Environmental Engineering Reference
In-Depth Information
Studies and Transactions on Pollution
Assessment of the Lagos Lagoon System,
Nigeria
Babajide Alo, Kehinde Olayinka, Aderonke Oyeyiola, Temilola Oluseyi,
Rose Alani, and Akeem Abayomi
Abstract
The Lagos Lagoon system is a brackish coastal lagoon—the largest in the West African coast
with a large series of estuaries—located between longitude 3
o
23
0
and 3
o
40
0
E and between
latitude 6
o
27
0
and 6
o
48
0
N. It is a shallow expanse of water (0.3-3 m deep), 50 km long and
3-13 km wide and separated from the Atlantic Ocean by a narrow strip of barrier bar
complex. This report is on the levels of pollution and nutrients status of the Lagos Lagoon
system including physicochemical properties, pesticides organochlorines (OC), polyaromatic
hydrocarbons (PAHs), heavy metal species and nutrients observed between 2002 and 2008.
Watersheds of the highways on the lagoon had higher concentrations of nutrients (phosphorus
and nitrates) relative to other locations on the Lagoon. The western part of the Lagoon was
found to have higher concentrations of Cd, Cu, Pb and Zn than the other points. Lagos
Lagoon and the adjoining creeks show high anthropogenic input of PAHs and other persistent
organic pollutants (POPs). The major hydrocarbon index in most samples was at C
29
,C
31
and
C
27
, indicating vascular plants sources. Mean PBT levels in water and in sediment increased
with time between 2004 and 2007. PBT distribution in the lagoon followed the pattern,
sediment [ biota [ water, though some exceptions occurred where the biota bioaccumulated
more PBTs than are found in both sediment and water. The Lagoon biota bioaccumulated
organochlorine pesticides above allowable limits and thus pose a high risk to human health.
The levels of some pollutants in the Lagoon have negatively impacted on the environmental
quality which has indirectly affected the social and economic activities of the dependants and
this requires improved management strategies to ameliorate. Indeed with the high population
that the estuary/lagoon system supports, consideration for its designation as an international
waterbody and its concomitant attention is now paramount.
Keywords
Lagos Lagoon
Heavy metals
Pollution
Nutrients
Polyaromatic hydrocarbons
Organochlorine pesticides
Polychlorinated biphenyls
Hydrocarbons
Introduction
Urbanization and industrialization have led to the release of
a variety of pollutants from both point and diffuse sources,
and has placed considerable pressure on the aquatic
resource. This is of particular concern in developing
countries where expansion of urban area may be relatively
65
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