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Spatial–temporal variations in carbon dioxide levels in Ibadan, Nigeria a
b
Godson R. Ana , Peju Ojelabi & Derek G. Shendell
cde
a
Environmental Health Sciences, University of Ibadan, Ibadan, Ibadan, Nigeria b
Faculty of Public Health, Department of Environmental Health Sciences, University of Ibadan, Ibadan, Nigeria c
Department of Environmental and Occupational Health, Rutgers School of Public Health, Piscataway, NJ, USA
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d
School of Public Health, Rutgers Biomedical and Health Sciences, Center for School and Community-Based Research and Education, New Brunswick, NJ, USA e
Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ, USA Published online: 30 Jul 2014.
To cite this article: Godson R. Ana, Peju Ojelabi & Derek G. Shendell (2015) Spatial–temporal variations in carbon dioxide levels in Ibadan, Nigeria, International Journal of Environmental Health Research, 25:3, 229-240, DOI: 10.1080/09603123.2014.938024 To link to this article: http://dx.doi.org/10.1080/09603123.2014.938024
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International Journal of Environmental Health Research, 2015 Vol. 25, No. 3, 229–240, http://dx.doi.org/10.1080/09603123.2014.938024
Spatial–temporal variations in carbon dioxide levels in Ibadan, Nigeria
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Godson R. Anaa, Peju Ojelabib and Derek G. Shendellc,d,e* a Environmental Health Sciences, University of Ibadan, Ibadan, Ibadan, Nigeria; bFaculty of Public Health, Department of Environmental Health Sciences, University of Ibadan, Ibadan, Nigeria; cDepartment of Environmental and Occupational Health, Rutgers School of Public Health, Piscataway, NJ, USA; dSchool of Public Health, Rutgers Biomedical and Health Sciences, Center for School and Community-Based Research and Education, New Brunswick, NJ, USA; e Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ, USA
(Received 13 August 2013; final version received 12 April 2014) Growing evidence suggests how global background levels of atmospheric carbon dioxide (CO2) are increasing and this impacts environmental quality and human and ecological health. Data from less developed countries are sparse. We determined spatial and temporal variations in concentrations of CO2 in selected locations in Ibadan, Nigeria with identifiable prominent outdoor sources. Activity driven areas in north and south-west areas were identified and marked with a global positioning system. Waste management practices and activities generating CO2 were documented and described using a technician observation checklist. CO2 levels were measured using a portable TELAIRE 7001 attached to HOBO U12 data loggers across seasons. Mean CO2 levels were compared over seasons, i.e. rainy season months and the dry season months. While CO2 levels recorded outdoors in study areas were comparable to available international data, routine monitoring is recommended to further characterize concurrent pollutants in fossil fuel combustion emissions with known deleterious health effects. Keywords: carbon dioxide; urban environment; human activities; Ibadan; Nigeria
Introduction Carbon overload in the atmosphere is caused mainly when fossil fuels like coal, oil, and gas are used or forests are cut down and burnt. There are many heat-trapping gases, including methane and water vapor, but carbon dioxide (CO2) presents the greatest risk of irreversible changes if it continues to accumulate unabated in the atmosphere (Minnisale 2004). CO2 has caused most of the climate change we experience and its influence is expected to continue; CO2, more than any other climate driver, has contributed the most to climate change between 1750 and 2005 (Petit 1999; Obersteiner et al. 2001; Karl & Trenberth 2003; Azar et al. 2006). CO2 is emitted by natural and human-induced activities, both outdoors and indoors, and by people indoors (respiration) at rest and during activity. One of the most important human impacts on our environment is the relatively rapid increase in atmospheric CO2 caused by the widespread use of fossil fuels. Currently, the rise in CO2 is more rapid than at any time in the past, due to the increase in industrial activities. *Corresponding author. Email: [email protected] © 2014 Taylor & Francis
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CO2 levels have increased substantially since the industrial revolution, and are expected to continue doing so (Solomon et al. 2007). It is reasonable to believe human activities have been responsible for much of this increase, due to an increased dependence on machines and equipment burning fossil fuels, such as automobiles and generators, as well as enhanced chemical processes carried out in factories and power plants. CO2 emissions also arise from refuse dumpsites, market areas, abattoirs (slaughterhouses), and agricultural fields due to the traffic, combustion, and human activities concentrated in these areas. In some cases, there is interplay of traffic, market areas, refuse dump sites, and abattoir emissions, causing a rise in the CO2 level in these environments. In Nigeria and many other less developed countries, particularly in west Africa and Asia, large population concentrations and the rapid growth of urban centers pose serious problems in the provision and management of services, which can impact the entire living environment (USEPA 2005, 2006). The various opportunities offered by rapid urbanization are accompanied by problems of congestion, environmental degradation, and other environmental risks. Ibadan is an older but important city due to the university and its medical school and hospital, and it is one of the rapidly growing cities in Nigeria; in 2009, Ibadan had a population of 307,840 (Ogwueleka 2009). CO2 has become an important topic due to the interest in climate change. Combustion of fuels in the power, transport, and household sectors produces CO2 and a wide range of short-lived air pollutants with global warming and cooling effects. They account, directly or indirectly, for a substantial proportion of climate change and for the bulk of the direct damage to human health from global energy use. These pollutants include particle aerosols (sulfate, organic, and black carbon), carbon monoxide, nonmethane volatile organic compounds, and the gases responsible for ozone. Whether warming or cooling, all short-lived greenhouse pollutants can affect human health, increasing the risk of respiratory and cardiovascular diseases or lung cancer, and significantly reducing life expectancy. In less developed countries (LDCs) where there are little or no environmental emission standards, emissions from fossil fuels resulting from industrial, transportation, agricultural, and commercial activities can occur without proper environmental monitoring. In some cases where these standards exist, there are little or no enforcement actions by concerned agencies. Moreover, more can be done to improve knowledge of the health and environmental impact of CO2 emissions and other greenhouse gases in most LDCs, including Nigeria (Houghton 2007; Marland et al. 2007). LDCs had been predicted to suffer more from the effects of climate change due to the fact that they have minimal resources to build adequate response in order to adapt to the environmental health outcomes of climate change. In Nigeria, much is being said, especially by the media, about climate change but research to document the increase of CO2 in urban areas is lacking. This forms the basis of this initial study in Ibadan, Nigeria, whose objectives were to: (1) Describe the selected activity-driven locations where CO2 is produced. (2) Determine the meteorological condition of the locations. (3) Determine the spatial and temporal variations in the concentration of CO2 in selected locations within Ibadan.
