No abstract

Superoxide radical (O2(•-)) is an important reactive oxygen species in seawater. Measurements of its production rates and steady-state concentrations generated by photochemical processes have been a Herculean task over the years. In this study, a probe - 3'6'-(diphenylphosphinyl)fluorescein (PF-1) - was used to trap photochemically generated O2(•-) in seawater, thereby yielding fluorescein. The fluorescein produced was measured by an isocratic fluorescence HPLC at excitation/emission wavelengths of 490/513 nm, respectively. The reaction rate constant of PF-1 with O2(•-) (kPF-1) was pH-dependent: (3.2-23.5) × 10(7) M(-1) s(-1) at pHTOT 7.65-8.50. By applying appropriate equations, both the production rate and the steady-state concentration of O2(•-) generated by photochemical reactions in the seawater were quantified. Under the optimized experimental conditions, fluorescein standards (3-50 nM) exhibited linearity in the seawater by HPLC. The photoformation of fluorescein, due to the reaction of PF-1 with the O2(•-) photochemically produced in the seawater, was linear within the 20 min irradiation. The detection limit of the fluorescein photoformation rate was 0.03 pM s(-1), defined as 3σ of the lowest standard fluorescein concentration per 20 min irradiation. Using this value, the yield of fluorescein, and the fraction of O2(•-) that reacted with PF-1 in the seawater, the detection limit of the O2(•-) photoformation rate was 1.78 pM s(-1). Superoxide measurements using the proposed method were relatively unaffected by the potential interfering species in seawater. Application of the proposed method to ten (10) seawater samples from the Seto Inland Sea, Japan, resulted in measured O2(•-) photoformation rates of 3.1-8.5 nM s(-1), with steady-state concentrations ranging (0.06-0.3) × 10(-10) M. The method is simple, requires no technical sample preparation, and can be used to analyze a large number of samples.

Heavy metals were analysed in Osun River (Nigeria) between 2017 and 2018. Concentrations of the heavy metals were in the increasing order: Fe > Zn > Cu > Mn > Pb > (Ni, Cr) > (Cd, Co). Iron made up 76% of the total heavy metals measured. Activities at Swanlux Farm (a major oil palm farm) seemed to impart on Osun River as the highest Fe concentration (2.55 mg/L) was measured near the farm. In the urban settlement, average zinc concentration was almost double (0.37 mg/L) of that found in the pre-urban area (0.25 mg/L). The pre-urban settlement had lower concentrations of Pb, Zn and Cd, signifying the effects of anthropogenic activities. Cu and Mn were found in a similar trend in the river; Coker village had their highest concentrations. Use of agrochemicals was conceivably the major source of Cu and Mn at the river sampling point as cocoa farms are predominant in the area. Osun River use for agricultural/irrigational purposes should be with continuous monitoring.

The study assessed histopathological alterations in the organs of Oreochromis niloticus (Nile tilapia) and Clarias gariepinus (Catfish) harvested from Dandaru Pond, Ibadan, Nigeria. The histopathological effects were evaluated through biomarkings and heavy metals measurements of the fish organs and tissue. Results showed the kidney with sign of coagulated necrosis of the renal tubules. In the liver, there were hepatocytes which appeared foamy and contained large-sized vacuoles. The gills appeared with some congestion in their capillaries in addition to numerous bluish staining walled-off structures. There was severe thinning of the myocardial fibres in the fish heart. The chambers were moderately congested. The fish organs contained 0.06-0.90 µg/g lead. The Pb concentrations and those of manganese and iron exceeded the WHO permissible limit in fish. It is conclusive that the bioaccumulated heavy metals in the tissue and fish organs consequently impaired their histopathological condition, and thus affect fish health status.

Background The research was carried out to assess the lipid characteristics of oil extracted from the head and gills of Claris macrocephalus and Scomber scombrus. Results The results confirmed the presence of C16:0, C18:0, C18:1, C18:2, C18:3, C22:6 as the major fatty acids. Titus fish head (TFHD) oil had a total saturated fatty acid (TSFA) of 40.804 ± 0.002% of which C16:0 and C18:0 were the most dominant fatty acids present while the total monounsaturated fatty (TMUFA) acids present in the oil was 33.853 ± 0.001%. The total polyunsaturated fatty acid (TPUFA) content of the TFHD oil sample was found to be 25.368 ± 0.002%. The results revealed that the total unsaturated fatty acid (TUFA) present in the TFHD was higher than the TSFA. The results obtained for Titus fish gills (TFGL) oil sample followed the same trend as observed in the head sample. The results showed that the four (4) oil samples contain high level of palmitic acid (C16:0) and stearic acid (C18:0) both of which are saturated fatty acids (SFA). The main MUFA identified was C18:1 (cis-6) and ranged from 14.120 ± 0.004 to 20.418 ± 0.002% for TFHD, TFGL, CFHD, CFGL and oleic acid (C18:1) ranged from 10.297 ± 0.001 to 11.570 ± 0.003% for TFHD, TFGL, CFHD and CFGL. Conclusions Oils of CFHD and TFHD showed higher peroxide values indicating suitability for human consumption.