Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Snow”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1998

Snow quality in the city of Luleå, Sweden--time-variation of lead, zinc, copper and phosphorus.

The quality of urban snow was studied with regard to how the concentrations of selected metals and phosphorus vary over time. The area studied is situated in northern Sweden (65 degrees 36' N; 22 degrees 13' E). Snow samples were taken at three different locations in the city centre, approximately every second week, throughout winter. This study has clearly shown the importance of local conditions and snow clearance operations on snow quality. The study also shows that it is difficult to interpret and predict the concentrations of lead, zinc, copper and phosphorus in the snow. However, it should be possible to predict the mass loads of these substances from the deposition velocities, if the snow handling methods and routines, as well as the local circumstances are known.

Copper↗
PubMed2005

Seasonal change in bacterial flora and biomass in mountain snow from the Tateyama Mountains, Japan, analyzed by 16S rRNA gene sequencing and real-time PCR.

The bacterial flora and biomass in mountain snow from the Tateyama Mountains, Toyama Prefecture, Japan, one of the heaviest snowfall regions in the world, were analyzed by amplified ribosomal DNA restriction analysis followed by 16S rRNA gene sequencing and DNA quantification by real-time PCR. Samples of surface snow collected in various months during the melting season contained a psychrophilic bacterium, Cryobacterium psychrophilum, and two psychrotrophic bacteria, Variovorax paradoxus and Janthinobacterium lividum. Bacterial colonies that developed in an in situ meltwater medium at 4 degrees C were revealed to be V. paradoxus. The biomasses of C. psychrophilum, J. lividum, and V. paradoxus, as estimated by real-time PCR, showed large increases during the melting season from March to October (2.0 x 10(5)-fold, 1.5 x 10(5)-fold, and 1.0 x 10(4)-fold increases, respectively), suggesting their rapid growth in the surface snow. The biomasses of C. psychrophilum and J. lividum increased significantly from March to April, reached a maximum in August, and dropped at the end of the melting season. In contrast, the biomass of V. paradoxus did not increase as rapidly during the early melting season but continued to increase from June until October. The differences in development observed among these bacterial species suggest that their growth was promoted by different nutrients and/or environmental conditions in the snow. Since these three types of bacteria have also been reported to be present in a glacier in Antarctica and a Greenland ice core, they seem to be specialized members of the snow biota that are distributed in snow and ice environments in various parts of the world.

Bacteria↗
PubMed1999

Snow algae of the Sierra Nevada, Spain, and High Atlas mountains of Morocco.

Snow algae (Chlorophyta) are reported from the Sierra Nevada mountains in southern Spain and the High Atlas mountains of Morocco. Populations of the snow algae Chlamydomonas sp., coloring the snow orange-red, were collected from Pico de Veleta, Spain, while snow samples from Mt. Neltner in the High Atlas mountains, contained resting spores of an orange-green colored Chloromonas sp. Other microbes observed in snow samples include bacteria, fungi, heterotrophic euglenids, diatoms, nematodes, and heterotrophic mastigotes (flagellated protists). This is the first report of snow algae from the Sierra Nevada mountains of Spain and from the Afro-alpine environment.

Altitude↗
PubMedDate not supplied

[Evaluation of pollution of an urban area by level of heavy metals in snow cover].

The goal of this study was to systematize various methodological approaches to evaluating the contamination of the snow cover with heavy metals (HM) by using Kazan, an industrial city with diversified industry, as an example. The findings suggest that it is necessary to characterize the contamination of the snow cover by the actual entrance of an element per area unit of the snow cover for a definite period of time rather than by the concentration of TM in the volume unit of snow water (mg/l), which minimizes the uncertainties with spatial and temporary snow cover variations. The index of the maximum allowable entrance, which is of practical value, may be used to objectively calibrate the pollution of the snow cover, by estimating the amount of a coming element and its toxicity.

Environmental Pollutants↗
PubMed2001

The impact of variable snow pack accumulation on a major Scottish water resource.

In regions such as northern Scotland, where winter temperatures are such that the occurrence of snow is borderline under the present climate, potential changes affecting precipitation and temperature regimes may have a disproportionately large impact on snow processes and hydrological behaviour. The physical characteristics of mountainous areas in Scotland mean that the spatial variability of snowpack accumulation is high, as well as the temporal variability caused by the climate. There have been few modelling studies aimed at assessing the significance of snow resources in these areas and none that have adopted a spatially distributed approach. This paper describes the approach taken in applying a new distributed model to a headwater catchment in the Cairngorm Mountains. The results demonstrate the importance of wind on re-distributing snow to create deep accumulations in small sheltered pockets. These accumulations are shown to be important in sustaining baseflows in the rivers, long after snow has melted from the rest of the catchment. The model has also produced a first set of maps showing how predicted snow depths vary across the catchment through the winter.

