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The efficacy of the lesser duckweed, Lemna aequinoctialis (Welw.), to remediate varying concentrations of cadmium, chromium, lead, and vanadium from an organo-metallic contaminated media was tested in artificial surface wetland mesocosm experiment. A 100 g of fresh-weight duckweed was introduced into each of the mesocosm, except for the control setup and monitored for 120 days while the metals removal rate was quantified using an atomic absorption spectrometer. A time-dependent and partial sorption of metals was observed with the highest removal rate recorded for cadmium (71.96%), followed by lead (69.23%), vanadium (55.22%), and chromium (41.64%). The uptake and bioaccumulation of metals were reflected in the increased plant biomass (p < 0.05, F = 97.12) and relative growth rate (p < 0.05, F = 1214.35) in duckweed. A coefficient (r2) of 0.951, 0.919, 0.970, and 0.967 was recorded for cadmium, chromium, lead, and vanadium respectively, indicating that the remediation of metals followed the first-order kinetic rate model. This study highlights the efficacy of the lesser duckweed to preferentially remediate metals in an organo-metallic complex medium for potential wastewater treatment in the petrochemical industry.

Appling ecological or nature-based solutions for the treatment of complex wastewater from the petrochemical industry in Africa remains a challenge due to the paucity of evidence-based science to support the implementation that is acceptable to regulators and the industry. Although laboratory and field-based demonstration of phytoremediation studies has shown the potential of macrophytes for the treatment of organic and inorganic pollutants, studies on the application of duckweed for complex organo-metallic wastewater treatment for heavy metals are few. This study demonstrates the efficacy of the lesser duckweed, Lemna aequinoctialis in the sorption of cadmium, chromium, lead, and vanadium from an organo-metallic complex with potential application in the petrochemical industry.

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The African Niger Delta is among the world's most important wetlands in which the ecological effects of intensive oil exploitation and global change are not well documented. We characterized the seasonal dynamics and pollution with total-petroleum-hydrocarbons (TPHs), heavy-metals (HMs) and nutrient-loads in relation to climate-driven variables. High TPH concentrations up to 889 mg/L and HMs up to 13.119 mg/L were found in water samples, with pronounced spatio-temporal variation throughout the year. HM pollution index and contamination factor indicate serious ecological and human health hazards, especially for Cd, Cu, Hg, and Ni. Significant differences in TPHs/HMs were observed between sites and seasons, with correlations between TPHs-HMs, and climate-variables and TPHs-HMs. Nutrient levels, turbidity, salinity, temperature, and SO42- were high and interlinked with the variability of TPHs/HMs being greatest during wet season. These findings suggest an urgent need for improved pollution control in the Niger Delta taking into account the observed spatio-temporal variation and the exacerbation of effects in light of climate change. Given the high levels of contamination, further assessments of exposure effects and bioaccumulation in biota should include future climate change scenarios and effects on humans who intensively depend on the system for drinking water, food supply and livelihood.

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Background: This study evaluated the potential protective effects of Zn and Se in the cerebellum and cerebral cortex, two fundamentally important brain regions, in albino rats that were exposed to heavy metals mixture (Al, Pb, Hg and Mn). Methods: Animals were divided into five groups of seven animals per group with following patterns of exposure, controls group 1 were orally treated with deionized water for 60 days; group 2 was exposed to heavy metal mixture (HMM) with following concentrations (20 mg·kg-1 of Pb body weight; 0.40 mg·kg-1 of Hg; 0.56 mg·kg-1 of Mn; and 35 mg·kg-1; of Al), while groups 3,4 and 5 were exposed to HMM and orally co-treated with zinc chloride (ZnCl2; 0.80 mg/kg), sodium selenite (Na2SeO3;1.50 mg/kg) and zinc chloride plus sodium selenite (ZnCl0.2 + Na2SeO3) respectively. Results: Exposure to HMM depressed cellular antioxidant apparatus, induced generation of lipid peroxidation markers (Malondialdehyde and NO), downregulated expression of transcription factors (Nrf2, and NF-kB) and upregulated Caspase 3 levels. HMM potentiated acetylcholinesterase activity and induced moderate histopathological alterations. Nevertheless, Zn, Se and in particular Zn + Se had recovering effects on all mentioned hazardous effects produced by HMM exposure in the cerebral cortex and cerebellum. Conclusions: Selenium and zinc exert neuroprotection via Nrf2/NF-kB signaling pathways against quaternary heavy metal mixture-induced impairments in albino Sprague Dawley rats.

