This study investigated the effects of gaseous emissions from crude storage tank and gas flaring on air and rainwater quality in Bonny Industrial Island. Ambient air quality parameters, rainwater and weather parameters were collected at 60 m, 80 m, 100 m, 200 m and control plot for 4 weeks at the Bonny. Rainwater parameters were investigated using standard laboratory tests. Data analyses were done using Analysis of variance, pairwise t-test and Pearson’s correlation statistical tools. Results show that emission rates, volatile organic compound (VOC) noise and flare temperature decreased with increasing distance from flare points and crude oil storage tanks. Findings further revealed the emission rates varied significantly with distance away from the gas flaring point (F = 6.196; p = 0.004). The mean concentration of pollutants between gas flare site and crude oil storage tank showed that CO (0.02 ± 0.001 - 0.002 ±0.001), SPM (0.011 ± 0.001 - 0.01 ± 0.001), VOC (0.005 ± 0.001 - 0.01 ± 0.001) and NO 2 (0.04 ± 0.001 - 0.005 ± 0.000) had significant variations (p > 0.05) with CO, O 3 and NO 2 having higher concentrations at the gas flare site while SPM, and VOC were higher around the crude oil storage tank site. Wind turbulence was higher around the gas flaring point (4.93 TKE) than the crude oil storage tank (4.55 TKE). Similarly, there was significant variation in the sun radiation, precipitation, and wind speed caused by gas flaring (1582.25 w/m 2, 436.25 mm, 0.53 m/s) and crude oil storage tank (1536.25 w/m 2, 3.91.41 mm, 0.51 m/s). There were also significant variations in flared temperature (F = 22.144; p = 0.001); NO 2 (F = 8.250; p = 0.001), CO (F = 6.000; p = 0.004) and VOC (F = 5.574; p = 0.006) with distance from the gas flaring point. The variation in the rainwater parameters with distance from the gas flaring indicated significant variations in pH (F = 5.594; p = 0.006). The study showed that the concentration of VOC and particulates were high in the supposedly control area which is perceived to be safe for human habitation. Significant variations exist in emission rate (p = 0.015), flare temperature (p = 0.001), NO 2 (p = 0.003), VOC (p = 0.001), noise (p = 0.041), hydrogen carbonate (p = 0.037) and chromium (p = 0.032) between the gas flaring and crude oil storage tank. Regular monitoring is advocated to mitigate the harmful effects of the pollutants.
Emissions from oil prospecting platforms and its environmental problems have continued to attract the attention of air pollution meteorologist and environmental experts amongst others [
From the available literature, it is obvious that air pollution problems associated with gas flares is not new, however, the combined effects of both flare gases and importantly emissions from crude oil storage tanks which are not visible especially as they affect ambient air and rainwater quality has not been given due attention in the literature. This is the gap which this paper intends to provide. To achieve this, the following conceptual questions are posed; what is the difference in the effects of gas flaring and gas emission from storage tank on rainwater? What is the difference in the effects of gas flaring and gas emission storage tank on air quality? Is there any difference in the meteorological parameters (air temperature, wind speed, atmospheric pressure, relative humidity, precipitation and sun radiation) with distance away from gas flaring point and crude oil storage tank in the study area?
