1.2. Importancia de la investigación
2.1.6. Técnicas e instrumentos de recolección de
So far microclimatic (ecoclimatic) research concerned mostly general state of atmosphere of an underground system and rarely microclimate of refuges (Kłys et al., 2005; Kłys, Wołoszyn, 2005; Kłys, 2008), which are direct places of wintering of bats. Microclimate of refuges many times differs greatly from microclimatic “background” of the underground system.
One may use various measuring devices, but methodology of measurement should be precisely described.
So far it was impossible to introduce to measuring technology a device which would measure a sum of factors having influence on hibernation comfort of a bat.
Most of works concerning microclimatic conditions in a place of occurrence of bats lack the description of methodology of measurement and kind of devices used, which makes correct interpretation of such data impossible (Kłys et al., 2005). Usually influence of the measuring person on the result of measurement is not taken into account as well as time for stabilization of the device, which is often 30 minutes or even longer (Caputa, Kłys, 2005).
Apart from measurement of ecoclimate of a refuge the “background” of the underground system was also measured.
Physical factors which determine microclimate of underground systems are discussed below.
5.3. 1. Air temperature (T)
The measure of empirical temperature is usually a change in volume or pressure of a standard body which is in the state of thermodynamic balance with the body the temperature of which is measured. There are theoretical and empirical scales of temperatures. The first group includes e.g. scale of perfect gas, thermodynamic scale of temperatures. Empirical scales based on empirical data includes International Practical Temperature Scale.
Depending on the way of heat transfer between the sensor and the body the temperature of which is determined; devices are divided into contacting ones called
A frequent measuring device used so far in measuring temperature was Assman aspiration psychrometer. However, values obtained in this method bear major errors and these measurements also average the values (drawing in larger quantities of air). They give only a very general picture of microclimatic values and they are totally useless to measure refugioclimate.
In the literature there is a notion of dry-bulb temperature (Ts) - it is temperature
displayed by a normal (i.e. dry) thermometer and if there is no reference to the kind of temperature, it means that dry-bulb temperature is concerned. Wet-bulb temperature (Tw) is the temperature shown by a wet thermometer, e.g. in a psychrometer or covered
by ice.
It should be pointed out that in small underground systems and relatively stable microclimate, measurements performed with the use of traditional methods are hindered and bear grave errors, also due to presence of the researcher and people who accompany him or her, as well as time of their stay in the place where the measurement is performed (Fig. 4).
There is a number of publications concerning influence of tourism in caves on their microclimate, including temperature (Kwiatkowski, Piasecki, 1989; Piasecki, 1996, 1996a; Pflitsch et. al., 1999; Zelinka, 2002; Piasecki et. al., 2007).
Measurement of temperature and air flow in a refuge should be performed from the side the air comes in (Fig. 5).
For the purpose of this research a thermoanemometer and a gas parameter gauge made by SENSOTRON, specially modified and calibrated to the needs of recording, were used. Special attention was paid to graduate thermometers (devices) in relation to a bench-mark in various ranges of temperature before the measurements were performed. In the immediate place of hibernation of bats temperature was measured with the use of an extension arm (aluminium rod), in such a way, that the observer did not interfere with readings of the gauge, always against the stream of inflowing air.
Fig. 4. Influence of human presence on measurement of temperature (9 Mar 2002). Measured at the place bat hibernation. Vertical lines show the range of data omitted in analyses (Kłys 2003).
5.3. 2. Substrate temperature
(Tch - temperature of the surface of hibernation)
To measure temperature of a side wall of an excavation or surface of objects which are close to wintering bats, thermometers or non-contacting devices are used. Usually temperature is measured with thermoelectric or resistance thermometers, less often expansion thermometers are utilized. For the purpose of this work an electric contact thermometer made by SENSOTRON was used. In order to enlarge the surface of contact silicone of high thermal conductivity was utilized.
5.3. 3. Air flow velocity (v)
A very important element of ecoclimate which should be registered is measurement of air flow velocity, both the background of ecoclimate and directly in the place of hibernation.
This parameter should be approached very carefully. In case of the background of an underground system these measurements require determining average velocity in time and certain cross section or determining spot speed for refugioclimate.
