Sampling and characterising groundwater nanoparticles in sub-oxic environments

Characterising nanoparticles is important for understanding physiochemical and biogeochemical processes occurring within groundwater bodies e.g. those impacted by the migration of leachates from waste storage sites as well as monitoring the use of engineered nanotechnology for pollution attenuation. While characterising nano-scale particles (both natural and engineered) within sub-oxic environments is a challenging task, it is critical for understanding pollution attenuation and migration within a number of different environments. The overall aim of this study was to develop a robust sampling and analytical methodology for characterising nanoparticles in sub-oxic environments using a range of complementary methods. This study has successfully sampled and characterised nano-scale particulate material in sub-oxic groundwaters within an alluvial floodplain aquifer impacted by a landfull plume. The integrity of the sample was maintained throughout the field and laboratory work to ensure that only nanoparticles representative of the sub-oxic environment were characterised. Nanoparticles from two pairs of nested boreholes were characterised by a number of state-of-the-art methods; atomic force microscopy (AFM), scanning electron microscopy (SEM), scanning transmisson electron microscopy (TEM) and field flow fractionation (FFF), to explore particle size distributions, morphology and surface chemistry. It is important to characterise nanoparticles in environmental contexts using multiple techniques as each method has its own benefits and limitations (Lead and Wilkinson 2006). As far as the authors are aware this is the first such study in the UK to isolate and characterise sub-oxic groundwater nanoparticles using these complimentary techniques. Groundwaters were found to have abundant iron and organic nanoparticles with diameters <30 nm. AFM results showed spherical nanoparticles with average diameters of ca 10 nm, while FFF with UV absorbance (254 nm) results indicated that smaller fulvic-like nanoparticles were present with average hydrodynamic diameters of ca. 1.5 nm. FFF with UV absorbance detection at 575 nm showed that another population of organic rich nanoparticles was present with larger hydrodynamic diameters (ca. 3 nm) in the groundwater at nest 26, but were not present in nest 28. These larger organic nanoparticles perhaps represent co-aggregated humic-like particles or another distinct type of organic matter. Scanning TEM analysis with energy-dispersive X-ray diffraction showed that Ca rich nanoparticles were present within the groundwater at a number of sites, and that P was associated with the surface of Fe rich particles in nest 28. Aeration of sub-oxic samples resulted in a dramatic shift in the nanoparticle size distribution. This was a result of the aggregation of smaller nanoparticles to form larger agglomerations with diameters typically >50-100 nm. This is analogous to processes that occur during groundwater aeration for water treatment, and mixing of anaerobic and aerobic environmental waters, e.g. during rapid recharge events, flooding, hyporheic zone mixing, waste water treatment and waste water inputs to surface waters. The techniques developed in this study have potential wider applications for understanding the occurrence and fate of natural and anthropogenic (engineered) nanoparticles in sub-oxic conditions, such as the fate of nanoparticles injected for pollution attenuation, those found below landfill sites, within waste water treatment works and the hyporheic zone which are all important redox hot-spots for pollution attenuation and biological activity

Pacific variability reconciles observed and modelled global mean temperature increase since 1950

Global mean temperature change simulated by climate models deviates from the observed temperature increase during decadal-scale periods in the past. In particular, warming during the ‘global warming hiatus’ in the early twenty-first century appears overestimated in CMIP5 and CMIP6 multi-model means. We examine the role of equatorial Pacific variability in these divergences since 1950 by comparing 18 studies that quantify the Pacific contribution to the ‘hiatus’ and earlier periods and by investigating the reasons for differing results. During the ‘global warming hiatus’ from 1992 to 2012, the estimated contributions differ by a factor of five, with multiple linear regression approaches generally indicating a smaller contribution of Pacific variability to global temperature than climate model experiments where the simulated tropical Pacific sea surface temperature (SST) or wind stress anomalies are nudged towards observations. These so-called pacemaker experiments suggest that the ‘hiatus’ is fully explained and possibly over-explained by Pacific variability. Most of the spread across the studies can be attributed to two factors: neglecting the forced signal in tropical Pacific SST, which is often the case in multiple regression studies but not in pacemaker experiments, underestimates the Pacific contribution to global temperature change by a factor of two during the ‘hiatus’; the sensitivity with which the global temperature responds to Pacific variability varies by a factor of two between models on a decadal time scale, questioning the robustness of single model pacemaker experiments. Once we have accounted for these factors, the CMIP5 mean warming adjusted for Pacific variability reproduces the observed annual global mean temperature closely, with a correlation coefficient of 0.985 from 1950 to 2018. The CMIP6 ensemble performs less favourably but improves if the models with the highest transient climate response are omitted from the ensemble mean