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Surface water and sediment from Bonny Estuary, Nigeria, were assessed to determine the nutrient dynamics. Nutrients (nitrates, phosphates, and total organic carbon (TOC)) and some physicochemical parameters of water samples are collected from three sampling stations along the Bonny Estuary during wet seasons (April 2017, 2018, and 2019) and dry seasons (November 2017, 2018, and 2019). Physicochemical parameters analyses were conducted in situ using Horiba water checker (Model U-10). Surface water nitrate and phosphate were analysed by APHA 4500-NO3-B Colorimetric method, while sediment nitrates and phosphate by Chemical Analysis for Ecological Matter CAEM/APHA 4500-NO3-E Colorimetric method and TOC by CAEM-Wet-Oxidation Titration method. There was no significant seasonal variation in pH, temperature, dissolved oxygen, biological oxygen demand, conductivity, and turbidity nor across the sampling stations. TDS values showed significant seasonal variation with higher values in the wet seasons. Surface water nitrate and phosphate had higher concentrations in wet seasons though within recommended limits. Conversely, nitrate, phosphate, and TOC in the sediments were quite high, with higher values in wet seasons, especially the downstream of the estuary. The high levels of nutrients in the sediments as opposed to surface water could be a result of rapid deposition of nutrients which could lead to possible nutrient enrichment of the sediment. Nutrient levels in the sediment have increased fourfold over the study period. This suggests an influx of nutrients into the estuary, due to human activities. Nutrient enrichment could result in deterioration in aquatic water quality and pose a threat to the ecology of the estuary.

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Solid mineral mining activities have contributed to the distribution and uptake of radionuclides. This has increased the active concentration of naturally occurring radioactive materials NORMs in different environmental media with increased human health risks. This systematic review was aimed at assessing data on active concentration of naturally occurring radioactive materials in mining sites in Nigeria. Articles available on recognized data bases such as Google scholar, PubMed, Cochrane Library and Science Direct were used. Thirty-two studies were used for this systematic review after meeting the inclusion criteria. Reports of studies according to Geopolitical zones revealed 0% North-east, 4% for Southeast, 8% for South-South, 16% in North-West, 20% in South-West, and 52% from North-Central Nigeria. 50%, 45.2%, 50%, and 38.5% of included studies reported elevated active concentration of 232Th, 40K, 238U and 226Ra in soil above world regulatory standards of the ICRP, UNSCEAR and IAEA. Gross-alpha and gross-beta activity concentrations reference dose level (RDL) were exceeded in 83.3% and 80% of studies respectively with the highest values recorded in water 10.12Bq/l, and 14.63Bq/l from an artisanal gold mine in North-West Nigeria. These data agree with reports from other African countries, but lower than reports from China and India. NORMs may be of public health concerns notwithstanding the lean data from clinical and epidemiological studies in Nigeria. This study recommends a One Health approach on the radiological implications of mining sites in Nigeria.

