[Enhancement of Antitumor Effect by the Combined Use of Anti-EGFR Antibody(Necitumumab)and PD-1 Inhibitor].

Necitumumab enhances antitumor immunity by decreasing the PD-L1 expression; it is expected to improve the prognosis of patients treated with an immune checkpoint inhibitor(ICI)by inhibiting the IL-8 expression. Since the combined effect of necitumumab and PD-L1 inhibitor was confirmed in an in vivo study conducted in transgenic mice, further antitumor effects can be expected by the combined use of necitumumab and ICI.

Multiple Evaluation of Typical Heavy Metals Pollution in Surface Soil and Road Dust from Beijing and Hebei Province, China.

Soil and road dust are important receptors of heavy metals in the environment. Meanwhile, heavy metal could transfer to the atmosphere through resuspension. Due to the serious consequences and atmospheric haze in Jing-Jin-Ji area, it's important to evaluate the pollution level, particle size distribution and sources of heavy metals. For heavy metals in soil samples, similar concentrations to the background values and no obvious pollution or low-level pollution was presented. Higher concentration of Cu (78.9 mg/kg) and Zn (261 mg/kg) were found in road dust. The source appointment results showed that Mn, Co, Cr, Ni, Zn and Pb in soils and Cr, Co and Mn in road dust were mainly from the natural sources, while traffic source contributed to most of Cu, Zn and Pb in road dust. Different particle size distribution patterns were found in soils and road dusts, and the finest particles presented the highest heavy metal concentrations.

Distributions of 239Pu and 240Pu Concentrations and 240Pu/239Pu Atom Ratios and 239+240Pu Inventories in a Water Column in the Eastern Indian Ocean: Transport of Pacific Proving Grounds-Derived Pu via the Indonesian Throughflow.

The 239+240Pu concentrations and 240Pu/239Pu atom ratios in seawater from the eastern Indian Ocean were determined to identify their Pu sources and to propose the transport pathway of Pacific Proving Grounds (PPG)-derived Pu into the studied area. This is the first study by anyone on these Pu atom ratios in the Indian Ocean. In the West Australia Basin, the 239+240Pu concentration was 2.89 mBq m-3 in the surface water and increased with depth; a subsurface maximum was identified at 200 m depth and then decreased gradually with depth; its water column inventory was 32.8 Bq m-2. The inventory-weighted mean 240Pu/239Pu atom ratios were 0.208 in the South Australia Basin, 0.226 in the Perth Basin, 0.242 in the West Australia Basin, 0.232 in the Bay of Bengal, and 0.225 in the Andaman Sea. The obtained 240Pu/239Pu ratios were clearly greater than the mean global fallout ratio of 0.18. These high atom ratios proved the presence of close-in fallout Pu from PPG nuclear tests. The relative contribution of global and PPG fallouts was evaluated using the two-end-member mixing model. The 239+240Pu inventories originating from the PPG fallout were calculated as 2.9-14.9 Bq m-2, which corresponded to 20-46% of the total 239+240Pu inventory. A significant amount of the PPG-derived Pu has been transported to the eastern Indian Ocean. The proposed transport pathway accounting for the high 240Pu/239Pu ratio is the transportation of PPG-derived Pu by the North Equatorial Current followed by the Mindanao Current, Indonesian Throughflow, and then spreading over the Indian Ocean by its surface circulation system.

[Intradural Mucocele Associated with a Frontoethmoidal Osteoma:A Case Report].

The formation of symptomatic intradural mucocele associated with a paranasal osteoma is rare, and no standard treatment has been established. Here, we present a case of intradural mucocele in a 27-year-old man complaining of headache and generalized convulsion. Cranial CT and brain MRI showed a left frontoethmoidal osteoma extending into the left anterior cranial fossa and orbit along with a mass in the left frontal lobe. He underwent resection of both intracranial osteomas and the mass through left frontal craniotomy. Histological findings were consistent with a mucocele, and the diagnosis of an intradural mucocele associated with a frontoethmoidal osteoma was confirmed. The postoperative course was uneventful. Although both osteoma and mucocele are benign, they may cause life-threatening symptoms by expanding intracranially. A tailored treatment considering the invasiveness and postoperative long-term follow-up of the patient is essential for this uncommon condition.

Plutonium Isotopes (239-241Pu) Dissolved in Pacific Ocean Waters Detected by Accelerator Mass Spectrometry: No Effects of the Fukushima Accident Observed.