Fractionation of iron species and iron isotopes in the Baltic Sea euphotic zone

To indentify sources and transport mechanisms of iron in a coastal marine environment, we conducted measurements of the physiochemical speciation of Fe in the euphotic zone at three different locations in the Baltic Sea. In addition to sampling across a salinity gradient, we conducted this study over the spring and summer season. Moving from the riverine input characterized low salinity Bothnian Sea, via the Landsort Deep near Stockholm, towards the Gotland Deep in the Baltic Proper, total Fe concentrations averaged 114, 44, and 15 nM, respectively. At all three locations, a decrease in total Fe of 80–90% from early spring to summer was observed. Particulate Fe (PFe) was the dominating phase at all stations and accounted for 75–85% of the total Fe pool on average. The Fe isotope composition (δ 56Fe) of the PFe showed constant positive values in the Bothnian Sea surface waters (+0.08 to +0.20‰). Enrichment of heavy Fe in the Bothnian Sea PFe is possibly associated to input of aggregated land derived Fe-oxyhydroxides and oxidation of dissolved Fe(II). At the Landsort Deep the isotopic fractionation of PFe changed between −0.08‰ to +0.28‰ over the sampling period. The negative values in early spring indicate transport of PFe from the oxic-anoxic boundary at ∼80 m depth. The average colloidal iron fraction (CFe) showed decreasing concentrations along the salinity gradient; Bothnian Sea 15 nM; Landsort Deep 1 nM, and Gotland Deep 0.5 nM. Field Flow Fractionation data indicate that the main colloidal carrier phase for Fe in the Baltic Sea is a carbon-rich fulvic acid associated compound, likely of riverine origin. A strong positive correlation between PFe and chl-a indicates that cycling of suspended Fe is at least partially controlled by primary production. However, this relationship may not be dominated by active uptake of Fe into phytoplankton, but instead may reflect scavenging and removal of PFe during phytoplankton sedimentation

The Red Flour Beetle as a Model for Bacterial Oral Infections

Experimental infection systems are important for studying antagonistic interactions and coevolution between hosts and their pathogens. The red flour beetle Tribolium castaneum and the spore-forming bacterial insect pathogen Bacillus thuringiensis (Bt) are widely used and tractable model organisms. However, they have not been employed yet as an efficient experimental system to study host-pathogen interactions. We used a high throughput oral infection protocol to infect T. castaneum insects with coleopteran specific B. thuringiensis bv. tenebrionis (Btt) bacteria. We found that larval mortality depends on the dietary spore concentration and on the duration of exposure to the spores. Furthermore, differential susceptibility of larvae from different T. castaneum populations indicates that the host genetic background influences infection success. The recovery of high numbers of infectious spores from the cadavers indicates successful replication of bacteria in the host and suggests that Btt could establish infectious cycles in T. castaneum in nature. We were able to transfer plasmids from Btt to a non-pathogenic but genetically well-characterised Bt strain, which was thereafter able to successfully infect T. castaneum, suggesting that factors residing on the plasmids are important for the virulence of Btt. The availability of a genetically accessible strain will provide an ideal model for more in-depth analyses of pathogenicity factors during oral infections. Combined with the availability of the full genome sequence of T. castaneum, this system will enable analyses of host responses during infection, as well as addressing basic questions concerning host-parasite coevolution

