Origin and Dynamics of Rare Earth Elements during Flood Events in Contaminated River Basins: Sr-Nd-Pb Isotopic Evidence.

In order to precisely quantify the contribution of anthropogenic activities and geogenic sources to the dissolved and suspended loads of rivers we have combined for the first time Rare Earth Element (REE) concentrations with Sr-Nd-Pb isotope ratios. We observed enrichments in Anthropogenic Rare Earth Elements (AREE) for dissolved (Gd) and suspended (Ce and Nd) loads of river water. During flood events, AREE anomalies progressively disappeared and gave way to the geogenic chemical signature of the basin in both dissolved and suspended loads. The isotopic data confirm these observations and shed new light on the trace elements sources. On the one hand, dissolved loads have peculiar isotopic characteristics and carry mainly limestone-derived and anthropogenic Sr and Nd as well as significant amounts of anthropogenic Pb. On the other hand, the results clearly indicate that anthropogenic contributions impact the suspended loads in all hydrological conditions. This study demonstrates that anthropogenic contributions to the river may change not only Pb but also Sr and Nd isotopic compositions in both dissolved and suspended loads. This is of importance for future provenance studies.

Optimisation and application of accelerated solvent extraction and flash chromatography for quantification of PCBs in tree barks and XAD-2 passive samplers using GC-ECD with dual columns.

An analytical method for the quantification of Polychlorinated biphenyls (PCBs) concentrations in XAD-2 passive air samplers (PAS) and tree barks collected close to the Rhine River between France and Germany was developed. This method used Accelerated Solvent Extraction (ASE) followed by a purification step by flash chromatography using a 4gr cartridge (3 g of silica gel and 1 g of 44% acidified silica) and analysis by GC-ECD with dual columns. Quantification (QL) and detection (DL) limits varied 0.5 from and 5.7 ng PAS(-1) and from 0.5 and 3.0 ng PAS(-1) respectively. For tree barks, quantification and detection limits were calculated for each congener on washed tree bark sample with a signal to noise ratio of 3:1 and 10:1 (corresponding to a LQ in the range of 1-4 ng per bark sample by congeners). Uncertainties on each congener concentration were calculated to be in the range of 3-20% XAD-2 passive samplers were field calibrated by using Hi-vol. Samplers. Sampling rates of 4.2, 11.5, 1.6, and 7.9 m(3) PAS(-1) d(-1) for tri-, tetra-, penta- hexa-PCBs, respectively were obtained and are comparable to those already obtained with PUF-PAS for gas phase only (gas/particle distribution was 90/10). Method was applied to real atmospheric samples collected by XAD-2 passive samplers and tree barks in the east of France.

Persistent organic pollutants in the atmosphere from urban and industrial environments in the Rhine Valley: PCBs, PCDD/Fs.

Polychlorinated biphenyls (PCBs) and polychlorinated dibenzodioxin and furan (PCDD/F) concentrations in the atmosphere were analysed using passive air samplers (PAS) close to the Rhine River between France and Germany. Collectors were placed in industrial, urban, rural and remote areas (Vosges Mountains) between March 2009 and August 2010, and the mean PCB concentrations (sum of 22 congeners) were 3.3, 3.9, 4.1 and 1.4 ng PAS(-1) day(-1), respectively. Two events during the sampling period were observed in April 2009 and February-March 2010 with the highest PCB concentrations found in the industrial area (19.6 ng PAS(-1) day(-1)). PCDD/F level were measured during these periods, and the maximum concentration observed was from 37.5 fg WHO PAS(-1) day(-1.)

Atmospheric pollution in an urban environment by tree bark biomonitoring--part I: trace element analysis.

