# manuscript_230720-arxiv

Sebastien Philippe

Fallout from U.S. atmospheric nuclear tests

in New Mexico and Nevada (1945-1962)


Sébastien Philippe1,*, Susan Alzner2, Gilbert P. Compo3,4, Mason Grimshaw5, Megan Smith2


1 Program on Science and Global Security, Princeton University, Princeton, New Jersey 2 shift7, Washington, District of Columbia

3 Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado

4 Physical Sciences Laboratory, NOAA, Boulder, Colorado 5 The Earth Genome, Los Altos, California


* Correspondence to: sebastien@princeton.edu


Abstract

One hundred and one atmospheric nuclear weapon tests were conducted between 1945 and 1962 in the United States, resulting in widespread dispersion of radioactive fallout, and leading to environmental contamination and population exposures. 1,2,3,4,5,6 Accurate assessment of the extent of fallout from nuclear weapon tests has been challenging in the United States and elsewhere, due to limited monitoring and data accessibility.1,4,5,6

Here we address this deficit by combining U.S. government data,2,3 high-resolution reanalyzed historical weather fields,7 and atmospheric transport modeling to reconstruct radionuclide deposition across the contiguous United States, 8 with 10-kilometer spatial and one-hour temporal resolution for five days fol owing detonation, from all 94 atmospheric tests detonated in New Mexico and Nevada with fission yields sufficient to generate mushroom clouds. Our analysis also includes deposition estimates for 10 days fol owing the detonation of Trinity, the first ever nuclear weapon test, on July 16, 1945.

We identify locations where radionuclide deposition significantly exceeded levels in areas covered by the U.S. Radiation Exposure Compensation Act (RECA).9 These findings include deposition in all 48 contiguous U.S. states. They provide an opportunity for re-evaluating the public health and environmental implications from atmospheric nuclear testing.

Finally, our findings also speak to debates about marking the beginning of the Anthropocene with nuclear weapons fallout.10,11 Our deposition estimates indicate that direct fallout from Trinity, a plutonium device, reached Crawford Lake in Canada, the proposed “golden spike” site marking the beginning of the Anthropocene epoch,12,13 starting on July 20, 1945.


1


MAIN

Atmospheric nuclear weapon testing beginning in 1945 led to unrestrained releases of radioactive materials in the environment. These materials were transported and dispersed in the atmosphere by prevailing winds and have historically been the most significant cause of exposure of the world population to human-made sources of radiation.1 The deposition of these materials, including plutonium 239 and 240, is now considered a potential geological marker for the beginning of the Anthropocene Epoch.10,11

Among the one hundred and one atmospheric nuclear weapon tests carried out in the contiguous United States between 1945 and 1962, ninety-four generated radioactive mushroom clouds.2,3 The first test, Trinity, took place in New Mexico on July 16, 1945, and the other ninety-three in Nevada starting in January 1951. Monitoring of U.S. radioactive fallout across the contiguous United States was limited in time and scope, and as a result, efforts to reconstruct its extent have had to rely on reanalysis of historical data, remodeling, and interpolation.4–6 This has had consequences for an understanding of population doses and eligibility for compensation under the 1990 Radiation Exposure and Compensation Act (RECA).9

For example, the Trinity test, which is now believed to have been about 24.8 kilotons (kt) of TNT equivalent in yield,14 is not included as a source of possible exposure in this legislation.

Here, we compute the atmospheric transport, dispersion, and deposition of fallout across the contiguous United States from all 94 atmospheric tests that took place in New Mexico and Nevada between 1945 and 1962 and generated a radioactive mushroom cloud. Our analysis uses U.S. government data about the location, time, and yield of U.S. atmospheric tests,2,3 a stabilized radioactive mushroom cloud source term, 15,16 the U.S. National Oceanic and Atmospheric Administration (NOAA)’s HYSPLIT atmospheric transport and dispersion model,8

and ERA5, a high spatial and temporal resolution dataset of reanalyzed historical weather fields developed by the European Centre for Medium-Range Weather Forecasts for 1940-onwards, updated in March 2023.7

We produce the first long-range radionuclide ground deposition estimates for the first ten days after the 16 July 1945 Trinity test. For the 93 atmospheric tests exploded in Nevada, we produce long-range radionuclide ground deposition estimates for the first five days after each test. Thirty of these 93 Nevada tests were not included in previous fallout studies. These 30

tests had yields spanning 0.0002 to 22 kt, with 73.4 kt cumulative and 2.4 kt mean yields.

Overall, the results cover deposition of all fission products from all mushroom cloud producing atmospheric tests conducted within the contiguous United States with higher spatial and temporal resolution than previously available.

Our estimates indicate that there are locations in New Mexico and other states, including federally recognized tribal lands, where radionuclide deposition reached levels higher than that in counties covered by RECA. This analysis lays a basis for more directed re-evaluation of contamination and population exposure and its impact on public health and the environment.

The tools and approach presented here may also facilitate similar modeling of atmospheric testing programs in other nuclear weapon states for which little to no deposition density data may be available.