The concentration of plutonium (Pu) and the isotopic ratios of 240Pu to 239Pu and 241Pu to 239Pu were determined by accelerator mass spectrometry (AMS) in Pacific Ocean water samples (20 L each) collected in late 2012. The isotopic Pu ratios are important indicators of different contamination sources and were used to identify a possible release of Pu into the ocean by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. In particular, 241Pu is a well-suited indicator for a recent entry of Pu because 241Pu from fallout of nuclear weapon testings has already significantly decayed. A total of 10 ocean water samples were prepared at the Radiochemie München of the TUM and analyzed at the Vienna Environmental Research Laboratory (VERA). Several samples showed a slightly elevated 240Pu/239Pu ratio of up to 0.22 ± 0.02 compared to global fallout (240Pu/239Pu = 0.180 ± 0.007), whereas all measured 241Pu-to-239Pu ratios were consistent with nuclear weapon fallout (241Pu/239Pu < 2.4 × 10-3), which means that no impact from the Fukushima accident was detected. From the average 241Pu-to-239Pu ratio of 8-2+3 ×10-4 at a sampling station located at a distance of 39.6 km to FDNPP, the 1-σ upper limit for the FDNPP contribution to the 239Pu inventory in the water column was estimated to be 0.2%. Pu, with the signature of weapon-grade Pu was found in a single sample collected around 770 km off the west coast of the United States.

Fractal Dimension of Tc-99m DTPA GSA Estimates Pathologic Liver Injury due to Chemotherapy in Liver Cancer Patients.

BACKGROUND: Chemotherapy-induced liver injury after potent chemotherapy is a considerable problem in patients undergoing liver resection. The aim of this study was to assess the relationship between the fractal dimension (FD) of Tc-99m diethylenetriaminepentaacetic acid (DTPA) galactosyl human serum albumin (GSA) and pathologic change of liver parenchyma in liver cancer patients who have undergone chemotherapy. METHODS: We examined 34 patients (10 female and 24 male; mean age, 68.5 years) who underwent hepatectomy. Hepatic injury was defined as steatosis more than 30 %, grade 2-3 sinusoidal dilation, and/or steatohepatitis Kleiner score ≥4. Fractal analysis was applied to all images of Tc-99m DTPA GSA using a plug-in tool on ImageJ software (NIH, Bethesda, MD). A differential box-counting method was applied, and FD was calculated as a heterogeneity parameter. Correlations between FD and clinicopathological variables were examined. RESULTS: FD values of patients with steatosis and steatohepatitis were significantly higher than those without (P > .001 and P > .001, respectively). There was no difference between the FD values of patients with and without sinusoidal dilatation (P = .357). Multivariate logistic regression showed FD as the only significant predictor for steatosis (P = .005; OR 36.5; 95 % CI 3.0-446.3) and steatohepatitis (P = .012; OR, 29.1; 95 % CI 2.1-400.1). CONCLUSIONS: FD of Tc-99m DTPA GSA was the significant predictor for fatty liver disease in patients who underwent chemotherapy. This new modality is able to differentiate steatohepatitis from steatosis; therefore, it may be useful for predicting chemotherapy-induced pathologic liver injury.

Vertical distributions of radionuclides ((239+240)Pu, (240)Pu/(239)Pu, and (137)Cs) in sediment cores of Lake Bosten in Northwestern China.

Artificial radionuclides ((137)Cs, (239+240)Pu, (241)Pu, (241)Am) deposited in lacustrine sediments have been used for dating as well as radionuclide source identification. In the present work, we investigated the vertical distributions of (239+240)Pu and (137)Cs activities, (240)Pu/(239)Pu atom ratios, and (239+240)Pu/(137)Cs activity ratios in sediment cores collected from Lake Bosten, which is the lake closest to the Lop Nor Chinese Nuclear Weapon Test site in northwestern China. Uniformly high concentrations of (239+240)Pu and (137)Cs were found in the upper layers deposited since 1964 in the sediment cores, and these were controlled by the resuspension of soil containing radionuclides from the nearby land surface. As the Chinese nuclear tests varied remarkably in yield, the mixing of the tropospheric deposition from these tests and the stratospheric deposition of global fallout has led to a (240)Pu/(239)Pu atom ratio that is similar to that of global fallout and to a (239+240)Pu/(137)Cs activity ratio that is slightly higher than that of global fallout. However, a low (240)Pu/(239)Pu atom ratio of 0.080 and high (239+240)Pu/(137)Cs activity ratio of 0.087, significantly different from the global fallout values, were observed in one sediment core (07BS10-2), indicating the inhomogenous tropospheric deposition from the Chinese nuclear tests in Lake Bosten during 1967-1973. These results are important to understand the influence of the CNTs on the radionuclide contamination in Lake Bosten.

