Open Pools Research Articles

Sedge Succession and Peatland Methane Dynamics: A Potential Feedback to Climate Change

Under the warmer climate, predicted for the future, northern peatlands are expected to become drier. This drying will lower the water table and likely result in reduced emissions of methane (CH4) from these ecosystems. However, the prediction of declining CH4 fluxes does not consider the potential effects of ecological succession, particularly the invasion of sedges into currently wet sites (open water pools, low lawns). The goal of this study was to characterize the relationship between the presence of sedges in peatlands and CH4 efflux under natural conditions and under a climate change simulation (drained peatland). Methane fluxes, gross ecosystem production, and dissolved pore water CH4 concentrations were measured and a vegetation survey was conducted in a natural and drained peatland near St. Charlesde-Bellechasse, Quebec, Canada, in the summer of 2003. Each peatland also had plots where the sedges had been removed by clipping. Sedges were larger, more dominant, and more productive at the drained peatland site. The natural peatland had higher CH4 fluxes than the drained peatland, indicating that drainage was a significant control on CH4 flux. Methane flux was higher from plots with sedges than from plots where sedges had been removed at the natural peatland site, whereas the opposite case was observed at the drained peatland site. These results suggest that CH4 flux was enhanced by sedges at the natural peatland site and attenuated by sedges at the drained peatland site. However, the attenuation of CH4 flux due to sedges at the drained site was reduced in wetter periods. This finding suggests that CH4 flux could be decreased in the event of climate warming due to the greater depth to the water table, and that sedges colonizing these areas could further attenuate CH4 fluxes during dry periods. However, during wet periods, the sedges may cause CH4 fluxes to be higher than is currently predicted for climate change scenarios.

Analysis of feasibility on heating single family houses in rural areas by using sun and wind energy

Households in Lithuania consume about 1/3 of total final consumption of fuel energy. In order to reduce imports of fossil fuel and emissions of dangerous pollutants, solar energy could be used for the above-mentioned needs. That would require large collector areas and volumes for seasonal heat storage. In wintertime the wind speed velocity is much higher than in summertime in Lithuania. Therefore, it is advisable to study meeting the thermal needs of single family houses by combining use of wind and solar energy. To this end analytical research has been made by using deterministic method. The analysis has been carried out for the case when 1 m 2 of heated room area requires 0.25 m 2 of solar collector area and 0.5 m 2 working area of wind turbine rotor. Heat storage is planned for 24 h. By using such a hybrid system during the heating season 42.6–56.2% of heating needs for space and domestic hot water are satisfied. However, for individual days (especially from May to October) a surplus of generated heat is formed and it reaches about 53.6% of space heating needs per year. This relative surplus of energy could be used for transmitting wind power-plant energy to the electric network or in a household and thermal energy can be used for drying agricultural produce, heating greenhouses, open swimming pools and satisfying other needs.

Geophysical and hydrological evaluation of two bog complexes in a northern peatland: Implications for the distribution of biogenic gases at the basin scale

Ground penetrating radar (GPR) was used to determine peat basin geometry and the spatial distribution of free‐phase biogenic gasses in two separate units of a northern peatland (Central and Southern Unit of Caribou Bog, Maine). The Central Unit is characterized by a deep basin structure (15 m maximum depth) and a raised (eccentric) bog topographic profile (up to 2 m topographic variation). Here numerous regions of electromagnetic (EM) wave scattering are considered diagnostic of the presence of extensive free‐phase biogenic gas. In contrast, the Southern Unit is shallower (8 m maximum depth) and has a slightly convex upwards bog profile (less than 1 m topographic variation), and areas of EM wave scattering are notably absent. The biogenic gas zones interpreted from GPR in the Central Unit are associated with: (1) wooded heath vegetation at the surface, (2) open pools at the surface, (3) high water table elevations near the center of the basin, and (4) a region of overpressure (at approximately 5 m depth) immediately below the zone of free‐phase gas accumulation. The latter suggests (1) a transient pressure head associated with low hydraulic conductivity resulting from the biogenic gasses themselves or confining layers in the peat that restrict both gas release and groundwater flow and/or (2) overpressure in the peat column as a result of the gas buildup itself. In contrast, the Southern Unit, where zones of EM scattering are absent, is characterized by: (1) predominantly shrub vegetation, (2) a lack of open pools, (3) only minor variations (less than 1 m) in water table elevation throughout the entire unit; and (4) generally upward groundwater flow throughout the basin. The results illustrate the nonuniformity of free‐phase biogenic gas distribution at the peat basin scale and provide insights into the processes and controls associated with CH4 and CO2 accumulation in peatlands.

