Arctic ecosystems are vulnerable to human-induced changes such as increases in contaminant levels and climatic warming. To predict effects of these changes, it is important to understand trophic relationships among Arctic organisms and how they change in response to time and environmental perturbations. Seabird diet can reflect relative availability and abundance of planktivorous fish and zooplankton in remote areas. The measurement of naturally occurring stable isotopes presents an alternative approach to evaluating dietary patterns of seabirds at both an individual level and at a larger, ecosystem level. Relative changes in δ13C values provided an indication of changes in consumption of benthic vs. pelagic prey and changes in δ15N values provided an indication of changes in trophic level.<p>I investigated trophic positions of four seabirds (Thick-billed Murres (<i>Uria lomvia</i>); Northern Fulmars (<i>Fulmarus glacialis</i>); Black-legged Kittiwakes (<i>Rissa tridactyla</i>); and Glaucous Gulls (<i>Larus hyperboreus</i>)) at Prince Leopold Island, Nunavut, 1988 2003, using my own and previously measured stable isotope measurements in blood samples. Trophic level and space use among years differed within and among species and may be related to ice conditions and species-specific foraging strategies. The species with the most flexible foraging methods, Thick-billed Murres, varied their foraging location and trophic level the most. In 2002, fewer chicks than average for all species were fledged and Thick-billed Murre chicks were lighter than in other years; however, only murres showed a concurrent decrease in the proportion of fish in their diet. Adult body condition of murres in 2002 was positively correlated with trophic level. Breeding season dietary patterns of Thick-billed Murre adults and chicks were examined on Coats Island, Nunavut, Canada, in 2004. Adult trophic level increased slightly through the breeding season and δ13C values indicated a switch from benthic to pelagic foraging locations. Chick and adult murres did not differ in either δ15N or δ13C values; however, within a family (two parents, one chick), chicks were fed at or slightly below adult trophic level. I found little variation in stable isotope values which suggests adult murres did not preferentially select prey for either themselves or their chicks. <p>Finally, stable isotope analysis was used to investigate winter foraging ecology of three species of alcids (Thick-billed Murres; Common Murres (<i>U. aalge</i>) and Razorbills (<i>Alca torda</i>)), off Newfoundland, Canada, 1996 2004. Thick-billed Murres fed at a higher trophic level than Common Murres. Razorbill δ15N values were highly variable and overlapped those of both murre species. I found no significant differences in δ13C values among the three species confirming a common spatial feeding pattern. Both murre species became depleted in 13C during winter suggesting foraging location or prey species shifted from nearshore to offshore. For Common Murres, hatching-year individuals fed at a higher trophic level and foraged farther offshore than after-hatch year birds. For Thick-billed Murres, I contrasted trophic level determined for the breeding colony at Prince Leopold Island with those determined for winter over four years and found considerable inter-annual variation in patterns of seasonal difference in trophic level. However, the proportion of lower trophic level (amphipod) vs. higher trophic level (fish) prey was generally greater in the winter than the summer.

