The wet season mean concentration of heavy metals were higher than the dry season. Concentration data were processed using Pearson correlation matrix to identify the inter-relationships between physicochemical parameters as well as the sources of heavy metals. The results showed that salinity, pH and temperature among others played a significant role in the adsorption/desorption and dissolution of heavy metals in the surface water. The Enrichment factor (EF) calculated during the wet season in surface water ranged from 0.2 to 2.9 while the EF calculated during the dry season ranged from 0.2 to 1.9. During wet season, Cd, Cu, Fe, Pb and Zn showed minor surface enrichments while Cr and Ni showed no enrichment. During dry season, Cd, Fe and Zn were moderately enriched in surface water while Cr, Cu, Pb and Ni were not enriched. Surface enrichment was attributed to atmospheric deposition, released of sediment bound metals to the surface, dissolution/erosion of coastal sediments as well as anthropogenic input. The computed degree of contamination indicated that the river system was moderately contaminated during dry season but highly contaminated during wet season. The implication is that during flooding which is consequent upon climate change, there will be higher degree of contamination of Qua Iboe River estuary and adjoining creeks.

No abstract

Four recent sediment cores (0-30 cm long) from Afam (AF), Mangrove (MG), Estuary (ES) and illegal Petroleum refinery (PT) sites of the Imo River, Southeastern Nigeria were analyzed to characterize the sources and distribution of organic matter (OM), as well as examine their historical trends of deposition and assess human-induced changes in the last ca. 5 decades using biomarker approach. Radionuclides 210Pb and 137Cs were used to assign approximate dates to each section of the cores. Evaluation of proxy parameters such as carbon preference index (CPI, 2.01 - 2.19), carbon number maximum (Cmax, 29, 31) and atomic C/N (16.51-31.32) for the most recent top layers (0-5 cm) revealed greater wash-in of land-derived organic matter (OM), attributable to the recent rise in water height. The bottom layer (PT1, 25-30 cm,) of the PT core deposited ca. 1964-1972 exhibited a CPI of 0.97 and pristane/phytane (Pr/Ph, 3.75), suggesting that oil bunkering/illegal refinery activity had begun in the region ca. 8 years after the first commercial discovery of oil in Nigeria in 1956. The occurrence in high abundance of heptadecane in the middle layer (ES4, 10-15 cm) of the ES almost corresponded with the period of eutrophication that blocked the waterway in the late 1980s. Measurement of a marked unresolved complex mixture at the near-top layer (AF5, 5-10 cm) of the AF indicated that the heaviest contamination by petroleum hydrocarbons occurred at ca. 1997-2005. This time frame coincided with the period of intensive bunkering and oil pipeline vandalism by Niger Delta militant groups.

No abstract

No abstract