Land use is one major factor that affects river water quality which is related to anthropogenic activities. Studies have shown that abandoned boats on watershed, petroleum and untreated wastewater from abattoirs can lead to anthropogenic pollution in surface waters. This study, therefore, was designed to assess spatial and temporal variation of selected heavy metals and level of pollution in Woji Creek. The study was carried out in the months of August, September and October 2018. Water samples were collected from five stations along the creek over a 3.2 km stretch. Water was collected to be analysed for heavy metals (Nickel, Cadmium, Copper, Lead and Iron). Results were subjected to ANOVA and heavy metal pollution index (HPI) was calculated using aquatic toxicity reference values (TRV) as threshold values. Heavy metal dominance in Woji was in the order of Pb>Ni>Fe>Cd>Cu. In the river, Ni had mean values ranging from 0.379±0.259 mg l −1 in August to 0.545±0.369 in October, while Pb with the highest concentration had mean values ranging from 0.229±0.333 mg l −1 in October to 1.534±0.103 mg l −1 in September. Concentrations of metals analysed were high than the TRV. Temporal analysis of HPI calculated for the study was above the critical heavy metal pollution index (100) (August=329.358, September=361.796, October=112.715). A correlation was observed between heavy metals analysed during the study. Spatial analysis of HPI showed higher pollution level at Station 3 with the highest anthropogenic activity along the creek. Cu showed a negative correlation to other metals analysed. Sources of pollution on this creek was identified to be both natural and majorly anthropogenic sources. This study, therefore, points out the need for proper environmental management as regards commercial activities around the waterways.

This study was designed to assess total petroleum hydrocarbon (THP) concentrations in the surface water and sediment sampled from Woji Creek and to assess potential ecological and human health risk due to petroleum hydrocarbons along the creek. Physicochemical parameters [pH, temperature (T), electrical conductivity (EC), dissolved oxygen (DO), total dissolved solids (TDS)] were in-situ measured from sediment and surface water; hydrological parameters (width, depth and volume) were used to calculate the flow rate (discharge) at different stations of the creek. Trend of TPH in the surface water samples along the creek were as follows: St4 (3.639 AE 1.121 mg/L) > St3 (2.449 AE 0.623 mg/L) > St1 (1.457 AE 0.244 mg/L) > St2 (1.069 AE 0.228 mg/L) > St5 (1.010 AE 0.120 mg/L) Trend of TPH concentration across the creek was as follows: St1 -8.758 AE 0.697 mg/kg > St3 -7.675 AE 0.541 mg/kg > St5 -5.515 AE 0.401 mg/kg > St4 -5.075 AE 0.363 mg/kg > St2 -3.162 AE 0.307 mg/kg. Diagnostic indices indicate that the hydrocarbon in the creek was from petrogenic source. Estimation of ecological risk indicated risk in the surface water but not in the sediment. However, human health risk assessment indicated no risk due to human ingestion of the sediment or surface water.

This is the first study related to PAHs distribution in the Woji Creek (Nigeria), that points out potential contaminant sources. The study involved sampling of water and sediment from five stations along the creek monthly (from August to October in 2018). Samples collected were analysed for the concentration of sixteen Polycyclic Aromatic Hydrocarbons (PAHs) using an Agilent 7890B Gas Chromatograph (GC-MS). Eleven (11) PAHs were identified in the water samples with five (5) below detectable limits (Naphthalene, Phenanthrene, Pyrene, Indeno (1, 2, 3, -cd) pyrene and Benzo [(g), (h), (i)] perylene). Results from the surface water showed that in the month of September, the concentration ranged from 6.029 ppm in S4 to 28.331 ppm in S5. October recorded a PAHs concentration ranging between 6.094 ppm at S1 and 29.257 ppm at S5. In the sediment highest concentration of PAHs was recorded in S5; 1809.08 ppm in August, 1810.05 ppm in September and 1821.5 ppm in October. The concentrations of PAHs in sediment were significantly greater than those in the water. In both sediment and water samples, the highest concentrations of total PAHs were recorded in station 5 and the lowest in station 4. The composition of PAH in water identified the dominance of 2 and 3 rings (Low Molecular Weight (LMW) PAHs) over 4, 5 and 6 rings (High Molecular Weight (HMW) PAHs). In the sediment samples analysed, LMW PAHs (2-3 rings) made up about 30% of the composition, while HMW PAHs (4-6 rings) made up about 70% of PAHs member groups. Cross plots showed that the PAHs could have come from petroleum and combustion.

