137Cs和210Pbex双核素示踪"三北"防护林区退耕前后坡地土壤侵蚀变化

为查明"三北"防护林建设前后农耕地和退耕地土壤保持效益变化，利用137Cs和210Pbex双核素示踪技术，选择了防护林建设较为成功的张家口坝上地区（风力侵蚀区）作为典型区，研究了农耕地以及退耕地土壤137Cs和210Pbex的剖面变化规律及其示踪的土壤侵蚀变化。结果表明：1）由于耕作的混匀作用，农耕地土壤剖面中137Cs和210Pbex均呈均匀态分布；退耕地土壤剖面中137Cs和210Pbex则表现为表层（0～5cm）浓度最高、下层（5～25cm）浓度均相对较低且分布相对均匀的形态，这表明退耕后坡地土壤137Cs和210Pbex剖面形态均会发生一定变化，退耕驱动土壤137Cs和210Pbex剖面变化导致运用土壤核素估算侵蚀模型在该区域难以适用；2）基于土壤137Cs和210Pbex剖面变化规律，利用210Pbex质量平衡方程，提出了退耕地土壤210Pbex土壤侵蚀估算模型；3）利用137Cs比例模型估算退耕地土壤侵蚀速率为27.94±11.92 (t/hm2·a)，农耕地侵蚀速率为29.11±14.42 (t/hm2·a)，而利用修正后的210Pbex转换模型估算得到"三北"防护林区退耕地造林前平均侵蚀速率为82.16±14.36 (t/hm2·a)，造林后平均侵蚀速率为-41.28±33.91 (t/hm2·a)；农耕地造林前平均侵蚀速率为68.55±22.11 (t/hm2·a)，造林后平均侵蚀速率-8.52±47.32 (t/hm2·a)。这表明137Cs示踪技术主要表征了1963年以来该区坡地土壤侵蚀和沉积的平均结果，而210Pbex示踪技术则可以较好地示踪防护林建成前后的土壤侵蚀变化。此外，研究结果也表明，相比于"三北"防护林建成之前，建成之后该区农耕地和退耕地的土壤侵蚀速率均呈显著下降趋势，且均由前期的风沙侵蚀转变成了风沙沉积。     

Soil Redistribution investigations by combined use of soil 137Cs and selected chemical properties

Abstract

To improve the methods of application of phosphorus or supply of soil P to Azolla (A. microphylld), basal application, split application, inoculation of P-enriched Azolla, and soil disturbance were compared. Soil disturbance did not increase the floodwater P content. Phosphorus was applied to inoculum production plots to enrich Azolla with P. Thus, phosphorus-enriched Azolla could multiply 5–7 times after inoculation until it became P deficient. Trials on the methods of enrichment of Azolla with P showed that the best method was to broadcast twice 4.33 kg P (10 kg P₂O₅/ha) at 2-day intervals and to harvest Azolla 3 days after P application. Addition of P once or twice 2 weeks after the inoculation of P-enriched Azolla further increased the biomass production. Efficiency of P application was analyzed in terms of N gain in relation to the amount of P applied. This ratio in the P-enriched Azolla treatment was higher than the economically sound ratio -5-, and higher than or equal to that in the standard split application.     

英国Culm河河漫滩沉积物中磷素时空变化研究

河漫滩上沉积物的沉积伴随着与沉积物相结合的营养和污染物质的沉积。已有研究表明,河漫滩是与沉积物相结合的磷的沉积地。采用137Cs技术,并结合河漫滩沉积物中全磷(TP)含量的剖面信息,可以调查近年河漫滩沉积物中的TP含量,计算TP储量。本文根据英国Devon郡Culm河8个河漫滩采样环沉积物中的数据,重建了在过去40～50年内TP储量和含量的变化。结果表明,在Culm河河漫滩沉积物中,在1963～2000年间TP平均含量为0.60～1.96gkg-1,该值自河流上游向下游和自过去到现在有逐渐增加的趋势;在相同的河漫滩沉积物中,在相同的时期内TP储量为18.62～435.48gm-2,即0.49～11.46gm-2a-1,最大值出现在河流的中游。     

Validating the use of Cs measurements to estimate rates of soil redistribution by wind

Wind erosion has degraded over one-half billion hectares of land worldwide. ¹³⁷Cesium (¹³⁷Cs) has been used as a tracer to study long-term rates of soil redistribution by water and, to a lesser extent, by wind. Early studies assumed that the decline in ¹³⁷Cs activity for a potentially eroded soil relative to that for an uneroded soil was linearly proportional to soil loss. More recently, models have emerged that consider the effects of soil cultivation and the particle surface area-dependent partitioning of ¹³⁷Cs on soils. We investigated the partitioning of ¹³⁷Cs in wind-eroded sediments and with soil surface samples sieved into contiguous ranges of particle sizes. We also compared the ¹³⁷Cs activities and stratification of several adjacent soils with known wind erosion and deposition histories. Finally, we tested ¹³⁷Cs-based soil loss models with measured data from sites with documented histories. ¹³⁷Cs activities and mean particle diameters of aeolian samples agreed well with the ¹³⁷Cs activities and respective mean diameters of the sieved surface soil samples. Good agreement between model estimations and measured data indicated that ¹³⁷Cs models developed to estimate soil redistribution by water were also applicable to soil redistribution by wind provided that the models contained an appropriate particle size correction parameter.     