A method of measurement of (239)Pu, (240)Pu, (241)Pu in high U content marine sediments by sector field ICP-MS and its application to Fukushima sediment samples.

An accurate and precise analytical method is highly needed for the determination of Pu isotopes in marine sediments for the long-term marine environment monitoring that is being done since the Fukushima Dai-ichi Nuclear Power Plant accident. The elimination of uranium from the sediment samples needs to be carefully checked. We established an analytical method based on anion-exchange chromatography and SF-ICP-MS in this work. A uranium decontamination factor of 2 × 10(6) was achieved, and the U concentrations in the final sample solutions were typically below 4 pg mL(-1), thus no extra correction of (238)U interferences from the Pu spectra was needed. The method was suitable for the analysis of (241)Pu in marine sediments using large sample amounts (>10 g). We validated the method by measuring marine sediment reference materials and our results agreed well with the certified and the literature values. Surface sediments and one sediment core sample collected after the nuclear accident were analyzed. The characterization of (241)Pu/(239)Pu atom ratios in the surface sediments and the vertical distribution of Pu isotopes showed that there was no detectable Pu contamination from the nuclear accident in the marine sediments collected 30 km off the plant site.

Release of Pu isotopes from the Fukushima Daiichi Nuclear Power Plant accident to the marine environment was negligible.

Atmospheric deposition of Pu isotopes from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has been observed in the terrestrial environment around the FDNPP site; however, their deposition in the marine environment has not been studied. The possible contamination of Pu in the marine environment has attracted great scientific and public concern. To fully understand this possible contamination of Pu isotopes from the FDNPP accident to the marine environment, we collected marine sediment core samples within the 30 km zone around the FDNPP site in the western North Pacific about two years after the accident. Pu isotopes ((239)Pu, (240)Pu, and (241)Pu) and radiocesium isotopes ((134)Cs and (137)Cs) in the samples were determined. The high activities of radiocesium and the (134)Cs/(137)Cs activity ratios with values around 1 (decay corrected to 15 March 2011) suggested that these samples were contaminated by the FDNPP accident-released radionuclides. However, the activities of (239+240)Pu and (241)Pu were low compared with the background level before the FDNPP accident. The Pu atom ratios ((240)Pu/(239)Pu and (241)Pu/(239)Pu) suggested that global fallout and the pacific proving ground (PPG) close-in fallout are the main sources for Pu contamination in the marine sediments. As Pu isotopes are particle-reactive and they can be easily incorporated with the marine sediments, we concluded that the release of Pu isotopes from the FDNPP accident to the marine environment was negligible.

No long-term variation of 240Pu/239Pu atom ratio in liver of Japanese common squid (Todarodes pacificus) collected from seven sea areas around Japan during 2003-2018.

The 239+240Pu concentrations and 240Pu/239Pu atom ratios were determined to trace the temporal variability in concentration and atom ratio in liver of the Japanese common squid during 2003-2018. The differences in their concentrations and atom ratios and the dependency on the collection areas and migratory history were compared. The organ affinity of Pu in mantle, limb, liver, and internal organs except liver was also investigated. The average 239+240Pu concentrations were the highest in liver followed in order by internal organs except liver, limb, and mantle. The Pu accumulation in liver could be explained by a mechanism for foreign substance processing. A significant difference in the average 239+240Pu concentrations in liver was found among the sea areas for specimen collection during 2003-2018. In spite of a noticeable difference in the average 239+240Pu concentrations, the 240Pu/239Pu atom ratios showed no significant temporal variability around Japan; thus, they were continuously uniform during 2003-2018.

Aplastic Anemia with Epstein-Barr Virus Reactivation after Anti-thymocyte Globulin Therapy.

Lymphoproliferative disorders and Epstein-Barr virus reactivation (EBV-LPDs) have various forms of onset, ranging from infectious mononucleosis-like syndrome (IM-like) to lymphoma, although whether or not IM-like progresses to lymphoma remains unclear. A 61-year-old man was diagnosed with aplastic anemia (AA). Polyclonal atypical B-lymphocytes were observed in the peripheral blood, and IM-like was diagnosed. Atypical lymphocytes disappeared, but a gastrointestinal examination revealed diffuse large B-cell lymphoma (DLBCL). Rituximab was initiated but later discontinued because of severe acute respiratory syndrome coronavirus 2 infection. Pancytopenia due to AA exacerbation recurred. The patient ultimately died of multiple organ failure due to bacterial infection.