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Materials and methods
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Study area The sites for CO2 sampling were selected purposively. The selected sites are within Ibadan North Local Government Area and Ibadan South-West Local Government Area. Six different points were chosen randomly for sampling in each of the selected sites. The sampling sites were chosen based on the increased potentials of CO2 emissions from CO2 driven activities in the following areas: Market Areas: MA (Bodija market or MA1, Aleshinloye market or MA2); Abattoir Area: AA (Bodija Abattoir or AA1, Aleshinloye Abattoir or AA2); Dumpsite Area: DA (Bodija dumpsite or DA1, Aleshinloye dumpsite or DA2); Farmland Area: FA (Awo (UI) farmland or FA1, Aleshinloye farmland or FA2); Traffic Area: TA (Ojoo Park or TA1, Mokola round about park or TA2, Agbowo complex area or TA3); and Industrial Area: IA (Challenge Park as IA1, Oluyole industrial area as IA2). Please refer to the map (Figure 1). Onsite observation An observational checklist was used to record the observable sources of CO2 emissions and environmental conditions in the selected sites. Meteorological information The Nigerian Meteorological Agency, Samonda, Ibadan was approached for the monthly/year weather conditions for Ibadan metropolis during the sampling period. Parameters obtained included outdoor air temperature, relative humidity (RH), rainfall, and wind speed. CO2 monitoring The CO2 gas meter used to measure CO2 levels at the different locations was a factory calibrated (with zero air/nitrogen gas) Telaire 7001 connected to a HOBO U12 outdoor/ indoor data logger (Onset Corp, Bourne, MA); air temperature and RH were also collected by the HOBO. Each data point represented an average of one second measures over a preset duration (every 5–10 s). The height of the measurement was about 1 m above the ground. The distance from the source was about 100–200 m. Measurements were conducted on three weekdays for four consecutive weeks during the rainy season and on three weekdays for four consecutive weeks during the dry season of 2009–2010. Arithmetic means and standard deviations were computed by aggregating data, by season, by location (2–3 sites per area) in six target areas. Data management and statistical analysis Data were analyzed using descriptive statistics and inferential statistics such as the student t-test to compare means of CO2, ANOVA to assess variations across study locations and the wet versus dry seasons, correlation coefficients (e.g. ambient air temperature and CO2), and spatial and trend analysis using SPSS at level of statistical significance p = 0.05.
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Figure 1. locations.
(Color online) Map of Ibadan, Nigeria showing the carbon dioxide (CO2) sample
Results Environmental management practices in sample locations Table 1 shows the degree of waste management practices across study locations. Fairly adequate waste management practices were observed at Aleshinloye dumpsite (DA2) compared to poor management practices at Bodija dumpsite (DA1). Similarly, fairly
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Table 1. Onsite trained technician observations on waste management practices and presence of greenhouse gas emission sources, Ibadan, Nigeria, Nov. 2009–Sept. 2010.
Locations
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Adequate Dumpsite area DA1 DA2 Market area MA1 MA2 Abattoir area AA1 AA2 Traffic area TA1 TA2 TA3 Farm area FA1 FA2 Industrial area IA1 IA2
Presence of emission sources
Waste management practices Fairly adequate
Inadequate
High
Medium
+
++ ++
+
++ ++
++ ++ +
Low
+++
++
++
++
+++
++
+++
+++
++
+++ +++
+ + ++ ++
+++ ++
Notes: DA1: Bodija dumpsite; DA2: Alesinloye dumpsite; MA1: Bodija market; MA2: Alesinloye market; AA1: Bodija Abattoir; AA2: Alesinloye Abattoir; TA1: Ojoo park; TA2: Agbowo park; TA3: Mokola park; FA1: Awo Farm, FA2: Alesh farm; IA1: Challenge Industrial area; IA2: Oluyole Industrial area. +++ : Adequate or highly present; ++ : Fairly adequate or medium; + : Inadequate or low.
adequate waste management practices were observed at Aleshinloye market and abattoir (MA1 and AA1) while inadequate management practices were noticed at Bodija market and abattoir (MA2 and AA2). Waste management practices at Ojoo and Mokola parks (TA1 and TA2, respectively) were found to be fairly adequate compared to adequate at Agbowo park (TA3). Waste management practices at Challenge and Oluyole industrial areas (IA1 and IA2, respectively) were found to be fairly adequate. CO2 generating sources/activities in study locations Table 2 shows CO2 generation sources/activities at the study locations. Open burning of refuse was the only CO2 generation activity observed at Bodija dumpsite (DA1), while this and automobile sources were found at Aleshinloye dumpsite (DA2). Automobile, generator and bush burning sources of CO2 emissions were found at Bodija and Aleshinloye markets (MA2 and MA1, respectively). Open burning of refuse was observed at the Bodija and Aleshinloye abattoir (AA2 and AA1, respectively) as the only CO2 generation source. Automobile sources was the only CO2 emission source found at Ojoo park (TA1) while automobile and power generator sources were observed at Mokola and Agbowo parks (TA2 and TA3, respectively). Automobile and industrial sources were observed at Challenge industrial area (IA1), while the Oluyole industrial area (IA2) also had these and power generator and bush burning sources. Other observable CO2 generating sources found at Bodija market (MA2) and at Oluyole Industrial area (IA2) included explosives and emissions from burning firewood from nearby canteens.
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Table 2. Specific identified greenhouse gas emission sources at the sampling sites, Ibadan, Nigeria, Nov. 2009–Sept. 2010. Typical emission sources
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Locations Automobile
Generator use
Open burning
Industry
Others
– +
– –
+ +
– –
– –
+ +
+ +
– –
– –
+ –
– –
– –
+ +
– –
– –
+ + +
– + +
– – –
– – –
– – –
– –
– –
– –
– –
– –
+ +
– +
– –
+ +
– +
Dumpsite area DA1 DA2 Market area MA1 MA2 Abattoir area AA1 AA2 Traffic area TA1 TA2 TA3 Farm area FA1 FA2 Industrial area IA1 IA2
Notes: DA1: Bodija dumpsite; DA2: Alesinloye dumpsite; MA1: Bodija market; MA2: Alesinloye market; AA1: Bodija Abattoir; AA2: Alesinloye Abattoir; TA1: Ojoo park; TA2: Agbowo park; TA3: Mokola park; FA1: Awo Farm, FA2: Alesh Farm; IA1: Challenge Industrial area; IA2: Oluyole Industrial area. + (Present) and – (Absent); others include bush burning and explosives, emissions from firewood from nearby canteens.
