Heavy Metals and Petroleum Hydrocarbon Concentration in water and Periwinkles (Tympanotonus fuscatus L.) obtained from Calabar River, Cross River State, Nigeria

Concentration of heavy metals; Cd, Cr and Pb along with total petroleum hydrocarbon (TPH) in periwinkles (Tympanotonus fuscatus) from Calabar River in Nigeria was assessed to determine their suitability for human consumption. Water and periwinkle samples were collected from five stations and taken to the laboratory for analysis. Heavy metals were analysed using Graphite Furnace Atomic Absorption Spectrophotometer (GFAAS-AA240FS) after digestion with concentrated Nitric acid while GC–FID (6890N, Agilent) was used to analyze TPH after liquid–liquid extraction of water and Soxhlet extraction of periwinkle tissues. The results obtained showed Pb as the highest (7.73±2.29 mg/l) occurring metal in water at station four, the lowest (1.88±0.90 mg/l) was Cd in station one while TPH was highest (259.47±45.90 mg/l) in station four and lowest (155.39±32.07 mg/l) in station two. Metal concentrations in water across sampling stations were not significantly different (p<0.05) while both metals and TPH exceeded the WHO standards for drinking water. Metal concentrations in periwinkles did not differ significantly (p<0.05) across sampling stations, they had exceeded the FAO standards with Pb and Cd being the highest (6.15±2.25 mg/kg) and lowest (0.69±0.43 mg/kg) in stations three and four respectively while TPH in periwinkles was highest (130.58±34.82 mg/kg) in station five and lowest (98.37±31.52 mg/kg) in station one which exceeded the FAO limit hence water and periwinkles from Calabar River are considered unsafe for consumption. Negative correlations of –0.03, –0.20 and –0.37 in TPH, Cr and Cd respectively suggests that other sources of these pollutants in periwinkles exist.