2


Finally, our findings contribute to broader debates about marking and locating the beginning of the Anthropocene using radionuclide deposition from nuclear weapon tests fallout. Our deposition estimates indicate that direct fallout from Trinity reached Crawford Lake in Canada, the proposed site for the Anthropocene Global boundary Stratotype Section and Point (GSSP),12,13 on July 20, 1945 before peaking on July 22, 1945.

FALLOUT MODELING

Our fallout simulation model uses the HYSPLIT Lagrangian atmospheric particle transport code integrated with weather fields from the ERA5 reanalysis project to track the dispersion and deposition of radioactive particles from a stabilized radioactive mushroom cloud source term.

The cloud particle composition is based on a model from the Department of Defense Fallout Prediction System (DELFIC) with assumed log-normal size distributions of micron-size silicate and metallic particles broken down into one hundred particle-size bins with equal activity such that the total cloud activity is normalized to 1 (unit release).17 Two sets of particle distribution parameters were used depending on whether each detonation was low (surface and tower) or high altitude (balloon or airdrop) (see methods).

The spatial extents and directions of fallout are dependent on daily and hourly changes in surface and high-altitude wind patterns aloft, as wel as local precipitation. The ERA5 reanalysis data set (1940-onwards) provides all the atmospheric parameters, including geopotential height, pressure, temperature, relative humidity, wind speed and direction, precipitation, and others, required to run HYSPLIT. ERA5 combines historical observations into globally complete estimates of the weather state using advanced modeling and data assimilation systems. To our knowledge, fol owing its March 2023 update, it is the only reanalysis data set including upper-air atmospheric observations that covers the entire 1945-1962 period. For the month of July 1945, it leverages ~2 mil ion global observations (about 60,000 per day), split about equally between surface and upper air measurements (see extended data figure 1 for a map of the observations included for July 16, 1945). The reanalysis fields are provided on a 0.25-degree grid with a 1-hour temporal resolution on 37 pressure and one surface level.

Particle deposition via gravitational settling or wet removal is computed on a 0.1-degree resolution grid spanning the entire contiguous United States (20 by 60 degrees centered at 37.0o N, 95.0o W). For each test, we tracked hourly particle deposition up to 5 days after detonation. Given its historical significance, we also simulated the fallout from Trinity for 5

additional days (total of 10 days). The results are then post-processed to obtain radionuclide deposition density.

Local deposition density is obtained for each test in two steps. The first step decays the activity generated from fission (assuming plutonium-239 fuel for each test) from the time of detonation to the time of arrival in each 0.1-degree latitude x 0.1-degree longitude grid cell, summed over all particle sizes. The second applies a correction factor as a function of the grid cel distance from ground zero, such that long-range deposition density estimates using DELFIC particle-size parameters can reproduce available reanalyzed experimental data, produced by the U.S.

Department of Energy and the National Cancer Institute (NCI), which is based on limited ground station measurements. The factors were obtained by benchmarking HYSPLIT estimates of iodine-131 deposition to the NCI reconstruction of nationwide (county-specific) total iodine-131


3


fallout deposition data from the Nevada Test Site at distances of 1500 to 3500 km from ground zero,6,18,19 covering the contiguous United States (see methods).

RESULTS

Fallout deposition density from U.S. atmospheric nuclear tests in New Mexico and Nevada We computed the dispersion and deposition of radionuclides produced by 94 non-zero yield atmospheric nuclear weapon tests across the contiguous United States. Six other atmospheric tests had zero yield and an additional one generated a yield of only ~36 grams of TNT, which did not generate a mushroom cloud. These seven tests were not simulated.

The first test, Trinity, was a tower test in New Mexico on July 16, 1945. The other 93 in Nevada consisted of 48 ground or tower tests and 45 airbursts, all between 1951 and 1962. Figure 1

shows the cumulative radionuclide deposition density map fol owing the first 5 days after each of the 94 atmospheric tests included in this study. Our map shows similarities to previously known features seen in past deposition density estimates that were based on only Nevada tests and limited measurement data gathered by the U.S. Department of Energy and the National Cancer Institute in the 1990s. 4,18,20 Unlike previous studies, our higher spatial resolution captures the deposition tracks produced by tower or surface explosions and some apparent influence of the Rocky Mountains.


Figure 1. Estimated deposition density (Bq/m-2) of fission products from 94 non-zero yield atmospheric nuclear tests conducted in New Mexico and Nevada, across the contiguous United States. The highest deposition points indicate the ground zeros of the Trinity test in New Mexico and of the 93 atmospheric tests in Nevada.


4


Trinity test

Our map also includes the contribution of the Trinity test to the cumulative deposition density across the United States. Our results show the significant contribution of the Trinity fallout to the total deposition density across the contiguous U.S. (reaching 46 states within 10 days) and in New Mexico in particular. This result is consistent with the low altitude of the detonation (~30 meters) and the yield of the Trinity test recently re-evaluated at 24.8 kilotons of TNT

explosive equivalent (representing ~5% of the total yield from all surface and tower shots in the contiguous U.S.).