Enhanced boundary scavenging of 241Am on the continental margin of the East China sea.

The 241Am concentrations were determined by sector field high-resolution inductively coupled plasma mass spectrometry for settling particles and surface sediments collected on the continental margin in the East China Sea to discuss the behavior of 241Am in the studied area. A large and regular increase was noted from 97 m depth to 592 m depth in 241Am concentrations in settling particles from the cylindrical sediment traps, whereas only a slight increase in 239+240Pu concentrations was evident. The gradual increase in 241Am/239+240Pu activity ratios from the cylindrical trap settling particles also was observed. These results were attributed to 241Am being scavenged by settling particles at a more rapid scavenging rate than 239+240Pu. There was an obvious tendency for 241Am fluxes to increase linearly with depth with the highest fluxes at near-bottom, and these fluxes were due to large advective import to the near-bottom. There was a tendency for 241Am concentrations in surface sediments to increase almost linearly with depth, showing the same tendency as 210Pb concentrations, and this tendency indicated that the enhanced boundary scavenging of 241Am as well as 210Pb occurred in the East China Sea continental slope region due to the greater abundance of reactive finer particles. The 241Am concentrations in settling particles from the time-series sediment trap ranged from 1.05 to 4.20 mBq g-1, showing large variation. The 241Am concentrations from the time-series trap varied inversely with the total mass fluxes, indicating that 241Am concentrations were diluted by particles when mass flux increased. The 241Am fluxes showed large time-series variations and these variations were primarily controlled by mass flux variation. It seems that the high total mass flux events are due to resuspension of the underlying surface sediments and episodic lateral transport of particles that flow down the continental slope in the East China Sea.

Cesium-137 and 137Cs/133Cs atom ratios in marine zooplankton off the east coast of Japan during 2012-2020 following the Fukushima Dai-ichi nuclear power plant accident.

We measured the concentrations of cesium isotopes (133Cs, 134Cs, and 137Cs) in zooplankton samples collected in waters off the east coast of Japan from May 2015 to June 2020. By combining these data with those obtained previously from May 2012 to February 2015, we evaluated the long-term impacts of the Fukushima Dai-ichi Nuclear Power Plant accident on marine zooplankton. Relatively high 137Cs concentrations in zooplankton, exceeding 10 Bq/kg-dry weight, were sporadically observed until June 2016, regardless of year or station. After May-June 2017, 137Cs concentrations decreased to below 1 Bq/kg-dry at most stations, and by May 2020, concentrations were below 0.5 Bq/kg-dry except those off Fukushima Prefecture. Since the accident, the 137Cs/133Cs atom ratios of zooplankton samples were higher than those of ambient seawater until 2019, but in May-June 2020 the ratios matched those of seawater except off Fukushima Prefecture. Highly radioactive particles were not detected in zooplankton samples by autoradiography using imaging plates after May-June 2017, although they were before. Therefore, the persistence of elevated 137Cs/133Cs ratios in zooplankton relative to seawater for nine years after the accident was probably due to the incorporation of highly radioactive particles (cesium-bearing particles or clay-mineral aggregates with highly adsorbed radiocesium) onto/into zooplankton for several years after the accident. However, since at least May-June 2017, these elevated ratios have likely been caused by small highly radioactive particles (or larger particles disaggregated into small pieces) entering the ocean from land via rivers or directly discharged from the Fukushima Nuclear Power Plant. Microplastics enriched with radiocesium with higher 137Cs/133Cs ratios than seawater may have also contributed 137Cs to the zooplankton.

Fifty-Six Years after Acrylic Hemiarthroplasty and after Then: A Case Report of Revision THA.

We revised an acrylic femoral hip prosthesis to a total hip prosthesis for an 86-year-old female. The implant was made of dental resin and had functioned for 56 years in situ, though its stem had broken. Because of no osteolytic reaction, the reconstruction was relatively easy. From the result of histologic and radiologic examination, the bio-inertness of material and uncemented fixation seemed to contribute the minimum bone loss and to the favorite spontaneous arthrodesis after providing good joint function in her middle age.

A storm-induced flood and associated nearshore dispersal of the river-derived suspended 137Cs.

