Ecological and human health risk assessment of total petroleum hydrocarbons in surface water and sediment from Woji Creek in the Niger Delta Estuary of Rivers State, Nigeria

Contamination of groundwater by petroleum hydrocarbons: Impact of fuel stations in residential areas

Anthropogenic factors such as leakages from fuel storage facilities contribute to the release of petroleum hydrocarbons into groundwater. Following the proliferation of fuel stations in residential areas, this research assessed physicochemical parameters, salinity, and levels of total petroleum hydrocarbons (TPH) in groundwater sources within selected residential areas. From the study, mean values of temperature (30.5 °C), pH (5.8), EC (181.5 μs/cm), TDS (90.7 mg/L), and salinity (0.1 ppm) were recorded. The highest mean concentration of TPH (9.5 mg/L) was recorded at location A, while three sampling points (J, L, and M) exhibited 0.0 mg/L. Notably, TPH concentrations exceeding permissible limits were observed at three sampling points (A, B, and R). Strong positive correlations were observed between EC and TDS (r = 0.9), as well as salinity and EC (r = 0.9) and TDS (r = 0.9). Matrix plots demonstrated non-linear relationships, except for TDS and EC, although TPH and temperature exhibited a slightly linear pattern. The distance from USTs to the groundwater sources varied in the area. At location H, this distance (25 m) was measured as the shortest, where the mean TPH concentration was 3.71 mg/L. However, site Q exhibited the longest distance of 535 m, accompanied by a mean TPH concentration of 1.1 mg/L. Though the proximity of USTs to groundwater sources exerted some level of influence on the groundwater system, multiple linear regression, ANOVA, and cluster analysis showed that this did not pose direct and major impacts on the concentrations of TPH. However, approaches are needed to remediate the affected groundwater sources.

Pollution of the Niger Delta with total petroleum hydrocarbons, heavy metals and nutrients in relation to seasonal dynamics

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.

Environmental and health risks assessment of n-alkanes and BTEX in Eze Iyi River at oil spill site in Isuikwuato, Abia State, Nigeria

The environmental and health risks of n-alkanes and benzene, toluene, ethylbenzene, and xylene (BTEX) in Eze-Iyi River at Isuikwuato oil spill site were evaluated. The water samples (60) were collected from upstream and downstream during the dry and rainy seasons. Concentrations of n-alkanes and BTEX were determined using a gas chromatograph coupled with a flame ionization detector. The percentage recovery of 87.3% and 92.0% was obtained for n-alkanes and BTEX in the water sample. The environmental risk analysis for n-alkanes and BTEX showed 80% of the water samples had a ratio greater than 1 indicating environmental risk in the area. Hydrocarbon source identification using biomarkers indicates that the n-alkane (nC16) dominant during the dry and rainy seasons was from anthropogenic/biogenic source, while nC14 and nC17 were from microbial and marine algae biogenic sources, respectively. The benzene levels in 100% (downstream) and 80% (upstream) of samples in the dry season and 40% (upstream) and 100% (downstream) of samples in the rainy season were above the WHO permissible limit of 0.01 mg/L for drinking water. The health risk index of n-alkanes during the dry season for children (upstream) was greater than 1 signifying adverse health risk. Therefore, consumption of water from the river should be discouraged and routine monitoring by regulatory authorities maintained to checkmate the build-up of BTEX and n-alkanes.

Improving cleaner production of human activities to mitigate total petroleum hydrocarbons accumulation in coastal environment

The marine coast is an important ecological transitional boundary but easily suffers from human intervention. Total petroleum hydrocarbons (TPHs) are ubiquitous along the coast. However, the influence of anthropogenic and natural factors on TPHs distribution remains unclear. This study sampled surficial sediment (N = 243) from the coasts of the largest peninsula-Leizhou Peninsula, in Southern China. We found that land-based discharge, sea traffic, and sediment type significantly (p < 0.05) drive the accumulation of TPHs. We observed that TPHs increased by 1.036 μg · g^-1 (exp[α_i] = exp. [0.0355]) of its original value with the addition of one more boat on the wharf. Although the average TPHs were at a moderate level (124.68, ND-1536.14, μg · g^-1) and risk, 'Blue Carbon' ecosystems, i.e., mangroves (224.84, ND - 1441.13, μg · g^-1, p < 0.001) were more severely polluted. Cleaner production policy should be applied to mitigate TPHs discharging trend from coastal areas.

The evaluation of Hudson River sediment as a growth substrate - Microbial activity, PCB-degradation potential and risk assessment

The potential use of growth substrates prepared with an admixture of 10% to 75% Hudson River sediments was evaluated by analysis of changes in microbial activity (measured using Biolog Ecoplates) and molecular markers (presence of degradative tceA1 and bphA genes) as well as potential risks toward humans and the environment (health and environmental risk quotients). The highest microbial activity was found in growth substrate with 25% Hudson River sediments compared to unamended control soil. Significant differences were observed between samples amended with lower (0-10%) and higher (25-75%) proportion of sediment. Microbial activity increased with the proportion of sediment amendment (≥25% sediment); however, this increase in microbial activity was not affected by increasing pollutant concentrations (PCBs, Pb, Cr Ni and Zn) nor decreasing TOC content. The growth substrate amended with Hudson River sediments demonstrated a potential for PCB degradation, as evidenced by the presence of tceA1 and bphA genes responsible, respectively, for reductive dehalogenation and oxidation of a range of aromatic organic compounds including PCBs. An assessment of risk quotients showed that the growth substrates containing lower doses of Hudson River sediments (10-50%) meet the international requirements for use in agriculture/horticulture for the production of non-food crops. Nevertheless, due to the elevated content of some toxic metals and PCBs, the growth substrate prepared with the highest proportion of sediments (75%) was not suitable for agricultural/horticultural use.