HYDROCARBON DEGRADATION AND ACCUMULATION BY SANSEVIERIALIBERICA GEROME ANDLABROY POLLUTED WITH CRUDE OIL

ABSTRACT

The  capability  ofSansevierialiberica   to  withstand  crude  oil  pollution,  degrade   and/or accumulate the contaminant was investigated using 0.3, 1.3 and 6.3% v/w concentrations of crude oil to pollute soil vegetated with the stem cuttings of the plant. These treatments were repeated in unvegetated soils and the control had no crude oil pollution. The experiment was carried out in 3 replicates in a completely randomized design. Total Petroleum Hydrocarbons (TPH) were determined for all soil samples (vegetated and unvegetated)as well as the leaves, stem and roots using Gas Liquid  Chromatography  (GLC). Vegetative parameters  namely; number of leaves, leaf area,  plant height and stem circumference were determined for both control and polluted  plants before and after pollution. The results showed that percentage TPH degraded in  the vegetated soil was 95.8, 88.5 and 68.1% for 0.3, 1.3 and 6.3% v/w concentrations,  respectively.  S liberica alone degraded 0.87, 2.92 and 2.29% for the same treatments. Percentage accumulations of 0.3% v/w crude oil pollution for the leaf, stem and root were 0.002, 0.036 and 0.209%, respectively, those of 1.3% v/w were 0.004, 0.067 and

0.315%, respectively while those of 6.3% v/w were 0.008, 0.085 and 0.43%,  respectively. Means for the vegetative parameters for the plant parts showed that there were significant (P<

0.05) differences in some vegetative parameters after contamination with crude oil. Therefore there was phytoremediation and accumulation of hydrocarbons by S. liberica.

CHAPTER ONE

1.0    INTRODUCTION

1.1   Crude oil/or hydrocarbon pollution

Crude oil is a crucial  energy resource  and vital industrial  raw material.  With  increasing industrial production, oil pollution has become a serious worldwide environmental problem, especially at the oil mining stage in the field (Zhu et al., 2013). Large-scale crude oil spills on soil,  leakages  from  pipelines,  underground  and surface  fuel storage  tanks,  indiscriminate spills and careless disposal and mismanagement of wastes and other petroleum by-products constitute the major sources of petroleum contamination in our environment. Oil spillage on soil has many detrimental effects on the composition, structure and functioning of terrestrial ecosystems,  including  loss of  biodiversity (Osuji et al., 2004). Soil contamination  arising from oil spills is one of the most limiting factors to soil fertility. It affects growth of plants thereby causing negative impacts on food productivity (Onwurahet al., 2007).

High levels of petroleum hydrocarbons  which include alkanes (paraffin), alkenes  (olefins) and various aromatic hydrocarbons are found in crude oil (Oforkaet al., 2012). According to a report by NNPC (2004), the Nigerian crude oil is characterized by high concentrations of aromatics (40%) and polars (resins and asphaltenes, 47%). Oil pollutants can get transferred via food chains and eventually cause adverse effect on human health. In addition, residual oil hydrocarbons can persist in the soil for decades and have chronic effect on ecosystems and human beings (Culbertson et al., 2008).The latter has attracted increasing attention because of the carcinogenic, mutagenic and toxic effects (Imeh and Sunday, 2012).

Environmental  remediation  deals  with  the  removal  of  pollutants  or  contaminants  from environmental media such as soil, groundwater, sediments or surface water (Zhu et al., 2004). Phytoremediation  (from  Ancient  Greek  (phyto),  meaning  “plant”,  and  Latin  remedium, meaning “restoring balance”)  describes the treatment of  environmental problems by using plants without the need to excavate the contaminant  material and dispose of it elsewhere (Ruiet al., 2012).

