We did re-analyze some of our samples from the West Coast that contained Fukushima cesium, and have not detected any additional strontium This new result makes sense, as the amount of strontium measured in the ocean near Fukushima was 40 times lower than cesium. This supports our idea that contaminated waters in the western Pacific today originated from near Japan 5 years ago. Plutonium was also released from Fukushima, but in concentrations even lower than strontium.
At the moment, concentrations of plutonium in waters off Fukushima are so low that background radiation from nuclear weapons testing more than 50 years ago makes the signal undetectable with our instruments. Japanese scientists using extremely sophisticated equipment have documented plutonium on land near the reactors at levels one million times lower than cesium in the same sample.
Where does radiation from Fukushima go once it enters the ocean? The spread of cesium once it enters the ocean can be understood by the analogy of mixing cream into coffee. At first, they are separate and distinguishable, but just as we start to stir, the cream forms long, narrow filaments or streaks in the water.
In the Pacific, streaks of contaminants become longer and narrower as they move offshore, where diffusive processes begin to homogenize and dilute the radionuclides. Currents then mix and continue to dilute the cesium as it travels across the ocean and, with distance and time, radionuclide concentrations in seawater decline. Is radiation a concern along U. Although we have found traces of radioactive contamination from Fukushima in samples collected through our citizen-science initiative Our Radioactive Ocean, the concentration of cesium and in these samples is well below levels of concern for humans or marine life.
Swimming every day in the ocean there would still result in a dose 1, time smaller than the radiation we receive with a single dental x-ray. Not zero, but still very low. Looking ahead, levels of any Fukushima contaminants along the West Coast of North America are predicted to peak around or , but at levels similar to what we are measuring in some of our samples today. This is not to say that we should not be concerned about additional sources of radioactivity in the ocean above the natural sources, but at the levels expected, even short distances from Japan, the Pacific will be safe for boating, swimming, etc.
Nevertheless, we continue to monitor levels of radiation up and down the West Coast through Our Radioactive Ocean. Has Fukushima been responsible for the deaths of marine animals in the Pacific? To date, there have been no reliable links made between radiation in the Pacific and mass die-offs of marine mammals, birds, fish, or invertebrates. Some of these die-offs have been attributed to viruses, warming water, and other changes to the marine environment that need to be addressed.
If there were effects from radioactive contamination, we would expect to see the largest effects off Japan, not the West Coast of North America, and this has not been seen. How far can radiation travel? Ionizing radiation itself cannot travel very far through the air. Typically, dust and other particles, seawater and other liquids, or even gases pick up radioactive contaminants that are then transported great distances.
In the months and years after the explosion at the Chernobyl nuclear power plant in Ukraine, scientists were able to track the spread of radioactive material in the atmosphere and the ocean around the globe. Within a week after the explosions at the Fukushima plant, there were reports of very small increases in radionuclides on the continental U.
If radioactivity from Fukushima was released into the atmosphere, should I be worried when flying? Immediately following the nuclear accident at Fukushima, radioisotopes were released into the atmosphere and were quickly carried around the globe by the wind. Gases and small aerosol particles dust are the main carriers of the radioactive materials. We detected extremely low levels in the atmosphere here on Cape Cod 10 days after the first releases, despite the distance from Fukushima. Iodine was the main isotope detected but it has a very short half-life 8 days so it disappeared very quickly.
The only population of concern would be those in close proximity to the accident and fortunately the wind blew most of this contamination offshore. These radioactive elements are generally carried by dust and fall quickly out of the atmosphere near the source via rain and settling, and are not a concern for flying in airplanes. When you fly in an airplane you are exposed to natural sources of radiation from cosmic rays emitted by the sun.
Exposure to these additional cosmic rays is not detectable in the health of pilots or those who spend a great deal of time flying. Is radiation exposure from the ocean and beach a concern? I stood on the deck of a ship l2 miles from the Fukushima reactors in June and was about one-half mile away as recently as October and the radiation detectors I was carrying showed little or no increase above background levels.
