Applications of Nuclear Science in Environmental Studies

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Applications of Nuclear Science
in Environmental Studies
Ehsan Ullah Khan
Director Research
Center for Emerging Sciences, Engineering
and Technology (CESET)
Former Professor of Physics & Chairman, Department of Physics, GU.
Former Professor of Physics & Dean Faculty of Sciences, CIIT
Former Professor of Physics & Dean Faculty of Sciences, IIU
Deputy Chief Scientist, PINSTECH
Environment and Radiation
Types of Radiation
(i)
Ionizing Radiation
•
Ionizing radiation is composed of particles that
individually carry enough energy to ionize an atom
or molecule without raising the bulk material to
ionization temperature.
•
Ionizing Radiation is generated through nuclear
reactions either from an artificial or natural source
such as cosmic rays, alpha, beta and gamma rays,
X-rays, neutrons, and in general any charged
particle moving at relativistic speeds.
(ii) Non-Ionizing Radiation
• Non-ionizing radiation refers to any type of
electromagnetic radiation that does not carry
enough energy per quantum to ionize atoms or
molecules.
• Instead, of producing charged ions when passing
through matter, the electromagnetic radiation has
sufficient energy only for excitation. Nevertheless,
different biological effects are observed for different
types of non-ionizing radiation.
• Near Ultraviolet , Visible light, Infrared, Micro and
Radia Waves and low-frequency RF (longwave) are
all examples of non-ionizing radiation
Types of Radio-nuclides Present in the
Environment
(i)
Primordial Radionuclides
(ii)
Cosmogenic Radionuclides
That RNs that are present since the creation of earth
and having long half-lives, e.g. 210Pb, 226Ra
That RNs that are produced in the upper atmosphere
as a result of cosmic rays interaction with light
particles (carbon, Nitrogen and Oxygen), e.g. 7Be,
22Na, 32P, 32S
(iii) Anthropogenic Radionuclides
That RNs that are produced as a result of man-made
activities such as nuclear fuel fabrication, enrichment,
nuclear power generation, nuclear accidents etc.,
e.g. 137Cs, 134Cs, 131I, 90Sr etc.
1. Radon
• Radon is an invisible, colorless, odorless,
tasteless radioactive gas created during the
natural breakdown of uranium in rocks and
soils
• It is one of the heaviest substances that
remains a gas under normal conditions and is
considered to be a health hazard causing
cancer
• It has three isotopes, namely, 222R (238U),
220Rn (232Th) and 219Rn (235U). 222Rn has longer
half life (3.84 days) than the other two
isotopes
Radon in Buildings
There are
two main
sources for
the radon in
home's
indoor air:
the soil and
the water
supply
Health Hazard
• Breathing air that contains radon can cause lung
cancer
• Risk of lung cancer from breathing radon in the
air is much greater than risk of stomach cancer
from swallowing water with radon in it
• Most of risk from radon in water comes from
radon released into the air when water is used for
showering and other household purposes
• Radon in home's water is not usually a problem
when the water source is surface water. A radon
problem is more likely when the source is
groundwater (e.g., a private well or a public water
supply system that uses groundwater)
Radon Measuring Techniques
There are two techniques used for Rn
measurements
Passive Technique (Alpha sensitive plastics)
Accumulates the alpha radiation over certain
time period (months) to give average Rn
concentration
Active Technique (Pylon and RAD-7 Detectors)
Gives instantaneous value of Rn in air (also in
water as well as in soils)
Radon Survey in Pakistan
Rn Survey has been carried out in:
• Various divisions of Punjab including
Bahawalpur, Lahore, Gujranwala and
Rawalpindi Divisions
• Various districts in KPK including D.I. Khan,
Peshawar, Charsadda, Mardan, Hazara and
Swabi
• Parts of FATA, AJK and Islamabad are also
surveyed
• There is lack of radon data from different
provinces of the country, specially Sind and
Baluchistan
Radon Levels in Pakistan
o The results obtained so far show that
there is no area in Pakistan that has
higher level of Rn than Permissible level
of Indoor radon (4 pCi/l or148 Bq/m3). The
level has not crossed the limit even in
earth quack areas
o However, there is a need to prepare Rn
Map of Pakistan
like of USA & UK
Scientific Uses of Rn Studies
• Because of radon's rapid loss to air and
comparatively rapid decay, radon is used in
hydrologic research that studies the
interaction between ground water and
