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. 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