45
Many review studies have been carried out to assess the pollution problem especially in the Dar es Salaam area. Uronu 1995 analysed the development of the sewerage system in Dar es Salaam, from its construction in 1948
through its different extension phases in the 1970s. The report also assessed domestic sources of pollution along the coast of Dar es Salaam. Another review of the development of the sewerage system of Dar es Salaam was
done by Martinez 1998.
Other reviews include that of Bryceson 1981a who assessed the state of the marine environment in the East African Region, including Tanzania. In another study, Bryceson 1981b reviewed some problems of marine
conservation with particular reference to Tanzania. A comprehensive review of the sources of pollution in Tanzania mainland was conducted by Mgana and Mahongo 1997, who quantified all major human activities that
contributed to pollution of the marine environment. A similar kind of review was carried out in Zanzibar by Mohammed 1997 who investigated land based sources of pollution affecting coastal, marine and associated
freshwater environments on the islands. Other reports from Dar es Salaam are those by Bwathondi et al 1991 who compiled all available data at that time on pollution of the Msimbazi River and advised on the need for a
comprehensive multidisciplinary research. Mashauri and Mayo 1989 discussed the potential impact of discharging raw sewage into the Indian Ocean. In Tanga, Shilungushela 1993 made an inventory of destructive
activities to the marine and freshwater bodies in the Tanga region.
2.1.6 Applied research
Applied research in water quality and pollution consist of those that were carried out with the prime objective of assessing the social impacts of pollution. These include those of Chaggu 1993 who studied ground water
pollution in Majumbasita in Ilala District, Dar es Salaam and JICA 1996 who assessed environmental and sanitation conditions in Dar es Salaam. Outside Dar es Salaam, there were only a few studies. These that by
Munisi 1998 who made a comparative study of intertidal floral communities in polluted and unpolluted areas near Tanga Municipality. Hoskoning and M-Konsult 1988 solid waste management and pollution by sewerage
system in Dar es Salaam. Hoskoning and M-Konsult 1988 assessed solid waste management and pollution by sewerage system in Dar es Salaam. In Zanzibar, Gillian 1998 made an assessment of waste disposal practices in
hotels located in four tourist zones on Unguja, Zanzibar.
2.2 Research methodology
2.2.1 Sampling aspectsparameters
Sampling aspects and sampling parameters dealt with in the various studies depended on the type of information gathered. Whereas baseline and experimental studies gathered quantitative data on pollution indicators or their
impacts on flora, fauna or on whole ecosystem, applied and review studies mainly gathered non-quantitative data on other aspects of pollution. The later is exemplified by the study by Hoskoning and M-Konsult 1988 which
looked at some aspects of solid waste management and pollution by sewerage system in Dar es Salaam. Quantitative data were gathered through collection of samples, mainly water samples, and in few cases sediment
samples, and their analysis for their concentrations of nutrients, heavy metals, organo-chemicals, and coliforms. In addition to such basic data on pollution indicators, some studies have also collected data on environmental
conditions, such as water temperature and current patterns in their reports.
Some studies were of socio-economic focus and these relied on formal and informal interviews. Interviews were carried out through standard techniques. In his study on waste disposal practices in hotels in Zanzibar,
Gillian1998 interviewed hotel personnel and government officials to assess these practices in tourism zones in Zanzibar. Chaggu 1993 partly used questionnaires for user utilisation surveys to assess pollution at
Majumbasita in Dar es Salaam.
2.2.2 Instrumentation and techniques of sampling and data collection
46
With regard to instrumentation, most studies relied on basic equipment for sampling and analysis. In most cases water sampling was effected through the use of a simple bucket or beaker and as such sampling other than surface
water was impossible. Similarly, sediment sampling was done with the use of hand operated plastic corers. An ordinary thermometer was used widely to read water temperatures and this measurement was therefore limited to
surface water temperatures. Many studies measured turbidity and this was effectively done with the help of a secchi disc. Hand held refractometers were used widely to take salinity measurements.
The most widely used analytical instrument was the spectrophotometer. This was mainly used for nutrient analysis. There was very little automation. Consequently only few studies used the auto-analysis technique for
nutrient analysis for example. The absence of the auto-analyser in many labs was a serious limitation in that in cases where samples to be analysed were very small, for example from pore water, some nutrients especially
nitrates in sediments could not be analysed. Sophisticated instruments were used only rarely and in many cases samples had to be sent abroad for analysis. For example, in his studies on organic carbon distribution,
mineralisation, and fluxes in Maruhubi mangroves, Machiwa 1998, 1999 relied on a TOC analyser that was available in Stockholm. Similarly, Mohammed 1998 used a CHN analyser for the analysis of total nitrogen and
total carbon also in Stockholm.
Generally, the different methods employed in the above studies discussed gave more or less accurate data. Having said that however, there is a need of conducting regular inter-calibration exercises among different laboratories in
the country to ensure further improvement in the quality of data generated by different researchers.
2.2.3 Sampling frequency, time of collection and duration of study