Even the samples I collected water, sediment, plants, and animals from these locations are safe to handle without any precautions. In fact, our biggest problem is blocking interference from background radiation in our samples so we can isolate the trace levels of cesium and other radionuclides that we know came from Fukushima.
On the West Coast of North America, radiation from the water, sediment, and biota is even less of a problem because of the distance from Japan and the dilution that occurs as the contaminants cross the Pacific. The greatest concern is for those who work on the site of the reactors because leaks from storage tanks could release water with high concentrations of contaminants. How does Our Radioactive Ocean measure radiation in seawater samples?
We use a method that is capable of detecting extremely low levels of the specific radioactivity produced by cesium isotopes released from Fukushima in seawater. First we pass a seawater sample through a column of cesium-absorbing beads made of a resin that has been optimized for use with seawater. Then we dry the resin and place it in a high-purity germanium well detector made by Canberra Industries for between 24 and 72 hours. By counting the decay events associated with each isotope, we can calculate the total counts per second cps for a given sample.
Knowing the efficiency of our detectors and something about the decay properties of the isotopes allows us to calculate the concentration of both cesium isotopes in a sample.
We regularly participate in proficiency tests with the International Atomic Energy Agency IAEA to ensure that our results are not just precise, but extremely accurate when compared to international seawater standards. I have a Geiger counter. Can I use it to detect radiation from Fukushima? There are two basic types of radiation detectors—those that measure only the number of times radiation interacts with the instrument, and those that measure the energy level in electron volts of the particles or waves detected by the instrument.
The Geiger-Mueller tube Geiger counter is perhaps the most widely known radiation detector and falls into the first category. Geiger counters can measure beta particles and gamma rays the detector window will block most alpha particles , but cannot distinguish between the two.
These interactions, and the decay events that trigger them, are registered as counts or audible clicks. All forms of nuclear radiation travel in invisible rays, some rays are weak and would not pass through a piece of paper, but other rays can pass straight through metal. In the same way some rays can pass into our bodies, or be eaten or breathed in - but other rays are too big and cannot. So, it is this invisible radiation which is causing worry, as it can spread miles and miles in the form of clouds, affecting other countries.
Since low levels of radioactive waste have been discharged into the Irish Sea, the English Channel and the Arctic Ocean.
It is recognised that radioactive material needs to be isolated and encased in glass and concrete to prevent leakage on the ocean floor and it is now kept on land for some time whilst radioactivity levels decrease. What long term effects might this have on marine environments? Certainly radiation can enter the food chain though plankton and kelp and then go on to contaminate fish. He points out that similar anomalies have been observed in areas of heavy fallout and in uncontaminated areas.
Again, there can be no doubt that there was damage and even the destruction of individual plants by radiation; but the spe- cific examples of damage or killing caused by radiation or by other factors, or in combination with other factors, can- not be sorted out.
The important point is that although in- dividuals may be debilitated or destroyed, the ecosystem recovers. The land-dwelling hermit crab, Coenobita sp. The levels of 90Sr and Cs were found to remain virtually constant at 4, pCi of 90Sr per gram of skeleton and pCi of Cs per gram of muscle in Coenobita sp.
Parallel studies of Birgus sp. No gross anomalies were noted among these crabs, and no obvious population changes were noted during this fallout period; however, population studies as such were not made.
The vegetation, exclusive of roots, taken from an area 10 m in diameter in a Scaevola sp. The abundance and size of fish and of spiny lobsters and coconut crabs at Bikini Atoll appear to be greater than ever, which does not, of course, reflect a beneficial effect of radiation but presum- ably results from the absence of predation by man.
Irish Sea Apart from the Pacific Proving Grounds, the Irish Sea coastal area adjacent to the Windscale reprocessing plant of the United Kingdom Atomic Energy Authority probably represents the most important area known with respect to the degree of contamination in the marine environment Mauchline and Templeton, Studies of the relationships between radionuclides and man have been of prime importance; some studies, though limited, have considered effects of radiation in the environ- ment.