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There exists a visible evidence of linkage between pollutant exposure and nutritional deficiency in many organisms. The aim of the present study was to analyze the proximate composition of juvenile African catfish (Clarias gariepinus) exposed to polydimethylsiloxane (antifoam) for 56 days using a renewal bioassay. The moisture, crude protein, ash, and fat content of the fish samples were analyzed using standard methods. Antifoam concentrations at 0.0mg/L, 63.96mg/L, 127.9mg/L, 255.82mg/L, and 511.64mg/L were used for the sublethal exposure after which the proximate composition was analyzed. The water quality variables including dissolved oxygen, conductivity, and total dissolved solids varied as the concentration increased. The moisture and lipid contents were highest at 511.64mg/L concentration while the control(0.0mg/L) had the highest percentage composition of ash, protein, carbohydrate, and fiber contents which were normal values. The differences in proximate values were slightly significant at P>0.05 among the different concentrations. The findings in this study may be an indication that antifoam can significantly affect some water quality variables and proximate composition, while also portraying the risk associated with the consumption of such exposed fish.

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Polycyclic aromatic compounds (PACs) pollution has been the focus of environmental research, mostly due to their mutagenicity, carcinogenicity, teratogenicity and genotoxicity. Concentrations of polycyclic aromatic hydrocarbons (PAHs) and the nitrogen-containing analogues (N-PAHs) (which tend to accumulate in sediments rather than water) was measured in 2 cm intervals segments from Bonny Estuary, Niger Delta using GC-MS. Data showed that PAHs/N-PAHs levels ranged from 8699 to 22,528 µg/kg and 503-2020 µg/kg, respectively. Furthermore, the data revealed that Æ©PAHs level in the estuarine segments was > 45% higher than DPR/EGASPIN intervention limit. This gives insight on PAHs/N-PAHs contamination in the oil rich region.

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Chemical-surveys of sediments are source of information about historical-pollution in aquatic-ecosystems, because ecological/human-health risks may arise from polycyclic-aromatic-hydrocarbons (PAHs) and nitrogen-PAHs presence in aquatic-environments, particularly sediments, where they partition. Despite this, sediment-PAHs/N-PAHs have not been reported in the Niger Delta. This study investigated vertical-profiles of PAHs/N-PAHs in 2 cm-intervals-segments from Bonny Estuary, Niger Delta. Analysis showed that Æ©PAHs/Æ©N-PAHs in segments ranged from 8699 to 22,528 µg/kg and 503 to 2020 µg/kg, respectively. Abundant-PAH/N-PAH are 2,6-dimethyl-naphthalene and benzo[a]acridine. PAHs/N-PAHs in the samples appeared to be from petrogenic and pyrogenic-sources. Petrogenic-PAHs/N-PAHs were predominated by 2-, 3-rings, alkylated-substituents, while, pyrogenic-PAHs/N-PAHs were dominated by 4-, 5-, 6-rings. Surface-sediments were dominated by petrogenic-PAHs/N-PAHs while, deeper-cores were heavily-contaminated with pyrogenic-PAHs/N-PAHs. Æ©PAHs exceeded the ISQGs and PELs of CSQGs. Æ©-quinoline/Æ©-acridine exceeded the guidelines for protection of aquatic-life. Furthermore, there are concerns over toxic-ratios >70% in the estuary. Such surveys may be helpful in future sediment-management-decisions for contaminated-systems and long-term-monitoring of sediments to assess remediation/recovery. CAPSULE: Distinct sources of PAHs and N-PAHs exist in the Niger Delta ecosystem and, there are concerns over toxic ratios >70% in the oil rich region and the potential for adverse biological effects.

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The potentials of the invasive duckweed species, Lemna paucicostata to remove pollutants from aquatic environment was tested in a constructed wetlands as an ecological based system for the phytoremediation of petroleum hydrocarbons in crude oil-contaminated waters within 120 days. Total petroleum hydrocarbons in wetlands and tissues of duckweed were analyzed using gas chromatography with flame ionization detector following established methods while the experimental data were subjected to the first-order kinetic rate model to understand the remediation rate of duckweed in wetlands. L. paucicostata effected a significant (F = 253.405, P < 0.05) removal of hydrocarbons from wetlands reaching 97.91% after 120 days. Assessment on the transport and fate of hydrocarbons in duckweed indicated that L. paucicostata bioaccumulated less than 1% and significantly biodegraded 97.74% of hydrocarbons in wetlands at the end of the study. The experimental data reasonably fitted (r2 = 0.938) into the first-order kinetic rate model. From the result of the study, it is reasonable to infer that L. paucicostata is an effective aquatic macrophyte for the removal of petroleum hydrocarbons in moderately polluted waters.

