Arsenic mobilization processes in the red river delta, Vietnam : towards a better understanding of the patchy distribution of dissolved arsenic in alluvial deposits

The spatial variability of dissolved arsenic (As) concentrations in aquifers was studied near Ha Noi, Vietnam. The goal was to identify major geochemical, sedimentological and hydrochemical differences between high and low As regions. Also, the behaviour of As and other elements during sequential extractions was characterized with micro synchrotron XRF analysis. Based on the results a conceptual model was developed which could explain the current situation on site and in other affected areas

From cave to spring: Understanding transport of suspended sediment particles in a fully phreatic karst conduit using particle analysis and geochemical methods

Karst aquifers are vulnerable to contamination, especially in the context of heavy rainfall events. Contamination is often associated with turbidity that can originate from the soil zone, infiltrating surface waters or resuspension of previously deposited sediments within the aquifer. While turbidity events can be well monitored at karst springs, related information about the sediment origin and the spatiotemporal input function usually remain unknown. Thus, the mobility and attenuation of the particulate matter and associated pollutants can hardly be determined quantitatively. A tracer test with suspended cave sediments and solute tracers for comparison has hence been performed in a karst aquifer at the Blue Spring (Blautopf) in Southern Germany. The tracers were injected in the cave system, at the beginning of a fully phreatic karst conduit, and monitored at the spring after a travel distance of 1250 m. The particle-size distribution was monitored using a particle counter and sediment samples were filtered with 0.45-μm cellulose acetate filters. Particles on the filter were analysed for major and trace elements as well as rare earth elements (REE) by ICP-MS after acid digestion. Results show that (1) sediment particles were transported faster than solutes, which was interpreted as a transport in the main flow path of the conduit, whereas conservative tracers tend to diffuse into smaller fissures as well. (2) All measured particles sizes were transported at similar flow velocities. (3) A transport associated to sediment particles could be shown for all measured elements. This study presents a methodological improvement of comparative sediment tracer tests as well as deeper insights into particle and element transport processes in karst aquifers, originating from previously deposited cave sediment. Results provide deeper knowledge into transport processes of sediment-associated contaminants, such as heavy metals which may strongly be affected by the particle size. This knowledge contributes to a better management of karst water resources in the context of turbidity events

Correction to: Flow-through experiments on the interaction of sandstone with Ba-rich fluids at geothermal conditions

Abstract After publication of the article (Orywall et al. 2017), it has been brought to our attention that there are a number of errors. The authors have listed them below

On the Activity Enhancing Role of Iron Oxide for Noble Metal Oxidation Catalysts: A CVD-Based Study with Differently Structured Combinations of Pt and FeOₓ Coatings on Al₂O₃

With regard to the catalysis of oxidation reactions by noble metals, the addition of FeOx to an Al2O3-supported Pt catalyst is known to be energetically more favorable compared to only Pt. In this work, different process routes for the preparation of such Fe-promoted Pt/Al2O3 catalysts via atmospheric chemical vapor deposition (CVD) in a fluidized bed were explored. Specifically, the question of whether it would be advantageous to deposit the Fe before, along with, or after the Pt was addressed, and new information was obtained about the optimum FeOx–Pt interface and mixing ratio. Vapors of Trimethyl(methylcyclopentadienyl)platinum(IV) and/or Ethyl-ferrocene were injected into the bed from the top, permitting a quasi-lossless precursor operation and a very good control of the deposited metal, and hence of the catalyst structure. Samples could be extracted from the top while CVD was ongoing to obtain time-resolved data. The catalytic activity was determined through CO oxidation. The Fe-Pt mixing ratio was then varied for the most active deposition sequence, in order to identify an activity optimum generated by the minimum amount of Pt catalyst. When compared to pure Pt/Al2O3, the optimum catalyst consistently showed superior performance even after thermal stres

Microbial transformation of biogenic and abiogenic Fe minerals followed by in-situ incubations in an As-contaminated vs. non-contaminated aquifer

Contains fulltext : 234196.pdf (Publisher’s version ) (Open Access

Gain time to adapt: How sorghum acquires tolerance to salinity

Salinity is a global environmental threat to agricultural production and food security around the world. To delineate salt-induced damage from adaption events we analysed a pair of sorghum genotypes which are contrasting in their response to salt stress with respect to physiological, cellular, metabolomic, and transcriptional responses. We find that the salt-tolerant genotype Della can delay the transfer of sodium from the root to the shoot, more swiftly deploy accumulation of proline and antioxidants in the leaves and transfer more sucrose to the root as compared to its susceptible counterpart Razinieh. Instead Razinieh shows metabolic indicators for a higher extent photorespiration under salt stress. Following sodium accumulation by a fluorescent dye in the different regions of the root, we find that Della can sequester sodium in the vacuoles of the distal elongation zone. The timing of the adaptive responses in Della leaves indicates a rapid systemic signal from the roots that is travelling faster than sodium itself. We arrive at a model where resistance and susceptibility are mainly a matter of temporal patterns in signalling