Dynamic characteristics of sulfur, iron and phosphorus in coastal polluted sediments, north China

The cycling of sulfur (S), iron (Fe) and phosphorus (P) in sediments and pore water can impact the water quality of overlying water. In a heavily polluted river estuary (Yantai, China), vertical profiles of fluxes of dissolved sulfide, Fe2+ and dissolved reactive phosphorus (DRP) in sediment pore water were investigated by the Diffusive Gradients in Thin films technique (DGT). Vertical fluxes of S, Fe, P in intertidal sediment showed the availability of DRP increased while the sulfide decreased with depth in surface sediment, indicating that sulfide accumulation could enhance P release in anoxic sediment. In sites with contrasting salinity, the relative dominance of iron and sulfate reduction was different, with iron reduction dominant over sulfate reduction in the upper sediment at an intertidal site but the reverse true in a freshwater site, with the other process dominating at depth in each case. Phosphate release was largely controlled by iron reduction

Karte von Rastatt, Baden & Gernsbach

gezeichnet und gestochen von J.G. KromNordostorientier

Karte von Baden & Gernsbach : mit ihren nächsten Umgebungen

gezeichnet und gestochen von J.G KromNordstorientier

Integration of PCI modules in JDAQ

This paper presents the extension of the data acquisition and control system JDAQ used at TEXTOR, to allow different data acquisition hardware. The extension was developed for the INCAA-TR10 and INCAA-TR32 recorders. These modules are built in the "CompactPCI" hardware format. It has been demonstrated that measuring with PCI modules under JDAQ is possible. However, the handling of the modules is not as systematic as measuring with CAMAC modules. General problems with implementation of the PCI modules will be discussed in this paper. (C) 2009 Elsevier B.V. All rights reserved

Stream-bed phosphorus in paired catchments with different agricultural land use intensity

Stream-bed sediments from three paired catchments, each draining a lower agricultural intensity system and a higher agricultural intensity system, were analysed for (a) total P (TP), (b) bioavailable-P (Resin-P), (c) equilibrium phosphorus concentration (EPC0), and (d) degree of phosphorus saturation (DPS). The influence of agriculture on sediment P was explored within the context of other key variables that may control the sediment P concentrations such as particle size, Fe, Ca and organic matter content, and in terms of potential implications of sediment P to in-stream biota. TP concentrations, EPC0, and the proportion of fine sediment were highest at the sites with the greater agricultural impact. Higher concentrations of bioavailable-P were also found in higher intensity agricultural systems. However, the highest concentrations of bioavailable-P were found at sites with point source inputs. Sites with high Fe concentrations had higher TP concentrations relative to agricultural intensity, but also had lower DPS values, illustrating that the sediment still had the capacity to take up P in a strongly bound form. The results from this study show that higher risk agricultural practices (intensive arable production and dairy and beef production) can lead either directly, or indirectly through increased inputs of fine sediment, to increased sediment TP concentrations. The importance of geochemical and physical controls on the bed sediments’ capacity to mitigate high P inputs in headwater lowland streams, especially under low flows and times of eutrophication risk in spring and summer is illustrated

Internal loading of phosphorus in a sedimentation pond of a treatment wetland: Effect of a phytoplankton crash

Sedimentation ponds are widely believed to act as a primary removal process for phosphorus (P) in nutrient treatment wetlands. High frequency in-situ P, ammonium (NH4+) and dissolved oxygen measurements, alongside occasional water quality measurements, assessed changes in nutrient concentrations and productivity in the sedimentation pond of a treatment wetland between March and June. Diffusive equilibrium in thin films (DET) probes were used to measure in-situ nutrient and chemistry pore-water profiles. Diffusive fluxes across the sediment–water interface were calculated from the pore-water profiles, and dissolved oxygen was used to calculate rates of primary productivity and respiration. The sedimentation pond was a net sink for total P (TP), soluble reactive P (SRP) and NH4+ in March, but became subject to a net internal loading of TP, SRP and NH4+ in May, with SRP concentrations increasing by up to 41 μM (1300 μl− 1). Reductions in chlorophyll a and dissolved oxygen concentrations also occurred at this time. The sediment changed from a small net sink of SRP in March (average diffusive flux: − 8.2 μmol m− 2 day− 1) to a net source of SRP in June (average diffusive flux: + 1324 μmol m− 2 day− 1). A diurnal pattern in water column P concentrations, with maxima in the early hours of the morning, and minima in the afternoon, occurred during May. The diurnal pattern and release of SRP from the sediment were attributed to microbial degradation of diatom biomass, causing reduction of the dissolved oxygen concentration and leading to redox-dependent release of P from the sediment. In June, 2.7 mol-P day− 1 were removed by photosynthesis and 23 mol-P day− 1 were supplied by respiration in the lake volume. SRP was also released through microbial respiration within the water column, including the decomposition of algal matter. It is imperative that consideration to internal recycling is given when maintaining sedimentation ponds, and before the installation of new ponds designed to treat nutrient waste

The TEC Web-Umbrella

The TEC community operates the TEXTOR device and in doing so collects and stores data from a number of different front-end acquisition systems, processing codes and analysis systems. Due to the evolution of these systems in the past, different, distributed data storage technologies were used to record this data. In an attempt to reduce the number of interfaces client codes have to use when accessing data from these data stores, an "umbrella" concept was developed: a software-layer that covers (as an "umbrella") as many as possible of these stores and provides a unified access mechanism to them. We explored the possibility of using the widely supported HTTP protocol for this purpose; this is the core protocol of the World-Wide-Web and it is capable of transporting almost any type of data. The concepts behind using this protocol were based on earlier work at JET. Access via this umbrella has been provided to the most important data stores around TEXTOR and access to others is being added regularly. Clients codes, libraries and programs have been developed for several user environments. The HTTP based concepts and the data-access via this system have been found to be highly portable. This paper gives an overview of the TEC Web-Umbrella. system, it describes the basic concepts of this system and it presents some of the client-side codes and programs. The paper also reports on some first (tentative) user experiences with it. (C) 2002 Elsevier Science B.V. All rights reserved

Technical challenges in the construction of the steady-state stellarator Wendelstein 7-X

The next step in the Wendelstein stellarator line is the large superconducting device Wendelstein 7-X, currently under construction in Greifswald, Germany. Steady-state operation is an intrinsic feature of stellarators, and one key element of the Wendelstein 7-X mission is to demonstrate steady-state operation under plasma conditions relevant for a fusion power plant. Steady-state operation of a fusion device, on the one hand, requires the implementation of special technologies, giving rise to technical challenges during the design, fabrication and assembly of such a device. On the other hand, also the physics development of steady-state operation at high plasma performance poses a challenge and careful preparation. The electron cyclotron resonance heating system, diagnostics, experiment control and data acquisition are prepared for plasma operation lasting 30 min. This requires many new technological approaches for plasma heating and diagnostics as well as new concepts for experiment control and data acquisition