利用137Cs技术研究黑土坡耕地土壤再分布特征

利用¹³⁷Cs示踪技术和不同的理论模型研究典型的东北漫岗地形的黑土土壤再分布状况.通过野外采样和模型分析,得出研究区¹³⁷Cs背景值为2 232.75 Bq·m^-2,介于长江三角洲和黄土高原背景值之间,表明¹³⁷Cs沉降与纬度和降水相关.研究区各地貌部位¹³⁷Cs含量在水平方向和深度分布上有很大的分异.坡肩部位¹³⁷Cs含量最低,土壤侵蚀最为强烈;坡顶和坡背侵蚀较为微弱;坡脚和坡足基本上表现土壤沉积.¹³⁷Cs分布深度从坡肩20 cm到坡足80 cm土层,表现出该区经历了强烈的侵蚀和沉积过程.文中采用4种常用的¹³⁷Cs土壤侵蚀模型估计研究区的土壤侵蚀速率,结果表明,PM模型明显低估了土壤侵蚀速率,MBM-1明显高估了土壤侵蚀速率,MBM-2和MBM-3估计的结果较为相近的合理结果.     

利用~(137)Cs大气沉降通量估算土壤侵蚀速率的可行性研究——以辽东湾地区为例

利用日本东京和秋田地区1957—2008年的~(137)Cs年沉降数据和降水数据,对辽东湾地区~(137)Cs的大气沉降通量进行估算;通过建立模型,对用~(137)Cs大气沉降通量来估算土壤侵蚀速率的可行性进行分析。结果表明:辽东湾地区~(137)Cs的大气总沉降通量为1614 Bq·m~(-2);利用该值估算出该区域的年均土壤侵蚀速率为17.39~38.92 t·hm~(-2)·a~(-1),而采用杨浩等(2000)的质量平衡模型估算出该地区年均土壤侵蚀速率为11.97~44.94 t·hm~(-2)·a~(-1);本文计算结果的变异系数为30.5%,低于杨浩等(2000)估算结果的变异系数49%。本文所采用的方法得出的结果与实测大气沉降通量背景值(1845 Bq·m~(-2))得出的结果进行t检验表明,两种方法估算的结果没有显著性差异,说明采用~(137)Cs大气沉降通量来估算土壤侵蚀速率是可行的,有利于简化估算土壤侵蚀速率的方法并提高其精度。     

黑土坡耕地有机碳及其组分累积-损耗格局对耕作侵蚀与水蚀的响应

耕作与水蚀是黑土区坡耕地碳库退化的主导因素,为进一步探究土壤有机碳(SOC)及其组分对不同侵蚀驱动力(耕作、水力)的响应格局,基于该区耕作侵蚀与水蚀模型,在定量表达耕作侵蚀-沉积量与水蚀量的基础上,利用地统计学的方法,分析了东北黑土区典型漫岗地形坡面尺度SOC及其3种组分的空间分布特征.结果表明: 耕作侵蚀与沉积速率分别表现为坡上>坡下>坡中>坡脚和坡脚>坡下>坡中>坡上;水蚀速率表现为坡下>坡脚>坡中>坡上;坡下陡坡位置耕作侵蚀与水蚀协同引起严重的土壤流失.虽然耕作侵蚀速率(0.02～7.02 t·hm^-2·a^-1)远小于水蚀速率(5.96～101.17 t·hm^-2·a^-1),但耕作侵蚀在全坡面范围均可对SOC产生不同程度的影响,而水蚀则主要在坡下径流汇集区显著影响SOC的累积-损耗.受水蚀与耕作侵蚀-沉积作用影响,SOC、颗粒有机碳、水溶性有机碳在侵蚀点含量低于沉积点,而微生物生物量碳变化趋势相反;耕作侵蚀通过影响颗粒有机碳参与SOC的积累-损耗过程.     

