

The application of depletive stripping chronopotentiometry at scanned deposition potential (SSCP) to metal ion speciation analysis of chemically heterogeneous complex systems is described. In this electroanalytical stripping technique, metal which is accumulated in the electrode during the deposition step is quantitatively reoxidized during the detection step. SSCP is able to provide an unambiguous measure of heterogeneity that is not attainable by other nondepletive electroanalytical stripping techniques that measure only a proportion of the accumulated metal. SSCP data are not affected by the secondary interferences that plague conventional electrochemical techniques, that is, induced metal adsorption and insufficient ligand excess during stripping. Furthermore, the effect of heterogeneity, as manifested in flattening of the SSCP wave, can be distinguished from that of electrochemical irreversibility. Data are presented for complexation of Cu(II), Pb(II), and Cd(II) by several humic fractions: distinct heterogeneity differences are observed.

Adsorption↗
PubMed2003

Voltammetry assisted by multivariate analysis as a tool for speciation of metallothioneins: competitive complexation of alpha- and beta-metallothionein domains with cadmium and zinc.

Multivariate Curve Resolution by Alternating Least Squares (MCR-ALS) is applied to voltammetric data obtained in the study of competitive complexation of Zn(II) and Cd(II) by alpha- and beta-domains of metallothionein (MT). The application of MCR-ALS allows the estimation of both the voltammograms and the concentration profiles associated with each electrochemical process. The complexity of the voltammograms obtained in titrations of the alpha- or beta-domains of MT with Cd(II) and later Zn(II) (or vice versa) prevents their direct interpretation using traditional electrochemical methods. But when MCR-ALS is applied, voltammograms can be interpreted rather satisfactorily in both qualitative and quantitative terms. MCR-ALS showed the formation of Cd2Znbeta dom and Cd3Znalpha dom complexes when both metals were competitively added. A method based on the combined use of voltammetry and some chemometric techniques is proposed. It can be useful for the metal speciation of environmentally relevant natural ligands.

Cadmium↗
PubMed2004

Influence of natural organic matter source on copper speciation as demonstrated by Cu binding to fish gills, by ion selective electrode, and by DGT gel sampler.

Rainbow trout (Oncorhynchus mykiss, 2 g) were exposed to 0-5 microM total copper in ion-poor water for 3 h in the presence or absence of 10 mg C/L of qualitatively different natural organic matter (NOM) derived from water spanning a large gradient in hydrologic residence time. Accumulation of Cu by trout gills was compared to Cu speciation determined by ion selective electrode (ISE) and by diffusive gradients in thin films (DGT) gel sampler technology. The presence of NOM decreased Cu uptake by trout gills as well as Cu concentrations determined by ISE and DGT. Furthermore, the source of NOM influenced Cu binding by trout gills with high-color, allochthonous NOM decreasing Cu accumulation by the gills more than low-color autochthonous NOM. The pattern of Cu binding to the NOM measured by Cu ISE and by Cu accumulation by DGT samplers was similar to the fish gill results. A simple Cu-gill binding model required an NOM Cu-binding factor (F) that depended on NOM quality to account for observed Cu accumulation by trout gills; values of Fvaried by a factor of 2. Thus, NOM metal-binding quality, as well as NOM quantity, are both important when assessing the bioavailability of metals such as Cu to aquatic organisms.

Animals↗
PubMed2004

Redox speciation of copper in rainwater: temporal variability and atmospheric deposition.

Copper speciation was determined in 68 rainwater samples collected in Wilmington, NC, from August 25, 2000, to September 24, 2002. Volume-weighted average concentrations of Cu(total), dissolved Cu(II), and dissolved Cu(I) were 5.3, 3.2, and 1.4 nM, respectively, with a significantly higher ratio of Cu(II)/Cu(I) in summer relative to winter events. The concentrations of all Cu species were higher in storms of continental origin relative to marine-dominated events, suggesting anthropogenic and/or terrestrial sources are important contributors of Cu in precipitation. Concentrations of strong Cu-complexing ligands were consistently lower than dissolved Cu concentrations, indicating a significant portion, but not all, of the dissolved Cu in rainwater is strongly complexed. A portion of these ligands, in addition to the sulfite and chloride in precipitation, may be Cu(I)-complexing ligands, which may explain the resistance of Cu(I) against oxidation in rainwater. Using our rainwater concentration data along with other published rainwater Cu concentrations and an estimate for total global annual rain, the total global flux of Cu removed from the atmosphere via wet deposition is 150 x 106 kg yr(-1). This represents complete removal of the estimated Cu input into the troposphere and indicates essentially all Cu released into the global atmosphere is removed by rain.

