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PubMedDate not supplied

Hand injuries from snow blowers: a report of an epidemic.

During a record snowfall in Worcester, Massachusetts, 11-13 December 1992, 37 male patients with hand injuries suffered during snow blower operation were seen at three area hospitals. Two previous reports describe 13 patients seen over a 3-year period and 28 patients over a 12-year period. This report describes the largest number of hand injuries from snow blowers that have occurred over a 48-hour period. The snow was unusual because of the high water density in the initial 9 inches (23 cm) that fell at an average temperature of 33 degrees F (0.6 degree C) with the final depth of 30 inches (76 cm), causing the machines to become clogged. Patients admitted to reaching into a running machine in 35/37 (95%) cases, 11/37 (30%) claimed the auger and impeller blades were disengaged, and 2/37 (5%) patients claimed their injuries occurred with the engines turned off. All injuries occurred when the patients placed their hands down the chute, contacting the impeller blades. Injuries involved 32 long, 15 ring, 13 index, and five small fingers and ranged from simple lacerations to partial phalangeal amputations. The majority, 27/37 (73%), were managed in emergency departments without interventions in the operating suites. Infection occurred in one patient who had the lesion repaired in the operating suite. As in previous studies, no differences were found for the variables of snow-blower age, type, or horsepower, or on experience level or age of the operators.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2004

Sorption of diverse organic vapors to snow.

Sorption from air to one snow sample has been measured for a broad set of organic vapors covering a wide range of physicochemical properties. Those results that could be compared to literature values mostly lay in the same order of magnitude. As expected, a fit with the vapor pressure did not reveal a good correlation (R2 = 0.11). Therefore, the data set was interpreted with a linear free energy relationship, based on intermolecular interactions (van der Waals interactions and hydrogen bond interactions). Although we cannot assign the observed sorption to a specific process (adsorption to the snow crystal surface, incorporation in the solid ice crystal, absorption into a quasi-liquid layer, or grain boundary effects), the model provides a useful tool for the prediction of snow sorption for other compounds: log K(i snow suface/air) = 0.639 (+/- 0.037) log K(i hexadecane/air) + 3.38 (+/- 0.17) sigmabetai + 3.53 (+/- 0.25) sigmaalphai - 6.85. The sorption coefficients measured could be described well with the compound parameters used (subscript i), with an R2 = 0.90.

Adsorption↗
PubMed2005

Trace analysis of semivolatile organic compounds in large volume samples of snow, lake water, and groundwater.

An analytical method was developed for the trace analysis of a wide range of semivolatile organic compounds (SOCs) in 50-L high-elevation snow and lake water samples. The method was validated for 75 SOCs from seven different chemical classes (polycyclic aromatic hydrocarbons, organochlorine pesticides, amides, triazines, polychlorinated biphenyls, thiocarbamates, and phosphorothioates) that covered a wide range of physical-chemical properties including 7 orders of magnitude of octanol-water partition coefficient (log K(ow) = 1.4-8.3). The SOCs were extracted using a hydrophobically and hydrophilically modified divinylbenzene solid-phase extraction device (modified Speedisk). The average analyte recovery from 50 L of reverse osmosis water, using the modified Speedisk, was 99% with an average relative standard deviation of 4.8%. Snow samples were collected from the field, melted, and extracted using the modified Speedisk and a poly(tetrafluoroethylene) remote sample adapter in the laboratory. Lake water was sampled, filtered, and extracted in situ using an Infiltrex 100 fitted with a 1-microm glass fiber filter to trap particulate matter and the modified Speedisk to trap dissolved SOCs. The extracts were analyzed by gas chromatographic mass spectrometry with electron impact ionization and electron capture negative ionization using isotope dilution and selective ion monitoring. Estimated method detection limits for snow and lake water ranged from 0.2 to 125 pg/L and 0.5-400 pg/L, respectively. U.S. historic and current-use pesticides were identified and quantified in snow and lake water samples collected from Rocky Mountain National Park, CO. The application of the analytical method to the analysis of SOCs in large-volume groundwater samples is also shown.

Chemistry Techniques, Analytical↗
PubMed2006

Measuring the release of organic contaminants from melting snow under controlled conditions.

