Urban storm water transport and wash-off of Cæfesium-137 after the chernobyl accident

Radiation protection planning in urban areas after a radioactive fallout requires knowledge of decontamination caused by storm water transport. This report elucidates the transport of ¹³⁷Cs from a roof and three storm sewers in Uppsala during the first rainfall after those, on 29–30 April 1986, causing the Chernobyl contamination. Runoff and concentration Of ¹³⁷Cs in storm water were determined with an accuracy of 10 to 15%. The origin of storm water was determined from its content of ¹⁸O. Surface contamination was measured on 3 July 1986. Total fallout was 25 kBq m^?2. During the rainfall on 11 May, 4 kBq m^?2 were transported from the roof and approximately 1 kBq m^?2 from the sewered areas. From 30 April to 4 July there was a decontamination of 13 to 20 kBq m^?2. Measurements from another project showed that the fallout rain events washed off 10 to 16 kBq m^?2. The wash-off by the small rainfall on 11 May constituted one third of the remaining decontamination occurring up until 4 July. The transport of ¹³⁷Cs during the 11 May event increased when the runoff increased, but was less efficient as the event proceeded. The relations between ¹³⁷Cs concentrations and runoff implied that the wash-off of ¹³⁷Cs in Uppsala was totally dominated by that bound to particles.     

Cadastral valuation of land contaminated with radionuclides

The methodology and procedure for cadastral valuation of land in the areas contaminated with radionuclides are presented. The efficiency of rehabilitation measures applied to decrease crop contamination to the levels satisfying sanitary-hygienic norms is discussed. The differentiation of cadastral value of radioactively contaminated agricultural lands for the particular farms and land plots is suggested. An example of cadastral valuation of agricultural land contaminated during the Chernobyl Nuclear Power Plant accident is given. It is shown that the use of sandy and loamy sandy soddy-podzolic soils with the ¹³⁷Cs contamination of 37–185 and >185 kBq/m² for crop growing is unfeasible. The growing of grain crops and potatoes on clay loamy soddy-podzolic soils with the ¹³⁷Cs contamination of 555–740 kBq/m² is unprofitable. The maximum cadastral value of radioactively contaminated lands is typical of leached chernozems.     

Radionuclide Behaviour and Transport in a Coniferous Woodland Ecosystem: The Distribution of Radionuclides in Soil and Leaf Litter

A coniferous woodland in the vicinity of theBritish Nuclear Fuels reprocessing plant atSellafield, Cumbria, was used to examine the spatial,temporal and depth distribution of ¹³⁴Cs,¹³⁷Cs, ²³⁸Pu, ^239+240Pu and ²⁴¹Amin soil and leaf litter. All the radionuclides, withthe exception of ¹³⁴Cs, showed a consistent fallin accumulated soil and litter deposits withincreasing distance from the woodland edge nearest toSellafield. ¹³⁷Cs levels in soil declined from 53to 28 kBq m^-2, ^239+240Pu from 5.5 to 3.6 kBqm^-2 and ²⁴¹Am from 2.9 to 1.1 kBq m^-2within 100 m of the forest edge. This decline isattributed to greater deposition occurring at theleading edge of the woodland. The uniform depositionpattern of ¹³⁴Cs in soil is consistent with thehypothesis that, at the time of sampling, thesedeposits derived largely from wet deposition duringpassage of the Chernobyl plume over Cumbria in May1986. Results for the leaf litter indicate a similarspatial distribution to that observed in soil.Radionuclide concentrations were also similar but thisis not attributable to adventitious soil contaminationbecause significant differences between isotopicratios of ¹³⁴Cs:¹³⁷Cs and ²³⁸Pu:^239+240Pu imply that the contamination on leaflitter is of more recent origin than that in soils.     

