Faecal indicator bacteria in New Zealand freshwater fish: a pilot study     

Sarah Coxon  Jon S Harding  Brent Gilpin 《新西兰海洋与淡水研究杂志》2019,53(3):470-479

Recent studies have suggested that poikilothermic animals, such as fish, may represent a previously overlooked source of the faecal indicator bacteria (FIB) used for the assessment of water quality. However, quantitative studies of FIB in poikilotherms are scarce. We investigated the presence of FIB in the faeces of five freshwater fish species. E. coli and enterococci were detected in 71 and 76% of faecal samples, respectively. Concentrations were highly variable, with maximum concentrations (2.1?×?10⁴ E. coli and 1.3?×?10⁶ enterococci per gram of faecal material) up to four orders of magnitude higher than present in the water column. FIB were not detected in faecal samples from marine fish. Our findings suggest that FIB ingested from the environment may be capable of replication within the fish gut, making fish a potential source and transport mechanism for FIB in New Zealand freshwaters. This may have implications for water quality monitoring.  相似文献   

The role of fog,orography, and seasonality on precipitation in a semiarid,tropical island          下载免费PDF全文

Sarah R. Schmitt  Diego A. Riveros‐Iregui  Jia Hu 《水文研究》2018,32(18):2792-2805

Isotopes of water (²H/¹H and ¹⁸O/¹⁶O) are commonly used to trace hydrological processes such as moisture recycling, evaporation loss, and moisture source region and often vary temporally in a given region. This study provides a first‐ever characterization of temporally variable precipitation mechanisms of San Cristóbal Island, Galápagos. We collected fog, rain, and throughfall samples over three field seasons to understand the mechanisms driving seasonal‐ and event‐based variability in the isotopic composition of precipitation in Galápagos. We establish that fog is a common phenomenon in San Cristóbal, especially during the dry season, and we found that fog, compared with cocollected rainfall, is consistently enriched. We further suggest that the relative contribution of fog formed via different mechanisms (orographic, advective, radiation) varied seasonally. We found that the source region is the most dominant control of the isotopic composition of rainfall in the Galápagos at both the seasonal and event scales, but subcloud evaporative processes (the nontraditional manifestation of the amount effect) became a dominant control on the isotopic composition of rainfall during the dry season. Overall, our findings suggest that understanding seasonally variable water‐generating mechanisms is required for effective water resource management in San Cristóbal Island and other semiarid island ecosystems under current and future regimes of climate change.  相似文献   

Gatekeepers,Shareholders, and Evangelists: Expanding Communication Networks of African American Forest Landowners in North Carolina     

Sarah Hitchner  Puneet Dwivedi  John Schelhas  Arundhati Jagadish 《社会与自然资源》2019,32(7):751-767

The Sustainable Forestry and African American Land Retention Program (SFLR) was launched in 2012 to increase adoption of sustainable forestry practices among African American landowners in the southeastern United States to prevent land loss, increase forest health, and build economic assets. One of its main goals was to build communication networks through which African American landowners could obtain and share information about forestry practices and landowner assistance programs independent of public agencies. To measure and examine the growth of these communication networks over a three-year period (2014-2017), we conducted 87 interviews with landowners (24 of whom were interviewed multiple times), SFLR personnel, and Federal and State staff members in North Carolina. We used complementary methods of data gathering and analysis, including social network analysis and qualitative analysis. Our results showed expanding communication networks will be sustained independently of the program over time, although there is still a heavy reliance on program personnel.  相似文献   

Evaluating post-wildfire logging-slash cover treatment to reduce hillslope erosion after salvage logging using ground measurements and remote sensing     

Peter R. Robichaud  Sarah A. Lewis  Robert E. Brown  Edwin D. Bone  Erin S. Brooks 《水文研究》2020,34(23):4431-4445

Continuing long and extensive wildfire seasons in the Western US emphasize the need for better understanding of wildfire impacts including post-fire management scenarios. Advancements in our understanding of post-fire hillslope erosion and watershed response such as flooding, sediment yield, and debris flows have recently received considerable attention. The potential impacts of removing dead trees, called salvage logging, has been studied, however the use of remotely sensed imagery after salvage logging to evaluate spatial patterns and recovery is novel. The 2015 North Star Fire provided an opportunity to evaluate hillslope erosion reduction using two field experiments and coincidental remotely sensed imagery over 3 years. Simulated rill experiments with four flow rates were used to quantify hillslope erosion on skidder trails with and without added logging slash compared with a burned-only control. Seven replicated hillslope silt fence plots with the same treatments were also evaluated for natural rainfall events. WorldView-2 satellite imagery was used to relate ground cover and erodible bare soil between the two experiments using multi-temporal Normalized Differenced Vegetation Index (NDVI) values. Results indicate that the skid trails produced significantly more sediment (0.70 g s⁻¹) than either the slash treated skid trail (0.34 g s⁻¹) or controls (0.04 g s⁻¹) with the simulated rill experiment. Similarly, under natural rainfall conditions sediment yield from hillslope silt fence plots was significantly greater for the skid trail (3.42 Mg ha⁻¹) than either the slash treated skid trail (0.18 Mg ha⁻¹) or controls (0 Mg ha⁻¹). An NDVI value of 0.32 on all plots over all years corresponded to a ground cover of about 60% which is an established threshold for erosion reduction. Significant relationships between NDVI, ground cover, and sediment values suggest that NDVI may help managers evaluate ground cover and erosion potential remotely after disturbances such as a wildfire or salvage logging.  相似文献   

