Reactive barriers for 137Cs retention

137Cs was dispersed globally by cold war activities and, more recently, by the Chernobyl accident. Engineered extraction of 137Cs from soils and groundwaters is exceedingly difficult. Because the half-life of 137Cs is only 30.2 years, remediation might be more effective (and less costly) if 137Cs bioavailability could be demonstrably limited for even a few decades by use of a reactive barrier. Essentially permanent isolation must be demonstrated in those few settings where high nuclear level wastes contaminated the environment with 135Cs (half-life 2.3 x 10(6) years) in addition to 137Cs. Clays are potentially a low-cost barrier to Cs movement, though their long-term effectiveness remains untested. To identify optimal clays for Cs retention, Cs desorption was measured for five common clays: Wyoming Montmorillonite (SWy-1), Georgia Kaolinites (KGa-1 and KGa-2), Fithian Illite (F-Ill), and K-Metabentonite (K-Mbt). Exchange sites were pre-saturated with 0.16 M CsCl for 14 days and readily exchangeable Cs was removed by a series of LiNO3 and LiCl washes. Washed clays were then placed into dialysis bags and the Cs release to the deionized water outside the bags measured. Release rates from 75 to 139 days for SWy-1, K-Mbt and F-Ill were similar; 0.017% to 0.021% sorbed Cs released per day. Both kaolinites released Cs more rapidly (0.12% to 0.05% of the sorbed Cs per day). In a second set of experiments, clays were Cs-doped for 110 days and subjected to an extreme and prolonged rinsing process. All the clays exhibited some capacity for irreversible Cs uptake. However, the residual loading was greatest on K-Mbt (approximately 0.33 wt.% Cs). Thus, this clay would be the optimal material for constructing artifical reactive barriers.     

Distribution coefficients (Kd) and desorption rates of Cs and Am in Black Sea sediments

The distribution coefficients (K_d) and desorption rates of ¹³⁷Cs and ²⁴¹Am radionuclides in bottom sediments at different locations in the Black Sea were studied under laboratory conditions. The K_d values were found to be 500 for ¹³⁷Cs and 3800 for ²⁴¹Am at the steady state and described exponential curves. Rapid uptake of the radionuclides occurred during the initial period and little accumulation happened after four days. The desorption rates for ¹³⁷Cs in different bottom sediments were best described by a three-component exponential model. The desorption half-times of ¹³⁷Cs ranged from 26 to 50 d at the slow components. However, the desorption rate of ²⁴¹Am described one component for all sediment samples and desorption half-time was found to be 75 d. In general, the results showed that the ²⁴¹Am radionuclide is more effectively transferred to bottom sediment and has longer turnover time than ¹³⁷Cs under Black Sea conditions.     

The use of clays to sequestrate organic pollutants. Leaching experiments

Leaching experiments are performed from clay-pollutant systems in order to evaluate the capability of clays to sequestrate organic pollutants from wastewaters. Reference kaolinite KGa-1b, montmorrillonite SWy-2 and reference soil BCR^®-700 are the sorbent materials. 2,4,6-trichloroaniline (2,4,6-TCA) and 4-chlorophenol (4-CP) are the typical pollutants, sorbed at amounts of 10.0 mg g⁻¹ and 5.8 mg g⁻¹ on SWy-2 and 7.3 mg g⁻¹ and 2.2 mg g⁻¹ on KGa-1b, respectively.The leaching agents are ultrapure water and model solutions of acid rain and surface waters that simulate meteoric leaching. 1.0 mM HNO₃, 1.0 mM H₂SO₄ solutions and a methanol/water 50/50 (v/v) mixture simulate leaching agents of industrial source.The results are compared and the preferential capability of the clays to sequestrate the more lipophilic 2,4,6-TCA is evidenced.The bond interactions are discussed and explained through preferential adsorption reactions. For montmorrillonite also a simultaneous intercalation in the phyllosilicate interlayer is proposed.     