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Over the past 50 years, different strategies have been developed for the remediation of polluted air, land and water. Driven by public opinion and regulatory bottlenecks, ecological based strategies are preferable than conventional methods in the treatments of chemical effluents. Ecological systems with the application of microbes, fungi, earthworms, plants, enzymes, electrode and nanoparticles have been applied to varying degrees in different media for the remediation of various categories of pollutants. Aquatic macrophytes have been used extensively for the remediation of pollutants in wastewater effluents and aquatic environment over the past 30 years with the common duckweed (L. minor) as one of the most effective macrophytes that have been applied for remediation studies. Duckweed has shown strong potentials for the phytoremediation of organic pollutants, heavy metals, agrochemicals, pharmaceuticals and personal care products, radioactive waste, nanomaterials, petroleum hydrocarbons, dyes, toxins, and related pollutants. This review covers the state of duckweed application for the remediation of diverse aquatic pollutants and identifies gaps that are necessary for further studies as we find pragmatic and sound ecological solutions for the remediation of polluted environment for sustainable development.

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Proximate composition and microbiological characteristics of pre-dried Chrysichthys nigrodigitatus and Pseudotolithus typus were studied over a period of 4weeks to determine the health risks associated with delayed consumption. All analyses were conducted using standard microbiological and chemical methods. Results showed a general decline in microbiological safety and nutritive characteristics of both fish species over time, with an observed increase in microbial loads over time. Aspergillus flavus was also present on both species which makes consumption of the fishes hazardous to the health of consumers due to its ability to produce carcinogenic aflatoxins. In order to minimise the health risks to consumers, it is recommended that smoke-dried fishes be consumed with minimal delay and cooked properly before consumption. The findings of this study will prove important in the development of more stringent regulations regarding food safety in Nigeria.

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The toxicity of drilling fluid XP-07 on gills of three life stages (fry, fingerling and post fingerling) of Tilapia guineensis was evaluated in a 96h static bioassay. The mortality rates of the organisms were determined using the same concentrations of XP-07 in all the life stages. At the end of 96h, the gills were examined for histopathological changes. The 96h median lethal concentrations for fry (Fr), fingerlings (F) and post fingerlings (PF) were 5.03, 7.77 and 6.93 percent XP-07 respectively. The median lethal time values decreased as concentration and time of exposure increased. The histopathological studies carried out on gills of T. guineensis showed injuries, which increased progressively with the concentration of the fluid. The fry stage was the most susceptible to the drilling fluid. This states the need for care to be taken in handling drilling fluids in Niger delta, since this area serves as breeding and nursery ground for several fish species.

A toxicidade do líquido de perfuração XP-07, nas brânquias de Tilapia guineensis, foi avaliada por meio de um bioensaio estático de 96h em três estágios da vida do peixe (larva, alevino e juvenil). As taxas de mortalidade do organismo foram avaliadas nas mesmas concentrações de XP-07 para todos os estágios de vida do peixe. As brânquias foram avaliadas ao final de 96 horas, com o objetivo de observarem-se mudanças histopatológicas. A concentração média letal para 96h foi de 5,03; 7,77 e 6,93 por cento para larvas, alevinos e juvenis, respectivamente. O tempo médio letal diminuiu à medida que a concentração e o tempo de exposição aumentaram. Os estudos histopatológicos realizados nas brânquias de T. guineensis indicaram lesões que aumentaram progressivamente com a concentração do fluido. A fase larval é a mais suscetível ao fluido de perfuração. Concluiu-se que é necessário cuidado no manuseio de fluidos de perfuração no Delta do Niger, uma vez que esta é uma área de reprodução e berçário para várias espécies de peixes.