Pediatric Drowning

Drowning is a significant cause of childhood mortality in the developed world. Males and preschool-aged children are overrepresented in most series of pediatric drowning. To obtain a better understanding of age- and gender-related factors, a retrospective review of autopsy records over a 20-year period (1984-2003) for cases of drowning (exclusive of bathtub drownings) was performed. Sixty-three consecutive cases of drowning were identified in 45 males and 18 females (ratio 2.5; P = 0.0007). The ages ranged from 9 months to 17 years, and most cases occurred in the 0- to 4-year age group (57%). Boys tended to be older than girls (5 years 9 months versus 4 years 4 months; P = 0.2133). Sites of drowning were open water (48%) and pools (44%), with children drowning in open water being significantly older than those drowning in pools (6 years 6 months versus 4 years 6 months; P = 0.0462). Most boys drowned in open water (53%), whereas most girls drowned in pools (50%). Resuscitation was attempted after the drowning episode in 84% of cases, with children aged 4 years or less having significantly higher rates than older children (P = 0.0346). The present study highlights differences in the pattern of drowning according to age and sex and may aid in developing targeted educational and preventative campaigns.

Evaluation of Toyserkan City's Water Contamination, due to The Existence of Radon, and Estimation of The Annual Effective Dose

The gas of 222Rn is one of the natural radioactivesources which is the decay product of 226Ra from 238U decay chain. Based on the latest information presented bythe United Nations Scientific committee in the field of the effects of atomic radiations, the respiration of Radon and its daughters (Plutonium, Bismuth and Lead), are one of the most important factors in human radiation inhalation, since Radon and its daughters account for approximately 1.2 msv of the total of 2.4 msv (mili Sievert) annual effective dose of natural radioactive sources produced. The fluctuation in the levels of Radon resolved in water, due to the hazards caused by the emitted radiations, is considerable; because studies show that long-term exposure to Radon increases the chances of lung cancer. The amount of radon in underground waters is more than that of surface waters. If water is exposed to free air, especially when it’s mixed as well, a considerable amount of its radon content is released. In this paper, Radon concentration (Bq/L) in waters of the wells and springs located in Toyserkan, is measured using Lucas chamber technique by means of a light weighted and transportable machine namely PRASSI (SFLENAmod5s). The results showed that the radon density in four measured samples in the waters of this region exceed 10 Bq/L, the allowable amount determined by the US Environmental Protection Agency (USEPA). For the cases where the concentration is high, is it proposed that drinkable water be preserved in open pools or at least waterfalls be used in order to agitate the water to release itsradon content. It is better to install a system for settling and exposing the water to air so that Radon and its decay products are dispersed and the contamination problem is solved.

Behaviour, home‐range size and habitat use by male Great Bittern Botaurus stellaris in Britain

This paper describes the first use of radiotracking to follow closely the secretive Great Bittern Botaurus stellaris, and to quantify its reedbed habitat preferences at a fine scale. Eight males were tracked at two sites in Britain, at which they were mainly resident through the winter. Their median home‐range sizes were 14.6, 19.3 and 33.1 ha during the booming, moult and winter periods, respectively, and home‐ranges were, on average, composed of 30% open pools and 48% reedbed edge (of 30 m width). Great Bitterns were most often active in reed with 20 cm water depth within the 30‐m reed edge next to water, whereas areas of reedbed near scrub or further from the water's edge were avoided. Reed edge adjacent to open pools was preferred over that adjacent to channels and ditches. These results provide a basis for conservation recommendations on the quantity and composition of reedbed habitat and provide the scientific basis for a national programme of reedbed rehabilitation and restoration.

