核素比率在土壤侵蚀区的应用探讨--以210Pbex/137Cs为例

环境放射性核素7B e、137C s和210Pb为测量土壤侵蚀和沉积速率提供了一种重要的方法。在某些情况下,由于受各种因素的影响,单一核素进行示踪研究很难精确测量,而核素比率的方法作为有益的补充,能够精确测量土壤侵蚀量的多少。这篇文章介绍W a llbrink和M urray在S t.H e lens森林区用210Pbex/137C s方法测量土壤侵蚀的情况,了解国外的研究动态,对此也提出在应用核素比率法中应注意的问题和展望。     

~(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。     

小流域不同土地利用方式土壤侵蚀分异的^137Cs示踪研究

应用137Cs示踪技术研究了黄土丘陵区典型流域土壤侵蚀强度分异规律,并对其原因进行了分析。结果表明,传统作业的果园地土壤侵蚀较坡耕地、生态林地严重;直接还林地土壤侵蚀较撂荒地严重;峁坡阳面人工林地土壤侵蚀较谷坡阴面人工林地严重;退耕时间短的地块土壤侵蚀较退耕时间长的地块严重。改善土地管理方式、因地制宜进行退耕地的植被建设是有效遏制土壤流失的关键点。     

黄土高原沟壑区谷坡农地侵蚀及产沙的137Cs法研究

该通过运用铯－１３７法对黄土高原沟壑区陇东南小河沟龙谷坡农耕地侵蚀进行研究，定量地分析了其侵蚀及产沙。结果表明：在老谷坡农地内其土壤侵蚀量很，但其输移率却很低，即其真正流失量较小，存在大量地内堆积。通过修建梯田，可使其流失量大大减小，梯田较坡耕地拦沙效益高出９６．５％。     

川中丘陵区人工刨地耕作方式下紫色土坡耕地侵蚀速率的137Cs和210Pbex双核素示踪法研究

Purple soils are widely distributed in the Sichuan Hilly Basin and are highly susceptible to erosion, especially on the cultivated slopes. Quantitative assessment of the erosion rates is, however, difficult due to small size of the plots of the manually-tilled land, the complex land use, and steep hillslopes. 137Cs and 210Pbex (excess 210Pb) tracing techniques were used to investigate the spatial pattern of soil erosion rates associated with slope-land under hoe tillage in Neijiang of the Sichuan Hilly Basin. The 137Cs and 210Pbex inventories at the top of the cultivated slope were extremely low, and the highest inventories were found at the bottom of the cultivated slope. By combining the erosion rates estimates provided by both 137Cs and 210Pbex measurements, the weighted mean net soil loss from the study slope was estimated to be 3100 t km-2 year-1, which was significantly less than 6930 t km-2 year-1 reported for runoff plots on a 10°cultivated slope at the Suining Station of soil Erosion. The spatial pattern of soil erosion rates on the steep agricultural land showed that hoe tillage played an important role in soil redistribution along the slope. Also, traditional farming practices had a significant role in reducing soil loss, leading to a lower net erosion rate for the field.     

宁南黄土高原阳洼流域137Cs分布及侵蚀特征研究

利用137Cs示踪方法,对宁南黄土高原阳洼流域土壤137Cs分布及土壤侵蚀进行了初步研究。结果表明:流域137Cs基准值为(1 966.99±112.06)Bq/m2。流域内林草地土壤剖面137Cs呈指数型分布,坡耕地137Cs在耕层内呈均一分布。受坡位影响,坡耕地上坡137Cs质量活度为中、下坡的25.14%~27%。流域内坡耕地土壤侵蚀最高,平均为3 889.95 t/km2,自然荒坡最小,仅为坡耕地的17.83%,坡耕地是流域泥沙的主要侵蚀溯源区。阳洼流域土壤侵蚀存在明显的空间格局,不同土地类型下土壤137Cs面积活度、土壤侵蚀模数呈斑块状镶嵌分布,以靠近流域西南边界、中部及东南部区域土壤侵蚀模数最大,平均侵蚀速率在3 405.59~7 080.73 t/(km2.a),沉积与侵蚀明显区域间有过渡区域。坡度是影响该流域土壤侵蚀空间变化的主导因子,但土壤侵蚀速率并不简单随坡度增加而增大,它还受土地利用方式、坡位、降雨等因素影响。     

Use of Cs to estimate tillage- and water-induced soil redistribution rates on agricultural land under different use and management in central-south Chile

