The Effect of Photosynthesis on Heat Island Production (A Case Study of Orji, Imo State Nigeria)

Transcription

1 The Effect of Photosynthesis on Heat Island Production (A Case Study of Orji, Imo State Nigeria) Ngozi B. Ewurum 1 & Ikechukwu E. Nwosu 2 1 Ngozi B. Ewurum & 2 Ikechukwu E. Nwosu 1,2 Department of Physics, Imo State University Owerri, Nigeria Abstract: The appearance of uncomfortable night- time rise in temperature at residence of cities needs to be addressed. Using the method of heat transfer through radiation and convection, the experiment was conducted where vegetation were planted around the residential areas of Orji, Imo State. Temperature Measurements were taken using a hand - held infrared thermometer (IRT) and recorded. Results obtained showed that the ambient mean temperature of the processes of photosynthesis in the vegetative gardens were 24.9oC, 24.6oC and 24.8oC for three days respectively. This means that heat island problems can be mitigated through planting of trees and grass around out cities. Orji is located at latitude 5.514oN and longitude 7.044oE. Keywords: Heat Island, Photosynthesis, Mitigation, Radiation, Convection, Heat Transfer 1. INTRODUCTION Over the years, there has been an increase in rural dwellers drifting to the cities because of the use of modern technologies. Today this population has grown approximately to 2.2 billion, which constitutes close to 50% of the world s population (Akbari et al, 2012). In the United States of America, roughly 80% of the people reside in metropolitan areas (Heisler and Brazel, 2010). High rates of urbanization have resulted in dramatic demographic, economic, land use and climate change. The sun is a very hot body that emits large amount of photon, but emits most of this energies to exist in electromagnetic spectrum, and this radiant energy of the sun also determine the seasonal variation (Owate and Okujagu, 1997). Hot bodies emit radiant energy at longer wavelength (i.e infrared) section of the spectrum. On itself, the atmosphere is composed of four states of matter and it, radiates energy downwards. Also, it is always noticed that atmosphere stands to be cooler than the surface of the earth, because of convection of the air current which tries to displace each other. 59

2 The word urban is used to classify a community or city where building density is relatively low with significant low green space and a commercial district that is dense. Heat from the sun is incident on the surfaces around urban areas. Basically, during the summer days, it is 50 o F to 96 o F hotter than the ambient temperature around it (Berdhl, 1997 and Brentz, 1997). This differential heating gives rise to a highest temperature within urban cities which shows up as urban heat island. Notably, close isotherm around a city indicates surfaces of an area that appear warmer relatively to its local surroundings. The indication is that urban regions of warmer than rural surrounding a phenomenon described as heat island.local temperature is influenced by so many factors including man made factors like the anthropogenic heat. Heat is lost and can be gained by other factors; as a result, energy is conserved. This process does not depend on different types of surfaces, but on the spread of the local climate and different regional meteorology (Oke, 1987 and Sailor, 1995). This will result into heaving a local heat island (heat hot spot) that can always have a shift experiencing dual seasons (Unwin, 1980). A city is defined by its open spaces without trees and grasslands, with its human populations and activities. As a city is developing more and more, vegetation is lost making way for more and more buildings. This lost of vegetation results in less shade and moisture that keeps the urban surfaces cool. In contrast to this, the rural areas are covered with vegetation and lots of grassland which provides shade that help to lower its ambient temperature. The heat of evaporation of water is constant at 2.43KJ per gram; the cooling provided by a plant is proportional to its rate of water loss. These trees have roles to play in the cities. They help remove almost all the pollutant elements in the air, for example trees require carbon dioxide, to produce their own food through photosynthesis and in return release oxygen to the atmosphere which helps to cool the environment. They also remove pollutants by allowing deposition of pollutant on their leaves. If we are to cool the soil, it is important to cover the soil by shading it from direct heating of the sun, while enabling cooling there are some benefits of planting trees. Trees can help improve the quality of life. It will also raise the value of properties. It will reduce the rain run-off water thereby putting a check to flooding (McPherson et al, 1994). Cities are made up of impervious surface. The result of over population of growing cities is lost of vegetation. Akbari, 2002, provides an overview of benefits and cost associated with plating urban trees. Rural areas have more vegetation than the cities. Plants cool themselves by evapotranspiration thereby losing some water to the space. One might expect tree to provide more cooling than grass, since their leaves are held higher up above the ground and so should lose water faster. Trees have a pipe that draws up water to their leaves against gravity. Also considerable differences of cooling loads occur when trees are planted around a building. This will ultimately reduce the solar radiation that is allowed to enter a building from the environment. 1.1 Photosynthesis Photosynthesis is the process by which green plants, photosynthetic bacteria and algae convert the energy in sun light together with carbon dioxide and water from the air into chemical energy in the form of carbohydrate in their leaves, which is then used to build the sugars, starches and proteins that make up plant matter. For a leaf, metabolic heat loss is minimal, so temperature depends chiefly upon incident radiation, evaporative and convective heat losses, which will vary with wind speed and humidity. The temperature of the heat may be above or below air temperature, dependent upon the gains from radiation and the losses from latent heat, which closely links temperature to water use. The oxygen produced escapes to the atmosphere, while the ionized hydrogen continues the process, carrying the energy. It passes along a chemical chain, until finally the H + effectively reacts with carbon dioxide to form carbohydrate, from to; 2H 2 O + energy => O 2 + 4H + + 4e - 4H + + 2CO 2 => 2 (CH 2 O) 60

