Paper TWENTY-FIVE YEARS OF ENVIRONMENTAL RADIONUCLIDE CONCENTRATIONS NEAR A NUCLEAR POWER PLANT Charles Harris,* Danielle Kreeger,†‡ Ruth Patrick,‡ and John Palms§ Abstract—The areas in and along a 262‐km length of the Susquehanna River in Pennsylvania were monitored for the presence of radioactive materials. This study began two months after the 1979 Three Mile Island (TMI) partial reactor meltdown; it spanned the next 25 y. Monitoring points included stations at the PPL Susquehanna and TMI nuclear power plants. Monthly gamma measurements document concentrations of radionuclides from natural and anthropogenic sources. During this study, various series of gamma-emitting radionuclide concentration measurements were made in many general categories of animals, plants, and other inorganic matter. Sampling began in 1979 before the first start-up of the PPL Susquehanna power plant. Although all species were not continuously monitored for the entire period, an extensive database was compiled. In 1986, the ongoing measurements detected fallout from the Chernobyl nuclear accident. These data may be used in support of dose or environmental transport calculations. Health Phys. 108(5):503–513; 2015 Key words: Chernobyl; monitoring, environmental; radiation dose; radiation, gamma
INTRODUCTION THIS STUDY compiled 25 y of actual radiation concentration measurements of species in many general categories of animals, plants, and other organic and inorganic matter. The presence of radionuclides measured in a species may have originated from a sorption process or direct exposure of any of the matter or organisms that become incorporated into the food web of the environment. Studies have been conducted for various radiation interactions with the environment (Haas et al. 1998; Simmonds *US Nuclear Regulatory Commission, retired, 11 Mills Road, Gaithersburg, MD 20877; †Partnership for the Delaware Estuary, One Riverwalk Plaza, Suite 202, Wilmington, DE 19801; ‡Academy of Natural Sciences of Drexel University, Patrick Center for Environmental Research, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103; §Distinguished Professor Emeritus, University of South Carolina, Office of the President, Columbia, SC 29208. The authors declare no conflicts of interest. For correspondence contact: Charles Harris, 11 Mills Road, Gaithersburg, MD 20877, or email at [email protected]. (Manuscript accepted 25 November 2014) 0017-9078/15/0 Copyright © 2015 Health Physics Society DOI: 10.1097/HP.0000000000000266
1998; Voigt et al. 2000). In recent years, even more detailed and sophisticated studies have been undertaken (Camplin and Jenkinson 2007). Among such efforts, this study has several unique aspects, including a span of 25 y with monthly measurements; data collected in Pennsylvania from the 1986 nuclear accident in Chernobyl, Ukraine; measurements after the reactor core meltdown at the Three Mile Island nuclear plant; and samplings taken from a very large variety of animals, plants, and inorganic materials. The map in Fig. 1 depicts many (not all) of the monitoring stations in the Susquehanna River and in the surrounding land areas near the PPL Susquehanna Steam Electric Station (SSES). Radiation monitoring was also performed directly upstream and downstream from the TMI nuclear power plant. Table 1 is a listing of when each of the species was surveyed with some notes to further describe the categories listed. Monitoring included measuring radionuclide concentrations in air, water, diatoms, and foods such as meat, fish, fruits, and vegetables. The Academy of Natural Sciences (ANS)** in Philadelphia, PA, led this monitoring program (Patrick and Palms 1983–2003). Sampling began before the first PPL Susquehanna plant start-up and continued through the next 24 y of the power plant’s operation. The entire ANS environmental program includes a wide variety of aquatic and terrestrial plants, animals, and inorganic matter. Two previous Health Physics Journal publications describe much of this environmental radiation monitoring in much more detail (Palms et al. 2007; Patrick et al. 2007). A complete treatment of the entire 25‐y data set for periphyton was given, including the relationship to anthropogenic monthly power plant releases. Also, a detailed explanation of Chernobyl 1986 fallout in the Susquehanna River was explained therein. Several of the best bioaccumulator substances presented in this current paper (periphyton, lichens, flocculated sediment, and litter-humus) were already given greater attention in the 2007 publications.
** The Academy of Natural Sciences is now the “Academy of Natural Sciences of Drexel University.”
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Fig. 1. Years when species were monitored.
The list of materials studied includes the following: periphyton, flocculated sediment, litter humus, lichens, fish flesh, fish muscle, mussels, snails, crayfish, insects, mushrooms, squirrels, deer, cabbage, tomatoes, coarse sediment, plastic bags, sticky paper, bee pollen, honey, aquatic vascular plants, amphipods, beans, corn, lettuce, Swiss chard, potatoes, carrots, canopy leaves, and fertilizers. The entire database of these thousands of measurements is compiled at the Academy of Natural Sciences of Drexel University
(Patrick et al. 1979–1982; Patrick and Palms 1983–2003). The collected data were sorted into four categories: 1) inedible materials in air contact, 2) terrestrial edible plants and animals, 3) aquatic edible food sources, and 4) aquatic inedible materials. MATERIALS AND METHODS Table 1 is a condensed summary of the several hundred taxonomic species, materials, chemicals, and other inorganic
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Radionuclide concentrations near a power plant c C. HARRIS ET AL.
