Transport and Fate of 137Cs Released From Multiple Sources in the North Atlantic and Arctic Oceans

The North Atlantic and Arctic oceans, along with the North Pacific, are the main reservoirs of anthropogenic radionuclides introduced in the past 75 years. The POSEIDON-R compartment model was applied to the North Atlantic and Arctic oceans to reconstruct 137Cs contamination in 1945–2020 due to multiple sources: global fallout, exchange flows with other oceans, point-source inputs in the ocean from reprocessing plants and other nuclear facilities, the impact of the Chernobyl accident and secondary contamination resulting from river runoff and redissolution from bottom sediments. The model simulated the marine environment as a system of 3D compartments comprising the water column, bottom sediment, and biota. The dynamic model described the transfer of 137Cs through the pelagic and benthic food chains. The simulation results were validated using the marine database MARIS. The calculated concentrations of 137Cs in the seaweed and non-piscivorous and piscivorous pelagic fish mostly followed the concentration of 137Cs in water. The concentration in coastal predator fish lagged behind the concentration in water as a result of a diet that includes both pelagic and benthic organisms. The impact of each considered source on the total concentration of 137Cs in non-piscivorous fish in the regions of interest was analyzed. Whereas the contribution from global fallout dominated in 1960–1970, in 1970–1990, the contribution of 137Cs released from reprocessing plants exceeded the contributions from other sources in almost all considered regions. Secondary contamination due to river runoff was less than 4% of ocean influx. The maximum total inventory of 137Cs in the Arctic Ocean (31,122 TBq) was reached in 1988, whereas the corresponding inventory in the bottom sediment was approximately 6% of the total. The general agreement between simulated and observed 137Cs concentrations in water and bottom sediment was confirmed by the estimates of geometric mean and geometric standard deviation, which varied from 0.89 to 1.29 and from 1.22 to 1.87, respectively. The approach used is useful to synthesize measurement and simulation data in areas with observational gaps. For this purpose, 13 representative regions in the North Atlantic and Arctic oceans were selected for monitoring by using the “etalon” method for classification.

Radioactivity level of coastal sediments and water across the Sangihe Island as the outlying islands of Indonesia

Indonesia as an archipelagic country is very concerned about maritime development, the outlying islands are the entrance for potential threats of radioactive distribution from global waters. Furthermore, the outlying islands have functions such as territorial defence, security, and sovereignty, economic and ecological. As environmental protection, level of natural and anthropogenic radioactivity was performed due to potential threats. The activity concentration of natural (226Ra, 232Th, and 40K) radionuclides inshore sediments samples are range from 3.44 ± 0.01 Bq kg−1, 5.13 ± 0.03 Bq kg−1 and 151.42 ± 0.04 Bq kg−1 respectively and average concentration level of anthropogenic of 137Cs in sediment and seawater obtained were 0.35 Bq kg−1 and 0.83 Bq m3 respectively. The concentrations value of NORM was lower compare to another region but the ratio sequence 226Ra<232Th<40K relatively have same pattern. The presence of fission product 137Cs in this region comes from global fallout since no nuclear activities in Indonesia and the level of 137Cs are almost same as the estimation the concentration 137Cs in the Pacific Ocean and comparable with other studies. Radioactivity levels in all samples are under the value of radiological hazard index (0.004-0.039, trace hold h-index=1) and annual effective dose rate are in save level (0.01 mSv/y, recommended limit AED=1mSv/year). The level of NORM radioactivity is locally and varied for each region meanwhile anthropogenic radioactivity are global and comparable since there are no nuclear activity in Indonesia.

Records of plutonium isotopes in marine sediments from the southern Gulf of Mexico