The study was carried out in Bonny Island, Bonny LGA, Rivers State. The study area was located between latitudes 4˚458'N and 4˚45'N, and longitudes between 7˚13'E and 7˚21'E (
design storage capacity of 7.5 million barrels [
This study adopted the Concept of Air Pollutants Spread in explaining the effects of emissions from crude oil storage tanks and gas flaring on ambient air and rain water quality. According to [
The sample sites were purposively selected to assess the concentration; nature of gases emitted and flared; location of crude storage tank and gas flare point as well as their orientation. Different samples at various proximities (60 m, 80 m, 100 m and 200 m) from the crude storage tank and gas flare location were taken and measurements and experimentations carried out according to standards for both gases and rainwater. In all, nine sampling points were considered. These include eight points from the primary emission sources and one control point. At each sampling point, ambient air quality and rainwater quality were sampled. Rainwater analysis was done for the following parameters: pH, Conductivity, SOx (Sulphate), NOx (Nitrate), Hydrogen carbonate (HCO3), Total Hydrocarbon (THC), Copper (Cu) and Chromium (Cr). pH was measured in-situ using a Beckman Electrode pH meter. Electrical conductivity was determined using a Jenway PCM1 portable conductivity meter. The total hydrocarbon compound in rainwater samples was carried out using Agilent 6890N Gas Chromatograph-Flame Ionization Detector (GC-FID) instrument. Heavy metals (Cu and Cr) were analyzed using atomic absorption spectrophometer (AAS) as described in APHA 3111B and ASTM D3651. This involved direct aspiration of the sample into an air/acetylene or nitrous oxide/acetylene flame generated by a hollow cathode lamp at a specific wavelength peculiar only to the metal programmed for analysis. For every metal investigated, standards and blanks were prepared and used for calibration before samples were aspirated. Concentrations at specific absorbance displayed on the data system monitor for printing. Limit of detection is <0.001 mg/l. NO2, SO2 and HCO3 were analyzed by ion chromatography (Metrohm 761 Compact IC with suppressed module, equipped with an anion-separator column (Dual 2). Sampling was performed weekly for 4-week period. All selected sites in the Bonny Terminal were old but still in production. Records indicate that the selected sites have been flared for 52 years. The selection of such old sites was based on the premise that the cumulative effects of waste gas emissions and flares are a better representation of speculated air quality-flare site relationship.
Descriptive analysis was used to explain mean values of air quality parameters, rainwater parameters and meteorological parameters with respect to distance in the study area. Analysis of variance (ANOVA) was used to analyze the conceptual question formulated for this study. Pearson’s Product Moment Correlation (PPMC) statistics was employed in testing for the significance of the relationships between the weather parameters and air/ rainwater quality parameters.
In the comparative analysis between the effects of gas flaring and crude oil storage tank on air quality (
Air Quality | Gas Flaring | Crude Oil Tank | T-test (Pairwise) Significance (p value) |
---|---|---|---|
Emission Rate (scf/hr) | 10,225.05 ± 36.9 | 10,149.00 ± 26.65 | 0.015* |
Flare Temperature (˚C) | 28.30 ± 0.18 | 27.80 ± 0.09 | 0.001* |
SO2 (ppm) | 0.00 ± 0.00 | 0.00 ± 0.00 | Not Applicable |
NO2 (ppm) | 0.004 ± 0.001 | 0.0005 ± 0.00 | 0.003* |
CO (ppm) | 0.002 ± 0.001 | 0.002 ± 0.001 | Not Applicable |
SPM (ppm) | 0.011 ± 0.001 | 0.01 ± 0.001 | 0.781 (NS) |
VOC (ppm) | 0.005 ± 0.001 | 0.04 ± 0.006 | 0.001* |
H2S (ppm) | 0.00 ± 0.00 | 0.00 ± 0.00 | Not Applicable |
O3 (ppm) | 0.01 ± 0.00 | 0.01 ± 0.00 | Not Applicable |
Noise (db) | 67.45 ± 1.74 | 69.03 ± 1.61 | 0.041* |
N = 30; *Significant at p < 0.05; NS―Not Significant.