3 The rate at which photosynthesis occurs depends upon several physical factors including the irradiation level temperature, water supply, supply of other nutrients and rate of diffusion of CO 2 into the chloroplasts. 1.2 Wavelengths Used by Photosynthesis In green plants, photosynthesis makes use of light across the visible part of the spectrum to power the chemical reactions. Light is captured by the pigment, chlorophyll-a and carotenoids such as β-carotene in the chloroplast. These capture red and blue light, but not green, which is why leaves are green it is reflected. Certain photosynthetic bacteria contain other pigments in addition to chlorophyll, allowing them to make use of other wavelengths. The wavelengths at which light is absorbed determine the efficiency of photosynthesis. Photon excites chlorophyll molecule, which can then use the energy to produce a free electron used in splitting water and in producing carbohydrate. 2. MATERIALS AND METHODS The ambient temperature of the plant surrounding needs to be established. A hand held infrared thermometer (IRT) wrapped in a thermal glove was used to measure the temperature. This glove prevents temporary inaccurate temperature readings due to thermal shock from moving the instrument quickly, from the indoor to outdoor ambient temperatures. Measurement were recorded, this experiment was carried out for several days so that the mean ambient temperature will be recorded and analyzed. 3. DATA PRESENTATION The result obtained after the measurements are tabulated in table 1 while the chats from the table is highlighted in figure 1. Figure 1 actually comprises three chats of time against temperature superimposed in one. Table 1. Three -Day Mean Temperature Records Time (hourly) Mean Temperature Reading ( o C) Day Day 1 Day 2 Day am am am noon pm pm pm pm pm pm

4 Figure 1. 3-Day Mean Temperature Chats 4. DISCUSSION The ambient temperature readings show that photosynthesis taking place in a vegetative farm land produced temperature variation. In the morning about 9.00am, the mean temperature readings were 24.9 o C the first day, 24.6 o C, the second day and 24.8 o C the third day. In the afternoon about 2.00pm the mean temperature was 32.4 o C for the first day, 31.3 o C the second day and 31.6 o C the third day. The mean ambient average temperature of the surrounding is 27 o C around 9.00am for the three days while the ambient average temperature of the vegetative garden is 24.8 o C.This means that mean temperature of the vegetative garden is lower than the ambient mean temperature of the surrounding; thus temperature reduction using vegetation is the most widely applied mitigation measure which could achieve huge energy savings. (Kikegawa et al, 2006). 5. CONCLUSION This study shows that photosynthesis contribute, greatly is the reduction of heat island phenomena. The more vegetative farm lands that are close to residential areas the more the ambient temperature of such surrounding are reduced to a comfortable level. The process of photosynthesis takes up the carbon dioxide in the air and releases oxygen to the environment which cools the overall temperature of the same environment then the effect of heat island on our environment will be holistically reduced. 6. REFERENCES 1. Akbari, H., Mathews, H.D., and Seto, D. (2012). The Long Term Effect of Increasing the Albedo of Urban Areas. Environmental Research Letters, 7(2) Berdahl, P. & Bretz, S. (1997). Preliminary Survey of the Solar Reflectance of Cool Roofing Materials. Energy and Buildings 25: Heisler A.M. & Brazel, A.J. (2010). The Urban Physical Environment: Temperature and Urban Heat Islands. Urban Ecosystem Ecology (Inbanecosysteme), Kikegawa, Y., Genchi, Y., Kondo, H., & Hanaki, K. (2006). Impact of City-block-scale Counter Measures against Urban Heat Island Phenomena upon a Buildings Energy Consumption for Anti-conditioner Applied Energy, 83(6):

5 5. Mcpherson, E.G., Nowak, D.J., & Rownstree, R.A. (1994) Chicago s Urban Forest Ecosystem; Results of the Chicago Urban Forest Climate Project. Forest Service, U.S. Dept of Agriculture NE Oke, T.R. (1987). Towards better Scientific Communication in Urban Climate. Theoretical and Applied Climatology, 84: Owate, I.O. & Okujagu, C.U. (1997). Introduction to Energy and Industrial Environment. Rescue Publications, Samonda, Ibadan, Oyo State Nigeria, pg Sailor, D.J. (1995). Simulate Urban Climate Response to Modifications in Surface Albedo and Vegetative Cover. J. appl met 34, Unwin, D.J. (1990). The Synoptic Climatology of Birmingham s Urban Heat Island. Weather, 35(2), Copyright 2018 International Journal of Scientific Researcher Group 63