Meteorological information for study area within period of investigation Table 3 shows the meteorological information between November 2009 and September 2010 as obtained from the Nigeria Meteorological agency of Ibadan. The highest RH was in April 2010 (87 %) while the lowest was in November 2009 (71 %). The highest atmospheric pressure was in November 2009 (989.6 hPa) while the lowest atmospheric pressure was in March 2010 (985.3 hPa). Figure 2 shows the minimum and maximum Table 3.
Meteorological data for Ibadan, Nigeria, November 2009–September 2010. Parameters (monthly average values are reported below)
Months (2009–2010) November December January February March April May June July August September
Relative humidity (%)
Pressure (hpa)
Average air temperature (°C)
71 78 78 76 76 78 83 83 86 87 86
989.6 986.7 986.6 985.9 986.3 985.9 986.6 988.6 988.8 988.8 988.1
27.8 29.2 29.1 30.5 30.1 29.5 28.0 27.5 25.9 25.7 25.9
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Figure 2. Maximum and minimum outdoor air temperatures, Ibadan, Nigeria, November 2009–September 2010.
temperatures between November 2009 and September 2010. Temperatures were highest in the month of February, with a maximum value of 36.1 °C and a minimum of 24.9 °C. The lowest temperatures were observed in April, with a maximum value of 28.8 °C and a minimum of 25.5 °C. In addition, a gradual rise in average rainfall was found between December 2009–January 2010 (main months of dry season) and May 2010, followed by a sharp fall in June 2010, then a steady rise in rainfall again from July to August–September 2010 (data not presented). These data collectively documented the annual presence of wet/rainy and dry seasons in Ibadan, Nigeria. Spatial variations in CO2 levels Figure 3 shows the arithmetic mean (average) CO2 levels across the sampling locations. The highest measured CO2 concentrations were found at Mokola round about (TA3),
Figure 3. Mean carbon dioxide (CO2) levels across study sampling locations, Ibadan, Nigeria, November 2009–September 2010. Notes: The lines show the minimum and maximum measures at each sampling location. DA1: Bodija dumpsite; DA2: Alesinloye dumpsite; MA1: Bodija market; MA2: Alesinloye market; AA1: Bodija Abattoir; AA2: Alesinloye Abattoir; TA1: Ojoo park; TA2: Agbowo park; TA3: Mokola park; FA1: Awo Farm; FA2: Alesh Farm; IA1: Challenge Industrial area; IA2: Oluyole Industrial area.
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with an arithmetic mean value of 383 ppm, followed by Ojoo park (TA1) with an arithmetic mean value of 376 ppm. The lowest CO2 concentrations were observed at Alesh farm (FA2), with an arithmetic mean value of 329 ppm. Temporal variations in CO2 levels Table 4 extends beyond Figure 3 and shows the average CO2 concentration in the dry and rainy seasons across the sampling locations. The average CO2 concentrations were lower during the dry season and higher during the rainy season. These differences were most likely due to the presence and strength of identified sources across study locations (see further discussion below) and atmospheric conditions (air flow/wind, pressure, and RH (see Table 3)). During the rainy season, the highest average CO2 level (±standard deviation), 390 ± 64 ppm, was recorded at the traffic area. This was followed by the market area, 375 ± 61 ppm, and abattoir, 357 ± 60 ppm. This was closely followed by the dumpsite area, 354 ± 56 ppm. The farmland area had the lowest CO2 level of 345 ± 55 ppm. In the dry season, market area recorded the highest average CO2 level (±standard deviation), 335 ± 45 ppm, followed by the abattoir, 335 ± 59 ppm, by traffic areas, 333 ± 56 ppm, and by the farmland area, 330 ± 44 ppm. The dumpsite area recorded the lowest CO2 level of 323 ± 50 ppm. Discussion The arithmetic mean (average) CO2 level across the sampling areas in the rainy season varied (see Table 4). The highest values were obtained in the traffic area (390 ± 64 ppm) while the lowest values were obtained at the farmland area (345 ± 55 ppm). The CO2 recorded at the traffic area sites could be attributable to the type of activities observed
Table 4.
Summary statistics for CO2 across seasons at the various sample locations. Rainy season
Dry season
Sample location
Mean
SD
Max
Min
Mean
SD
Max
Min
DA1 DA2 MA1 MA2 AA1 AA2 TA1 TA2 TA3 FA1 FA2 IA1 IA2
360.9 347.1 381.1 369.0 369.6 343.9 390.5 361.9 416.9 352.4 337.2 408.4 373.2
66.1 40.5 70.1 50.8 70.3 43.4 67.5 65.5 62.9 61.4 46.4 55.8 62.8
530 456 575 532 544 477 546 555 603 492 464 567 484
280 290 288 283 210 284 277 250 306 267 271 296 276
313.9 332.6 330.6 340.1 335.8 333.2 361.4 317.7 348.6 338.2 319.2 336.1 299.9
53.2 45.0 51.0 38.1 70.9 45.1 52.4 54.5 47.1 45.7 41.3 82.2 67.8
467 419 513 414 605 472 521 454 483 431 396 563 475
219 229 245 251 237 228 265 208 259 258 225 194 193
Notes: DA1: Bodija dumpsite; DA2: Alesinloye dumpsite; MA1: Bodija market; MA2: Alesinloye market; AA1: Bodija Abattoir; AA2: Alesinloye Abattoir; TA1: Ojoo park; TA2: Agbowo park; TA3: Mokola park; FA1: Awo Farm, FA2: Alesh Farm; IA1: Challenge Industrial area; IA2: Oluyole Industrial area.
