基于土壤~(137)Cs监测的土壤侵蚀与有机质流失——以密云水库为例

本文运用137Cs核素示踪技术,研究北京重要的水源供应地密云水库周边地区及白河上游地区土壤侵蚀状况与有机质流失状况及其相互之间的量变关系。试验结果表明:0～20cm土层中山坡上137Cs含量低于坡中、坡下,但若山顶具有缓坡或山角下具有陡坡则137Cs含量变化规律相反。根据水利部标准与土壤137Cs监测结果,密云水库周边大部分地区基本属于轻度侵蚀和中度侵蚀,部分地区侵蚀情况严重,达到了剧烈侵蚀的程度。不同土地利用方式对土壤有机质分布有很大影响,有机质含量分布为灌丛>林地>果园>农田;上游地区有机质含量高于水库周边地区土壤,表明人为活动加剧了土壤侵蚀和有机质的流失。对于景观单一,地域较小的采样区进行三次曲线数学模拟,其相关系数高达0.9左右,表明在监测土壤137Cs、210Pb含量变化的同时,可以利用小区域数学模型直接预报预测土壤有机质含量的变化。     

植物对~(137)Cs污染土壤的修复

选用了南瓜、油菜、虎尾草、红梗叶甜菜、东升叶甜菜和红甜菜等几种植物,通过盆栽模拟,研究不同活度137Cs污染的广东大亚湾水稻土、浙江秦山水稻土和北京褐土的生物修复作用。结果表明,供试植物在3种土壤上均对137Cs有较强的吸收能力,并随137Cs施入量的增加而增加,两者呈显著正相关r2=0.9989。在污染水平相同的情况下,试验发现,虎尾草、油菜和南瓜所吸收137Cs的比活度随土壤的pH值降低而增加。6种植物的生物修复能力差异较大,综合评价结果为,对137Cs污染土壤修复能力的顺序是:虎尾草>油菜>红梗叶甜菜>南瓜>红甜菜>东升叶甜菜。     

核素示踪技术在土壤侵蚀研究中的应用进展

介绍了单核素 (137Cs、2 10 Pb和7Be)、复合核素 (7Be、2 10 Pb、2 2 6 Ra和137Cs)及稳定性稀土元素 (REE)示踪技术在土壤侵蚀速率、泥沙沉积速率、侵蚀产沙时空分布和侵蚀类型转变等研究中的应用现状 ,并对各方法做了简要评价。     

~(137)Cs在土壤中的污染行为与钾盐的防治效果

本研究结果表明 ,在污染水平相同的情况下 ,不同土壤对春小麦吸收137Cs有很大影响 ,植株中137Cs的比活度相差几十倍。在同一种土壤、不同污染水平下 ,春小麦对137Cs的吸收与土壤中137Cs的污染水平呈正相关。在137Cs污染的土壤上施用钾盐可以降低春小麦植株对137Cs的吸收。防治效果与钾盐施用量有关 ,本试验结果为土壤阳离子代换量 1 / 3 0的量施用效果最好 ,使植株中的137Cs比活度降低 84 74%～88 89% ,与不施钾盐的对照组的差异十分显著     

~(137)Cs不同污染水平在大亚湾、秦山、北京土壤植物系统的转移

采用我国大亚湾、秦山和北京土壤 ,模拟核裂变产物137Cs在 0Bq kg土、3 3×1 0 4 Bq kg土、3 3× 1 0 5Bq kg土、3 3× 1 0 6 Bq kg土污染水平时 ,研究土壤 -小麦系统的污染影响与137Cs核素的转移规律。结果表明 :在本试验条件下小麦生长发育处于正常状态 ,未发现对小麦有不良影响 ;小麦分别在 3个污染水平下从试验用的 3种土壤中吸收137Cs的趋势是一致的 ;小麦植株中137Cs的比活度随137Cs施入量相应以数量级增加 ,两者间呈十分显著的正相关 ;137Cs在土壤 -小麦系统中的转移系数随土壤的性质不同而变化 ,在同一污染水平下转移系数在n× 1 0 - 2 ～n× 1 0 0 范围变化 ;在同一种土壤中 ,随土壤污染水平的提高 ,转移系数亦有所提高 ,但变化范围不大 ,对北京土转移系数为 2 2× 1 0 - 2 ～ 5 4× 1 0 - 2 ,大亚湾土转移系数为 1 0 4～ 2 0 9,均在同一数量级内变化 ;对秦山土转移系数为 0 51～ 1 2 1。     