Role of magnetite and humic acid in radionuclide migration in the environment

Sorption of ¹³⁷Cs, ⁹⁰Sr, ¹⁵⁴Eu and ¹⁴¹Ce by magnetite has been studied at varying pH (4 to 11) in the presence and absence of humic acid. The sorption studies have also been carried out at varying ionic strength (0.01 to 0.2 M NaClO₄) and humic acid concentration (2 to 20 mg/L). Percentage sorption of ¹³⁷Cs and ⁹⁰Sr was found to be pH dependent, with the sorption increasing with increasing pH of the suspension. At any pH, the percentage sorption of ⁹⁰Sr was higher than that of ¹³⁷Cs. The results have been explained in terms of the electrostatic interaction between the positively charged metal ions and the surface charge of the magnetite which becomes increasingly negative with increasing pH. On the other hand, ¹⁵⁴Eu and ¹⁴¹Ce were found to be strongly sorbed by the magnetite at all pH values, with the sorption being independent of pH. The strong sorption of trivalent and tetravalent metal ions suggests the role of complexation reactions during sorption, apart from the electrostatic interactions. However, in the case of ¹⁴¹Ce surface precipitation of Ce(III) formed by reduction of Ce(IV) in the presence of magnetite cannot be ruled out. Presence of humic acid (2 mg/L) was found to have negligible effect on sorption of all metal ions.     

C?sium-137 in B?den saarl?ndischer Wald?kosysteme

Zusammenfassung Ziel und Schwerpunkte  Um das Verhalten des künstlichen Radionuklids¹³⁷Cs im Landschaftshaushalt der Saar-Lor-Lux Region zu klaren, wurdend die r?umliche Verteilung sowie das deszendente Migrationsverhalten und die Tiefenfunktionen des Radioisotops in den wichtigsten Bodensubstraten saarl?ndischer Wald?kosysteme untersucht. Ergebnisse  Demnach finden sich die h?chsten¹³⁷Cs-Aktivit?ten im Norden des Landes, w?hrend die Gebiete im Süden und Südosten deutlich geringere Konzentrationen aufweisen. Es konnten deszendente Migrationsraten zwischen 0,25 cm/a und 1,0 cm/a festgestellt werden. Durchschnittlich treten die h?chsten Migrationsraten in den tonig-schluffigen Substraten des Muschelkalks auf (0,66 cm/a), gefolgt von den lehmig ausgepr?gten Substraten des Unterrotliegenden (0,53 cm/a) und den sandigen Substraten des Buntsandsteins (0,41 cm/a). In den tonarmen Bodensubstraten des Unterrotliegenden und des Buntsandsteins lassen sich 90–95% der Aktivit?ten in den oberen 10 cm der humusreichen Oberb?den nachweisen, wohingegen in den tonreichen Substraten des Muschelkalks bis zur gleichen Tiefe nur etwa 70–76% zu finden sind. Schlussfolgerungen  Mit einem Abnehmen der als Leitbahnen fungierenden Prim?r-und Sekund?rporen in zunehmender Tiefe ist künftig mit einer deutlichen Reduzierung der Verlagerungsgeschwindigkeit von¹³⁷Cs in den Substraten des Muschelkalks zu rechnen. Insbesondere bei geringm?chtigen B?den auf kluftreichem Ausgangsgestein impliziert die maximale Eindringtiefe des Isorops von 40 cm in den Unterboden jedoch eine m?gliche Kontamination des oberfl?chennahen Grundwassers, ebenso wie an Standorten mit hohem Grundwasserstand. Ausblick  Aufgrund der hier vorgestellten Ergebnisse wurde ein¹³⁷Cs-Monitoring in das Boden-Dauerbeobachtungsprogramm des Landesamts für Umweltschutz des Saarlandes aufgenommen Online-First: 25. April 2000     

Sorption studies of chloroanilines on kaolinite and montmorillonite

Batch experiments have been performed in order to evaluate the ability of the two reference clays kaolinite (KGa-1) and Na-montmorillonite (SWy-1) to retain three representative chloroanilines: 3-chloroaniline, 3,4-dichloroaniline and 2,4,6-trichloroaniline. Systems containing the clay mineral and the pollutant solution (at concentration levels ranging between 1.0 and 10.0mg/L) were considered and RP-HPLC methods were employed to follow the sorption processes as a function of time. The results indicate that montmorillonite shows a general higher sorption capacity with respect to kaolinite and that for both the reference clays, in the concentration range investigated, the amount of pollutant sorbed increases with concentration. The sorption coefficient K(d) ranges between 0.0030 L/g for the system 3-chloroaniline-kaolinite and 0.0488L/g for the system 2,4,6-trichloroaniline-montmorrillonite. The most lipophilic trichloroaniline shows the greater sorption. X-ray analyses suggest for kaolinite a preferential sorption onto the mineral surface, while for montmorillonite a progressive swelling of the structure is observed, likely due to sorption processes that also take place in the interlayer.     