In order to measure spot and average velocity in time anemometers, impact pressure tubes, flowmeters, hot-wire anemometers and katathermometers are used.
Air flow velocity in underground systems is usually given in m/s, m/min and sometimes cm/s (100 cm/s = 1 m/s = 60 m/min).
Sometimes these devices have scales in imperial system units in/s, ft/s, yd/s. (1m/s = 39.3701 in/s = 3.28082)
Specifying air flow in the hibernation place of a bat with the use of anemometers is difficult due to technical reasons. Above all it refers to measurements (recording) of movement of small velocity which occurs in niches. Measurements of air velocity lower than 0.1 ms-1 are difficult or impossible to perform with the use of regular anemometers.
Using mechanical anemometers of various types is not as effective as it was expected due to small inertia of receptors, necessity to overcome internal and external friction, as well as small space of a niche.
In the current work a specially modified and calibrated to the needs of recording SENSOTRON hot-wire anemometer was used.
In order to minimize influence of a human and a wintering bat measurements were performed from leeward side while standing face front to coming air (Fig. 5).
In narrow (low) corridors and chambers of small volume emission of heat (3 - 4 thousand kcal/24h) and breath of the observer may significantly influence results of observation (Kłys et al., 2005).
Fig. 5. Performing measurement of air flow and temperature. The arrow shows direction of air flow. An infrared photograph for the author by P. Rutkowski, Flir Systems.
In measurements in cross section of a corridor (“background”) air velocity is not same in all points of the section (Fig. 6). The highest velocities are usually in central parts of a corridor, while the lowest ones are at walls.
There are often observed streams of air flowing in and out which flow through the entire inside diameter of the opening in one direction or interchangeably, i.e. in the cross section of the corridor two opposite fluxes of air are moving.
several times (Pawiński et al., 1995) and an arithmetic mean should be calculated from these measurements.
Fig. 6. An exemplary distribution of air velocity in a corridor of an underground system. The place of hibernation of a bat is indicated. (The photograph and the drawing are made by the author).
5.3. 4. Relative humidity of air (Rh)
Atmospheric air in underground systems is considered to be a mixture of dry air and water vapour. One should remember, that when temperature of air saturated with vapour drops, part of vapour condenses and mist occurs. As temperature of air saturated with steam increases, state of insatiability occurs (it is shown in a Mollier diagram (Biernacki, 1993).
Air humidity (relative and absolute) is a value changeable in time and space. It depends on climate, season of the year, intensity of precipitation and direction of air flow (into or out of a cave). Differences in air humidity of a zone next to an entrance and deeper ones may be significant. Air humidity is an equally complex factor as air temperature. It is formed as a result of moisture incoming from the surface, cooling of air inside, becoming damper in contact with groundwater flows and infiltration water (Kwiatkowski, Piasecki, 1989).
To measure humidity the following methods are used: gravimetric, condensation (dew point), psychrometric, hygroscopic ones as well as hygrometer sensors.
To measure relative humidity of background of the underground system usually an Assman aspiration psychrometer was used of an accuracy up to 0,2 0C.
Despite very precise measurement of relative humidity the devices used so far (Assman aspiration psychrometer) are totally useless for measuring refugioclimate.
The author used an electronic gas parameter gauge made by SENSOTRON. It allowed to measure relative humidity in microniches. The measurement was performed while standing face front to coming air in order to minimize influence of the human and the wintering bat. The bats often use seeps of water from walls (Fig. 7); air humidity is then higher only in the immediate proximity of the wintering bat.
Fig. 7. In an environment where humidity is lower then the desired one, greater mouse- eared bats choose microniches of higher humidity of rock and air (photographed by the author).
5.3. 5. Thermal conduction of materials (λ)
Thermal conductivity, thermal conduction coefficient (marked with the symbol of λ) is one of the most important parameters of substance for heat conduction. In same conditions more heat will flow through a substance of higher thermal conduction coefficient.
Thermal conductivity is a quantity characteristic for a substance in a given state of aggregation and its phase. It depends on its chemical composition, structure, porosity, state of aggregation and temperature. The substances which best conduct heat are metals, while gases are the poorest conductors.
In the work there were no field measurements of conductivity, only a rough analysis of the substance on which bats wintered. Taking into consideration the type of the substrate approximate values of thermal conductivity were used (Table 3).