shown
Similarly, findings revealed that comparatively, the mean pH of rainwater around gas flaring was 6.66 while it was 6.53 around the crude oil storage tank (
The comparative variation in the effects of gas flaring and crude oil storage tank on weather parameters is shown in
Rainwater Parameters | Gas Flaring | Crude Oil Tank | T-test (Pairwise) Significance (p Value) |
---|---|---|---|
pH | 6.66 ± 0.12 | 6.53 ± 0.11 | 0.157 |
Conductivity (μs/cm) | 35.08 ± 3.53 | 33.18 ± 3.32 | 0.666 |
Total Hydrocarbon (mg/l) | 0.01 ± 0.00 | 0.01 ± 0.00 | Not Applicable |
Nitrate (mg/l) | 0.56 ± 0.09 | 0.68 ± 0.08 | 0.303 |
Sulphate (mg/l) | 1.16 ± 0.11 | 1.32 ± 0.14 | 0.093 |
Hydrogen Carbonate (mg/l) | 0.0235 ± 0.002 | 0.018 ± 0.002 | 0.037* |
Copper (mg/l) | 0.001 ± 0.00 | 0.001 ± 0.00 | Not Applicable |
Chromium (mg/l) | 0.0012 ± 0.00 | 0.21 ± 0.09 | 0.032* |
N = 20; *Significant at p < 0.05.
Weather Parameter | Gas Flaring | Crude Oil Tank | T-test (Pairwise) Significance (p value) |
---|---|---|---|
Air Temperature (˚C) | 27.99 ± 0.31 | 28.85 ± 0.24 | 0.007* |
Wind Speed (m/s) | 0.53 ± 0.05 | 0.51 ± 0.06 | 0.791 |
Atmospheric Pressure (psi) | 14.71 ± 0.01 | 14.69 ± 0.003 | 0.200 |
Relative Humidity (%) | 85.74 ± 1.25 | 82.01 ± 0.86 | 0.001* |
Wind Turbulence (A-F) | 4.93 ± 0.27 | 4.55 ± 0.23 | 0.186 |
Precipitation (mm) | 436.25 ± 3.45 | 391.42 ± 40.28 | 0.006* |
Sun Radiation (w/m2) | 1582.25 ± 20.79 | 1536.25 ± 25.68 | 0.028* |
N = 30; *Significant at p < 0.05.
Findings further revealed that the emission rates varied significantly with distance away from the gas flaring point (F = 6.196; p = 0.004). There was also significant variation in the flare temperature (F = 22.144; p = 0.001); NO2 (F = 8.250; p = 0.001), CO (F = 6.000; p = 0.004) and VOC (F = 5.574; p = 0.006) with distance from the gas flaring point. The variation in the rainwater parameters (
The relationships between weather and air quality parameters around the gas flaring point are showed that there was significant positive correlations between flare temperature and atmospheric pressure (r = 0.610; p < 0.05); relative humidity (r = 0.452; p < 0.05); wind turbulence and (r = 0.497; p < 0.05). Meanwhile, flare temperature had negative relationship with precipitation (r = −0.506; p < 0.05). However, CO was significantly and positively correlated with air temperature (r = 0.742; p < 0.05) and negatively with relative humidity (r = −0.614; p < 0.05). Furthermore, air temperature had significant positive correlation with VOC (r = −0.765, p < 0.05) while relative humidity had negative correlation with VOC (r = −0.617, p < 0.05). More importantly, wind speed had significant positive correlation with noise (r = 0.693; p < 0.05).