The release of organic contaminants from a melting snowpack may result in temporary concentration peaks in receiving water bodies and respective pulse exposure of aquatic organisms. It is thus of considerable interest to gain a mechanistic and quantitative understanding of the processes determining the dynamic behavior of organic chemicals during snowmelt. Uniformly structured and contaminated snow was produced with the help of a newly designed snow gun and exposed to predetermined temperature conditions in a temperature-controlled cold room. The dry density and liquid water content during four freeze-thaw cycles was recorded continuously at different layers within the snowpack using time domain reflectometry, providing information on meltwater production and propagation as well as snow metamorphism. Fractionated meltwater samples were filtered and the dissolved and particle phase analyzed for five polycyclic aromatic hydrocarbons (PAHs) using gas chromatography/ mass spectrometry. The distribution of the PAHs between the dissolved and particulate fractions of the meltwater was strongly related to their hydrophobicity. Particle-bound PAHs were released late during the snowmelt, whereas PAHs in the dissolved phase were released uniformly during a two day melting period. Even though conductivity measurements indicated a preferential early elution of ions in the first meltwater fractions, no such "first flush" behavior was observed for soluble PAH. The developed laboratory-based approach opens up for the first time the possibility of reproducible experiments on organic contaminant behavior in snow. Future experiments will explore, in detail, how the properties of organic chemicals, the physical and chemical properties of the snowpack, and the temperature variations before and during the time of melting interact to determine the timing of chemical release from a snowpack.

Climate↗
PubMed2005

Potential impacts of a warming climate on water availability in snow-dominated regions.

All currently available climate models predict a near-surface warming trend under the influence of rising levels of greenhouse gases in the atmosphere. In addition to the direct effects on climate--for example, on the frequency of heatwaves--this increase in surface temperatures has important consequences for the hydrological cycle, particularly in regions where water supply is currently dominated by melting snow or ice. In a warmer world, less winter precipitation falls as snow and the melting of winter snow occurs earlier in spring. Even without any changes in precipitation intensity, both of these effects lead to a shift in peak river runoff to winter and early spring, away from summer and autumn when demand is highest. Where storage capacities are not sufficient, much of the winter runoff will immediately be lost to the oceans. With more than one-sixth of the Earth's population relying on glaciers and seasonal snow packs for their water supply, the consequences of these hydrological changes for future water availability--predicted with high confidence and already diagnosed in some regions--are likely to be severe.

Aerosols↗
PubMed2026

A chromosome-level assembly of the alpine snow alga Chloromonas typhlos.

Chloromonas typhlos is a cosmopolitan alpine snow alga distributed across continents, and its blooming accelerates snow melting by decreasing the amount of snow albedo. To elucidate the genetic traits underlying the adaptation of C. typhlos to the alpine habitat, we combined PacBio sequencing and Hi-C to generate a high-quality chromosome-level genome assembly (contig N50: 1.29 Mb; scaffold N50: 7.23 Mb) with 31 chromosomes and a genome size of 200.86 Mb. Repetitive elements constituted 11.05% of the genome, and 16,133 protein-coding genes were predicted, of which 82% were functionally annotated. This study provides a set of omics resources both for snow algae and the genus Chloromonas.

Snow↗
PubMed2001

Effects of surface soil removal on dynamics of dissolved inorganic nitrogen in a snow-dominated forest.

To clarify the effect of vegetation and surface soil removal on dissolved inorganic nitrogen (N) dynamics in a snow-dominated forest soil in northern Japan, the seasonal fluctuation of N concentrations in soil solution and the annual flux of N in soil were investigated at a treated site (in which surface soil, including understory vegetation and organic and A horizons, was removed) and control sites from July 1998 to June 2000. Nitrate (NO3-) concentration in soil solution at the treated site was significantly higher than that of the control in the no-snow period, and it was decreased by dilution from melting snow. The annual net outputs of NO3- from soil at the treated site and control sites were 257 and -12 mmol m(-2) year(-1), and about 57% of the net output at the treated site occurred during the snowmelt period. NO3- was transported from the upper level to the lower level of soil via water movement during late autumn and winter, and it was retained in soil and leached by melt water in early spring. Removing vegetation and surface soil resulted in an increase in NO3- concentration of soil solution, and snowmelt strongly affected the NO3- leaching from treated soil and the NO3- restoration process in a snow-dominated region.