Radioactive contamination of permafrost-affected soils with 137Cs and 90Sr, the products of an accidental underground nuclear explosion

The specificity of contamination of permafrost-affected soils with radionuclides derived from an accidental underground nuclear explosion at the Kraton-3 polygon located in the northern taiga subzone has been studied in northwestern Yakutia. It is shown that the high density of the radioactive contamination is preserved in the soils 23 years after the nuclear accident. The concentrations of ¹³⁷Cs and ⁹⁰Sr vary from 34 to 1025 and from 57 to 781 kBq/m², respectively, which is 30–1000 times higher than the global fallout of these radionuclides.     

Atmospheric Deposition of Acidifying Components to a Japanese Cedar Forest

One-year field measurements were conducted in a Japanese cedar (Cryptomeria japonica) forest, located in Gunma Prefecture, Japan. On the basis of the meteorological and atmospheric concentration data, the dry deposition of SO₂, HNO₃, NO₂ and HCl was estimated using the inferential method. The annual dry deposition of H⁺ was estimated at 721 eq ha^?1yr^?1, which was 40% larger than the measured annual wet deposition of H⁺ (514 eq ha^?1yr^?1). Therefore, dry deposition is an important pathway for the atmospheric input of H⁺ to the forest in the study site. The contribution of each gas to the dry deposition of H⁺ was as follows: SO₂, 25%; HNO₃, 32%; NO₂, 10%; and HCl, 33%. The extremely high contribution of HCl appeared to be caused by the high emission intensity of HCl due to waste incineration in the site region. The differences between estimated deposition and throughfall and stemflow measurements indicated that about 80% of the total deposition of H⁺ was taken up by the canopy.     

Contemporary Flux of Radionuclides to Contaminated Saltmarshes in the Esk Estuary,Cumbria

The Esk estuary is approximately 10 km from the marine outfall fromBritish Nuclear Fuels plc (BNFL) Sellafield Site and saltmarshes here havereceived significant quantities of radionuclides as reported in many studiessince 1975. These studies have concentrated on the inventory ofradionuclides in the estuary, but they have not addressed the continualreworking of radionuclides from these deposits. A detailed investigation ofboth the concentration of ¹³⁷Cs in the surface 10 cm and gammaair-kerma dose rates has been made where 120 determinations were made in agrid over 14600 m² of saltmarsh. The surface microtopographyis shown to be important for the continuing deposition of contaminatedsediments to the saltmarsh surface. This study has concentrated on thedevelopment and the possible application of sediment traps made fromAstroturf (an artificial grass). They were deployed at three sites whichwere representative of the major saltmarsh units in the estuary. The trapswere used to investigate the mobile sediments during a single tide, for aweek, and for a month. The Astroturf provided a reasonable analogue for thesaltmarsh surface and was arranged such that the radionuclide concentrationof the trapped sediment was measured directly by gamma spectrometry. Sediment deposition rates of between 30 and 240 g m^-2d^-1 were determined for the study sites, and these wereconsistent with earlier studies. Measurement of the radionuclideconcentration of the deposited sediment showed the addition of between 90and 750 Bq ³¹⁷Cs m^-2 d^-1 and 200and 1400 Bq ²⁴¹Am m^-2 d-1. At thedepositional sites over the saltmarsh this would represent an annualaddition of about 90 kBq m^-2 of ¹³⁷Cs and 180kBq m^-2 of ²⁴¹Am.     

Dry Deposition of Atmospheric Sulphur and Nitrogen in Russia and the Former USSR

Generally, dry deposition processes are very important for atmospheric chemistry of pollutants providing up to 30–80 % of the removal for certain compounds from the atmosphere. The model for calculating of dry deposition fluxes for a large territory seems unsophisticated in spite of the dependence on surface characteristics, pollutant properties and atmospheric conditions. The approach of combining monthly average concentrations measured at the Integrated Background Monitoring Network (IBMoN) and EMEP stations and linear dry deposition velocity was used to calculate total sulphur and nitrogen fluxes for the whole of the former Soviet Union (FSU) taking into account large-scale geographical variability in climate and lands. Most values of all SO₂ and SO₄ ^2? concentrations were below 2.9 and 3.1 mgS/m³, and NO₂ concentration were 1.5 mgN/m³ over European part and 0.6 mgN/m³ in Western Siberia. The long-term trends of oxidised sulphur and nitrogen compounds in the atmosphere were examined for 1982–1998 in certain FSU regions. Annual dry deposition of sulphur was estimated as 3.64 Mt S (in sulphate form) and 2.76 Mt S (in SO₂ form) for the whole area of FSU. Annual removal of NO₂ by dry deposition was calculated at 1.27 Mt N. These values constituted between 44 and 50% of total oxidised sulphur and nitrogen deposition.     