Accidental leakage of radionuclides from the Fukushima Nuclear Power Plant (FNPP1) took place in the aftermath of the catastrophic tsunamis associated with the Great East Japan Earthquake that occurred on March 11, 2011. Significant amount of radionuclides released into the atmosphere were reportedly transported and deposited on land located near FNPP1. The Niida River, Fukushima, Japan, has been recognized as a terrestrial source of highly contaminated suspended radiocesium adhering to sediment particles in the ocean through the river mouth as a result of hydrological processes. Remaining scientific questions include the oceanic dispersal and inventories of the sediments and suspended radiocesium in the ocean floor derived from the Niida River. Complementing limited in situ data, we developed a quadruple nested 3D ocean circulation and sediment transport model in an extremely high-resolution configuration to quantify the transport processes of the suspended radiocesium. Particularly, we investigated the storm and subsequent floods associated with Typhoon 201326 (Wipha) that passed off the Fukushima coast in October 2013, and subsequently promoted precipitation to a considerable extent and associated riverine freshwater discharge along with sediment outfluxes to the ocean. Using in situ bed sediment core data obtained from regions near the river mouth, we conducted a quantitative assessment of the accumulation and erosion of the sediments and explored the resultant suspended radiocesium distribution around the river mouth and nearshore areas along the Fukushima coast. We identified three major accumulative areas, near the river mouth within an area < 1 km, around the breakwaters in the north of the river mouth, and along the southern coastal area, while offshore and northward transports were minor. The present study clearly exhibits substantial retention of the land-derived radiocesium adsorbed to the sediments in the coastal areas, leading to possible long-term influences on the surrounding marine environment.

Assessment of chromosome aberrations in large Japanese field mice (Apodemus speciosus) in Namie Town, Fukushima.

PURPOSE: After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan on March 11 2011, the surroundings became contaminated with radionuclides. To understand the possible biological effects after chronic low dose-rate radiation in contaminated areas of Fukushima, we assessed the effects in large Japanese field mice (Apodemus speciosus) by means of chromosome aberration analysis. MATERIALS AND METHODS: We collected A. speciosus in five sites around Namie Town, Fukushima (contaminated areas) and in two sites in Hirosaki City, Aomori (control areas, 350 km north of FDNPP) from autumn 2011 to 2013. The number of mice captured and ambient dose-rates were as follows: high (n = 11, 10.1-30.0 µGy h-1), moderate (n = 10, 5.7-15.6 µGy h-1), low (n = 12, 0.23-1.14 µGy h-1) and control (n = 20, 0.04-0.07 µGy h-1). After spleen extraction from rodents, spleen cell culture was performed to obtain metaphase spreads. Chromosome aberrations were assessed on Giemsa-stained metaphase spreads. RESULTS: Although the mice in the contaminated areas were chronically exposed, there was no radiation-specific chromosome aberrations observed, such as dicentric chromosomes and rings. Some structural aberrations such as gaps and breaks were observed, and these frequencies decreased annually in mice from Namie Town. CONCLUSION: These findings suggest that chromosome aberration analysis is useful to evaluate and monitor radiation effects in wild animals.

Anomalous plutonium isotopic ratios in sediments of Lake Qinghai from the Qinghai-Tibetan Plateau, China.

The vertical profiles of (239+240)Pu and (137)Cs activities and (240)Pu/(239)Pu isotopic ratios are determined for three sediment cores of Lake Qinghai from the Qinghai-Tibetan Plateau, China, and compared with those in sediments of another three lakes (Lakes Bosten, Sugan, and Shuangta), the only existing ones closest to Lop Nor area, China's nuclear weapons test site in the northwestern part of the country. The mean inventory of 47.7 ± 18.7 MBq km(-2) for (239+240)Pu activity in Lake Qinghai is comparable to the average value of global fallout expected at the same latitude, yet the mean inventory of 1112.0 ± 78.0 MBq km(-2) for (137)Cs is slightly lower than that of global fallout. Anomalously low (240)Pu/(239)Pu isotopic ratios (0.038-0.125) were found in the 3-6.5 cm deep sediment layers, indicating the trace Pu input from early nuclear weapons research activities at Atomic City in the lake's watershed during the 1950-60s. Model calculation indicated that the Pu input accounted for approximately 5-16% of the total Pu inventory. The observation of low (240)Pu/(239)Pu ratio in the deep sediment layer provided a new time marker for recent sediment dating in the lake and around the area. The results are of great significance to the further understanding of sources, records, and environmental impacts of global and regional nuclear activities in the environment and provide important chronological information for further studies on the water eutrophication process and climatic change, and reconstruction of pollution history of organic contaminants and heavy metals in the watershed of Lake Qinghai.