Result of the relationships between weather parameters and air quality parameters around the crude oil storage tank indicated (
Sum of Squares | df | Mean Square | F | Sig. | ||
---|---|---|---|---|---|---|
pH | Between Groups | 2.205 | 4 | 0.551 | 3.071 | 0.049* |
Within Groups | 2.693 | 15 | 0.180 | |||
Total | 4.898 | 19 | ||||
Conductivity | Between Groups | 2622.065 | 4 | 655.516 | 6.249 | 0.004* |
Within Groups | 1573.572 | 15 | 104.905 | |||
Total | 4195.637 | 19 | ||||
THC | Between Groups | 0.000 | 4 | 0.000 | 0.000 | 1.000 |
Within Groups | 0.000 | 15 | 0.000 | |||
Total | 0.000 | 19 | ||||
Nitrate | Between Groups | 1.055 | 4 | 0.264 | 2.648 | 0.075 |
Within Groups | 1.494 | 15 | 0.100 | |||
Total | 2.548 | 19 | ||||
Sulphate | Between Groups | 4.552 | 4 | 1.138 | 5.825 | 0.005* |
Within Groups | 2.931 | 15 | 0.195 | |||
Total | 7.483 | 19 | ||||
Hydrogen Carbonate | Between Groups | 0.001 | 4 | 0.000 | 3.850 | 0.024* |
Within Groups | 0.001 | 15 | 0.000 | |||
Total | 0.002 | 19 | ||||
Copper | Between Groups | 0.000 | 4 | 0.000 | . | . |
Within Groups | 0.000 | 15 | 0.000 | |||
Total | 0.000 | 19 | ||||
Chromium | Between Groups | 2.022 | 4 | 0.506 | 7.972 | 0.001* |
Within Groups | .951 | 15 | 0.063 | |||
Total | 2.974 | 19 |
N = 30; *Significant at p < 0.05.
Also, CO was positively correlated with air temperature (r = 0.650, p < 0.05) and negatively correlated with relative humidity (r = −0.502; p < 0.05). Furthermore, VOC was positively correlated with relative humidity (r = 0.475, p < 0.05) and wind turbulence (r = 0.520, p < 0.05). Nevertheless, noise had positive relationship with wind speed (r = 0.693, p < 0.05). Similarly, the relationships between weather parameters and rainwater parameters around gas flaring point (
Findings on the relationships between weather and rainwater parameters in crude oil storage tank (
Sum of Squares | df | Mean Square | F | Sig. | ||
---|---|---|---|---|---|---|
Air Temperature | Between Groups | 15.573 | 4 | 3.893 | 2.597 | 0.049* |
Within Groups | 22.485 | 15 | 1.499 | |||
Total | 38.058 | 19 | ||||
Wind Speed | Between Groups | 0.197 | 4 | 0.049 | 1.078 | 0.402 |
Within Groups | 0.685 | 15 | 0.046 | |||
Total | 0.882 | 19 | ||||
Atmospheric Pressure | Between Groups | 0.012 | 4 | 0.003 | 1.535 | 0.243 |
Within Groups | 0.029 | 15 | 0.002 | |||
Total | 0.041 | 19 | ||||
Relative Humidity | Between Groups | 195.828 | 4 | 48.957 | 1.857 | 0.171 |
Within Groups | 395.500 | 15 | 26.367 | |||
Total | 591.328 | 19 | ||||
Wind Turbulence | Between Groups | 5.000 | 4 | 1.250 | 0.800 | 0.544 |
Within Groups | 23.438 | 15 | 1.563 | |||
Total | 28.438 | 19 | ||||
Precipitation | Between Groups | 112,139.445 | 4 | 28,034.861 | 1.750 | 0.191 |
Within Groups | 240,242.085 | 15 | 16,016.139 | |||
Total | 352,381.530 | 19 | ||||
Sun Radiation | Between Groups | 26,330.000 | 4 | 6582.500 | 0.716 | 0.594 |
Within Groups | 137,893.750 | 15 | 9192.917 | |||
Total | 164,223.750 | 19 |
N = 20; *Significant at p < 0.05.
Air Quality | Weather Parameters | ||||||
---|---|---|---|---|---|---|---|
Air Temperature | Wind Speed | Atmospheric Pressure | Relative Humidity | Wind Turbulence | Precipitation | Sun Radiation | |
Emission rate | −0.277 | 0.359 | 0.053 | 0.367 | 0.378 | −0.386 | 0.305 |
Flare Temperature | −0.366 | 0.346 | 0.610* | 0.452* | 0.497* | −0.506* | 0.322 |
NO2 | −0.312 | 0.175 | 0.320 | 0.375 | 0.257 | −0.345 | 0.104 |
CO | 0.742* | −0.336 | −0.225 | −0.614* | −0.288 | 0.361 | 0.050 |
SPM | 0.098 | 0.189 | −0.035 | −0.196 | −0.156 | −0.283 | −0.232 |
VOC | 0.765* | −0.303 | −0.022 | −0.617* | −0.225 | 0.444* | −0.064 |
Noise | −0.247 | 0.693* | 0.025 | −0.085 | −0.227 | −0.084 | −0.061 |
N = 20; *Significant at p < 0.05.
