Journal of Geology and Mining Research Vol. 3(5), pp. 131-136, May 2011 Available online http://www.academicjournals.org/jgmr ISSN 2006 – 9766 ©2011 Academic Journals Full Length Research Paper

Effects of gas flaring on surface and ground waters in Delta State Nigeria

Nwankwo C. N.1 and Ogagarue D. O.2*

1Department of Physics, University of Port Harcourt, Port Harcourt, Rivers State, Nigeria.

2Department of Earth Sciences, Federal University of Petroleum Resources, Effurun, Warri, Delta State, Nigeria.

Accepted 21 February, 2011

Surface and groundwater samples from gas flared region of Warri and a neighboring town, Abraka, where minimal gas flaring activity takes place were analyzed for their major, minor and trace element constituents and some physical characteristics. The results were evaluated with a view to determine and compare the quality and potability of the water from areas of high gas flaring activity with samples collected from an environment of minimal or no gas flaring in one hand, and between surface and subsurface waters. The range of concentration of heavy metals were lead (1.0 to 7.0 mg/l), barium (-2.0 to 5.9 mg/l), cadmium (0.0 to 2.0 mg/l), selenium (0.0 to 0.07 mg/l), copper (0.01 to 0.03 mg/l). Some of these concentration levels are above World Health Organization (WHO) maximum permissible limits. However, the concentrations are more in surface waters than in borehole waters, with the gas flare region having upper limit. pH concentration ranges from 5.05 to 6.81 with surface waters having lower values on the average than borehole waters. The Igbudu River in Warri with a value of 5.05 is the most acidic. Apart from some remote cases of heavy metals contamination and the pH, the general results showed that water from the boreholes in the study areas had acceptable quality for household utilization while the surface waters may require treatment. Key words: Gas flaring, groundwater quality, physicochemical, WHO.

INTRODUCTION The flaring of associated gas in Nigeria’s oil exploration fields dates back to about 45 years when oil production began in the Niger Delta. Over 170 trillion cubic feet of gas is produced in Nigeria, of which more than 70% is burnt off, with Shell Petroleum Development Company of Nigeria taking the lead (Ojeifo, 2009). Flared gas is the most significant source of air emission from offshore oil and gas installations. When these combustible vapours are burnt off into the atmosphere, they in turn form acid rain. The acid rain, when it falls to the earth’s surface, is corrosive in nature, and causes widespread damage to the environment. In addition to the gas flaring, an estimated annual average of about 2,300 m3 of refined and unrefined petroleum products is jettisoned into the environment through spillage (Bronwen, 2007), some of which are frequently discharged into the nearby rivers within the study area. *Corresponding author. E-mail: dogagaru@yahoo.com.

Most inhabitants of Delta State, South-South Nigeria where the study was carried out, depend on rivers and streams that run across the area as the main source of their daily water needs. Water (be it groundwater or surface water) meant for drinking, must however, meet quality standards. This quality is essentially determined by its physical, chemical, as well as microbiological characteristics. Acid rain leaches nutrients from the soil, slows the growth of trees and makes lakes uninhabitable for fish and other wildlife. This study is therefore aimed at determining the potability of both the surface and ground waters in a gas flared environment. METHOOLOGY Study areas The study areas lie within the Niger Delta sedimentary basin which is characterized by both marine and mixed continental quaternary sediments that are composed of abandoned beach ridges and mangrove swamps (Allen, 1999). The areas are bounded by

132 J. Geol. Min. Res.

Figure 1. Map of Delta state showing local government areas and study areas.

latitude 05031′ and 05048′ N, and longitude 050 45′ and 060 08′ E respectively (Figure 1). Both areas experience wet and dry seasons which are typical seasons in Nigeria (Ushie and Amadi, 2008).

Three stratigraphic layers - the Akata Formation, Agbada Forma-tion and Benin Formation characterize the area. Benin Formation which is the youngest is the main source of groundwater in the region. It consists of coarse grain sands, gravels, lignite streak and wood fragments with minor intercalations of shale (Kogbe, 1992; Reyment, 1965). Sampling procedure and laboratory analysis In carrying out the investigation, water was sampled from eight different locations within the period of July 2009 as follows: Location 1: Rain water in contact with roofing zinc at Warri. Location 2: Rainwater in contact with roofing zinc at Abraka. Location 3: Borehole water at Warri. Location 4: Borehole water at Abraka. Location 5: Rain water directly from the sky at Warri. Location 6: Rain water directly from sky at Abraka.

