Hydrocarbons and some Heavy Metals in Tissues of Tympanotonus fuscatus periwinkles from Warri river of Niger Delta Area of Nigeria

The levels of petroleum hydrocarbons and some heavy metals in the tissues of Tympanotomus fuscatus periwinkle from Warri River of Niger Delta area were investigated. Six hundred samples of periwinkles collected fortnightly for a period of six months from three stations (Jala. Ubeji and Suoroagbene-control) along Warri River were analyzed using Atomic Absorption Spectrophotometry for the determination of heavy metals. The mean levels of total hydrocarbon varied from 0.0045mg/g to 0.093 mg/g and mean lead (Pb) levels varied from 0.0023 ppm to 0.046 ppm. Mercury (Hg) and Cadmium (Cd) were below the instrument detection limit of <0.001 ppm in all three stations. The levels of total hydrocarbon at Jala and Ubeji were significantly (P < 0.05) higher than at Suoroagbene, the control station. The level of lead at Suoroagbene was significantly lower (P < 0.05) than at Jala and Ubeji. The higher levels of total hydrocarbon and lead in tissues of periwinkles from Jala and Ubeji were attributed to more industrial activities and close proximity of the stations to the major road where emission from automobiles abound more than Suoroagbene, which is purely a residential area. This study demonstrated the evidence of bioaccumulations of total hydrocarbons and lead but levels were below the recommended tolerable levels and also lower than levels reported previously in periwinkle tissues by some authors in same river. This implies that periwinkles from Warri River are safer now than before as a food source for consumers who delight in this delicacy. However, constant monitoring of water bodies receiving effluents is emphasized in order to forestall cumulative effects of pollutants which may lead to sub-lethal consequences in the aquatic fauna and clinical poisoning to man. @JASEM Oil pollution, one of the environmental consequences of crude oil exploration and exploitation activities, produces aqua-toxicological effects, which are deleterious to aquatic life (Kori-Siakpere, 2000; Agbogidi et al., 2005). Aquatic organisms can acquire trace elements from food, suspended particles or directly from the water (Carvalho and Fowler, 1993). Many of these pollutants are nonbiodegradable compounds and dangerous due to their innate ability to constantly remain within the ecosystem (Hernandez-Hernandez et al., 1990). According to Vuuren et al. (1999) metal pollutants are currently considered to be some of the most toxic contaminants present world-wide. The adverse effect of heavy metals in aquatic environment has been documented (Jack et al. 2005, Ideriah, 2005, Zeinab, 2006). Many aquatic organisms have been used as sensitive indicators of heavy metal pollution (Osibanjo and Ajayi, 1980, Foulkes. 1990). Bioaccumulation in aquatic organisms such as crustaceans, mollusk and fish has been reported to depend on exposure time and concentrations of metals in the water (Jackson et al. 2004). Periwinkles are mollusk and have been reported to be one of the preferred pollution bio monitors because of their sedentary and bottom feeding habits which make them good accumulators of heavy metals and polycyclic aromatic hydrocarbons (Wilson et al., 1992; Jack at al., 2005). Periwinkles are mass-consumer products constituting re1atively cheap animal protein in Delta State (Ekanem and Otti, 1997) and are one of the many delicacies in the Nigeria cuisines. Tympanotomus fuscatus is a common species of periwinkle found in the Warri River. Warri River stretches within latitude 5 0 21’ – 6 0 .00’N and Longitude 5 0 24’ – 6 0 .21’E and has outlets to the Atlantic Ocean. The river which supports major commercial activities such as shipping of crude oil, fishery, and recreational fishing and prawning has been implicated in heavy metal contamination in the past (Egborge, 1991, Edema et al, 1992, Ayenimo et al., 2005). With an extensive utilization of crude oil and its refined products in Nigeria, the Niger Delta region especially the Warri River, would continue to receive run-offs or industrial effluents which will contaminate and bioaccumulate in aquatic organisms. Periodic assessment of levels of these pollutants in food sources like periwinkles from the river is necessary to assure their safety for human consumption. This research determines the levels of petroleum hydrocarbons and some heavy metals in the tissues of Tympanatonus fuscatus from Warri River. MATERIALS AND METHODS Six hundred samples of Tympanotonus fuscatus periwinkles were randomly collected fortnightly from three stations namely: Jala and Ubeji, representing areas more susceptible to pollution as a result of high industrial activities and Suoroagbene, a residential area along the Warri River for a period of six months. Periwinkles were washed and frozen at -5°C until they were ready for analysis. Later, periwinkles were deshelled and the soft tissues air-dried at room temperature for three weeks and analyzed at the Petroleum Training Institute Efferent Laboratory, Warri. Tissues of periwinkles were ground to powder form, sieved, weighed and ashed at 77°C for two hours in a furnace. Ten grams ashed periwinkle tissues were digested with 20 ml of concentrated HNO3 and heavy metal determined using solar model-unicam 969 Atomic Absorption