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during the times of measurement as the observable checklist indicated consistently high traffic-associated CO2 sources in the parks and garages where sampling was done. Vehicular emissions from traffic and motor bikes on the roads were the major sources of CO2 emissions. This is not unexpected as combustion of automobile engines is known to contribute greatly to CO2 deposits in the atmosphere. Another online reference (www.123HelpMe.com 2012) has recently reported cars release approximately 30 % of the CO2 in the earth’s air. Vehicles, including cars, degrade the environment by releasing emissions from the combustion systems of these automobiles. Every time an automobile burns a gallon of gasoline it releases about 10 kilograms (about 20 lb) of CO2 (USEIA 2013). Recent research also noted increased CO2 emissions from mobile line sources in suburban/ urban areas surrounded by rural agriculture (Shendell et al. 2012). Ndoke et al. (2013) reported that areas with relatively heavy congestion have higher concentrations of CO2, while areas with minimal traffic have lower concentrations of CO2. For example, Sabo in Kaduna had the highest average concentration of 1840 ppm, while Asokoro (behind ECOWAS) in Abuja had the lowest average concentration of 1160 ppm (Ndoke et al. 2013). It should be noted that these were shorter term averages than in the present study (three weekdays in each of four weeks in each of two seasons during November 2009 and September 2010). The minimum CO2 value recorded at the farmland area during the rainy season could be due to the fact that green plants use CO2 during photosynthesis. Although, the environmental conditions of the farmland area were good at the time of measurement and there was a low observable source of CO2 emissions, the effect of CO2 being transported to the farmland area cannot be ruled out. Also, the farmland area was not expected to record a high CO2 concentration, even though according to Rees (2009), soil is the third largest carbon sink in the world. The concentrations were likely low because the sample sites used were not recently tilled, which would make the soil reservoir carbon available in the atmosphere. Higher CO2 enables plants to grow faster and larger and to live in drier climates. During the dry season, there was no significant difference between the mean CO2 levels obtained in all the sampling areas. The maximum CO2 level was recorded at the market area (335 ± 45 ppm), closely followed by the value obtained in the abattoir area (335 ± 60 ppm). The lowest value was obtained at the dumpsite area (323 ± 50 ppm). The maximum CO2 recorded at the Market area in the dry season can be attributed to vehicular emissions from traffic moving in and out of the market, car parks, commercial activities from stores, and the inflow of polluted air from nearby activity driven areas. However, Ndoke et al. (2003) recorded a considerably higher CO2 concentration in three major Nigerian markets with 1380 ppm in Wuse market, Abuja, 1630 ppm in Kasuwa market, Kaduna, and Sabo market in Kaduna recorded the highest CO2 level with 1840 ppm. Again, however, these were shorter term averages than in the present study (three weekdays in each of four weeks in each of two seasons during November 2009 and September 2010). The result of this study is further enhanced by the work of Pretty and Hine (2001) that found a major source of greenhouse gas emissions related to enteric fermentation and manure deposition and management in meat production and supply chains. Steffen and Bedker (1962) posited that meat processing and abattoir operations produce highly organic, highly nitrogenous, biologically degradable waste water with relatively high concentrations of suspended and dissolved solids and grease. The CO2 concentration is also expected to have come from the burning activities going on in the abattoir.
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The dumpsite recorded the lowest CO2 concentration, mainly because anaerobic respiration is prominent with only the upper surface area decomposing with the aid of atmospheric oxygen. The concentration of CO2 in the air changes with location and the seasons of the year (Gratani & Varone 2005). The mean CO2 levels varied substantially across the seasons (rainy and dry seasons) in the present study as well. The arithmetic mean CO2 levels varied significantly across the seasons (rainy and dry seasons). The higher arithmetic mean CO2 was recorded during the rainy season, 370 ± 63 ppm, while the average CO2 in the dry season was 332 ± 57 ppm. This result represents sampled locations (2–3 sites in six areas) within the two government administrative areas of Ibadan, Nigeria, and, therefore, perhaps different from the expected result given the ambient and built environment attributes of the individual locations. For instance, Ophardt (2003) found cyclic changes in CO2 concentrations occur due to seasonal variation of vegetation growth on farmland. Starting in May, the growth of plants and trees uses CO2, so the concentration decreases a little bit. Starting in October and November, the growth ceases, thus, causing the CO2 to increase. This trend was further corroborated by Brebner (2010). However, the seasonal CO2 concentration for the farmland in this experiment does not confirm the findings of Ophardt (2003). An average of 345 ± 55 ppm was recorded in the rainy season with a reduction to 323 ± 50 ppm in the dry season. It can be assumed the effect of other carbon sources could have contributed to the amount of CO2 in the atmosphere across seasons. Another impact follows the effects of climate change – due to higher air and surface temperatures – and the increased CO2 levels in the atmosphere. Andrews and Forster (2010) reported climate models indicated precipitation around the world will increase by roughly 2–3 % per degree Celsius of global surface temperature change. Trusilova and Churkina (2008) and Leggett (2011) corroborated this by stating the latest research suggested precipitation can also respond directly to the atmospheric heating caused by increases in CO2. This direct reaction occurs much faster than the precipitation modifications caused by global climate change because global climate change is relatively slow; it depends on how quickly the oceans warm – something that can take decades to centuries (Beamish 2004). This could apply to the situations in this report as the measured outdoor CO2 levels are within internationally acceptable range, i.e. comparable to other available data, but the impact of its effect or interplay of effects encompassing the abundance of CO2 in the atmosphere is already being felt in the amount of rainfall and direct effect of observable change in temperature. Conclusion This study assessed the carbon dioxide (CO2) levels of 13 selected activity driven locations (2–3 locations or sites per targeted area) in two local government areas of Ibadan, Nigeria, stratified into six targeted areas: Market area, Dumpsite area, Abattoir area, Farmland area, Traffic area, and Industrial area. Our study suggested emissions from tailpipes of vehicles primarily contributed to the measured CO2 in the two local government areas of Ibadan, Nigeria where the study was carried out, given the lack of other large point sources. Thus, vehicular emissions, if not controlled, can have detrimental effects on the long-term climate of Ibadan, Nigeria, and throughout the region, and indirectly lead to chronic diseases and environmental impacts being increasingly associated with climate change.
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Acknowledgements The authors are grateful to all the research assistants for their support throughout the course of the study and to the Department of Environmental Health Sciences for their technical support. This project was completed during the MPH program of O. Ojelabi. The authors also thank S.W. Kelly for internal manuscript review. This work was supported by the Georgia State University International Strategic Initiative and the Atlantic Philanthropies-Bermuda/U.K. office, 2006–2008.
