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1.
~(137)Cs示踪法土壤侵蚀量估算的本底值问题 总被引：1，自引：0，他引：1
137Cs示踪法因能快速、相对简便地估算土壤侵蚀量而在土壤侵蚀定量研究中得到广泛应用。本底值获取是137Cs示踪法的关键和基础。在具有空间异质性多因素综合作用下,本底值呈现高度的空间异质性。针对本底值空间变异性,从气候气象要素、地形、土壤属性、土地利用/覆被四个方面阐明各因素与本底值空间变异的作用机理。分析了当前137Cs示踪法应用中在本底值获取时参考点存在性及选点的准确性、单个或几个本底值对研究区本底值的代表性和参考点采样设计。提出划分侵蚀测定单元、建立多本底值体系和进行地形校正解决当前137Cs示踪法中本底值存在问题的对策。侵蚀测定计算单元的划分原则和方法、根据已有参考点的137Cs本底值推算各单元137Cs本底值的技术方法、定量化研究各因素对137Cs的作用是今后需要深入的工作。 相似文献
2.
Wind-driven soil erosion results in land degradation, desertification, atmospheric dust, and sandstorms. The Hunshandake Sandy Land, an important part of the Two Barriers and Three Belts project, plays important roles in preventing desert and sandy land expansion and in maintaining local sustainability. Hence, assessing soil erosion and soil accumulation moduli and analyzing the dynamic changes are valuable. In this paper, Zhenglan Banner, located on the southern margin of the Hunshandake Sandy Land, was selected as the study area. The soil erosion and accumulation moduli were estimated using the 137Cs and 210Pbex composite tracing technique, and the dynamics of soil erosion and soil accumulation were analyzed during two periods. The results are as follows: (1) the regional 137Cs reference inventory was 2123.5±163.94 Bq/m 2, and the regional 210Pbex reference inventory was 8112±1787.62 Bq/m 2. (2) Based on the 137Cs isotope tracing analysis, the erosion moduli ranged from -483.99 to 740.31 t·km -2·a -1. Based on the 210Pbex isotope tracing analysis, the erosion moduli ranged from -441.53 to 797.98 t·km -2·a -1. (3) Compared with the earliest 50 years, the subsequent 50 years exhibited lower soil erosion moduli and accumulation moduli. Therefore, the activities of local sand dunes weakened, and the quality of the local ecological environment improved. The multi-isotope composite tracing technique combining the tracers 137Cs and 210Pbex has potential for similar soil erosion studies in arid or semiarid regions around the world. 相似文献
3.
内蒙古浑善达克沙地南缘 137Cs、 210Pbex复合示踪研究 总被引：2，自引：0，他引：2
土壤风蚀是导致土地退化、荒漠化以及大气扬尘、风沙天气的重要原因。内蒙古浑善达克沙地南缘是国家主体功能区规划确定的“两屏三带”的重要部分,科学估算本地区土壤风蚀强度及其变化,是地区生态安全和生态建设成效评估的重要内容。选择浑善达克沙地南缘的正蓝旗为研究区,运用 137Cs、 210Pbex复合示踪技术,对研究区土壤侵蚀速率及其变化进行了分析。结果表明：① 研究区内 137Cs本底值为2123.5±163.94 Bq·m -2, 210Pbex本底值为8112±1787.62 Bq·m -2。② 基于 137Cs同位素示踪分析,研究区侵蚀模数为-483.99~740.31 t·km -2·a -1;基于 210Pbex同位素示踪分析,研究区侵蚀模数为-441.53~797.98 t·km -2·a -1。③ 与20世纪20-70年代相比,20世纪70年代以来土壤侵蚀与堆积速率明显降低,研究区风沙活动明显减弱,区域生态环境质量得到改善。综合 137Cs和 210Pbex的多同位素复合示踪技术在干旱、半干旱地区土壤侵蚀研究中具有较大的潜力。 相似文献
4.
土地利用/覆盖变化对地表蚀积过程的影响——来自137Cs示踪的证据 总被引：1，自引：0，他引：1
土地利用/覆盖变化不仅影响地表137Cs总量的再分配，而且显著影响土壤137Cs剖面分布。坝上地区各类土地利用/覆盖条件下137Cs总量的再分配，显示该区总体处于风蚀环境，其中农田和撂荒地是风蚀最严重的土地利用类型；137Cs剖面分布则指示了土地利用/覆盖变化过程中的土壤风蚀/堆积过程的转换，蚀积过程的转换证实了风蚀重灾区退耕还林还草，特别是退耕还草，对控制土壤风蚀、改善生态环境的重要意义。分析还认为，利用137Cs示踪方法计算土壤风蚀/堆积速率时，应格外注意样地的土地利用/覆盖变化过程。 相似文献
5.