Productivity and Carbon Storage in Silvopastoral Systems with \u3cem\u3ePinus ponderosa\u3c/em\u3e and \u3cem\u3eTrifolium\u3c/em\u3e spp. Plantations and Pasture on a Volcanic Soil in the Chilean Patagonia

Little information is available about carbon (C) sequestration potentials in ecosystems on Andisols of the Chilean Patagonia. This study was undertaken to measure the size of the C stocks in three predominant ecosystems: Pinus ponderosa-based silvopastoral systems (SPS), pine plantations (PPP) and natural pasture (PST), and to examine how clover (Trifolium spp.) affect tree growth and stocks of soil C. The C contents of trees and pasture were determined by destructive sampling and dry combustion. Soil samples were taken at 0-5, 5-20, 20-40 cm depths in order to determine soil C and N. For PPP and SPS, respectively, 38.4 and 53.1 kg/tree of total tree C were stored aboveground, whereas 21.3 and 23.4 kg/tree were stored belowground. Tree diameter at breast height increased 1 and 2 cm/year in PPP and SPS, respectively, and was significantly higher in SPS, an interesting value for the region. Tree growth in SPS was enhanced by lower tree competition and the additional soil N provided by the leguminous pasture, resulting in larger amounts of C being sequestered. Soil organic C (SOC) stocks at 0-40 cm depth were 193.76, 177.10 and 149.25 Mg/ha in SPS, PST and PPP, respectively. The conversion of PPP to SPS and PST to PPP resulted in an increase of 44.51 Mg/ha and a decrease of 27.85 Mg/ha in SOC, respectively, at 0-40 cm soil depth. A favourable micro-climate (air temperature, soil moisture) has been observed in SPS as well as a synergistic effect between trees and pasture

A Regularized Discrete Laminate Parametrization Technique with Applications to Wing-Box Design Optimization

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97055/1/AIAA2012-1519.pd

Wave vector dependence of the dynamics in supercooled metallic liquids

We present a detailed investigation of the wave vector dependence of collective atomic motion in Au49Cu26.9Si16.3Ag5.5Pd2.3 and Pd42.5Cu27Ni9.5P21 supercooled liquids close to the glass transition temperature. Using x-ray photon correlation spectroscopy in a precedent uncovered spatial range of only few interatomic distances, we show that the microscopic structural relaxation process follows in phase the structure with a marked slowing down at the main average inter-particle distance. This behavior is accompanied by dramatic changes in the shape of the intermediate scattering functions which suggest the presence of large dynamical heterogeneities at length-scales corresponding to few particle diameters. A ballistic-like mechanism of particle motion seems to govern the structural relaxation of the two systems in the highly viscous phase, likely associated to hopping of caged particles in agreement with theoretical studies

VarFish - Collaborative and comprehensive variant analysis for diagnosis and research

VarFish is a user-friendly web application for the quality control, filtering, prioritization, analysis, and user-based annotation of panel and exome variant data for rare disease genetics. It is capable of processing variant call files with single or multiple samples. The variants are automatically annotated with population frequencies, molecular impact, and presence in databases such as ClinVar. Further, it provides support for pathogenicity scores including CADD, MutationTaster, and phenotypic similarity scores. Users can filter variants based on these annotations and presumed inheritance pattern and sort the results by these scores. Filtered variants are listed with their annotations and many useful link-outs to genome browsers, other gene/variant data portals, and external tools for variant assessment. VarFish allows user to create their own annotations including support for variant assessment following ACMG-AMP guidelines. In close collaboration with medical practitioners, VarFish was designed for variant analysis and prioritization in diagnostic and research settings as described in the software’s extensive manual. The user interface has been optimized for supporting these protocols. Users can install VarFish on their own in-house servers where it provides additional lab notebook features for collaborative analysis and allows re-analysis of cases, e.g., after update of genotype or phenotype databases