Dissolved organic carbon dynamics in a UK podzolic moorland catchment: linking storm hydrochemistry, flow path analysis and sorption experiments

Better knowledge of spatial and temporal delivery of dissolved organic carbon (DOC) in small catchments is required to understand the mechanisms behind reported long-term changes in C fluxes from some peatlands. We monitored two storms with contrasting seasons and antecedent conditions in a small upland UK moorland catchment. We examined DOC concentrations and specific UV absorbance (SUVA at 285 nm), together with solute concentrations required to undertake end-member mixing analyses to define dominant flow paths contributing to streamflow. This was combined with laboratory soil-solution equilibrations. We aimed to resolve how seasonal biogeochemical processing of DOC and flowpath changes in organo-mineral soils combine to affect DOC exported via the stream. An August storm following a dry period gave maximum DOC concentration of 10 mg l<sup>−1</sup>. Small DOC:DON ratios (16–28) and SUVA (2.7–3.6 l mg<sup>−1</sup> m<sup>−1</sup>) was attributed to filtration of aromatic compounds associated with up to 53% B horizon flow contributions. This selective filtration of high SUVA DOC was reproduced in the experimental batch equilibration system. For a November storm, wetter antecedent soil conditions led to enhanced soil connectivity with the stream and seven times greater DOC stream-load (maximum concentration 16 mg l<sup>−1</sup>). This storm had a 63% O horizon flow contribution at its peak, limited B horizon buffering and consequently more aromatic DOC (SUVA 3.9–4.5 l mg<sup>−1</sup> m<sup>−1</sup> and DOC:DON ratio 35–43). We suggest that simple mixing of waters from different flow paths cannot alone explain the differences in DOC compositions between August and November and biogeochemical processing of DOC is required to fully explain the observed stream DOC dynamics. This preliminary evidence is in contrast to other studies proposing hydrological controls on the nature of DOC delivered to streams. Although our study is based only on two storms of very different hydrological and biogeochemical periods, this should promote wider study of DOC biogeochemical alteration in headwaters so that this be better incorporated in modelling to predict the impacts of changes in DOC delivery to, and fate in, aquatic systems

Control of the conformations of ion Coulomb crystals in a Penning trap

Laser-cooled atomic ions form ordered structures in radiofrequency ion traps and in Penning traps. Here we demonstrate in a Penning trap the creation and manipulation of a wide variety of ion Coulomb crystals formed from small numbers of ions. The configuration can be changed from a linear string, through intermediate geometries, to a planar structure. The transition from a linear string to a zigzag geometry is observed for the first time in a Penning trap. The conformations of the crystals are set by the applied trap potential and the laser parameters, and agree with simulations. These simulations indicate that the rotation frequency of a small crystal is mainly determined by the laser parameters, independent of the number of ions and the axial confinement strength. This system has potential applications for quantum simulation, quantum information processing and tests of fundamental physics models from quantum field theory to cosmology

Resolved-sideband laser cooling in a penning trap

We report the laser cooling of a single ^{40}Ca^{+} ion in a Penning trap to the motional ground state in one dimension. Cooling is performed in the strong binding limit on the 729-nm electric quadrupole S_{1/2}↔D_{5/2} transition, broadened by a quench laser coupling the D_{5/2} and P_{3/2} levels. We find the final ground-state occupation to be 98(1)%. We measure the heating rate of the trap to be very low with n[over ¯][over ˙]≈0.3(2)  s^{-1} for trap frequencies from 150-400 kHz, consistent with the large ion-electrode distance

Heads in the cloud:innovation in data and model dissemination

Utilising environmental data to better support decision making is a complex task. The Environmental Virtual Observatory pilot project has demonstrated that a multidisciplinary approach to making integrated data and modelling services available via new cloud technologies offers a way forward

Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities

Background The dynamics of phosphorus (P) in the environment is important for regulating nutrient cycles in natural and managed ecosystems and an integral part in assessing biological resilience against environmental change. Organic P (Po) compounds play key roles in biological and ecosystems function in the terrestrial environment being critical to cell function, growth and reproduction. Scope We asked a group of experts to consider the global issues associated with Po in the terrestrial environment, methodological strengths and weaknesses, benefits to be gained from understanding the Po cycle, and to set priorities for Po research. Conclusions We identified seven key opportunities for Po research including: the need for integrated, quality controlled and functionally based methodologies; assessment of stoichiometry with other elements in organic matter; understanding the dynamics of Po in natural and managed systems; the role of microorganisms in controlling Po cycles; the implications of nanoparticles in the environment and the need for better modelling and communication of the research. Each priority is discussed and a statement of intent for the Po research community is made that highlights there are key contributions to be made toward understanding biogeochemical cycles, dynamics and function of natural ecosystems and the management of agricultural systems