and organic compounds and mixtures that were sampled. For example, one species is called mussels. However, strophitus undulates, lampsilus cariosa, and elliptio complanata are only three of eight taxonomic mussel species sampled in 2001. Various trees and shrubs contribute to litterfall and humus, but for the single category called “litter-humus,” samples actually included material from 46 varieties of trees and shrubs. A final example of the large number of actual species is periphyton. Periphyton includes over 300 varieties of diatoms. Descriptions of the most important of the species follow. For a complete description of the taxonomy of the plant and animal species and other materials, one may refer to the 25 annual reports by Patrick et al. (1979–1982) and Patrick and Palms (1983–2003). As indicated in the Fig. 1 map, Ricketts Glen State Park is a pristine environment far north and far upstream from any likely nuclear contaminants from the SSES. Therefore, the park was selected as an overall control station. The following sections give a listing of brief definitions and descriptions of the major substances, plants, or animals that were measured for radionuclide concentrations. Aquatic studies Periphyton refers to a large variety of aquatic organisms growing attached to a surface. Such organisms include bacteria, algae, protozoa, and microscopic multicellular animals. Included among periphyton are some 300 varieties of diatoms in the Susquehanna River. Radionuclide gamma activity was measured in periphyton every month for the entire 300‐mo duration of the project. Flocculated river sediment (floc) consists of organic and inorganic particles transported into and along riverbeds via erosion and runoff. Radionuclides bound in terrestrial or aquatic organisms may enter into flocculated sediment in detritus, including both fecal matter and carcasses. Aquatic snails are mollusks that graze mainly on periphyton and organic detritus. In turn, some snails are consumed by fish. Snails are efficient accumulators of manmade radionuclides. Snails were continuously monitored between 1990 and 1997 and again in 2001. Aquatic vascular plants are consumed by a variety of aquatic fauna. These plants have been shown in some ecosystems to be accumulators of heavy metals and radionuclides (Domotor and McLean 1989; Whicker et al. 1990). Vascular plant species included western waterweed (elodea nuttallii), water stargrass (heteranthera dubia), American water willow (justicia americana), and pondweed (potamogeton sp.). Larval forms of aquatic insects provide a vital food web link between algae, detritus and other benthic organisms, and fishes. Nymphal and larval stages of insects appear to have an accumulation mechanism beyond a simple sediment association (Whicker et al. 1990). Because of this food chain relationship, aquatic insect larvae are potential
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transporters of radioactive materials to fish and, ultimately, to humans. Dobson fly larvae (hellgrammites), mayflies (both the heptogenidae and the isonychia genera), and caddisflies (hydropsychids) were aquatic insects included in this program. Crayfish are also accumulators of radioactive materials (Domotor and McLean 1989). As omnivores and scavengers, they feed on a variety of components in the food web and are also readily consumed by many fishes. Bivalve mollusks, or mussels, are known to accumulate heavy metal radionuclides efficiently (Goldberg et al. 1978). Their main sources of nutrition are algae, small zooplankton, detritus, and bacteria. During 2001, a composite sample of native freshwater mussels from the Susquehanna River was collected to examine whether radionuclides could be accumulated over longer times than previously studied in transplanted mussels. In addition to tissue analysis, the mussel shell material was also analyzed. Fish provide a direct radiological dose-to-human pathway because they are consumed directly. Representative species of carnivorous, omnivorous, and bottom-feeding fish were collected to obtain composite muscle tissue samples. Species sampled included the scavenger Northern Hogsucker (Hypentelium nigricans), Smallmouth Bass (Micropierus dolomiew), Carp (Cyprinus carpio), and Bluegill sunfish (Lepomis aurilus). Adult fish and fish larvae samples were collected. Since radionuclides may enter free-ranging fish at various locations, an experiment was also performed on fish in a fixed caged. Amphipods comprise a wide variety of both marine and freshwater crustaceans. They are important herbivores, detrivores, and scavengers because they inhabit almost all areas of rivers, lakes, and seas (Holsinger 1972). Samples taken in this study were not dissected for complete classification; rather, they were considered as one grouping of gammaridean amphipods. Although aquatic studies concentrated on species in contact with river water, some measurements were made of lake water in the vicinity. These values were considered as control measurements, which did not receive power plant effluents containing anthropogenic radioactive materials. Terrestrial plant and soil studies Canopy leaves atop the forest may accumulate fallout from nuclear weapons or atmospheric releases from a nuclear plant. To monitor effects after the 1986 Chernobyl accident, the canopy leaves of several tree species were collected during the 1986, 1987, and 1988 growing seasons. A lichen is a composite organism, consisting of a fungus and an alga or cyanobacterium, living in symbiotic association. Many lichens are extremely sensitive to metals uptake from atmospheric pollution and have been used as pollution indicators (Richardson 1992).
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FOOTNOTES: (1) Chernobyl accident of 1986—a special measure of periphyton was initiated, repeated in 1991.
