紫色丘陵区小流域土壤侵蚀产沙空间分布的137Cs法初步研究

该文通过紫色丘陵区响水滩小流域不同土地利用类型、不同坡度和坡长、不同地貌部位土壤剖面中137Cs含量的测定与分析,对其侵蚀空间分布进行了估算.研究结果表明:该流域137Cs含量的背景值为1870 Bq/m2;流域内坡耕地、林地的年平均侵蚀强度分别为4468、1759 t/(km2·a);土壤侵蚀量与坡长、坡度均指数相关;丘顶、丘坡和鞍部的年平均侵蚀强度分别为2125、4676、3625 t/(km2·a).结果表明土地利用类型、坡长和坡度、地貌部位对土壤侵蚀量影响很大,坡耕地是该流域泥沙的主要来源.     

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。     

沂蒙山区土壤侵蚀的137Cs示踪法初步研究

沂蒙山区是我国北方典型的土石山区,当地土壤由片麻岩、砂岩发育而来,质地疏松易流失,缺乏对泥沙侵蚀监测的长期观测数据。本研究采集了山东省沂蒙山区某一小流域的48个土样共72个样品,利用137Cs示踪技术,确定该地区土壤中的137Cs背景值约为1 740 Bq m-2,并利用杨浩等人的土壤侵蚀定量模型,对该流域土壤侵蚀进行了初步估算。估算结果表明该地区非耕地土壤侵蚀的平均速率为2 531 t km-2a-1,坡耕地土壤侵蚀的平均速率为6 953 t km-2a-1。由于人类耕作活动以及地形的影响,坡耕地土壤侵蚀严重,土壤侵蚀速率在坡面上呈复杂变化。当地土壤流失严重,使得土壤涵蓄水能力下降,加剧了洪涝、干旱灾害的发生,影响当地农业的可持续发展和人们生活水平的提高。     

基于137Cs的青藏高原高寒草甸土壤侵蚀及碳流失估算

[目的] 定量分析青藏高原高寒草甸土壤侵蚀状况及其伴随的碳流失,为全面评估土壤侵蚀影响,实施有效水土保持措施提供参考。[方法] 结合¹³⁷Cs示踪技术与前人研究,对青藏高原高寒草甸土壤的整体侵蚀水平及其土壤有机碳流失进行了估算。[结果] 未受人为扰动的高寒草甸土壤自上而下表现出3个层次(A,B和C层)的理化性质特征,其¹³⁷Cs分布遵循显著指数递减模式。目前,高原草甸土壤年均侵蚀模数约为77~230 t/km²,推测其每年直接导致的土壤有机碳损失量平均不低于4.86 t/km²。[结论] 青藏高原高寒草甸土壤侵蚀水平整体较弱,但因土壤侵蚀流失的有机碳不容忽视。在未来气候变化背景下,升温导致的土壤湿度下降对植被生长的限制,以及人类活动的影响,较大可能成为诱使青藏高原草甸土壤退化和有机碳流失的潜在因素。     

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.137Cs作为一种有效的示踪剂,在国内外越来越多地用于中长期(40余年)以来的土壤侵蚀模数的估算.采用137Cs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137Cs基准值为2107Bq/m2;对于表土质地较为粘重的非耕作红壤而言,137Cs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137Cs分布深度通常在15cm以内,而耕作土中则达30cm;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11.2～14.5t/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.     

