Low Water Temperature Conditions Research Articles

Maximized thermal energy utilization of surface water-source heat pumps using heat source compensation strategies under low water temperature conditions

Surface water-source heat pumps (SWHPs) are expected to replace conventional cooling and heating systems owing to their high energy efficiencies. However, the risk of freezing during heating operations makes it impossible to operate SWHPs when the surface water temperature approaches the freezing point. Accordingly, this study proposes a heat source compensation operation for maximizing the use of the water's thermal energy, allowing the SWHP to use the thermal energy storage as a supplementary heat source at low river water temperatures. The performance characteristics of a compensation-based water-source heat pump (CWHP) and hybrid compensation-based water-source heat pump (HCWHP) are analyzed using a transient simulation tool under various operating conditions. Their environmental and economic performances are also analyzed and compared with those of a conventional cooling and heating system (CCHS) based on water temperature measurements of the Han River in South Korea. As a result, the CWHP shows a 10.6 % lower lifecycle climate performance and 20.2 % lower lifecycle cost (LCC) than the CCHS. The HCWHP exhibits the lowest greenhouse gas emissions in all periods but shows a 19.5 % higher LCC than the CWHP.

In response to the subject of forensic diagnosis of a human death caused by exposure to low-temperature water

BACKGROUND: Examining corpses recovered from the water often poses challenges in forensic medical evaluation.
 AIM: To propose a clarifying set of differential diagnostic features characteristic of a fatal cold injury in low-water temperature conditions.
 MATERIALS AND METHODS: Clinical observations, forensic examination of the corpses of patients who died from general hypothermia and drowning in ice water.
 RESULTS: A complex of the most apparent diagnostic signs for the differential diagnosis of acute deep hypothermia in water from other types of hypothermia and drowning was revealed.
 CONCLUSION: Morphofunctional changes in the internal organs have always been determined by hypothermias type, degree, and speed. The most characteristic signs of a fatal cold injury in low-water temperature conditions were determined by the state of the blood supply and the structure of organs and tissues. Pathological changes developed according to the type of edema, focal ischemia, and focal necrosis.

Benthic-pelagic coupling under juvenile oyster influence in a French Mediterranean coastal lagoon (Thau Lagoon)

The aim of the present work was to test the influence of juvenile oyster culture on benthic-pelagic coupling in the French Mediterranean Thau Lagoon. Although the period of juvenile growth induces the introduction of millions of juvenile oysters in the lagoon over a short duration, the effects on the water-column and on the benthic ecosystem are poorly known. Using a multiple ecological approach, water column parameters, sedimentation rates, sediment characteristics and benthic fluxes were monitored on three occasions during the oyster pre-growth period, from October to December, at two sites inside the farming area and two sites outside the farming area that served as reference. In the water column, results showed a significant lower ratio between total phytoplankton biomass (chlorophyll-a) and degraded pigments (pheopigment), a significant increase in the contribution of phytoplankton containing chlorophyll-b (ie chlorophytes) to total phytoplankton biomass and a significant decrease in the contribution of phytoplankton containing chlorophyll-c (mainly diatoms) to the total phytoplankton biomass at farm sites, attributed to the grazing pressure caused by juvenile oysters on large particles, as described for adult oysters. No significant effect was observed at the benthic interface during this period, due to the dispersion of the small quantities of biodeposit produced by juveniles in the low water temperature conditions. A multivariate approach supported the effect of juvenile oysters on the water column and revealed a trend in benthic conditions with farm sites being distinct from the reference ones. The long farming history of the lagoon could have shaped sediment properties such that farming areas maintain different benthic conditions.

Survival of purebred and hybrid Serrasalmidae under low water temperature conditions

The aim of the study was to evaluate the survival of Serrasalmidaes fish, pure and hybrid, during periods of low temperature. The experiment was carried out from June to August 2016 (51 days) in an aquaculture station of São Paulo Agribusiness Technology Agency, Brazil. A diallel crossbreeding between pacu and tambaqui was performed by artificial reproduction, generating four genetic groups: pacu (♂ pacu × ♀ pacu), tambaqui (♂ tambaqui × ♀ tambaqui), paqui (♂ tambaqui × ♀ pacu), and tambacu (♂ pacu × ♀ tambaqui). Fish were distributed in 24 experimental plots (110 fingerlings of each groups per plot) and were fed twice daily with commercial diets containing three different levels of crude protein (CP): 24%, 28% and 32%. When the water temperature showed successive decreases due to the environmental climatic conditions, the ponds were monitored daily to record the mortality. The data on number of days of life of animals were submitted to Cox multivariate regression analysis to test the effects of the genetic group, CP levels and the interaction between the two factors. Kaplan-Meier survival curves were adjusted for factors that had a significant effect on the Cox regression analysis. The pacu group presented higher survival than other groups, regardless of the CP level in the diet. The tambaqui and paqui groups were more susceptible to environmental conditions, especially when fed a diet containing a higher level of CP. Overall, purebred pacu presented greater adaptation to the production conditions in the region where the experiment was carried out. However, if the aim is the production of hybrid fish, crosses between pacu males and tambaqui females (Tambacu) generate fish that are resistant to low temperatures.