Concentrations of Nitrogen and Sulfur Species in Gas and Rainwater from Six Sites in Indonesia

Gas mixing ratios of SO₂, NO₂ and HNO₃ and nitrate and sulfate concentrations in rainwater have beenmeasured at six sites in Indonesia. The sites, Jakarta, Serang,Cilegon, Merak and Bogor, in Java, and Bukit Koto Tabang inSumatra, provide a range of pollution regimes in Indonesia.Jakarta and Bogor are heavily polluted sites in Java, whereasBukit Koto Tabang is a clean air station in a relativelyunpopulated area on the west coast of equatorial Sumatra. At thesesites rainwater was collected daily and gas samples weeklyduring 1996. The other three sites Serang, Cilegon and Merakrepresent smaller regional towns in west Java. At these sitesrainwater samples were collected weekly from June 1991 untilJune 1992.The results show that Jakarta has the highest volume-weightedmean sulfate concentrations in rainwater while the lowest weremeasured at Bukit Koto Tabang. Volume-weighted mean nitrateconcentration was about 24 μeq L^-1 at Jakarta and Bogor,significantly higher than the 0.8 μeq L^-1 measured atBukit Koto Tabang.Sulfur dioxide mixing ratios ranged from 4–7 ppbv in Jakarta toan average of 1.3 ppbv at Bukit Koto Tabang. Nitrogen dioxidemixing ratio was highest in Jakarta averaging 28 ppbv comparedwith the background mixing ratio of 1.2 ppbv at Bukit KotoTabang. Using dry deposition velocities estimated during aseparate study in the similar conditions of Malaysia enabled drydeposition estimates of SO₂, HNO₃ and NO₂.Results of estimated total acidic S and N deposition (wet anddry) were greater than 250 meq m^-2 yr^-1 at the Jakartaand Bogor sites compared with about 23 meq m^-2 yr^-1 atBukit Koto Tabang. At Jakarta and Bogor dry deposition accountedfor more than 50% of the total deposition estimates compared with about 20% at Bukit Koto Tabang. Such deposition rates arehigh when compared to critical loads estimated for Indonesia bythe RAINS-Asia model. In this model, critical loads in western Java and equatorial western Sumatra fall into one of twoclasses: 50–100 and 20–50 meq m^-2 yr^-1. Thus acidic deposition flux at Jakarta and Bogor wasfound to be above the predicted critical loads even for the moreacid insensitive soils.     

Estimation of Dry Deposition by Using a Filter Pack Method at Chunchon, Korea

Atmospheric gases and particulates were collected using four-stage filter-pack in Chunchon from January through December in 1999. Particulate SO₄ ^2? and NO₃ ^?, and gaseous HNO₃, SO₂ and NH₃ were analyzed. Annual average concentration of SO₄ ^2?(S), NO₃ ^?(S), HNO₃ (g), SO₂(g) and NH₃(g) were 5.75µg/m³, 4.98µg/m³, 0.33ppb, 1.52ppb and 7.25ppb, respectively. Annual dry deposition fluxes were estimated using the measured concentration and dry deposition velocity published by other research group. Annual dry deposition of S was 287kg · (km)^?2·y^?1, which accounted for about 30% of total S deposition. For N deposition, dry deposition is predominant; about 70% of total N deposition was through dry process mostly as forms of NH₃ and HNO₃.     