Morgan reported that effects of radiation had been sought in plaice Pleuronectes platessd caught in the region of the Windscale discharge, but none has been estab- lished so far. The area, which had been carefully surveyed before and after discharges began, showed that there were no changes in bottom organisms that could be ascribed to the effects of the discharge.
Calculations Dunster et al. The concentration of these radionuclides in the egg can now be calculated for any concentration of the radionuclides in seawater to which they may be exposed. Tentative conclu- sions have been drawn that the dose rate to the eggs of plaice from the contaminant activity in the spawning areas off St. Bees Head, near Windscale, was 9. Studies have also been made of the radiation dose re- ceived by fish in the Windscale discharge area Ministry of Agriculture, Fisheries and Food, The plaice, Pleuro- nectes platessa, is a seabed resident and is known to spend its early life, up to the beginning of its third year, inshore.
In the calculations, allowance was made for fish movement and type of bottom, and these indicated that an annual dose of 7. The seawater and internal radionuclides would only contribute about 1 percent of the total expected dose Table 6. The annual dose might increase to rads if the fish spent the whole year close to the pipeline outlet on a silty bottom.
This calculation suggested that the use of thermolumi- nescent dosimetry was warranted, and 2, marked plaice were released in the vicinity of the outfall in Ministry. Each fish carried two lithium fluoride dosimeters, incorporated in a Petersen fish tag, one to measure the accumulated dose on the upper surface and one to measure the dose on the under surface.
In the first few months, over marked fish were recov- ered, and preliminary data indicated an integrated exposure of 4. This was equivalent to a dose of 10 R per year. The ratio of top to bottom dose was 0. The differential response of dosimeters placed on the top and the underside of the fish indicated the expected re- sponse to beta radiation. The agreement between calculated and measured dose is extremely good.
Organisms in the top 3 in. Oak Ridge Very few studies have been made of natural populations ex- posed to chronic radiation higher than background. The salivary chromosomes of the larvae ofChironomus tentam, which inhabit the contaminated bottom sediments of White Oak Creek and White Oak Lake at Oak Ridge National Lab- oratory, were analyzed for 5 years for chromosomal aber- rations Blaylock, More than generations had been exposed to this or greater dose rates over the previous 22 years.
The conclusion was that the ionizing radiation from the contaminated en- vironment was increasing the frequency of new chromo- somal aberrations in the irradiated population, but that the new aberrations were eliminated by natural selection. Also, the present level of chronic irradiation has not affected the frequency of the endemic inversions. Blaylock also studied the fecundity of a natural population of fish, Gambusia affinis affinis, that had been exposed to chronic irradiation in White Oak Creek for many generations, compared with a control population.
The calcu- lated dose rate from the bottom sediments was A significantly larger brood size occurred in the irradi- ated than in the nonirradiated population, although signifi- cantly more dead embryos and abnormalities were observed in the irradiated broods. These results suggest that an in- creased fecundity is a means by which a natural population having a relatively short life cycle and producing a large number of progeny can adjust rapidly to an increased en- vironmental stress caused by radiation.
We return then to a concept that has recurred in this report: Man, as an individual, is the critical biological target in predicting the consequences of introducing radioactive materials into marine environments. If the radionuclides are present in concentrations acceptable for man, the individual, then it is difficult to conceive that there will be more than subtle effects on ecosystems-perturbations that would probably be indistinguishable from those due to causes other than radiation.
On the other hand, it is not only con- ceivable, but probable, that with increasing uses of atomic energy, accidents will occur that will result in damaging con- centrations of radionuclides.
In preparation for these con- tingencies, there is a pressing need to increase the sensitivity of methods for studying the response to radiation of popu- lations and ecosystems in the marine environment. EFFECTS ON RESOURCES The extrapolation of the results of laboratory experiments into the practical terms of their effects on marine resources must be made with care since, without evaluation of the natural variations related to changes in fecundity, mortality, and recruitment, quite erroneous conclusions can be reached.
