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- Beauchard, Olivier, et al.
(författare)
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Trawling-induced change in benthic effect trait composition – A multiple case study
- 2023
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Ingår i: Frontiers in Marine Science. - 2296-7745. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The importance of the response-effect trait dichotomy in marine benthic ecology has garnered recent attention. Response traits, characterising species responses to environmental variations, have been a dominant focus in the development of ecological indicators for ecosystem health assessment. In contrast, effect traits, expressing effects of organism activities on the ecosystem, still do not benefit from an equal interest in spite of the complementary facet that they provide to complete our understanding of functional diversity and ecosystem vulnerability. In this study, we explore the consequences of disturbance by bottom trawl fisheries on benthic effect trait composition.Methods: To this end, we used different contexts of environmental and trawling conditions from thirteen case studies in European waters and apply the same analytical procedure to derive a gradient that solely account for trawling-induced disturbance (Partial RLQ analysis).Results: Bottom trawling was found to be a selective force of benthic effect trait composition in a majority of case studies. In general, tube-dwelling species were more typical of low trawling frequencies, whereas deep burrowing species were more resistant at high trawling frequencies. Although we report significantly deleterious effects of trawling on benthic ecosystem functions, the effect trait pattern along the gradient was never related to life span, a key response trait generally assumed to express recoverability following disturbance. Furthermore, we show that trends in species multi-functionality and community functional diversity can be negative or positive along the trawling intensity gradient.Discussion: We discuss the relevance of these results in light of recent developments in the framework of response and effect trait dichotomy, and provide guidelines of trait data analysis in the context of trawl fisheries impact on the sea floor. Our findings emphasize the importance of fundamental concepts from functional ecology in this context and represent a first step toward an assessment of trawling effect more oriented on benthos-mediated biogeochemical processes.
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| 2. |
- Björling, Mikael, et al.
(författare)
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Ventilation measurements combined with pollutant concentration measurements discriminates between high emission rates and insufficient ventilation
- 2007
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Ingår i: IAQVEC 2007 Indoor Air Quality Ventilation and Energy Conservation. ; , s. 393-400
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Konferensbidrag (refereegranskat)abstract
- High local concentrations of a pollutant can be the result of high local emission rates of the pollutant or insufficient ventilation. Using tracer gases to map the ventilation in multi-zone buildings combined with measurements of the local pollutant concentration provide the means to discriminate between these causes. In a similar manner, the propagation rate of pollutants from a source to a target zone and the emission rate of the pollutants at the source may be determined quantitatively.The paper presents both the theoretical framework for the techniques and experimental examples of the proposed methods.
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| 5. |
- Blomqvist, Claes, et al.
(författare)
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Air Movements through Horizontal Openings in Buildings – A Model Study
- 2004
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Ingår i: The International Journal of Ventilation. - : Informa UK Limited. - 1473-3315 .- 2044-4044. ; 3:1, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- A building contains a number of large openings like doors and staircases. When the temperature of the spaces connected by these openings differs, the difference in density will cause air movements through them. Horizontal air movements through vertical openings in buildings like doors and windows are well investigated while studies of air movements through horizontal openings like stairwells are less frequent and therefore this work is focusing on this case. The paper reports on an experimental study of the possibility of using buoyancy forces to distribute air and heat through horizontal openings. The experiments have been carried out in a scale model with water as the operating fluid. The result of the study shows that the flow rate through a horizontal opening is roughly half of the flow rate through a vertical opening for the same conditions, probably caused by the more complex flow pattern in the horizontal opening. A staircase below the horizontal opening will guide the flow somewhat and will cause a small increase of the fluid exchange through the opening.
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| 6. |
- Blomqvist, Claes, et al.
(författare)
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Conversion of electric heating in buildings An unconventional alternative
- 2008
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 40:12, s. 2188-2195
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Tidskriftsartikel (refereegranskat)abstract
- To decrease the electric energy used for heating buildings it has become desirable to convert direct electrical heating to other heat sources. This paper reports on a study of the possibility of using an unconventional method for conversion to avoid installing an expensive hydronic system. The conversion method combines the ventilation and heating systems and uses air instead of water for distribution of heat within the building, taking advantage of thermal forces and the special properties of gravity currents. Full-scale tests have been carried out in a test apartment inside a laboratory hall where the conditions could be controlled. Temperatures and efficiency of ventilation have been measured to ensure that the demands with respect to thermal climate and air exchange were fulfilled. The results show that it is possible to use the method for heating and ventilation when converting the heating system, but further work has to be done to develop a detailed solution that works in practice. (C) 2008 Elsevier B.V. All rights reserved.