137Cs和210Pbex示踪黑土区坡耕地土壤侵蚀对有机碳的影响

通过在野外28.5 hm2的坡耕地上采集土壤样品,定量评价了利用137Cs和210Pbex研究土壤有机碳(SOC)动态的潜力,以探讨东北黑土区土壤侵蚀对土壤有机碳的影响.结果表明:农耕地土壤137Cs、210Pbex和SOC在平面和垂直深度上均具有相似的分布特征.在平面上,尽管受土壤侵蚀沉积的影响,137Cs、210Pbex面积活度及SOC储量变异很大,但它们具有相同的变化趋势.在垂直断面上,侵蚀区137Cs、210Pbex和SOC在0～25 cm耕层内分布均匀,25 cm以下放射性活度减小,SOC含量也相应下降;沉积区0～100 cm深度上137Cs和210Pbex呈现先增加后减小的分布规律,SOC也具有类似的变化特征.农耕地SOC与137Cs、210Pbex呈显著线性相关,表明它们在黑土区农耕地上具有相似的物理运移特征,137Cs和210Pbex可直接用来定量评价黑土侵蚀下SOC的时空分布特点.     

桂西北喀斯特坡地土壤137Cs的剖面分布特征及其指示意义

分析了137Cs及土壤有机碳(SOC)在桂西北典型峰丛坡地及岩溶裂隙中的剖面分布特征,探讨了137Cs方法在喀斯特坡地的适用性及其指示的坡面土壤侵蚀特征.结果表明:所有剖面137Cs与SOC均显著相关,两者可能有相同的流失途径;次生林坡地137Cs主体分布深度在24 cm以内,中上及中坡剖面随深度呈指数递减分布,地表无侵蚀或侵蚀轻微,坡脚剖面呈较严重侵蚀形态;坡耕地剖面137Cs在耕层内均匀分布,中上坡及中坡主体分布深度在15 cm左右,面积活度远低于背景值,土壤侵蚀剧烈,坡脚分布深度至45 cm,呈堆积形态;次生林坡脚剖面、耕地中上坡剖面及所有裂隙剖面,137Cs在主体分布深度以下有断续极微量的分布,指示了喀斯特坡地土壤颗粒有随降雨沿地表负地形向地下流失的趋势,但流失量轻微.     

红壤侵蚀地马尾松林恢复后土壤有机碳库动态

运用RothC(version 26.3)模型,并结合“时空代换法”对长汀河田红壤侵蚀退化地马尾松人工恢复后林地表层(0-20cm)土壤有机碳库的动态变化进行了反演和预测,研究结果表明:RothC 26.3模型的模拟结果能够较好地反映红壤侵蚀地植被恢复过程中土壤有机碳的变化趋势;RothC 26.3模型适用于中亚热带季风气候条件下马尾松林地土壤碳库的动态模拟;侵蚀退化地在马尾松林建植后,林地表层土壤碳吸存速率以非线性的形式上升,并在15-25a时间内达到最大,马尾松恢复后前30a林地土壤平均碳吸存速率约为0.385 tC·hm-2· a-1,自马尾松建植后演替至当地顶级群落(次生林)全过程中平均碳吸存速率约0.156 tC·hm-2·a-1;根据模拟结果得到的拟合方程,计算得到研究区红壤侵蚀退化地的碳饱和容量约为36.85 tC/hm2,固碳潜力约为33.26 tC/hm2.     

黄土区耕作侵蚀及其对总土壤侵蚀贡献的空间格局

耕作能直接造成大量的土壤向坡下运动 ,却在以往土壤侵蚀研究中被忽视。为了定量评价耕作侵蚀以及在坡耕地土壤侵蚀中的重要性 ,通过耕作侵蚀示踪试验及铯 - 1 37示踪的方法对黄土区耕作侵蚀及其对总土壤侵蚀贡献的空间格局进行了研究 ,取得了如下结果 :( 1 )一次耕作造成的单宽土壤搬运量为 2 3.60～ 45 .68kg/m,并从坡地上部和下部向中部逐渐变大 ;( 2 )耕作侵蚀强度主要集中在 70 0～ 2 0 0 0 t/km2 和- 1 2 0 0～ - 2 0 0 0 t/km2 之间 ,分别发生在坡地凸型和凹型部位 ;( 3)总土壤侵蚀强度主要集中在 2 60 0～890 0 t/( km2· a)和 - 2 75 0～ - 3390 t/( km2· a)之间 ,分别发生在坡地凸型部位与凹型部位的上部及坡地凹型部位的下部 ;( 4 )耕作侵蚀占总土壤侵蚀的百分比 ,主要集中在 1 0 %～ 2 8%、- 2 7%～ - 398%和 36%～ 5 4 %之间 ,从坡顶向坡底 ,依次分布在两种侵蚀皆呈侵蚀的部位、耕作侵蚀呈沉积而总土壤侵蚀呈侵蚀的部位及两种侵蚀皆呈沉积的部位。结果表明 ,耕作侵蚀是黄土区坡耕地的一种重要的土壤侵蚀 ,是总土壤侵蚀的重要组成部分 ,水土保持工作中应充分考虑耕作侵蚀及其对总土壤侵蚀贡献的空间格局。     

