Impact of rainfall on the hygienic quality of blue mussels and water in urban areas in the Inner Oslofjord,Norway     

Ingun Tryland  Mette Myrmel  Øyvin Østensvik  Aina C. Wennberg  Lucy J. Robertson 《Marine pollution bulletin》2014

The effects of precipitation on the hygienic quality of water and blue mussels collected from five different localities in the urban areas in the Inner Oslofjord were investigated, with samples analysed for Escherichia coli, Salmonella spp., pathogenic Vibrio spp., Norovirus, Sapovirus, Cryptosporidium spp. and Giardia duodenalis. The sampling sites were located at varying distances from the outlet of combined sewer overflows (CSO)-impacted rivers/streams. In general, 1–3 log₁₀ increases in fecal indicator bacteria and human pathogens were observed after heavy rainfalls. Blue mussels appeared to be a useful indicator of the impact of sewage at these sites, and generally a good correlation was identified between concentrations of E. coli and other human pathogens in the mussels. Provision of general advice to the public of avoiding areas near the outlets of CSO-impacted rivers after heavy rainfall may reduce the risk of gastroenteritis by bathers and others that may swallow water during recreational activities.  相似文献   

MRS applicability for a study of glacial sedimentary aquifers in Central Jutland, Denmark   总被引：6，自引：0，他引：6  

Konstantinos Chalikakis  Mette Ryom Nielsen  Anatoly Legchenko 《Journal of Applied Geophysics》2008,66(3-4):176

Intensive geophysical measurements are currently being carried out in Denmark to comply with the Danish Government's environmental plans of dense hydrogeological mapping to ensure high quality non-treated drinking water supply based solely on groundwater. A MRS-TDEM combined geophysical survey was conducted to measure the applicability and the contribution of MRS to running drilling programs.Despite complicated electromagnetic noise conditions, the MRS method proved to be applicable in the Danish context. An example of the practical application of MRS combined with TDEM in two selected areas of the former County of Vejle in Denmark, demonstrates the efficiency of the technique. The MRS results clearly suggest optimal locations for water supply boreholes within subsurface structures with homogeneous resistivity conditions mapped by TDEM. These results reveal the interest of using MRS as a new geophysical tool for the Danish water supply policy, which can provide a foundation for optimising drilling site locations within areas with resistivities in the aquifer range. However, more MRS soundings need to be carried out in order to improve MRS calibration in the Danish context, which will allow quantitative MRS characterization of aquifers.  相似文献   

Conceptualizing delta forms and processes in Arctic coastal environments          下载免费PDF全文

Mette Bendixen  Aart Kroon 《地球表面变化过程与地形》2017,42(8):1227-1237

Climate warming in the Arctic directly causes two opposite changes in Arctic coastal systems: increased melt‐water discharge through rivers induces extra influx of sediments and extended open water season increases wave impact which reworks and erodes the shores. A shoreline change analysis along the southern coast of Disko Island in western Greenland was conducted with aerial photographs and satellite images from 1964, 1985, and 2012. The decadal morphologic evolution of this 85 km section showed that large parts of the coast had undergone very limited changes. However, two deltas were highly dynamic and popped up as hotspots. The Tuapaat delta and Skansen delta showed large progradation rates (1.5 and 7 m/yr) and migration of the adjacent barriers and spits. The dynamic behavior at the delta mouths was mainly caused by classic delta channel lobe switching at one delta (Tuapaat), and by a breach of the fringing spit at the other delta (Skansen). The longshore and cross‐shore transports are responsible for reworking the sediment with a result of migrating delta mouths and adjacent subaqueous mouth bars. Seaward progradation of the deltas is limited due to the steep nature of the bathymetry in Disko Bay. Finally, a schematic conceptual overview of processes and associated morphological responses for deltas in Arctic environments is presented, including the climate drivers affecting delta evolution. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Vertical Hydraulic Gradient Estimation in Clay Till,Using MiHPT Advanced Direct-Push Technology     

Louise Rosenberg  Mette M. Broholm  Nina Tuxen  Ida Henriette Kerrn-Jespersen  Gro Lilbæk  Poul L. Bjerg 《Ground Water Monitoring & Remediation》2022,42(1):29-37

The vertical transport of contaminants from source areas is employed in many risk assessment models and screening tools in order to estimate the contaminant mass discharge (CMD) into underlying aquifers. The key parameters for estimating CMD are the contaminant source area and concentration, and the vertical water flux, the latter of which depends on the vertical hydraulic conductivity and the vertical hydraulic gradient in the subsurface. This study focuses on advancing the use of the combined membrane interface probe hydraulic profiling tool (MiHPT) to investigate the vertical hydraulic gradient across a clay till overlying a sandy aquifer at a contaminated site in Denmark. Only the HPT is necessary for the estimate of vertical hydraulic gradient. The hydraulic head, clay till thickness, and resulting vertical hydraulic gradients found using the MiHPT compared well with observations from nearby nested wells. The parameter with the largest discrepancy was the thickness of the clay till. The advantage of the MiHPT is its relatively quick depth discrete access to information regarding subsurface permeability, vertical hydraulic gradients and contaminant distribution across a site. In this case study, performance of additional dissipationtests during the HPT log to acquire determination of the vertical hydraulic gradient increased the cost by 3% compared to standard HPT logs.  相似文献   