Polikarpov suggests "inhibition and degen- eration of a number of food fishes and other radio-sensitive organisms" and "rapid development and multiplication of. Zaytsev and Polikarpov and Polikarpov , based on their previously discussed laboratory data, have calculated the time needed to halve the stocks of various species of Black Sea fishes in relation to the proportion of the eggs damaged by radiation.
These workers conclude that there is reason to assume that the fisheries will be adversely affected, and may, in many instances, cease to function if fish stocks are reduced to one half or less. They consider that from the commercial standpoint, radiation damage must not affect more than 10 percent of the eggs, though even at this level, catches will be perceptibly reduced.
Garrod points out the fallacy of this argument. For marine mammals or for certain fish species with low fecundity, a 50 percent mortality of the young or of the eggs will be reflected as a 50 percent reduction in recruits to the stocks, though this does not generally occur in the marine environment.
In the general case of organisms with high fecundity, reduction in the spawning stock does not necessarily result in a decrease in the number of recruits. The capacity of the environment to support young fish is limited, and this capacity can be satisfied by the eggs from a small number of adults, the superfluous eggs and larvae being reduced by density-dependent mortality.
The magnitude of the mortality is also pertinent in the evaluation of the effects of radiation on marine resources. Garrod indicates that for stocks of arctic cod with high fe- cundity, survival is 1 in and can be as low as 1 in The addition of 50 percent mortality in the egg stage due to the effects of radioactive contamination of the environment would not noticeably alter the existing mortality rate of This would also be true of all highly fecund species.
While it may be true that the fecundity of both the indi- vidual and the population could be reduced by radiation ef- fects, it is extremely doubtful that these would influence stock size beyond the normal range related to environmental changes, except in very heavily exploited stocks. It is cer- tain, however, that with the techniques of assessment now available, it would not be possible to obtain an unbiased measure of the effect attributable to radiation alone.
The effects of other environmental "stress" factors, such as salinity, temperature, oxygen, and pollutants, must be studied and expanded to include the interaction of these factors with radiation effects. Long-term studies, in which factors such as rates of growth, morphological abnormalities, onset of maturity, and repro- ductive capacity are considered, for example, should be em- phasized.
Chromosomal studies under experimental and field conditions should be extended, and the somatic and genetic consequences of such changes on populations and ecosystems should be evaluated. In areas subject to radioactive contamination, studies should be initiated to determine the radiation regime in the environ- ment.
The data obtained should be closely correlated with measurements of concentration of radionuclides in order that the historical radiation regime can be determined.
SUMMARY Radiation is not a recent introduction to the marine environ- ment, since low levels from environmental and cosmic sources have been present throughout geological time. Lethal amounts of acute radiation differ widely among ma- rine organisms and are related to variations such as species, age, physiological status, and body size.
These variations are further complicated by the interaction of environmental fac- tors such as temperature and salinity. Exclusive of the eggs of fish and larvae of invertebrates and fish, most marine or- ganisms for which data exist are relatively radioresistant. Limited studies on the effects of chronic exposure have been conducted.
These have been limited to selected devel- opmental stages and indicate that, with the possible excep- tion of some Russian data, the dose necessary to evoke an unequivocally detectable biological response is considerably above that of concentrations of radionuclides in the environ- ment as a result of controlled waste disposal operations.
Studies on the genetic consequences of radiation expo- sure to population indicate that, despite larger numbers of mutations, increased utilization of reproductive capacity maintains a population at preradiation density. Field studies on the effects of radiation indicate that our best technologies and methods cannot demonstrate effects on marine ecosystems, at prevailing dose rates, that are clearly and uniquely attributable to ionizing radiation. Dose-rate distributions from spherical and spherical-shell radiation sources, with special reference to fish eggs in radioactive media.
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Fosberg, F. Long-term effects of radioactive fallout on plants? Share sensitive information only on official, secure websites. JavaScript appears to be disabled on this computer. Please click here to see any active alerts. The EPA does not monitor or sample ocean waters.
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