Post on 01-Jun-2020
Radionuclides in Groundwater
State Hygienic Laboratory at the University of Iowa
Dustin May
Laboratory Supervisor
• What is radioactivity? And more importantly, why should you care?
• Types of Radioactivity – Alpha (α)
• Helium nucleus, 2 protons, 2 neutrons, positive charge – Beta (β-/β+)
• Electrons or Positrons, can have negative or positive charge – Photons (Gamma/X-Rays)
• Electromagnetic radiation • Often occur as a result of beta decay or electron capture
(γ/x-rays) or due to material interaction (x-ray, Bremsstrahlung)
– Neutrons • Deeply penetrating, usually man-made, often in particle
accelerators
Radioactivity
• Radioactivity Units – Becquerel (Bq) = disintegrations per second, SI
Unit, named after Henri Becquerel – Curies (Ci) = 2.22x1012 disintegrations per minute,
named after Marie & Pierre Curie • Roughly the disintegrations per minute of 1 gram of
radium-226…it’s a long story. • https://www.orau.org/ptp/articlesstories/thecurie.htm
Radioactivity
• Health Physics – Radioactive particles cause damage to cells and
DNA – Usually via either direct action (kinetic) or indirect
action (free-radicals and reactive oxygen species) – Two main types of effects, stochastic and
deterministic – Exposure to radiation comes from many sources – There is no such thing as a “safe” dose of radiation
Radioactivity
• Natural Radioactivity – Generally the result of
two decay series, originating from the primordial nuclides, Th-232 and U-238
– K-40 is the most abundant radioactive nuclide
• Also the only natural positron emitter
– Cosmic Radiation • Gamma/X-Rays,
particles generated in in atmosphere
Figure 1. Autunite ore, Calcium uranyl phosphate (Parent, 2011)
Radioactivity
• Uranium Series – Abundant in rock and
soil – Mixture of long and
short half-lives – Leads to complex
relationships – Radium is especially
soluble • Ra-226 is usually
most concerning in water
– Radon is a noble gas, low adsorption, non-reactive
NORM
Figure 2. Uranium decay chain. Half-lives and decay information were obtained from the NuDat 2 Database (NNDC 2013). Abbreviations: d, days; h, hours; m, minutes; s, seconds; y, years.
• Thorium Series – Thorium is more
abundant than U – Radium especially
soluble • Ra-228 usually
most concerning in water, but has a much shorter t1/2 than Ra-226
– Half-lives are very different than U series
NORM
Figure 3. Natural thorium decay chain. Half-lives and decay information were obtained from the NuDat 2 Database (NNDC 2013). Abbreviations: d, days; h, hours; m, minutes; s, seconds; y, years.
Radioactive Equilibrium
A. Figure 4. Secular Equilibrium, daughter t1/2 <<< parent t1/2 B. Figure 5. Transient Equilibrium, daughter t1/2 < parent t1/2 C. Figure 6. No Equilibrium, daughter t1/2 > parent t1/2
A B
C
Groundwater and Minerals
Figure 7. Interaction between minerals and groundwater (Porcelli & Swarzenski, 2003)
Iowa Bedrock Aquifers
Figure 8. Iowa bedrock aquifers (Prior et al, 2003).