Comparison of Delivery Methods for Enhanced In Situ Remediation in Clay Till     

Camilla M. Christiansen  Ida Damgaard  Mette Broholm  Timo Kessler  Knud E. Klint  Bertel Nilsson  Poul L. Bjerg 《Ground Water Monitoring & Remediation》2010,30(4):107-122

Three methods for enhanced delivery of in situ remediation amendments in low-permeability deposits have been tested at a site in Denmark: pneumatic fracturing, direct-push delivery, and hydraulic fracturing. The testing was carried out at an uncontaminated part of a farm site, previously used for storage of chlorinated solvents, underlain by basal clay till with hydraulic conductivity ranging from 7.1× 10^–11 to 3.5 × 10^–7 m/s at testing depths 2.5 to 9.5 m b.s. Fluorescent tracers fluorescein and rhodamine WT were delivered. Tests of all three delivery methods have not been carried out at a single site before, and thus, this study provides unique data for comparison of enhanced delivery methods in both the vadose and saturated zone. Results show that pneumatic fracturing with nitrogen gas and propagation pressures of 1 to 9 bar had a distribution radius of less than 2 m, and produced dense networks of tracer-filled natural fractures above the redox boundary (0 to 3 m b.s.) and widely spaced, discrete, induced, tracer-filled subhorizontal fractures at depth (>3 m b.s.). Direct-push delivery at pressures of 8 to 30 bar had a distribution radius of approximately 1 m, distributed tracer primarily in natural fractures above the redox boundary and in discrete, closely spaced (but not merging) induced fractures below the redox boundary. Hydraulic fracturing with a sand-guar mixture at pressures of 0 to 6 bar produced an elliptical, asymmetrical, bowl-shaped fracture with a physical radius of approximately 3.5 m at 3 m b.s. The geometry of hydraulic fractures attempted emplaced at 6.5 and 9.5 m b.s. is uncertain, but clearly not horizontal as desired. The direct-push delivery method is robust and efficient for enhanced delivery at the clay till site in question, which based on thorough geological characterization is deemed a geologically representative basal clay till site.  相似文献   

Human-driven topographic effects on the distribution of forest in a flat,lowland agricul-tural region简   总被引：1，自引：0，他引：1  

Mette V. ODGAARD  Peder K. B CHER  Tommy DALGAARD  Jesper E. MOESLUND  Jens-Christian SVENNING 《地理学报(英文版)》2014,24(1):76-92

Complex topography buffers forests against deforestation in mountainous regions. However, it is unknown if terrain also shapes forest distribution in lowlands where human impacts are likely to be less constrained by terrain. In such regions, if important at all, to- pographic effects will depend on cultural-historical factors and thus be human-driven （an- thropogenic） rather than natural, except in regions where the general climate or extreme soils limit the occurrence of forests. We used spatial regression modeling to assess the extent to which topographic factors explain forest distribution （presence-absence at a 48x48 m resolu- tion） in a lowland agricultural region （Denmark, 43,075 km2） at regional and landscape scales （whole study area and 10x10 km grid cells, respectively）, how landscape-scale for- est-topography relationships vary geographically, and which potential drivers （topographic heterogeneity, forest cover, clay content, coastal/inland location） determine this geographic heterogeneity. Given a moist temperate climate and non-extreme soils all landscapes in Denmark would naturally be largely forest covered, and any topographic relationships will be totally or primarily human-driven. At regional scale, topographic predictors explained only 5% of the distribution of forest. In contrast, the explanatory power of topography varied from 0%-61% at landscape scale, with clear geographic patterning. Explanatory power of topog- raphy at landscape scale was moderately dependent on the potential drivers, with topog- raphic control being strongest in areas with high topographic heterogeneity and little forest cover. However, these conditioning effects were themselves geographically variable. Our findings show that topography by shaping human land-use can affect forest distribution even in flat, lowland regions, but especially via localized, geographically variable effects.  相似文献   

Field Demonstrations Using the Waterloo Ground Water Profiler   总被引：3，自引：0，他引：3  

Seth E. Pitkin  John A. Cherry  Robert A. Ingleton  Mette Broholm 《Ground Water Monitoring & Remediation》1999,19(2):122-131