万山汞矿区表层土壤汞迁移

水土流失是土壤退化的根本原因,是最严重的生态环境问题之一。目前对喀斯特山区土壤侵蚀研究已经进入成熟阶段,但对以典型喀斯特山区为背景、汞污染严重地区因土壤侵蚀发生的汞迁移的研究却很少。本文基于GIS平台,借助通用土壤流失方程(RU-SLE)模型评估研究区侵蚀强度,对万山汞矿区(167.4km2)因土壤侵蚀造成的汞迁移进行了研究。结果表明,万山土壤侵蚀模数为0～600884t·km-2·a-1,微度侵蚀和剧烈侵蚀面积占全区总面积的76.6%,其中剧烈侵蚀对土壤总侵蚀量的贡献率达到90.5%。全区因土壤侵蚀发生的土壤汞(THg)流失量高达505kg·a-1,迁移速率为3.02kg·km-2·a-1。土地利用方式和坡度是影响汞流失的重要因素。旱地和灌木林最易发生汞流失,流失量分别为175和319kg·a-1。本研究不仅为当地治理水土流失、制定水土保持方案奠定了可靠的科学依据,也为当地环境汞污染治理提供了有力的数据支持。     

黑土坡耕地有机碳变化及固碳潜力分析

东北黑土区自开垦以来有机质含量逐渐降低,有机碳库长期处于亏缺状态,理论上也具有较大的固碳潜力。以典型黑土区长期传统作业的坡耕地(30—60 a)为研究对象,通过测定不同坡位(坡上侵蚀区和坡下沉积区)、不同土层(表土和底土)有机碳分布特征,估算不同开垦年限黑土固碳潜力及其恢复至固碳潜力所需的时间。结果表明:(1)总有机碳、有机碳密度以及碳饱和水平均表现为沉积区显著大于侵蚀区,表土显著大于底土,且均在开垦30a坡耕地达到最大值;(2)固碳潜力表现为侵蚀区(1.24—2.89 kg/m~2)显著大于沉积区(0.79—1.04 kg/m~2),底土(0.83—3.59 kg/m~2)显著大于表土(0.6—2.53 kg/m~2),随着开垦年限的增加表现为开垦30 a显著小于开垦40 a、60 a;(3)黑土坡耕地(30—60 a)侵蚀区和沉积区土壤(0—50 cm)达到固碳潜力分别需要20—181 a和13—66 a。黑土坡耕地固碳潜力的时空变异性在农业经营以及修复管理过程中需引起重视,以实现黑土资源的可持续利用。     

137Cs技术量化卧龙自然保护区不同生态系统水土保持能力

不同自然植被的水土保持能力可作为制定水土保持目标的重要参考. 通过应用137Cs技术测算卧龙自然保护区不同自然生态系统过去40年的土壤再分配情况, 以此量化可代表不同气候类型的自然植被的水土保持能力. 卧龙保护区地处四川盆地向青藏高原的过渡地带, 植被类型丰富. 研究选取了可以代表适温针阔叶混交林、耐寒落叶针叶林、耐寒灌丛、耐寒常绿针叶林、高山草甸的五个自然生态系统, 每个系统剖面的土壤净侵蚀速率依次是0.17, 0.16, 0.13, 0.11和0.06 kg/(m²·a), 它们的水土保持能力则正好与此顺序相反. 由于降雨量随海拔升高而增加, 使得不同生态系统的¹³⁷CsCs背景值随海拔不同而在1658.2~3707.2 Bq/m²之间变化. 在相似的气候带内制定水土保持策略时, 这些植被的水土保持效果都是必须要参考的.     