Oil pollution, one of the environmental consequences of crude oil exploration and exploitation activities, produces aqua-toxicological effects, which are deleterious to aquatic life (Kori-Siakpere, 2000;Agbogidi et al., 2005).Aquatic organisms can acquire trace elements from food, suspended particles or directly from the water (Carvalho and Fowler, 1993).Many of these pollutants are nonbiodegradable compounds and dangerous due to their innate ability to constantly remain within the ecosystem (Hernandez-Hernandez et al., 1990).According to Vuuren et al. (1999) metal pollutants are currently considered to be some of the most toxic contaminants present world-wide.
The adverse effect of heavy metals in aquatic environment has been documented (Jack et al. 2005, Ideriah, 2005, Zeinab, 2006).Many aquatic organisms have been used as sensitive indicators of heavy metal pollution (Osibanjo andAjayi, 1980, Foulkes. 1990).Bioaccumulation in aquatic organisms such as crustaceans, mollusk and fish has been reported to depend on exposure time and concentrations of metals in the water (Jackson et al. 2004).Periwinkles are mollusk and have been reported to be one of the preferred pollution bio monitors because of their sedentary and bottom feeding habits which make them good accumulators of heavy metals and polycyclic aromatic hydrocarbons (Wilson et al., 1992;Jack at al., 2005).
Periwinkles are mass-consumer products constituting re1atively cheap animal protein in Delta State (Ekanem and Otti, 1997) and are one of the many delicacies in the Nigeria cuisines.Tympanotomus fuscatus is a common species of periwinkle found in the Warri River.Warri River stretches within latitude 5 0 21' -6 0 .00'Nand Longitude 5 0 24' -6 0 .21'Eand has outlets to the Atlantic Ocean.The river which supports major commercial activities such as shipping of crude oil, fishery, and recreational fishing and prawning has been implicated in heavy metal contamination in the past (Egborge, 1991, Edema et al, 1992, Ayenimo et al., 2005).
With an extensive utilization of crude oil and its refined products in Nigeria, the Niger Delta region especially the Warri River, would continue to receive run-offs or industrial effluents which will contaminate and bioaccumulate in aquatic organisms.Periodic assessment of levels of these pollutants in food sources like periwinkles from the river is necessary to assure their safety for human consumption.This research determines the levels of petroleum hydrocarbons and some heavy metals in the tissues of Tympanatonus fuscatus from Warri River.

MATERIALS AND METHODS
Six hundred samples of Tympanotonus fuscatus periwinkles were randomly collected fortnightly from three stations namely: Jala and Ubeji, representing areas more susceptible to pollution as a result of high industrial activities and Suoroagbene, a residential area along the Warri River for a period of six months.Periwinkles were washed and frozen at -5°C until they were ready for analysis.Later, periwinkles were deshelled and the soft tissues air-dried at room temperature for three weeks and analyzed at the Petroleum Training Institute Efferent Laboratory, Warri.Tissues of periwinkles were ground to powder form, sieved, weighed and ashed at 77°C for two hours in a furnace.Ten grams ashed periwinkle tissues were digested with 20 ml of concentrated HNO 3 and heavy metal determined using solar model-unicam 969 Atomic Absorption Spectrophotometer.The Soxhlet Extraction Gravimetric method was used for determination of hydrocarbon.Fifty grams of air-dried and ground periwinkle tissues were extracted in Soxhlet Extractor for 8 hours using hexane acetone (60:40) cocktail solvent.Soluble metallic soaps were hydrolyzed by acidification.Oils and solids or viscous grease present were separated from liquid samples by filtration.After extraction, the residue after solvent evaporation was weighed to determine the oil and grease content.Compounds volatilized at or below 103°C were lost when filter was dried up.Data obtained were subjected to one way analysis of variance using statistical package for social sciences (SPSS) at 95% confidence interval and means separated using Duncan's -Multiple range Test (DMRT).