• Drinking Water Regulations – Community water
supplies • >15 connections or
25 persons • Safe Drinking Water
Act (SDWA) – Combined Radium –
MCL = 5 pCi L-1
• Only Ra-226 and Ra-228
Risk Based Regulation
• Drinking Water Regulations – Uranium – MCL = 30 μgL-1
• Regulated as mass, not radioactivity
– Gross Alpha Particles – MCL = 15 pCiL-1
• Regulated excluding Uranium
– Gross Beta/Photon Emitters – MCL = 4 mremyr-1
• No enforcement in Iowa • Dependent on
susceptibility to man-made nuclides
Risk Based Regulation
• Review of Risk from Public Water Supplies – Risk calculated based of EPA FGR 13 – Several assumptions made
• 2 Liters consumed/day • Lifetime of consumption (70 years)
– EPA guidelines for Maximum Contaminant Level (MCL) • 1:10,000 to 1:1,000,000 mortal cancer incidence (CI)
• Available Data, Public Water Supplies in Iowa 2012-2017 – 547 Community Water Systems Tested – 856 Gross Alpha Analyses – 293 Uranium Analyses – 1049 Ra-226 Analyses – 1055 Ra-228 Analyses – 1.62 million Iowans Served
Risk
Risk Based Regulation
Figure 9. Risk Estimate for Iowans Consuming Public Drinking Water (May, 2017)
• Private Drinking Water – No regulation – Installation testing,
few tested for radionuclides
– Many wells are not treated
– Water softening – Radionuclide
impact in private well water
Risk Based Regulation
Figure 18. Well Spudder (Wikipedia, 2016)
Figure 10. Uranium Decay Series (Nelson, unpublished)
• Polonium-210 – Alpha emitter – High specific activity
(166 TBqg-1)3 – Uranium series – t1/2 = 138 days – Parent Pb-210
• t1/2 = 22.2 years
Current Research
• Polonium-210 Health Risk – ~50% ingested Po-210
retained (ICRP, 1993; Thomas et al, 2001)
– Accumulates in reticuloendothelial system (Moroz & Parfenov, 1971)
• liver, spleen, kidneys, and lymph nodes
– Ra-226 and Pb-210 incorporate into bony tissue
• Potential source of Po-210
Current Research
Figure 11. Death by acute radiation syndrome via Po-210 (Telegraph, 2006)
• Iowa Groundwater Monitoring Project – Fall 2015 Sampling, 59 sites – Public Wells – Mostly shallow, alluvial wells – Generally deemed vulnerable to surface water
contamination – Found very low concentrations of NORM
Current Research
Current Research
Figure 12. Sampling sites for FY2016 IGWM (Hruby, 2015)
• Private Well Water Study – Iowa is majority rural; represents a significant
population at risk – Private wells are entirely unregulated – Co-funded by CHEEC and SHL – Will examine 50 confined-aquifer wells across
Iowa – Broad range of chemical parameters – Uranium-series radionuclides, including radon
Current Research
• Parent, Géry. (2011). Autunite_1(France).jpg [Image file]. Retrieved from: https://upload.wikimedia.org/wikipedia/commons/3/39/Autunite_1(France).jpg
• Focazio MJ, et al. Occurrence of Selected Radionuclides in Ground Water Used for Drinking Water in the United States: A Targeted Reconnaissance Survey, 1998; U.S. Geological Survey Water-Resources Investigations Report 00-4273. Reston, VA:U.S. Geological Survey, U.S. Department of the Interior (2001).
• ICRP, 1993. Age-dependent Doses to Members of the Public from Intake of Radionuclides - Part 2 Ingestion Dose Coefficients. ICRP Publication 67. Ann. ICRP 23 (3-4).
• Thomas PA, Fisenne I, Chorney D, Baweja AS, and Tracy BL. Human Absorption and Retention of Polonium-210 from Caribou Meat. Radiat Prot Dosimetry (2001) 97 (3): 241-250.
• Moroz BB and Parfenov YD. 1971. Effects of Polonium-210 on the Organism. Moscow, Atomizdat. Translation Series Report AEC-tr-7300, Biology and Medicine (TID 4500), United States Atomic Energy Commission, Technical Information Center, National Technical Information Service, U.S. Department of Commerce, Springfield, VA. Issued April 1972.
• “Polonium-210.” Fact Sheet. May 2010. Health Physics Society. McLean, VA. Web. • Telegraph. (2006). Death by polonium-210 [Image file]. Retrieved from: http://i.telegraph.co.uk/multimedia/archive/00631/news-graphics-
2006-_631086a.gif • Porcelli, D and Swarzenski, PW. The Behavior of U- and Th-series Nuclides in Groundwater. Reviews in Mineralogy and Geochemistry (2003) 52
(1): 317-361 • Wikipedia. (2016). 874px-Well_spudder_8606.jpg [Image file]. Retrieved from:
https://upload.wikimedia.org/wikipedia/en/thumb/5/59/Well_spudder_8606.jpg/874px-Well_spudder_8606.jpg • Frame, PW. (1996). How the Curie Came to Be. Retrieved from: https://www.orau.org/ptp/articlesstories/thecurie.htm • Prior JC, Boekhoff, JL, Howes MR, Libra RD, VanDorpe PE. (2003). Iowa’s Groundwater Basics. Iowa Department of Natural Resources, Iowa.
Reference List