Tritium was introduced into the atmosphere primarily as a result of nuclear bomb testing from the period to The natural concentration of tritium in seawater is around 0. However, its concentration up to Bq kg -1 has also been reported in some seawaters [McCubbin and Leonard, ]. The most important use of tritium is in distinguishing water that entered in water bodies prior to from water that entered into water bodies after [Drever, ]. Tritium is also used for studying mixing of seawater with fresh water [Mazor, ]. As shown in Table 12 , tritium 3 H content was higher in water of Layari 7.
Tritium content of seawater in mixing zone of Layari River outfall area was 6. Tritium contents in Manora Channel water seawater were higher than southeast and northwest coastal water, which show mixing of Layari River in seawater of Manora Channel. Tritium content in between 0. Tritium contents of Karachi coastal water are between 0.
A two-component mixing equation was used to assess the pollution contribution to seawater by the Metropolitan wastewater by using stable carbon and sulfur isotopes in addition to the application of oxygen isotope ratio to determine fresh water mixing with seawater. Thus, isotopic values of the two end points such as polluted water body and seawater can be used to estimate the contribution of polluted river to marine water through a two-component isotope mixing equation [Spiker, ].
Numerous researchers [ 18 ; Balesdent, et al.
In this study, an attempt has been made to estimate mixing percentage of polluted water in marine environment through stable isotope signatures. The equation described in Section 3. The dominant factors that appear to control the extent of terrestrial pollution mixing with Manora Channel seawater are tide conditions, distance from the joining point of Layari River with sea and sampling season. High tide environment hinders the Layari river water mixing with seawater coupled with a gradual decrease in pollution levels from entrance point of Layari River into sea.
The mixing of river water with seawater is substantially high near Layari River outfall zone and gradually lowers toward Manora Channel exit with the exception at KPT and Bhaba Island where the addition of sewage input from local population may be considered responsible for increased pollution load. Mixing pattern is also appeared to be effected by seasonal environmental variations. In April, strong currents and high flow of seawater in Manora Channel diluted the Layari River added pollution as compared to weak current season and moderate seawater flow in the channel during September and December when volume of seawater in the channel is decreased; thereby, the ratio of Layari river water to seawater in channel is increased.
Mixing of Malir River with seawater is considerably high at the Ghizri area, which is the entrance point of Malir River in the sea. The pollution load diffuses quickly as the distance is increased from entrance point to other sampling sites. It appeared that mixing pattern is not much effected by seasonal changes during low and high tide environments except at Ghizri area. Tide height and distance of sampling sites from the Layari River outfall are the main factors that play part in transport and spread of Layari River pollution in Manora Channel.
There was an optimal mixing of river water with sea at Layari River outfall zone in high and low tide conditions. However, the fraction percent of polluted water in seawater appears to be gradually decreased from Layari River outfall zone to Manora Lighthouse Figure However, at sites like Marina Plaza, Casino, Naval Jetty, and Marina Club, the increase in mixing percent was not very significant Figure 17 , which is attributed to dilution of Malir River pollution by open sea currents.
It is evident from Table 13 that freshwater—seawater mixing is influenced by tidal height and distance from the fresh water source. Low tide environment is favored, and high tide environment slows the mixing process. A progressive reduction in proportion of freshwater into seawater is observed from Layari River outfall zone to Manora Lighthouse. Along southeast coast, mixing of freshwater with seawater is considerably high at the Ghizri area and Ibrahim Haideri Fish Harbor during low tide environment.
At sampling stations Marina Plaza, Casino, and Naval Jetty , the ratio of freshwater into seawater was not significant showing that Malir river water is diluted quickly by strong open sea currents. This study may also provide a precise and accurate isotopic database for researchers interested in seawater pollution and its effect on benthic life. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.
Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications. Edited by Maged Marghany. We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Keywords isotope carbon sulfur oxygen mixing sediments seawater coastal algae metals Karachi marine pollution. Introduction Marine pollution due to anthropogenic activities has now become a worldwide environmental concern [ 33 ].
Description of pollution sources of Karachi coast Metropolitan municipal sewage and industrial effluent are two major sources of coastal water pollution.