Location 7: River Water (Igbudu River) at Warri. Location 8: River Water (Ethiope River) at Abraka. The rain water was caught off the zinc roof during rain fall, using plastic buckets; while plastic cup was used to fetch water from the river. Similarly, borehole water was fetched from potable water tap. The samples were collec-ted in clean plastic bottles and taken to the laboratory for preservation and analysis using the various analytical techniques (Table 1). The plastic containers were wash- ed thoroughly with the various water samples before they were finally collected. This was to ensure that no foreign material was introduced into the sample. Analyses were done approximately 72 h after sampling. The concentration levels of the constituents were compared with the WHO (2007) recommended standards. RESULT AND DISCUSSION The results are presented and discussed in terms of the implication of the role of gas flare in modifying the quality

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Table 1. Summary of analysis methods used. Determination Analysis method Total hardness, total acidity, Ca2+, Mg2+ Titration Colour Lovibond comparator Turbidity Turbidimetric pH pH meter Conductivity, TDS, salinity Conductivity meter Trace metals: Fe, Mn, Cu, Cd, Pb, etc Atomic Absorption Spectrophotometer SO4

2-, PO42-, NO2

- and humid acid UV-Visible Spectrophotometer of surface and ground waters in relation to conforming to the guideline of the WHO for drinking water. Tables 2 and 3 summarize the analysis of the water samples from all the locations.

Graphs of the physicochemical parameters of the tested water samples are shown in Figure 2. All surface waters have objectionable taste while those from gas flared region have offensive odour when compared to the samples from locations 8 where no flaring activity is evident. The colour values followed the same trend as easily noticed in locations 7 and 8; indicating possible contamination of both surface waters of gas flared areas. Hardness values range of 17 to 35 mg/l was measured on surface waters at the gas flared zone as against 5 to 17 mg/l range obtained at Abraka town with minimal or no gas flaring. Similarly, the borehole water in gas flared area is harder than that from no-flared area. Rain and river waters have more hardness than borehole water. Its effect is decrease of lather formations of soaps and increase of scale formation on hot water heaters.

Both surface and borehole water samples are charac-terized by low conductivity (4.0 to 191.0 mg/l), although samples from gas flared environments are relatively more conductive. Water samples from Warri have conductivity values ranging from 4.0 to 191.0 mg/l as against 7.6 to 32.0 mg/l recorded for surface waters from Abraka. The high conductivity values from these gas flared environment indicates that the water is in contact with more inorganic constituents probably originating from the emissions of the flared gas (Etu-Efeotor, 1998). The geology of the area has been observed to be underlain mainly by the Benin Formation with high hydraulic conductance and transmissivity values (Ekine and Iheonunekwu, 2007; Ehirim and Nwankwo, 2010). These hydraulic characteristics of the aquifers promote infilteration of pollutants from flares into groundwater bodies.

The pH values of all the surface water samples reveal that most samples in the study areas are acidic in nature with those from gas flared zones being more acidic. This may be due to presence of inorganic constituents within the aquiferous materials of the decomposed rock, or as a result of industrial and oil exploration activities going on within the region.

Cyanide constituent of permissible limit were recorded in some surface water samples. Presence of cyanide in water can cause poisoning, and subsequent damage of spleen, brains and liver. Chromium content in water samples collected from the study areas is insignificant and unnoticeable. Aluminum contents in surface water samples from gas flared regions were slightly higher than those from Abraka locations. Heavy metal concentration in the waters is all below WHO permissible limits. Barium content in locations 1, 5 and 7 are very much, having values of 5.0, 5.9 and 4.0 mg/l respectively as against samples collect from locations 2, 6 and 8 with values of 1.0, 2.0 and 2.0 mg/l respectively. Barium can cause a variety of cardiac, gastrointestinal and neuromuscular effect associated with hypertension and cardio-toxicity in animals.

The value of lead obtained in all the water samples used in this study fall short of WHO standard. Its value for samples in gas flared Warri area ranges from 1.0 to 7.0 mg/l as against 0.0 to 1.0 mg/l range for non-flared area. Lead can enter the human body through food, water, and air. It is found in water when the water is slightly acidic, and its presence disrupts biosynthesis of hemoglobin and anemia, increases blood pressure, damages kidney, brain and causes infertility in men and abortion in women (Marcus, 2001).

Selenium content in gas flared area was higher than observed in samples from Abraka, with values slightly above WHO standard. Selenium is needed by humans and animals in small quantity, but when present in large amounts can cause damage to the nervous system, fatigues and irritability (Joseph, 2001).