Distribution and migration of radiocesium in sloping landscapes three years after the Fukushima-1 nuclear accident

The results of the study are presented on the distribution and migration of radiocesium in mountainous (580–620 m a.s.l.) landscapes in the northeast of Honshu Island (Tohoku Region, Miyagi Prefecture) subjected to radioactive contamination after the nuclear accident at Fukushima-1 NPP. In July 2014, the average contamination density with radiocesium (¹³⁴Сs and ¹³⁷Сs) over the territory (150 km to the northwest from NPP) was equal to 16 kBq/m². This contamination is estimated at the acceptable level according to both Japanese and Russian standards and legislation. Three years after the accident, radiocesium is found to be unevenly distributed by the biogeocenosis components, i.e. 45% in litter, 40% in plants, 10% in soil, and 5% in roots. As for the distribution of total radiocesium (Cs tot = ¹³⁴Сs + ¹³⁷Сs) by the profile of volcanic podzolic-ocherous soil (Dystric Aluandic Andosols), its maximal content (about 80%) was found in the surface layer (0–2.5 cm), with the specific activity ranging from 250 to 10070 Bq/kg and sharply decreasing with the depth. Radiocesium amount in the soils of forest ecosystems was on average by 20% higher than in meadow ecosystems. Accumulation of radionuclides in soils of lower and middle parts of a slope with an insignificant vertical migration was found to be the most general regularity. The air dose rate did not exceed the maximal permissible level, and the snow cover acted as an absorbing and scattering screen.     

Long-term Continuous Measurements of SO2 Dry Deposition over the Speulder Forest

In 1990 a project to develop a dry deposition monitoring method of SO₂, NH₃ and NO₂ to Speulder forest in the Netherlands began. Detailed annual deposition fluxes for these gases were measured throughout November 1992 to December 1995. This paper describes the measurement set-up and the analysis of the deposition parameters for SO₂. The dry deposition velocity was usually smaller than the maximum V_d, showing a resistance to surface uptake, except for periods when the canopy is wet and surface resistance is negligible. Several methods were tested to estimate annual average fluxes from the gradient measurements. Annual fluxes were estimated by selecting the data for periods fulfilling gradient theory and extending the data by using an inferential method for the other periods. The surface resistance parametrisation used in the inferential method was tested using the selected data and was found to yield systematic larger fluxes of the order of 20%. Annual fluxes were 465 mol ha^-1 a^-1 in 1992/1993, 460 mol ha^-1 a^-1 in 1994 and 330 mol ha^-1 a^-1 in 1995. The uncertainty in the annual flux was estimated to be 25%. The annual average dry deposition velocity was 1.5 cm s^-1. No large differences were found in deposition parameters between each of the three years.     

A Single Law to Describe Atmospheric Nitrogen Bulk Deposition versus Rainfall Amount: Inputs at the Seine River Watershed Scale

Atmospheric nitrogen species (NH₄-N and (NO₃+NO₂)-N) were determined in weekly samples of atmospheric bulk deposition (dry plus wet), collected in France at seven sites over the course of a year. Rural, semi-rural and industrialised-urban sites were chosen in the Seine river watershed from the Seine estuary to upstream from Paris. Mean NH₄-N concentrations varied from 0.7 to 1.7 mg L^-1. Mean (NO₃+NO₂)-N concentrations were approximately 0.5 mg L^-1 for all sites except Paris (0.7 mg L^-1), which has a local impact on the fallout contamination from urban emissions. The relation between concentration and rainfall amount obeys a power law, in the form of y = ax ^b. When the nitrogen sources are very local, this relationship turns into a dilution law. Annual atmospheric nitrogen deposition (NH₄-N+(NO₃+NO₂)-N) was calculated and varied from 7.8 kg ha^-1 yr^-1 in the neighbourhood of a rural town to 17.3 kg ha^-1 yr^-1 in a very industrialised harbour. 58% of the atmospheric nitrogen deposition occurred during ‘spring + summer’ period. The total nitrogen atmospheric input to the Seine estuary, via direct deposition + indirect input via the watershed, was estimated to about 5% of the total nitrogen load within the Seine river basin.     