Amphipods Aquatic Insects Aquatic Vascular Plants Aqueous Snails Caged Fish Canopy Leaves Course Sediment Crayfish Deer (8) Filtration Plant Precipitates Fish Flesh Fish Muscle/Kidney/Liver Flocculated Sediment Garden (11) Garden Additions Glass Beads Grid Soil Samples Honey Honeybees In Situ Soil Tests Lichens Litter Humus Mammal Food (4) Mammal Tissue (2) Mussel Shells Mussels Pasture Grass Periphython Plastic Garbage Bags Pollen Radio Carbon Analysis (6) Regular Crops Soil (Surface) Soil Core Sr and Transuranics Sticky Paper Synthetic Resin Beads Vegetation (7) Wood
1979 1980 1981
Table 1. Years when species were monitored.
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(2) Mammal Tissues include: Squirrels, rabbits, and woodchucks (3) Mammal Tissue: For 1989–1992 includes only squirrels; 2000 includes squirrels, turkeys, and grouse (4) Mammal Food includes mushrooms, which were sampled separately from 1988 onward. (5) Because of the Chernobyl accident of 1986, monthly samples, as well as an annual sample at harvest were taken. (6) Potato leaves and tubers were analyzed. (7) Includes; Trees, saplings, seedlings, shrubs, herbs, and ground cover, at Quarry Hill location. (8) In 1980 and 1986, sample data were provided by Radiation Management Corporation. (9) Data by Radiation Management Corporation (10) Drought; No mushroom crop. (11) Garden: Lettuce, Cabbage, Chard, beans, tomatoes, corn, potatoes, carrots and soil. Plant parts include: leaf, stem, fruit, and root tubers. (12) Additives include: Grass seed, bean seed, corn seed, annual ryegrass, potato seed, cabbage plants, cabbage roots, tomato plants, tomato roots, 5-10-5 fertilizer 10-10-10 plant food, tri-phosphate fertilizer 0-44-0, Start and Grow fertilizer 16-32-16, ammonium nitrate 35%N fertilizer, fertilizer lime, dolomitic lime fertilizer, dolomitic limestone fertilizer, liquid nitrogen fertilizer, soda fertilizer 16-0-0, 46-0-0 fertilizer, 0-44-0 fertilizer, 10-10-10 fertilizer, 5-10-5 plant food fertilizer, Thomasville pulverized limestone fertilizer, lime, 0-25-25 plant food fertilizer chlorothalamil pesticide, liquid dylox pesticide (Gypsy Moth Spray), Malathion methoxychlor pesticide, captan vegetable dust, carbaryl mareb pesticide, mareb-Seven pesticide, dacthal herbicide, krenite herbicide (13) Cow manure, 0-46-0 garden fertilizer, 0-0-60 fertilizer. (14) Samples include: lichens, moss, and ferns (15) Samples include: lichens, and substrate rock.
Radionuclide concentrations near a power plant c C. HARRIS ET AL.
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Decaying fallen leaves from trees and plants are called litterfall. Humus results from the breakdown of plant material. Litter-humus is a term used to describe litterfall and humus as a combined radioactive material biomonitor. Trees and shrubs contributing to the Pennsylvania litter-humus included black oak, white oak, maple, and black birch. In all, 46 individual species of trees and shrubs were identified in the sampling areas. Mushrooms were originally sampled and included with other mammal foods as an annual harvest. From 1988 onward, mushrooms were sampled separately. Also, following the Chernobyl accident, monthly samples were taken during 1986, as well as the annual harvest sample. For several years in the 1980s, as seen in Table 1, two gardens were planted by ANS researchers on the grounds of the PPL Susquehanna power plant. The gardens were strategically located to monitor the prevailing winds over the power plant. Garden vegetables included lettuce, cabbage, Swiss chard, beans, tomatoes, corn, potatoes, and carrots. Grass seed, bean seed, corn seed, annual ryegrass, potato seed, cabbage plants, cabbage roots, tomato plants, and tomato roots were also analyzed. Fertilizers and pesticides were also studied. These garden additives included: cow manure, ammonium nitrate, lime, dolomitic lime, dolomitic limestone, Malathion, and some 20 other pesticides and fertilizers. In situ gamma-ray spectrographic soil studies were performed each year from 1980 through 1987, yielding estimates of the concentrations of gamma-emitting radionuclides in the soil and their associated exposure dose (Coleman et al. 1976; Tanner et al. 1985). Terrestrial animal studies The quantities of radioactive materials in mammals were examined. Tissue sources included deer, squirrels, rabbits, black bears, and woodchucks. Two bird species, turkey and grouse, were also sampled. In 1980 and 1986, radionuclide concentration data from hunted deer tissue were provided by Radiation Management Corporation of Philadelphia, PA††. Honey, pollen, and bee samples were collected and measured. Pollen and honey have been shown to be suitable biological indicators of radioactive trace elements in the environment. (Kirkham and Corey 1977; Gilbert and Lisk 1978). Inorganic studies Several public water supplies obtain water directly from the Susquehanna River. Therefore, some water sampling stations were established at public water supply intake locations. Also, water filtration plant precipitates were analyzed. Periphyton does not grow well in winter weather, so in 1992 and 1993, studies of ion-exchange chelex and stator †† The address at the time of measurement was: Radiation Management Corporation, 3508 Market Street, Philadelphia, PA, USA, 19104.