Journal Article↗
PubMed1986

IgE sensitization in snow crab-processing workers.

Occupational asthma is a highly prevalent disease among snow crab-processing workers, but its immunologic mechanism has not been identified. Prick skin tests with snow crab-meat extract, commercial extracts from other crab genera, and snow crab cooking water collected in 1984 were performed on 119 workers. Crab-specific IgE was assessed by RAST in sera from 115 workers with meat and water extracts. Both skin and RAST tests were performed in 58 individuals. Diagnosis of occupational asthma had previously been confirmed in 54 individuals. A highly significant relationship was demonstrated between the presence of immediate skin reactivity or increased serum levels of specific IgE to crab extracts and the occurrence of occupational asthma. There was good agreement between the results of skin and RAST tests with extracts of either meat or snow crab cooking water. Cooking water and snow crab-meat extracts were more sensitive than commercial preparations. Water extract was more potent and more sensitive than meat extract. We conclude that there is evidence that occupational asthma in snow crab-processing workers is mediated through an IgE mechanism.

Aerosols↗
PubMed1995

A new perspective on John Snow's communicable disease theory.

When John Snow undertook the studies of the cholera epidemic of 1854 in London, he was testing his theory of communicable disease, which had been enunciated in an oration delivered at the 80th anniversary of the Medical Society of London. Snow had been elected orator of the year for 1853 and, according to his biographer, had spent the better part of a year in preparation. The oration was titled, "On Continuous Molecular Changes, More Particularly in Their Relation to Epidemic Diseases." Although the text of this oration is readily available in the 1936 Commonwealth Fund facsimile reprint of Snow's more famous cholera studies, few modern epidemiologists are familiar with the work. In it, Snow lays out a theory which includes recognition that for each communicable disease there is a distinct and specific cause, that the causal agent is a living organism which is stable over many generations of propagation, that infection is necessary for communication to occur, and that the quantity of infectious material transmitted is increased by multiplication after infection to produce disease manifestations. Although Snow's theory is similar to Jacob Henle's formulations of a decade earlier, it is more precise, more comprehensive, and more explicit. On the basis of this work alone, Snow deserves broader recognition than he has received.

Cholera↗
PubMed2000

Characterization of the microbial community of lotic organic aggregates ('river snow') in the Elbe River of Germany by cultivation and molecular methods.

Aerobic and anaerobic cultivation techniques, 16S rDNA-based phylogeny, and fluorescent in situ hybridization were used to describe the phylogenetic diversity and physiological versatility of lotic microbial aggregates ('river snow') obtained from the river Elbe. In the course of the year the 'river snow' community changed. It was characterized by a great bacterial diversity in spring, the predominant occurrence of algae in summer and reduction of the total bacterial cell count in autumn and winter. In all 'river snow' samples, more than 70% of the bacteria counted with the general DNA stain DAPI also hybridized with the Bacteria-specific probe EUB338. In situ analysis of the bacterial 'river snow' community with a comprehensive suite of specific rRNA-targeted probes revealed population dynamics to be governed by seasonal factors. During all seasons, beta-Proteobacteria constituted the numerically most important bacterial group forming up to 54% of the total cell counts. In contrast to this, the relative abundance of other major bacterial lineages ranged from 2% for the order Planctomycetales to 36% for Cytophaga-Flavobacteria. Cultivation of 'river snow' under aerobic and anaerobic conditions with a variety of different media resulted in the isolation of 40 new bacterial strains. Phenotypic and phylogenetic analyses revealed these new strains to be mostly unknown organisms affiliated to different bacterial phyla. Application of newly developed specific oligonucleotide probes proved the cultivated bacteria, including clostridia and the numerically abundant beta-Proteobacteria, as relevant in situ members of the 'river snow' community.

Journal Article↗
PubMed2006

Behavioral responses of bison and elk in Yellowstone to snowmobiles and snow coaches.

