Investigation and Assessment of Polycyclic Aromatic Hydrocarbons Concentrations in Sediments at Drainage Discharge Points into the Mangrove Stretch of New Calabar River, Port Harcourt, Nigeria

Abstract

Edori OS, Edori ES. and Iyama WA

Sediment samples were collected from surface of sediments from parts of the mangrove wetlands of the New Calabar River at points of effluents discharge. The samples were treated according to standard procedures and analyzed for the concentrations of polycyclic aromatic hydrocarbons (PAHs). The results showed the presence of ten PAHs at Iwofe Jetty and Police Post stations and eleven PAHs at the Minipiti station. The summation of the total PAHs in the stations showed 23.440, 33.694 and 51.094 mg/Kg in sediments from Iwofe Jetty, Minipiti and Police Post stations respectively. Pyrene was the most abundant PAH in sediment from Iwofe station, Dibenzo (a,h) anthracene was the most abundant PAH at the Minipiti Station and acenaphthylene was the most abundant PAH at the Police Post Station. The categorization of the PAHs classes showed that the high molecular weight PAHs (HMW PAHS) were more abundant than the low molecular weight (PAHs) in all the stations examined, although, at the Police Post station, the values were very close. The 4-membered rings were more abundant in sediments from Iwofe Jetty station. The 4 and 5-membered rings were more abundant at the Minipiti station and the 2-3 membered rings were dominant at the police Post station. The 6-membered rings were the least abundant or undetected in all the stations. Source and origin diagnosis showed that LMW/ HMW PAHs as pyrogenic in all the stations, An/(An+Phe) ratio revealed pyrogenic sources of PAHs, Fl/(Fl+Pyr) analysis in all the stations indicated petrogenic origin of PAHs, BaA/ (BaA+Chr) evaluation in all the stations revealed pyrogenic sources of PAHs. The mixed sources of PAHs in the wetlands drainage discharge points calls for concern and therefore, efforts should be geared to identify the points at which they were introduced into the effluents and be adequately controlled to prevent harm to the environment.

PDF