Figure 2 shows a time sequence of maps of the Trinity deposition over the first 10 days fol owing detonation. Our reconstruction suggests that radioactive fallout from the Trinity explosion led to significant deposition on a north-east primary axis before reaching 46 states within 10 days. Only Washington state and Oregon show no deposition. Deposition also occurred south and west of ground zero within the first 48 hours, and after.


Figure 2. Estimated radionuclide deposition density from the Trinity test for the first 10 days after detonation on July 16, 1945 at 05:29 AM local time.

We find these results to be consistent with the few radiological and meteorological data available in the literature for this test. For example, our results for the first 24 hours agree with local fallout estimates produced as part of a 1987 NOAA analysis of Trinity also covering the first 24 hours (see figure 3).21 Our results are also consistent with the long-range contemporary detection of radioactive contaminants from Trinity in strawboard material for packaging sensitive photographic films, manufactured in Indiana and Iowa (see extended data figure 2).22


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Figure 3. Historical and simulated Trinity fallout dose rate contours for ground level at H+1

hour.

Finally, our deposition estimates also indicate that direct fallout from the Trinity test arrived at Crawford Lake in Ontario, Canada, on July 20, 1945 with a peak deposition on July 22, 1945 (see extended data figure 3 for a time series of plutonium deposition estimate). This would mark the first-time plutonium-249 and 240 deposited in the lake that is now proposed as the Global boundary Stratotype Section and Point to define the Anthropocene as a geological epoch – five years before the proposed base dated at 1950 CE.12,13

Deposition density and the Radiation Exposure Compensation Act Our total deposition density estimates across the contiguous United States have implications for public health and discussions about the 1990 Radiation Exposure and Compensation Act.

Aggregated by counties and federally recognized tribal lands, our total deposition density estimates show that there are locations in New Mexico, and in other parts of the United States, including Utah, Nevada, Wyoming, Colorado, Arizona, and Idaho, where radionuclide deposition reached levels larger than those we estimate in some counties covered by RECA. Total deposition density is a metric that reflects external exposure to radiation without accounting for internal contamination via the ingestion of contaminated water, fresh milk, and other foodstuffs.


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Figure 4. Deposition density distribution for counties and federally recognized tribal lands in the United States. (a) Deposition density for all counties (grey), RECA counties (red), and 549

federally recognized tribal lands, including tribal trust lands (orange). (b) Cumulative distribution function of county deposition density, with RECA and 33 the New Mexico counties.

Figure 4a shows the deposition density distribution for the 3108 counties and 549 federally recognized tribal lands (including tribal trust lands) in the United States and how they compare to deposition in areas covered by RECA. There are 38 federally recognized tribal land areas where estimated deposition levels are higher on average than the lowest county included in RECA. There are 27 higher than the second lowest county included in RECA. There are six in Nevada, Utah, Arizona, and New Mexico with levels comparable to the top 10 RECA counties.

Figure 4b shows how New Mexico counties lie on the county cumulative distribution function compared to RECA counties, given that ground zero for the Trinity test was in New Mexico and that no counties in New Mexico are covered by that Act. Our estimates indicate that there are locations in New Mexico where radionuclide deposition reached levels on par with Nevada, with levels in 28 of the 33 counties in New Mexico experiencing higher deposition levels on average than the lowest deposition level county covered by RECA. The New Mexico county within which the Trinity explosion took place – Socorro County – has the 5th highest deposition per county of all counties in the U.S. Al other counties in the U.S. with this level of deposition are included in RECA. Overall, the results indicate that there are a significant number of locations that experienced levels of deposition higher than areas covered in RECA.

Sources of uncertainties

There are multiple sources of uncertainties associated with our deposition density estimates that can be grouped in four categories: uncertainties about nuclear test data (fission fuel, yield, cloud dimensions), uncertainties about the particle source term, uncertainties about modeling and post-processing, and uncertainties about the meteorological data.

For the available nuclear test data, we are restricted to public information available in government reports and the literature. There are unknown uncertainties about yield. For example, the Trinity yield was recently reevaluated from 21 kt to 24.8kt of TNT equivalent. The exact composition of each test device remains unknown (except for Trinity, a plutonium 7


device). We have assumed that all tests were performed with plutonium-239. This assumption does not, however, significantly impact the overall fission activity generated by the tests.

Several factors influence the HYSPLIT results. For the source term, the particle size distribution and the cloud dimensions have the most influence on the HYSPLIT results. The DELFIC particle size parameters combined with the U.S. government cloud parameters that we used produce conservatively low long range deposition estimates. Because of the lack of experimental data on particle sizes and corresponding ground deposition density measurements in the literature, a systematic exploration of the particle-size parameter space is beyond the scope of this study.