Managers of public lands are charged with protecting some of our most important natural resources and ecosystems, while providing for their use and enjoyment by visitors. Almost one million visitors entered Yellowstone National Park by motorized means on snowmobiles (87%) or snow coaches (13%) during 1992-2003. Most vehicles toured the central portion of the park where bison (Bison bison) and elk (Cervus elaphus) concentrate in geothermal areas. We sampled >6500 interactions between groups of these species and groups of snowmobiles and snow coaches (collectively, OSV, over-snow vehicles) during five winters (1999-2000, 2002-2004). Multinomial logits models were used to identify conditions leading to behavioral responses. Elk responded three times as often (52%) as bison (19%) during interactions with groups of snowmobiles and snow coaches due to increased vigilance responses (elk, 44%; bison, 10%). However, the frequency of higher-intensity movement responses by bison and elk were similar (6-7% travel, 1-2% flight, <1% defense) and relatively low compared to other studies of ungulates and snowmobile disturbance. The likelihood of active responses by bison and elk increased significantly if animals were on or near roads, groups were smaller, or humans approached. The likelihood of an active response by bison decreased within winters having the largest visitation, suggesting some habituation to snowmobiles and snow coaches. There was no evidence that snowmobile use during the past 35 years affected the population dynamics or demography of bison or elk. Thus, we suggest that regulations restricting levels and travel routes of over-snow vehicles (OSVs) were effective at reducing disturbances to bison and elk below a level that would cause measurable fitness effects. We recommend park managers consider maintaining OSV traffic levels at or below those observed during our study. Regardless, differing interpretations of the behavioral and physiological response data will continue to exist because of the diverse values and beliefs of the many constituencies of Yellowstone.

Animals↗
PubMed2003

Snow metamorphism as revealed by scanning electron microscopy.

Current theories of snow metamorphism indicate that sublimating snow crystals have rounded shapes, while growing crystals have shapes that depend on growth rates. At slow growth rates, crystals are rounded. At moderate rates, they have flat faces with rounded edges. At fast growth rates, crystals have flat faces with sharp edges, and they have hollow faces at very fast growth rates. The main growth/sublimation mechanism is thought to be by the homogeneous nucleation of new layers at or near crystal edges. It was also suggested that the equilibrium shape of snow crystals would be temperature dependent: rounded above -10.5 degrees C, and faceted below. To test these paradigms, we have performed SEM investigations of snow samples having undergone metamorphism under natural conditions, and of snow samples subjected to isothermal metamorphism at -4 degrees and -15 degrees C in the laboratory. In general, current theories predicting crystal shapes as a function of growth rates, and of whether crystals are growing or sublimating, are verified. However, the transition in equilibrium shapes from rounded to faceted at -10.5 degrees C is not observed in our isothermal experiments that reveal a predominance of rounded shapes after more than a month of metamorphism at -4 and -15 degrees C. Some small crystals with flat faces that also have sharp angles at -15 degrees C, are observed in our isothermal experiments. These faces are newly formed, and contradict current theory. Several hypotheses are proposed to explain their occurrence. One is that they are due to sublimation at emerging dislocations.

Crystallization↗
PubMed1992

Effect of age and coronary artery disease on response to snow shoveling.

OBJECTIVES: The objective of this study was to evaluate the effect of age and coronary artery disease on responses to snow shoveling. BACKGROUND: Little information is available on the hemodynamic and metabolic responses to snow shoveling. METHODS: Sixteen men with asymptomatic coronary artery disease and relatively good functional work capacity, 13 older normal men and 12 younger normal men shoveled snow at a self-paced rate. Oxygen consumption, heart rate and blood pressure were determined. In nine men with coronary artery disease left ventricular ejection fraction was evaluated with an ambulatory radionuclide recorder. RESULTS: Oxygen consumption during snow shoveling differed (p < 0.05) among groups; it was lowest (18.5 +/- 0.8 ml/kg per min) in those with coronary artery disease, intermediate (22.2 +/- 0.9 ml/kg/min) in older normal men and highest (25.6 +/- 1.3 ml/kg/min) in younger normal men. Percent peak treadmill oxygen consumption and heart rate with shoveling in the three groups ranged from 60% to 68% and 75% to 78%, respectively. Left ventricular ejection fraction and frequency of arrhythmias during shoveling were similar to those during treadmill testing. CONCLUSIONS: During snow shoveling 1) the rate of energy expenditure selected varied in relation to each man's peak oxygen consumption; 2) older and younger normal men and asymptomatic men with coronary artery disease paced themselves at similar relative work intensities; 3) the work intensity selected represented hard work but was within commonly recommended criteria for aerobic exercise training; and 4) arrhythmias and left ventricular ejection fraction were similar to those associated with dynamic exercise.

Adult↗
PubMed2003

Rate of evolution of the specific surface area of surface snow layers.