Experimental evidence of biomass burning as a source of atmospheric 137Cs,puy de Dôme (1465 m a.s.l.), France

The presence of cesium-137 (¹³⁷Cs) in the environment is mainly due to past nuclear tests and accidental reactor releases. Due to the half-life of ¹³⁷Cs (30.2 y), amounts of this radionuclide releases are in fact still detectable in soils, and at trace levels in the vegetation and the atmosphere. Since the middle of the 1990’s, the presence of ¹³⁷Cs in the atmosphere has long been attributed to the resuspension of terrestrial dust. Recently, modelling studies have demonstrated that an additional and possibly dominant source of this anthropogenic radionuclide is biomass burning. Here, we report the variations of atmospheric ¹³⁷Cs activity levels over a 2-year period at the puy de Dôme (1465 m a.s.l.), France in combination with measurements of the aerosol chemical composition, in particular with indicators for biomass burning (levoglucosan and potassium) and soil dust (calcium). Temporal co-variations of these chemical compounds in addition to back-trajectories are used to identify common source emissions. Significant correlation is found between these compounds. Hence, we experimentally confirm the modelling study highlighting the fact that the atmospheric ¹³⁷Cs is partly released by biomass burning. In addition, we observed that the correlations between the ¹³⁷Cs concentrations and levoglucosan and biomass burning K⁺ differ according to the season. This is in agreement with the temporal evolution of levoglucosan concentration, which has maxima in winter and minima in summer.     

Chemical and biological release of 14C‐bound residues from soil treated with 14C‐p,p'‐DDT

Abstract

¹⁴C‐p,p'‐DDT‐bound residues in soil can be released by treatment with concentrated sulphuric acid at ambient temperatures. Within 6 days, about 70% of the bound residues was released. Bound residues released after 9 months incubation with ¹⁴C‐DDT showed the presence of DDT and DDE only while bound residues released after 18 months, contained in addition 13% DDD.

Release of bound ¹⁴C‐residues also occurs readily following inoculation of the soil‐bound residues with fresh soil or with individual microorganisms. Almost complete release of bound residues was observed after incubation for 45 days. The rate of release was rapid during the first two weeks and decreased thereafter. TLC and HPLC analysis showed that the released residues contained DDE (about 80%) and a smaller amount of DDD. The disappearance of DDT from the released residues may be attributed to its microbiological degradation to DDE and DDD, shortly after its release.     

Long term investigation of 137Cs in chicken meat and eggs from northwest Croatia

Abstract

This paper presents the results of long-term investigations of ¹³⁷Cs activity concentrations in chicken meat and eggs from northwest Croatia for the period 1987–2018. The research has been done as a part of monitoring program of radioactive contamination in Croatia. The highest activity concentrations in both of these foodstuffs were measured in 1987 and have been decreasing exponentially ever since. The Fukushima-Daiichi accident in 2011 did not cause any increase of ¹³⁷Cs activity concentrations. The ecological half-life for ¹³⁷Cs was estimated to be 8.0 and 8.4?years for chicken meat and eggs respectively. The correlation between ¹³⁷Cs in fallout and chicken meat as well as between ¹³⁷Cs in fallout and eggs is very good, the respective correlation coefficients being 0.79 and 0.72, indicating that fallout was the main source of ¹³⁷Cs contamination in both foodstuffs. The estimated effective doses received by adult members of the Croatian population due to the intake of radiocaesium by chicken meat and egg consumption for the overall observed period are very small, 2.0 and 0.6 µSv respectively. Therefore, chicken meat and chicken egg consumption was not a critical pathway for the transfer of radiocaesium to humans.     