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Stable isotope techniques Naturally occurring isotopes are found in both stable and radioactive forms in the environment and are known as environmental isotopes [ 13 ]. Materials and methods 3. Location of sampling sites For sampling, Karachi coast was broadly divided into three zones: i Manora Channel, ii southeast coast, and iii northwest coast Figure 4. Sample collection and preservation The period of field sampling was spanned over 2 years April —September Chemical analysis Samples of seawater, river water, and groundwater were characterized in terms of electrical conductivity EC , turbidity, and pH.
Stable Isotope Techniques to Address Coastal Marine Pollution
Determination of polluted water mixing with coastal water A two-component isotope mixing equation was used to compute polluted river water mixing with coastal water. Results and discussion 4. Heavy metal concentration of polluted rivers and coastal waters Heavy metal levels in Layari and Malir river water and Karachi coastal waters are summarized in Table 1. Table 1.
Heavy metal contents of polluted river water and Karachi coastal water. Table 2. Heavy metal contentsof sea sediments Surficial sediments are a feeding source for biological life, a transporting agent for pollutants, and an ultimate sink for organic and inorganic matter settling.
Table 3. Heavy metal contents of coastal sediments.
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Table 4. Stable isotope characteristics of Karachi coastal water, sediments, and biota Stable isotope analysis of coastal water, sediments, and biota was undertaken in order to understand the mechanism of the land base terrestrial pollution transport to coastal ecosystem. Table 5. Table 6.
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All the values are an average of five. ND, not determined. Table 7. Table 8. Table 9. Table Tritium Tritium 3 H is isotope of hydrogen with relatively short half-life Tritium contents in river water and coastal water. Computation of polluted river water mixing with seawater using stable isotopes A two-component mixing equation was used to assess the pollution contribution to seawater by the Metropolitan wastewater by using stable carbon and sulfur isotopes in addition to the application of oxygen isotope ratio to determine fresh water mixing with seawater.
Percent mixing of freshwater—seawater. More Print chapter. How to cite and reference Link to this chapter Copy to clipboard. Available from:. Over 21, IntechOpen readers like this topic Help us write another book on this subject and reach those readers Suggest a book topic Books open for submissions. There is abundant.
This occurs both within vegetation types and through the distribution of species and ecotypes along moisture gradients. Terrestrial nitrogen cycling exhibits similar scaling. On short timescales, nitrogen availability is determined by the biophysical regulation of the activity of soil microbes, with nitrogen mineralization increasing as conditions become more microclimatically favorable for soil biological activity.
On somewhat longer timescales, nitrogen cycling is greatly influenced by changes in litter organic chemistry, which may change with the growth stages of a plant or over successional changes, as species with different litter chemistries change in abundance over time. Thus, variations in atmospheric deposition at mesoscales or larger, and in hydrology at the watershed or larger scale, are key controls on N cycling over very long timescales.
Nitrogen cycling in marine ecosystems is similarly dominated by a fast cycle on short timescales, governed by local trophic interactions and microbial recycling. But on seasonal to millennia timescales, transport of nitrogen to the euphotic sunlit zone is controlled by the coupling of large-scale ocean circulation to ocean biogeochemistry. Because of these multiple scales of regulation, issues of scale are critical in ecology. This fact has long been recognized: the first science workshop explicitly charged with addressing the science agenda of the IGBP produced the volume Scales and Global Change.
This approach has been extraordinarily fruitful and has also catalyzed successful interdisciplinary interactions e. It has proved resolutely difficult to extrapolate from basic enzymatic or physiological controls to large scales and long time intervals because of the hierarchy of control across scales. For example, in the early s the problems of calculating whole-plant or ecosystem photosynthesis from first principles of leaf physiology seemed intractable and empirical models dominated.
Work on leaf physiology along light extinction gradients within plant canopies demonstrated regularities in the relationship of canopy environmental variables to leaf physiology. Today there are many successful models of ecosystem CO 2 exchange based on first principles of photosynthesis and stomatal regulation. Two lessons can be learned from this research example and from experience with multiscaled measurements in general:.
Related Stable Isotope Techniques in the Study of Biological Processes and Functioning of Ecosystems
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