Stratigraphic controls on pool formation in a domed bog inferred from ground penetrating radar (GPR)

Ground penetrating radar (GPR) and terrain conductivity measurements reveal a close correlation between the location of water-filled pools and stratigraphic/lithologic features in Caribou Bog, a 2200-hectare peatland in central Maine. The geophysical profiles, supported by coring, define the general peatland stratigraphy as till underlain by glacio-marine sediment overlain by organic-rich lake sediment transitioning into terrestrial peat. GPR measurements show that open pools coincide with abrupt thinning of lake sediment and glaciomarine clay such that elevated mineral soil surfaces are in direct contact with the base of terrestrial peat. The width of these features, the GPR reflection patterns, the anomalously low terrain conductivity and the core samples obtained support the interpretation of these elevated mineral surfaces as the extension of buried eskers that outcrop on the periphery of Caribou bog. The geophysical results indicate that two parallel esker ridges are orientated N–S and dip towards the south. We suggest that the distribution of open pools is related to the distribution of depressions and beads associated with a beaded esker deposit, the pools possibly being maintained by local groundwater flow cells associated with the esker. GPR and EM31 surveys across Sphagnum pools (defined here as Sphagnum filled wet depressions) suggest a continuous sequence of underlying lake sediment and glacio-marine deposits devoid of elevated mineral surfaces. We suggest that Sphagnum pools developed after peatland formation (secondary features) due to changes in water table, peat accumulation and/or climatic controls.

Halbyggeri mellem fag, politik og økonomi

Sports hall construction caught between the profession, politics and the purseThis article looks at the political processes that from 1948 onwards led to the eventual construction of Aabenraa Swimming Pool and Sports Centre in the period 1971-73. The article concludes that it was the persistent demands of local people effectively supported by sporting organisations that at several crucial points made local politicians work towards the establishment of a swimming pool and in the end of a sports centre. As a result of the very slow political decision-making process, the politicians’ wishes and requirements for a swimming pool were overtaken not only by technological developments but also by the increasing demands of the welfare state for public bathing facilities, and this led in the mid-1960s to a violent schism in the town council. While at the end of the 1950s open air bathing and swimming pools could be regarded as providing the basic framework for elementary swimming instruction to prevent people drowning at the seaside, swimming pools developed during the 1960s into the welfare state’s alternative to public beaches. When in 1968 it at last became possible to unite the different views as to the purpose of the swimming pool, Friluftsloven (the Open Air Act) of the same year ended up playing a central role in the construction and maintenance of the centre. This, combined with ideologically based requirements that sport should be party to financing the construction of sports centres, still plays a decisive role today in determining the degree to which sports associations can make more substantial sporting investments in, for example, competitive sport.

Housing and Health Transition in Thailand

Over the past half-century, Thailand's health profile has been undergoiog an epidemiologic transition in association with various fundamental societal changes, shifting from one with a predominant burden of communicable disease to one in which noncommunicable diseases and accidents now predominate. The primary question is why have the disease rates in the Thai population changed? Answering this question requires an examination of the underlying transitions in social and contextual factors. This paper explores, using published data, how housing conditions, as one set of environmental health risks, have undergone transition in recent years and how this change maps on the health-transition process. A combination of economic development, urbanization, modernization, and increased health literacy resulted in a range of health-protecting changes in housing design and materials. Pre-eminent among such changes are improvements in household sanitation and in equipment, ventilation, and fuel pertaining to indoor cooking and heating. In tropical countries like Thailand, gains have been made in mosquito-proofing houses and in minimizing open pools of water to combat the risks of malaria, dengue fever, and other mosquito-borne infections. Meanwhile, the growth in shantytown and slum housing around the urban fringe, often in precarious environmental settings, introduced a negative dimension to the evolving profile of housing-related health risks, whereas the urban sprawl of modern residences creates health risks that are due to traffic crashes and the lack of walking in daily transport.

Variations of 18O/ 16O in plants from temperate peat bogs (Switzerland): implications for paleoclimatic studies