Fate of radiocesium in sewage treatment process released by the nuclear accident at Fukushima

The nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) which occurred after the Great East Japan Earthquake on March 11, 2011 resulted in releases of radionuclides such as ¹³⁴Cs (half-life:T_1/2 = 2.06 yr), ¹³⁷Cs (T_1/2 = 30.04 yr) and ¹³¹I (T_1/2 = 8.05 d) to the environment. For this paper, we observed the monthly variations of radiocesium (¹³⁴Cs and ¹³⁷Cs) and stable Cs concentrations in influent, effluent, sewage sludge, and sludge ash collected from a sewage treatment plant 280 km north of the FDNPP from July to December, 2011. Using the stable Cs results, we concluded the mass balance of Cs in the sewage treatment plant showed that about 10% of the Cs entering the sewage treatment plant would be transferred to the sewage sludge, and then Cs in the sewage sludge was totally recovered in the sludge ash. The behavior of Cs was similar to that of Rb, but it was not similar to that of K in the sewage treatment process.     

Fate in soil of 14C-sulfadiazine residues contained in the manure of young pigs treated with a veterinary antibiotic

The fate of ¹⁴C-labeled sulfadiazine (¹⁴C-SDZ) residues was studied in time-course experiments for 218 days of incubation using two soils (A_p horizon of loamy sand, orthic luvisol; A_p horizon of silt loam, cambisol) amended with fresh and aged (6 months) ¹⁴C-manure [40 g kg^?1 of soil; 6.36 mg of sulfadiazine (SDZ) equivalents per kg of soil], which was derived from two shoats treated with ¹⁴C-SDZ. Mineralization of ¹⁴C-SDZ residues was below 2% after 218 days depending little on soil type. Portions of extractable ¹⁴C (ethanol-water, 9:1, v/v) decreased with time to 4–13% after 218 days of incubation with fresh and aged ¹⁴C-manure and both soils. Non-extractable residues were the main route of the fate of the ¹⁴C-SDZ residues (above 90% of total recovered ¹⁴C after 218 days). These residues were high immediately after amendment depending on soil type and aging of the ¹⁴C-manure, and were stable and not remobilized throughout 218 days of incubation. Bioavailable portions (extraction using CaCl₂ solution) also decreased with increasing incubation period (5–7% after 218 days). Due to thin-layer chromatography (TLC), 500 μg of ¹⁴C-SDZ per kg soil were found in the ethanol-water extracts immediately after amendment with fresh ¹⁴C-manure, and about 50 μg kg^?1 after 218 days. Bioavailable ¹⁴C-SDZ portions present in the CaCl₂ extracts were about 350 μg kg^?1 with amendment. Higher concentrations were initially detected with aged ¹⁴C-manure (ethanol-water extracts: 1,920 μg kg^?1; CaCl₂ extracts: 1,020 μg kg^?1), probably due to release of ¹⁴C-SDZ from bound forms during storage. Consistent results were obtained by extraction of the ¹⁴C-manure-soil samples with ethyl acetate; portions of N-acetylated SDZ were additionally determined. All soluble ¹⁴C-SDZ residues contained in ¹⁴C-manure contributed to the formation of non-extractable residues; a tendency for persistence or accumulation was not observed. SDZ's non-extractable soil residues were associated with the soluble HCl, fulvic acids and humic acids fractions, and the insoluble humin fraction. The majority of the non-extractable residues appeared to be due to stable covalent binding to soil organic matter.     

Dissipation and Leaching of 14C-Monocrotophos in Soil Columns under Subtropical Climate