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| 7. |
- Blomqvist, Claes, 1945-
(författare)
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Distribution of Ventilation Air and Heat by Buoyancy Forces inside Buildings : An Experimental Study
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main task of the ventilation system in a building is to maintain the air quality and (together with the heating or cooling system) the thermal climate at an acceptable level within the building. This means that a sufficient amount of ventilation air at the appropriate temperature and quality must be supplied to satisfy thermal comfort and air quality demands and that this air is distributed to the parts of the building where people reside. Air movements caused by buoyancy forces can determine the distribution of ventilation air within buildings. The purpose of this thesis is to advance the state of knowledge of buoyancydriven air movements within buildings and to determine their importance both for ventilation air distribution and the maintenance of thermal comfort and air quality in buildings. The work is focused on studying thermally-driven air movements through large openings, both horizontal and vertical (i.e. doorways). The properties of a special type of thermally-driven currents, so called gravity currents, have also been explored. Large vertical openings like doorways are important for air exchange between rooms within a building. Air movements through doorways separating rooms with different air temperatures are often bidirectional and the buoyancy-driven flow rates are often greater than those caused by the mechanical ventilation system alone. Bidirectional flows through doorways can effectively spread contaminants, for example, from a kitchen or a hospital rooms, yet the results of this study indicate that the conversion of a thermally-driven bidirectional flow to a unidirectional flow via an increase of the mechanically forced flow rate requires forced flows that are more than three times greater than the thermally-driven flows. Experiments conducted in this project indicate that the resistance to buoyancy-driven flows in horizontal openings is significantly greater than that in vertical openings. Model tests have shown, however, that this problem may be mitigated if a simple model of a staircase located in the centre of the room (being ventilated) is linked to the horizontal ventilation opening. Gravity currents in rooms occur in connection with so called displacement ventilation as cool gravity currents propagate along the floor that are driven by the density difference of the ventilation air and the ambient, warmer air within the room. As these gravity currents easily pass obstacles and to a certain extent are self-controlling, they can effectively distribute the cool air within rooms in a building. Likewise, warm gravity currents occur when warmer air introduced in a room rises and spreads along the ceiling plane. One application where warm gravity currents may be used to advantage is when converting buildings from electric heating to district hot water heating thus, avoiding the introduction of an expensive hydronic heating system. This report includes a full-scale laboratory study of the basic properties of thermally-driven warm air gravity currents in a residential building and examines the possibilities of using the resulting air movements for the distribution of ventilation air as well as heat. Results from laboratory tests show that this conversion method may prove effective if certain conditions on the layout of the building are fulfilled.
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| 9. |
- Blomqvist, Claes, et al.
(författare)
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Measurements and Control of Air Movements within a Building
- 1997
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Ingår i: 18th AIVC Conference: Ventilation and Cooling. - 0946075956 ; , s. 427-436
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There are a number of methods available concerning with distribution of air in buildings. Within control research, one can find new control algorithms which have not yet been used in practice. These new algorithms open the possibility of developing and implementing of new demand controlled ventilation systems. In a building the internal air motions are due both to differences in temperature and pressure differences caused by the ventilation system. Therefore, one fundamental question is to what extent it s possible to control the air motions within a building using fan powered ventilation in combination with temperature control. The aims of this paper is to report on measurements done to examine the influence of temperature differences between rooms on the air exchange through open doors in a building and to explore the use of modern control technique to minimise the temperature difference. The result of the measurements shows that even very small (0.1-0.2°C) temperature differences between rooms cause bi-directional air flows in the doorways of a magnitude that exceed the flow rates caused by the mechanical ventilation system. Therefore it is necessary to control the temperatures in the rooms to make it possible for the ventilation system to distribute the air to those parts of the building where it is needed.
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