利用137Cs示踪技术研究滇池流域土壤侵蚀

核素示踪技术研究作为一种新的土壤侵蚀研究方法,已经在土壤侵蚀研究中获得了极大应用,并在土壤侵蚀的沉积、侵蚀、运移研究上取得许多成果。采用放射性核素作为土壤示踪剂,可以很好地进行流域尺度的范围研究,且可靠性比较高,省时省力。云贵高原在处于我国的西南地区,是我国南方水土流失严重的地区之一。本文应用137Cs示踪技术,研究了云南省滇池流域土壤侵蚀的强度分异规律:坡地不同地貌部位的土壤侵蚀速率是坡中部>坡下部>坡上部;不同土地利用类型和方式下的土壤平均侵蚀速率是耕地>非耕地。研究表明,整个流域平均土壤侵蚀速率为1 280 t km-2a-1,属于轻度侵蚀,地貌部位、坡度以及土地利用方式是影响土壤侵蚀的主要因素。     

赣南红壤丘陵区137Cs示踪土壤侵蚀对土壤养分元素的影响

赣南红壤丘陵区是我国土壤侵蚀与土地退化比较严重的地区,以南丰县为例,应用137 Cs示踪技术探讨不同土地利用方式下土壤侵蚀与养分元素的关系。结果表明:(1)湿地松林、桔园、水田3种土地利用方式作用下土壤中137 Cs与养分元素分布差异显著,在垂直剖面上,湿地松林137 Cs含量呈指数递减分布,水田与桔园137 Cs含量因人为干扰在耕层内均匀分布;有机质与137 Cs有相似的分布特征;全氮、碱解氮、速效磷、速效钾含量均呈现一定表聚性。(2)位于坡地的2种土地利用方式中,湿地松林137 Cs、全氮、碱解氮、速效磷、速效钾、有机质含量均表现为下坡>上坡>中坡;桔园137 Cs活度表现为中坡>下坡>上坡,全氮、碱解氮、速效磷表现为下坡>中坡>上坡,而速效钾、有机质最大值均出现在上坡。(3)相关性分析表明,土壤137 Cs与有机质、全氮、碱解氮显著正相关,表明小流域有机质、氮元素可能与137 Cs有相同的物理运移方式,pH与137 Cs显著负相关,速效磷、速效钾则与137 Cs不相关。(4)3种土地利用方式中位于小流域谷地的水田137 Cs、有机质、全氮、碱解氮含量最高,坡地上桔园坡面137 Cs与土壤养分元素含量均高于湿地松林地,表明一定程度的坡改梯桔园种植模式能有效缓解土壤侵蚀与养分流失,改善区域生态环境。     

三峡库区紫色土坡耕地土壤侵蚀的137Cs示踪研究

坡耕地是三峡库区的重点水土流失区和河流泥沙的主要来源地.采用~(137)Cs示踪技术对三峡库区紫色土坡耕地的土壤侵蚀速率进行了定量研究.结果表明,新政小流域的~(137)Cs本底值为1 420.9 Bq/m~2;平均坡度为11.4°的缓坡耕地的~(137)Cs面积活度介于398.5～1 649.6 Bq/m~2之间,坡长加权平均值为816.0Bq/m~2;采用改进的简化质量平衡模型计算了坡耕地的土壤侵蚀速率,结果得出该坡地的土壤侵蚀模数介于-3 358.8～4 937.4 t/(km~2·a),其加权平均值为1 294.6 t/(km~2·a).受犁耕作用的影响,坡耕地两个坡段的土壤侵蚀速率随坡长增加大致都呈下降趋势,并在坡段下方出现了堆积.坡耕地土壤侵蚀速率不高的原因,一方面是由于所研究坡耕地属于缓坡,坡度较小,另一方面则是由于当地农民总结出了一套有效防止水土流失的耕作方式,使得土壤侵蚀强度大大降低.     

黄土峁坡侵蚀的137Cs法研究

本文运用¹³⁷Cs法,对陕北峁坡耕地的土壤侵蚀与泥沙运移进行了研究,定量地分析了峁坡侵蚀的特征,指出峁坡侵蚀存在由上往下呈强烈、减弱,再强烈、再减弱的波动。并利用非农耕地和农耕地土壤侵蚀公式,计算了峁顶非农耕地自1963年以来的侵蚀模数为1068t/（km²·a）;农耕地的侵蚀模数为4059t/（km²·a）。并与径流试验场实测的梁峁坡坡耕地侵蚀模数进行了对比分析。     

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.     