Cadmium was present only in water samples from gas flared zones, having values ranging from 1.0 to 3.0 mg/l as against WHO standard value of 0.005 mg/l. In humans, long term exposure is associated with renal diseases, obstructive lung diseases, which have been linked to lung cancer. The content of fluoride, iron, manganese and copper in all water samples of the study Conclusion This study has revealed that surface waters quality in

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Table 2. Physicochemical parameters of samples from the study area.

Sample Location 1 Location 2 Location 3 Location 4 Location 5 Location 6 Location 7 Location 8 WHO (2007) standards Alkalinity (mg/l) 17.00 38.00 14.00 3.00 10.00 7.00 12.00 4.00 500 Colour (Hu) 15.0 11.00 11.00 17.00 44.00 33.00 36.00 19.00 15.0-85.0 Conductivity (mg/l) 4.00 32.30 96.4 38.6 15.40 7.60 191.60 17.40 - Hardness (mg/l) 25.00 17.00 18.00 6.00 17.00 5.00 35.00 10.00 500 pH (units) 6.27 6.76 6.81 6.47 5.83 6.43 5.05 6.04 6.5-8.5 Taste Offensive Offensive Inoffensive Inoffensive Offensive Offensive Offensive Offensive Inoffensive Temperature (°C) 28.90 30.10 30.00 29.60 30.20 29.70 29.60 30.70 - TDS (mg/l) 7.48 17.34 20.34 101.00 9.59 5.18 98.39 8.95 1000.00 Turbidity (NTU) 5.00 5.00 5.00 4.70 5.00 5.00 4.60 5.00 25.00

Table 3. Concentrations (mg/l) of anions and trace metals in water from the study areas. Sample Location 1 Location 2 Location 3 Location 4 Location 5 Location 6 Location 7 Location 8 WHO (2007) standards Aluminium 0.01 0.00 b/d 0.01 0.02 0.010 0.00 0.02 0.20 Barium 5.00 1.00 b/d 3.00 5.90 2.00 4.00 2.00 - Cadmium 1.00 0.00 0.00 3.00 2.00 0.00 1.00 0.00 0.005 Chloride 0.30 0.50 0.50 0.30 0.20 0.10 1.00 0.30 600 Chromium 0.00 0.00 0.00 0.00 0.01 0.01 0.00 0.00 0.05 Copper 0.03 0.00 0.02 0.00 0.02 0.05 0.01 1.00 1.5 Cyanide 0.00 0.00 0.00 0.00 0.00 0.001 0.001 0.00 0.10 Fluoride b/d b/d 0.03 b/d b/d b/d b/d b/d 1.50 Iron 0.03 0.00 0.01 0.05 0.06 0.07 0.04 0.03 1.00 Lead 3.00 1.00 1.00 1.00 3.00 0.00 7.00 1.00 0.05 Manganese 0.008 b/d 0.00 0.001 0.006 0.001 0.001 0.00 0.50 Nitrate 0.02 0.01 0.00 0.02 0.02 0.02 0.03 0.00 10.0-50.0 NH3 0.01 0.01 0.01 0.07 0.05 0.08 0.09 b/d - Phenol 0.001 0.003 b/d 0.002 0.003 0.04 0.07 0.02 - Phosphate 0.70 0.60 b/d 0.400 0.80 0.10 1.20 0.40 - Selenium 0.03 0.01 0.00 0.01 0.03 0.02 0.07 0.10 - Sulphate 2.00 2.00 3.00 4.00 3.00 2.00 5.00 0.00 400 Susp solid 3.00 b/d b/d b/d 8.00 27.00 7.00 b/d 30

b/d = below detection.

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Figure 2. Graphs of physicochemical parameters of tested water samples.

areas are within the WHO standards. However, the fluoride values were relatively higher in regions of minimal gas flaring. Warri is poor when compared with that of Abraka. The poor water quality can be linked to gas flaring activity, anthropogenic activities within the area as well as spillage of refined petroleum products to the river. The project also exposed that boreholes analyzed from Warri and Abraka are harmless for household consumption though there are isolated cases of presence of trace metals. The physicochemical approach has therefore, shown that waters in a gas flared environment contain higher concentrations of harmful metals such as barium, cyanide, selenium, cadmium, chromium, iron, manganese and copper. There is also an increase in conductivity, colour as well as a change in taste of water in the gas flaring environment when compared to areas having minimal gas flaring activities. ACKNOWLEDGEMENTS The authors are grateful to Akwa Ibom State water board for making their laboratory available to us through Mr. Martins Agbigor. We also thank Dr. C.A. Tse of the

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