Beyond the source term, underprediction may also be the result of multiple assumptions and models included in HYSPLIT, which have been noted elsewhere.23,24 For example, HYSPLIT

typically overestimates wet deposition from light rain. This would deplete the debris cloud more rapidly as it travels for several days and therefore cause an underestimation of deposition at corresponding distances downwind. In addition, HYSPLIT assumes particle sizes and densities to remain constant over time and may be underestimating their settling velocity once they reach lower altitudes. These two factors led us to develop a two-step post-processing approach that included correcting for the long-range underestimation of fallout deposition as described in the method section. Our estimates likely remain conservatively low, however. For example, we do not include deposition from activation products and unfissioned fissile materials.

DISCUSSION

This study presents an analysis of fallout for the first five days and first ten days after the Trinity test in New Mexico on July 16, 1945, and the first five days from each of the 93 atmospheric nuclear weapon tests conducted in Nevada between 1951 and 1962 that generated a mushroom cloud. It provides fission-product deposition-density estimates across the contiguous United States. The findings have implications for population exposure, contamination, public health, and the environment.

The analysis identifies locations in New Mexico and other states, including in federally recognized tribal lands, where radionuclide deposition exceeded levels in some counties covered by the Radiation Exposure Compensation Act (RECA). Our results demonstrate the significant impact of Trinity, the first nuclear weapon test, on the overall deposition density in New Mexico and across the contiguous U.S. They also indicate that fallout from Trinity crossed the Canadian border and reached Crawford Lake in Ontario, the proposed site marking the beginning of the Anthropocene epoch, less than a week after detonation.

While uncertainties remain in the nuclear test data, particle source term, modeling, and historical weather data, the results align with available information, including short-range measured and reanalyzed fallout patterns and contemporary observations of radionuclide contamination at long distances.

Overall, this research contributes to a better understanding of the extent of radioactive fallout from 94 atmospheric nuclear weapon tests in the United States and provides a methodology for similar studies of all 528 atmospheric nuclear tests that took place worldwide between 1945

and 1980. Finally, it also contributes to a better understanding of the processes, events, and places that are to possibly mark the beginning of the Anthropocene epoch.


8


Acknowledgements: The authors grateful y acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model used in this publication.

Hersbach, H. et al., (2023) was downloaded from the Copernicus Climate Change Service (C3S) (2023). The results contain modified Copernicus Climate Change Service information 2020. We thank H. Hersbach of the European Centre for Medium-Range Weather Forecasts (ECMWF) for providing the observations from their Observational DataBase. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains. The authors thank S. Chanock of the National Cancer Institute for providing nationwide (county-specific) total iodine-131 fallout deposition data from the Nevada Test Site. Cartographic boundary files for U.S. counties and federally-recognized tribal lands were obtained from the U.S. Census Bureau.

The authors thank Z. Statman-Weil, T. Ingold, M. Maron, and D. Hammer of the Earth Genome, for database engineering, architecture and implementation, GIS mapping and data visualization col aborations. The authors thank R. Sayer and B. Shander for col aboration on color science and visualization. We thank F. von Hippel and Z. Mian for useful discussions and feedback on the manuscript.

S.P. acknowledges funding through grants to the Program on Science and Global Security by the Carnegie Corporation of New York, the MacArthur Foundation, and the Ploughshares Fund. S.P., S.A., M.G., and M.S. were supported in part by a grant from Bezos Earth Fund. G.P.C. was supported in part by NOAA cooperative agreement NA22OAR4320151 and the NOAA Physical Sciences Laboratory.

Data availability: Al data generated or analyzed during this study are either included or cited in the published article and are available from the corresponding author upon reasonable request.

Nationwide (county-specific) total iodine-131 fallout deposition data from the Nevada Test Site is available from the U.S. National Cancer Institute. The ERA5 gridded meteorological data can be downloaded from the Copernicus Climate Change Service (C3S) (2023).

Code availability: The source code for the HYSPLIT transport and dispersion model is available upon request from the NOAA Air Resources Laboratory

(https://www.ready.noaa.gov/HYSPLIT_linux.php).

Competing Interest Statement: The authors declare no competing interests.

Authors contributions: SP conceptualized the research with SA and MS. SP conducted the source term evaluations, the atmospheric transport modeling, and the data processing. GP

conducted the meteorological data analysis with inputs from SP and SA. SP and MG performed data aggregation, cleaning, and analysis. MG, SA and SP developed data visuals. Al authors contributed to the manuscript.


9


METHODS

Source term, transport, dispersion, and deposition of fallout particles We modeled the dispersion and deposition of fallout from a stabilized nuclear debris mushroom cloud using the U.S. NOAA Hybrid Single-Particle Integrated Trajectory (HYSPLIT) particle transport and dispersion model (Linux version 5.2.0, January 2022),8,15 U.S. government data on key parameters for each test,3,14 and meteorological fields from the ERA5 reanalysis project (1940 – present, March 2023 update).7

Initial particle clouds were assumed to be stabilized ~10 minutes after detonation. They were represented as a segmented vertical linear source with activity distributed among the cap, skirt, and stem of the mushroom cloud as 0.775/0.15/0.075 for surface and tower tests and 0.9712/0.0283/0.0005 for all aerial tests (e.g., balloon, airdrop, …).