Air Pollutants↗
PubMed2003

Arsenic speciation and reactivity in poultry litter.

Recent U.S. government action to lower the maximum concentration levels (MCL) of total arsenic (As) (10 ppb) in drinking water has raised serious concerns about the agricultural use of As-containing biosolids such as poultry litter (PL). In this study, solid-state chemical speciation, desorbability, and total levels of As in PL and long-term amended soils were investigated using novel synchrotron-based probing techniques (microfocused (micro) synchrotron X-ray fluorescence (SXRF) and micro-X-ray absorption near-edge structure (XANES) spectroscopies) coupled with chemical digestion and batch experiments. The total As levels in the PL were as high as approximately 50 mg kg(-1), and As(II/III and V) was always concentrated in abundant needle-shaped microscopic particles (approximately 20 microm x 850 microm) associated with Ca, Cu, and Fe and to a lesser extent with S, Cl, and Zn. Post-edge XANES features of litter particles are dissimilar to those of the organo-As(V) compound in poultry feed (i.e., roxarsone), suggesting possible degradation/transformation of roxarsone in the litter and/or in poultry digestive tracts. The extent of As desorption from the litter increased with increasing time and pH from 4.5 to 7, but at most 15% of the total As was released after 5 d at pH 7, indicating the presence of insoluble phases and/or strongly retained soluble compounds. No significant As accumulation (< 15 mg kg(-1)) was found in long-term PL-amended agricultural surface soils. This suggests that As in the PL may have undergone surface and subsurface transport processes. Our research results raise concerns about long-term PL amendment effects on As contamination in surrounding soil-water environments.

Absorptiometry, Photon↗
PubMed2003

Congener-based Aroclor quantification and speciation techniques: a comparison of the strengths, weaknesses, and proper use of two alternative approaches.

This paper compares two previously published methods, an Aroclor estimation method and a mixing model method, that relate Aroclor contamination to congener specific data in environmental samples. The Aroclor estimation method, which is consistent with U.S. EPA Method 8082, uses a limited set of congener specific data to estimate Aroclor contributions to the sample, while the mixing model method uses the full congener data to model sample compositions as linear combinations of Aroclors. The performance of these methods are compared, using 181 samples at a variety of trophic levels, in terms of (a) total PCB concentrations, (b) compositional modification levels from original Aroclors, and (c) determination of the Aroclor mixture or mixtures best describing the sample (Aroclor speciation). We find that the two methods agree in all three terms for samples of low trophic level, but disagree for samples of higher tropic levels. Most significantly, the comparison reveals systematic overestimation of total PCB content by the Aroclor estimation method for samples at high trophic levels. The implication is that Aroclor determinations using persistent congeners cannot reliably be used as surrogates for total PCB concentration. The strengths and weaknesses of each method are detailed.

Animals↗
PubMed2003

Accumulation of copper and zinc in periphyton in response to dynamic variations of metal speciation in freshwater.

Although the free ion activity model (FIAM) has been well-established in laboratory studies, there remains the need for field data in order to validate the applicability of this model in natural systems. The objective of this study was to investigate the response of copper and zinc accumulation in periphyton to short-term variations in metal concentration and speciation in freshwater. During heavy rain events, dissolved Cu in the Furtbach stream increased from 40 to 118 nM, while dissolved Zn increased from 45 to 147 nM due to the release of metals from contaminated sediments. Increases in free copper and free zinc ions in the water (from 10(-14) to 10(-11.5) M for Cu2+; from 1 to 15 nM for Zn2+) were observed during the onset of heavy rain events. Periphytic algae collected from artificial substrates had an intracellular copper content (0.2-2.8 micromol/g dry weight (dw)) that varied as a function of the exchangeable copper in the water (labile form) rather than the free Cu2+. Intracellular zinc content (1.5-8.0 micromol/g dw) was found to follow the same trend as the free zinc ion concentration. Adsorbed Cu and Zn on periphyton showed a very dynamic response to variations in dissolved metal concentration. Different concentrations of dissolved manganese during the two time periods may affect the accumulation of zinc and copper by competition for metal uptake.