用137Cs示踪法研究密云水库周边土壤侵蚀与氮磷流失

运用137Cs核素示踪技术,研究密云水库周边地区及白河上游地区土壤侵蚀与氮、磷流失状况及其相互之间的量变关系.研究结果表明:从土壤表层(0～20 cm)137Cs分布规律基本符合地形地貌的变化规律,山坡上部的137Cs含量低于山坡中部与坡下部,但是如果山顶具有缓坡或山角下具有陡坡,则137Cs含量变化规律相反.根据土壤137Cs监测数据结果判定该地区基本属于轻度侵蚀和中度侵蚀,部分地区侵蚀情况达到剧烈程度.不同景观与土地利用方式对土壤氮、磷分布有巨大影响:有机质、全氮、水解氮含量均是以灌丛土壤最高,林地次之,与流域内137Cs分布规律相符合;而农田中全磷、速效磷含量最高.不同区域土壤养分含量不同:水库上游地区土壤氮素、磷素含量均低于水库周边地区.证明不合理的人为活动严重的增强了土壤侵蚀程度与养分流失量.回归模拟了土壤中137Cs、(210Pb)与全氮、全磷、水解氮、速效磷含量之间的数学模型.这些模型在区域较小、景观单一的范围内可以定量分析、预报预测各采样区的全磷和有效态氮、磷含量的变化趋势.简化了监测与分析测试程序.扩大了核素示踪技术的应用范围.     

秦山核电站周围农业生态环境放射性本底调查

本研究调查了秦山核电站站址周围50km半径范围内土壤、水和农作物的总α、总β放射性水平,土壤中天然放射性核素含量,以及γ外照射积累剂量。结果表明:土壤中总α、总β值分别为0.54—1.48×10~(-8)Ci/kg和1.90—2.96×10~(-8) Ci/kg,低于全国一般地区平均水平,且0—100cm土层变化不大。土壤中~238U、~226Ra、~232Th、~40k、~137Cs的放射性活性分别为0.67—5.00×10~(-9)、4.49—11.4×10~(-10)、0.88—1.69×10~(-9)、0.39—2.09×10~(-8)和0.89—4.32×10~(-10)Ci/kg。河水、湖水以及核电站废水排放口处海水总β值分别为1.32—8.62、3.6和2.55×10~(-12)Ci/L。大米和油菜叶中的总β值分别为2.53和3.0×10~(-9)Ci/kg。室内外月平均γ照射量各为10.6—14.7和9.16—13.7mR。     

辽东湾沿岸土壤中~(137)Cs背景值及分布特征研究

在辽东湾沿岸区域采集了20个土壤表层样和7个非耕作土壤剖面样(其中一个为标准剖面),通过对采集的土壤样品中的137 Cs进行测量与分析,确定该区域土壤中137 Cs的背景值,并探讨了土壤中137 Cs的分布特征。结果表明,研究区137 Cs的背景值为(1 704±40)Bq/m2;表层土壤中137 Cs的比活度范围为0.84～19.90Bq/kg,不同土地利用类型表层土壤中的137 Cs比活度有明显差异,比活度高低依次为:草地>盐碱地>耕地;非耕作土壤剖面中137 Cs的总量范围为65～1 535Bq/m2,大部分土壤剖面中137 Cs呈指数递减分布,且剖面中的137 Cs发生不同程度的流失,而受到沉积扰动作用的剖面中137 Cs分布无规律。通过探讨辽东湾沿岸区域土壤中137 Cs的背景值及137 Cs的分布特征,为利用137 Cs示踪技术定量研究该区域物质输移和辽东湾沉积物来源提供依据。     