ABSTRACT In this study, we conducted an intensive sampling of Asian dusts at Pescadores Islands for heavy Asian continental sandstorms (ACS) from February 22 to March 6, 2008. To investigate the succession of anthropogenic and natural pollutants for the ACS transportation, PM2.5 and PM2.5-10 were sampled by two dichotomous samplers once every four hours during the ACS periods, and furthermore analyzed their physicochemical properties, including mass concentrations, particle size distribution, water-soluble ionic species, carbonaceous contents, and metallic contents. Experimental results indicated that it was mainly fine particles (PM2.5) prior to the ACS, and the percentage of anthropogenic species (i.e., SO42-, NH4+, NO3-, Zn, Mn and OC) increased dramatically. However, it changed to coarse particles while the ACS overwhelming, and the percentage of crustal/marine species (i.e., Cl-, Na+, Ca2+, Mg2+, Ca, Al, Mg and EC) increased. After the ACS, the concentrations of all species decreased substantially. However, the percentage of Cl- and Na+ increased, suggesting that sea breeze has constant influences on local suspended particles. In addition to the analysis of physicochemical properties of Asian dusts, this study applied a HYSPLIT MODEL to figure out the transportation routes and the source regions of the ACS. Backward trajectory analysis showed that the ACS was originated from the east portion of Inner Mongolia, namely the Onqin Daga Sandy Land and the Horqin Sandy Land. Moreover, seventeen soil samples were collected from the Tengger Desert, the Mu Us Desert, the Onqin Daga Sandy Land, and the Horqin Sandy Land in Inner Mongolia during the year of 2005. The soil samples were resuspended in a resuspension chamber and then collected by a dichotomous sampler. This study focused on PM2.5-10 particles that mainly influence the downwind regions, and then took the ACS samples and the resuspended soil samples to measure the Sr isotopic characteristics of 87Sr/86Sr ratios by a multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). To characterize the isotopic properties of resuspended dust particles from the ACS source regions in northern China, and to correlate Asian dusts at the downwind regions of ACS with the source regions by Duncan¡¦s Multiple Range Test (DMR). The DMR results showed that the ACS was probably originated from the east portion of Inner Mongolia, namely the Onqin Daga Sandy Land and the Horqin Sandy Land, which concurred with the backward trajectory analysis.

<p>In modern military operations the requirements of transmitting large amounts of information have increased substantially during the last decade. This increases the demand for high-capacity radio networks. It is also very important that military decisions are made on recent and correct information and this implies that low and known delays are required. The existing military radio ommunications, within the Swedish army, do not meet the requirements for capacity and delay. </p><p>We have investigated how the capacity and average delay can be improved in an Ad Hoc network with STDMA by using antenna arrays. The study is based on different antenna combinations consistingof single isotropic antenna element, beam steering and adaptive beamforming. We have also studied how the number of antenna elements, the terrain, and an increased connectivity due to the antenna arrays_affects the performance measurements. </p><p>The study shows that the capacity is improved with up to 1200%, and the average delays are decreased when using antenna arrays instead of single isotropic antenna elements. Depending on the beamforming combination used the capacity gain and average delay reduction will differ. The way of using the antenna array also affects the capacity gain and average delay. The capacity gain is higher when the antenna array is used not only to suppress and decrease interferences, but also to increase the connectivity. </p><p>The study also shows that the capacity gain is higher when using more antenna elements for a network with a high number of links, than with fewer. The benefit from antenna arrays is higher in a flat terrain than in a rough.</p>

Except for direct drilling and sampling of marine gas hydrates, the occurrence of gas hydrates has been identified generally by inference from indirect evidence, derived from geological, geophysical, and geochemical data. In this paper, we intend to discuss the geochemical anomalies of pore waters and their implications for gas hydrate occurrence in the northern continental slope of the South China Sea. The molecular concentration and isotopic composition of methane in sediments can provide clues to gas sources, whereas ionic and isotopic compositions of pore waters, such as steep SO42- gradients, shallow SMI (sulfate-methane interface) depths; decreasing pore water chlorinity, and heavy oxygen isotopic compositions, are used to identify gas hydrate occurrence and the distribution and thickness of sediment layers containing gas hydrates. Other good geochemical indicators include anions and cations concentrations such as Br-, I-, PO43-, NH4+, Ca2+, Mg2+, Sr2+, B3+, Li+, and Ba2+ in pore waters. We also found that the very negative carbon isotopic compositions of dissolve inorganic carbon (DIC) in pore waters can serve as good indicators for gas hydrate occurrence. In the South China Sea, three most promising target areas for gas hydrates include the Dongsha, Shenhu, and Xisha Trough.

Stable isotope of natural gas hydrates provides useful information of their gas sources. We investigated the isotopic fractionation of gas molecules during the formation of synthetic gas hydrates composed of methane and ethane. The gas hydrate samples were experimentally prepared in a pressure cell and isotopic compositions (δ13C and δD) of both residual and hydratebound gases were measured. δD of hydrate-bound molecules of methane and ethane hydrates was several per mil lower than that of residual gas molecules in the formation processes, while there was no difference in the case of δ13C. Effect of temperature on the isotopic fractionation was also investigated and it was found that the fractionation was effective at low temperature.