influence in the chromium level in the rain water. Wind speed fell within 0.35 m/s - 0.63 m/s. This suggests that the wind speed in the entire study area is calm which suggest accumulation of pollutants at the ground level. [
Rainwater Parameters | Weather Parameters | ||||||
---|---|---|---|---|---|---|---|
Air Temperature | Wind Speed | Atmospheric Pressure | Relative Humidity | Wind Turbulence | Precipitation | Sun Radiation | |
pH | 0.438 | −0.248 | 0.179 | −0.210 | 0.286 | −0.360 | 0.496* |
Conductivity | −0.332 | 0.257 | −0.090 | 0.315 | −0.044 | −0.152 | −0.099 |
Nitrate | 0.518* | −0.008 | 0.191 | −0.328 | −0.154 | −0.046 | 0.213 |
Sulphate | −0.477* | 0.556* | 0.125 | 0.392 | 0.142 | −0.170 | 0.006 |
Hydrogen Carbonate | −0.306 | −0.040 | 0.043 | 0.153 | 0.216 | −0.138 | −0.139 |
Chromium | 0.093 | −0.218 | −0.039 | −0.111 | −0.216 | −0.011 | −0.512* |
N = 20; *Significant at p < 0.05.
Rainwater Parameters | Weather Parameters | ||||||
---|---|---|---|---|---|---|---|
Air Temperature | Wind Speed | Atmospheric Pressure | Relative Humidity | Wind Turbulence | Precipitation | Sun Radiation | |
pH | 0.114 | −0.533* | −0.450* | 0.002 | 0.000 | −0.042 | 0.245 |
Conductivity | −0.110 | 0.033 | 0.570* | 0.113 | 0.224 | −0.075 | −0.037 |
Nitrate | 0.566* | 0.115 | −0.061 | −0.659* | −0.001 | 0.346 | 0.024 |
Sulphate | −0.332 | 0.449* | 0.430 | 0.152 | 0.132 | −0.148 | −0.199 |
Hydrogen Carbonate | −0.169 | 0.291 | −0.215 | 0.047 | −0.029 | −0.177 | −0.118 |
Chromium | 0.078 | −0.137 | 0.158 | −0.033 | −0.165 | 0.223 | −0.277 |
N = 20; *Significant at p < 0.05.
of pollutants at ground level. By implication, this makes the accumulation of the air and rainwater pollutants to be deposited heavily around the sources of the pollutants (Gas flaring point and Crude oil storage tank.
This study has shown that the air and rainfall water quality are compromised as a result of emissions from gas flare and crude oil storage tanks in Bonny. Specifically, the turbulent generated from the flare instigated the initial dispersion of the pollutants which were transported to the residential areas found downwind of the industrial area in the island. This compromised the air quality of the residential areas which spelled dome for the island residents. However, the moderating influence of the sea breeze from the Gulf of Guinea may have influenced the variations in temperature around the residential areas causing a cooling effect which favours stagnation of atmospheric pollutants. These have serious implications for the health of residents and the conditions of the environment at large.
Vincent Ezikornwor Weli,Nsikak I. Itam, (2016) Impact of Crude Oil Storage Tank Emissions and Gas Flaring on Air/Rainwater Quality and Weather Conditions in Bonny Industrial Island, Nigeria. Open Journal of Air Pollution,05,44-54. doi: 10.4236/ojap.2016.52005