抗辐射球菌对结球甘蓝吸收~(134)Cs的影响

在土壤中引入134Cs后接种抗辐射球菌(Deinococcus radiodurans),研究其对放射性铯在土壤中化学形态的影响。在抗辐射球菌存在的情况下,利用结球甘蓝(Brassica oleracea)吸收134Cs,初步研究了134Cs化学形态与结球甘蓝对其吸收能力的关系。结果表明:134Cs在土壤中主要以残留态形式存在,且接种抗辐射球菌的土壤残留态134Cs比在无菌土壤中的比例高28.64%~38.17%。结球甘蓝对134Cs的吸收量约为12100Bq/g,但在接种抗辐射球菌后,结球甘蓝对134Cs的吸收量约为8500Bq/g,比未接种细菌时的吸收量下降了约29%。抗辐射球菌可以改变134Cs在土壤中的化学形态,从而降低植物对134Cs的吸收。     

用 137Cs示踪法研究密云水库周边土壤侵蚀与氮磷流失

运用 ¹³⁷Cs核素示踪技术，研究密云水库周边地区及白河上游地区土壤侵蚀与氮、磷流失状况及其相互之间的量变关系。研究结果表明：从土壤表层(0～20 cm) ¹³⁷Cs分布规律基本符合地形地貌的变化规律，山坡上部的 ¹³⁷Cs含量低于山坡中部与坡下部，但是如果山顶具有缓坡或山角下具有陡坡，则 ¹³⁷Cs含量变化规律相反。根据土壤 ¹³⁷Cs监测数据结果判定该地区基本属于轻度侵蚀和中度侵蚀，部分地区侵蚀情况达到剧烈程度。不同景观与土地利用方式对土壤氮、磷分布有巨大影响：有机质、全氮、水解氮含量均是以灌丛土壤最高，林地次之，与流域内 ¹³⁷Cs分布规律相符合；而农田中全磷、速效磷含量最高。不同区域土壤养分含量不同：水库上游地区土壤氮素、磷素含量均低于水库周边地区。证明不合理的人为活动严重的增强了土壤侵蚀程度与养分流失量。回归模拟了土壤中 ¹³⁷Cs、( ²¹⁰Pb)与全氮、全磷、水解氮、速效磷含量之间的数学模型。这些模型在区域较小、景观单一的范围内可以定量分析、预报预测各采样区的全磷和有效态氮、磷含量的变化趋势。简化了监测与分析测试程序。扩大了核素示踪技术的应用范围。     

Kinetics of 110mAg, 60Co, 137Cs and 54Mn Bioaccumulation from Water and Depuration by the Crustacean Daphnia Magna

As part of a research program on the transfer withinfreshwater ecosystems of the radionuclides present inthe weakly radioactive liquid effluents from nuclearpower stations, this article presents an assessment ofthe dynamics of zooplankton contamination from water.The experiments were carried out on young pre-adultdaphnids, placed at a density of 250 individualsL^-1, in 0.45 m filtered river water. Inorder to maintain the radionuclide contamination at ahigh level and to limit alterations in the chemicalcharacteristics of the medium, the water was reneweddaily. The dynamics of contamination were described bya one (¹³⁷Cs) or a two compartmental model(^110mAg, ⁶⁰Co and ⁵⁴Mn), taking intoaccount the fluctuations of the radionuclideconcentration in the water, as well as the growth rateof the daphnids. The contamination levels weredescribed by the steady state value of theconcentration factor, which was 2870 mL g^-1 wetweight, 320 mL g^-1 wet weight, 265 mL g^-1wet weight and 30 mL g^-1 wet weight, for^110mAg, ⁵⁴Mn, ⁶⁰Co and ¹³⁷Cs,respectively. During the depuration phase,radioactivity decrease in daphnids was a very fastphenomenon indicating that radionuclide adsorption tothe surface was the major process involved in thecontamination of daphnids. The two correspondinghalf-lives of the depuration kinetics were 10 min and7 d, 20 min and 1 d and 3 hr and 1.5 d for⁶⁰Co, ^110mAg and ⁵⁴Mn, respectively.The loss of ¹³⁷Cs was characterised by a singlehalf-life of 0.3 d.     