Table 3. Exemplary approximate values of thermal conductivity of materials
which one may encounter at bat hibernation (grey fields show average values of the factor). The unit of the thermal conduction coefficient in SI is J/(m s K) = W m-1 K-1
(watt per meter kelvin).
material Thermal conductivity in (W m-1 *K-1).
The average value is given
Air 0.025 Expanded polystyrene 0,03; 0,06; 0,1 Wood 0,04; 0,12; 0,21 Rubber 0,16 Water 0,5; 0,55; 0,6 Brick 0,6 - 0,15; 0,6; 0.69; 1.31 Concrete 0,8; 1,0; 1,28 Limestone 1,33 Soil 0,6; 2,3; 4 Sandstone 1,83; 2,4; 2,90 Marble 2,07; 2,5; 2,94 Granite 1,73; 2,8; 3,98 Cast iron 55; Iron 71,8; 80,2; 55.4; 34.6; 60,5
5.3. 6. Air pressure (p)
Air pressure depends on basic quantities, which must be taken into consideration in research on underground systems. Knowing the value of pressure is useful for estimation of velocity of flow, volume of flux and mass of air. During comparison of data of refugioclimate with humidity and temperature a program calculating Mollier diagram was used (Wykres i-x Molliera).
In underground systems depending on the way of measurement the following items are used: devices to measure absolute pressure: mercury barometers, aneroid barometers, barolux, micro-barolux; devices to measure pressure above or below atmospheric:
micromanometers, manometers, differential manometers. According to the principle of operation one may distinguish: liquid gauges, elastic pressure gauges and electric converters.
The author used an electronic gas parameter gauge made by SENSOTRON, which had a built-in barometer. In the current work values of pressure of refugioclimate were converted into values for 1000 hPa of absolute pressure (the program Wykres i-x Molliera). It facilitates comparison of data of relative humidity from different measuring points as well as days of measurement.
5.3. 7. Level of cooling (Ka)
While entering the state of hibernation a body of a bat may give up heat to the environment by radiation, vaporization, convection and conduction. The amount of heat which is given up in convection depends on thermal conductivity of the body of the bat and difference of temperatures of skin and air or rock that surrounds the body.
In certain combination of such factors as: temperature, air movement and humidity one may assume that the bat achieves comfort of hibernation. In order to determine optimal values for hibernation of bats dry-bulb temperature, relative humidity and air flow velocity was measured in the place of hibernation.
Thermal comfort is determined by measurement of intensity of cooling with the use of wet Hill’s katathermometer.
The quantity of cooling power of the atmosphere, which is intensity of cooling Ka°, is expressed by loss of heat from 1 cm2 of surface in 1 second (Frycz, 1974).
The unit of intensity of cooling is 1 Kata degree mcal/cm2 • s. Due to the commonly
binding SI the intensity of cooling effect of the atmosphere should be expressed in W/m2.
The unit of intensity of cooling is NKa° (new Kata degree) expressed in W/m-2. Due to
frequent use of the old unit in literature, a conversion formula has been given. NKa° = 42 x Ka° [W/m-2]
There are the following empirical relations between the cooling effect of the atmosphere given in Kata degrees and air velocity υ and its temperature T expressed in
0C (Budryk, 1961). υ ≤ 1ms-1
Where: w – air velocity, ms-1 Tw – wet-bulb temperature
Due to measuring difficulties (in our case low temperature, disturbances by human presence itself, heating up the katathermometer, repeating the measurement at least 5 times and above all else difficulty in placing it close to the hibernating bat) the above mentioned formula was used. So the following components were measured: air flow velocity and temperature in the proximity of a hibernating bat, but the wet-bulb Hill’s katathermometer was not used due to the above mentioned measuring errors.
Unfortunately, there is no direct formula which allows to calculate wet-bulb temperature Tm on the basis of dry-bulb temperature Ts and relative humidity Rh.
Due to the fact that dry-bulb temperature Ts and relative humidity Rh was measured, not wet-bulb temperature Tw which is necessary for the formula, Tw was calculated with the use of the computer program Wykres i-x Molliera the purpose of which is to simplify calculations connected with transformations of humid air.
The list of devices used during research as well as their parameters are included in Appendix no. 1.