Uranium Toxicity in the State of Punjab in North-Western India - Management of Natural Resources in a Changing Environment - page 261

Methodology
Eight samples of top soil from different locations in Punjab State lying between
29.5° N and 32.5° N latitude and between 73.8° E and 76.9° E longitude represent-
ing region having threshold and above threshold uranium concentration in ground
water besides those from where no uranium toxicity has so far been reported were
collected using standard auger method. Two additional top soil samples were
obtained for comparing purpose from sites nearly 1,000 km away known to be
normally fertilized and located in the State of Uttar Pradesh (22.4° N and 88.4° E)
which too like the State of Punjab lies in the Indo-Gangetic plain to act as compara-
tor. The only parameter common to all the samples was that they all had common
geologic origin i.e. the Indo-Ganges Alluvion.
The samples were dried for a day in an oven at 60 °C until moisture was driven
out and then further pulverized and homogenized. 50 g of the dried, pulverized and
homogenized soil samples were then packed in leak proof PET containers. The sealed
containers were kept aside for 4 weeks for attainment of secular equilibrium between
radium, thorium and their daughter products before carrying out measurements
using direct gamma spectrometry.
The uranium concentration ( 238 U) was determined by high resolution low level
gamma ray spectrometry following the 186.2 keV gamma line of the daughter 226 Ra
which is in secular equilibrium with its precursor namely 238 U. The samples were
measured using a 40 % high purity germanium detector shielded by 10 cm of lead
and coupled to a 16 K multi channel analyzer. The resolution of the detector was
found to be 1.7 keV at 1,332 keV gamma peak of 60 Co. The spectral analysis was
carried out using the GENIE 2000 software program (Canberra Co., USA).
Results and Discussion
Table 1 shows the concentration of the elements of interest expressed in terms of
disintegration of 238 U per gram of soil as well as in mg/kg (ppm). Samples PUH1,
PUH2 and PUH3 are from locations from the region showing high level of uranium
in ground water, samples PUT1, PUT2 and PUT3 are from locations from the region
where threshold concentration of uranium in ground water was observed and
samples PUN1, PUN2, UPN1 and UPN2 are from locations from the region where
so far no report related to uranium toxicity has been published.
It can be clearly observed from the obtained experimental data that the mean
concentration of uranium based on three measurements in top soil irrespective of the
locations from where they were collected seems to be not only low and comparable
but even lie within the mean natural abundance of 3 ppm (Kabata-Pendias 2011 ).
Therefore it becomes rather diffi cult to conclude that uranium from fertilizers in
top soils could be the main cause for the observation of extremely high levels of
uranium in water in the Malwa region of Punjab.