RESULTS AND DISCUSSION
The concentration of total hydrocarbons (THC) and heavy metals in the tissues of periwinkles analyzed are presented in Table 1.The mean THC concentrations varied from 0.0045mg/g to 0.093mg/g in all three stations sampled for the study.The concentrations of THC at Jala and Ubeji were significantly higher (P < 0.05) than at Suoroagbene, the control station.A slight variation in concentration of THC was however, observed in Jala and Ubeji.The higher mean concentrations of THC observed in Jala and Ubeji stations were probably due to more industrial activities in these stations than in Suoroagbene, the control station, which is more of a residential area.
Table 1: Mean levels of total hydrocarbon (THC) and some heavy metals in tissues of Tympanotonus fuscatus from Warri River <0.001-less than Instrument Detection Limit (IDL).
Though the control station is residential, some level of pollution was observed.Variations in levels of pollution could be due to the varying levels of activities at each station and the extent of discharge of wastes into the water body.According to Ideriah et al., (2005), levels of pollution observed suggest that in addition to tidal actions, domestic wastes containing discharges of metal and THC may have contributed to the level of pollution in aquatic organisms.Petroleum and allied industries located close to Jala and Ubeji stations are likely sources of the higher level of THC observed in these stations .The concentrations of THC in tissues of periwinkles in all three stations were generally low compared with levels of previous reports from the same river (Edema et al., 1992) and similar polluted river (Ideriah et al., 2005).Jack et al. (2005)  and that marine organisms accumulate hydrocarbons due to their sedentary and bottom feeding habit.
Figure 1, shows levels of hydrocarbons in tissues of periwinkles from Warri River.
The presence of heavy metals in the tissues of periwinkles supports the report of Ayenimo et al. (2005), which showed the presence of heavy metals in tissues of periwinkles from Warri River.Mean lead (Pb) concentrations varied from 0.0027ppm to 0.046ppm.Mercury (Hg) and cadmium (Cd) were below the Instrument Detection Limit (IDL) of <0.001ppm in all three stations.The concentration of lead (Pb) at Suorogbene was significantly lower (P < 0.05) than at Jala and Ubeji.The concentration of lead was also higher in Jala and Ubeji stations than in Suoroagbene, the control station.The further location and longer distance of Suoroagbene from the major road could be responsible for the lower mean concentration of lead observed in this station.This implies that emissions from automobile activities on the major roads close to Jala and Ubeji could have also contributed to the higher level of pollution observed in the stations.Similar observations on bioaccumulation of heavy metal pollution had earlier been reported in tissues of oysters and periwinkles (Cummingham and Tripp, 1975;Davies et al, (2006).Figure 2, shows levels of heavy metals in tissues of periwinkles from Warri River as compared with WHO ( 2004) provisional weekly tolerance intake of Lead, Mercury and Cadmium.
This study demonstrated evidence of bioaccumulation of total hydrocarbons (THC) and lead in the tissues of periwinkles from Warri River.Levels were however, observed to be below the recommended tolerance levels of 0.01mg/g for hydrocarbon and 10mg/kg for lead (WHO, 2004;Davies et al, 2006).The values obtained in this study were also lower than those reported in previous study which was suggestive of sub-lethal toxicity in humans (USEPA, 1986;Sharp, 1987), Ayenimo et al., 2005).The results of this study show imminent problems of contamination in Warri River if control measures are not put in place.This emphasizes the importance of constant monitoring of rivers and other water bodies receiving effluents in order to forestall cumulative effects of pollution in the river which may lead to sub lethal consequences in the aquatic fauna and clinical poisoning to man.

Fig 1 .
Fig 1. Levels of heavy metals in tissues of periwinkles from Warri River compared with Provisional weekly tolerance intake (PWTI).
noted that hydrocarbons take longer time to sink to the riverbed