Trace elements in world steam coal and their behaviour in Dutch coal-fired power stations: A review

Trace elements associated with the combustion of coal have received more attention recently, as can be seen from the increasing demands laid down in legislation and permits.Knowledge of the trace element content of coal is essential. Coal used in the Netherlands is imported from all over the world. As a consequence, Dutch power stations are designed to burn a wide range of bituminous coals. The largest share nowadays originates from South Africa, Colombia, and Indonesia, with these three countries accounting for more than 85% of the coal fired in the Netherlands in recent years. The coals, as imported in the Netherlands, have been monitored for their (trace) element content. At present the database contains results of own analyses of about 170 coals, originating from 14 different countries. An important uncertainty was the question of how homogeneous the imported lots are. It appears that the lots as imported from overseas are fairly homogeneous.The behaviour and fate of trace elements in coal-fired power stations has been studied in more than 40 mass balance studies since 1977. More than 50 test series have been completed during co-combustion of biomass and waste materials (up to 40% on mass base) since 1993. It has therefore been possible to establish a relationship between (trace) elements in the fuel and the ash, as well as with emissions into the atmosphere.     

The Effelsberg Bonn H I Survey (EBHIS)

The Effelsberg‐Bonn H I survey (EBHIS) comprises an all‐sky survey north of Dec = –5° of the Milky Way and the local volume out to a red‐shift of z ≃ 0.07. Using state of the art Field Programmable Gate Array (FPGA) spectrometers it is feasible to cover the 100 MHz bandwidth with 16.384 spectral channels. High speed storage of H I spectra allows us to minimize the degradation by Radio Frequency Interference (RFI) signals. Regular EBHIS survey observations started during the winter season 2008/2009 after extensive system evaluation and verification tests. Until today, we surveyed about 8000 square degrees, focusing during the first all‐sky coverage of the Sloan‐Digital Sky Survey (SDSS) area and the northern extension of the Magellanic stream. The first whole sky coverage will be finished in 2011. Already this first coverage will reach the same sensitivity level as the Parkes Milky Way (GASS) and extragalactic surveys (HIPASS). EBHIS data will be calibrated, stray‐radiation corrected and freely accessible for the scientific community via a webinterface. In this paper we demonstrate the scientific data quality and explore the expected harvest of this new all‐sky survey (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Origin and mobility of hexavalent chromium in North-Eastern Attica,Greece

An integrated framework that is comprised of field surveys of groundwater, surface water and soils, laboratory process experiments and hydrologic and geochemical modeling is used to identify the origin (anthropogenic versus geogenic sources), fate and transport of hexavalent Cr in Tertiary and Quaternary deposits of Oropos plain in Greece. Groundwater and soils were analyzed in May 2008 and exhibited considerable Cr concentrations. Mineralogical analysis and micro-XRF analysis of the heavy soil fractions (metallic components) showed Cr bearing phases like chromites, Cr-silicate phases with positive correlation between Si, Al, Fe and Cr soil concentrations. Column experiments showed the Cr(VI) desorption ability of soils, e.g. concentration of 20 μg L⁻¹ was detected after the application of 50 mm of rain. The groundwater model simulated the variability of Cr concentrations emanating from both anthropogenic and geogenic sources, successfully using rate constants obtained from the laboratory experiments, e.g. 4.24 nM h⁻¹ for serpentine soil and 0.77 nM h⁻¹ for soil in alluvial deposits. The mineralogical and geochemical results support a geogenic origin for Cr in soils and groundwater of Oropos plain while modeling results suggest that contaminants transported by Asopos River have affected only the upper layers of the subsurface in the vicinity of the river. The framework can be used to establish background concentrations or clean up levels of Cr-contaminated soils and groundwater.     

Hydrological change in the central interior of British Columbia,Canada: diatom and pollen evidence of millennial-to-centennial scale change over the Holocene

Diatom-based inferences of post-glacial hydrological change from a sedimentary record from Felker Lake, British Columbia, show millennial-scale pacing of climate over the past approximately 11670 calendar years with change at ca. 8140 cal. year BP, ca. 6840 cal. year BP, ca. 5700 cal. year BP, and ca. 2230 cal. year BP. Early postglacial diatom assemblages are dominated by fragilaroid taxa, suggesting that cool and moist climate conditions and relatively high lake levels prevailed at this time. Early Holocene warming near ca. 8140 cal. year BP promoted Cyclotella bodanica var. lemanica, a fall bloomer competitive in limnological conditions associated with warmer water and stratified conditions. Short-lived peaks of Stephanodiscus parvus/minutulus between ca. 6340 cal. year BP and ca. 5860 cal. year BP indicate periodic increases in nutrient availability and prolonged mixing likely associated with long cool and moist spring seasons. The diatom-inferred depth of Felker Lake increased during the mid-Holocene to reach a record high-stand at ca. 5860 cal. year BP. Large changes in hydrological variability and terrestrial vegetation at Felker Lake occurred after ca. 2230 cal. year BP when high-amplitude centennial-scale fluctuations in diatom-inferred lake depth and salinity are observed. Change is first documented in terrestrial vegetation at this time by a shift from open Pinus parklands to a landscape that periodically supported populations of Cupressaceae. Three record low-stand high-salinity events are reconstructed between ca. 1910 cal. year BP and ca. 1800 cal. year BP, ca. 1030 cal. year BP and ca. 690 cal. year BP, and ca. 250 cal. year BP and ca. 140 cal. year BP. The low lake-level episode of ca. 1030 cal. year BP–ca. 690 cal. year BP is coeval with the Medieval Warm Period (ca. 1000 cal. year BP–ca. 600 cal. year BP), a period of intense drought in western North America. Post-glacial hydrological change at Felker Lake is coherent with regional, hemispherical, and global paleoclimate events, suggesting that millennial-and centennial-scale shifts in water availability are a persistent feature of the climate of western North America.     