137Cs distribution and accumulation in organs and tissues of sheep in the event of chronic consumption of contaminated fodder in the area of the Chernobyl NPP accident

The regularities of 137Cs distribution and accumulation in organs and tissues of sheep on a farm located in the Chernobyl accidental zone were experimentally estimated. The distribution pattern of 137Cs concentration in organs and tissues is found to depend on the duration of the radionuclide uptake with the ration. During the first 24 h the highest 137Cs concentration is reported in the parenchymal organs; starting from day 30 muscular tissue and kidneys rank first, whereas in the other organs and tissues 137Cs concentration is 1.5-2 times lower. By 137Cs content and accumulation rate the study organs are arranged in a declining order as follows: muscles > > skin > liver > kidneys > heart > spleen. The mathematical models were devised describing the dynamics of increasing with time in 137Cs concentration in muscles, liver and skin. The methodology is suggested for the prediction of levels of 137Cs contamination of the muscular tissue of sheep. The time periods were regulated for sheep feeding with 137Cs contaminated fodder that ensure the production of mutton the radionuclide concentration in which meets the sanitary-hygienic standards.     

137Cs和210Pbex示踪黑土区坡耕地

通过在野外28.5 hm²的坡耕地上采集土壤样品,定量评价了利用¹³⁷Cs和²¹⁰Pb_ex研究土壤有机碳(SOC)动态的潜力,以探讨东北黑土区土壤侵蚀对土壤有机碳的影响.结果表明:农耕地土壤¹³⁷Cs、²¹⁰Pb_ex和SOC在平面和垂直深度上均具有相似的分布特征.在平面上,尽管受土壤侵蚀沉积的影响,¹³⁷Cs、²¹⁰Pb_ex面积活度及SOC储量变异很大,但它们具有相同的变化趋势.在垂直断面上,侵蚀区¹³⁷Cs、²¹⁰Pb_ex和SOC在0～25 cm耕层内分布均匀,25 cm以下放射性活度减小,SOC含量也相应下降;沉积区0～100 cm深度上¹³⁷Cs和²¹⁰Pb_ex呈现先增加后减小的分布规律,SOC也具有类似的变化特征.农耕地SOC与¹³⁷Cs、²¹⁰Pb_ex呈显著线性相关,表明它们在黑土区农耕地上具有相似的物理运移特征,¹³⁷Cs和²¹⁰Pb_ex可直接用来定量评价黑土侵蚀下SOC的时空分布特点.     

137Cs and 90Sr distribution peculiarities in soil and accumulation by pine tree wood and bark depending on edaphotops

The range of researches was made on 137Cs and 90Sr distribution regularities in pine tree plantations depending on different edaphic conditions. It is shown that total radionuclide amount in the forest litter depends on its thickness and is thought to be 10 to 70% for 137Cs and 20 to 60% for 90Sr. When soil fertility come increases from trophotop "A" to "C", 137Cs and 90Sr transfer factors for wood reduce. Soil humidity increase for each grade of trophic net results in increase of 137Cs transfer factors to wood and decrease for 90Sr. Total activity of 37Cs and 90Sr in pine wood plantation depends on plantation productivity and radionuclide transfer factors depending on different plantation conditions. In the most prevailing edaphotops pine wood accumulates 1-3% of 137Cs and 6-11% of 90Sr from total activity of radionuclides in biogeocenosis.     