Computer Science and Programming Courses in Geography Departments in the United States     

Forrest J. Bowlick  Daniel W. Goldberg  Sarah Witham Bednarz 《The Professional geographer》2017,69(1):138-150

Geographic information systems (GIS) are fundamental information technologies. The capabilities and applications of GIS continue to rapidly expand, requiring practitioners to have new skills and competencies, especially in computer science. There is little research, however, about how best to prepare the next generation of GIScientists with adequate computer science skills. This article explores how U.S. geography departments are introducing and developing computer science and programming skills in their geography and GIS degree programs. We review the degree requirements in fifty-five geography departments and discover that forty-four of them offer some kind of GIS programming course. Of the 210 separate degree options identified, however, only 22 require one of these courses for a degree. There is little consistency or emphasis on computer science and programming skills in geography or GIS degrees, despite the immense importance of these components in geography and GIS careers. We propose future research along distinct investigative tracks to build a research-based understanding of the educational interactions among GIS, computer science, programming, and geography.  相似文献   

Downscaling climate-model output in mountainous terrain using local topographic lapse rates for hydrologic modeling of climate-change impacts     

Sarah Praskievicz 《自然地理学》2018,39(2):99-117

One of the challenges in using general circulation model (GCM) output is the need to downscale beyond the model’s coarse spatial grid for use in hydrologic modeling of climate-change impacts. In mountainous terrain, using elevation as a primary control on temperature and precipitation at the local scale provides the potential for topographic variables to be used to adjust climate-model output. Here, local topographic lapse rates (LTLR) were estimated from gridded climate data for the Pacific Northwest of the United States and used to downscale GCM output. Skill scores were calculated for the LTLR-downscaled climate-model output relative to an existing set of model output downscaled using the established statistical downscaling technique of localized constructed analogs (LOCA). The results indicate that the LTLR method performs well in the mountainous study region relative to the LOCA method. LTLR downscaling offers a promising method for downscaling climate-model output in regions in which elevation strongly controls climate, particularly for studying impacts of future climate change on water resources.  相似文献   

Reducing fugitive methane emissions from the North American oil and gas sector: a proposed science-policy framework     

Kate Konschnik  Sarah Marie Jordaan 《Climate Policy》2018,18(9):1133-1151

The shale gas boom in the United States spurred a shift in electricity generation from coal to natural gas. Natural gas combined cycle units emit half of the CO₂ to produce the same energy as a coal unit; therefore, the market trend is credited for a reduction in GHG emissions from the US power sector. However, methane that escapes the natural gas supply chain may undercut these relative climate benefits. In 2016, Canada, the United States and Mexico pledged to reduce methane emissions from the oil and natural gas sector 40–45% from 2012 levels by 2025. This article reviews the science-policy landscape of methane measurement and mitigation relevant for meeting this pledge, including changes in US policy following the 2016 presidential election. Considerable policy incoherence exists in all three countries. Reliable inventories remain elusive; despite government and private sector research efforts, the magnitude of methane emissions remains in dispute. Meanwhile, mitigation efforts vary significantly. A framework that integrates science and policy would enable actors to more effectively inform, leverage and pursue advances in methane measurement and mitigation. The framework is applied to North America, but could apply to other geographic contexts.

Key policy insights

• The oil and gas sector’s contribution to atmospheric methane concentrations is becoming an increasingly prominent issue in climate policy.

• Efforts to measure and control fugitive methane emissions do not presently proceed within a coherent framework that integrates science and policy.

• In 2016, the governments of Canada, Mexico and the United States pledged to reduce methane emissions from the oil and natural gas sector 40–45% from 2012 levels by 2025.

• The 2016 presidential election in the United States has halted American progress at the federal level, suggesting a heavier reliance on industry and subnational efforts in that country.

• Collectively or individually, the countries, individual agencies, or private stakeholders could use the proposed North American Methane Reduction framework to direct research, enhance monitoring and evaluate mitigation efforts, and improve the chances that continental methane reduction targets will be achieved.