The effects of introduced water hyacinth on habitat structure,invertebrate assemblages,and fish diets

The South American floating aquatic plant water hyacinth (Eichhornia crassipes) has a history of worldwide invasions, including a 1904 introduction into the Sacramento-San Joaquin Delta, California. The native pennywort (Hydrocotyle umbellata) occupies similar habitats in the Delta and is extensively used by resident invertebrates and fish. We sought to discover if an invader would be functionally equivalent to the native plant, by asking whether the encroadhing hyacinth modified the invertebrate assemblage structure and fish-invertebrate food web relative to pennywort. We sampled epiphytic, epibenthic, and benthic invertebrates, and plant canopy insects in patches of hyacinth and pennywort, and analyzed fish diets at three sites in the Delta during 1998. We also measured habitat structure (leaf density, root biomass, and surface area). In 1999, following control and absence of hyacinth, we again measured epiphytic invertebrates in pennywort. We found differences between hyacinth and pennywort in structure, associated invertebrates, and fish diets. Most measurements inferred functional non-equivalency between hyacinth and pennywort, although some functional equivalency and natural variation existed. Leaf and insect densities were significantly higher in pennywort and there were also significant differences in insect assemblage compositions. Hyacinth roots in the water column had significantly more surface area. Densities of epibenthic and benthic aquatic invertebrates were typically greater in pennywort and taxonomic compositions of aquatic invertebrate assemblages showed significant differences. Amphipods and isopods living epiphytically in the root masses were particularly abundant, including several newly discovered introduced species: the amphipodCrangonyx floridanus and the isopodsCaecidotea racovitai andAsellus hilgendorfii. The native amphipodHyalella azteca was more abundant in pennywort and heavily preyed upon by fish, while the non-indigenousC. floridanus was more abundant in hyacinth and not prevalent in fish diets. The introduction of hyacinth to the Delta has caused significant ecological alterations in the surrounding community, due to hyacinth being functionally different from native patches of pennywort.     

Wave climatology and extreme value analysis for the Baltic Sea area off the Warnemünde harbour entrance

Ocean Dynamics - A numerical wave model was used to determine the wave climate in the southern Baltic Sea. The basic data derived from wave hindcasts were evaluated statistically. Climate graphs...     

Agreeing to disagree: uncertainty management in assessing climate change, impacts and responses by the IPCC

Dealing consistently with risk and uncertainty across the IPCC reports is a difficult challenge. Huge practical difficulties arise from the Panel’s scale and interdisciplinary context, the complexity of the climate change issue and its political context. The key question of this paper is if the observed differences in the handling of uncertainties by the three IPCC Working Groups can be clarified. To address this question, the paper reviews a few key issues on the foundations of uncertainty analysis, and summarizes the history of the treatment of uncertainty by the IPCC. One of the key findings is that there is reason to agree to disagree: the fundamental differences between the issues covered by the IPCC’s three interdisciplinary Working Groups, between the type of information available, and between the dominant paradigms of the practitioners, legitimately lead to different approaches. We argue that properly using the IPCC’s Guidance Notes for Lead Authors for addressing uncertainty, adding a pedigree analysis for key findings, and particularly communicating the diverse nature of uncertainty to the users of the assessment would increase the quality of the assessment. This approach would provide information about the nature of the uncertainties in addition to their magnitude and the confidence assessors have in their findings.     

RFI detection by automated feature extraction and statistical analysis

In this paper we present an interference detection toolbox consisting of a high dynamic range Digital Fast‐Fourier‐Transform spectrometer (DFFT, based on FPGA‐technology) and data analysis software for automated radio frequency interference (RFI) detection. The DFFT spectrometer allows high speed data storage of spectra on time scales of less than a second. The high dynamic range of the device assures constant calibration even during extremely powerful RFI events. The software uses an algorithm which performs a two‐dimensional baseline fit in the time‐frequency domain, searching automatically for RFI signals superposed on the spectral data. We demonstrate, that the software operates successfully on computer‐generated RFI data as well as on real DFFT data recorded at the Effelsberg 100‐m telescope. At 21‐cm wavelength RFI signals can be identified down to the 4σ _rms level. A statistical analysis of all RFI events detected in our observational data revealed that: (1) mean signal strength is comparable to the astronomical line emission of the Milky Way, (2) interferences are polarised, (3) electronic devices in the neighbourhood of the telescope contribute significantly to the RFI radiation. We also show that the radiometer equation is no longer fulfilled in presence of RFI signals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)