Here we report on new data on plutonium (Pu) isotopes to elucidate activity concentrations, inventories, sources and their transport from the ocean surface to the sea floor from a collection of deep-sea sediment cores (depths ranging from 257 to 3739 m) in the Gulf of Mexico (GoM). Sediment cores collected from the continental shelf and upper slope region of the GoM consistently showed 240Pu/239Pu ratios of 0.15 to 0.26 and Pu-inventories ranging from 15 to 35 Bq m− 2. Inventories and ratios are consistent with global fallout Pu for this tropical region. In the continental shelf and upper slope regions, higher particle concentrations close to the margins favor significant scavenging and removal of Pu from the water column; in contrast with the deep-sea cores that show low 240Pu/239Pu ratios (0.07–0.13) and a much lower Pu inventory (< 7 Bq m-2) implying a small fraction of the expected global fallout inventory has reached into the lower slopes and abyssal plain of the GoM. Low values and a progressive decrease of 240Pu/239Pu ratios and Pu inventories with increasing water depth have been previously reported for the GoM. The low Pu ratios indicate that Nevada tests fallout was an important source of Pu to deep-sea sediments, and that this source was likely more efficiently removed from the water column than global fallout Pu. Analysis of Pu isotopes in two sediment traps from the upper slope regions show 240Pu/239Pu ratios comparable to the ones observed in the global fallout. These results indicate that global fallout Pu is currently the main source of Pu in water column particles. Therefore, a significant fraction of global fallout Pu must still be present; either in a dissolved phase, or as biologically recycled material in the water column, or scavenged on the shelf and shelf break. Our results bring to light important questions on the application of Pu isotopes to establish sediment chronologies, since these radionuclides are shown to be tracers of bioturbation rather than accumulation processes in deep-sea sediments of the GoM, similar to previously reported results from excess 210Pb.

70-year anthropogenic uranium imprints of nuclear activities in Baltic Sea sediments

Strongly stratified water structure and densely populated catchment make the Baltic Sea one of the most polluted seas. Understanding its circulation pattern and time scale is essential to predict the dynamics of hypoxia, eutrophication, and pollutants. Anthropogenic 236U and 233U have been demonstrated as excellent transient tracers in oceanic studies, but unclear input history and inadequate long-term monitoring records limit their application in the Baltic Sea. From two dated Baltic sediment cores, we obtained high-resolution records of anthropogenic uranium imprints originated from three major human nuclear activities throughout the Atomic Era. Using the novel 233U/236U signature, we distinguished and quantified 236U inputs from global fallout (43.3%-50.5%), Chernobyl accident (< 0.9%), and discharges of civil nuclear industry (48.6%-56.7%) to the Baltic Sea. We estimated the total release of 233U (7-15kg) from the atmospheric nuclear weapons testing, and pinpointed 233U peak signal in the mid-to-late 1950s as a potential time marker for the onset of the Anthropocene Epoch. This work also provides fundamental 236U data for Chernobyl accident and early discharges from civil nuclear facilities, prompting worldwide 233U-236U tracer studies. We anticipate our data to be a broader application in model-observation interdisciplinary research on water circulation and pollutant dynamics in the Baltic Sea.

Yemeni combatants’ stances will block peace efforts

Significance He insisted the Saudi-led military coalition, which backs internationally recognised President Abd Rabbu Mansur Hadi, must first end its blockade. Fighting has intensified in recent weeks: the Huthis have conducting missile attacks on Saudi Arabia and Riyadh yesterday launching heavy air strikes against a major Huthi advance in oil-rich Marib. Impacts Armed conflict and blockade measures will cause continuing economic and humanitarian hardship. The ongoing global fallout from the COVID-19 pandemic will further reduce international attention on Yemen. Pressure will mount for greater civil society inclusion in peace talks, though mechanisms for this will be highly controversial. Appointment of a new UN Yemen envoy soon (as the incumbent has been three years in office, with poor Sana’a ties) may shift talks dynamics.

Detection of an unknown emission source in the Baltic Sea using the new oceanographic tracer U-233/U-236

&lt;p&gt;&lt;span&gt;By analysing the two long-lived anthropogenic Uranium (U) isotopes U-233 and U-236 in different compartments &lt;/span&gt;&lt;span&gt;of the environment affected by releases of nuclear power production or by global fallout from nuclear weapons tests&lt;/span&gt;&lt;span&gt;, we showed that the corresponding isotopic ratios U-233/U-236&lt;/span&gt;&lt;span&gt; differ by one order of magnitude. Based on these experimental results which were obtained with the ultra-sensitive detection method Accelerator Mass Spectrometry, we suggested a representative ratio for nuclear weapons fallout of &lt;/span&gt;&lt;span&gt;U-233/U-236&lt;/span&gt;&lt;span&gt; =&lt;/span&gt;&lt;span&gt; (1.40 &amp;#177; 0.15) &amp;#183;10&lt;/span&gt;&lt;sup&gt;&lt;span&gt;-2&lt;/span&gt;&lt;/sup&gt;&lt;span&gt; and (0.12 &amp;#177; 0.01) &amp;#183;10&lt;/span&gt;&lt;sup&gt;&lt;span&gt;-2&lt;/span&gt;&lt;/sup&gt;&lt;span&gt; for releases from nuclear power production. Consequently, the &lt;/span&gt;&lt;span&gt;U-233/U-236&lt;/span&gt;&lt;span&gt; ratio not only &lt;/span&gt;&lt;span&gt;has the potential to become a novel sensitive fingerprint for releases from nuclear industry, but could also serve as a powerful oceanographic tracer due to the conservative behaviour of U in ocean water which does not suffer from chemical fractionation. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;As a first application of this paired tracer, we studied the distribution of U-233 and U-236 concentrations in addition to I-129 in the Baltic Sea which is known to have received inputs of radionuclides from various contamination sources including the two European reprocessing plants, global fallout from weapons testings and fallout from the Chernobyl accident. Our data indicate an additional unidentified source of reactor U-236 in the Baltic Sea demonstrating the high sensitivity of the U-233/U-236 ratio to distinguish different emission sources in water mixing processes.&lt;/span&gt;&lt;/p&gt;