Ammonia↗
PubMed2003

Hypercapnia increases core temperature cooling rate during snow burial.

Previous retrospective studies report a core body temperature cooling rate of 3 degrees C/h during avalanche burial. Hypercapnia occurs during avalanche burial secondary to rebreathing expired air, and the effect of hypercapnia on hypothermia during avalanche burial is unknown. The objective of this study was to determine the core temperature cooling rate during snow burial under normocapnic and hypercapnic conditions. We measured rectal core body temperature (T(re)) in 12 subjects buried in compacted snow dressed in a lightweight clothing insulation system during two different study burials. In one burial, subjects breathed with a device (AvaLung 2, Black Diamond Equipment) that resulted in hypercapnia over 30-60 min. In a control burial, subjects were buried under identical conditions with a modified breathing device that maintained normocapnia. Mean snow temperature was -2.5 +/- 2.0 degrees C. Burial time was 49 +/- 14 min in the hypercapnic study and 60 min in the normocapnic study (P = 0.02). Rate of decrease in T(re) was greater with hypercapnia (1.2 degrees C/h by multiple regression analysis, 95% confidence limits of 1.1-1.3 degrees C/h) than with normocapnia (0.7 degrees C/h, 95% confidence limit of 0.6-0.8 degrees C/h). In the hypercapnic study, the fraction of inspired carbon dioxide increased from 1.4 +/- 1.0 to 7.0 +/- 1.4%, minute ventilation increased from 15 +/- 7 to 40 +/- 12 l/min, and oxygen saturation decreased from 97 +/- 1 to 90 +/- 6% (P < 0.01). During the normocapnic study, these parameters remained unchanged. In this study, T(re) cooling rate during snow burial was less than previously reported and was increased by hypercapnia. This may have important implications for prehospital treatment of avalanche burial victims.

Adult↗
PubMed2001

Normal oxygenation and ventilation during snow burial by the exclusion of exhaled carbon dioxide.

OBJECTIVE: To confirm that the accumulation of exhaled carbon dioxide (CO2) is the principal cause of nonmechanical asphyxiation during avalanche burial by demonstrating that complete exclusion of exhaled CO2 during experimental snow burial results in normal oxygenation and ventilation utilizing the air within the snowpack. METHODS: In the experimental group, 8 healthy volunteers (mean age 32 years, range 19-44 years) were fully buried up to 90 minutes in compacted snow with a density ranging from 300 to 680 kg/ m3 at an elevation of 2385 m. The 6 men and 2 women breathed directly from the snow utilizing a device containing no air pocket around the inhalation intake, in addition to an extended exhalation tube running completely out of the snowpack to remove all exhaled CO2. Continuous physiologic monitoring included oxygen saturation, end-tidal CO2, inspired CO2, electrocardiogram, rectal core temperature, and respiratory rate. As controls, 5 of the 8 subjects repeated the study protocol breathing directly into a small, fist-sized air pocket with no CO2 removal device. RESULTS: In the experimental group, the mean burial time was 88 minutes, despite the absence of an air pocket. No significant changes occurred in any physiologic parameters in this group compared to baseline values. In contrast, the controls remained buried for a mean of 10 minutes (P = .003) and became significantly hypercapnic (P < .01) and hypoxic (P < .02). CONCLUSIONS: There is sufficient oxygen contained within a densified snowpack comparable to avalanche debris to sustain normal oxygenation and ventilation for at least 90 minutes during snow burial if exhaled CO2 is removed. The prolonged oxygenation observed during CO2 exclusion is irrespective of the presence of an air pocket.

Adult↗
PubMed2002

Energy cost during locomotion across snow: a comparison of four types of snowshoes with snowshoe design considerations.

Snowshoes are a common method of locomotion across snow but no investigations has previously examined the energy cost of different snowshoe models or looked for desirable snowshoe design characteristics. To this end, four Marines were studied while walking at 4 km/h in four different types of snowshoes. They traversed a field with an average grade of 2.4%, walking once downhill and once uphill with each snowshoe. Expired respiratory gases (for energy cost measures) and heart rates were collected continuously during the walk. The Pride Assault and US Army Standard models had a lower energy cost than the Montana Light model and tended to have a lower cost than the British Assault model. Correlations between snowshoe mass/surface area ratios and energy cost were 0.81 and 0.72 on the uphill and downhill portions of the course, respectively. Examination of the physical attributes of the snowshoes suggested several design characteristics may be favorable from an energy cost perspective: 1) a hinge-and-binding system that allows the snowshoe to be dragged across the snow, 2) an upturned front that pushes snow away and allows a more horizontal (less vertical) displacement of the snowshoe during locomotion, 3) a narrow profile that avoids leg abduction, and 4) a lower mass to surface area ratio. Further research will be necessary to determine the importance of these factors because of the limited number of subjects and the single snow condition examined here.