Geographical coordinates, time, and yield of detonation as wel as dimensions of the stabilized cloud were obtained from U.S. government reports (see Extended Data Table 1). In general, the base of the mushroom cap is ~0.7 of the altitude of the top of the cap. The base of the skirt is 1/2 and 2/3 the altitude of the base of the cap for ground/tower bursts and air bursts respectively.

The cloud particle sizes were assumed to be log-normally distributed using standard parameters from the U.S. Defense Land Fallout Interpretative Code for ground and tower tests (d=0.407 µm, s=4) and for aerial tests (d=0.15 µm, s=2), where d is the mean particle diameter and s the standard deviation of the diameter's natural logarithm.17 Particles were distributed in 100 diameter bins of equal activity (according to the 2.5 and 3rd moment respectively) and summed to a unit release. For ground and tower tests, the 2.5 moment of the distribution was used to model the first-order effect of fractionation between refractive and volatile nuclides which are typically located within the particle volume and on the particle surface, respectively.25,26 No fractionation was assumed for aerial tests.

In HYSPLIT, the particle density is kept constant over time. We assumed particle density to range from 2.5 to 4.8 g/cm3 for tower and aerial tests respectively and used the default scavenging coefficient for wet removal, applied both to below- and within-cloud scavenging, covering a wide range of particle sizes.27 (In HYSPLIT, the wet removal rate constant is defined as βwet = 8x10-5 P0.79 s-1 with P the precipitation rate in mm/h).

The results presented in this study were obtained by running 95 HYSPLIT computations (including 94 120-hour runs for all tests and one 240-h run for Trinity), with 9,000,000 particles each – requiring ~1 year of CPU time. To speed up computations, fallout from individual detonations was run in parallel on 128 threads (AMD Ryzen Threadripper PRO 5995WX, 64

cores) with 1-TB of RAM. The number of particles to track as wel as the size of the deposition grid (20 by 60 degrees with 0.1 x 0.1-degree cel s centered at 37.0o N, 95.0o W) required significant computational and memory resources. The grid size did not allow us to comprehensively study the impact of the atmospheric tests on Canada and Mexico but our estimates suggest fallout did cross the Canadian and Mexican borders in several instances, including after Trinity. Deposition density estimates beyond the United States could be the focus of future studies.


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Post-processing of particle deposition data

Our deposition density and dose rate estimates were produced in two steps. First, radionuclide density in Bq/m2 was computed using the con2rem HYSPLIT routine. The source code of con2rem was modified to allow for the use of more than 500 nuclides in the source term and to account for the beginning of decay at the time of the explosion and not at the beginning of the simulation. To produce the deposition density map, decay was stopped for particles at their moment of deposition on the surface. Different source terms were used for deposition density and dose rate contour calculations normalized at H+1 hour, where H is the detonation time, using plutonium-239 ENDF8 fission product yields at 500 keV fission neutron energy. Decay of the source term was conducted at different time intervals with Onix, an open-source depletion code developed at Princeton University.28

Second, a correction factor was applied to deposition density as a function of the distance from ground zero to account for the lack of well-defined semi-empirical particle sizes for tower shots (where only partial interaction between the ground and the fireball occur)19 and for what we identified as the underestimation of long-range deposition with standard DELFIC particle size parameters. The important challenge is the absence of consistent deposition density data for all radionuclides at short, medium, and very long ranges in the literature. This contributes to the need for a correction factor. A systematic exploration of the particle-size parameter space based on the paucity of semi-empirical data is beyond the scope of this study.

Instead, HYSPLIT estimates of iodine-131 deposition were benchmarked using the NCI reconstruction of nationwide (county-specific) total iodine-131 fallout deposition data from the Nevada Test Site at distances of 1500 to 3500 km from ground zero.5 The NCI dataset provides iodine deposition densities in 3094 United States counties from 54 atmospheric tests conducted at the Nevada test site. It was built from the reanalysis and interpolation of experimental deposition data, measured at ground stations across the United States.4 These measurements were carried out from October 1951 to November 1958 and involved between 40 and 95 stations spread throughout the country.

Two different correction factors Ctower and Cair were computed for ground/tower and aerial tests, using NCI data from 23 aerial and 31 ground and tower Nevada tests. For tower tests, we assumed a linear model, Ctower ∝ dGZ with dGZ the distance from ground zero, to capture the dominant effect of dry deposition via gravitational settling for large particles at short ranges.

For aerial tests, we found the correction factor to vary as exp(-β dGZ), consistent with the higher residence time of small airburst-generated particles, which are primarily removed from the atmosphere via wet scavenging. The parameters providing the best fit were found to be Ctower =

0.1493 x dGZ and Cair = 4.0518 104 x exp(-6.647 10-4 x dGZ) with dGZ in kilometers.


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Additional Data and Figures


Extended Data Table 1. List of atmospheric nuclear tests with key parameters used in this study. Time in GMT, height, cloud top and bottom are in meters above ground level.


U.S.