Differentiating Fukushima and Nagasaki sourced plutonium from global fallout: Pu vs Cs in soils and biota

&lt;p&gt;The release of plutonium (Pu) from the 2011 Fukushima accident has raised questions on how prevalent it is in the environment and how its cycling into the biosphere compares with that from the previous Nagasaki and global-fallout sources.&amp;#160; Here, we report on systematic sampling and analysis of soils, earthworms, and wild boar as markers of Pu in the deposition areas near the Fukushima Daiichi Nuclear Power Station (FDNPS) and Nagasaki. Highly-sensitive Accelerator Mass Spectrometry (AMS) methods were used to distinguish the Pu sourced from the FDNPS accident, and Nagasaki-detonation, from worldwide fallout Pu. We primarily used &lt;sup&gt;241&lt;/sup&gt;Pu/&lt;sup&gt;239&lt;/sup&gt;Pu atom ratios, as the other typically-used Pu measures (&lt;sup&gt;240&lt;/sup&gt;Pu/&lt;sup&gt;239&lt;/sup&gt;Pu atom ratios, activity concentrations) were less sensitive and did not distinguish the FDNPS Pu from background in most study samples.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Near the FDNPS, results indicate that five years after the accident, 0.4% &amp;#8211; 2% of the Pu in the local soils (0-5cm) had originated from the FDNPS releases, the remainder being from global fallout.&amp;#160; The trace amounts of FDNPS Pu (e.g., 0.02-0.04 Bq kg&lt;sup&gt;-1&lt;/sup&gt;&lt;sup&gt;239&lt;/sup&gt;Pu estimated in local ~3km deposition) contrasted sharply with the &lt;sup&gt;134+137&lt;/sup&gt;Cs content which was about 10&lt;sup&gt;6&lt;/sup&gt; times greater than background in the same samples. The accident also contributed new Pu of ~0.3% &amp;#8211; 3% in earthworms and ~1% &amp;#8211; 10% in wild boar near the FDNPS. The soil and wild boar data from across the study sites consistently indicate only low levels of new accident-Pu and do not support the concept of a substantial undiscovered deposit of Pu near the FDNPS. Unlike sparsely-taken individual soil samples that might miss a Pu hotspot, the wild boar samples represent the integration of uptake throughout their entire foraging areas.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Near Nagasaki, our measurements in 2016 show a lasting legacy of Pu sourced from the 1945 detonation (~93% soils, ~88% earthworm, ~96% boar in samples &lt;5km from the Nagasaki hypocentre; the remainder from global fallout). Even with these high percentages arising from the 1945 detonation, &amp;#160;the Pu amounts at all study sites in Japan are comparable&amp;#160; to background fallout levels elsewhere and are orders of magnitude lower than what remains near Chernobyl. At the study areas, the dose rates from Pu to organisms, as well as to potential human consumers of wild boar meat, have been only slightly elevated above background and are orders of magnitude lower than the dose potentials from the &lt;sup&gt;134,137&lt;/sup&gt;Cs in samples from near the FDNPS. &amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The results demonstrate progress in increasing the sensitivity of AMS methods, including the use of &lt;sup&gt;241&lt;/sup&gt;Pu/&lt;sup&gt;239&lt;/sup&gt;Pu atom ratios, to compare recent and past nuclear contamination events and suggest that the Nagasaki-detonation Pu will be distinguishable in the environment long after the FDNPP-accident Pu is not.&lt;/p&gt;