Pu and 137Cs in the Yangtze River estuary sediments: distribution and source identification.

Pu isotopes and (137)Cs were analyzed using sector field ICP-MS and γ spectrometry, respectively, in surface sediment and core sediment samples from the Yangtze River estuary. (239+240)Pu activity and (240)Pu/(239)Pu atom ratios (>0.18) shows a generally increasing trend from land to sea and from north to south in the estuary. This spatial distribution pattern indicates that the Pacific Proving Grounds (PPG) source Pu transported by ocean currents was intensively scavenged into the suspended sediment under favorable conditions, and mixed with riverine sediment as the water circulated in the estuary. This process is the main control for the distribution of Pu in the estuary. Moreover, Pu is also an important indicator for monitoring the changes of environmental radioactivity in the estuary as the river basin is currently the site of extensive human activities and the sea level is rising because of global climate changes. For core sediment samples the maximum peak of (239+240)Pu activity was observed at a depth of 172 cm. The sedimentation rate was estimated on the basis of the Pu maximum deposition peak in 1963-1964 to be 4.1 cm/a. The contributions of the PPG close-in fallout Pu (44%) and the riverine Pu (45%) in Yangtze River estuary sediments are equally important for the total Pu deposition in the estuary, which challenges the current hypothesis that the riverine Pu input was the major source of Pu budget in this area.

Temporal trend of 240Pu/239Pu atom ratios in water columns in the Western North Pacific Ocean and its marginal seas.

The 240Pu/239Pu atom ratios were determined by inductively coupled plasma mass spectrometry for seawater samples from the Okinawa Trough in the western North Pacific Ocean margin to identify their Pu sources and to elucidate the temporal variability in atom ratios in the water columns in the western North Pacific Ocean and its marginal seas. The 239Pu, 240Pu and 239+240Pu water column inventories were 12.2 ± 0.5, 10.5 ± 0.5 and 22.7 ± 0.7 Bq m-2, respectively. The observed 240Pu/239Pu ratios were clearly greater than the mean global fallout ratio of ∼0.18 with a mean value of 0.236 ± 0.014. The observed greater atom ratios confirmed the presence of close-in fallout Pu from nuclear testing at the Pacific Proving Grounds (PPG). The relative percentage of the PPG-derived Pu to global fallout Pu was estimated as 41 ± 10%. The 239+240Pu water column inventory originating from the PPG close-in fallout was also calculated as 9.2 ± 0.4 Bq m-2. The temporal variability in the mean 240Pu/239Pu atom ratios in the water columns in the western North Pacific Ocean and its marginal seas was obtained through comparison of the present study values and the previously reported values, and it had no significant temporal variation with a mean value of 0.237 ± 0.004 during the observation period of 1984-2015. The 239Pu and 240Pu derived from the two different sources of global fallout and the close-in fallout at the PPG were homogenized in the water masses in the studied areas.

Effects of environmental conditions, low-level potassium, ethylenediaminetetraacetic acid, or combination treatment on radiocesium-137 decontamination in Napier grass.

Phytoextraction is widely used to remove environmental pollutants such as heavy metals or radionuclides from soil. It is important to understand how to enhance the accumulation of contaminants by plants. Previously, we found that Napier grass (Pennisetum purpureum Schum.) has the potential to effectively remove Cs (133Cs and 137Cs). In order to enhance the remediation efficiency of Napier grass, we evaluated the effects of low-level K (K), ethylenediaminetetraacetic acid (EDTA), or the combination of low-level K and EDTA (K+EDTA). We also examined the differences in 137Cs decontamination between two cropping years (2018 and 2019). Overall, there were no prominent effects from the K, EDTA, or K+EDTA treatments on plant growth (plant height, tiller number), aboveground biomass, 137Cs concentration, and 137Cs removal ratio (CR) in 2 years. However, the aboveground biomass (P < 0.001), 137Cs concentration (P < 0.001 in 2019 only), and CR (P < 0.001) in plants grown in the first growing period were significantly higher than in plants grown in the second growing period in both years. The mean 137Cs concentration (P < 0.001) and total CR (P < 0.001) per year was significantly greater in 2019 than in 2018. The precipitation amount during the cultivation period in 2019 (1197 mm) was 1.8-fold higher than in 2018 (655 mm). In this study, the K, EDTA, and K+EDTA treatments had less effect plant growth than the natural environmental conditions. To enhance remediation efficiency, soil moisture is one important factor to produce more aboveground biomass to achieve high CR in Napier grass.