The snowpack can impact atmospheric chemistry by exchanging adsorbed or dissolved gases with the atmosphere. Modeling this impact requires the knowledge of the specific surface area (SSA) of snow and its variations with time. We have therefore measured the evolution of the SSA of eight recent surface snow layers in the Arctic and the French Alps, using CH4 adsorption at liquid nitrogen temperature (77 K). The SSA of fresh snow layers was found to decrease with time, from initial values in the range 613-1540 cm2/g to values as low as 257 cm2/g after 6 days. This is explained by snow metamorphism, which causes modifications in crystal shapes, here essentially crystal rounding and the disappearance of microstructures. A parametrization of the rate of SSA decrease is proposed. We fit the SSA decrease to an exponential law and find that the time constant alpha(exp) (day(-1)) depends on temperature according to alpha(exp) = 76.6 exp (-1708/7), with Tin kelvin. Our parametrization predicts that the SSA of a snow layer evolving at -40 degrees C will decrease by a factor of 2 after 14 days, while a similar decrease at -1 degrees C will only require 5 days. Wind was found to increase the rate of SSA decrease, but insufficient data did not allow a parametrization of this effect.

Adsorption↗
PubMed2005

Traffic as a source of organophosphorus flame retardants and plasticizers in snow.

Snow samples collected in northern Sweden at a road intersection and an airport indicated that traffic is a source of organophosphorus flame retardants and plasticizers (OPs) in the outdoor environment. Analysis of snow samples taken at distances of 2, 100, and 250 m from the road intersection showed that the total amount of OPs declined as distance increased. Of the 11 analyzed substances, tris-(2-chloroisopropyl) phosphate (TCPP) dominated in the snow samples from the intersection, with levels of 170, 130, and 110 ng/kg snow at distances of 2, 100, and 250 m. Similar amounts of TCPP were found at the airport (100-220 ng/kg). These levels are approximately twice as high as the level found in the reference snow sample from a remote area (70 ng/kg). A possible explanation for the higher levels of TCPP found close to the road intersection is that it may be emitted from the interior of cars via their ventilation systems. Triphenyl phosphate (TPP) was identified in lubricants and in waste oil from vehicles, and thus, leakage of transmission and motor oils is a probable source of TPP found at the sampled sites. Ten OPs were detected in the three samples from the airport, of which tributyl phosphate (TBP) was the most abundant, at levels 3 orders of magnitude higher than in the reference sample, that is, 25 000 compared to 19 ng/kg. The main source of TBP at the airport was traced to aircraft hydraulic fluid. Analysis of background air and deposition samples indicated that some OPs are subject to long-range air transportation.

Air Pollutants↗
PubMed2002

Falls from rooftops after heavy snowfalls: the risks of snow clearing activities.

Many patients present to emergency departments as a result of falling from a roof while shoveling snow. This study was undertaken to determine whether the frequency of such falls increases after large snowfalls, and to describe associated injuries. We reviewed the records of all patients presenting with cause of injury codes (E-codes) related to a fall: (E882, E881, and E884.9). We compared the frequency with which snow-shoveling related falls from roofs occurred on days with and without snowfalls greater than 12 inches. Fifty-nine patients met inclusion criteria. Patients were more likely to fall from a roof while shoveling snow on days with greater than 12 inches of snow accumulation than on days with less than 12 inches of snow accumulation (12/14 v 2/45, P <.001). Injuries included spinal fractures, extremity fractures, and head injury. These results suggest a need for public service campaigns emphasizing the risks of roof shoveling.

Accidental Falls↗
PubMed2005

Blowing snow at Mizuho station, Antarctica.

Blowing snow observations were carried out at Mizuho station, Antarctica, from October to November 2000. A blowing snow observation system including snow particle counters, which can sense not only the number of snow particles, but also their diameters, was situated on a 30 m tower. All instruments worked correctly and the data obtained revealed profiles of mass flux and particle size distributions as a function of the friction velocity. Measurements were compared with a blowing snow model that accounted for most physical processes including aerodynamic entrainment, grain/bed collisions, wind modification, particle size distribution and turbulent fluctuations on the particle trajectories. Simulated and measured results showed close agreement, and the validity of the model was demonstrated. Vertical profiles of horizontal mass flux from saltation to suspension, as well as the particle size distributions were expressed precisely, which could not be achieved using the previous models.

Antarctic Regions↗
PubMed1997

GPS signal reception under snow cover: a pilot study establishing the potential usefulness of GPS in avalanche search and rescue operations.