In situ radiometric mapping of soil erosion and field-moist bulk density on cultivated fields

Abstract. Recent developments in in situγ ray spectrometry offer a new approach to measuring the activity of radionuclides such as ¹³⁷Cs and ⁴⁰K in soils, and thus estimating erosion or deposition rates and field moist bulk density (ρ_m). Such estimates would be rapid and involve minimal site disturbance, especially important where archaeological remains are present. This paper presents the results of a pilot investigation of an eroded field in Scotland in which a portable hyper pure germanium (HPGe) detector was used to measure γ ray spectra in situ. The gamma (γ) photon flux observed at the soil surface is a function of the ¹³⁷Cs inventory, its depth distribution characteristics and ρ_m. A coefficient, Q_Cs, derived from the forward scattering of ¹³⁷Cs γ ray photons within the soil profile relative to the ¹³⁷Cs full energy peak (662 keV), was used to correct the in situ calibration for changes in the ¹³⁷Cs vertical distribution in the ploughed field, a function of tillage, soil accumulation and ρ_m. Based on only 8 measurements, the agreement between in situγ ray spectrometry and soil sample measurements of ¹³⁷Cs inventories improved from a non significant r²=0.05 to a significant r²=0.62 (P<0.05). Erosion and deposition rates calculated from the corrected in situ¹³⁷Cs measurements had a similarly good agreement with those calculated from soil cores. Mean soil bulk density was also calculated using a separate coefficient, Q_K, derived from the forward scattering γ photons from ⁴⁰K within the soil relative to the ⁴⁰K full energy peak (1460 keV). Again there was good agreement with soil core measurements (r²=0.64; P<0.05). The precision of the in situ¹³⁷Cs measurement was limited by the precision with which Q_Cs can be estimated, a function of the low ¹³⁷Cs deposition levels associated with the weapons testing fallout and relatively low detector efficiency (35%). In contrast, the precision of the in situ ρ_m determination was only limited by the spatial variability associated with soil sampling.     

Forms and rates of release of 137Cs in two peat soils

Cation exchange resin saturated with H⁺ and Ca²⁺ was used to extract ¹³⁷Cs from peat soil at two sites in Britain affected by ^l37Cs deposition following the Chernobyl accident. The technique identified three classes of ¹³⁷Cs, similar to those observed for K⁺ in soils: ‘Fast’, ‘Intermediate’ and ‘Slow’. These classes are probably related to the selectivity for ¹³⁷Cs of the cation exchange sites on the organic matter and the clay minerals, and to the structure of the soil. With one exception, most ¹³⁷Cs was in the ‘Slow’ form and was only very slowly released to the resins, if at all. However, there was enough ^l37Cs in the ‘Fast’ and ‘Intermediate’ forms to contaminate pasture and thus grazing animals for some years. Based on the resin technique, it is estimated that contamination will persist for several decades in uplands contaminated at these activity concentrations.     

The Efficiency of Moldboard Plowing upon Deactivation and Rehabilitation of Radioactively Contaminated Pastures in the North of Japan