I. D. L. Foster T. M. Mighall H. Proffitt D. E. Walling P. N. Owens 《Journal of Paleolimnology》2006,35(4):881-895
We present 137Cs profiles for three low lying coastal lagoons in Southwest England that show a decline in activity with sediment depth.
137Cs inventories are lower than expected by comparison with local reference inventories despite the fact that sampling was undertaken
in the deep-water zone of each lake where sediment and 137Cs focusing would be expected. At all three locations, lake sediment 7Be and unsupported 210Pb (210Pbun) inventories are not significantly lower than the local reference inventory. 137Cs inventories in the study cores range from 38 to 95% of local reference inventories. The standing water level and mud: water
interface at two sites are below maximum tide level and, at all three sites, salinity increases significantly in the water
columns between low and high tide and in the pore waters of the underlying sediments. We suggest that the difference in hydrostatic
pressure between sea level and standing water levels in the lagoons forces salt water up through the sediment column and that
monovalent cations (especially Na+ and K+) replace 137Cs on exchange sites leading to the upward migration and loss of 137Cs. Rising sea levels may therefore contribute to remobilisation and release of 137Cs to the aquatic environment from the sediments of coastal lagoons. 相似文献
6.
Soil erosion is a global environmental problem, and anthropogenic fallout radionuclides offer a promising tool for describing and quantifying soil redistribution on decadal time scales. To date, applications of radioactive fallout to trace upland sediment transport have been developed primarily on lands disturbed by agriculture, grazing, and logging. Here we use 137Cs to characterize and quantify soil erosion at the Konza Prairie Long-Term Ecological Research (LTER) site, an undisturbed grassland in northeastern Kansas. We report on the small scale (< 10 m) and landscape scale (10 to 1000 m) distribution of fallout 137Cs, and show significant variability in the concentrations and amounts of 137Cs in soils at our site. 137Cs soil concentrations and amounts typically vary by 10% to 30% on small scales, which most likely represents the spatial heterogeneity of the depositional processes. Landscape scale variability of soil 137Cs was significantly higher than small scale variability. Most notably, soils collected on convex (divergent) landforms had 137Cs inventories of 2500 to 3000 Bq m− 2, which is consistent with the expected atmospheric inputs to the study area during the 1950s and 1960s. Concave landforms, however, had statistically lower inventories of 1800 to 2300 Bq m− 2. The distribution of 137Cs on this undisturbed landscape contrasts significantly with distributions observed across disturbed sites, which generally have accumulations of radioactive fallout in valley bottoms. Because the upslope contributing area at each sampling point had a significant negative correlation with the soil inventory of 137Cs, we suggest that overland flow in convergent areas dominates soil erosion at Konza on time scales of decades. Very few points on our landscape had 137Cs inventories significantly above that which would be predicted from direct deposition of 137Cs on the soil surface; we conclude therefore that there is little net sediment storage on this undisturbed landscape. 相似文献
7.
8.
The~(137)Cs activity and its geographical significance in terrestrial ecosystem of Great Wall Station, Antarctica 
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下载免费PDF全文 The radioactive isotope 137 Cs is one of the important tracers for studying the physical processes and the human impacts on the environment. Based on the investigation results of the terrestrial ecosystem of Great Wall Station, Antarctica, it was shown that there are some artificial radioactive elements 137 Cs in Antarctic terrestrial ecosystem. The sequence of 137 Cs specific activities is as follows: crustaceous lichen>fruticose lichen>surfacemoss>surface soil, and the crustaceous lichen is one of the most sensitive ways in monitoring the impact of the longterm diffusion of 137 Cs on the environment. 相似文献
9.