Use of direct-push sampling tools fur rapid investigations of contaminated sites has proliferated in the past several years. A direct-push device, referred to as a ground water sampling profiler, was recently developed at the University of Waterloo. This tool differs from oilier direct-push tools in that point samples are collected at multiple depths in the same hole without retrieving, decontaminating, and re-driving the tool alter each sampling event. The collection of point samples, rather than samples from a longer screened interval, allows an exceptional level of detail to be generated about the vertical distribution of contamination from each hole. The benefits of acquiring this level of detail arc contingent on minimization of vertical cross contamination of samples caused by drag down from high concentration zones into underlying low concentration zones. In a detailed study of chlorinated solvent plumes in sandy aquifers, we found that drag down using the profiler is minimal or non-detectable even when the tool is driven through high concentration zones of dissolved chlorinated solvent contamination. Chlorinated solvent concentrations, primarily PCE and TCE at or below a detection limit of 1 μg/L, were obtained directly beneath plumes with maximum concentrations up to thousands of μg/L. Minimal drag down, on the order of a few μg/L to 20 μg/L, may have been observed below chlorinated solvent concentrations of several tens of thousands to hundreds of thousands of μg/L. Drag down through DNAPL zones was not evaluated.  相似文献   

Phytoscreening for Vinyl Chloride in Groundwater Discharging to a Stream          下载免费PDF全文

Cecilie B. Ottosen  Vinni Rønde  Stefan Trapp  Poul L. Bjerg  Mette M. Broholm 《Ground Water Monitoring & Remediation》2018,38(1):66-74

This study applies an optimized phytoscreening method to locate a chlorinated ethene plume discharging into a stream. To evaluate the conditions most suitable for successful phytoscreening, trees along the stream bank were monitored through different seasons with different environmental conditions and hence different uptake/loss scenarios. Vinyl chloride (VC) as well as cis‐dichloroethylene (cis‐DCE), trichloroethylene (TCE), and tetrachloroethylene (PCE) were detected in the trees, documenting that phytoscreening is a viable method to locate chlorinated ethene plumes, including VC, discharging to streams. The results reveal, that phytoscreening for VC is more sensitive to environmental conditions affecting transpiration than for the other chlorinated ethenes detected. Conditions leading to higher groundwater uptake by transpiration than contaminant loss by diffusion from the tree trunks are optimal (e.g., low relative humidity, plentiful hours of sunshine and an intermediate air temperature). Additionally, low precipitation prior to the sampling event is beneficial, as uptake of infiltrating precipitation dilutes the concentration in the trees. All chlorinated ethenes were sensitive to dilution by clean precipitation and in some months, this resulted in no detection of contaminants in the trees at all. Under optimal environmental conditions the tree cores allowed detection of chlorinated solvents and their metabolites in the underlying groundwater. Whereas, for less ideal conditions there was a risk of no detection of the more volatile VC. This study is promising for the future applicability of phytoscreening to locate shallow groundwater contamination with the degradation products of chlorinated solvents.  相似文献   

Upper Cretaceous bottom current deposits,north-east Greenland     

Jussi Hovikoski  Alfred Uchman  Rikke Weibel  Henrik Nøhr-Hansen  Emma Sheldon  Jon Ineson  Morten Bjerager  Jens Therkelsen  Mette Olivarius  Michael Larsen  Peter Alsen  Jørgen Bojesen-Koefoed 《Sedimentology》2020,67(7):3619-3654

Reported ancient bottom current deposits in deep marine settings are scarce and most of them remain contentious. This study describes sedimentological, ichnological and petrographical characteristics of a drill core that covers ca 10 Myr of Upper Cretaceous stratigraphy at Hold with Hope, north-east Greenland. The core is divided into four facies associations, which are interpreted to reflect deposition from bottom currents, turbidity flows and hemipelagic settling in slope and/or near slope environments. The evidence for bottom current influence is three-fold. Firstly, pervasive indications of winnowing such as marine bioclast-rich lags and outsized clasts on ‘mud on mud’ contacts are suggestive of low-sediment concentration flows capable of transporting up to pebble-sized clasts. Common Mn–Fe–Mg rich carbonate matrix cements and various types of hiatal chemogenic lag deposits showing glauconite, apatite and carbonate clasts also point to condensation, prolonged exposure at the sediment–water interface and recurrent phases of sea-floor erosion. Secondly, such deposits can show indicators for tidal processes such as double mud-drapes, tangential bottom sets in dune-scale cross-bedding and cyclic rhythmites. Thirdly, inverse to normal grading at various scales is common in fully marine, commonly seafloor-derived sediments. Ichnological data indicate considerable taxonomic variability in the bottom current deposits, but recurrent fabrics are characteristically dominated by morphologically simple burrows such as Thalassinoides and Planolites, with secondary Phycosiphon, Nereites, Zoophycos and/or Chondrites. In general, opportunistic taxa are common whereas mature composite ichnofabrics are rare. The omission surfaces are locally burrowed with stiffground to firmground trace fossil suites. The results contribute to establishing sedimentological, ichnological and mineralogical criteria for recognition of bottom current deposits as well as to the understanding of the Late Cretaceous palaeoenvironmental evolution of the Arctic region.  相似文献