农耕地土壤137Cs与210Pbex深度分布过程对比研究

探讨了137Cs与210Pb_ex在农耕地土壤深度分布过程的差异。基于137Cs与210Pb_ex的不同沉降过程,考虑到核素由犁耕层向犁底层的扩散,对农耕地土壤137Cs、210Pb_ex的深度分布过程进行了理论推导,并以杨凌符家庄麦田剖面的实测数据予以验证,同时讨论了实测符家庄麦田剖面137Cs、210Pb_ex深度分布的规律特征及其原因,以此阐明了137Cs与210Pb_ex在农耕地土壤深度分布过程的差异。137Cs源于大气核试爆,没有持续沉降补充,犁耕层和犁底层土壤137Cs深度分布一直处于随时间变化的非稳定态;而210Pb_ex是天然核素,存在大气沉降的持续补充,犁耕层和犁底层土壤210Pb_ex深度分布最终呈稳定态。农耕地土壤137Cs、210Pb_ex深度分布的实测值曲线与理论值曲线的差异,尤其210Pb_ex,可能与耕作深度的变化历史或土地利用(覆被)变化有关。     

Method of studying the degradation of soil macroaggregates based on the self-absorption of 137Cs β radiation

A method was proposed for studying the degradation of soil aggregates in time from the absorption of ¹³⁷Cs β-radiation by a soil sample. The method is based on the difference in the recorded β radiation intensities depending on the distribution of ¹³⁷Cs between the surface of the aggregates and the nonaggregated soil material. At the localization of the radionuclide on the surface of the soil aggregates, the counting rate will significantly exceed that for the samples containing a similar amount of the radionuclide uniformly distributed throughout the soil volume. This effect is due to the insignificant range of the mild β radiation in the soil (less than 1 mm depending on the radiation energy). Relatively clear calibration graphs under the selected conditions of the radiometric measurements were obtained for the aggregates whose sizes were in the range of 3–10 mm. Under natural conditions, the 7- to 10-mm aggregates of a dark gray clay loamy soil under a forest belt decomposed by 50–65% at a depth of 10 cm and by 23–32% at a depth of 30 cm. The more intense degradation of the soil aggregates of the same size was observed under the conditions of a pot experiment.     

Sediment Records of Fallout Radionuclides and their Application to Studies of Sediment-Water Interactions

The fallout radionuclides 210Pb and 137Cs are widely used to date environmental records contained in lake sediments. Since the radionuclide records are themselves the outcome of the transformation of atmospheric fallout by mediating transport processes from the catchment, through the water column and post-depositional migration via pore waters, reliable models of these processes are crucial to accurate dating. The large quantities of data on 210Pb and 137Cs in lake sediments accumulated through their widespread dating applications may be used to study transport models. Their advantages as tracers of transport processes include widespread dispersal through the environment, relatively simple and well known input functions, and ease of measurement. One of the principle factors controlling the transport of any species through the water column is its distribution between aqueous and particulate phases. The relatively solubility of 137Cs in the water column is demonstrated by the reduced 137Cs/210Pb inventory ratios in sediments compared to values expected from direct fallout. Using sediment records from a wide range of Cumbrian lakes, calculations based on simple models indicate that the particulate fraction of weapons fallout 137Cs in the water column ranged from 5-22%, and was proportional to the square root of the sedimentation rate (determined by 210Pb). The KD value for weapons 137Cs in the water column is estimated to be in the range 1-2×105 L kg-1. This is comparable with KD values for Chernobyl 137Cs in these lakes (Smith et al. in press) obtained from direct measurements in the water column.     

Concentrations of Radionuclides (<Superscript>226</Superscript>Ra, <Superscript>232</Superscript>Th, <Superscript>40</Superscript>K,and <Superscript>137</Superscript>Cs) in Chernozems of Volgograd Oblast Sampled in Different Years