Tree bark has been shown to be a useful biomonitor of past air quality because it accumulates atmospheric particulate matter (PM) in its outermost structure. Trace element concentrations of tree bark of more than 73 trees allow to elucidate the impact of past atmospheric pollution on the urban environment of the cities of Strasbourg and Kehl in the Rhine Valley. Compared to the upper continental crust (UCC) tree barks are strongly enriched in Mn, Ni, Cu, Zn, Cd and Pb. To assess the degree of pollution of the different sites in the cities, a geoaccumulation index I(geo) was applied. Global pollution by V, Ni, Cr, Sb, Sn and Pb was observed in barks sampled close to traffic axes. Cr, Mo, Cd pollution principally occurred in the industrial area. A total geoaccumulation index I(GEO-tot) was defined; it is based on the total of the investigated elements and allows to evaluate the global pollution of the studied environment by assembling the I(geo) indices on a pollution map.

Atmospheric pollution in an urban environment by tree bark biomonitoring - part II: Sr, Nd and Pb isotopic tracing.

The harmful effect of manmade particles on natural processes and human health is documented by a large number of studies showing a positive correlation between particulate matter (PM) concentration and health effects. Diminution of this health risk necessitates among others the precise knowledge of the particle sources, their physical and chemical properties and their dissemination in the environment. Pb isotope ratios have been successfully used during the past decades as tracers of anthropogenic Pb disseminated in the biosphere. Here we show that tree bark biomonitoring with lead (Pb), strontium (Sr) and neodymium (Nd) isotope ratios as tracers allow a thorough analysis of the impacts of industrial and other anthropogenic emissions on the urban environment. This is the first comprehensive multi-isotope tracer study of atmospheric pollution in an urban environment allowing to identify and to integrate the different plume paths of emissions in a digital map system. This innovative approach might become an important tool for environmental management and policy-making processes dealing especially with risks and surveillance of air quality in the urban environment.

Biotic and abiotic experimental identification of bacterial influence on calcium isotopic signatures.

In this study, we tested experimentally the influence of plant and bacterial activities on the calcium (Ca) isotope distribution between soil solutions and plant organs. Abiotic apatite weathering experiments were performed under two different pH conditions using mineral and organic acids. Biotic experiments were performed using either apatite or Ca-enriched biotite substrates in the presence of Scots pines, inoculated or not with the rhizosphere bacterial strain Bulkholderia glathei PML1(12), or the B. glathei PML1(12) alone. For each experiment, the percolate was collected every week and analyzed for Ca concentrations and Ca isotopic ratios. No Ca isotopic fractionation was observed for the different abiotic experimental settings. This indicates that no Ca isotopic fractionation occurs during apatite dissolution, whatever the nature of the acid (mineral or organic). The main result of the biotic experiments is the 0.22 ‰ (44)Ca enrichment recorded for a solution in contact with Scots pines grown on the bacteria-free apatite substrate. In contrast, the presence of bacteria did not cause Ca isotopic fractionation of the solution collected after 14 weeks of the experiments. These preliminary results suggest that bacteria influence the Ca isotopic signatures by dissolving Ca from apatite more efficiently. Therefore, Ca isotopes might be suitable for detecting bacteria-mediated processes in soils.

Air quality assessment by tree bark biomonitoring in urban, industrial and rural environments of the Rhine Valley: PCDD/Fs, PCBs and trace metal evidence.

