Environmental Engineering Reference
In-Depth Information
Table 1
Percentage recoveries of PAHs from spiked water and sediment samples
Recoveries (%)
PAH standard
Water
Sediment
Retention time (min)
Indene
76
74
5.86
Azulene
67
61
9.53
Dibenzothiophene
74
72
14.23
Anthracene
102
77
14.56
Fluoranthene
68
60
17.79
Pyrene
95
90
18.62
LLE has been successfully applied to a wide range of environmental matrices, such
as surface water, precipitation, sea water and waste water samples
[19]
. Determination
of PAHs in marine samples of Siokolo Fishing Settlement was done using LLE
[23]
and recoveries ranged from 64.78%-91.94%.
SE is recommended by the US Environmental Protection Agency (USEPA) for
the extraction of semi-volatile and non-volatile organics from solid matrices
[8, 21, 22]
.
SE is a standard method and is preferred because it is easily standardized, with high
recoveries when compared to other matrix dependent techniques like microwave
extraction, pressurized liquid extraction and supercritical fluid extraction
[19, 21]
.
PAHs in marine water samples of Siokolo Fishing Settlements were determined
[23]
, and extraction of water sediment samples was based on SE and recoveries
ranged from 90.58%-118%.
PAHs are commonly analyzed by gas chromatography coupled with either mass
spectrometry (GC-MS) or flame ionization detector (GC-FID), or by liquid chro-
matography coupled with mass spectrometry (LC-MS) or UV-diode array detection
(LC-UV-DAD) (19, 24). In principle, GC-FID is simple and more direct for the
determination of PAHs compared to other methods, if a suitable column is used.
The use of capillary column in GC as employed here has brought a high level of
excellent reproducibility, high sensitivity and high resolution of PAHs on routine
basis
[8]
. Thus the use of GC-FID was the method of choice in this study.
The results of recovery experiments by liquid-liquid (LLE) and Soxhlet extrac-
tion (SE) methods with determination by GC-FID, for water and sediment samples
are shown in Table
1
. The recoveries varied between 68%-102% for spiked water
samples and from 60%-90% for spiked sediments. The results were adjudged sat-
isfactory and the methods were therefore used for analysis of environmental water
and sediment samples.
Concentration of PAHs in water samples varied between 0.1-53.5 (mg/L) in river
water samples (Table
2
) and between 22.8-9,870 (mg/kg) in river sediments (Table
3
).
PAHs levels in runoffs varied between 1.0-2,500 (mg/L) (Table
4
) while levels in
runoff sediment ranged from 72.5-34,000 (mg/kg) at the Univen parking lot (Table
5
).
This might be due to high levels of vehicles parked here.
Generally the levels of PAHs in sediments samples are consistently higher than
those in water samples. The higher concentrations in sediments were expected
because of possible accumulation of PAHs on sediments. The sediments could act