Jerry C. Ritchie Jeffrey E. Herrick Carole A. Ritchie 《Journal of Arid Environments》2003,55(4):737-746
A hypothesis for understanding the stability of northern Chihuahuan Desert landscapes is that the distribution of soil resources changes from spatially homogeneous in arid grasslands to spatially heterogeneous in invading shrublands. Since radioactive fallout 137Cesium (137Cs) was deposited uniformly across the landscape during the 1950s and 1960s and was quickly adsorbed to soil particles, any redistribution of 137Cs across the landscape would be due to soil redistribution or instability at either plant-interspaces or on a landscape scale. The concentration of 137Cs in soils collected from different vegetation communities (black grama grass, tarbush, tobosa grass, and mesquite) at the USDA-ARS Jornada Experimental Range in the Northern Chihuahuan Desert in New Mexico was determined. At the black grama grass and tobosa grass sites, 137Cs was uniformly distributed at the plant interspace scale. At the mesquite sites, 137Cs was concentrated in the dune area under mesquite shrubs with little to no 137Cs in the interdune areas. 137Cs data support the hypothesis that significant soil redistribution has occurred at dune sites created by invading mesquite. In the arid grassland-shrub sites with black grama grass, tobosa grass, and tarbush the 137Cs data support the hypothesis of spatially homogeneous distribution of soil resources. High concentrations of 137Cs in the biological soil crusts (0–5 mm) at the tarbush sites indicate that biological soil crusts can contribute to the stability of these sites. 相似文献
10.
Evaluating the mobility of137Cs,239+240Pu and210Pb from their distributions in laminated lake sediments 总被引：1，自引：0，他引：1
Post-depositional mobility of137Cs,239+240Pu and210Pb was assessed in six small lake basins by comparing sedimentary nuclide profiles with their known fallout history. Laminae couplets, when present, were determined to be varves because the137Cs and239+240Pu 1963 fallout peaks are present in laminae couplets corresponding to years 1962–1964. There is no evidence of mobility of210Pb, because 1) mass accumulation rates based on210Pb agree with those based on137Cs and239+240Pu peak depths and with those based on varve counts, and 2)210Pb ages agree with varve ages. Significant mobility of137Cs is evident from the penetration of137Cs to depths 15–20 cm deeper than239+240Pu. Deep penetration of137Cs in spite of a sharp gradient below the peak is interpreted by a numerical model to suggest that137Cs is present in two distinct forms in these sediments, 67–82% as an immobile form and 18–33% reversibly adsorbed with a K
d
of approximately 5000. The profiles can be interpreted equally well assuming a small portionof the total137Cs was present as an extremely mobile phase (K
d
5000) in the months to years following peak fallout, slowly becoming more strongly adsorbed. High NH
4
+
concentrations in porewaters may enhance diffusion of the mobile form of137Cs, but not of the immobile form of137Cs that defines the sharp gradient. Mobility of137Cs is likely also enhanced by the low clay content and the high porosity of these sediments. Thus the first detection of137Cs in the sediments cannot automatically be assumed to correspond to a date of 1952 (initial testing of thermonuclear weapons), although the depth of the peak can be assumed to correspond to 1963 (the year of maximum fallout from testing of thermonuclear weapons).239+240Pu is a more reliable sediment chronometer than137Cs because it is significantly less mobile.This is the sixth of a series of papers to be published by this journal following the 20
th
anniversary of the first application of210Pb dating of lake sediments. Dr P.G. Appleby is guest editing this series. 相似文献
11.
Using unsupported lead-210 measurements to investigate soil erosion and sediment delivery in a small Zambian catchment 总被引：7，自引：0，他引：7
Traditional techniques used to assemble information on rates of erosion and soil redistribution possess many important limitations. As a result, the use of environmental radionuclides, and more particularly 137Cs measurements, has attracted increasing attention in recent years as a means of obtaining spatially distributed information on rates of erosion and deposition. The application of the 137Cs approach is, however, hampered in some areas of the world where 137Cs inventories are low and the low concentrations of 137Cs found in soils and sediments cause problems for laboratory analysis. These problems will increase as time progresses due to the radioactive decay of the existing inventory, most of which was deposited as fallout ca. 40 years ago. This contribution explores the potential for using another fallout radionuclide, namely unsupported 210Pb, as an alternative to 137Cs, in the small (63 km2) Upper Kaleya catchment in southern Zambia where 137Cs inventories are already very low. The approach employed with unsupported 210Pb is similar to that used for 137Cs, although the essentially constant fallout of unsupported 210Pb through time means that the resulting estimates of erosion and soil redistribution rates reflect a longer period of time (ca. 100 years rather than ca. 40 years). The estimates of erosion and deposition rates derived from the unsupported 210Pb measurements are used to construct typical sediment budgets for the three main land-use types in the Upper Kaleya catchment, namely, commercial cultivation, communal cultivation and bush grazing. The results obtained from the unsupported 210Pb are compared with equivalent results based on 137Cs measurements provided by a previous investigation undertaken in the study catchment. The two sets of results are highly consistent. The study reported confirms the viability of using unsupported 210Pb as an alternative to 137Cs in this environment and demonstrates that conjunctive use of both radionuclides can provide additional information on the erosional history of a study area. 相似文献
12.