Analysis of Variance↗
PubMed2003

Assessment and characterization of polychlorinated biphenyls near a hazardous waste incinerator: analysis of vegetation, snow, and sediments.

Samples of spruce needles, snowpack, and sediment were analyzed in the area around the Alberta Special Waste Treatment Centre (ASWTC) near Swan Hills, Canada, in 1997 and 1998, following a major accidental release of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) in October 1996. The PCB concentrations in spruce needles and snow were mostly elevated to the east of the plant and contained congeners that were not present at upwind or distant sites. Several years of annual vegetation monitoring data indicated that PCB emissions increased prior to the reported accident. Within 3 km of the plant, there was a predominance of higher chlorinated congeners penta-, hexa-, hepta-, and octachlorobiphenyls in white spruce (Picea glauca) needles and snow. Polychlorinated biphenyl congener patterns varied seasonally in spruce needles, likely influenced by temperature effects on the volatilization and of particle-bound and vapor phase PCBs in the forest canopy. The similarity of deposition patterns in snow and needles in 1997 and 1998 suggested the PCBs in the surrounding area were derived by long-term fugitive releases of PCBs rather than an accidental release. In addition, hexachlorobenzene, a combustion by-product of chlorinated organics in waste incinerators, was not measured at elevated concentrations in spruce needles or snow east of the facility and, when detected, was not correlated with PCB concentrations. A radiometrically dated sediment core from nearby Chrystina Lake (AB, Canada) showed a gradual increase in annual PCB flux during the early years of operation of the ASWTC, followed by a higher PCB flux in 1997, indicating that the lake may have been directly contaminated by the accidental release.

Alberta↗
PubMed2003

Siting, design and operational controls for snow disposal sites.

The Municipality of Anchorage (MOA), at 61 degrees north latitude, ploughs and hauls snow from urban streets throughout the winter, incorporating grit and chloride applied to street surfaces for traffic safety. Hauled snow is stored at snow disposal facilities, where it melts at ambient spring temperatures. MOA studies performed from 1998 through 2001 show that disposal site melt processes can be manipulated, through site design and operation practices, to control chloride and turbidity in meltwater. An experimental passive "V-swale" pad configuration tested by MOA investigators reduced site meltwater turbidity by an order of magnitude (to about 50 NTU from the 500 NTU typical of more conventional planar pad geometry). The MOA has developed new siting, design and operational criteria for snow disposal facilities to conform to the tested V-swale pad configuration.

Alaska↗
PubMed2003

Estimation of snow covered area for an urban catchment using image processing and neural networks.

This paper presents a method to estimate the snow covered area (SCA) for small urban catchments. The method uses images taken with a digital camera positioned on top of a tall building. The camera is stationary and takes overview images of the same area every fifteen minutes throughout the winter season. The images were read into an image-processing program and a three-layered feed-forward perceptron artificial neural network (ANN) was used to calculate fractional snow cover within three different land cover types (road, park and roofs). The SCA was estimated from the number of pixels with snow cover relative to the total number of pixels. The method was tested for a small urban catchment, Risvollan in Trondheim, Norway. A time series of images taken during spring of 2001 and the 2001-2002 winter season was used to generate a time series of SCA. Snow covered area was also estimated from aerial photos. The results showed a strong correlation between SCA estimated from the digital camera and the aerial photos. The time series of SCA can be used for verification of urban snowmelt models.

Cities↗
PubMed1979

[Studies on medico-legal diagnosis in cold district. 5. The blood shed on the snow (author's transl)].

By using bovine blood as a model, the authors have observed the forms and patterns of the blood drops shed or spurted on the snow and the extent of a large amount of blood absorbed in the deep snows, investigating the influence of the properties of snow upon them. It has been demonstrated that the polarographic method is most excellent for the purpose of determining the amount of blood absorbed in the snow.