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Normal fault growth and linkage in the Gediz (Alaşehir) Graben,Western Turkey,revealed by transient river long‐profiles and slope‐break knickpoints          下载免费PDF全文

Emiko Kent  Sarah J. Boulton  Alexander C. Whittaker  Iain S. Stewart  M. Cihat Alçiçek 《地球表面变化过程与地形》2017,42(5):836-852

The Gediz (Ala?ehir) Graben is located in the highly tectonically active and seismogenic region of Western Turkey. The rivers upstream of the normal fault‐bounded graben each contain a non‐lithologic knickpoint, including those that drain through inferred fault segment boundaries. Knickpoint heights measured vertically from the fault scale with footwall relief and documented fault throw (vertical displacement). Consequently, we deduce these knickpoints were initiated by an increase in slip rate on the basin‐bounding fault, driven by linkage of the three main fault segments of the high‐angle graben bounding fault array. Fault interaction theory and ratios of channel steepness suggest that the slip rate enhancement factor on linkage was a factor of 3. We combine this information with geomorphic and structural constraints to estimate that linkage took place between 0.6 Ma and 1 Ma. Calculated pre‐ and post‐linkage throw rates are 0.6 and 2 mm/yr respectively. Maximum knickpoint retreat rates upstream of the faults range from 4.5 to 28 mm/yr, faster than for similar catchments upstream of normal faults in the Central Apennines and the Hatay Graben of Turkey, and implying a fluvial landscape response time of 1.6 to 2.7 Myr. We explore the relative controls of drainage area and precipitation on these retreat rates, and conclude that while climate variation and fault throw rate partially explain the variations seen, lithology remains a potentially important but poorly characterised variable. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Delineation of flooding risk hotspots based on digital elevation model,calculated and historical flooding extents: the case of Ouagadougou     

Raffaele?De RisiEmail author  Fatemeh?Jalayer  Francesco?De Paola  Sarah?Lindley 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(6):1545-1559

Delineation of flood risk hotspots can be considered as one of the first steps in an integrated methodology for urban flood risk management and mitigation. This paper presents a step-by-step methodology in a GIS-based framework for identifying flooding risk hotspots for residential buildings. This is done by overlaying a map of potentially flood-prone areas [estimated through the topographic wetness index (TWI)], a map of residential areas [extracted from a city-wide assessment of urban morphology types (UMT)], and a geo-spatial census dataset. The novelty of this paper consists in the fact that the flood-prone areas (the TWI thresholds) are identified through a maximum likelihood method (MLE) based both on inundation profiles calculated for a specific return period (T_R), and on information about the extent of historical flooding in the area of interest. Furthermore, Bayesian parameter updating is employed in order to estimate the TWI threshold by employing the historical extent as prior information and the inundation map for calculating the likelihood function. For different statistics of the TWI threshold, the map of potentially flood-prone areas is overlaid with the map of residential urban morphology units in order to delineate the residential flooding risk urban hotspots. Overlaying the delineated urban hotspots with geo-spatial census datasets, the number of people affected by flooding is estimated. These kind of screening procedures are particularly useful for locations where there is a lack of detailed data or where it is difficult to perform accurate flood risk assessment. In fact, an application of the proposed procedure is demonstrated for the identification of urban flooding risk hotspots in the city of Ouagadougou, capital of Burkina Faso, a city for which the observed spatial extent of a major flood event in 2009 and a calculated inundation map for a return period of 300 years are both available.  相似文献   

The fusion crust of the Winchcombe meteorite: A preserved record of atmospheric entry processes     

Matthew J. Genge  Luke Alesbrook  Natasha V. Almeida  Helena C. Bates  Phil A. Bland  Mark R. Boyd  Mark J. Burchell  Gareth S. Collins  Luke T. Cornwell  Luke Daly  Hadrien A. R. Devillepoix  Matthias van Ginneken  Ansgar Greshake  Daniel Hallatt  Christopher Hamann  Lutz Hecht  Laura E. Jenkins  Diane Johnson  Rosie Jones  Ashley J. King  Haithem Mansour  Sarah McMullan  Jennifer T. Mitchell  Gavyn Rollinson  Sara S. Russell  Christian Schröder  Natasha R. Stephen  Martin D. Suttle  Jon D. Tandy  Patrick Trimby  Eleanor K. Sansom  Vassilia Spathis  Francesca M. Willcocks  Penelope J. Wozniakiewicz 《Meteoritics & planetary science》2024,59(5):948-972

Fusion crusts form during the atmospheric entry heating of meteorites and preserve a record of the conditions that occurred during deceleration in the atmosphere. The fusion crust of the Winchcombe meteorite closely resembles that of other stony meteorites, and in particular CM2 chondrites, since it is dominated by olivine phenocrysts set in a glassy mesostasis with magnetite, and is highly vesicular. Dehydration cracks are unusually abundant in Winchcombe. Failure of this weak layer is an additional ablation mechanism to produce large numbers of particles during deceleration, consistent with the observation of pulses of plasma in videos of the Winchcombe fireball. Calving events might provide an observable phenomenon related to meteorites that are particularly susceptible to dehydration. Oscillatory zoning is observed within olivine phenocrysts in the fusion crust, in contrast to other meteorites, perhaps owing to temperature fluctuations resulting from calving events. Magnetite monolayers are found in the crust, and have also not been previously reported, and form discontinuous strata. These features grade into magnetite rims formed on the external surface of the crust and suggest the trapping of surface magnetite by collapse of melt. Magnetite monolayers may be a feature of meteorites that undergo significant degassing. Silicate warts with dendritic textures were observed and are suggested to be droplets ablated from another stone in the shower. They, therefore, represent the first evidence for intershower transfer of ablation materials and are consistent with the other evidence in the Winchcombe meteorite for unusually intense gas loss and ablation, despite its low entry velocity.  相似文献