The purpose of this research was to evaluate the applicability of conventional ¹³⁷Cs sampling and a simplified approach, for estimating medium-term tillage- and water-induced soil erosion and sedimentation rates on agricultural land in Chile. For this purpose, four study sites under contrasting land use and management were selected in central-south Chile. First, a conventional ¹³⁷Cs approach, based on grid sampling was applied, adapting a mass balance conversion model incorporating soil movement by tillage to the site specific conditions of the study region. Secondly, using the same conversion model, the feasibility of estimating soil redistribution rates from measurements of ¹³⁷Cs inventories based on composite soil samples taken along contour lines was also tested at all four sites. The redistribution rates associated with tillage and water and the total rates estimated using both methods correlated strongly at all four sites. The conventional method provides more detailed information concerning the redistribution processes operating over the landscape. The simplified method is suitable for assessing soil loss and sediment accumulation in areas exhibiting simple topography and almost similar slopes along the contour lines. Under these conditions, this method permits faster estimation of soil redistribution rates, providing the possibility of estimating soil redistribution rates over larger areas in a shorter time. In order to optimise the costs and benefits of the methods, the sampling and inventory quantification strategy must be selected according to the resolution of the required information, and the scale and complexity of the landscape relief. Higher tillage- and water-induced erosion rates were observed in the annually ploughed cropland sites than in the semi-permanent grassland sites. Subsistence managed crop and grassland sites also show greater erosion effects than the commercially managed sites. The ¹³⁷Cs methods used permit discrimination between redistribution rates observed on agricultural land under different land use and management. The ¹³⁷Cs technique must be seen as an efficient method for estimating medium-term soil redistribution rates, and for planning soil conservation and sustainable agricultural production under the climatic conditions and the soil type of the region of Chile investigated.     

中国南方红壤地区的137Cs基准点的选取

The ^137Cs vertical distributions in uncultivated and cultivated soils, developed from Quaternary red clay, granite, argillaceous shale, and red sandstone, were studied to develop reliable guidelines for selecting reference sites in southeastern China, which is dominated by strong acidic and/or clay-textured soils, and examine their reliability by comparing them to the reported ^137Cs reference inventory data to see whether they agreed with the global distribution pattern. It was observed that a relatively high proportion of ^137Cs was concentrated in the surface layers of soils with relatively high clay content. In the paddy soils developed from granite more ^137Cs penetrated to depths below the plow layer （about 45.3%）, when compared to those from the other three parent materials. The relatively low soil ^137Cs inventories on crests excluded using the crest as the ^137Cs reference site; instead the paddy field on the hillock plain was selected. Furthermore, within a specific county characterized by great systematic spatial variations of rainfall and topography across the landscape, a significant （P 〈 0.01） and positive linear relationship （r^2 = 0.81） between local ^137Cs inventory and corresponding local annual rainfall was observed. Thus, for areas with large variations in rainfall, a single uniform value of local ^137Cs reference inventory should be used with caution.     

^137Cs法估算南方红壤地区土壤侵蚀作用的初步研究

第四纪红色粘土发育的红壤在我国南方地区分布较广 ,不合理的开发和利用导致植被覆盖破坏严重 ,致使该地区长期以来遭受强烈的土壤侵蚀作用。1 37Cs作为一种有效的示踪剂 ,在国内外越来越多地用于中长期 ( 4 0余年 )以来的土壤侵蚀模数的估算。采用 1 37Cs技术 ,研究第四纪红色粘土发育的红壤典型小流域的土壤侵蚀作用。结果表明 ,该流域的1 37Cs基准值为 2 10 7Bq/m2 ;对于表土质地较为粘重的非耕作红壤而言 ,1 37Cs在土壤剖面中呈指数型分布 ;该流域内山坡和山顶非耕作土的 1 37Cs分布深度通常在 15 cm以内 ,而耕作土中则达 3 0 cm ;对于坡度相对较大 ( 5 .5～ 11°) ,植被条件较差的迎风坡非耕作红壤而言 ,其土壤侵蚀模数达 11.2～ 14 .5 t/hm2 · a;对于坡度较小 ( 1.5～ 4 .5°) ,植被条件较好的背风坡非耕作红壤而言 ,土壤侵蚀模数为 0 .3～ 10 .8t/hm2·a;坡上部水作梯田的侵蚀作用比坡下部的水作梯田小 ,且水作梯田比旱作梯田更有利于水土保持。     

小麦抽穗期和株高的辐射遗传效应

以两个小麦品种为材料,用０、２０、３０、４０ｋｒａｄ的１３７Ｃｓ和６０Ｃｏγ射线辐照,探讨其抽穗期和株高的辐射遗传效应,比较两种辐射源的差异。结果表明：１３７Ｃｓ和６０Ｃｏγ射线均能诱发早熟和矮秆突变,辐射遗传效应显著并相似。说明两种辐射源均可采用,但性状的平均表现与遗传方差、遗传变异系数、遗传力、遗传进度、相对遗传进度等遗传参数值随品种、辐照剂量和辐射世代的不同而异。诱变效果较好的品种是７７中－２８８２,剂量为３０ｋｒａｄ;在Ｍ２、Ｍ３代的辐射遗传效应明显。