Animals↗
PubMedDate not supplied

Irregular snow crystals: structural features as revealed by low temperature scanning electron microscopy.

For nearly 50 years, investigators using light microscopy have vaguely alluded to a unique type of snow crystal that has become known as an irregular snow crystal. However, the limited resolution and depth-of-field of the light microscope has prevented investigators from characterizing these crystals. In this study, a field-emission scanning electron microscope, equipped with a cold stage, was used to document the structural features, physical associations, and atmospheric metamorphosis of irregular snow crystals. The crystals appear as irregular hexagons, measuring 60 to 90 mm across, when viewed from the a-axis. Their length (c-axis) rarely exceeds the diameter. The irregular crystals are occasionally found as secondary particles on other larger forms of snow crystals; however, they most frequently occur in aggregates consisting of more than 100 irregular crystals. In the aggregates, the irregular crystals have their axes oriented parallel to one another and, collectively, tend to form columnar structures. Occasionally, these columnar structures exhibit rounded faces along one side, suggesting atmospheric metamorphoses during formation and descent. In extreme cases of metamorphoses, the aggregates would be difficult to distinguish from graupel. Frost, consisting of irregular crystals, has also been encountered, suggesting that atmospheric conditions that favor their growth can also occur terrestrially.

Journal Article↗
PubMed2001

The changing assessments of John Snow's and William Farr's cholera studies.

This article describes the epidemiological studies of cholera by two major British investigators of the mid-nineteenth century, John Snow and William Farr, and it asks why the assessments of their results by contemporaries was the reverse of our assessment today. In the 1840s and 1850s Farr's work was considered definitive, while Snow's was regarded as ingenious but flawed. Although Snow's conclusions ran contrary to the exceptations of his contemporaries, the major reservations about his cholera studies concerned his bold use of analogy, his thoroughgoing reductionism, and his willingness to ignore what seemed to be contrary evidence. Farr's electric use of current theories, his reliance multiple causation, and his discovery of a mathematical law to describe the outbreak in London in 1849 was much more convincing to his contemporaries. A major change in thinking about disease causation was needed before Snow's work could be widely accepted. William Farr's later studies contributed to that acceptance.

Anesthesiology↗
PubMed1989

John Snow and research.

John Snow's leadership in epidemiology as well as anaesthesia resulted from his research as much as his clinical practice. In anaesthesia, Snow's research concerned the regulation of concentrations of volatile agents and the development of efficient inhalers; the uptake and elimination of volatile agents; stages of anaesthesia; carbon dioxide metabolism and rebreathing; and metabolism in anaesthesia and the theory of anaesthesia. In epidemiology, Snow investigated the relationship of water supplies to mortality in cholera during the London epidemic in 1854, which led him to formulate an original and valid theory of the transmission of cholera. Snow's research, which has received less attention than anecdotes concerning his career (e.g., his anaesthetizing Queen Victoria and urging removal of the handle of a contaminated water pump), was always directed towards solving specific problems. The significance of his research is evident in its leading not only to improvements in health care but also to the evolution of anaesthesia and epidemiology as professional disciplines.

Anesthesia, Inhalation↗
PubMed2002

First investigation of an original device dedicated to the determination of gaseous mercury in interstitial air in snow.

The GAMAS (gaseous mercury in interstitial air in snow) instrument developed in our laboratory is a new device devoted to sampling and determination of gaseous mercury concentration in interstitial air in snow. Sampling probes inserted in the snowpack, coupled with a Gardis mercury vapour analyser, provide reliable and original data of vertical profiles of both snow temperature and gaseous mercury concentration at several depths in a snow mantle. This instrument has been tested successfully in Station Nord in Greenland in February-March 2002. A description of this instrument, of the sampling area and its setting up is presented with precise details. Illustrations of the first investigations are given showing a rapid decrease of gaseous mercury concentration simultaneously with depth. A concentration of 0.10 ng/m(3) is reached at 120 cm depth. It may be the result of fast oxidation processes occurring within the snowpack. Gaseous mercury behaviour in the snowpack is a central parameter to elucidate the fate of deposited mercury after mercury depletion events in polar regions. With our new device, we have now the opportunity to determine this key parameter.

Journal Article↗