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resin beads were conducted as a test alternative. The ionexchange materials could absorb radioactive materials in a manner similar to periphyton. Also, glass beads having a minimal materials uptake rate were examined as a control in 1993. Glass was used to verify that resin bead radioactive material uptake measurements were actually from waterborne sources and not from materials already mixed in with the resin. It is reasonable that radioactive materials may be present in the atmosphere and possibly deposited on land (or water) or inhaled. Therefore, some monitoring was done using sticky paper. With this paper, depositions of airborne inorganic (and organic) matter were taken occasionally. Experimental procedures Radionuclides measured. Only gamma-ray emitting radionuclides were measured. Radionuclides near PPL Susquehanna can come from several sources, including naturally occurring, anthropogenic from the nuclear plant or medical sources, and fallout from weapons testing. The radionuclides considered in theses analyses included: 7 Be, 14Be, 40K, 51Cr, 54Mn, 58Co, 59Fe, 60Co, 65Zn, 103Ru, 110m Ag, 129I, 131I, 134Cs, 137Cs, 140Ba, 141Ce, 144Ce, 210Pb, 214 Pb, 226Ra, 228Ac, 232Th, 239Pu, 240Pu, and 241Am. Sampling. Various sites along the Susquehanna River were sampled, both upstream and downstream from the PPL nuclear power plant. Terrestrial and aquatic control stations were located far from the other sampling stations. Minimum detectable activities, minimum detectable concentrations, calibration, and statistical methods are detailed by Coleman et al. (1984). Materials and methods for terrestrial and aquatic studies are extensively detailed by Patrick and Palms (1983-2003), but some brief descriptions of representative sampling methods are given below: • Periphyton were collected on glass slide diatometers. After drying, samples were analyzed for radionuclide content using gamma spectroscopy; • Flocculated sediment was vacuumed from various surfaces on the river bottom, filtered, and dried; • Lichens were collected from rocks in forest sites. Locations varied from year to year, and the number of locations ranged from five to 11 sites; • Samples of litter-humus were collected in the fall months. Square grid sections of a set depth were laid out in areas exposed to the open sky; and • Fish, deer, and other river and land animals were caught to obtain tissue, shell, or other cellular samples. Radiometric analysis. Since periphyton was the only species collected in each of the 300 months, it is used here as a more detailed example of analyses: Glass slide diatometers were placed in the river and collected on a monthly basis. The periphyton were scraped
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into a petri dish using a rubber policeman and dried in a laminar flow oven at 90-95 °C, then pulverized. Samples of approximately 0.5 to 20 grams were analyzed in a petri dish, using a high-resolution gamma-ray spectrometer. All of the measured species were sorted into four categories: 1. Inedible materials contacting air: All inedible non-aquatic species were grouped together. These materials, such as canopy leaves, trees, shrubs, surface soil, and sticky paper were all in contact with the air. Of course, airborne particles are not the only possible source of radionuclides within these materials; 2. Waterborne inedible species and materials: Periphyton was found to be the best bio-accumulator of radioactive metals in the Susquehanna River (Patrick et al. 2007; Palms et al. 2007). Flocculated sediment of the riverbed is also a good bio-accumulator in contact with the river water. A difference between periphyton and floc is that periphyton was collected on glass slides near the water surface, while much of the floc content comes from runoff, detritus, and fecal matter. Therefore, waterborne radioactive materials are the sole contributors of radionuclides for periphyton, but that is not so for flocculated sediment. Other inedible samples in the river included amphipods, coarse sediment, mussel shells, and aquatic vascular plants; 3. Terrestrial food: Radionuclide concentrations measured in edible terrestrial plant and animal species were determined from gamma radiation measurements performed on samples obtained on land near the Susquehanna River. Samples were taken from gardens, game birds, and animals; and 4. Aquatic food: In a similar fashion to terrestrial measurements, radionuclide concentrations were measured in edible aquatic plant and animal species including fish, mussels, snails, and crayfish.
RESULTS All the measured maximum monthly radionuclide concentrations are listed in Tables 2, 3, 4, and 5. The maximum concentrations were of the same order of magnitude as the average concentrations for all species measured over the years, with one exception. The exception is for 65Zn concentrations in periphyton. While the maximum 65Zn concentration listed in Table 2 is 3,439.5 ± 243.1 Bq kg−1, the average concentration is two orders of magnitude less at 81.4 ± 55.87 Bq kg−1 (Palms et al. 2007). Except for rare occasions, such as after the Chernobyl release, concentrations remained at similar levels over time. That is, increases in radionuclide concentrations were not observed. Concentrations were on the order of tens or hundreds of Bq kg−1.
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40
Be K 51 Cr 54 Mn 58 Co 59 Fe 60 Co 65 Zn 103 Ru 110m Ag 131 I 137 Cs 141 Ce 144 Ce 214 Pb 226 Ra 228 Ac 232 Th 239 Pu, 240Pu 241 Am
7
45.51±21.09 187.22±98.79 73.26±35.15 64.38±27.01 0.2257± 0.481±
340.77±139.5 605.69±349.6 1517±333 56.98±15.17 114.7±22.20 55.5±25.90 57.72±7.40 3439.5±243.1 999.37±10.36 27.75±14.07 41.44±17.39 33.30±22.20 6.66±2.96
Periphyton (Bq kg−1)
18.5±11.1
2.96±3.7
129.5±111.0
Amphipods (Bq kg−1)
Table 2. Waterborne radionuclide concentrations.