Despite the great potential of peat bogs as climatic archives, to date only few studies have focused on the climatic controls on cellulose isotopic composition in modern bog plants. This study attempts to calibrate plant–climate relationships by sampling a set of modern plant species (both vascular plants and mosses) and bog surface waters along an altitude transect in Switzerland. Isotopic analyses of water samples show that the δ 18O-values of surface bog waters follow the trend of precipitation despite significant scatter in the data set. Detailed sampling of surface waters within one bog shows that δ 18O-values vary widely and are closely related to the micro-topography of the bog surface. More enriched 18O/ 16O ratios in water samples collected from small raised hummocks than the ones collected from hollows are documented in both horizontal and vertical profiles. A δ 18O–δD plot indicates that the process leading to the isotopic enrichment of the uppermost surface waters is evaporation, greater above Sphagnum covered hummocks than above open pools. To investigate the implications of such high variability of source water for plant α-cellulose δ 18O-values, a detailed study of both surface water and α-cellulose δ 18O-values within one site is conducted. The large δ 18O variability observed in surface waters is found to be considerably smoothed in α-cellulose (by a factor of 5–10 depending on the plant species). This indicates that the water used by plant photosynthetic processes reflects the isotopic composition of the average annual precipitation. This points to a source water level for plants of a few decimeters where the variations are smaller than at the air–water interface. The response of the α-cellulose δ 18O to the environmental gradient along the altitude transect varies considerably from species to species. For most of the species studied, the δ 18O-values decrease with altitude, following the trends of δ 18O-values in precipitation and in surface water samples. Some species, the cotton sedge Eriophorum vaginatum and the moss Sphagnum capillifolium, show statistically significant δ 18O relationships to an altitude of −1.8‰/km and −2.9‰/km respectively. However, some other plant species, Calluna vulgaris, Vaccinium uliginosum, Andromeda poliflora, Carex pauciflora, Sphagnum cuspidatum and Sphagnum magellanicum, do not, or only partially, reflect changes in climatic parameters associated with an altitude increase. Furthermore, changes in relative humidity, which are not correlated with altitude, are found to explain a large part of the variability in δ 18O-values for the sedge Carex pauciflora and the moss Sphagnum cuspidatum. Therefore, this study confirms the importance of species-specific studies when interpreting 18O/ 16O ratios of macrofossils along a fossil peat sequence as a record of past climate changes. Our study allows to extend the mechanistic model that isotopically links source water and cellulose to the physiological specificities of sedges and mosses. A comparison of the modeled and calculated net biological fractionation factors for Eriophorum vaginatum and Sphagnum capillifolium reveals that these two species appear to have a more homogeneous leaf reservoir than trees.

Hydraulic Performance of an Annular Plunging Jet Reactor

Agas-liquid reactor is described, in which a plunging jet issues into a confined downcomer column, entraining headspace gas as it impinges onto the surface of a receiving pool of the same liquid. The two-phase mixture flows down the confining column and then rises through a concentric annulus, before disengaging in a separation vessel. Such a design gives increased gas-liquid contact times compared to jets plunging into open pools. Another feature of the current design is that it is straightforward to recycle both the gas and liquid phases from the separation, using only a single pump, thus ensuring almost complete utilization of the gaseous feed. A hydraulic model of the reactor is presented and tested against experimental data over a range of liquid flow rates and nozzle sizes. The agreement between the predictions and the experimental data indicates that the model provides a good basis for the design of this type of gas-liquid reactor. It is also shown that downcomers with diameter greater than 24 mm appeared to have little effect on the gas entrainment rate, when nozzles of 5 to 12 mm diameter were used. Smaller downcomers significantly reduced the gas volumetric entrainment flow rate.

Experimental Analysis of the Role of Emigration in Population Regulation of Desert Pupfish

Pupfishes (genus Cyprinodon) have existed for long periods in small desert springs and streams that often lack competitors, major predators, and large environmental changes. How their populations are regulated in these systems is poorly known. We experimentally examined the role of emigration in regulating populations of pupfish by (1) comparing the dynamics of populations held in four pools open to emigration with those of populations held in four pools closed to emigration over a 22—mo period and (2) comparing the rates of emigration from open pools having different densities of pupfish in relation to resources. When pupfish populations were prevented from emigrating, they exhibited symptoms of overpopulation similar to those well documented for fenced populations of small mammals. Their numbers increased more than populations in open pools, mortality was high, and body condition and recruitment were low. Again, as in small—mammal populations, these responses were absent in pupfish populations in open pools, where 84% of the total numbers of fish produced emigrated. The timing and magnitude of pupfish emigration was similar in all four open pools and was related to seasonal temperature changes. More males emigrated than females, and emigrants had significantly lower condition factors than residents. When densities of pupfish in relation to resources were doubled in two open pools, the percentages of pupfish that emigrated (41.8 and 42.2%) were almost equal to the 50% drop in resources. In contrast, only 15.5 and 16.0% emigrated from two control pools, where pupfish densities in relation to resources were left unchanged. Our results, demonstrating that emigration is a potentially significant mechanism for regulating populations of desert pupfish, are consistent with data from a variety of other animals (small mammals, hydra, roe deer), suggesting that population regulation via a behavioral spacing mechanism may be common among mobile animals.