Copper↗
PubMed2004

Speciation of zinc in municipal solid waste incineration fly ash after heat treatment: an X-ray absorption spectroscopy study.

Fly ash is commonly deposited in special landfills as it contains toxic concentrations of heavy metals, such as Zn, Pb, Cd, and Cu. This study was inspired by our efforts to detoxify fly ash from municipal solid waste incineration by thermal treatment to produce secondary raw materials suited for reprocessing. The potential of the thermal treatment was studied by monitoring the evaporation rate of zinc from a certified fly ash (BCR176) during heating between 300 and 950 degrees C under different carrier gas compositions. Samples were quenched at different temperatures for subsequent investigation with X-ray absorption spectroscopy (XAS). The XAS spectra were analyzed using principal component analysis (PCA), target transformation (TT), and linear combination fitting (LCF) to analyze the major Zn compounds in the fly ash as a function of the temperature. The original fly ash comprised about 60% zinc oxides mainly in the form of hydrozincite (Zn5(OH)6(CO3)2) and 40% inerts like willemite (Zn2SiO4) and gahnite (ZnAl2O4) in a weight ratio of about 3:1. At intermediate temperatures (550-750 degrees C) the speciation underlines the competition between indigenous S and Cl with solid zinc oxides to form either volatile ZnCl2 or solid ZnS. ZnS then transformed into volatile species at about 200 degrees C higher temperatures. The inhibiting influence of S was found absent when oxygen was introduced to the inert carrier gas stream or chloride-donating alkali salt was added to the fly ash.

Air Pollution↗
PubMed2004

Effects of dissolved carbonate on arsenate adsorption and surface speciation at the hematite--water interface.

Effects of dissolved carbonate on arsenate [As(V)] reactivity and surface speciation at the hematite-water interface were studied as a function of pH and two different partial pressures of carbon dioxide gas [P(CO2) = 10(-3.5) atm and approximately 0; CO2-free argon (Ar)] using adsorption kinetics, pseudo-equilibrium adsorption/titration experiments, extended X-ray absorption fine structure spectroscopic (EXAFS) analyses, and surface complexation modeling. Different adsorbed carbonate concentrations, due to the two different atmospheric systems, resulted in an enhanced and/or suppressed extent of As(V) adsorption. As(V) adsorption kinetics [4 g L(-1), [As(V)]0 = 1.5 mM and I = 0.01 M NaCl] showed carbonate-enhanced As(V) uptake in the air-equilibrated systems at pH 4 and 6 and at pH 8 after 3 h of reaction. Suppressed As(V) adsorption was observed in the air-equilibrated system in the early stages of the reaction at pH 8. In the pseudo-equilibrium adsorption experiments [1 g L(-1), [As(V)]0 = 0.5 mM and I = 0.01 M NaCI], in which each pH value was held constant by a pH-stat apparatus, effects of dissolved carbonate on As(V) uptake were almost negligible at equilibrium, but titrant (0.1 M HCl) consumption was greater in the air-equilibrated systems (P(CO2) = 10(-3.5) atm) than in the CO2-free argon system at pH 4-7.75. The EXAFS analyses indicated that As(V) tetrahedral molecules were coordinated on iron octahedral via bidentate mononuclear ( 2.8 A) and bidentate binuclear (approximately equal to 3.3 A) bonding at pH 4.5-8 and loading levels of 0.46-3.10 microM m(-2). Using the results of the pseudo-equilibrium adsorption data and the XAS analyses, the pH-dependent As(V) adsorption under the P(CO2) = 10(-3.5) atm and the CO2-free argon system was modeled using surface complexation modeling, and the results are consistent with the formation of nonprotonated bidentate surface species at the hematite surfaces. The results also suggest that the acid titrant consumption was strongly affected by changes to electrical double-layer potentials caused by the adsorption of carbonate in the air-equilibrated system. Overall results suggest that the effects of dissolved carbonate on As(V) adsorption were influenced by the reaction conditions [e.g., available surface sites, initial As(V) concentrations, and reaction times]. Quantifying the effects of adsorbed carbonate may be important in predicting As(V) transport processes in groundwater, where iron oxide-coated aquifer materials are exposed to seasonally fluctuating partial pressures of CO2(g).

Adsorption↗
PubMed2004

Mercury speciation and microbial transformations in mine wastes, stream sediments, and surface waters at the Almadén Mining District, Spain.