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Steffen AJ, Bedker M. 1962. Operation of full scale anaerobic contact treatment plant for meat packing wastes. Proceedings of the 16th Purdue Industrial Waste Conference. 109:423. Trusilova K, Churkina G. 2008. The response of the terrestrial biosphere to urbanization: land cover conversion, climate, and urban pollution. Biogeosciences Discuss. 5:2445–2470. United States Energy Information Administration (USEIA). 2013. How much carbon dioxide is produced by burning gasoline and diesel fuel? [cited 2013 June 12]. Available from: http:// www.eia.gov/tools/faqs/faq.cfm?id=307&t=11. United States Environmental Protection Agency. 2005. Average Annual Emissions and Fuel Consumption for Gasoline-Fueled Passenger Cars and Light Trucks. [cited 2013 May 9]. Available from: http://www.epa.gov/otaq/consumer/420f08024.pdf. United States Environmental Protection Agency. 2006. Agriculture. In: Inventory of US greenhouse gas emissions and sinks: 1990–2004. Washington (DC): U.S. Environmental Protection Agency; p. 1.
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Spatial–temporal variations in carbon dioxide levels in Ibadan, Nigeria a
b
Godson R. Ana , Peju Ojelabi & Derek G. Shendell
cde
a
Environmental Health Sciences, University of Ibadan, Ibadan, Ibadan, Nigeria b
Faculty of Public Health, Department of Environmental Health Sciences, University of Ibadan, Ibadan, Nigeria c
Department of Environmental and Occupational Health, Rutgers School of Public Health, Piscataway, NJ, USA
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d
School of Public Health, Rutgers Biomedical and Health Sciences, Center for School and Community-Based Research and Education, New Brunswick, NJ, USA e
Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ, USA Published online: 30 Jul 2014.
To cite this article: Godson R. Ana, Peju Ojelabi & Derek G. Shendell (2015) Spatial–temporal variations in carbon dioxide levels in Ibadan, Nigeria, International Journal of Environmental Health Research, 25:3, 229-240, DOI: 10.1080/09603123.2014.938024 To link to this article: http://dx.doi.org/10.1080/09603123.2014.938024
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International Journal of Environmental Health Research, 2015 Vol. 25, No. 3, 229–240, http://dx.doi.org/10.1080/09603123.2014.938024
Spatial–temporal variations in carbon dioxide levels in Ibadan, Nigeria
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Godson R. Anaa, Peju Ojelabib and Derek G. Shendellc,d,e* a Environmental Health Sciences, University of Ibadan, Ibadan, Ibadan, Nigeria; bFaculty of Public Health, Department of Environmental Health Sciences, University of Ibadan, Ibadan, Nigeria; cDepartment of Environmental and Occupational Health, Rutgers School of Public Health, Piscataway, NJ, USA; dSchool of Public Health, Rutgers Biomedical and Health Sciences, Center for School and Community-Based Research and Education, New Brunswick, NJ, USA; e Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ, USA
(Received 13 August 2013; final version received 12 April 2014) Growing evidence suggests how global background levels of atmospheric carbon dioxide (CO2) are increasing and this impacts environmental quality and human and ecological health. Data from less developed countries are sparse. We determined spatial and temporal variations in concentrations of CO2 in selected locations in Ibadan, Nigeria with identifiable prominent outdoor sources. Activity driven areas in north and south-west areas were identified and marked with a global positioning system. Waste management practices and activities generating CO2 were documented and described using a technician observation checklist. CO2 levels were measured using a portable TELAIRE 7001 attached to HOBO U12 data loggers across seasons. Mean CO2 levels were compared over seasons, i.e. rainy season months and the dry season months. While CO2 levels recorded outdoors in study areas were comparable to available international data, routine monitoring is recommended to further characterize concurrent pollutants in fossil fuel combustion emissions with known deleterious health effects. Keywords: carbon dioxide; urban environment; human activities; Ibadan; Nigeria
Introduction Carbon overload in the atmosphere is caused mainly when fossil fuels like coal, oil, and gas are used or forests are cut down and burnt. There are many heat-trapping gases, including methane and water vapor, but carbon dioxide (CO2) presents the greatest risk of irreversible changes if it continues to accumulate unabated in the atmosphere (Minnisale 2004). CO2 has caused most of the climate change we experience and its influence is expected to continue; CO2, more than any other climate driver, has contributed the most to climate change between 1750 and 2005 (Petit 1999; Obersteiner et al. 2001; Karl & Trenberth 2003; Azar et al. 2006). CO2 is emitted by natural and human-induced activities, both outdoors and indoors, and by people indoors (respiration) at rest and during activity. One of the most important human impacts on our environment is the relatively rapid increase in atmospheric CO2 caused by the widespread use of fossil fuels. Currently, the rise in CO2 is more rapid than at any time in the past, due to the increase in industrial activities. *Corresponding author. Email: [email protected] © 2014 Taylor & Francis
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CO2 levels have increased substantially since the industrial revolution, and are expected to continue doing so (Solomon et al. 2007). It is reasonable to believe human activities have been responsible for much of this increase, due to an increased dependence on machines and equipment burning fossil fuels, such as automobiles and generators, as well as enhanced chemical processes carried out in factories and power plants. CO2 emissions also arise from refuse dumpsites, market areas, abattoirs (slaughterhouses), and agricultural fields due to the traffic, combustion, and human activities concentrated in these areas. In some cases, there is interplay of traffic, market areas, refuse dump sites, and abattoir emissions, causing a rise in the CO2 level in these environments. In Nigeria and many other less developed countries, particularly in west Africa and Asia, large population concentrations and the rapid growth of urban centers pose serious problems in the provision and management of services, which can impact the entire living environment (USEPA 2005, 2006). The various opportunities offered by rapid urbanization are accompanied by problems of congestion, environmental degradation, and other environmental risks. Ibadan is an older but important city due to the university and its medical school and hospital, and it is one of the rapidly growing cities in Nigeria; in 2009, Ibadan had a population of 307,840 (Ogwueleka 2009). CO2 has become an important topic due to the interest in climate change. Combustion of fuels in the power, transport, and household sectors produces CO2 and a wide range of short-lived air pollutants with global warming and cooling effects. They account, directly or indirectly, for a substantial proportion of climate change and for the bulk of the direct damage to human health from global energy use. These pollutants include particle aerosols (sulfate, organic, and black carbon), carbon monoxide, nonmethane volatile organic compounds, and the gases responsible for ozone. Whether warming or cooling, all short-lived greenhouse pollutants can affect human health, increasing the risk of respiratory and cardiovascular diseases or lung cancer, and significantly reducing life expectancy. In less developed countries (LDCs) where there are little or no environmental emission standards, emissions from fossil fuels resulting from industrial, transportation, agricultural, and commercial activities can occur without proper environmental monitoring. In some cases where these standards exist, there are little or no enforcement actions by concerned agencies. Moreover, more can be done to improve knowledge of the health and environmental impact of CO2 emissions and other greenhouse gases in most LDCs, including Nigeria (Houghton 2007; Marland et al. 2007). LDCs had been predicted to suffer more from the effects of climate change due to the fact that they have minimal resources to build adequate response in order to adapt to the environmental health outcomes of climate change. In Nigeria, much is being said, especially by the media, about climate change but research to document the increase of CO2 in urban areas is lacking. This forms the basis of this initial study in Ibadan, Nigeria, whose objectives were to: (1) Describe the selected activity-driven locations where CO2 is produced. (2) Determine the meteorological condition of the locations. (3) Determine the spatial and temporal variations in the concentration of CO2 in selected locations within Ibadan.