Solar heating of open swimming pools

This communication presents a thermal model for the performance of an open swimming pool. It is seen from numerical calculations that the combination of a pool cover and solar collectors (with an area equal to 75 per cent of that of the pool) enables the swimming season to be extended in Delhi, India to forty-seven weeks as compared to the period of twenty-nine weeks for an open swimming pool.

Peatland water chemistry in Central Ontario in relation to acid deposition

Thirty-one peatlands from two areas of central Ontario were sampled to assess the influence of acid deposition on peatland water chemistry. Factor analysis differentiated peatland water chemistry along three major axes of chemical variation, interpreted as axes of organic concentration, mineral concentration, and deposition influence. Water from the surface mats had a higher organic concentration than water from open pools. Mineral influence in peatland waters was reflected by higher concentrations of Ca, Mg, Na, and silica in fen pools compared to bog pools. The influence of high acid deposition in the Wanapitei study area was indicated by high concentrations of sulphate, Ni, Mn, and Cu, and lower pH compared to an area that has received less acidic deposition (Ranger). Regression analyses indicated that H+ variation in bogs could be largely explained by organic C concentration, but that sulphate concentration was also positively associated with acidity, while Ca was negatively associated with acidity.

Organization of a community of tadpoles in rain forest streams in Borneo

ABSTRACTSamples of 29 distinct larval forms of anurans were collected in streams flowing through primary rain forest at Nanga Tekalit, Sarawak, at three periods spaced over 22 years. This assemblage of tadpoles lives in torrents, riffles, shingle areas, open pools, leaf drifts, protected side pools, potholes in rocky banks, bank seepages, and pools of small intermittent streams. Positive associations of species in types of microhabitats and co-occurrence within sites lead to recognition of four taxonomically heterogeneous groups: one concentrated in leaf drifts; one using riffles, shingle areas, and open pools; one concentrated in potholes; and one using side pools and potholes. Most pairs of larval forms having strong negative association are characterized by differences in morphology and feeding behaviour; they show little evidence of competitive relations. Between-sites variation in species composition differs among the types of microhabitats, leaf drifts showing the least amount of variation. Species composition within a site shows less change over intervals of 1–5 days than over intervals of 13–18 days. Variation in species composition is greater between sites than within sites over intervals of 9–31 days. Organization in this community seems to be effected by three factors: reproductive behaviour of adults and morphological and behavioural adaptations of tadpoles.

Selection of the optimal composition of connected pumps under conditions of functioning of an automatic process control system

1. The solution of problems of optimal selection of the number and composition of operating units for a given value of the total discharge of each pumping station will make it possible as a whole for the canal to reduce expenditures of electric energy for pumping the necessary volumes of water. 2. The mathematical approach to the solution of the given problem examined above is suitable for canals with open pools and with multiple-unit pumping stations having a considerable internal range of regulation.

Analytical evaluation of direct solar heating of swimming pools

An analytical model for the long term thermal performance of swimming pools is developed and shows that the solution for open pools is applicable to enclosed pools with appropriate modification of parameters. From this solution the seasonal heating load of swimming pools, open or closed, can be calculated analytically.

Ecological Studies of Culiseta Melanura (Diptera: Culicidae) in Relation to Eastern and Western Equine Encephalomyelitis Viruses on the Eastern Shore of Maryland