Speciation of Hg and conversion to methyl-Hg were evaluated in mine wastes, sediments, and water collected from the Almadén District, Spain, the world's largest Hg producing region. Our data for methyl-Hg, a neurotoxin hazardous to humans, are the first reported for sediment and water from the Almadén area. Concentrations of Hg and methyl-Hg in mine waste, sediment, and water from Almadén are among the highestfound at Hg mines worldwide. Mine wastes from Almadén contain highly elevated Hg concentrations, ranging from 160 to 34,000 microg/g, and methyl-Hg varies from <0.20 to 3100 ng/g. Isotopic tracer methods indicate that mine wastes at one site (Almadenejos) exhibit unusually high rates of Hg-methylation, which correspond with mine wastes containing the highest methyl-Hg concentrations. Streamwater collected near the Almadén mine is also contaminated, containing Hg as high as 13,000 ng/L and methyl-Hg as high as 30 ng/L; corresponding stream sediments contain Hg concentrations as high as 2300 microg/g and methyl-Hg concentrations as high as 82 ng/g. Several streamwaters contain Hg concentrations in excess of the 1000 ng/L World Health Organization (WHO) drinking water standard. Methyl-Hg formation and degradation was rapid in mines wastes and stream sediments demonstrating the dynamic nature of Hg cycling. These data indicate substantial downstream transport of Hg from the Almadén mine and significant conversion to methyl-Hg in the surface environment.

Geologic Sediments↗
PubMed2005

Automated speciated mercury measurements in Michigan.

Automated speciated mercury measurements were made at a rural (Dexter, MI) and an urban (Detroit, MI) site in Michigan during selected times from 1999 to 2002 to assess the concentrations of elemental (Hg0), reactive gaseous (RGM), and particulate mercury (Hgp) in these environments. Here we present the first-ever reported values for RGM in Michigan. Median RGM concentrations were 2.21-2.93 pg m(-3) at Dexter and were 3-11 times higher in Detroit at 6.41-22.0 pg m(-3). Maximum RGM concentrations of 38.7 pg m(-3) and 270 pg m(-3) were observed in Dexter and Detroit, respectively. Measured RGM/Hg0 ratios were in the range of 0.04-11.60% indicating that at times RGM comprises greater than the currently held view of 5% of total gaseous mercury in the air. Well-pronounced diurnal patterns of RGM were observed at the rural site, whereas the urban site exhibited patterns that were influenced by nighttime emissions and regional transport. An analysis of RGM/Hgp ratios at the urban site when combined with trajectory analysis suggests that the site receives mercury inputs from both local and regional sources. Episodes of elevated ozone concentrations which were accompanied by increases in RGM concentrations were observed to occur in the late afternoon and overnight. These may be evidence of advection of ozone and RGM over long distances to the site.

Air Pollutants↗
PubMed2005

XAS study of iron and arsenic speciation during Fe(II) oxidation in the presence of As(III).

The speciation of As and Fe was studied during the oxidation of Fe(II)-As(III) solutions by combining XAS analysis at both the Fe and As K-edges. Fe(II) and As(III) were first hydrolyzed to pH 7 under anoxic conditions; the precipitate was then allowed to oxidize in ambient air for 33 h under vigorous stirring. EXAFS analysis at the As K-edge shows clear evidence of formation of inner-sphere complexes between As(III) and Fe(II), i.e., before any oxidation. Inner-sphere complexes were also observed when Fe became sufficiently oxidized, in the form of edge-sharing and double-corner linkages between AsIIIO3 pyramids and FeIIIO6 octahedra. XAS analyses at the Fe K-edge reveal that the presence of As(III) in the solution limits the polymerization of Fe(II) and the formation of green rust and inhibits the formation of goethite and lepidocrocite. Indeed, As(III) accelerates the Fe(II) oxidation kinetics and leads to the formation of nanosized Fe-As subunits of amorphous aggregates. These observations, rather than a presumed weaker affinity of As(III) for iron oxyhydroxides, might explain why As(III) is more difficult to remove than As(V) by aerating reducing groundwater.

Arsenic↗
PubMed2005

Spatial distribution and speciation of lead around corroding bullets in a shooting range soil studied by micro-X-ray fluorescence and absorption spectroscopy.

