The book titled, X-Ray and Gamma Ray Spectrometers for
Environmental Studies in Tanzania is written with the aim of disseminating
knowledge about the Gamma and x-rays, detectors, the measurements and the
results of a research work done. These include Shell Fish in the vicinity of
the port of Zanzibar, Vegetables and radionuclides of polluted air, all in
Tanzania.
The X-ray analysis in its Energy Dispersive X-ray
fluorescence (EDXRF) and Wavelength Dispersive X-ray fluorescence (WDXRF)
techniques for investigations of different types of samples are described.
Samples with radionuclides have been analysed by Gamma-ray Spectroscopy. The
process in the radionuclides begins with the nucleus of an unstable atom losing
energy by emitting radiation. The elements or isotopes that emit radiation and
go through radioactivity are known as radioactive elements. There are many of
these particles in the air, water and even food that we eat. The aim of chapter
one is to highlight the procedures, methodologies and facilities that are used
in the analysis of the coming chapters.
The report on the existence of a link between seafood and
toxic heavy metals in human beings is given. The aim of this chapter is to
assess the metal concentration of shellfish along the Sea Port of Zanzibar. The
shellfish include; oysters, mussels, clams and crabs. They were collected at
the Sea Port and the concentrations were determined using Energy Dispersive
X-ray Fluorescence (EDXRF). In Zanzibar, the major source of food for a large
number of populations comes from the sea like many coastal area residents.
Concentrations range in clams, crabs and for Cr, Mn, Fe, Ni, Cu, Zn, Cd and As
were found. The concentrations of heavy metals in most different species of
shellfish could be attributed to water from sewage, marine activities, paints
and human activities from the ship.
Chapter three reports on the results of vegetables from Dar
es Salaam are given using Wavelength Dispersive X-ray fluorescence (WDXRF). The
sample analyzer machine is equipped with an Rh anode tube with spot focus
operating under vacuum conditions. The operating voltages vary from 20 kV to 60
kV with current from 50 mA to 5 mA. The characteristic x-rays from the sample
were collimated before arriving at the analyzing crystal under a vacuum of 0.05
mB and detected using a proportional counter and NaI (Tl) x-ray detector biased
at -1000V. The net peak is as of the characteristic lines was determined using
a non-linear least square fitting procedure. The whole detection and crystal
system was shielded by a 10 mm lead shield. Analysis time ranged between 20-50
seconds for each element and about 100 for the standard sample. Elements in the
material range from C, N, O, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Ni, Mn, Fe,
Cu, Zn, Br, Rb, and Sr. The values obtained are within range of those published
as essential as foodstuff.
Chapter four of this book focuses on the activity
concentrations data of radionuclides 7Be and 212Pb. These are from the CTBTO
radionuclides monitoring station located in Dar es Salaam where for the first
time is measured and analyzed. In Tanzania, the data were used together with
the meteorological one to investigate the mechanism that governs radionuclide
concentration levels in the atmosphere. The two radionuclides of different
origins showed different periodic patterns of atmospheric concentration for the
past 11 years (2008 – 2018). No correlation was found between 7Be and 212Pb
activity concentration. This suggests that the surface air concentration
between 212Pb (was a terrestrial radionuclide) and 7Be (was cosmogenic
radionuclide), was affected differently by local conditions of atmospheric
processes. The mean values of both 7Be and 212Pb were higher in dry seasons and
lower in rain seasons due to vertical mixing and greater deposition of
radionuclides. It was also observed that, both 7Be and 212Pb decrease with the
increase in rainfall and humidity.
Author(s) Details
Yusuf Ismail Ally
Koleleni
Department of Physics, University of Dar es Salaam, P. O.
Box 35063, Dar es Salaam, Tanzania and Department of Physics, Muslim University
of Morogoro, P. O. Box 1031, Morogoro, Tanzania.
Please see the book here:- https://doi.org/10.9734/bpi/mono/978-81-974388-4-4/CH0
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