Tree barks were used as biomonitors to evaluate past atmospheric pollution within and around the industrial zones of Strasbourg (France) and Kehl (Germany) in the Rhine Valley. The here estimated residence time for trace metals, PCBs and PCDD/Fs in tree bark is >10 years. Thus, all pollution observed by tree bark biomonitoring can be older than 10 years. The PCB baseline concentration (sum of seven PCB indicators (Σ(7)PCB(ind))) determined on tree barks from a remote area in the Vosges mountains is 4 ng g(-1) and corresponds to 0.36 × 10(-3)ng toxic equivalent (TEQ) g(-1) for the dioxin-like PCBs (DL-PCBs). The northern Rhine harbor suffered especially from steel plant, waste incinerator and thermal power plant emissions. The polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/Fs) concentrations analyzed in tree barks from this industrial area range between 392 and 1420 ng kg(-1) dry-weight (dw) corresponding to 3.9 ng TEQ(PCDD/Fs) kg(-1) to 17.8 ng TEQ(PCDD/Fs) kg(-1), respectively. Highest PCDD/F values of 7.2 ng TEQ kg(-1) to 17.8 ng TEQ kg(-1) have been observed close to and at a distance of <2 km southwest of the chemical waste incinerator. However, very close to this incinerator lowest TEQ dioxin-like PCB (TEQ(DL-PCB)) values of 0.006 ng TEQ g(-1) have been found. On the other hand close to and southwest and northeast of the steel plant the values are comparatively higher and range between 0.011 ng TEQ g(-1) and 0.026 ng TEQ g(-1). However, even stronger Σ(7)PCB(ind) enrichments have been observed at a few places in the city center of Kehl, where ΣDL-PCB values of up to 0.11 ng TEQ g(-1) have been detected. These enrichments, however, are the result of ancient pollutions since recent long-term measurements at the same sites indicate that the atmospheric PCB concentrations are close to baseline. Emissions from an old landfill of waste and/or great fires might have been the reasons of these PCB enrichments. Other urban environments of the cities of Kehl and Strasbourg show significantly lower Σ(7)PCB(ind) concentrations. They suffer especially from road and river traffic and have typically Σ(7)PCB(ind) concentrations ranging from 11 ng g(-1) to 29 ng g(-1). The PCB concentration of 29 ng g(-1) has been found in tree bark close to the railway station of Strasbourg. Nevertheless, the corresponding TEQ(DL-PCB) are low and range between 0.2 × 10(-3) ng TEQ g(-1) and 7 × 10(-3) ng TEQ g(-1). Samples collected near road traffic are enriched in Fe, Sb, Sn and Pb. Cd enrichments were found close to almost all types of industries. Rural environments not far from industrial sites suffered from organic and inorganic pollution. In this case, TEQ(DL-PCB) values may reach up to 58 × 10(-3) ng TEQ g(-1) and the corresponding V, Cr, Co, Ni, and Cd concentrations are comparatively high.

Identifying the origins of local atmospheric deposition in the steel industry basin of Luxembourg using the chemical and isotopic composition of the lichen Xanthoria parietina.

Trace metal atmospheric contamination was assessed in one of the oldest European industrial sites of steel production situated in the southern part of the Grand-Duchy of Luxembourg. Using elemental ratios as well as Pb, Sr, and Nd isotopic compositions as tracers, we found preliminary results concerning the trace metal enrichment and the chemical/isotopic signatures of the most important emission sources using the lichen Xanthoria parietina sampled at 15 sites along a SW-NE transect. The concentrations of these elements decreased with increasing distance from the historical and actual steel-work areas. The combination of the different tracers (major elements, Rare Earth Element ratios, Pb, Sr and Nd isotopes) enabled us to distinguish between three principal sources: the historical steel production (old tailings corresponding to blast-furnace residues), the present steel production (industrial sites with arc electric furnace units) and the regional background (baseline) components. Other anthropogenic sources including a waste incinerator and major roads had only weak impacts on lichen chemistry and isotopic ratios. The correlation between the Sr and Nd isotope ratios indicated that the Sr-Nd isotope systems represented useful tools to trace atmospheric emissions of factories using scrap metal for steel production.

Tracing of industrial aerosol sources in an urban environment using Pb, Sr, and Nd isotopes.