<p>This research investigated the nature, source and the spatial variation of the salinity of the water used for irrigation in the urban farming area of Philippi, which lies in the Cape Flats region of the Cape Town Metropolitan Area, South Africa. The irrigation water is mainly drawn from the Cape Flats aquifer, and pumped into ponds for eventual crop irrigation. Water samples were collected in summer and in winter from fifteen selected sites using standard water sampling procedures. Each site consisted of one borehole and one pond. The samples were routinely analyzed for salinity levels, and concentrations of major and minor ions. From the same boreholes and ponds, water was sampled in summer for isotope analysis to assess effects of evaporation on the water quality and salinity. Descriptive statistics were used to display the variation in range of specific ions in order to compare them with the recommended ranges. Geographical Information Systems analysis described the spatial distribution of the salinity across the study area, and hydrogeochemical analysis characterized the various waters and detected similarities between the water samples in the study area and other waters found in the Cape Flats region. In addition, the US salinity diagram classification of irrigation water developed by Richards (1954) was used to assess the current suitability of groundwater and pond water samples collected during the entire sampling period for irrigation activities. The research indicated that the concentrations of some ions such as chloride, nitrate, potassium and sodium exceeded in places in the study area, the target range values set by the Department of Water Affairs and Forestry (DWAF, 1996) and the Food and Agriculture Organization (Ayers and Westcot, 1985). It revealed that borehole and pond water were mostly brackish across the area regarding their total dissolved salts content, and fresh water was only found in the middle part of the study area. The research found that sea water does not intrude into the aquifer of the study area, and the accumulation of salts in groundwater and soil in the study area is mainly due to the agricultural activities and partially due to the natural movement of water through the geological formation of the Cape Flats region. The conceptual model of the occurrence of the salinization process supported these findings. From this investigation it is understood that the groundwater and pond water in the study area were generally suitable for irrigation purposes but they have to be used with caution as the vegetables are classified as sensitive and moderately sensitive to salt according to DWAF Irrigation water guidelines (1996). The quality of these waters was mainly affected by the land use activities.</p>

The ozone formation reaction O+O2+M→O3+M is a unique example of a chemical reaction that leads to an anomalous isotopic composition of the products, most likely due to symmetry - breaking effects. So far, results on other chemical systems that might show similar effects are spurious, even though such claims concerning reactions other than the formation of ozone have been made repeatedly.This applies in particular to the spin forbidden O+CO+M→CO2+M reaction, where two studies report a mass-independent fractionation of about 8%. Nevertheless, the presence of ozone in these experiments raises questions as to the validity of this assertion. We thus make a new attempt to study the O+CO+M reaction in the photoreactor at CCAR (University of Copenhagen) where reagents and contaminants are monitored on-line by FTIR spectroscopy. This study combined with the analysis of the spectral distribution of the employed lamps and isotope kinetic modeling lead to a complete re-interpretation of previous experiments. We conclude that available measurements are more compatible with the hypothesis that there is no mass-independent isotope fractionation in the O+CO reaction. We propose that all observations can be completely explained by an isotope transfer from ozone, involving photolytic production of O(1D) that in turn leads to OH radicals, which then rapidly form CO2 from reaction with CO. We also present a method to produce pure ozone samples and derive an upper limit on nitrogen oxide contaminations based on mass spectrometer measurements. These values will serve as benchmarks values for future studies of ozone absorption cross sections in the IR and UV.