The nuclear disaster at the Fukushima-1 nuclear power plant resulted in the widespread contamination of agrocenoses with radiocesium (¹³⁴Cs and ¹³⁷Cs) on the Honshu Island. Our study was performed on four agricultural fields located on gentle slopes of southern aspect 150 km to the northwest from the nuclear power plant. Three plots were tilled in different periods (in 2012–2013), and one plot remained untilled. The density of soil contamination and the specific activity of radiocesium in plants (June 2014) on tilled plots appeared to be permissible. Thus, the density of soil contamination varied within the range of 1.3–6.5 kBq/m², and the specific radioactivity of plants did not exceed 100 Bq/kg in plants. Such areas may be used as pastures without restrictions. At the same time, an increased density of the soil contamination (13–32 kBq/m²) and the concentration of radiocesium in plants (up to 138 Bq/kg) were detected in some areas not subjected to reclamation works. Such fallow lands are suitable as pastures only for feeding cattle for meat and for milk with their obligatory subsequent processing. On all the plots, the concentration of radiocesium in soils decreased down the soil profile. In general, radiocesium was accumulated on the middle and lower parts of slopes, which is associated with the development of water erosion and initial distribution of radiocesium during the snowmelt season. The air dose rate on the studied plots did not exceed the permissible safety level (0.2 μSv/h) and varied within the range 0.05–0.10 μSv/h. The maximum level of γ-radiation was determined on the fallow (untilled) plot. On tilled plots, γ-radiation was 30–50% lower. Therefore, soil moldboard plowin tillage to the depth of 20 cm with or without shallow cultivation is an efficient measure to reclaim agricultural lands with the initially low level of radiocesium contamination (up to 32 kBq/m²).     

Land use in agricultural landscapes with chernozems contaminated after Chernobyl accident: Can we be confident in radioecological safety of plant foodstuff?

Agricultural land use in the area of the post-Chernobyl Plavsk radioactive hotspot (Tula region, Central Russia) has raised a problem of radioecological safety of obtained plant foodstuff. Verification of ¹³⁷Cs activities and inventories in components of “soil-plant” systems of the territory has been conducted in 2014–2017 in 10 agrosystems and 2 semi-natural meadows. It was revealed that density of ¹³⁷Cs contamination of arable chernozems and alluvial calcareous soils nowadays varies in a range 140–220 kBq/m² and exceeds radiation safety standard by ˜ 3.5–6 times. Deep plowing of the arable soils up to 30-cm in 1986–1987 resulted in decreasing of ¹³⁷Cs inventories in rooting zone by ≈ 70% for crops cultivated with shallow disk plowing (wheat, barley), and by ≈ 35% for crops cultivated with middle plowing (buckwheat, amaranth, white mustard). The investigated plants and their compartments can be grouped on the basis of transfer factor values as follows: maize (stems and leaves) > amaranth > bromegrass > vegetation of dry meadow, galega, sunflower (seeds), vegetation of wet meadow > maize (grain), soybean (pods), barley (grain), buckwheat (grain), potatoes (tubers) > white mustard (seeds), wheat (grain). It is noticeable that generative plant compartments are characterized by less ¹³⁷Cs activities in comparison with stems and leaves; and that ¹³⁷Cs root uptake is not coincide with total flux of mineral nutrients in “soil-plant” systems. In sum, ¹³⁷Cs soil-to-plant transfer in the area of the Plavsk radioactive hotspot is characterized by considerable discrimination, so ¹³⁷Cs activities in plants are completely in accordance with national standards.     

Acid deposition to nature areas in the Netherlands: Part I. Methods and results

In this paper estimates of dry and wet deposition of acidifying substances in the Netherlands are presented. The deposition was estimated from measured concentrations in the atmosphere and in precipitation or if these were not available, from modelled concentrations. The method was applied for the Netherlands on a 5×5 km scale. The most important components are sulphur oxides and ammonia and their reaction products. It was estimated that the annual average deposition of SO _x in the Netherlands decreased from 1570 to 670 mol ha^?1 a^?1 between 1980 and 1989. In 1989, the annual average NO _y deposition was estimated to be 1220 mol ha^?1 a^?1 in 1980 and 1160 mol ha^?1 a^?1 in 1989. The annual average NH _x deposition in the Netherlands was estimated to be 2330 and 2190 mol ha^?1 a^?1 in 1980 and 1989 respectively. HCI deposition was about 100 mol ha^?1 a^?1 in all years. Dry deposition contributes most to the total deposition for each component. The spatial distribution of the total deposition shows a gradient over the Netherlands with highest values in the South and lowest in the North of the country. Meteorological conditions are also of influence on the deposition fluxes for all components. During 1988 and 1989 meteorological conditions favoured low deposition. The estimated uncertainty in the average fluxes of SO _x , NO _y , and NH _x for the Netherlands is 15, 25, and 30% respectively. The wet deposition fluxes can be estimated more accurately than the dry deposition.     