streams. Any significant concentration of
radon in a stream is a good indicator that
there are local inputs of ground water
•
Radon is also used in the dating of oilcontaining soils because radon has a high
affinity of oil-like substances
Scientific Uses of Rn Studies
•
Radon soil-concentration has been used in to
map buried close-subsurface geological faults
because concentrations are generally higher
over the faults. Similarly, it has found some
limited use in geothermal prospecting
• Some researchers have also looked at
elevated soil-gas radon concentrations, or
rapid changes in soil or groundwater radon
concentrations, as a predictor for
earthquakes. Results have been generally
unconvincing
2 (a). Radioactivity in Drinking Water
Neutron activation technique:
• Water samples are dried on Nuclear Track
Detectors, exposed to known fluence of
thermal neutrons at reactors. The number
of fission events are then co-related to the
concentration of radio nuclide
• This study has been carried out at a very
limited scale. Extended work is required to
have a comprehensive survey
2 (b). Radioactivity in Material used in
construction
•
226Ra, 232Th,
and 40K are easily detected
in building materials using NaI Detector
• Bricks, stones and other flooring materials
is crushed dry and gamma spectrum taken
• This study has been carried out in very
limited area and in limited building
materials
• Studies so far in Pakistan has not shown
any abnormal results
3. Measurement of
137Cs
in Soil
o The major source of 137Cs in the
atmosphere is atmospheric nuclear
explosions that were conducted by
developed countries from 1940 to 1960
o Among this huge amount ~ 90 % was
released by atmospheric testing, 6 % by
the Chernobyl accident and nearly 4 % is
released by nuclear fuel processing
facilities
o The site with deposition or erosion can be
identified only if a reference site has been
identified near the study
o A reference site has been identified in
Lehri Park, on GT Road near Jhelum for
the first time in Pakistan
o Hence ground is set for 137Cs based soil
erosion studies in Potohar region
Soil Measurements
(A)
Open Land Soil
1600
1800
Cs Inventory (Bq/m )
Wood Land Soil
2
1600
1400
1200
1000
800
600
400
137
137
(B)
1400
2
Cs Inventory (Bq/m )
2000
200
1000
2000
210
3000
4000
5000
6000
2
Pb Inventory (Bq/m )
7000
1200
1000
800
600
400
200
2000
3000
210
4000
5000
6000
7000
2
Pb Inventory (Bq/m )
210Pb
Vs 137Cs inventories in soil samples from open land
(A) and Woodland (B) sites. In both plots, in general with a
very few exceptions, 210Pb Vs 137Cs inventories are
linearly proportional.
17
Soil Measurements
7500
2000
(A)
Cs Inventory (Bq/m )
2
2
4500
150
100
Altitude (ft)
900
600
300
8000
7000
6000
0
5000
8000
7000
6000
5000
4000
2100
1500
0
(B)
137
50
1800
210
3000
1900
1600
1700
1800
1900
2000
2100
Pb Inventory (Bq/m )
6000
Altitude (ft)
210Pb
(A) and 137Cs (B) inventories in soil samples from study
sites of different altitudes. 210Pb shows decreasing while
137Cs depicts increasing trend with altitude.
18
210
Pb in Open Land
210
Pb in Woodland
60
137
50
Cs (Bq/kg)
(A)
40
30
20
10
0
a
b
c
Depth in soil
210Pb
d
Concentrations of
Pb (Bq/kg)
210
Concentrations of
70
15
137
12
Cs in Open Land
Cs in Woodland
(B)
137
9
6
3
0
a
b
c
d
Depth in soil
and 137Cs concentrations in soil samples from
open land (A) and Woodland (B) sites with increasing
depth in soil.
210Pb
137Cs is showing a
Exc. is decreasing But
decreasing trend with depth in soils.
4. Nuclear Aerosols as Atmospheric
Tracers
Some of the objectives are to study:
• Cloud scavenging and precipitation Processes
• Aerosols transit, deposition velocities and
residence time in the troposphere
•
The air-water exchange rate
• Aerosol traps above the above ground
vegetation
• Soil erosion
• Deposition patterns of air-borne contaminants
Main Uses are:
• Tracing of the atmospheric processes
• Climate change prediction
• Atmospheric dating:
e.g., dating of earthquake
eruption of earth releasing radon using 210Pb
• Better use of hydrological cycle
21
Aerosols and Related Processes
Aerosol package NCAR CAM4, Xiahong Liu
22
Rain Collector and Met Instruments
(a)
(b)
A
Background Spectrum
B
Air Sample Spectrum
Pb-210
46.5 keV
Pb-214
295 keV
Pb-214
352 keV
Cs-137
662 keV
K-40
1460 keV
(477 keV)
Part 1: Air Measurements
Map of Pakistan showing the wind directions on a sampling day
obtained from GrADS software (a) The overall view of wind
directions over Pakistan (b) the magnified view at the sampling
point (c) The colours in the arrow shows wind speed.