Sideband cooling of small ion Coulomb crystals in a Penning trap

We have recently demonstrated the laser cooling of a single 40Ca+ ion to the motional ground state in a Penning trap using the resolved-sideband cooling technique on the electric quadrupole transition S1/2 ↔ D5/2. Here we report on the extension of this technique to small ion Coulomb crystals made of two or three 40Ca+ ions. Efficient cooling of the axial motion is achieved outside the Lamb-Dicke regime on a two-ion string along the magnetic field axis as well as on two- and three-ion planar crystals. Complex sideband cooling sequences are required in order to cool both axial degrees of freedom simultaneously. We measure a mean excitation after cooling of n¯COM = 0.30(4) for the centre of mass (COM) mode and n¯B = 0.07(3) for the breathing mode of the two-ion string with corresponding heating rates of 11(2) s−1 and 1(1)s−1 at a trap frequency of 162 kHz. The occupation of the ground state of the axial modes (ntilt = nCOM = 0) is above 75% for the two-ion planar crystal and the associated heating rates 0.8(5)s−1 at a trap frequency of 355 kHz

The multifunctional roles of vegetated strips around and within agricultural fields : A systematic map protocol.

Background: Agriculture and agricultural intensification can have significant negative impacts on the environment, including nutrient and pesticide leaching, spreading of pathogens, soil erosion and reduction of ecosystem services provided by terrestrial and aquatic biodiversity. The establishment and management of vegetated strips adjacent to farmed fields (including various field margins, buffer strips and hedgerows) are key mitigation measures for these negative environmental impacts and environmental managers and other stakeholders must often make decisions about how best to design and implement vegetated strips for a variety of different outcomes. However, it may be difficult to obtain relevant, accurate and summarised information on the effects of implementation and management of vegetated strips, even though a vast body of evidence exists on multipurpose vegetated strip interventions within and around fields. To improve the situation, we describe a method for assembling a database of relevant research relating to vegetated strips undertaken in boreo-temperate farming systems (arable, pasture, horticulture, orchards and viticulture). Methods: We will search 13 bibliographic databases, 1 search engine and 37 websites for stakeholder organisations using a predefined and tested search string that focuses on a comprehensive list of vegetated strip synonyms. Non-English language searches in Danish, Finnish, German, Spanish, and Swedish will also be undertaken using a web-based search engine. We will screen search results at title, abstract and full text levels, recording the number of studies deemed non-relevant (with reasons at full text). A systematic map database that displays the meta-data (i.e. descriptive summary information about settings and methods) of relevant studies will be produced following full text assessment. The systematic map database will be displayed as a web-based geographical information system (GIS). The nature and extent of the evidence base will be discussed

Phosphorus dynamics in a tropical forest soil restored after strip mining

Background and aims We hypothesized that successful early ecosystem and soil development in these P-deficient soil materials will initially depend on effective re-establishment of P storage and cycling through organic matter. This hypothesis was tested in a 26-year chronosequence of seven lightly fertilized, oxidic soil materials restored to eucalypt forest communities after bauxite mining. Methods Total P (Pt) status, Hedley P fractions and partial chemical speciation (NaOH-EDTA extraction and analysed using solution 31P NMR spectroscopy) were determined in the restored soils. Results Concentrations of Pt and most Hedley fractions changed with restoration period, declined with depth and were strongly positively correlated with C and N concentrations. Biological P dominated the Labile and Intermediate P fractions while Long-term P was dominantly inorganic. Organic P concentrations in NaOH-EDTA extracts and their chemical natures were similar in restored and unburned native forest sites. Phosphomonoesters were the dominant class of organic P. Conclusions Surprisingly rapid P accretion and fractional changes occurred over 26 years, largely in the surface soils and closely associated with organic matter status. Alkaline hydrolysis products of phosphodiesters and pyrophosphate indicated the importance of microbial P cycling. The important consequences for long-term ecosystem development and biological diversity require further study