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Materials and methods
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Study area The sites for CO2 sampling were selected purposively. The selected sites are within Ibadan North Local Government Area and Ibadan South-West Local Government Area. Six different points were chosen randomly for sampling in each of the selected sites. The sampling sites were chosen based on the increased potentials of CO2 emissions from CO2 driven activities in the following areas: Market Areas: MA (Bodija market or MA1, Aleshinloye market or MA2); Abattoir Area: AA (Bodija Abattoir or AA1, Aleshinloye Abattoir or AA2); Dumpsite Area: DA (Bodija dumpsite or DA1, Aleshinloye dumpsite or DA2); Farmland Area: FA (Awo (UI) farmland or FA1, Aleshinloye farmland or FA2); Traffic Area: TA (Ojoo Park or TA1, Mokola round about park or TA2, Agbowo complex area or TA3); and Industrial Area: IA (Challenge Park as IA1, Oluyole industrial area as IA2). Please refer to the map (Figure 1). Onsite observation An observational checklist was used to record the observable sources of CO2 emissions and environmental conditions in the selected sites. Meteorological information The Nigerian Meteorological Agency, Samonda, Ibadan was approached for the monthly/year weather conditions for Ibadan metropolis during the sampling period. Parameters obtained included outdoor air temperature, relative humidity (RH), rainfall, and wind speed. CO2 monitoring The CO2 gas meter used to measure CO2 levels at the different locations was a factory calibrated (with zero air/nitrogen gas) Telaire 7001 connected to a HOBO U12 outdoor/ indoor data logger (Onset Corp, Bourne, MA); air temperature and RH were also collected by the HOBO. Each data point represented an average of one second measures over a preset duration (every 5–10 s). The height of the measurement was about 1 m above the ground. The distance from the source was about 100–200 m. Measurements were conducted on three weekdays for four consecutive weeks during the rainy season and on three weekdays for four consecutive weeks during the dry season of 2009–2010. Arithmetic means and standard deviations were computed by aggregating data, by season, by location (2–3 sites per area) in six target areas. Data management and statistical analysis Data were analyzed using descriptive statistics and inferential statistics such as the student t-test to compare means of CO2, ANOVA to assess variations across study locations and the wet versus dry seasons, correlation coefficients (e.g. ambient air temperature and CO2), and spatial and trend analysis using SPSS at level of statistical significance p = 0.05.
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Figure 1. locations.
(Color online) Map of Ibadan, Nigeria showing the carbon dioxide (CO2) sample
Results Environmental management practices in sample locations Table 1 shows the degree of waste management practices across study locations. Fairly adequate waste management practices were observed at Aleshinloye dumpsite (DA2) compared to poor management practices at Bodija dumpsite (DA1). Similarly, fairly
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Table 1. Onsite trained technician observations on waste management practices and presence of greenhouse gas emission sources, Ibadan, Nigeria, Nov. 2009–Sept. 2010.
Locations
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Adequate Dumpsite area DA1 DA2 Market area MA1 MA2 Abattoir area AA1 AA2 Traffic area TA1 TA2 TA3 Farm area FA1 FA2 Industrial area IA1 IA2
Presence of emission sources
Waste management practices Fairly adequate
Inadequate
High
Medium
+
++ ++
+
++ ++
++ ++ +
Low
+++
++
++
++
+++
++
+++
+++
++
+++ +++
+ + ++ ++
+++ ++
Notes: DA1: Bodija dumpsite; DA2: Alesinloye dumpsite; MA1: Bodija market; MA2: Alesinloye market; AA1: Bodija Abattoir; AA2: Alesinloye Abattoir; TA1: Ojoo park; TA2: Agbowo park; TA3: Mokola park; FA1: Awo Farm, FA2: Alesh farm; IA1: Challenge Industrial area; IA2: Oluyole Industrial area. +++ : Adequate or highly present; ++ : Fairly adequate or medium; + : Inadequate or low.
adequate waste management practices were observed at Aleshinloye market and abattoir (MA1 and AA1) while inadequate management practices were noticed at Bodija market and abattoir (MA2 and AA2). Waste management practices at Ojoo and Mokola parks (TA1 and TA2, respectively) were found to be fairly adequate compared to adequate at Agbowo park (TA3). Waste management practices at Challenge and Oluyole industrial areas (IA1 and IA2, respectively) were found to be fairly adequate. CO2 generating sources/activities in study locations Table 2 shows CO2 generation sources/activities at the study locations. Open burning of refuse was the only CO2 generation activity observed at Bodija dumpsite (DA1), while this and automobile sources were found at Aleshinloye dumpsite (DA2). Automobile, generator and bush burning sources of CO2 emissions were found at Bodija and Aleshinloye markets (MA2 and MA1, respectively). Open burning of refuse was observed at the Bodija and Aleshinloye abattoir (AA2 and AA1, respectively) as the only CO2 generation source. Automobile sources was the only CO2 emission source found at Ojoo park (TA1) while automobile and power generator sources were observed at Mokola and Agbowo parks (TA2 and TA3, respectively). Automobile and industrial sources were observed at Challenge industrial area (IA1), while the Oluyole industrial area (IA2) also had these and power generator and bush burning sources. Other observable CO2 generating sources found at Bodija market (MA2) and at Oluyole Industrial area (IA2) included explosives and emissions from burning firewood from nearby canteens.
