3.2 a known concentration. The concentration of uranium (ppb)

3.2
Effective dose due to ingestion and inhalation of 222Rn in water

Where
 is the effective dose
for inhalation,  is the Rn
concentration in water (kBq/m3) ,  is the Rn in air to
Rn in water (10-4), F is the equilibrium factor between Rn and it’s
progenies(0.4),I is the average indoor occupancy time per individual (7000ha-1)
and DCF is the dose conversion factor for Rn exposure (9nSv(Bqhm-3)).

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

 

Where  is the effective dose for ingestion,  is the222Rn concentration in water
(kBq/m3),  is the weighed estimate of water
conception(730 l/a) and EDC is the effective dose coefficient for ingestion
(3.5nSv/Bq) respectively1.

 

3.3
Procedure to determine the uranium concentration in water using LED Fluorimeter

The uranium
analyzer is a compact analytical instrument to measure uranium concentration in
trace levels (ppb) in aqueous environmental samples 4 The concentration of
uranium in water samples were measured using Laser fluorometer. It works on the
principle of detection of fluorescence of uranyl complex formed by the addition
of an inorganic reagent called fluran 5,6. A standard stock solution of 1.179
g U3O8 was diluted to specific concentrations for regular
calibration of the system. Sodium pyrophosphate (5 %) was used as the
fluorescence-enhancement agent and for the formation of the uranyl complex,
because uranyl phosphate complexes are stable. A 5 ml of water sample was placed
in a dry and clean cell, 1 ml of 5 % sodium pyrophosphate (pH 7) was added and
fluorescence counts were noted. The instrument was calibrated with standard
uranium solution of a known concentration. The concentration of uranium (ppb)
in samples was calculated using the following equation:

Where

D1 is
the fluorescence counts due to sample only,

D2
the fluorescence counts due to sample and uranium standard,

V1
the volume of uranium standard added (ml),

V2
the volume of sample taken (ml) and

C is the concentration
of uranium standard solution (ppb).

 

3.3 Ingestion dose due to
Uranium in drinking water:

Ingestion dose was estimated using the intake of uranium through
drinking water pathway for different age groups according to the water intake
rates as presented in. According to the ICRP-60, dose coefficients for infants
is 1.2×10-7,  6.8 ×10-8
for children and 4.5 ×10-8 SvBq-1 for male and female adults 7.

3.4 Effective dose

Total effective
radiation dose was calculated considering drinking of 730 ly-1. This
corresponds to 2 liter of water consumed daily by the people. Dose conversion
factor (DCF) is equal to 4.5 × 10?8 SvBq-1 for 238U.
The annual radiation ingestion dose due to uranium intake through the drinking
water pathway was calculated using the following equation:Ingestion dose (Sv.y-1)
= Uranium concentration (Bq .l-1) x Intake of water (l.y-1)
x Dose conversion factor (Sv Bq-1).

 

                                                                                                                             
I.           
RESULTS
AND DISCUSSION

238U and 222Rn were measured in
water samples collected from bore well in and around Kodagu distrct and the
results are given in table 1. Uranium concentration in the studied water
samples varies from 0.013 to 0.083 Bq l-1 with an average of 0.046
Bq l-1. Radon concentration varies from 6.38 to 30.69 Bq l-1
with an average of 13.49 Bq l-1. The total dose due to U and 222Rn
concentration in water varies from 33.93 to 158.46 ?Svy-1 with an
average of 69.97 ?Svy-1. The average annual effective dose due to U
and 222Rn concentrations in bore well water samples are below the
MCL limit recommended by EPA, WHO and AERB. The annual effective dose is well
below the recommended limit of 100 ?Svy-1 8-10.

Maximum U concentration in ground water is
observed at Chettalli. Higher concentration of uranium in this region may be
due to presence of granite rocks present in this region. The concentration of
uranium in water varies from one place to the other depending on lithology,
geomorphology and other geological conditions. Uranium easily dissolves in
water and occurs both in dissolved and particulate forms. It can enter food
chain from soil, water and fertilizers.

Even though the most parts of the study
area contains different types of gneisses and granite rocks the uranium
concentration in water depends on the depth of the bore well and uranium
content in the host aquifer rock. The variation between radon concentration and
uranium concentration in water is shown in figure 2. A poor correlation has
been observed between radon concentration and uranium concentration in water.