Total petroleum hydrocarbon (TPH) is defined as the measurable amount of petroleum-based hydrocarbon in an environmental medium. It is thus, dependent on analysis of the medium in which it is found (Adesodun and Mbagwu, 2007). Some chemicals that may be found in TPH are hexane, jet fuels, mineral oils, benzene, toluene, xylenes, naphthalene and fluorine as well as other petroleum products and gasoline components. However, it is likely that samples of TPH will contain only some, or a mixture of these chemicals (USEPA, 2012).

Gas liquid chromatography (GLC) is one of the most powerful, popular, unique and versatile analytical  techniques  used  for  the  separation,  identification  and   quantitative  assay  of compounds  in  the  vapour  state.  The  popularity  of  GLC  is  absolutely  centred  on  high selectivity, sensitivity, high resolution combined with good accuracy and precision in a wide dynamic concentration range (Sjaaket al., 2009).

1.2Sansevierialiberica Gerome and Labroy

The genus  Sansevieria   pronounced   (san-se-vi-ee’-ri-ah)   –  is  a  member  of   theFamily

Asparagaceae  and is popularly called Snake-plant,  Mother-in-Law’s  tongue or  Bowstring-

hemp. The genus was named by Thunberg after the Prince of Sanseviero who was born in Naples in 1710.Sansevieria tops the list as the most tolerant of all decorative plants that can survive  the most unsuitable  growing  conditions,  abuse  and neglect  a  plant could receive (Chahinian, 2005).

1.3 Scientific classification

Kingdom: Plantae

Division: Magnoliophyta

Class: Liliopsida Order: Asparagales Family: Asparagaceae Genus: Sansevieria

Species: Sansevierialiberica

(Source: Aigbokhan, 2014)

1.4 Description of the plant

Sansevierialibericais an evergreen perennial plant forming dense stands, spreading by way of its creeping rhizome, which is sometimes above ground, sometimes underground with fibrous roots. Its stiff leaves grow vertically from a basal rosette. Mature leaves are dark green with light grey-green cross-banding and usually range between 70–90 centimetres (28–35″) long and 5–6 centimetres (2.0–2.4″) wide. It bears milk coloured  flowers that are bisexual and pollinated by moths. Sansevierialiberica  flowers from the month of March to June in West Africa. Fruits are green when unripe and turn orange in colour when ripe.Both flowering and fruiting are erratic and few seeds are produced. The raceme of Sansevieria is derived from the

apical meristem and a flowered plant will no longer produce new leaves but continues  to grow by producing plantlets via its rhizomes or stolons (Chahinian, 2005).

1.5 Cultivation ofSansevierialiberica

It can be propagated by leaf cutting; whole leaves are cut from the rosette and set aside for several days to allow the cut to dry. At this point the leaf will be inserted cut side down into moist porous potting medium to root. Over time the leaf will produce roots and a stolon from the cut surface which will bear a new plant at its tip. The rhizome can also be cut and sown. It is tolerant of salt and saline soils. It can tolerate drought and  should  not be over watered (Chahinian, 2005).

1.6Uses

Like some other members of its genus, S. liberica yields bowstring hemp, a strong plant fibre once used to make bowstrings  and can be used in place of rubber (Osabohien  and Egbo,

2008). It is now used predominantly as an ornamental plant, outdoors in warmer  climates, and indoors as a houseplant  in cooler climates. It is popular as a houseplant  because it is tolerant  of low light levels and irregular watering.  A study by National  Aeronautics  and Space Administration (NASA) found that it is one of the best plants for improving indoor air quality by passively absorbing toxins such as nitrogen oxides and formaldehyde (Wolvertonet al., 1989).

1.7Aim and objectives of the research work

The aim and objectives of this work are:

•          to assess the capability ofSansevierialiberica  to degrade petroleum hydrocarbons in crude oil contaminated soil.

•          to       determine       the       quantity       of       total       petroleum       hydrocarbons

(TPH)Sansevierialibericacan accumulate.

•          to establish the levels of crude oil contamination the plant can tolerate.

.to ascertain the effect of crude oil pollution on some vegetative parameters of S.  liberica.

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