Evaluation of Total Petroleum Hydrocarbon (TPH) in Sediments and Aquatic macrophytes in the River Nun, Amasoma Axises, Niger Delta, Nigeria.
Abstract
The Total Petroleum Hydrocarbon (TPH) in the bottom sediments and aquatic macrophytes of the River Nun at AmasomaAxises was investigated in December, 2017. This was done to establish the existing levels of TPH in the River in order to ascertain the degree of its threat to the environment. Benthic samples were collected close to the shore with the aid of a hand trowel and put in aluminum foils, while macrophyte samples were collected by hand pulling and transported in plastic bags for laboratory analysis. Data were subjected to statistical analysis using the Microsoft Excell® tool pack. Regression analysis was employed in order to determine the correlation between TPH in bottom sediments with that in plant tissues (leaf, stem and root). Analysis of variance was employed at the 95% confidence level to determine the degree of significance in interaction of TPH between sediments and macrophyte tissues and between macrophyte tissues (leaf, stem, and root). Duncan multiple range test was use to compare means. The bioaccumulation factor (BAF) was calculated for TPH in order to estimate the absorption rate of TPH between sediments and plant tissues (leaf, stem and root). Results indicate that TPH were recorded in sediments and plant tissues. TPH concentrations were greater in plant tissues than in sediments. Concentration of TPH showed concentrations indicating that root> stem> leaf inmost stations. The relationships between the TPH attributes indicated strong association between Leaves and stem (r2 = 0.92). Strong negative association was also observed between sediment and stem (r2 = -0.83) while sediment and leaves (r2 = -0.64) had moderate negative relationship. It can be concluded that the River Nun at AmasomaAxises is mildly polluted due to land based activities and therefore there is a need to enact water use regulatory ordinances to protect its ecology. Sediment organisms and plants are vital links to man in the food chain. This may portend danger in the future.
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Introduction
Total petroleum Hydrocarbon (TPH) is a term used for any mixture of hydrocarbons found in crude oil. They are several hundred of these compounds, but not all occur in anyone sample. There are so many different chemicals in crude oil and other chemical products for instance that it is not practical to measure each one separately. Therefore the measurement of TPH becomes most apt, as it gives a definitive picture of the whole.
The contamination of aquatic ecosystems with TPH is a disturbing reality. The majority of TPH entering aquatic environments remain close to sites of deposition, suggesting that lakes, rivers, estuaries and coastal environments near centers of human population are the primary repositories of the aquatic TPH [1]. Discharges from urban catchments may carry with them sediments, nutrients, heavy metals, pesticides, oils and hydrocarbons and solid pollutants such as litter [2]. Also, Industrial discharges also carry significant TPH and thermal load to receiving environments [3]. TPH sources of pollution of the aquatic environment are so diverse that no single source can beheld culpable. Sadly, the accumulation of TPH in an aquatic environment has direct consequences to man and to the ecosystem due to the intrigues of food chain [4]. This is as a result their easy affinity for bottom sediments and plant tissues. This may imply serious health implications from bioaccumulation and bio-magnifications in living organisms.
Therefore the fate of TPH introduced by human activities into aquatic ecosystems have become the subject of widespread concern, since beyond the tolerable limits they become toxic [5, 6].The measurement of TPH in the aquatic ecosystem is a universally accepted practice for determining the pollution status and integrity of water bodies.
The River Nun at the Amasoma axis is afresh water body and an appendage that lies along the 160km flow course of the River from its flow origins of the River Niger. It is the main live-wire of the Amasoma people as it provides their source for fish and a transportation route for trade and commerce for goods coming and leaving this ancient city settlement. Like every threatened water body that has lots of heavy human activities and marine transport, the River is prone to TPH pollution. Therefore there is an acute need to investigate the TPH levels in bottom sediments and aquatic macrophytes of the River. Bottom sediment pollution is considered by many regulatory agencies to be one of the largest risks to the aquatic environment, since many aquatic organisms spend the major part of their life cycle living on or in sediments [7]. This study will reveal the existing levels of TPH in the River in order to ascertain the degree of its threat to human health and the environment
Conclusion
Despite the presence of potential anthropogenic sources of TPH in the river shores at the study stations, this study found only insignificantly low concentrations of TPH in sediment and plant tissues. This is in disagreement with the findings of previous works done on similar water bodies with human inputs[8]. However, the presence of TPH may be due to their easy affinity for bottom sediments and plant tissues. Also the presence of TPH in plant tissues was observed to be correlated to the amounts of these elements in bottom sediments because plants ingest or absorb them from sediments.[9] noted that the extent of bioaccumulation in biota is dependent on the chemical effect of the metal or pollutant, its tendency to bind to particular materials and or the lipid content and composition of the biological tissues. In a similar study [10] also observed differential rate of adsorption of heavy metals in leaf, stem, and root of bitter leaf and okra plants in the Niger Delta exposed to metal polluted soils.
The study reveal a spatial increasing trend in TPH in both sediments and plant tissues from station to station (station 1> station 2> station 3). One reason for this may be the fact that station 1 is a Jetty and landing terminal for all boats transport from the city to the hinterlands of southern-Ijaw and beyond. As such lots of petroleum products are landed on the jetty both for fueling and domestic use. This is result is in disagreement with the findings of [11] who experienced a trendless spatial variation of TPH in study stations with evidently different potential of TPH generation. However, it may be difficult to predict and identify which station and sources may produce more TPH. [12] put it aptly by saying that the exact identification of TPH sources to the Niger Delta soils is not feasible due to the variety of processes contributing to the formation and preservation of TPH in soils of this area.
Also, in all stations throughout the study the result indicate that the absorption of TPH by macrophyte tissues show that root>stem>leaf. The lower concentration of TPH in leaf samples may have been caused due to phytodegradation or phyto transformation of petroleum hydrocarbons which was subjected the contaminants to the bioremedial processes occurring within the areal part of plant itself[8].Hydrophobic chemicals are generally not sufficiently soluble in water or are bound so strongly to the surface of the roots and may not pass beyond the root’s surface due to the high proportion of lipids present at the surface, so cannot be easily translocated into the plant [13]
The mean level of Bioaccumulation factor (BAF) of TPH in plant samples was found to be 1 and lower than 1.The lower BAF value of leaf samples shows uptake of hydrophilic compound of petroleum hydrocarbons by root and translocation to the leaf through vascular system. In general, chemicals that are highly water soluble are not sufficiently sorbed to roots or actively transported through plant membranes [14].
Finally, these results show the mean value of TPH in macrophyte samples and sediments does not exceeded the average global permissible limit in soil (1000mg/l) and also lower than the phytotoxic level in the plants (1000-12000 mg/l)[8]. It can be concluded that the River Nun at Amasoma Axis is only mildly polluted but there is reason to still monitor its water characteristic and promulgate land use ordinances to protect its fishery and entire ecosystem