Operation

Name

Date

Type

Time

Latitude

Longitude

Height

Yield

Cloud

Cloud

#

[m]

[kt]

top [m]

bottom

[m]

1

MANHATTAN

Trinity

7/16/45

Tower

12:29

33.6773

-106.4754

30.5

24.8

9259

1822

7

RANGER

Able

1/27/51

Airdrop

13:45

36.8051

-115.9502

323.1

1

4225

2841

8

RANGER

Baker

1/28/51

Airdrop

13:52

36.8051

-115.9502

329.2

8

9711

6531

9

RANGER

Easy

2/1/51

Airdrop

13:47

36.8051

-115.9502

329.2

1

2853

1919

10

RANGER

Baker-2

2/2/51

Airdrop

13:49

36.8051

-115.9502

335.3

8

7577

5096

11

RANGER

Fox

2/6/51

Airdrop

13:47

36.8051

-115.9502

437.4

22

12149

7273

16

BUSTER

Able

10/22/51

Tower

14:00

37.0833

-116.0247

30.5

0.1

1168

771

17

BUSTER

Baker

10/28/51

Airdrop

15:20

37.0850

-116.0211

340.8

3.5

8384

5732

18

BUSTER

Charlie

10/30/51

Airdrop

15:00

37.0850

-116.0213

345

14

11219

6952

19

BUSTER

Dog

11/1/51

Airdrop

15:30

37.0846

-116.0209

431.9

21

12743

8171

20

BUSTER

Easy

11/5/51

Airdrop

16:30

37.0919

-116.0253

400.5

31

13953

9381

21

JANGLE

Sugar

11/19/51

Surface

17:00

37.1315

-116.0394

1.2

1.2

3287

2068

23

TUMBLER-

Able

4/1/52

Airdrop

17:00

36.7980

-115.9364

241.7

1

4000

2690

SNAPPER

24

TUMBLER-

Baker

4/15/52

Airdrop

17:30

37.0841

-116.0203

338

1

3507

1770

SNAPPER

25

TUMBLER-

Charlie

4/22/52

Airdrop

17:30

37.0844

-116.0211

1050.7

31

11524

8171

SNAPPER

26

TUMBLER-

Dog

5/1/52

Airdrop

16:30

37.0841

-116.0211

317

19

12133

7256

SNAPPER

27

TUMBLER-

Easy

5/7/52

Tower

12:15

37.0530

-116.1035

91.4

12

9044

5711

SNAPPER

28

TUMBLER-

Fox

5/25/52

Tower

12:00

37.0955

-116.1036

91.4

11

11184

7062

SNAPPER

29

TUMBLER-

George

6/1/52

Tower

11:55

37.0955

-116.1036

91.4

15

10050

6347

SNAPPER

30

TUMBLER-

How

6/5/52

Tower

11:55

37.1384

-116.1183

91.4

14

11372

7181

SNAPPER

33

UPSHOT-

Annie

3/17/53

Tower

13:20

37.0955

-116.1036

91.4

16

11270

7307

KNOTHOLE

34

UPSHOT-

Nancy

3/24/53

Tower

13:10

37.0955

-116.1036

91.4

24

11336

6611

KNOTHOLE

35

UPSHOT-

Ruth

3/31/53

Tower

13:00

37.0853

-116.0221

93

0.2

2926

2042

KNOTHOLE

36

UPSHOT-

Dixie

4/6/53

Airdrop

15:30

37.0846

-116.0207

1835.5

11

12489

8832

KNOTHOLE


12


37

UPSHOT-

Ray

4/11/53

Tower

12:45

37.0989

-116.0933

30.5

0.2

2674

1120

KNOTHOLE

38

UPSHOT-

Badger

4/18/53

Tower

12:35

37.1384

-116.1183

91.4

23

9604

5642

KNOTHOLE

39

UPSHOT-

Simon

4/25/53

Tower

12:30

37.0530

-116.1035

91.4

43

12119

8157

KNOTHOLE

40

UPSHOT-

Encore

5/8/53

Airdrop

15:30

36.7979

-115.9298

738.5

27

11864

7597

KNOTHOLE

41

UPSHOT-

Harry

5/19/53

Tower

12:05

37.0403

-116.0262

91.4

32

11733

7161

KNOTHOLE

42

UPSHOT-

Grable

5/25/53

Airburst 15:30

36.7979

-115.9298

159.7

15

9730

6073

KNOTHOLE

43

UPSHOT-

Climax

6/4/53

Airdrop

11:15

37.0875

-116.0192

406.6

61

11788

9441

KNOTHOLE

50

TEAPOT

Wasp

2/18/55

Airdrop

20:00

37.0865

-116.0227

232.3

1

5275

3141

51

TEAPOT

Moth

2/22/55

Tower

13:45

37.0955

-116.1036

91.4

2

6149

3619

52

TEAPOT

Tesla

3/1/55

Tower

13:30

37.1254

-116.0484

91.4

7

7918

4352

53

TEAPOT

Turk

3/7/55

Tower

13:20

37.1384

-116.1183

152.4

43

12256

9330

54

TEAPOT

Hornet

3/12/55

Tower

13:20

37.0403

-116.0262

91.4

4

10056

7252

55

TEAPOT

Bee

3/22/55

Tower

13:05

37.0948

-116.0246

152.4

8

10807

7698

57

TEAPOT

Apple-1

3/29/55

Tower

12:55

37.0955

-116.1036

152.4

14

8440

5575

58

TEAPOT

Wasp Prime

3/29/55

Airdrop

18:00

37.0865

-116.0227

225.2

3

8475