Avalanches are one of the major threats to life in high-mountain terrain and account every year for approximately 150 accidents causing injury or death in the United States alone. Every year avalanches cause significant property damages and a death toll of approximately 15 people in the United States. The specific characteristic of the avalanche accident is the extreme importance of getting to the buried victim as soon as, possible to improve survival. Approximately 40% of all buried victims survive 1 hour, and only about 20% survive 2 hours. Newer studies from Europe indicate that the initial survival probability is 92% at 15 minutes, 30% at 35 minutes, 27% at 90 minutes, and finally drops to 3% at 130 minutes. Unless prompt and efficient search and rescue are ensured, the prospect of buried victims is rather grim. Many tools have been used in the past to aid in retrieving buried victims including the avalanche cord, probing techniques, and in more recent time, the use of electronic beacon devices that allow search teams to locate the buried victim. The advent of satellite navigational aids (GPS, GLONASS) makes it possible to determine one's position with remarkable accuracy. We studied the degree to which the GPS satellite signal could penetrate through snow and be received by a commercially available GPS receiver. This information may lead to the development of an additional tool for precise and quick localization of buried victims in avalanche accidents and thus may substantially improve their survival by shortening the search time at the accident site. In this study we used a Motorola Traxar six-channel GPS receiver with amplifier unit connected to an antenna by means of a shielded coaxial cable. The antenna was buried under incremental covers of compact snow, and the reception of the GPS signal was measured at each burial depth: 5 cm, 15 cm, 25 cm, 35 cm, 45 cm, 55 cm, 1 m, and 1.5 m. The variables that were measured included signal quality, number of satellites received by the receiver, and their respective signal strength. A reference reading was taken from the GPS receiver above the testing site before measurements under snow cover were started. The satellite signals were received with good quality and precise readings up to a burial depth of 1 m. Under 1.5 m of snow the receiver was able to lock on only one satellite, making a positional reading impossible. The reception of the GPS signals under snow cover is possible and warrants further study directed toward the development of a search and rescue device using this technology.

Asphyxia↗
PubMedDate not supplied

Influence of manure application on surface energy and snow cover: model development and sensitivities.

Winter landspreading is an important part of manure management in the U.S. Upper Midwest. Although the practice is thought to lead to excessive P runoff losses, surprisingly little has been learned from field experiments or current water quality models. We captured knowledge gained from winter manure landspreading experiments by modifying a mechanistic snow ablation model to include manure. The physically based, modified model simulated the observed delay in snow cover disappearance and surface energy balance changes caused by application of the manure. Additional model simulations of surface energy balance estimates of radiation and turbulent fluxes showed that during intense melting events the manure on top of snow significantly reduced the energy available for melt of the snow underneath, slowing melt. The effect was most pronounced when snowmelt was driven by both relatively high solar radiation and turbulent heat fluxes. High absorbed shortwave radiation caused significant warming of the manure, which led to substantial losses in turbulent fluxes and longwave radiation. Simulations of snowmelt also showed that manure applications between 45 and 100 Mg ha(-1) significantly reduced peak snowmelt rates, in proportion to the manure applied. Lower snowmelt rates beneath manure may allow more infiltration of meltwater compared with bare snow. This infiltration and attenuated snowmelt runoff may partially mitigate the enhanced likelihood of P runoff from unincorporated winter-spread manure.

Agriculture↗
PubMed2002

Wastewater reclamation for use in snow-making within an alpine resort in Australia--resource rather than waste.

The Mt Buller Alpine Resort is located approximately 200 km north of Melbourne, in Victoria, Australia. A wastewater treatment plant services the resort and currently treats to advanced nutrient removal standards. The treated effluent is presently discharged into the Howqua River. Most Australian ski resorts are not blessed with abundant snow cover on a regular basis. Artificial snow allows most of the popular ski runs to operate for the whole of the season. At the Mt Buller resort, snow-making is presently limited by lack of water supply in the catchment. The conditions at Mt Buller resort present a unique opportunity to utilise reclaimed wastewater to allow increased snow-making capacity. It is one of the unique opportunities where the wastewater is valued as a resource rather than merely viewed as a waste problem. Wastewater reclamation for snow-making will require additional treatment for pathogen removal. It is proposed that following advanced nutrient removal, the effluent will require further treatment, including membrane ultrafiltration, so as to ensure a minimum of four barriers for pathogen removal. Pilot plant operation of a membrane ultrafiltration system commenced in June 2000 and will continue until the end of 2001, to primarily demonstrate the extent of pathogen removal.

Australia↗