Performance evaluation of the sulfur-redox-reaction–activated up-flow anaerobic sludge blanket and down-flow hanging sponge anaerobic/anoxic sequencing batch reactor system for municipal sewage treatment

A sulfur-redox-reaction–activated up-flow anaerobic sludge blanket (UASB) and down-flow hanging sponge (DHS) system, combined with an anaerobic/anoxic sequencing batch reactor (A2SBR), has been used for municipal sewage treatment for over 2years. The present system achieved a removal rate of 95±14% for BOD, 74±22% for total nitrogen, and 78±25% for total phosphorus, including low water temperature conditions. Sludge conversion rates during the operational period were 0.016 and 0.218g-VSSg-COD-removed−1 for the UASB, and DHS, respectively, which are similar to a conventional UASB–DHS system, which is not used of sulfur-redox-reaction, for sewage treatment. Using the sulfur-redox reaction made advanced treatment of municipal wastewater with minimal sludge generation possible, even in winter. Furthermore, the occurrence of a unique phenomenon, known as the anaerobic sulfur oxidation reaction, was confirmed in the UASB reactor under the winter season.

Photosynthetic Performance of Marestail (<i>Hippuris vulgaris</i> Linn.) across a Water Temperature Gradient

we examined the photosynthetic responses of submerged marestail in three lakes using pulse amplitude modulated (PAM) fluorometry. Three lakes were studied across a gradient of water temperature, with low water temperature conditions in Grass Lake and Arrow Bamboo Lake, and higher water temperature in Five Colored Lake. In the field, electron transport rates (ETRmax) were measured as rapid light curves (RLCs) by in situ yield measurements. Submerged marestail showed higher photosynthetic activity in Five Colored Lake compared to the other lakes, a response consistent with the adaptation of marestail in Five Colored Lake to high water temperature. The optimal temperature for photosynthesis of submerged marestail in Jiuzhaigou is about 12 °C. These results indicate that in different lakes the function of these aquatic plants is associated with a diversity of place-dependent environmental conditions, especially water temperature that leads to pronounced differences in the plant’s ecophysiological reactions.

有害珪藻 <i>Asteroplanus karianus</i> の有明海佐賀県海域における出現動態と各種環境要因との関係

ノリの色落ち原因珪藻 Asteroplanus karianus の出現動態と環境要因との関係を調べるため，2007 年 12 月から 2012 年 3 月に有明海佐賀県海域で，植物プランクトン組成および各種環境要因を調査した。また，高水温および低水温条件下における本種の増殖および発芽特性を室内試験で調べた。その結果，本種は冬季にのみ赤潮を形成することが確認された。また，本種の増殖速度は低水温よりも高水温条件下で高いことが確認されたが，底泥中の休眠期細胞が発芽に要する時間は低水温条件下で短いことが示唆された。

Swimming activities of zoospores in Laminaria japonica (Phaeophyceae)

: The release of zoospores from zoosporangia in Laminaria japonica mainly occurred at night. The maximum swimming speed of the zoospores was observed immediately after release (~160 μm/s), and then decreased with time. The zoospores exhibited clear chemotaxis to high concentrations of nitrate-N and phosphate-P. Only half of the zoospores were observed to swim against seawater with a flow velocity of 124 μm/s. The zoospores became floating spores after they stopped swimming in the seawater. Low light and low water temperature conditions prolonged the swimming period of the zoospores. However, the photosynthesis of the zoospores was suppressed in low water temperatures, and was also limited under high light irradiance. These results suggest that photosynthesis in zoospores does not prolong their swimming period, and that when their swimming energy is exhausted, floating spores appear.

Distribution of cyanobacteria and other picophytoplankton in the western North Pacific Ocean, Summer 1989

Cell densities of phycoerythrin-fluorescing cyanobacteria and other chlorophyll-fluorescing picophytoplankton in the 0.2–2.0 µm size fraction were investigated, using an epifluorescence microscope, in the western North Pacific Ocean (36.5–44.0 °N, 155.0°E) in the summer of 1989. Cyanobacteria were most abundant in the surface of the subtropical water (36.5–38.0°N) and less in the northern sea area (39.5–44.0°N). The cell density of other picophytoplankton was, however, high in the northern part and low in the subtropical water. Results showed that algae other than cyanobacteria may significantly contribute to the picophytoplankton community under the low water temperature conditions of open waters. Chlorophylla concentration represented well the abundance of picophytoplankton other than cyanobacteria, but had no significant correlation with the cyanobacteria cell density. Chlorophylla-based data must be interpreted with caution, since the abundances of cyanobacteria were often considerably different even though the chlorophylla concentrations were the same level.