Dissipation and leaching behavior of ¹⁴C-monocrotophos was studied for 365 days under field conditions using PVC cylinders. The first set (24 cylinders) was spiked with 1.0 μCi ¹⁴C-labeled monocrotophos along with 1.06 mg unlabeled monocrotophos to give a concentration of 2 mg kg ^?1 in the soil up to 15 cm depth. The second set (24 cylinders) received ¹⁴C-labeled monocrotophos along with other non-labeled insecticides viz., dimethoate @ 300 g a.i ha^?1, deltamethrin @ 12.5 g a.i ha^?1, endosulfan @ 750 g a.i ha^?1, cypermethrin @ 60 g a.i ha^?1, and triazophos @ 600 g a.i ha^?1 at an interval of 15 days each as recommended for the cotton crop. ¹⁴C-monocrotophos dissipated faster, up to 45% in first 90 days in columns treated with only monocrotophos compared to 25% in columns that received monocrotophos along with other insecticides. However, both the columns showed similar residues 180 days onward. After 180 days of treatment, 46% radiolabeled residues were observed, which reduced up to 39.6% after 365 days. Leaching of ¹⁴C-monocrotophos to 15–30 cm soil layer was observed in both the experimental setups. In the 15–30 cm soil layer of both soil columns, up to 0.19 mg ¹⁴C-monocrotophos kg^?1d. wt. soil was detected after 270 days.     

Impact of an exceptional Saharan dust outbreak in France: PM10 and artificial radionuclides concentrations in air and in dust deposit

The present study focuses on the exceptional Saharan dust event that affected most of France in February 2004. Activity levels of various artificial radionuclides (⁹⁰Sr, ¹³⁷Cs, uranium, thorium and plutonium isotopes, ²⁴¹Am) were examined. Activity or isotopic ratios are discussed in the context of atmospheric nuclear weapons tests, among them French tests performed in Sahara in the 1960s. The daily evolution of ¹³⁷Cs activity levels in the atmosphere was compared to daily PM₁₀ change. A link between airborne ¹³⁷Cs and PM₁₀, is given. It is estimated that this 2-day event deposited as much ¹³⁷Cs as would be deposited on average over a 10-month period. The amount of deposited ¹³⁷Cs and ^239+240Pu represents respectively about 0.1 and 1% of the activity already present in the soil. Such Saharan dust events correspond to an extreme type of “feeder” process of artificial radionuclides in the atmosphere. Therefore, they contribute to the long term background level of artificial radionuclides kept at trace levels in the atmosphere.     

Migration of Cs through quartz sand: experimental results and modeling approaches

We present results from experiments on the migration of ¹³⁷Cs through columns containing quartz sand. Times for ¹³⁷Cs movement through these columns and the quantity of ¹³⁷Cs adsorbed by the sand decreased as the ionic strength of the pore water increased from 0.002 to 0.1 m. The breakthrough curves were characterized by a slow approach towards steady-state concentrations as well as by long tails, indicating that ¹³⁷Cs adsorption to the sand grains was, at least in part, controlled by rate-limited reactions. Various formulations for solute mass transfer were tested for their ability to fit the experimental breakthrough curves. Based on a statistical analysis, a nonlinear, two-site model was identified as the most appropriate for describing the suite of experimental data. Variation in the model parameter that describes the rate of ¹³⁷Cs adsorption to the sand showed no consistent pattern with changes in ionic strength. In contrast, model parameters describing the sorption capacity of the sand grains and the fraction of kinetic sorption sites on the sand decreased with increasing ionic strength. The parameter describing the rate of ¹³⁷Cs desorption varied directly with changes in ionic strength.     

Impact of repeated pesticide applications on the binding and release of methyl 14C-monocrotophos and U-ring labelled 14C-carbaryl to soil matrices under field conditions

The dissipation of (O-methyl-¹⁴C) monocrotophos and U-ring labelled ¹⁴C-carbaryl was monitored for over two years in absence and presence of other insecticides using in situ soil columns. The dissipation of ¹⁴C-monocrotophos from soil treated with methomyl and carbaryl showed a faster rate of downward movement than in a control column tagged with the labelled insecticide alone. The same trend was observed in experiments with ¹⁴C-carbaryl that dissipated more readily in soil treated with non-labelled monocrotophos and methomyl. In the presence of other insecticides the percentage of bound residues was generally lower than in control experiments. The bound residues at the top of the column are released at a low rate under conditions prevailing in the field. The overall time required for dissipation of 50% of monocrotophos and carbaryl (t₅₀) as estimated from control experiment was approximately 20 and 24 weeks, respectively. The data indicate that repeated applications of pesticides might enhance the release of ¹⁴C-bound residues.     

