Title of Thesis
Application Of Isotope & Hydrochemical Techniques To Address
Marine Coastal Pollution Along Karachi Coast-Pakistan
Institute Of Geology / University Of The Punjab,
|Number of Pages|
|Keywords (Extracted from title, table of contents and
abstract of thesis)|
Application, Isotope, Hydrochemical, Techniques,
Marine, Coastal, Pollution, Karachi, Coast, carbon, sulfur, Manora,
In this study,
stable isotopes of carbon (δ13C), sulfur (δ34S), oxygen (δ18O),
hydrogen (δ2H), nitrogen (δ15N) and radioactive isotope of hydrogen
(tritium) have been applied in combination with conventional
techniques (physiochemical and biological) to investigate Karachi
Coastal water pollution due to Layari and Malir rivers, which mainly
carry Karachi Metropolitan domestic and industrial wastewater, and
to determine the effect of seawater on the aquifer system of the
Physico-chemical (pH, electrical conductivity and turbidity),
biological (fecal coliform), heavy metal and stable isotope (carbon
and sulfur) characteristics of Layari and Malir rivers water,
Karachi coastal waters and sea sediments showed that Karachi
Metropolitan domestic sewage and industrial effluents were the main
source of coastal water pollution, and coastal water of Manora
Channel was heavily polluted as compared to water of southeast
coastal area of Karachi. However, the northwest coastal water was
marginally polluted. Turbidity and fecal coliform population levels
in seawater of Manora Channel and some locations along southeast
coast (Ghizri area and Ibrahim Haideri) were found above the WHO
recommended threshold limits set for seawater bathing.
Heavy metal contents of Manora Channel and southeast coastal waters
were higher than the Swedish guidelines for the quality of seawater.
In contrary, heavy metal concentrations in coastal sediments were
found to be significantly higher than that of seawater. Mn and Ni
contents in sediments of entire coast (Manora Channel, southeast and
northwest coast) were above USEPA guidelines except at Buleji site,
whereas Cr, Zn and Cu levels only in Manora Channel sediments were
higher than USEPA guidelines. The higher heavy metal contents of
Manora Channel water and sediments can be attributed to an influx of
a major portion of untreated industrial and/or domestic wastewater.
Layari and Malir rivers water was observed to be depleted in
δ13C(TDIC) and δ34S which showed heavy influx of sewage into these
rivers. Manora Channel water was also depleted in δ13CTDIC and δ34S
during low tide environment showing a large scale domestic
wastewater mixing with seawater. Southeast coastal water was found
to be slightly enriched in δ13C(TDIC) and δ34S and exhibited mixing
of relatively small quantity of sewage with the seawater as compared
to Manora channel. δ13C(TDIC) and δ34S contents of northwest coastal
water were close to the values meant for normal seawater.
δ13C and δ15N contents of Karachi coastal seaweed ranged from -31.1
to -4.9 ‰ PDB and 6.1 to 17.8 ‰ Air, respectively. Average δ15N
values (10.2 ‰ Air) of Ulva spp. collected from non polluted
northwest coast was higher as compared to average δ15N contents (8.0
‰ Air) of Ulva from Manora Channel suggesting that nitrogen isotopic
ratios of Ulva spp. could be a good indicator of sewage pollution.
The results of a two component isotope mass balance equation using
δ13C and δ34S values for Layari and Malir rivers and coastal water
indicated that tide conditions and distance of sampling site from
the pollution source were the main factors to control transport and
dissemination of Layari river pollution into Manora Channel. High
tide environment slowed down the Layari river water mixing with
seawater coupled with a gradual decrease in pollution levels from
Layari river out fall zone to Manora Lighthouse.
Physico-chemical characteristics of groundwater showed that shallow
aquifer system was not generally affected by seawater intrusion.
Deep groundwater was observed to be moderately (chloride contents
1000- 2000 ppm) to highly saline (chloride contents > 2000 ppm).
However, shallow and deep well located in vicinity of the Malir and
Layari rivers showed fecal coliform contamination which rendered
their water unfit for drinking.
An anion based piper diagram showed predomination of chloride and
bicarbonate ions relative to sulfate (SO4-2) ions in coastal
groundwater. It was inferred from Piper diagram that shallow aquifer
system was predominantly replenished by freshwater (mainly Layari
and Malir rivers basin), while salinity of deep aquifer owes to the
seawater intrusion or entrapped salinity. The δ18O composition of
groundwater and δ2H vs. δ18O relationship for groundwater of coastal
aquifer also indicated that shallow aquifer system was predominantly
recharged through fresh water sources. Salinity of deep aquifer
seemed to originate from seawater intrusion and/or from entrapped
salinity. These finding were strongly endorsed by anion and stable
isotope interpretations such as Cl-concentration vs δ18O, Cl-/HCO3
-1 ratio vs δ18O values and SO4-2 contents against SO4-2/Cl- ratio
of shallow and deep aquifers.
The present study has demonstrated that stable isotopes (δ13C, δ15N,
δ34S, δ2H and δ18O) can be effectively used to monitor the marine
pollution and to investigate origin of salinity in the coastal
aquifer. This study may also provide a precise and accurate isotopic
database for researchers interested in seawater pollution and its
effect on benthic life.