Measurements of ozone deposition to a potato canopy

Potatoes are an important staple crop, grown in many parts of the world. Although ozone deposition to many vegetation types has been measured in the field, no data have been reported for potatoes. Such measurements, including the latent-heat flux, were made over a fully grown potato field in central Scotland during the summer of 2006, covering a 4-week period just after rainfall and then dry, sunny weather. The magnitude of the flux was typical of many canopies showing the expected diurnal cycles. Although the bulk-canopy stomatal conductance declined as the field dried out (～300 mmol-O₃ m^?2 s^?1 to ～70 mmol-O₃ m^?2 s^?1), the total ozone flux did not follow the same trend, indicating that non-stomatal deposition was significant. Over a dry surface non-stomatal resistance (R_ns) was 270–450 s m^?1, while over a wet surface R_ns was ～50% smaller and both decreased with increasing surface temperature and friction velocity. From the variation with relative humidity (RH) it is suggested that three processes occur on leaf surfaces: on a very dry surface ozone is removed by thermal decomposition, possibly enhanced by photolytic reactions in the daytime and so R_ns decreases as temperature increases; at 50–70% RH a thin film of liquid blocks the “dry” process and resistance increases; above 60–70% RH sufficient surface water is present for aqueous reactions to remove ozone and resistance decreases.     

利用137Cs示踪技术评价东北黑土侵蚀和沉积过程

Soil and water losses through erosion have been serious in the black soil region of Northeast China. Therefore, a sloping cultivated land in Songnen Plain was selected as a case study to： 1） determine the ^137Cs reference inventory in the study area; 2） calculate erosion and deposition rates of black soil on different slope locations; 3） conduct a sensitivity analysis of some model parameters; and 4） compare overall outputs using four different models. Three transects were set in the field with five slope locations for each transect, including summit, shoulder-slope, back-slope, foot-slope, and toe-slope. Field measurements and model simulation were used to estimate a bomb-derived ^137Cs reference inventory in the study area. Soil erosion and deposition rates were estimated using four ^137Cs models and percentage of ^137Cs loss/gain. The ^137Cs reference value in the study area was 2 232.8 Bq m^-2 with ^137Cs showing a clear topographic pattern, decreasing from the summit to shoulder-slope, then increasing again at the foot-slope and reaching a maximum at the toe-slope, Predicted soil redistribution rates for different slope locations varied. Among models, the Yang Model （YANG-M） overestimated erosion loss but underestimated deposition. However, the standard mass balance model （MBM1） gave predictions similar to a mass balance model incorporating soil movement by tillage （MBM2）. Sensitivity analysis of the proportion factor and distribution pattern of ^137Cs in the surface layer demonstrated the impact of ^137Cs enrichment on calculation of the soil erosion rate. Factors influencing the redistribution of fallout ^137Cs in landscape should be fully considered as calculating soil redistribution rate using ^137Cs technique.     

Relationship of ambient atmospheric hydrocarbon (C12–C32) concentrations to deposition

Anthropogenic and biogenic high molecular weight (C₁₂–C₃₂) hydrocarbons (HC) were deposited from the atmosphere in association with both wet and dry deposition. Wet deposition generally removes HC at a faster rate (22 to 670 μg m^?2 day^?1) than dry deposition (4 to 189 μg m^?2 day^?1). However, due to longer periods during which dry deposition occurred, the removal of atmospheric HC by wet and dry deposition is almost equal during this sampling period. Atmospheric HC concentrations ranged from 0.8 to 4.1 μg m^?3 and show no simple relationship to wet or dry deposition rates. Large variabilities in deposition rates for individual events were found, but long-term average deposition was relatively constant.