Assessing the potential of short rotation coppice (SRC) for cleanup of radionuclide-contaminated sites

A small-scale greenhouse investigation was undertaken using Goat willow (Salix caprea) and aspen (Populus tremula) to evaluate the potential of short rotation coppice for remediation of 137Cs- and 90Sr-contaminated sites. Results showed that both species were able to accumulate these radionuclides from a representative disposal soil (aged) and a spiked soil S. caprea accumulating greater levels of 137Cs than P. tremula, with no difference between species for 90Sr accumulation. For each radionuclide, the distribution in both species was similar, with 137Cs accumulation greatest in the roots, whereas 90Sr accumulation was greatest in the leaves. It was also evident that the soil-to-plant transfer factor (Tf) values for 90Sr were greater than for 137Cs, agreeing with differences in the reported bioavailailablity of these radionuclides in soil Based on the Tf values for S. caprea (conservative), estimated remediation times were 92 and 56 yr, for 137Cs and 90Sr, respectively. It is suggested that the selection of Salix species grown in a system of SRC provides a significant opportunity for removal of both 137Cs and 90Sr, primarily due to its higher biomass production. However, for 137Cs phytoremediation investigations into the appropriate use of soil amendments for increasing bioavailability are required.     

Analysis of factors determining the biological availability of 137Cs in forest ecosystem soils

On five forest plots varying in species composition of woody plants and soil properties, 137Cs accumulation by vegetation of the forest understorey has been studied. Differences in 137Cs availability for root uptake are shown to be dependent on a vertical distribution of 137Cs content over the soil profile, percentage of exchangeable 137Cs and distribution of plant root systems (fungous mycelium) in soil. A 137Cs-bioavailability index is suggested and its non-linear relationship with 137Cs transfer factors to different plant species in the understorey is shown.     

Response of changes in soil nutrients to soil erosion on a purple soil of cultivated sloping land

Severe soil erosion of cultivated sloping land in hilly areas of Sichuan, China, has resulted in deterioration of soil quality, and therefore has an adverse impact on crop production. A hillslope of 110 m in length was selected with a slope steepness of 10.12% where the soils were classified as Regosols. Soil samples for determining ¹³⁷Cs, soil organic matter (SOM), total N, P, K, available N, P, K and particle size fraction were collected at 10 m intervals along a transect of the hillslope. Loss of soil nutrients owing to soil erosion was studied by using ¹³⁷Cs technique, and the relationships between ¹³⁷Cs-derived soil redistribution rates and soil nutrients were established over the cultivated sloping land in hilly areas of Sichuan, China (30o26′N, 104o28′E). The values of SOM, total N, available N, P, K and the soil particle fractions of size < 0.002 mm were smaller at upper and middle slope positions where ¹³⁷Cs inventories were lower (i.e., soil erosion rates were higher) than at downslope positions where ¹³⁷Cs inventories were higher (i.e., soil erosion rates were lower). The lowest ¹³⁷Cs inventories were found at the hilltop, showing that besides erosion owing to water flow, tillage also contributed to soil losses, and intensive tillage was mostly responsible for severe erosion at upper slope positions. There were significant differences in SOM, total N, available N, P, K and the soil particle fractions of size < 0.002 mm between different slope segments, and these properties were significantly correlated with slope length. These soil properties were also significantly correlated with ¹³⁷Cs inventories, indicating that both ¹³⁷Cs and nutrient concentrations varied with topographical changes. The variation in soil properties was strongly influenced by erosion-induced soil redistribution, and therefore ¹³⁷Cs inventories mirroring soil redistribution rates would be considered as an integrated indicator of soil quality.     

The accumulation of the technogenic radionuclides by mushrooms in the area affected by the activity of the Krasnoyarsk mining-and-chemical industrial complex

The radionuclide content was measured in mushrooms collected in different sites situated in the zone of the radiation influence on the Mining-and-Chemical Combine at Zheleznogorsk and on the control site, near Krasnoyarsk, in 2002-2004. The analytical investigations of fruiting bodies of 12 mushroom species have revealed three gamma-emitting radionuclides: 7Be, 40K (natural) and 137Cs (artificial). It was found that only three species contain 7Be; activity concentration of 40K is not species- and site-dependent, averaging 1600 Bq/kg. All collected samples contain 137Cs, and its accumulation by mushrooms is species-specific. Suillus concentrates more 137Cs activity than other species and can be used as a bioindicator of soil contamination with radiocesium. The average activity concentration of 137Cs in Suillus granulatus collected in the sites subjected only to aerosol discharges of the MCC is more than twice higher than 137Cs content of the mushrooms collected in the control site--"Krasnoyarsk". The maximum activity concentration of 137Cs in Suillus samples collected in the sites that receive 137Cs with the flood water is an order of magnitude higher, amounting to 8624 Bq/kg. The analysis of the radionuclide distribution in a mushroom shows that 40K activity concentration is the same in caps and stems of Suillus, and 137Cs concentration in Suillus caps is 1.7-2.3 times higher than in stems. Binding of radionuclides by mushroom biomass was determined by chemical fractionation; it was found that the highest activities of 137Cs and 40K are in the exchange-adsorption fraction (56 to 71% of the total content of a radionuclide) and in the organic fraction (23 to 37%). Calculations were made for determination of the coefficients of 40K and 137Cs transfer from the soil to the fruiting body of Suillus.     