14.8±11.1 14.8±11.1 11.1±11.1 14.8±14.8
7.40±1.48 136.9±95.8
247.9±222
Aquatic insects (Bq kg−1)
18.5±11.1 11.1±3.7
7.77±3.7
109.52
40.7±18.5 851±333
Aquatic vascular plants (Bq kg−1)
31.45±3.70 92.5±37 48.1±14.8 33.3±7.4
8.14±6.29 9.62±2.59
11.01±22.2 370.1±11.1 17.76±0.00
Coarse sediment (Bq kg−1)
INTRODUCTION THIS STUDY compiled 25 y of actual radiation concentration measurements of species in many general categories of animals, plants, and other organic and inorganic matter. The presence of radionuclides measured in a species may have originated from a sorption process or direct exposure of any of the matter or organisms that become incorporated into the food web of the environment. Studies have been conducted for various radiation interactions with the environment (Haas et al. 1998; Simmonds *US Nuclear Regulatory Commission, retired, 11 Mills Road, Gaithersburg, MD 20877; †Partnership for the Delaware Estuary, One Riverwalk Plaza, Suite 202, Wilmington, DE 19801; ‡Academy of Natural Sciences of Drexel University, Patrick Center for Environmental Research, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103; §Distinguished Professor Emeritus, University of South Carolina, Office of the President, Columbia, SC 29208. The authors declare no conflicts of interest. For correspondence contact: Charles Harris, 11 Mills Road, Gaithersburg, MD 20877, or email at [email protected]. (Manuscript accepted 25 November 2014) 0017-9078/15/0 Copyright © 2015 Health Physics Society DOI: 10.1097/HP.0000000000000266
1998; Voigt et al. 2000). In recent years, even more detailed and sophisticated studies have been undertaken (Camplin and Jenkinson 2007). Among such efforts, this study has several unique aspects, including a span of 25 y with monthly measurements; data collected in Pennsylvania from the 1986 nuclear accident in Chernobyl, Ukraine; measurements after the reactor core meltdown at the Three Mile Island nuclear plant; and samplings taken from a very large variety of animals, plants, and inorganic materials. The map in Fig. 1 depicts many (not all) of the monitoring stations in the Susquehanna River and in the surrounding land areas near the PPL Susquehanna Steam Electric Station (SSES). Radiation monitoring was also performed directly upstream and downstream from the TMI nuclear power plant. Table 1 is a listing of when each of the species was surveyed with some notes to further describe the categories listed. Monitoring included measuring radionuclide concentrations in air, water, diatoms, and foods such as meat, fish, fruits, and vegetables. The Academy of Natural Sciences (ANS)** in Philadelphia, PA, led this monitoring program (Patrick and Palms 1983–2003). Sampling began before the first PPL Susquehanna plant start-up and continued through the next 24 y of the power plant’s operation. The entire ANS environmental program includes a wide variety of aquatic and terrestrial plants, animals, and inorganic matter. Two previous Health Physics Journal publications describe much of this environmental radiation monitoring in much more detail (Palms et al. 2007; Patrick et al. 2007). A complete treatment of the entire 25‐y data set for periphyton was given, including the relationship to anthropogenic monthly power plant releases. Also, a detailed explanation of Chernobyl 1986 fallout in the Susquehanna River was explained therein. Several of the best bioaccumulator substances presented in this current paper (periphyton, lichens, flocculated sediment, and litter-humus) were already given greater attention in the 2007 publications.
** The Academy of Natural Sciences is now the “Academy of Natural Sciences of Drexel University.”
www.health-physics.com
503
Copyright © 2015 Health Physics Society. Unauthorized reproduction of this article is prohibited.
504
Health Physics
May 2015, Volume 108, Number 5
Fig. 1. Years when species were monitored.
The list of materials studied includes the following: periphyton, flocculated sediment, litter humus, lichens, fish flesh, fish muscle, mussels, snails, crayfish, insects, mushrooms, squirrels, deer, cabbage, tomatoes, coarse sediment, plastic bags, sticky paper, bee pollen, honey, aquatic vascular plants, amphipods, beans, corn, lettuce, Swiss chard, potatoes, carrots, canopy leaves, and fertilizers. The entire database of these thousands of measurements is compiled at the Academy of Natural Sciences of Drexel University
(Patrick et al. 1979–1982; Patrick and Palms 1983–2003). The collected data were sorted into four categories: 1) inedible materials in air contact, 2) terrestrial edible plants and animals, 3) aquatic edible food sources, and 4) aquatic inedible materials. MATERIALS AND METHODS Table 1 is a condensed summary of the several hundred taxonomic species, materials, chemicals, and other inorganic
www.health-physics.com
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Radionuclide concentrations near a power plant c C. HARRIS ET AL.