We investigated the spatial distribution and speciation of Pb in the weathering crust and soil surrounding corroding metallic Pb bullets in a shooting range soil. The soil had a neutral pH, loamy texture, and was highly contaminated with Pb, with total Pb concentrations in the surface soil up to 68 000 mg kg(-1). Undisturbed soil samples containing corroding bullets were collected and embedded in resin, and polished sections were prepared for micro-X-ray fluorescence (micro-XRF) elemental mapping and micro-X-ray absorption near edge structure (micro-XANES) spectroscopy. Bullet weathering crust material was separated from the metallic Pb cores and analyzed by powder X-ray diffraction analysis. Our results show a steep decrease in total Pb concentrations from the bullet weathering crust into the surrounding soil matrix. The weathering crust consisted of a mixture of litharge [alpha-PbO], hydrocerussite [Pb3(CO3)2-(OH)2], and cerussite [PbCO3], with litharge dominating near the metallic Pb core and cerussite dominating in the outer crust, which is in contact with the soil matrix. On the basis of these results and thermodynamic considerations, we propose that the transition of Pb species after oxidation of Pb(O) to Pb(II) follows the sequence litharge --> hydrocerussite --> cerussite. Consequently, the solubility of cerussite limits the activity of Pb2+ in the soil solution in contact with weathering bullets to < or =1.28 x 10(-6) at pH 7, assuming that the CO2 partial pressure (PCO2) in the soil is equal or larger than in the atmosphere (PCO2 > or = 0.000 35 atm).

Corrosion↗
PubMed2005

Use of diffusive gradients in thin films to measure cadmium speciation in solutions with synthetic and natural ligands: comparison with model predictions.

The performance of the technique of diffusive gradients in thin films (DGT) was characterized in well-defined systems containing cadmium with chloride and nitrate ions, simple organic ligands (nitrilotriacetic acid and diglycolic acid), and Suwannee river fulvic acid for the pH range 5-8. Cd was fully labile in all Cd, Cl-, and NO3- solutions tested (I= 0.1 and 0.01 M), even atvery low Cd concentrations (10 nM), consistent with there being no binding of Cd to the diffusive gel. Diffusion coefficients of Cd-nitritotriacetic acid (NTA) and Cd-diglycolic acid (DGA) species were measured and found to be ca. 25-30% lower than the equivalent coefficient for free metal ions. These values were used to calculate concentrations of labile Cd from DGT measurements in solutions of Cd with NTA or DGA. Cd-NTA and Cd-DGA species were found to be fully DGT-labile. DGT devices that used a diffusive gel with a reduced pore size, which retarded the passage of fulvic acid species through the gel, were used to estimate the proportion of Cd complexed by fulvic acid. These results were compared with predictions of the solution speciation from models with default parameter values. ECOSAT, incorporating the NICA-Donnan model, correctly predicted the magnitude of the binding and its pH dependence, while predictions from WHAM V (with humic ion binding model V) and WHAM 6 (with humic ion binding model VI) were less satisfactory at predicting the pH dependence. Reasonable fits to the data could be obtained from WHAM 6 when the effective binding constant log K(MA) was changed from 1.6 to 1.5, the value of deltaLK1 from 2.8 to 1.0 to minimize the dependence on pH, and the value of deltaLK2 from 1.48 to 1.0 to decrease the strength of the strong bidentate and tridentate binding sites.

Benzopyrans↗
PubMed2004

Modeling the effect of algal dynamics on arsenic speciation in Lake Biwa.

Algae reduce and methylate arsenate and the end product of the reaction is correlated to their growth rate. At slow growth rates, dimethylarsinate (DMA) is produced, and at fast growth rates arsenite (As(III)) is produced. Previous work has linked this phenomenon to the phosphorus luxury uptake mechanism of algae, and a model was developed for the process (Hellweger et al. Limnol. Oceanogr. 2003, 48, 2275). This paper presents the integration of that process model for arsenic transformation by algae into a full ecological model and application to Lake Biwa, Japan. The model application allows for a quantitative analysis of the field data, consistent with the process model and the ecological dynamics of the lake. The newly developed ecological model includes a variable phytoplankton composition, which is needed to simulate luxury uptake. This is in contrast to most existing ecological models, which typically assume a fixed "Redfield" composition. The model adequately reproduces the observed ecology of Lake Biwa, including the rapid uptake of phosphate by phytoplankton without immediate growth (luxury uptake) following lake overturn. The model also reproduces the observed arsenic speciation, including the gradual appearance of DMA during the summer and peaks in As(III) concentration at the onset of spring and fall algal blooms.