Part 1: Air Measurements
0.40
210
Pb
Experimental
Linear fit
Upper 95% CL
Lower 95% CL
0.30
0.25
0.20
0.15
0.10
0.05
Regime I
20
40
Regime II
60
80
Regime III
100 120 140
3
0.35
Monthly Mean Concentration [mBq/m ]
3
Monthly Mean Concentration [mBq/m ]
Measured Monthly Mean Concentrations
7
4.5
Be
Experimental
Data9D
UCL
LCL
4.0
3.5
3.0
2.5
2.0
1.5
20
Regime I
40
Regime II
60
80
100
120
140
Monthly Rain [mm]
Monthly Rain [mm]
Monthly concentrations (mBq m-3) of 210Pb
and 7Be in air samples against the amount
of rainfall.
29
Part 1: Air Measurements
6
210
Pb
0.6
0.5
0.4
0.3
0.2
0.1
Seasonal Concentration
7
Be
5
4
3
2
1
0
0.0
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
0.7
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
Seasonal Concentration of
210
Pb
Measured Seasonal Concentrations
Seasonal concentrations (mBq m-3) of
210Pb and 7Be in air samples.
30
Part 1: Air Measurements
-3
Pb (mBqm )
3
0.4
0.3
80-100 % C
60-80 % C
40-60 % C
20-40 % C
0-20 % C
Mixed F+C
20-0 % F
40-20 % F
60-40 % F
80-60 % F
1
100-80 % F
2
0.2
0.1
0.0
100-80 % F
80-60 % F
60-40 % F
40-20 % F
20-0 % F
Mixed F+C
0-20 % C
20-40 % C
40-60 % C
60-80 % C
80-100 % C
7
210
3
Concentration of
Concentration of Be (mBq/m )
Measured Concentrations and NFLL-FHL Air Masses
Concentrations of 7Be (mBq m-3) and percentages of
NFLL-FHL air masses in air samples. The error bars are
the standard deviation of 7Be and 210Pb concentration at
each bin.
31
0.0
0.5
0.4
0.3
0.2
0.1
3
Be Concentration [mBq/m ]
7
0.6
0
100-90% LP
90-80% LP
80-70% LP
70-60% LP
60-50% LP
50-40% LP
40-30% LP
30-20% LP
20-10% LP
10-00% LP
00-10% HP
10-20% HP
20-30% HP
30-40% HP
40-50% HP
50-60% HP
60-70% HP
70-80% HP
80-90% HP
90-100% HP
--
100-90% LP
90-80% LP
80-70% LP
70-60% LP
60-50% LP
50-40% LP
40-30% LP
30-20% LP
20-10% LP
10-00% LP
00-10% HP
10-20% HP
20-30% HP
30-40% HP
40-50% HP
50-60% HP
60-70% HP
70-80% HP
80-90% HP
90-100% HP
--
3
Pb Concentration [mBq/m ]
210
Part 1: Air Measurements
Concentrations of aerosols and Percent Pressure
6
5
4
3
2
1
Concentrations of 210Pb and 7Be (mBq m-3) and percentages of
High-Low pressures in air samples. The error bars are the
standard deviation of 210Pb and 7Be concentration at each bin.
32
Part 1: Air Measurements
Determination of residence time of aerosols
Statistics of the 210Pb, 214Pb and 7Be concentrations (mBq m-3) and mean residence
time of aerosol over Islamabad.
Quartiles
Mean
Uncertainty
Radionuclide
Min.
1st
Median
3rd
Max.
(µ)
(σ)
MRT
(days)
210Pb
0.056
0.172
0.246
0.390
0.761
0.284
0.012
5.29±0.91
214Pb
200.56
385.35
554.37
875.77
1371
631.06
155.47
7Be
0.772
2.321
2.977
3.672
6.847
3.171
0.084
7.18±0.97
Part 2: Precipitation Measurements
(b)
Throughfall Samples
30
25
20
15
10
Mar 10
Nov 09
Aug 09
May 09
Feb 09
Nov 08
Jul 08
0
Apr 08
5
Jan 08
Sampling Month/Year
35
Oct 07
(a)
Open Rain Samples
Pb Concentration [mBq l-1]
40
210
110
100
90
80
70
60
50
40
30
20
10
0
Oct 06
Jan 07
Apr 07
Jul 07
Oct 07
Jan 08
Apr 08
Jul 08
Nov 08
Feb 09
May 09
Aug 09
Nov 09
Mar 10
210
Pb Concentration [mBq l-1]
Concentrations of 210Pb
Sampling Month/Year
Concentrations of 210Pb in (a) open rain and (b) throughfall
samples during the sampling period. Straight horizontal lines
show respective mean values.
