Abstract:
This study was carried out to determine the toxicity of Zinc (Zn) and Lead (Pb) spiked
sediment to Chironomus sp. as well as to study the relationship between pore water metal
content and toxicity. This experiment involved the use of two types of sediment spiking
methodology - unrinsed sediment and rinsed sediment. The toxicants used were Zn and
Pb. The chironomids were exposed to spiked sediment of 5 different concentrations
(nominal concentration: Oppm, 3750ppm, 7500ppm, I 5000ppm and 30000ppm). The 96
hour LCso value for Zn in sediment was 870.32mg/L (1
st
replicate) and 147.444mg/L (2
n
d
replicate). For overlying water, the value was 854.92mg/L ( I
st
replicate) and 587.38mg/L
nd
(2
replicate). The 96 hour LC50 value for Pb was 2913.56mg/L (1
st
replicate) and
2285.13mg/L (2
n
d replicate) in sediment. The value in overlying water was 17.925mg/L
t
( I s
replicate) and 22.994mg/L (2
n
d replicate). It was observed that in unrinsed Pb spiked
sediment the overlying water was more toxic than the sediment.