Arsenic↗
PubMed2005

Speciation of iron and sulfate in acid waters: aqueous clusters to mineral precipitates.

Acid mine drainage (AMD) contaminates surface water bodies, groundwater, soils, and sediments at innumerable locations around the world. AMD usually originates by weathering of pyrite (FeS2) and is rich in Fe and sulfate. In this study, we investigated speciation of FeII, FeIII, and SO4 in acid waters by Fourier transform infrared and X-ray absorption spectroscopy. The molalities of sulfate (15 mmol/ kg) and iron (10, 20, and 50 mmol/kg), and pH (1, 2, and 3) were chosen to mimic the concentration of ions in AMD waters. Sulfate and FeII either associate in outer-sphere complexes or do not associate at all. In contrast, sulfate interacts strongly with FeIII. The predominating species in FeIII-SO4 solutions are hydrogen-bonded complexes; inner-sphere complexes account only for 10+/-10% of the total sulfate. Our results show that the mode of interaction between FeIII and sulfate is similar in aqueous phase and in nanocrystalline precipitate schwertmannite (approximately FeO(OH)3/4(SO4)1/8). Because of this similarity, schwert-mannite should be the phase that controls solubility and availability of FeIII, SO4, and indirectly also other components in the AMD solutions.

Chemical Precipitation↗
PubMed2004

Influence of the sea rush Juncus maritimus on metal concentration and speciation in estuarine sediment colonized by the plant.

Metal accumulation by Juncus maritimus and the role of this plant on the physical and chemical composition of sediments, from the Douro river estuary (NW Portugal), were investigated. The contents of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined (by atomic absorption spectrophotometry) in sediments, rhizosediments (those among plant roots and rhizomes), and different plant tissues (roots, rhizomes, leaves, and stems). Metal fractionation in sediments through sequential extraction was carried out and used for interpretation of sediment/J. maritimus interactions. Two estuarine sites with different characteristics were studied: site I displayed sandy sediment with lower organic matter and metals more weakly bound to it than site II sediment, which was muddy. At both sites, higher metal contents were observed in rhizosediments than in the surrounding sediment, but metals were more weakly bound to rhizosediment. Therefore, J. maritimus markedly influenced the sediments among its roots and rhizomes, changing metal distribution and speciation. Different patterns of both metal uptake and metal distribution among J. maritimus tissues were observed at the two sites. Plant bioaccumulation was only observed for Cd, Cu, and Zn, being similar for Cd atthe two sites and significantly higher for Cu and Zn (9 and 4 times higher, respectively) at site I. In conclusion, J. maritimus was shown to have potential for phytoextraction (or phytostabilization) of Cd, Cu, and Zn in estuarine environment. However, an eventual application of J. maritimus for this purpose will require a periodic removal of the plants together with their own rhizosediment.

Environmental Monitoring↗
PubMed2006

Chemical-thermal quantitative methodology for carbon speciation in damage layers on building surfaces.

The issue of environment protection, including the conservation of the monumental heritage worldwide, is related to atmospheric pollution, and its future therefore depends on air pollutant reduction. Carbonaceous particles emitted by combustion processes are the main factors responsible for the blackening of buildings. The identification and evaluation of the carbon species constituting the noncarbonate fraction of total carbon in damage layers, particularly in urban areas, are required in orderto investigate atmospheric deposition on building surfaces. Since noncarbonate carbon contains organic and elemental carbon originating from various human activities, its measurement and speciation are crucial to the protection and conservation of monuments and ancient masonry, playing an important role both in the proposal of mitigation strategies and in the definition of conservation treatments. The availability of a correct, accurate, and reproducible analytical method for a complete carbon balance is essential in studying the effects of atmospheric pollutants on the environment, including those affecting cultural heritage. A chemical-thermal methodology was set up, and its sensitivity, accuracy, repeatability, and reproducibility were tested on appropriate standard samples of composition similar to the black crusts on stones and mortars. The results indicate thatthe technique satisfactorily distinguishes among carbon species, particularly those of anthropogenic origin, allowing a reliable evaluation of their quantities in damage layers. In view of the difficulties encountered in applying the thermo-optical methods adopted for the measurement of carbon filters, the proposed methodology contributes to filling the current gap in suitable and reliable analytical procedures in the field of cultural heritage protection.

Air Pollution↗