5700

59

TEAPOT

HA

4/6/55

Airdrop

18:00

37.0287

-116.0587

9931.1

3

15533

10446

60

TEAPOT

Post

4/9/55

Tower

12:30

37.1221

-116.0353

91.4

2

3433

2366

61

TEAPOT

MET

4/15/55

Tower

19:15

36.7979

-115.9298

121.9

22

11345

8755

62

TEAPOT

Apple-2

5/5/55

Tower

12:10

37.0530

-116.1035

152.4

29

14254

9225

63

TEAPOT

Zucchini

5/15/55

Tower

12:00

37.0948

-116.0246

152.4

28

10898

6387

67

Project 56

Project 56

1/18/56

Surface

21:30

36.9713

-115.9554

0.9

0.001

914

610

No. 4

87

PLUMBBOB

Boltzmann

5/28/57

Tower

11:55

37.0948

-116.0245

152.4

12

8768

5720

88

PLUMBBOB

Franklin

6/2/57

Tower

11:55

37.0955

-116.1036

91.4

0.14

3863

3040

89

PLUMBBOB

Lassen

6/5/57

Balloon

11:45

37.1347

-116.0416

152.4

0.0005

722

486

90

PLUMBBOB

Wilson

6/18/57

Balloon

11:45

37.1347

-116.0416

152.4

10

9379

6331

91

PLUMBBOB

Priscil a

6/24/57

Balloon

13:30

36.7979

-115.9298

213.4

37

12169

6378

93

PLUMBBOB

Hood

7/5/57

Balloon

11:40

37.1347

-116.0416

457.2

74

13341

9379

94

PLUMBBOB

Diablo

7/15/57

Tower

11:30

37.1502

-116.1095

152.4

17

8392

4734

95

PLUMBBOB

John

7/19/57

Rocket

14:00

37.1604

-116.0538

4520.2

2

12104

7644

96

PLUMBBOB

Kepler

7/24/57

Tower

11:50

37.0955

-116.1036

152.4

10

7221

4783

97

PLUMBBOB

Owens

7/25/57

Balloon

13:30

37.1347

-116.0416

152.4

9.7

9383

4811

99

PLUMBBOB

Stokes

8/7/57

Balloon

12:25

37.0865

-116.0248

457.2

19

10002

6954

101

PLUMBBOB

Shasta

8/18/57

Tower

12:00

37.1279

-116.1073

152.4

17

8417

3540

102

PLUMBBOB

Doppler

8/23/57

Balloon

12:00

37.0865

-116.0248

457.2

11

10293

5721


13


104

PLUMBBOB

Franklin

8/30/57

Balloon

12:40

37.0865

-116.0248

228.6

4.7

8478

5125

Prime

105

PLUMBBOB

Smoky

8/31/57

Tower

12:30

37.1872

-116.0687

213.4

44

10217

6452

106

PLUMBBOB

Galileo

9/2/57

Tower

12:40

37.0530

-116.1035

152.4

11

9982

3886

107

PLUMBBOB

Wheeler

9/6/57

Balloon

12:45

37.1347

-116.0416

152.4

0.197

3892

2978

108

PLUMBBOB

Coulomb-B

9/6/57

Surface

20:05

37.0429

-116.0271

0.9

0.3

4257

2688

109

PLUMBBOB

Laplace

9/8/57

Balloon

13:00

37.0865

-116.0248

228.6

1

4820

2991

110

PLUMBBOB

Fizeau

9/14/57

Tower

16:45

37.0334

-116.0322

152.4

11

10964

7001

111

PLUMBBOB

Newton

9/16/57

Balloon

12:50

37.0865

-116.0248

457.2

12

8478

4515

113

PLUMBBOB

Whitney

9/23/57

Tower

12:30

37.1384

-116.1183

152.4

19

7777

4119

114

PLUMBBOB

Charleston

9/28/57

Balloon

13:00

37.1347

-116.0416

457.2

12

8469

4811

115

PLUMBBOB

Morgan

10/7/57

Balloon

13:00

37.1347

-116.0416

152.4

8

10908

6640

117

PROJECT58

Coulomb-C

12/9/57

Surface

20:00

37.0482

-116.0252

0

0.5

2728

1723

160

HARDTACKII

Eddy

9/19/58

Balloon

14:00

37.0865

-116.0248

152.4

0.083

2077

1010

165

HARDTACKII

Mora

9/29/58

Balloon

14:05

37.0865

-116.0248

457.2

2

4363

1772

166

HARDTACKII

Hidalgo

10/5/58

Balloon

14:10

37.0865

-116.0248

114.9

0.077

2382

1163

169

HARDTACKII

Quay

10/10/58

Tower

14:30

37.0948

-116.0245

30.5

0.079

1754

992

170

HARDTACKII

Lea

10/13/58

Balloon

13:20

37.0865

-116.0248

457.2

1.4

3906

2382

172

HARDTACKII

Hamilton

10/15/58

Tower

16:00

36.8023

-115.9331

15.2

0.0012

890

433

174

HARDTACKII

Dona Ana

10/16/58

Balloon

14:20

37.0865

-116.0248

137.2

0.037

2077

705

175

HARDTACKII

Vesta

10/17/58

Surface

23:00

37.1226

-116.0354

0

0.024

1760

1111

176

HARDTACKII

Rio Arriba

10/18/58

Tower

14:25

37.0409

-116.0268

22.3

0.09

2893

2131