and organic compounds and mixtures that were sampled. For example, one species is called mussels. However, strophitus undulates, lampsilus cariosa, and elliptio complanata are only three of eight taxonomic mussel species sampled in 2001. Various trees and shrubs contribute to litterfall and humus, but for the single category called “litter-humus,” samples actually included material from 46 varieties of trees and shrubs. A final example of the large number of actual species is periphyton. Periphyton includes over 300 varieties of diatoms. Descriptions of the most important of the species follow. For a complete description of the taxonomy of the plant and animal species and other materials, one may refer to the 25 annual reports by Patrick et al. (1979–1982) and Patrick and Palms (1983–2003). As indicated in the Fig. 1 map, Ricketts Glen State Park is a pristine environment far north and far upstream from any likely nuclear contaminants from the SSES. Therefore, the park was selected as an overall control station. The following sections give a listing of brief definitions and descriptions of the major substances, plants, or animals that were measured for radionuclide concentrations. Aquatic studies Periphyton refers to a large variety of aquatic organisms growing attached to a surface. Such organisms include bacteria, algae, protozoa, and microscopic multicellular animals. Included among periphyton are some 300 varieties of diatoms in the Susquehanna River. Radionuclide gamma activity was measured in periphyton every month for the entire 300‐mo duration of the project. Flocculated river sediment (floc) consists of organic and inorganic particles transported into and along riverbeds via erosion and runoff. Radionuclides bound in terrestrial or aquatic organisms may enter into flocculated sediment in detritus, including both fecal matter and carcasses. Aquatic snails are mollusks that graze mainly on periphyton and organic detritus. In turn, some snails are consumed by fish. Snails are efficient accumulators of manmade radionuclides. Snails were continuously monitored between 1990 and 1997 and again in 2001. Aquatic vascular plants are consumed by a variety of aquatic fauna. These plants have been shown in some ecosystems to be accumulators of heavy metals and radionuclides (Domotor and McLean 1989; Whicker et al. 1990). Vascular plant species included western waterweed (elodea nuttallii), water stargrass (heteranthera dubia), American water willow (justicia americana), and pondweed (potamogeton sp.). Larval forms of aquatic insects provide a vital food web link between algae, detritus and other benthic organisms, and fishes. Nymphal and larval stages of insects appear to have an accumulation mechanism beyond a simple sediment association (Whicker et al. 1990). Because of this food chain relationship, aquatic insect larvae are potential
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transporters of radioactive materials to fish and, ultimately, to humans. Dobson fly larvae (hellgrammites), mayflies (both the heptogenidae and the isonychia genera), and caddisflies (hydropsychids) were aquatic insects included in this program. Crayfish are also accumulators of radioactive materials (Domotor and McLean 1989). As omnivores and scavengers, they feed on a variety of components in the food web and are also readily consumed by many fishes. Bivalve mollusks, or mussels, are known to accumulate heavy metal radionuclides efficiently (Goldberg et al. 1978). Their main sources of nutrition are algae, small zooplankton, detritus, and bacteria. During 2001, a composite sample of native freshwater mussels from the Susquehanna River was collected to examine whether radionuclides could be accumulated over longer times than previously studied in transplanted mussels. In addition to tissue analysis, the mussel shell material was also analyzed. Fish provide a direct radiological dose-to-human pathway because they are consumed directly. Representative species of carnivorous, omnivorous, and bottom-feeding fish were collected to obtain composite muscle tissue samples. Species sampled included the scavenger Northern Hogsucker (Hypentelium nigricans), Smallmouth Bass (Micropierus dolomiew), Carp (Cyprinus carpio), and Bluegill sunfish (Lepomis aurilus). Adult fish and fish larvae samples were collected. Since radionuclides may enter free-ranging fish at various locations, an experiment was also performed on fish in a fixed caged. Amphipods comprise a wide variety of both marine and freshwater crustaceans. They are important herbivores, detrivores, and scavengers because they inhabit almost all areas of rivers, lakes, and seas (Holsinger 1972). Samples taken in this study were not dissected for complete classification; rather, they were considered as one grouping of gammaridean amphipods. Although aquatic studies concentrated on species in contact with river water, some measurements were made of lake water in the vicinity. These values were considered as control measurements, which did not receive power plant effluents containing anthropogenic radioactive materials. Terrestrial plant and soil studies Canopy leaves atop the forest may accumulate fallout from nuclear weapons or atmospheric releases from a nuclear plant. To monitor effects after the 1986 Chernobyl accident, the canopy leaves of several tree species were collected during the 1986, 1987, and 1988 growing seasons. A lichen is a composite organism, consisting of a fungus and an alga or cyanobacterium, living in symbiotic association. Many lichens are extremely sensitive to metals uptake from atmospheric pollution and have been used as pollution indicators (Richardson 1992).
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FOOTNOTES: (1) Chernobyl accident of 1986—a special measure of periphyton was initiated, repeated in 1991.
Amphipods Aquatic Insects Aquatic Vascular Plants Aqueous Snails Caged Fish Canopy Leaves Course Sediment Crayfish Deer (8) Filtration Plant Precipitates Fish Flesh Fish Muscle/Kidney/Liver Flocculated Sediment Garden (11) Garden Additions Glass Beads Grid Soil Samples Honey Honeybees In Situ Soil Tests Lichens Litter Humus Mammal Food (4) Mammal Tissue (2) Mussel Shells Mussels Pasture Grass Periphython Plastic Garbage Bags Pollen Radio Carbon Analysis (6) Regular Crops Soil (Surface) Soil Core Sr and Transuranics Sticky Paper Synthetic Resin Beads Vegetation (7) Wood
1979 1980 1981
Table 1. Years when species were monitored.