A comprehensive Pb-Sr-Nd isotope tracer study of atmospheric trace metal pollution has been performed in the urban environment of Strasbourg-Kehl. Filter dust of the principal pollutant sources (waste incinerators, thermal power plant and steel plant) and soot of car and ship exhausts have been analyzed. In addition tree barks (as biomonitors) and PM10 have been analyzed to trace and determine the distribution of the pollution in the environment. The industrial sources have highly variable epsilonNd values (-9.7 and -12.5 for incinerators and -17.5 for steel plant). Much higher epsilonNd values have been found for soot of car exhausts (-6 and -6.9). These high values make the Nd isotope system a powerful tool for the discrimination of traffic emissions but especially for the identification of diesel derived particles in the urban environment. The 206Pb/207Pb isotope ratios of gasoline are low (1.089) compared to diesel soot (1.159). The 26Pb/207Pb ratios of 1.151-1.152 for the steel plant and 1.152 for the solid waste incinerator are close to the Pb isotope ratio of diesel. The 87Sr/ 8Sr isotope ratios of the principal industrial sources vary significantly: 0.7095 for the domestic solid waste incinerator, 0.709 for the steel plant, and 0.7087 for car exhaust soot. PM10 aerosols collected in the urban center of Strasbourg show the influence of the pollutant sources at 3-7 km distance from the center. Most of the aerosols Pb isotopic compositions suggest Pb admixtures from at least three sources: a natural background and in function of the wind direction the domestic waste incinerator (S-wind) or the steel plant and the chemical waste incinerator (NE-wind). The traffic contribution can only be estimated with help of Nd isotopes. Therefore the clear identification of different pollutant sources in the urban environment is only possible by combining the three different isotope systems and is based on the fact that significant differences exist between the Pb, Sr, and Nd isotope ratios of the natural atmospheric background and pollutants containing Pb, Sr, and Nd of industrial origin with similar variable 206Pb/207Pb, 87Sr/ 86Sr, and 143Nd/144Nd.

Influence of bacteria on lanthanide and actinide transfer from specific soil components (humus, soil minerals and vitrified municipal solid waste incinerator bottom ash) to corn plants: Sr-Nd isotope evidence.

Experiments have been performed to test the stability of vitrified municipal solid waste (MSW) incinerator bottom ash under the presence of bacteria (Pseudomonas aeruginosa) and plants (corn). The substratum used for the plant growth was a humus-rich soil mixed with vitrified waste. For the first time, information on the stability of waste glasses in the presence of bacteria and plants is given. Results show that inoculated plant samples contained always about two times higher lanthanide and actinide element concentrations. Bacteria support the element transfer since plants growing in inoculated environment developed a smaller root system but have higher trace element concentrations. Compared with the substratum, plants are light rare earth element (LREE) enriched. The vitrified bottom ash has to some extent been corroded by bacteria and plant activities as indicated by the presence of Nd (REE) and Sr from the vitrified waste in the plants. (87)Sr/(86)Sr and (143)Nd/(144)Nd isotope ratios of plants and soil components allow the identification of the corroded soil components and confirm that bacteria accelerate the assimilation of elements from the vitrified bottom ash. These findings are of importance for landfill disposal scenarios, and similar experiments should be performed in order to better constrain the processes of microbially mediated alteration of the MSW glasses in the biosphere.

Formation of radioactivity enriched soils in mountain areas.

A field study was carried out in the Mercantour Mountains at 2200 m altitude to investigate the processes of soil enrichment in atmospheric Chernobyl (137)Cs. Soils with high (137)Cs activities have been collected in the pasture areas with frequently measured (137)Cs activity values of the order of 7000 Bq m(-2). At some single spots (about 6% of the studied area), activity in soils reached 300000 Bq m(-2), which represents 44% of the (137)Cs of the total area. Data further showed that spatial distribution of Cs depends widely on its origin: Chernobyl Cs is mainly concentrated in "enriched" soils, whereas older Cs and (241)Am fallout from nuclear weapons tests (NWTs) and natural atmospheric (210)Pb in soils is less heterogeneously distributed. In order to elucidate the processes which have led to the enrichment in Chernobyl (137)Cs in the Alps in May of 1986, we have studied the repartition of atmospheric (7)Be isotope (half-life=53.3 d) in the pasture compartments (soil, litter, grass, and snow). Snow (7)Be data give evidence that fallout enrichment is related to snow accumulation (snow drift). The transfer of beryllium occurs rapidly to the grass and litter, where the strongest pollutant accumulations were measured. However, (7)Be transport to the soil required more than 8 months.