Data on the concentrations of natural (²²⁶Ra, ²³²Th and ⁴⁰K) and artificial (¹³⁷Cs) radionuclides and on the physicochemical properties of chernozems sampled in different years are presented. In 1952, upon the creation of the Penza-Kamensk state shelterbelt, three deep (up to 3 m) soil pits were examined within the former arable field under two-year-old plantations of ash and maple along the transect crossing the territory of the Beloprudskaya Experimental Station of the USSR Academy of Sciences in Volgograd oblast. The samples from these pits were included into the collection of dated soil samples of the Dokuchaev Central Soil Science Museum. Five pits were examined along the same transect in 2009: three pits under shelterbelts (analogues of the pits studied in 1952) and two pits on arable fields between the shelterbelts. In the past 57 years, certain changes took place in the soil structure, bulk density, and the content and composition of humus. The salt profile of soils changed significantly under the forests. The comparison of distribution patterns of natural soil radionuclides in 1952 and 2009 demonstrated their higher contents at the depth of 10–20 cm in 2009 (except for the western shelterbelt). Background concentrations of natural radionuclides in parent materials and relationships between their distributions and the salt profiles of soils have been determined; they are most clearly observed is the soils under shelterbelts. Insignificant contamination with ¹³⁷Cs (up to 34 Bq/kg) has been found in the samples of 2009 from the upper (0–20 cm) horizon. The activity of ¹³⁷Cs regularly decreases from the east to the west; the highest concentrations of this radionuclide are found in the topmost 10 cm. This allows us to suppose that ¹³⁷Cs was brought with aerial dust by eastern winds, and the shelterbelts served as barriers to the wind flow.     

Cesium-137 Root Uptake by Oat and Lettuce Test Crops from Radioactively Contaminated Chernozem under Model Experiment Conditions

The features of cesium-137 (¹³⁷Cs) root uptake by spring oat (Avena sativa L.) and lettuce (Lactuca sativa L.) plants have been studied in a model experiment with simulation of radionuclide fallout into undisturbed monoliths of arable chernozems from the Plavsk radioactive spot. An integrated approach using digital autoradiography and γ-spectrometry methods has revealed a uniform pattern of vertical and lateral ¹³⁷Cs distribution in the soil profile and low bioavailability of the radionuclide or root uptake by plants. Certain biological features of the test crops with respect to root uptake of ¹³⁷Cs have been demonstrated: limited translocation of the element into shoots via its relative accumulation in roots for oats and limitation of general root uptake of ¹³⁷Cs into plants, given its uniform distribution between roots and shoots for lettuce.     

江苏省句容地区137Cs背景值研究

土壤侵蚀问题是当今世界面临主要环境问题之一,137Cs示踪作为一种应用于土壤侵蚀研究比较成熟的方法,其背景值的确定是前提.本研究通过两个疑似背景值点样品的采集,探讨了耕地土壤剖面137Cs活度的分布特征、增加样品的采集数量,并且与其他研究者的研究进行对比,确定江苏省句容地区137Cs的背景值为1820.36 Bq/m2.此活度与江苏省其他地区的背景值接近,可以用该背景值进行土壤侵蚀速率以及农业非点源污染负荷估算.     

Einfluß des Jahresniederschlags und der Bodenart auf die 137Cs-Tiefenverteilung in Böden Südchiles

The influence of mean annual rainfall and soil texture on the ¹³⁷Cs vertical distribution in soils from southern Chile The influence of mean annual rainfall and soil texture on the vertical distribution of ¹³⁷Cs from global fallout was studied in undisturbed volcanic ash soils from southern Chile. The areal concentration and translocation depth increase with the mean annual precipitation. In spite of the high rainfall at the sampled area (970 - 2500 mm a^?1), the highest ¹³⁷Cs contamination was found in the upper 10 cm layer. The vertical migration is reduced by the high adsorption capacity of these volcanic ash soils, but on the other side increased in soils with high large-pore volumen. The translocation depth reaches only up to 26 cm in the clay soils, 35 cm in the silty soils and 70 cm in the sandy soil.     

Relationships Between Radionuclide Content and Textural Properties in Irish Sea Intertidal Sediments

Intertidal sediments from a range of depositional environments in the eastern Irish Sea have been analysed with regard to their radionuclide content, particle size distribution and magnetic properties. Concentrations of²⁴¹Am and¹³⁷Cs are highly influenced by the abundance of sediment finer than 32μm in fine-grained sedimentary environments, whilst radionuclide activity in coarser sediments is less dependent on particle size. Investigation of the magnetic properties of these sediments highlights a similar association between this size fraction and magnetic remanence, the latter being shown to offer strong potential as a grain size proxy in monitoring¹³⁷Cs concentrations in fine-grained sediments. Analysis of particle size fractions indicates the extent to which¹³⁷Cs may be enriched in the clay size fractions of both tine and coarse sediments.