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Table 2. Specific identified greenhouse gas emission sources at the sampling sites, Ibadan, Nigeria, Nov. 2009–Sept. 2010. Typical emission sources
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Locations Automobile
Generator use
Open burning
Industry
Others
– +
– –
+ +
– –
– –
+ +
+ +
– –
– –
+ –
– –
– –
+ +
– –
– –
+ + +
– + +
– – –
– – –
– – –
– –
– –
– –
– –
– –
+ +
– +
– –
+ +
– +
Dumpsite area DA1 DA2 Market area MA1 MA2 Abattoir area AA1 AA2 Traffic area TA1 TA2 TA3 Farm area FA1 FA2 Industrial area IA1 IA2
Notes: DA1: Bodija dumpsite; DA2: Alesinloye dumpsite; MA1: Bodija market; MA2: Alesinloye market; AA1: Bodija Abattoir; AA2: Alesinloye Abattoir; TA1: Ojoo park; TA2: Agbowo park; TA3: Mokola park; FA1: Awo Farm, FA2: Alesh Farm; IA1: Challenge Industrial area; IA2: Oluyole Industrial area. + (Present) and – (Absent); others include bush burning and explosives, emissions from firewood from nearby canteens.
Meteorological information for study area within period of investigation Table 3 shows the meteorological information between November 2009 and September 2010 as obtained from the Nigeria Meteorological agency of Ibadan. The highest RH was in April 2010 (87 %) while the lowest was in November 2009 (71 %). The highest atmospheric pressure was in November 2009 (989.6 hPa) while the lowest atmospheric pressure was in March 2010 (985.3 hPa). Figure 2 shows the minimum and maximum Table 3.
Meteorological data for Ibadan, Nigeria, November 2009–September 2010. Parameters (monthly average values are reported below)
Months (2009–2010) November December January February March April May June July August September
Relative humidity (%)
Pressure (hpa)
Average air temperature (°C)
71 78 78 76 76 78 83 83 86 87 86
989.6 986.7 986.6 985.9 986.3 985.9 986.6 988.6 988.8 988.8 988.1
27.8 29.2 29.1 30.5 30.1 29.5 28.0 27.5 25.9 25.7 25.9
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Figure 2. Maximum and minimum outdoor air temperatures, Ibadan, Nigeria, November 2009–September 2010.
temperatures between November 2009 and September 2010. Temperatures were highest in the month of February, with a maximum value of 36.1 °C and a minimum of 24.9 °C. The lowest temperatures were observed in April, with a maximum value of 28.8 °C and a minimum of 25.5 °C. In addition, a gradual rise in average rainfall was found between December 2009–January 2010 (main months of dry season) and May 2010, followed by a sharp fall in June 2010, then a steady rise in rainfall again from July to August–September 2010 (data not presented). These data collectively documented the annual presence of wet/rainy and dry seasons in Ibadan, Nigeria. Spatial variations in CO2 levels Figure 3 shows the arithmetic mean (average) CO2 levels across the sampling locations. The highest measured CO2 concentrations were found at Mokola round about (TA3),
Figure 3. Mean carbon dioxide (CO2) levels across study sampling locations, Ibadan, Nigeria, November 2009–September 2010. Notes: The lines show the minimum and maximum measures at each sampling location. DA1: Bodija dumpsite; DA2: Alesinloye dumpsite; MA1: Bodija market; MA2: Alesinloye market; AA1: Bodija Abattoir; AA2: Alesinloye Abattoir; TA1: Ojoo park; TA2: Agbowo park; TA3: Mokola park; FA1: Awo Farm; FA2: Alesh Farm; IA1: Challenge Industrial area; IA2: Oluyole Industrial area.
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with an arithmetic mean value of 383 ppm, followed by Ojoo park (TA1) with an arithmetic mean value of 376 ppm. The lowest CO2 concentrations were observed at Alesh farm (FA2), with an arithmetic mean value of 329 ppm. Temporal variations in CO2 levels Table 4 extends beyond Figure 3 and shows the average CO2 concentration in the dry and rainy seasons across the sampling locations. The average CO2 concentrations were lower during the dry season and higher during the rainy season. These differences were most likely due to the presence and strength of identified sources across study locations (see further discussion below) and atmospheric conditions (air flow/wind, pressure, and RH (see Table 3)). During the rainy season, the highest average CO2 level (±standard deviation), 390 ± 64 ppm, was recorded at the traffic area. This was followed by the market area, 375 ± 61 ppm, and abattoir, 357 ± 60 ppm. This was closely followed by the dumpsite area, 354 ± 56 ppm. The farmland area had the lowest CO2 level of 345 ± 55 ppm. In the dry season, market area recorded the highest average CO2 level (±standard deviation), 335 ± 45 ppm, followed by the abattoir, 335 ± 59 ppm, by traffic areas, 333 ± 56 ppm, and by the farmland area, 330 ± 44 ppm. The dumpsite area recorded the lowest CO2 level of 323 ± 50 ppm. Discussion The arithmetic mean (average) CO2 level across the sampling areas in the rainy season varied (see Table 4). The highest values were obtained in the traffic area (390 ± 64 ppm) while the lowest values were obtained at the farmland area (345 ± 55 ppm). The CO2 recorded at the traffic area sites could be attributable to the type of activities observed
Table 4.
Summary statistics for CO2 across seasons at the various sample locations. Rainy season
Dry season
Sample location
Mean
SD
Max
Min
Mean
SD
Max
Min
DA1 DA2 MA1 MA2 AA1 AA2 TA1 TA2 TA3 FA1 FA2 IA1 IA2
360.9 347.1 381.1 369.0 369.6 343.9 390.5 361.9 416.9 352.4 337.2 408.4 373.2
66.1 40.5 70.1 50.8 70.3 43.4 67.5 65.5 62.9 61.4 46.4 55.8 62.8
530 456 575 532 544 477 546 555 603 492 464 567 484
280 290 288 283 210 284 277 250 306 267 271 296 276
313.9 332.6 330.6 340.1 335.8 333.2 361.4 317.7 348.6 338.2 319.2 336.1 299.9
53.2 45.0 51.0 38.1 70.9 45.1 52.4 54.5 47.1 45.7 41.3 82.2 67.8
467 419 513 414 605 472 521 454 483 431 396 563 475
219 229 245 251 237 228 265 208 259 258 225 194 193
Notes: DA1: Bodija dumpsite; DA2: Alesinloye dumpsite; MA1: Bodija market; MA2: Alesinloye market; AA1: Bodija Abattoir; AA2: Alesinloye Abattoir; TA1: Ojoo park; TA2: Agbowo park; TA3: Mokola park; FA1: Awo Farm, FA2: Alesh Farm; IA1: Challenge Industrial area; IA2: Oluyole Industrial area.