Artificial radioactivity in environmental media (air, rainwater, soil, vegetation) in Austria after the Fukushima nuclear accident

Several environmental media in Austria were monitored for artificial radionuclides released during the Fukushima nuclear accident. Air (up to 1.2 mBq/m³ particulate ¹³¹I) and rainwater (up to 5.2 Bq/L ¹³¹I) proved to be the media best suited for the environmental monitoring, allowing also a temporal resolution of the activity levels. Significant regional differences in the wet deposition of ¹³¹I with rain could be observed within the city of Vienna during the arrival of the contaminated air masses. Forward-trajectory analysis supported the hypothesis that the contaminated air masses coming from the northwest changed direction to northeast over Northern Austria, leading to a strong activity concentration gradient over Vienna. In the course of the environmental monitoring of the Fukushima releases, this phenomenon—significant differences of ¹³¹I activity concentrations in rainwater on a narrow local scale (8.1 km)—appears to be unique. Vegetation (grass) was contaminated with ¹³¹I and/or ¹³⁷Cs at a low level. Soil (up to 22 Bq/kg ¹³⁷Cs) was only affected by previous releases (nuclear weapon tests, Chernobyl). Here, also significant local differences can be observed due to different deposition rates during the Chernobyl accident. The effective ecological half-lives of ¹³⁷Cs in soil were calculated for four locations in Austria. They range from 7 to 30 years. No Austrian sample investigated herein exceeded the detection limit for ¹³⁴Cs; hence, the Fukushima nuclear accident did not contribute significantly to the total radiocesium inventory in Austrian environmental media. The levels of detected radioactivity were of no concern for public health.     

Biodegradation of Trifluralin in Harran Soil

Abstract

Degradation of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) was investigated in soils taken from three different locations at Harran region of Turkey under laboratory conditions. Surface (0–10 cm) soils, which were taken from a pesticide untreated field Gürgelen, Harran-1 and Ikizce regions in the Harran Plain, were incubated in biometer flasks for 350 days at 25°C. Ring-UL-¹⁴C-trifluralin was applied at the rate of 2 µg g^?1 with 78.7 kBq radioactivity per 100 g soil flask. Evolved ¹⁴CO₂ was monitored in KOH traps throughout the experiment. Periodically, soil sub-samples were removed and extracted by supercritical fluid extraction (SFE). Unextractable soil-bound ¹⁴C residues were determined by combustion. During the 350 days incubation period 6.6, 5.4, and 3.3% of the applied radiocarbon was evolved as ¹⁴CO₂ from the Harran-1, Gürgelen, and Ikizce soil, respectively. At the end of 350 days the SFE-extractable and bound ¹⁴C-trifluralin residues were 39.0 and 29.2% of the initially applied herbicide in Gürgelen soil. The corresponding values for Harran-1 and Ikizce soils were 36.2, 28.4% and 41.6, 18.5% respectively.     

Radioactive isotopes in atmospheric aerosols over Russia and the Sea of Japan following nuclear accident at Fukushima Nr. 1 Daiichi Nuclear Power Station in March 2011