Abstract Dissimilatory microbial sulfate reduction (MSR) The specific objectives of the study were to provide the first measurements of sulfur isotope fractionation associated with acidophilic sulfate reducing-microorganisms, and to examine whether pH influences sulfur fractionation during MSR. The fractionation associated with the strains investigated was comparable to that of neutrophilic strains with similar metabolisms (4-12‰), but varied with pH. Two fractionation regimes were identified: one regime is consistent with fractionation during exponential growth, while the other – not identified previously - is not linked to active sulfate reduction and may result from internal sulfate accumulation. This would represent the first measurement of sulfur fractionation during sulfate uptake, the first step of MSR. Geological processes at the Cretaceous-Paleogene (KPg) boundary The KPg boundary is associated with one of the largest biological extinctions in the history of our planet. Two major geologic events - the Chicxulub bolide impact with evaporite terrane and the eruption of the Deccan continental flood basalts - coincide with the KPg boundary and have been identified as possible triggers for the extinctions, but their relative timing remains unresolved. The objectives of this study were to identify the contribution of these processes to the sulfur burden in the sedimentary environment of two freshwater KPg sections, and to determine their relative timing. The results demonstrate that the peak of Deccan volcanism post-dates the Chicxulub impact and the associated abrupt KPg mass extinction, thus precluding a direct volcanic causal mechanism, but shedding light on the underlying causes for the delayed recovery of ecosystems in the early Paleogene.

Mass, solute (chloride), isotope (deuterium) and thermal balances were completed at Perry Lakes, two semi-permanent 'water table' lakes near Perth, Western Australia. All balance components except groundwater discharge/recharge were measured independently. These difficult to measure groundwater components of lake-aquifer interaction were estimated by integrating mass, solute and chloride data in sequential 4 day balances spanning two years. Before urbanisation, such wetlands functioned predominantly as flow-through lakes. Now, large winter storm water inputs (and summer artificial level maintenance pumped locally from groundwater) dominate. In East Lake these inputs together comprise 42% of the annual water budget; groundwater discharge is reduced to just 2%. Even under flow-through conditions, these 'non natural' inputs are so large East Lake always tends towards a recharge state and commonly becomes a local groundwater mound. Flow-through is established in both lakes over winter. Initially each lake functions separately however as winter progresses shared capture and release zones are established. Maintenance of lake levels in early summer forces East Lake back to recharge status. Sediment heat flux (Qse) is significant in these very shallow lakes. Over summer Qse was negative, with a net movement of heat from the water into the sediments which act as a seasonal heat sink. In winter Qse was positive and stored summer heat was returned to the water column. This flux at times exceeded 40 W m-2. Evaporation was determined independently by floating pan, leaving Qse as the thermal balance residual. Ignoring Qse, annual evaporation determined by thermal balance was over estimated by 7%. Over and under estimates of individual 12 day balance period evaporation exceeded 50%. Monthly Class A (Perth airport) pan coefficients varied from 0.54 (January) to 0.86 (September). Ten empirical equations for evaporation were calibrated and compared with the East Lake floating pan. Best performer was the Makkink which tracked the floating pan closely throughout all seasons. Poorest were the Penman, DeBruin-Keijman, Priestly-Taylor and Brutsaert-Stricker which grossly over estimated late winter evaporation. Transpiration from Typha orientalis, estimated using hydrograph techniques was 43% of open water evaporation in summer and 28% annually. Temperature controlled evaporation pans (tracking lake temperature) experimentally determined the local deuterium content of lake evaporate ƒÔE, required for isotopic balances. Techniques employing pans evaporated to dryness and pans evaporated at constant volume were run in tandem continuously for two years. This study singularly integrates mass, solute and isotope balances thereby allowing groundwater components to be accurately quantified. The isotope balances are unique, being the only such balances incorporating experimentally derived local deuterium values of lake evaporate. This study represents the only thermal balance, the only accurate determination of pan-lake coefficients and the first calibration of commonly used empirical evaporation equations for Swan Coastal Plain wetlands. Groundwater levels in the western suburbs of Perth have declined over 40 years and a disproportionate larger decline now seriously threatens Perry Lakes. Modelling suggests regional groundwater extraction exceeds recharge. Wetland managers can no longer maintain East Lake via local groundwater extraction. Artificial recharge using imported surface and waste water are possible future management options.

No description available.