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(2) Mammal Tissues include: Squirrels, rabbits, and woodchucks (3) Mammal Tissue: For 1989–1992 includes only squirrels; 2000 includes squirrels, turkeys, and grouse (4) Mammal Food includes mushrooms, which were sampled separately from 1988 onward. (5) Because of the Chernobyl accident of 1986, monthly samples, as well as an annual sample at harvest were taken. (6) Potato leaves and tubers were analyzed. (7) Includes; Trees, saplings, seedlings, shrubs, herbs, and ground cover, at Quarry Hill location. (8) In 1980 and 1986, sample data were provided by Radiation Management Corporation. (9) Data by Radiation Management Corporation (10) Drought; No mushroom crop. (11) Garden: Lettuce, Cabbage, Chard, beans, tomatoes, corn, potatoes, carrots and soil. Plant parts include: leaf, stem, fruit, and root tubers. (12) Additives include: Grass seed, bean seed, corn seed, annual ryegrass, potato seed, cabbage plants, cabbage roots, tomato plants, tomato roots, 5-10-5 fertilizer 10-10-10 plant food, tri-phosphate fertilizer 0-44-0, Start and Grow fertilizer 16-32-16, ammonium nitrate 35%N fertilizer, fertilizer lime, dolomitic lime fertilizer, dolomitic limestone fertilizer, liquid nitrogen fertilizer, soda fertilizer 16-0-0, 46-0-0 fertilizer, 0-44-0 fertilizer, 10-10-10 fertilizer, 5-10-5 plant food fertilizer, Thomasville pulverized limestone fertilizer, lime, 0-25-25 plant food fertilizer chlorothalamil pesticide, liquid dylox pesticide (Gypsy Moth Spray), Malathion methoxychlor pesticide, captan vegetable dust, carbaryl mareb pesticide, mareb-Seven pesticide, dacthal herbicide, krenite herbicide (13) Cow manure, 0-46-0 garden fertilizer, 0-0-60 fertilizer. (14) Samples include: lichens, moss, and ferns (15) Samples include: lichens, and substrate rock.
Radionuclide concentrations near a power plant c C. HARRIS ET AL.
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Decaying fallen leaves from trees and plants are called litterfall. Humus results from the breakdown of plant material. Litter-humus is a term used to describe litterfall and humus as a combined radioactive material biomonitor. Trees and shrubs contributing to the Pennsylvania litter-humus included black oak, white oak, maple, and black birch. In all, 46 individual species of trees and shrubs were identified in the sampling areas. Mushrooms were originally sampled and included with other mammal foods as an annual harvest. From 1988 onward, mushrooms were sampled separately. Also, following the Chernobyl accident, monthly samples were taken during 1986, as well as the annual harvest sample. For several years in the 1980s, as seen in Table 1, two gardens were planted by ANS researchers on the grounds of the PPL Susquehanna power plant. The gardens were strategically located to monitor the prevailing winds over the power plant. Garden vegetables included lettuce, cabbage, Swiss chard, beans, tomatoes, corn, potatoes, and carrots. Grass seed, bean seed, corn seed, annual ryegrass, potato seed, cabbage plants, cabbage roots, tomato plants, and tomato roots were also analyzed. Fertilizers and pesticides were also studied. These garden additives included: cow manure, ammonium nitrate, lime, dolomitic lime, dolomitic limestone, Malathion, and some 20 other pesticides and fertilizers. In situ gamma-ray spectrographic soil studies were performed each year from 1980 through 1987, yielding estimates of the concentrations of gamma-emitting radionuclides in the soil and their associated exposure dose (Coleman et al. 1976; Tanner et al. 1985). Terrestrial animal studies The quantities of radioactive materials in mammals were examined. Tissue sources included deer, squirrels, rabbits, black bears, and woodchucks. Two bird species, turkey and grouse, were also sampled. In 1980 and 1986, radionuclide concentration data from hunted deer tissue were provided by Radiation Management Corporation of Philadelphia, PA††. Honey, pollen, and bee samples were collected and measured. Pollen and honey have been shown to be suitable biological indicators of radioactive trace elements in the environment. (Kirkham and Corey 1977; Gilbert and Lisk 1978). Inorganic studies Several public water supplies obtain water directly from the Susquehanna River. Therefore, some water sampling stations were established at public water supply intake locations. Also, water filtration plant precipitates were analyzed. Periphyton does not grow well in winter weather, so in 1992 and 1993, studies of ion-exchange chelex and stator †† The address at the time of measurement was: Radiation Management Corporation, 3508 Market Street, Philadelphia, PA, USA, 19104.