Sediment focusing in six small lake basins is inferred from sedimentary radionuclide profiles. The activities of137Cs and9+240Pu do not decrease to zero above the sub-surface maximum but tail off gradually. Similar behavior is observed in the sediments of three lakes for134Cs and60Co, which were added only to the lake. This upward tailing is not caused by bioturbation or erosion from the watershed. Sediment focusing is the likely cause, further substantiated by inventories in deep sediments of9+240Pu and210Pb that are twice as high as expected from atmospheric fallout. Inventories in deep sediments of137Cs are in several cases lower than expected from atmospheric fallout, and cannot be explained by hydraulic flushing from the lakes, as this would require unreasonable flushing rates. The low137Cs inventories and the sedimentary profiles of the137Cs/9+240Pu ratio are consistent with137Cs removal from the water column by boundary scavenging to shallow sediments. The profiles and inventories of all three nuclides could be reproduced with a simple three box model, assuming focusing of shallow sediments (50–60% of total sediment area) to deep sediments with a rate constant of 5–10% yr–1.This is the seventh of a series of papers to be published by this journal following the 20
th
anniversary of the first application of210Pb dating of lake sediment. Dr P. G. Appleby is guest editing this series. 相似文献
13.
14.
137Cs示踪技术在黑土区农业非点源污染负荷研究中的应用 总被引：1，自引：0，他引：1
利用137Cs核素示踪和定位监测相结合,研究松嫩平原黑土区3个旱作坡面土壤的流失厚度和流失速率,坡面土壤流失厚度1.20~5.25 mm/a,侵蚀强度1 355.0~7 558.2 t/(km2·a);近40 a来,松嫩平原黑土区年均入河(湖)农业非点源污染负荷分别为TN 1.43 t/(km2·a)、NH3-N 15.01 kg/(km2·a)、NO3-N 8.51 kg/(km2·a)TP 0.42 t/(km2·a)、PO43--P 1.85 kg/(km2·a);土壤流失氮以有机氮为主;水溶态无机氮占总氮的0.51%,水溶性磷酸盐磷占总磷的0.12%。黑土区农业非点源污染物的输出和水土流失密切相关,深入研究其输移机理及防治措施具有重要的环境意义。 相似文献
15.
青海共和盆地土壤风蚀的137Cs法研究(Ⅱ)——137Cs背景值与风蚀速率测定 总被引：16，自引：5，他引：11
通过对高寒草原背景值样点(RS7)的分析,将共和盆地的137Cs背景值含量确定为(2691.78±196.08) Bq·m-2,基本接近北半球137Cs背景值的平均水平,其137Cs剖面满足尖峰分布函数,与公认的理论分布(即负指数分布)相比,呈现出峰值下移和曲线趋平的现象,可能与近几十年来137Cs的稳定下渗有关。应用137Cs背景值剖面分布函数,建立了风蚀速率的137Cs估算模型,估算出四个样方的土壤风蚀速率,并由此转化为区域风蚀速率,计算出共和盆地区域土壤风蚀速率为12.556 t·hm-2·a-1,通过蚀积平衡检验,其误差水平小于10%。并分析了风蚀物的输出途径及其所占比例。 相似文献
16.
我国350多个盐湖湖表卤水水化学成分综合研究表明,成矿元素K、Li、B主要分布在青藏高原地区,但新疆一些富K、B盐湖也具有较好的开发潜力。我国盐湖卤水中的Br、I、Rb、Cs呈现明显的区域分异,富Br和I盐湖主要分布在内蒙古的中东部,而Rb和Cs则主要分布在青藏高原地区。我国盐湖区按主要成矿元素禀赋情况可以分为3种类型,K+B+Li资源综合利用型;K+B(Li)资源综合利用型以及单一的K(B或Li)资源利用型。青藏高原地区的盐湖卤水矿床以前两者为主,新疆和内蒙的盐湖则以后两者为主。 相似文献
17.
滇西和黔中表土中7Be与137Cs分布特征对比研究 总被引：15，自引：2，他引：15
滇西和黔中28个表土剖面分层土样^7Be、^137Cs比活度对比分析可见：滇西地区表土层顶部^7Be/^137Cs为100－1000，而黔中地区仅10－100；两地区表土层中^7Be的表观比活度和最大渗透深度总体相近；^137Cs在黔中表土层中的比活度总体较滇西地区略高。而黔中表土中^7Be累计值的偏低现象，映射了该地区强烈的水土流失。为解释滇西和黔中地区之间表土层顶部^7Be/^137Cs的地区差异，需进一步讨论两核素的湖泊沉积物蓄积特征。 相似文献
18.