利用137Cs估算土壤侵蚀速率的定量模型

A quantitative model was developed to relate the amount of ^137Cs loss from the soil profile to the rate of soil erosion,According th mass balance model,the depth distribution pattern of ^137Cs in the soil profile ,the radioactive decay of ^137Cs,sampling year and the difference of ^137Cs fallout amount among years were taken into consideration.By introducing typical depth distribution functions of ^137Cs into the model ,detailed equations for the model were got for different soil,The model shows that the rate of soil erosion is mainly controlled by the depth distrbution pattern of ^137Cs ,the year of sampling,and the percentage reduction in total ^137Cs,The relationship between the rate of soil loss and ^137Cs depletion i neither linear nor logarithmic,The depth distribution pattern of ^137Cs is a major factor for estimating the rate of soil loss,Soil erosion rate is directly related with the fraction of ^137Cs content near the soil surface. The influences of the radioactive decay of ^137Cs,sampling year and ^137Cs input fraction are not large compared with others.     

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.     

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.     

应用137Cs示踪技术估算土壤侵蚀的若干问题探讨

[目的]探讨用~(137)Cs示踪技术估算土壤侵蚀量方法(以下简称"~(137)Cs示踪方法")所存在的几个关键问题,促进该方法的标准化和系统化。[方法]对大量已发表的相关文献进行分析,根据作者的研究经验,归纳出~(137)Cs示踪方法在实践应用中所存在的核心问题。[结果]~(137)Cs示踪方法中关于~(137)Cs在空间是均匀分布的假设存在不合理性,不能直接用于定量估算单钻点取样的土壤侵蚀量。~(137)Cs活度的空间变化存在随机性的成分。敏感度和不确定性分析结果证明~(137)Cs活度的空间随机变化量是~(137)Cs示踪方法不确性的最大来源。[结论]可以用多钻点样本平均值来减少~(137)Cs随机变化量所引起的侵蚀估算误差。以统计学为基础的试验设计和采取独立样本的办法可以消除该误差。虽然~(137)Cs模型已被广泛应用,但由于缺乏长期观测资料诸多模型还处在理论研究阶段,没有得到严格的验证和评判。因为不同模型估算的侵蚀量差别甚大,模型验证和筛选对该方法的成功运用至关重要。     

陇东黄土高塬沟壑区土壤侵蚀的137Cs法研究

该文通过运用铯－１３７法对陇东黄土高塬沟壑区土壤侵蚀进行研究，定量地分析了塬、坡、沟各土地利用类型的侵蚀及产沙。结果表明，通过生物及工程措施治理后的沟谷其侵蚀量都大大减小，然而塬面侵蚀问题却相对突出，塬面侵蚀量不可忽视。     

中国西南薄层砾石土喀斯特坡地土壤的137Cs分布特点

The fallout radionuclide cesium-137(137 Cs) has been widely employed as a tracer for assessment of soil loss from thick uniform soils;however,few studies have been conducted on thin stony soils on slopes underlain by carbonate rocks which are widely distributed in karst areas.Information derived from 137 Cs measurement of soil samples collected along a carbonate rock slope with thin stony soil where neither soil erosion nor deposition occurred was used to investigate the characteristics of 137 Cs redistribution in a karst area of Southwest China.The results indicated that the 137 Cs inventories of the surface soil on the slope studied were much lower than that of the local 137 Cs reference inventory and the 137 Cs activities were much higher than those on slopes with thick uniform soils.The spatial distribution of 137 Cs inventories was characterized by considerable variation.The high 137 Cs depletion in the stony soil of the slope studied was mainly because a considerable proportion of the fallout input of 137 Cs could be lost with runoff and the dissolution of carbonate particles in the soil promoted the loss of 137 Cs.These demonstrated that the rates of soil loss could not be estimated from the degree of depletion of the 137 Cs inventory relative to the local reference inventory for the thin stony soil of the rocky slope underlain by carbonate rocks in the study area in the way that has been widely used in areas with thick uniform soils.