Abstract:
The chromium pollution in the lower reaches (estuary area) of the Kelani river
was examined by analyzing chromium levels in abiotic (sediment, water) and
biotic (two fish species, Liza dussumieri and Macrones gulio} components of
the aquatic system at 21 longitudinal and cross sectional locations.
The morphology of the sediment of the study area indicated that it was mainly
composed of sand (over 80%) except at a few uppermost points on the right
bank where the predominant component was silt and clay (over 90%). The total
chromium content in the sediment varied between 5 - 103mg/kg with a mean t
value of 22.9:1:27.5mg/kgdepending on sampling location. The accumulation of
chromium in the silt and clay fraction was found to be 6 - 7 times greater than
in the sand fraction. The difference in the distribution of chromium with respect
to sampling locations was significant (p< 0.05) along the banks and across the
river but not along the center of the river.
The chromium concentration of the river water ranged between 10.5-35.6flg/1
with a mean value of 25.9:1:4.18flg/1.The variation in the distribution was
significant (P<0.05) both along the river and across the river. The sediment
chromium showed a significant positive correlation with that of water. About
40 fold emichment of chromium in the river water was observed suggesting.that
the chromium pollution in the Kelani river occurs in the water phase. In
general, physico chemical parameters (pH, salinity, dissolved oxygen,
conductivity) of the river water did not have a significant influence on either
water or sediment chromium.
The bio accumulation of chromium in the same body organs of the two fish
species were similar. However the chromium content in different organs of the
same species were significantly different (P< 0.05) which followed the order,
liver, gill and muscle. A negative trend in chromium bio accumulation with
2
respect to length/weight parameters was noted for all organs of both species.
Significantnegative correlations were observed between gill/ muscle chromium
content and length/ weight for both fish species, Liza dussumieri and Macrones
gulio, except gill chromium content vs weight in M.gulio. However, chromium
content in the body organs did not correlate significantly with that of water and
sediment.
The two fish species captured from the study area appeared to have 120 - 170
fold bio accumulation of chromium in the fish muscle in comparison to that of
the same species captured from unpolluted areas of the Kelani river. However,
these levels are at least 10 times lower than those specified by FAO for
chromium in edible fish. Therefore, those who consume above fish species t
captured from the Kelani estuary do not face health risks related to chromium
at present.