Artificial radionuclides, such as iodine-131 (¹³¹I), cesium-134 (¹³⁴Cs), and cesium-137 (¹³⁷Cs), as well as natural isotopes of beryllium-7 (⁷Be) and potassium-40 (⁴⁰K) have been registered in atmospheric aerosols over Vladivostok selected from 11 March to 17 June 2011. Additionally, ¹³⁴Cs and ¹³⁷Cs were detected in atmospheric aerosols over Tomsk selected from 16 March to 17 June 2011. Artificial radionuclides were also discovered in atmospheric wet depositions sampled in Vladivostok from 3 to 17 May 2011. Moreover, these radionuclides have been registered in atmospheric aerosols over the sea surface of the Sea of Japan selected from 3 to 31 May 2011 during an expedition of the “Nadezhda” sailing ship. From 18 March to 15 April, an increase in concentrations of atmospheric aerosols over Vladivostok from 108.8 to 321.5 μg/m³ has been registered. It was accompanied by increased activity concentrations of ¹³⁴Cs, ¹³⁷Cs, and the ¹³¹I. During the period from 18 March to 15 April, activity concentrations of ¹³⁷Cs and ¹³⁴Cs in atmospheric aerosols increased 100 times compared with the minimum detectable concentration (MDC) level and peaked in the weekly sample gathered from 8 to 15 April (145.0 and 105.3 μBq/m³, respectively). Variability of concentrations of natural isotopes of ⁷Be and ⁴⁰K was not greater than 1 order of magnitude throughout the sampling period. Maximal values of ¹³⁷Cs and ¹³⁴Cs concentrations (1,281.5?±?141 and 384.4?±?42.3 μBq/m³, respectively) in Tomsk were reached in samples taken from 1 to 2 April. For the atmospheric aerosol samples from the Sea of Japan, the largest concentration of ¹³¹I (392.3?±?215.7 μBq/m³) was detected from 13 to 19 May, while all other samples had much lower concentration values. Synoptic analysis of back trajectories movement of air masses showed that the radioactive cloud came to Vladivostok from the regions of Siberia and northeastern part of China. Synoptic analysis for Tomsk showed that during the period of maximal activity concentrations (1–9 April), air masses were arriving from the European part of Russia and north of Kazakhstan.     

Metabolic fate of the 14C-labeled herbicide clodinafop-propargyl in soil

The metabolic fate of ¹⁴C-phenyl-labeled herbicide clodinafop-propargyl (CfP) was studied for 28 days in lab assays using a soil from Germany (A_p horizon, silt loam, and cambisol). Mineralization amounted to 12.40% of applied ¹⁴C after 28 days showing a distinct lag phase until day 7 of incubation. Portions of radioactivity extractable by means of 0.01 M CaCl₂ solution (bioavailable fraction) decreased rapidly and were 4.41% after 28 days. Even immediately after application, only 57.31% were extracted with the aqueous solvent. Subsequent extraction using accelerated solvent extraction (ASE; acetonitrile/water 4:1, v/v) released 39.91% of applied ¹⁴C with day 0 and 26.16% with day 28 of incubation from the samples. Non-extractable portions of radioactivity thus, increased with time amounting to 11.99% (day 0) and 65.00% (day 28). A remarkable increase was observed between 14 and 28 days correlating with the distinct increase of mineralization. No correlation was found throughout incubation with general microbial activity as determined by DMSO reduction. Analysis of the CaCl₂ and ASE extracts by radio-TLC, radio-HPLC and GC/MS revealed that CfP was rapidly cleaved to free acid clodinafop (Cf), which was further (bio-) transformed; DT₅₀ values (based on radio-TLC detection of the parent compound) were far below 1 day (CfP) and about 7 days (Cf). TLC analysis pointed to 2-(4-hydroxyphenoxy)-propionic acid as further metabolite. Due to fractionation of non-extractable residues, most of the ¹⁴C was associated with fulvic and humic acids, portions in humin fractions and non-humics were moderate and low, respectively. Using a special strategy, which included pre-incubation of the soil with CfP and then mineralization of ¹⁴C-CfP as criterion, a microorganism was isolated from the soil examined. The microorganism grew using CfP as sole carbon source with concomitant evolution of ¹⁴CO₂. The bacterium was characterized by growth on commonly used carbon sources and by 16S rDNA sequence analysis. The sequence exhibited high similarity with that of Rhodococcus wratislaviensis (99.56%; DSM 44107, NCIMB 13082).     

Studies on the dissipation of 14C‐DDT from water and solid surfaces

Abstract

Dissipation of ¹⁴C‐p,p'‐DDT from water was studied for 180 days under outdoor conditions. DDT dissipated rapidly with overall half‐life of 53 days. The main degradation products were p,p'‐DDE and p,p'‐DDD. A portion of ¹⁴C‐residues was found in the sediment plus biomass (pellet) and on the inner surface of the glass container. This amounted to 7.2 and 6.7% of the initially added radioactivity, respectively. After 6 months, bound¹⁴C was more as compared to extractable ¹⁴C and p,p'‐DDD was the major metabolite of p,p'‐DDT in the extractable fraction. DDT dissipated from clay plates under indoor conditions with an overall half‐life of 160 days.