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resin beads were conducted as a test alternative. The ionexchange materials could absorb radioactive materials in a manner similar to periphyton. Also, glass beads having a minimal materials uptake rate were examined as a control in 1993. Glass was used to verify that resin bead radioactive material uptake measurements were actually from waterborne sources and not from materials already mixed in with the resin. It is reasonable that radioactive materials may be present in the atmosphere and possibly deposited on land (or water) or inhaled. Therefore, some monitoring was done using sticky paper. With this paper, depositions of airborne inorganic (and organic) matter were taken occasionally. Experimental procedures Radionuclides measured. Only gamma-ray emitting radionuclides were measured. Radionuclides near PPL Susquehanna can come from several sources, including naturally occurring, anthropogenic from the nuclear plant or medical sources, and fallout from weapons testing. The radionuclides considered in theses analyses included: 7 Be, 14Be, 40K, 51Cr, 54Mn, 58Co, 59Fe, 60Co, 65Zn, 103Ru, 110m Ag, 129I, 131I, 134Cs, 137Cs, 140Ba, 141Ce, 144Ce, 210Pb, 214 Pb, 226Ra, 228Ac, 232Th, 239Pu, 240Pu, and 241Am. Sampling. Various sites along the Susquehanna River were sampled, both upstream and downstream from the PPL nuclear power plant. Terrestrial and aquatic control stations were located far from the other sampling stations. Minimum detectable activities, minimum detectable concentrations, calibration, and statistical methods are detailed by Coleman et al. (1984). Materials and methods for terrestrial and aquatic studies are extensively detailed by Patrick and Palms (1983-2003), but some brief descriptions of representative sampling methods are given below: • Periphyton were collected on glass slide diatometers. After drying, samples were analyzed for radionuclide content using gamma spectroscopy; • Flocculated sediment was vacuumed from various surfaces on the river bottom, filtered, and dried; • Lichens were collected from rocks in forest sites. Locations varied from year to year, and the number of locations ranged from five to 11 sites; • Samples of litter-humus were collected in the fall months. Square grid sections of a set depth were laid out in areas exposed to the open sky; and • Fish, deer, and other river and land animals were caught to obtain tissue, shell, or other cellular samples. Radiometric analysis. Since periphyton was the only species collected in each of the 300 months, it is used here as a more detailed example of analyses: Glass slide diatometers were placed in the river and collected on a monthly basis. The periphyton were scraped
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into a petri dish using a rubber policeman and dried in a laminar flow oven at 90-95 °C, then pulverized. Samples of approximately 0.5 to 20 grams were analyzed in a petri dish, using a high-resolution gamma-ray spectrometer. All of the measured species were sorted into four categories: 1. Inedible materials contacting air: All inedible non-aquatic species were grouped together. These materials, such as canopy leaves, trees, shrubs, surface soil, and sticky paper were all in contact with the air. Of course, airborne particles are not the only possible source of radionuclides within these materials; 2. Waterborne inedible species and materials: Periphyton was found to be the best bio-accumulator of radioactive metals in the Susquehanna River (Patrick et al. 2007; Palms et al. 2007). Flocculated sediment of the riverbed is also a good bio-accumulator in contact with the river water. A difference between periphyton and floc is that periphyton was collected on glass slides near the water surface, while much of the floc content comes from runoff, detritus, and fecal matter. Therefore, waterborne radioactive materials are the sole contributors of radionuclides for periphyton, but that is not so for flocculated sediment. Other inedible samples in the river included amphipods, coarse sediment, mussel shells, and aquatic vascular plants; 3. Terrestrial food: Radionuclide concentrations measured in edible terrestrial plant and animal species were determined from gamma radiation measurements performed on samples obtained on land near the Susquehanna River. Samples were taken from gardens, game birds, and animals; and 4. Aquatic food: In a similar fashion to terrestrial measurements, radionuclide concentrations were measured in edible aquatic plant and animal species including fish, mussels, snails, and crayfish.
RESULTS All the measured maximum monthly radionuclide concentrations are listed in Tables 2, 3, 4, and 5. The maximum concentrations were of the same order of magnitude as the average concentrations for all species measured over the years, with one exception. The exception is for 65Zn concentrations in periphyton. While the maximum 65Zn concentration listed in Table 2 is 3,439.5 ± 243.1 Bq kg−1, the average concentration is two orders of magnitude less at 81.4 ± 55.87 Bq kg−1 (Palms et al. 2007). Except for rare occasions, such as after the Chernobyl release, concentrations remained at similar levels over time. That is, increases in radionuclide concentrations were not observed. Concentrations were on the order of tens or hundreds of Bq kg−1.
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Be K 51 Cr 54 Mn 58 Co 59 Fe 60 Co 65 Zn 103 Ru 110m Ag 131 I 137 Cs 141 Ce 144 Ce 214 Pb 226 Ra 228 Ac 232 Th 239 Pu, 240Pu 241 Am
7
45.51±21.09 187.22±98.79 73.26±35.15 64.38±27.01 0.2257± 0.481±
340.77±139.5 605.69±349.6 1517±333 56.98±15.17 114.7±22.20 55.5±25.90 57.72±7.40 3439.5±243.1 999.37±10.36 27.75±14.07 41.44±17.39 33.30±22.20 6.66±2.96
Periphyton (Bq kg−1)
18.5±11.1
2.96±3.7
129.5±111.0
Amphipods (Bq kg−1)
Table 2. Waterborne radionuclide concentrations.
14.8±11.1 14.8±11.1 11.1±11.1 14.8±14.8
7.40±1.48 136.9±95.8
247.9±222
Aquatic insects (Bq kg−1)
18.5±11.1 11.1±3.7
7.77±3.7
109.52
40.7±18.5 851±333
Aquatic vascular plants (Bq kg−1)
31.45±3.70 92.5±37 48.1±14.8 33.3±7.4
8.14±6.29 9.62±2.59
11.01±22.2 370.1±11.1 17.76±0.00
Coarse sediment (Bq kg−1)