Small waterbodies have potentially high greenhouse gas emissions relative to their small footprint on the landscape, although there is high uncertainty in model estimates. Scaling their carbon dioxide (CO2) and methane (CH4) exchange with the atmosphere remains challenging due to an incomplete understanding and characterization of spatial and temporal variability in CO2 and CH4. Here, we measured partial pressures of CO2 (pCO2) and CH4 (pCH4) across 30 ponds and shallow lakes during summer in temperate regions of Europe and North America. We sampled each waterbody in three locations at three times during the growing season, and tested which physical, chemical, and biological characteristics related to the means and variability of pCO2 and pCH4 in space and time. Summer means of pCO2 and pCH4 were inversely related to waterbody size and positively related to floating vegetative cover; pCO2 was also positively related to dissolved phosphorus. Temporal variability in partial pressure in both gases weas greater than spatial variability. Although sampling on a single date was likely to misestimate mean seasonal pCO2 by up to 26%, mean seasonal pCH4 could be misestimated by up to 64.5%. Shallower systems displayed the most temporal variability in pCH4 and waterbodies with more vegetation cover had lower temporal variability. Inland waters remain one of the most uncertain components of the global carbon budget; understanding spatial and temporal variability will ultimately help us to constrain our estimates and inform research priorities.

The present study investigated the risk associated with concentrations of lead and cadmium in tissues (gills, livers and muscles) of Blackchin tilapia (Sarotherodon melanotheron) from upstream and downstream regions of an intertidal creek in Rivers State, Nigeria. The trend of Cd in fish tissues and water was as follows: muscle > liver > gills > water. The concentration of Cd in fish gills was higher in downstream fish when compared to upstream fish. The mean Cdmg kg −1 in fish gills was 0.048 ± 0.015—upstream and 0.549 ± 0.152—downstream, 0.037 ± 0.030—upstream and 0.769 ± 0.100—downstream, 0.026 ± 0.015—upstream and 0.902 ± 0.118—downstream, and 0.040 ± 0.018—upstream and 0.727 ± 0.157—downstream in December, January, February and March respectively. The trend of Pb in fish tissues and water was as follows: muscle > liver > gills > water. Pb was generally higher in fish sampled downstream when compared to those sampled upstream of the creek. Fish gills in upstream fishes had Pb of 6.324 ± 0.388 mg kg−1, 5.140 ± 1.249 mg kg−1, 5.459 ± 0.471 mg kg−1 and 5.730 ± 0.859 mg kg−1 while downstream fishes had Pb 7.732 ± 0.640 mg kg−1, 9.401 ± 0.711 mg kg−1, 7.575 ± 0.624 mg kg−1 and 7.644 ± 0.637 mg kg−1 in December, January, February and March respectively. Cdfish gills < Food and Agriculture Organization (FAO) maximum permissible limit (MPL), Cdfish muscles and Cdlivers < MPL for FAO, FAO/WHO and WHO. Pbgills upstream and downstream > MPL for FAO, FAO/WHO and WHO. Pb and Cd did not indicate non-carcinogenic risks to human health owing to the consumption of fish up- and downstream. In the present study, fishes sampled upstream showed low cancer risk in adults, however, cancer risk index (CRI) indicated moderate cancer risk in children (male and female). For fishes sampled downstream, CRI indicated low risk for adults and male children, but a moderate risk for female children.

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