A. Laissaoui M. Benmansour N. Ziad M. Ibn Majah J. M. Abril S. Mulsow 《Journal of Paleolimnology》2008,40(3):823-833
Global fallout is the main source of anthropogenic radionuclides in the Mediterranean Sea. This work presents 137Cs, 239+240Pu and 241Am concentrations in the water column in the southwest Alboran Sea, which was sampled in December 1999. A sediment core was
taken at 800 m depth in the area (35°47′ N, 04°48′ W). 210Pb, 226Ra, 137Cs and 239+240Pu specific activities were measured at multiple depths in the core for dating purposes. 137Cs and 239+240Pu profiles did not show defined peaks that could be used as time markers, and they extended up to depths for which the 210Pb-based constant rate of supply (CRS) dating model provided inconsistent dates. These profiles can be useful to test dating
models, understood as particular solutions of a general advection–diffusion problem, if the time series of radionuclide inputs
into the sediment is provided. Thus, historical records of depth-averaged 137Cs and 239+240Pu concentrations in water, and their corresponding fluxes into the sediment, were reconstructed. A simple water-column model
was used for this purpose, involving atmospheric fallout, measured distribution coefficient (k
d) values, and a first-estimate of sedimentation rates. A dating model of constant mixing with constant sedimentation rate
was applied successfully to three independent records (unsupported 210Pb, 137Cs and 239+240Pu), and provided the objective determination of mixing parameters and mass sedimentation rate. These results provide some
insight into the fate of atmospheric inputs to this marine environment and, particularly, into the contribution from the Chernobyl
accident. 相似文献
19.
基于氢氧同位素和水化学的祁连山老虎沟冰川区径流过程分析 总被引：2，自引：0，他引：2
基于2012-2013年两个消融期在祁连山老虎沟冰川区连续2 a采集的冰川融水径流、雪冰以及降水样品,分析探讨了冰川区水体介质中氢氧同位素和水化学要素(主要化学离子、pH值、TDS和电导率等)在消融期的变化过程及特征。结果表明:祁连山老虎沟雪冰融水中的氢氧同位素值(δD和δ18O)表现出明显的消融期随月份波动,先升高再降低的趋势,在7月份表现出高值,反映了冰川消融强弱程度的变化过程。冰川径流中同位素含量与冰雪融水接近,且处于当地降水线上,其主要来自冰雪融水和降雨补给。老虎沟冰川融水径流水化学主要表现为Ca-Na-HCO3-SO4和Ca-Mg-HCO3-SO4型,其组成特征也表现出随消融过程而变化。对氢氧同位素和化学要素组成在消融期(6~9月)随时间的变化过程进行了分析,表明结合冰川区氢氧同位素和化学要素(包括化学离子、TDS、pH值和电导率等)的组成可以区分雪坑和新雪、河水的组分变化,可以反映冰川融水径流在消融期的变化过程。 相似文献
20.
Yan Ping Dong Zhibao Dong Guangrong Zhang Xinbao Zhang Yiyun 《Journal of Arid Environments》2001,47(4):443
The world fallout of caesium-137 (137Cs) associated with nuclear weapons testing during the 1950s and 1960s has provided a valuable man-made tracer for studies of soil erosion and sediment delivery. But relatively few researchers have used it to estimate wind erosion. In this paper, the137Cs technique is introduced into the study of wind erosion and its modern processes in the Qinghai-Tibet Plateau. Two137Cs reference inventories of 982·11 and 2376·04 Bq m−2was established preliminarily, which distribute in the south and mid-north parts of the study area respectively. By analysing the patterns of137Cs depth profiles from sampling sites, the aeolian processes of erosion and deposition along nearly 40 years has been revealed, i.e. the shrub coppice dunes(S1) and semi-fixed dunefields (S3) had experienced the alternation of erosion and deposition, while the grasslands (S4, S6 and S7) and dry farmlands (S5) suffered erosion only. By using the137Cs model, the average wind erosion rates for shrub coppice dune (S1), semi-fixed dunefields (S3), dry farmlands (S5) and grasslands (S4, S6 and S7) were estimated to be 84·14, 69·43, 30·68 and 21·84 tha−1a−1respectively, and for the whole Plateau, averaging 47·59 ha−1a−1which can be regarded as the medium erosion standard. These results derived from137Cs for the first time have significant implications for the further research of wind erosion and desertification control in the Qinghai-Tibet Plateau. 相似文献