Mosquito larvae were caught by larval traps and dipping, and adults with CDC miniature light traps, vacuum sweeping, and other means near Pocomoke City, Maryland. Culiseta melanura (Coquillett) was caught in greatest numbers, persisted through the summer, and was the primary source of eastern and western equine encephalomyelitis (EEE and WEE) virus isolations. Larvae of C. melanura were found in “typical” sites, in crypts, in water held in the saturated root mat that forms the substratum of much of the swamp, and in freshly dug holes in the root mat, even in winter. Very few were found in open pools or in areas with mucky soil near the river. Some adult C. melanura emerged into funnels placed over “typical” breeding sites, and a few from the root mat into emergence traps which enclosed neither exposed water nor crypts. The catch of C. melanura in CDC miniature light traps appeared be influenced by temperature, cloud cover, precipitation, water table, and activity of the mosquitoes. Light traps captured more females than males. Vacuum sweep samples fluctuated less, had more males than females, a larger proportion of blood-engorged and gravid females, and a higher virus isolation rate than did the light trap samples. All but 1 of the C. melanura blood meals identified (191) were avian. Both Culex salinarius Coquillett, and Aedes canadensis (Theobald) contained bovine and avian blood. Dispersal of C. melanura increased in late summer, into the vicinity of nearby farms. In 1966, 1 isolation of EEE virus and 16 of WEE virus were made, all from female C. melanura ; in 1967, there was 1 isolation of EEE virus (from Culex salinarius ) and 8 of WEE virus (all from C. melanura , 1 of which was caught in a nearby farmyard).

The Role of Spring Thaw in String Bog Genesis

... it is necessary to establish a more thoroughly documented framework of current physical processes operating in string bogs throughout the year. It is to this end that the present note is directed. Two problems immediately present themselves in any discussion of string bog genesis. First, there is the need to explain the initial establishment and maintenance of the ridge-hollow pattern; and second, the related problem of the concentration of string bogs in the boreal forest. ... observations near Schefferville, Quebec (54°50'N, 67°W) in the spring of 1970 are specially pertinent to explaining patterns within string bogs. Permafrost is absent from beneath these string bogs. ... There is no doubt that in the subarctic, spring thaw is rapid and debris of various kinds is transported by the meltwater over the frozen surface of the bog. Several stages in the melt-transportation process can be recognized. 1) The thaw is first evident on the thin snow cover of the bog with the development of a mixture of slush, ice and open pools. 2) Additional melt involves the removal of snow from the surface of the bog. ... 3) Pools become linked as the volume of meltwater increases with advance of the thaw. ... 4) Continued and perhaps more rapid melt of snow lying adjacent to the bog from within the spruce forests, augments the sheet flow. ... 5) With the removal of the bog ice cover, sheet flow over the bog ceases, and the meltwater becomes more channelized. ... In the bog near Schefferville where these processes were observed, incipient accumulations of the type described were only noted at the upstream end of a bog in which strings had already been developed down-bog. Where strings were already in existence, the damming effect was most apparent, although its importance declined down-bog as the floating organic debris was trapped or filtered by plants up-bog. Lines of debris accumulation are therefore considered initially to develop into permanent sites for plant growth at the downstream end of the bog, and then progressively build in an up-bog direction always at right angles to flow patterns of spring meltwater. Younger strings, according to this view, will occur at progressively higher elevations within any given bog. ... it is assumed that the sites of detrital deposition become the preferred sites for plant growth because of their relatively better-drained condition. ... Once started, such a process will accelerate by its own effects. ... Although excavations in the Schefferville area were not conclusive, ... the hypothesis of in situ growth of strings was supported by bog stratigraphy. ... Emphasis is placed on the primary role of organic accumulations during early phases of the spring thaw, a period of the year when few observers have had the opportunity to examine such bogs. A vital role is attributed to the more intense plant growth on initial shallow deposits which leads to the formation of the ridge. Ice-push and frost heave appear to play secondary and perhaps localized functions. Solifluction, differential settling and tilting due to permafrost melt, and compaction of peats under varying loads, are not factors which appear to be of great importance in string bog development. There remain several critical problems which require further study ....

Static heat transfer to liquid helium in open pools and narrow channels

The transfer of heat to boiling liquid helium has been measured in open pools and narrow channels. In open pools a marked dependence of heat transfer on the orientation of the heated surface is observed. The maximum heat flux for nucleate boiling varies from 1 W/cm 2 with the heated surface horizontal facing upwards to about 0·1 W/ cm 2 with the surface horizontal facing downwards. In a narrow vertical channel the maximum heat flux is reduced to about 0·15 W/ cm 2 for a rectangular channel 10 mm × 1 mm (50 cm length), and appears to decrease linearly with the channel dimension. The heat transfer is considerably increased in the narrow channel when the fluid is pressurized.