Environmental Engineering Reference
In-Depth Information
Keywords
Crude oil
·
Germination
·
Phytoremediation
·
Soil
1 Introduction
Oil-contaminated soil can damage environment by affecting the plants and micro-
organisms of the soil. The effect of contaminant on microorganisms and plants de-
pends on the concentration and the kind of contamination (Boethling and Alexander
1979
). Heavy crude oil has higher resin and asphaltine than light crude oil. These
compounds do not well biodegrade by microorganisms and plants and remain in soil
for many years (Walker et al.
1975
). On the other hand, some gaseous and volatile
hydrocarbons are higher in light crude oil than those in heavy crude oil. These
compounds are toxic for biological systems of soil. The effect of crude oil and its
components on germination and growth of some plants has been studied (Adam and
Duncan
2002
).
Some plants are able to remediate the organic pollutant from the soil. Phytore-
mediation is the use of plants and their associated microorganisms to remediate
contaminated soil and water. Among the plants, grasses and legumes have higher
potential on removal of oil from contaminated soil (Minai-Tehrani
2008
). The
plant roots stimulate the bacteria in rhizosphere area, which enhance the biodeg-
radation of petroleum hydrocarbons. Legumes are able to fix nitrogen and do not
compete with microorganisms for limited supplies of available nitrogen at oil-
contaminated soils. In this study, the effect of different concentrations of light
crude oil on growth and germination of a legume,
Medicago sativa
(alfalfa), was
studied and the reduction of light crude oil in the soil in the presence of plant was
investigated.
2
Materials and Methods
Soil Analysis
The soil and light crude oil (API = 40) were obtained from Sarkan
zone, near the oil processing factory of Sarkan in the west of Iran. The soil was
dried at room temperature and then sieved through 2 mm mesh. Light crude oil was
added to the dry soil with concentrations of 0, 1, 3, 5, 7 and 10 % (w/w). The soil
and oil were well mixed to make homogenized contaminated soil, and then trans-
ferred to pots each of one L size. Each sample consisted of 800 g of dry soil.
Chemical fertilizers were added to the soil before seeding. Each of the soil
sample was supplied with 75 mg/kg nitrate (NH
4
NO
3
) and 30 mg/kg of phosphate
(KH
2
PO
4
). Twenty seeds of alfalfa were planted in each sample. All vegetated sam-
ples were prepared as three replicates. The control samples for each concentration
were also prepared as three replicates which were without seeds (non-vegetated).
The number of germinations was counted 30 days after planting and indicated as
germination number. The number of leaves was counted 60 days after planting and