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during the times of measurement as the observable checklist indicated consistently high traffic-associated CO2 sources in the parks and garages where sampling was done. Vehicular emissions from traffic and motor bikes on the roads were the major sources of CO2 emissions. This is not unexpected as combustion of automobile engines is known to contribute greatly to CO2 deposits in the atmosphere. Another online reference (www.123HelpMe.com 2012) has recently reported cars release approximately 30 % of the CO2 in the earth’s air. Vehicles, including cars, degrade the environment by releasing emissions from the combustion systems of these automobiles. Every time an automobile burns a gallon of gasoline it releases about 10 kilograms (about 20 lb) of CO2 (USEIA 2013). Recent research also noted increased CO2 emissions from mobile line sources in suburban/ urban areas surrounded by rural agriculture (Shendell et al. 2012). Ndoke et al. (2013) reported that areas with relatively heavy congestion have higher concentrations of CO2, while areas with minimal traffic have lower concentrations of CO2. For example, Sabo in Kaduna had the highest average concentration of 1840 ppm, while Asokoro (behind ECOWAS) in Abuja had the lowest average concentration of 1160 ppm (Ndoke et al. 2013). It should be noted that these were shorter term averages than in the present study (three weekdays in each of four weeks in each of two seasons during November 2009 and September 2010). The minimum CO2 value recorded at the farmland area during the rainy season could be due to the fact that green plants use CO2 during photosynthesis. Although, the environmental conditions of the farmland area were good at the time of measurement and there was a low observable source of CO2 emissions, the effect of CO2 being transported to the farmland area cannot be ruled out. Also, the farmland area was not expected to record a high CO2 concentration, even though according to Rees (2009), soil is the third largest carbon sink in the world. The concentrations were likely low because the sample sites used were not recently tilled, which would make the soil reservoir carbon available in the atmosphere. Higher CO2 enables plants to grow faster and larger and to live in drier climates. During the dry season, there was no significant difference between the mean CO2 levels obtained in all the sampling areas. The maximum CO2 level was recorded at the market area (335 ± 45 ppm), closely followed by the value obtained in the abattoir area (335 ± 60 ppm). The lowest value was obtained at the dumpsite area (323 ± 50 ppm). The maximum CO2 recorded at the Market area in the dry season can be attributed to vehicular emissions from traffic moving in and out of the market, car parks, commercial activities from stores, and the inflow of polluted air from nearby activity driven areas. However, Ndoke et al. (2003) recorded a considerably higher CO2 concentration in three major Nigerian markets with 1380 ppm in Wuse market, Abuja, 1630 ppm in Kasuwa market, Kaduna, and Sabo market in Kaduna recorded the highest CO2 level with 1840 ppm. Again, however, these were shorter term averages than in the present study (three weekdays in each of four weeks in each of two seasons during November 2009 and September 2010). The result of this study is further enhanced by the work of Pretty and Hine (2001) that found a major source of greenhouse gas emissions related to enteric fermentation and manure deposition and management in meat production and supply chains. Steffen and Bedker (1962) posited that meat processing and abattoir operations produce highly organic, highly nitrogenous, biologically degradable waste water with relatively high concentrations of suspended and dissolved solids and grease. The CO2 concentration is also expected to have come from the burning activities going on in the abattoir.
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The dumpsite recorded the lowest CO2 concentration, mainly because anaerobic respiration is prominent with only the upper surface area decomposing with the aid of atmospheric oxygen. The concentration of CO2 in the air changes with location and the seasons of the year (Gratani & Varone 2005). The mean CO2 levels varied substantially across the seasons (rainy and dry seasons) in the present study as well. The arithmetic mean CO2 levels varied significantly across the seasons (rainy and dry seasons). The higher arithmetic mean CO2 was recorded during the rainy season, 370 ± 63 ppm, while the average CO2 in the dry season was 332 ± 57 ppm. This result represents sampled locations (2–3 sites in six areas) within the two government administrative areas of Ibadan, Nigeria, and, therefore, perhaps different from the expected result given the ambient and built environment attributes of the individual locations. For instance, Ophardt (2003) found cyclic changes in CO2 concentrations occur due to seasonal variation of vegetation growth on farmland. Starting in May, the growth of plants and trees uses CO2, so the concentration decreases a little bit. Starting in October and November, the growth ceases, thus, causing the CO2 to increase. This trend was further corroborated by Brebner (2010). However, the seasonal CO2 concentration for the farmland in this experiment does not confirm the findings of Ophardt (2003). An average of 345 ± 55 ppm was recorded in the rainy season with a reduction to 323 ± 50 ppm in the dry season. It can be assumed the effect of other carbon sources could have contributed to the amount of CO2 in the atmosphere across seasons. Another impact follows the effects of climate change – due to higher air and surface temperatures – and the increased CO2 levels in the atmosphere. Andrews and Forster (2010) reported climate models indicated precipitation around the world will increase by roughly 2–3 % per degree Celsius of global surface temperature change. Trusilova and Churkina (2008) and Leggett (2011) corroborated this by stating the latest research suggested precipitation can also respond directly to the atmospheric heating caused by increases in CO2. This direct reaction occurs much faster than the precipitation modifications caused by global climate change because global climate change is relatively slow; it depends on how quickly the oceans warm – something that can take decades to centuries (Beamish 2004). This could apply to the situations in this report as the measured outdoor CO2 levels are within internationally acceptable range, i.e. comparable to other available data, but the impact of its effect or interplay of effects encompassing the abundance of CO2 in the atmosphere is already being felt in the amount of rainfall and direct effect of observable change in temperature. Conclusion This study assessed the carbon dioxide (CO2) levels of 13 selected activity driven locations (2–3 locations or sites per targeted area) in two local government areas of Ibadan, Nigeria, stratified into six targeted areas: Market area, Dumpsite area, Abattoir area, Farmland area, Traffic area, and Industrial area. Our study suggested emissions from tailpipes of vehicles primarily contributed to the measured CO2 in the two local government areas of Ibadan, Nigeria where the study was carried out, given the lack of other large point sources. Thus, vehicular emissions, if not controlled, can have detrimental effects on the long-term climate of Ibadan, Nigeria, and throughout the region, and indirectly lead to chronic diseases and environmental impacts being increasingly associated with climate change.
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Acknowledgements The authors are grateful to all the research assistants for their support throughout the course of the study and to the Department of Environmental Health Sciences for their technical support. This project was completed during the MPH program of O. Ojelabi. The authors also thank S.W. Kelly for internal manuscript review. This work was supported by the Georgia State University International Strategic Initiative and the Atlantic Philanthropies-Bermuda/U.K. office, 2006–2008.
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