Large Variation of Mercury Isotope Composition During a Single Precipitation Event at Lhasa City, Tibetan Plateau, China

AbstractThis study examined for the first time the Hg isotope composition in rain samples from a single precipitation event at Lhasa City (China) on the Tibetan Plateau, the “world's third pole”. Large variations of both mass-dependent fractionation (MDF, δ202Hg from -0.80‰ to -0.42‰) and mass-independent fractionation (MIF, Δ199Hg from 0.38‰ to 0.76‰) were observed, with the latter increasing with time. Our results demonstrated that the large variation of Hg isotope ratios likely resulted from mixing of locally emitted Hg and long-term transported Hg, which were characterized by different Hg isotope signatures and mainly leached by below-cloud scavenging and in-cloud scavenging processes, respectively. Our findings demonstrated that Hg isotopes are a powerful tool for investigating the dynamics of precipitation events and emphasized the importance of systematic monitoring studies of the chemical and isotope variability of Hg and other elements during rainfall events

Characterization of manufacturing-induced surface scratches and their effect on laser damage resistance performance of diamond fly-cut KDP crystal

Manufacturing-induced defects have drawn more and more attentions to improve the laser damage resistance performance of KDP crystal applied in high-power laser systems. Here, the morphology of surface scratches on diamond fly-cut KDP crystal is characterized and their effect on the laser damage resistance is theoretically and experimentally investigated. The results indicate that surface scratches could lower laser-induced damage threshold (LIDT) by modulating incident lasers and producing resultant local light intensifications. The induced maximum light intensity enhancement factors (LIEFs) are dependent on scratch shapes and dimensions. The diffraction effects originating from scratch edges are responsible for the strongest light intensification. Even for ultra-precision finished KDP surface with scratches that well satisfy the currently applied scratch/dig specification, the induced LIEFs are quite high, indicating that the actual defect dimension allowance should be amended and specified according to the defect-induced LIEFs. The effect of scratches on laser damage resistance is experimentally verified by the tested LIDT, which is approximately consistent with the simulation one. The morphologies of laser damage sites further confirm the role of scratches in lowering LIDT. This work could offer new perspective and guidance for fully evaluating the performance of ultra-precision manufactured optical materials applied in high-power laser facilities

Toxic metals in the environment- geochemical processes and health implications

Geochemical risk; harmful elements

Zn isotope measurements in freshwater and its use as a probe of anthropogenic contamination in the Seine River

International audienc

Cu Isotopic Composition in Surface Environments and in Biological Systems: A Critical Review

Copper (Cu) is a transition metal and an essential micronutrient for organisms, but also one of the most widespread toxic inorganic contaminants at very high content. The research on Cu isotopes has grown rapidly in the last decade. Hitherto, a large number of studies have been published on the theoretical fractionation mechanisms, experimental data and natural variations of Cu isotopes in variable environments and ecosystems. These studies reported a large variation of δ65Cu (−16.49 to +20.04‰) in terrestrial samples and showed that Cu isotopes could be fractionated by various biogeochemical processes to different extent. Several papers have previously reviewed the coupling of Cu and Zn isotope systematics, and we give here a tentative review of the recent publications only on Cu isotopesin variable surface repositories, animals and human beings, with a goal to attract much attention to research on Cu (and other metals) behaviors in the environment and biological systems

Zn isotopes in the suspended load of the Seine River, France: Isotopic variations and source determination

International audienceWe report Zn isotopic ratios (d66Zn) of river suspended particulate matter (SPM) and floodplain deposits (FD) from the Seine basin, France, with a precision < 0.05 per mil. A decrease in d66Zn from 0.30 per mil to 0.08 per mil is observed in SPM from the upstream to downstream parts of the fluvial system, associated with an increase in Zn concentration from 100 ppm to 400 ppm. The Zn/Al of SPM at the river mouth is up to five times greater than the Zn/Al of the natural background, and by normalizing to the later value we define a Zn enrichment factor. Suspended sediments from a temporal series of samples collected in Paris display a similar variation in d66Zn of between 0.08 per mil and 0.26 per mil, while showing an inverse relationship between the Zn enrichment factor and d66Zn. The amount of Zn transported as suspended load varies from 10% to 90%, as a function of increasing discharge. The d66Zn of SPM and the dissolved load are correlated, suggesting that adsorption processes are probably not the dominant process by which the Zn enrichment of SPM takes place. Instead, we interpret our data as reflecting the mixture of two main populations of suspended particles with distinct d66Zn. The first is characteristic of natural silicate particles transported by erosion processes to the river, while the second likely represents anthropogenic particles derived from wastewater treatment plants or combined sewer overflows. Based on isotopic ratios, we calculate that 70% of Zn in SPM of the Seine River in Paris is of anthropogenic origin

Dynamic of boron in forest ecosystems traced by its isotopes: A modeling approach

International audienceUnderstanding the factors that control the cycling of nutrients in terrestrial ecosystems is of fundamental importance given its role for example in nutrient availability to sustain forest productivity, and ultimately in soil carbon storage.In this paper, we developed a model to assess the dynamic of boron in forest ecosystems and to appraise how the impacts on boron cycling by internal or external factors should be reflected in the changes of its isotopic compositions across an ecosystem. Despite the scarcity of data, we tested this model on two case studies and were able to reproduce the distribution of boron isotopes between the different pools of these two contrasted ecosystems. The model shows a time dependency of the boron isotopic composition of the different biotic and abiotic compartments of the ecosystem. When the forest grows, a transient enrichment in the heavy isotope up to 20‰ relative to the values at steady-state is observed in the biomass and the soil solutions. The magnitude of this enrichment, and the return time to steady state, are sensitive to B supply and plant demand for boron. Responses of B dynamic to natural or anthropogenic disturbances is well reflected in the variations of the B isotopic compositions of the different pools that make B isotopes a good potential tracer of nutrient cycling and by extension make boron isotopes a promising proxy for tracing the global functioning of terrestrial biosphere at present and in the past

Behaviors of major and trace elements during single flood event in the Seine River, France

International audienceThis study examines for the first time the characteristics of suspended particulate matter (SPM) and geochemical behaviors of major and trace elements during one single flood event of the Seine River, France. Source contribution, dilution by silicates and carbonates are the main scenarios consecutively occurring during the flood event, as can be inferred from the geochemical behaviors for major and trace elements. This study confirms the importance of flood events for the flux of materials transported by rivers to the ocean and emphasizes the need of systematic studies on the chemical variability of elements transported during flood events