178

HARDTACKII

Socorro

10/22/58

Balloon

13:30

37.0865

-116.0248

442

6

6649

4820

179

HARDTACKII

Wrangel

10/22/58

Balloon

16:50

36.7979

-115.9298

457.2

0.115

2110

1196

181

HARDTACKII

Rushmore

10/22/58

Balloon

23:40

37.1347

-116.0416

152.4

0.188

457

307

182

HARDTACKII

Catron

10/24/58

Tower

15:00

37.0428

-116.0278

22.3

0.021

1364

297

183

HARDTACKII

Juno

10/24/58

Surface

16:01

37.1233

-116.0387

0

0.0017

393

248

184

HARDTACKII

Ceres

10/26/58

Tower

4:00

37.1813

-116.0695

7.6

0.0007

479

303

185

HARDTACKII

Sanford

10/26/58

Balloon

10:20

36.7979

-115.9298

457.2

4.9

6987

2872

186

HARDTACKII

De Baca

10/26/58

Balloon

16:00

37.0865

-116.0248

457.2

2.2

4058

1772

187

HARDTACKII

Chaves

10/27/58

Tower

14:30

37.0446

-116.0307

15.8

0.0006

754

476

(Chavez)

190

HARDTACKII

Humboldt

10/29/58

Tower

14:45

37.0476

-116.0254

7.6

0.0078

1058

601

191

HARDTACKII

Santa Fe

10/30/58

Balloon

3:00

37.0865

-116.0248

457.2

1.3

4211

2687

194

HARDTACKII

Titania

10/30/58

Tower

20:34

37.1772

-116.0701

7.6

0.0002

487

307

265

SUNBEAM

Little Feller II

7/7/62

Surface

17:00

37.1191

-116.3037

0.9

0.022

1790

1130

271

SUNBEAM

Small Boy

7/14/62

Tower

18:30

36.8025

-115.9259

3

1.65

4853

3065

272

SUNBEAM

Little Feller I

7/17/62

Surface

17:00

37.1096

-116.3182

0.9

0.018

1770

1118


14


Extended Data Figure 1. ERA5 surface and upper air (pilot balloons and radiosondes) observations for July, 16, 1945. (a), World-wide observations. (b), Details for the region of interest in this study.


15


Extended Data Figure 2. Trinity deposition density map six days after detonation showing the contamination of two mills manufacturing strawboard material for photographic film storage in 1945.


16


Extended Data Figure 3. Plutonium-239 deposition density estimates at Crawford Lake (43.468 N, 79.949 W) in Ontario, Canada, following the detonation of Trinity in New Mexico, United States. These estimates assume that 5.2kg out of 6 kg of plutonium-239 (specific activity of 2.27 1012 Bq/kg ) did not fission during the explosive chain reaction.29 Estimates show that small amounts of plutonium could have arrived at Crawford Lake as early as 4 days after detonation and that peak deposition happened between 6 and 7 days after detonation.


17


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20 Beck, H. L., and Bennett, B. G. Historical overview of atmospheric nuclear weapons testing and estimates of fal out in the continental United States. Health Physics 82, no. 5, 591-608, (2002).

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National Oceanic and Atmospheric Administration, Las Vegas, NV (USA). Weather Service Nuclear Support Office, 1–82 (1987).

22 Webb, J. H. The fogging of photographic film by radioactive contaminants in cardboard packaging materials. Physical Review 76, no. 3, 375–380, (1949).

23 Draxler, R. et al. World Meteorological Organization's model simulations of the radionuclide dispersion and deposition from the Fukushima Daiichi nuclear power plant accident, Journal of environmental radioactivity 139, 172–184 (2015).

24 Quérel, A., Quélo, D., Roustan, Y. and Mathieu, A. Sensitivity study to select the wet deposition scheme in an operational atmospheric transport model, Journal of Environmental Radioactivity 237, 106712 (2021).

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29 Beck, H. L., Simon, S.L., Bouvil e, A. and Romanyukha, A. Accounting for unfissioned plutonium from the Trinity atomic bomb test. Health Physics 119, no. 4, 504 (2020).


19