34
Part 2: Precipitation Measurements
Concentrations of 7Be
2000
Be Concentration [mBq l-1]
1600
1200
1400
1200
1000
800
600
400
200
7
7
Be Concentration [mBq l-1]
1800
(a)
Open Rain Samples
(b)
Throughfall Samples
1000
800
600
400
200
Sampling Month/Year
0
Oct 07
Jan 08
Apr 08
Jul 08
Nov 08
Feb 09
May 09
Aug 09
Nov 09
Mar 10
Oct 06
Jan 07
Apr 07
Jul 07
Oct 07
Jan 08
Apr 08
Jul 08
Nov 08
Feb 09
May 09
Aug 09
Nov 09
Mar 10
0
Sampling Month/Year
Concentrations of 7Be in (a) open rain and (b) throughfall
samples during the sampling period. Straight horizontal lines
show respective mean values.
35
Part 2: Precipitation Measurements
100
80
Regime I
Be Concentration (mBq/l)
(a)
Open Rain Samples
Regime II
60
40
20
0
7
210
Pb Concentration (mBq/l)
Concentrations of radionuclides and precipitation
0
100
200
300
Monthly Rainfall (mm)
400
(b)
Open Rain Samples
2000
Regime I
1600
Regime II
1200
800
400
0
0
100
200
300
Monthly Rainfall (mm)
400
Results of concentrations of (a) 210Pb and (b) 7Be radionuclides
versus monthly amount of precipitation.
36
40
30
20
10
(b)
Throughfall Samples
20
15
10
5
210
0
25
Pb Concentration (mBq/l)
50
(a)
Open Rain Samples
210
Pb Concentration [mBq/l]
Accumulated
Part 2: Precipitation Measurements
Concentrations of 210Pb
Autumn Winter
Spring Summer
Season
0
Autumn Winter
Spring Summer
Season
Accumulated concentrations of 210Pb in (a) open rain
and (b) throughfall samples for different seasons.
37
Accumulated
(a)
Open Rain Samples
1200
1000
(b)
Throughfall Samples
Be Concentration (mBq/l)
1000
800
600
400
200
800
600
400
200
7
7
Be Concentration (mBq/l)
1200
Part 2: Precipitation Measurements
Concentrations of 7Be
0
Autumn Winter
Spring Summer
Season
0
Autumn Winter
Spring Summer
Season
Accumulated concentrations of 7Be in (a) open rain and
(b) throughfall samples for different seasons.
38
Part 2: Precipitation Measurements
Activity Ratios of 210Pb and 7Be aerosols
1
210
(b)
20
7
Pb)
25
15
Activity ratio ( Be/
10
7
Activity ratio ( Be/
210
Pb)
(a)
Rain-Temp
10
5
Oct 06
Dec 06
Feb 07
Apr 07
Jun 07
Aug 07
Oct 07
Dec 07
Feb 08
Apr 08
Jun 08
Aug 08
Nov 08
Jan 09
Mar 09
May 09
Jul 09
Sep 09
Nov 09
Feb 10
Apr 10
0.1
100
1000
Altitude [m]
(a) Measured activity ratios of 210Pb and 7Be aerosols. Dashed
line shows the situation when activities of both aerosols are
equal whereas solid line is the mean value of all measured
activity ratios. (b) Activity ratios of 210Pb and 7Be aerosols for
39
different altitudes around the globe.
Part 2: Precipitation Measurements
o
2400
(a)
Mean annual rain (mm)
Mean maximum temperature ( C)
Mean Annual Rainfalls and Temps at Murree
2000
1600
Grand average
1200
800
400
0
1960
1970
1980 1990
Year
2000
2010
21
(b)
18
15
12
1980 1984 1988 1992 1996 2000 2004 2008
Year
Mean annual rain, at Murree, for the period of 1960-2009
and (b) mean maximum temperature for the period of
1980-2008.
Conclusion
• A number of Scientific groups in various R&D
centers and universities in Pakistan have been
using Nuclear radiations for environmental
Studies.
• Most of the Rn survey has been done using low
cost Nuclear Track Detection Technique
• There are very limited instruments available,
particularly N-type HPGe detectors for gamma
spectroscopy in the country
• There is a need to develop Rn map of Pakistan
through collaborative efforts
• Coordinated efforts are needed to promote the
culture of cooperation and readiness to extend
access to limited equipment available at various
fortunate locations
• The life cycle of atmospheric aerosols is complex.
Most atmospheric aerosols eventually drop to the
ground or get washed down with the rain.
However, some particles ascend to the highest
levels of the atmosphere, stay for a very long time
and travel long distances
• Since these particles know no borders,
international cooperation is essential in any
measures designed to control them.
Thank You Very Much
for your Patience
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