Comparative study of 137Cs distribution in broilers and pheasants and possibilities for protection

The aim of the present study was to investigate distribution of (137)Cs in leg and breast meat of broilers and pheasants following single alimentary contamination and administration of two protectors (AFCF and clinoptilolite). The birds were administered a single dose of (137)CsCl, with an activity of 750?Bq. Protectors were given via gastric tube or mixed in the forage pellets. AFCF given via gastric tube decreased the (137)Cs concentration by a factor of 7.8 in broilers leg meat and 7.4 in broilers breast meat. When AFCF was mixed in pellets, the (137)Cs concentration was 19.5 times lower in broilers leg meat and 22.1 times lower in broilers breast meat, than in the control group. In pheasants, AFCF administered via gastric tube decreased the (137)Cs concentration by a factor of 12.4 in leg meat and by a factor of 13.7 in breast meat, respectively. In group 4, where pheasants were administered AFCF mixed in pellets, the (137)Cs concentration was 3.7 times lower in leg and breast meat, than in the control group. For comparison, clinoptilolite administered via gastric tube decreased the (137)Cs concentration 1.8 times in broilers leg meat and 2.0 times in breast meat, compared to the control group. In pheasants, (137)Cs concentration was 2.9 times lower in leg meat and 2.6 times lower in breast meat. Clinoptilolite mixed in the feed had relatively low efficiency of protection in broilers ((137)Cs concentration was 1.4 times lower in leg meat and 1.6 lower in breast meat). A similar trend was observed in pheasants ((137)Cs concentration was 1.6 lower in leg and breast meat).     

Chronic Internal Exposure to Low Dose 137Cs Induces Positive Impact on the Stability of Atherosclerotic Plaques by Reducing Inflammation in ApoE-/- Mice

After Chernobyl and Fukushima Daï Chi, two major nuclear accidents, large amounts of radionuclides were released in the environment, mostly caesium 137 (¹³⁷Cs). Populations living in contaminated territories are chronically exposed to radionuclides by ingestion of contaminated food. However, questions still remain regarding the effects of low dose ionizing radiation exposure on the development and progression of cardiovascular diseases. We therefore investigated the effects of a chronic internal exposure to ¹³⁷Cs on atherosclerosis in predisposed ApoE^-/- mice. Mice were exposed daily to 0, 4, 20 or 100 kBq/l ¹³⁷Cs in drinking water, corresponding to range of concentrations found in contaminated territories, for 6 or 9 months. We evaluated plaque size and phenotype, inflammatory profile, and oxidative stress status in different experimental groups. Results did not show any differences in atherosclerosis progression between mice exposed to ¹³⁷Cs and unexposed controls. However, ¹³⁷Cs exposed mice developed more stable plaques with decreased macrophage content, associated with reduced aortic expression of pro-inflammatory factors (CRP, TNFα, MCP-1, IFNγ) and adhesion molecules (ICAM-1, VCAM-1 and E-selectin). Lesions of mice exposed to ¹³⁷Cs were also characterized by enhanced collagen and smooth muscle cell content, concurrent with reduced matrix metalloproteinase MMP8 and MMP13 expression. These results suggest that low dose chronic exposure of ¹³⁷Cs in ApoE^-/- mice enhances atherosclerotic lesion stability by inhibiting pro-inflammatory cytokine and MMP production, resulting in collagen-rich plaques with greater smooth muscle cell and less macrophage content.