~(137)Cs在卧龙自然保护区土壤中的分布特征

对137Cs在卧龙自然保护区内不同生态系统土壤中的分布特征进行测量分析的结果表明:137Cs在耕地土壤中均匀分布,在其余6种非耕地土壤中呈明显的指数递减分布;非耕地土壤在0~10 cm土层内存在一个137Cs富集层,富集层以下137Cs含量有一个骤降的过程;137Cs在耕地土壤中的分布深度大于耕层厚度20 cm,在非耕地土壤中的分布深度在24 cm左右;137Cs的面积浓度在高山草甸土壤中最大,在适温灌丛土壤中最小,前者是后者的2.6倍。     

黄土丘陵区小流域淤地坝纪录的泥沙沉积过程研究

淤地坝是黄土丘陵区小流域水土流失治理的重要工程措施之一,在拦蓄泥沙的同时,也记载了小流域侵蚀产沙的历史变化过程及特征.该研究根据流域历史降雨资料,分析了黄土丘陵区关地沟小流域淤地坝1959～1987年泥沙沉积旋回变化及各旋回层泥沙中、小流域沟间地和沟谷地表层土体中放射性同位素137Cs含量,研究了小流域侵蚀产沙变化过程及泥沙主要来源.结果表明:该小流域在淤地坝建设初期,侵蚀产沙强度很大,其后产沙强度由强变弱,呈显著降低趋势,淤地坝内沉积泥沙的70%来源于沟间地;微小流域与较大流域在泥沙来源方面存在较大差异.     

基于137Cs示踪的丹江口市农用地土壤侵蚀与有机质流失分析

运用137Cs示踪技术探讨了丹江口市小流域不同土地利用方式的土壤侵蚀,并分析了137Cs含量与有机质和重金属含量之间的关系。结果表明:农用地土壤侵蚀速率从大到小依次为沟谷旱地>坡耕地>菜田>水田>草地>灌丛,耕作土的侵蚀强度多为中度和强度侵蚀,非耕作土则是微度和轻度侵蚀;不同土地利用方式对土壤有机质和重金属分布影响很大,有机质含量分布规律为草地>灌丛>菜田>水田>沟谷旱地>坡耕地;Pb与Ni含量为灌丛>草地>坡耕地>沟谷旱地>菜田>水田;Cr与Cu含量为灌丛>菜田>坡耕地>草地>沟谷旱地>水田;Zn含量为灌丛>菜田>草地>坡耕地>沟谷旱地>水田。对137Cs含量与土壤有机质、重金属含量进行回归分析的相关系数均在0.7以上,说明在景观简单的小流域,可以利用137Cs含量和数学模型预测土壤有机质和重金属的含量变化。     

Soil and phosphorus redistribution along a steep tea plantation in the Feitsui reservoir catchment of northern Taiwan

Feitsui reservoir, the major water supply of Taipei city, has shown declining water quality in recent years. The reservoir is located in an area famous for tea cultivation, and the question arises as to whether the hillside tea plantations have contributed to increased sediment and nutrient discharge into the reservoir. In this study, soil and phosphorus redistribution were examined along a steep tea plantation in the reservoir's catchment and the provenance of reservoir sediment was assessed. Fallout radionuclides were used as soil erosion/deposition tracers and as markers of sediment sources. Continuous fertilizer application has raised (inorganic) phosphorus levels in the studied tea plantation. The plantation's narrow bench terraces trap eroded material and slow down soil and nutrient translocation. Nevertheless, eroded soil and phosphorus have accumulated on a vegetated toeslope below the tea plantation. The reservoir sediment contained significant amounts of inorganic phosphorus and cesium-137, and application of a mixing model resulted in a surface soil contribution of approximately 30%. This points towards tea plantations as possible sediment and pollutant sources and underlines the necessity of soil conservation strategies, such as the maintenance of vegetated riparian buffer zones. However, other sources, such as landslide debris and urban wastewaters, cannot be entirely ruled out. Further research is needed to better characterize the catchment's soils and sediments and to improve sediment fingerprinting efforts. Potential point and non-point pollution sources need to be examined in detail to better understand how phosphorus enters the reservoir.     

侵蚀作用对黄土丘陵沟壑区有机碳迁移-沉积的影响

土壤有机碳(SOC)作为陆地碳库的重要组成部分,不仅对土壤肥力产生重要影响,而且在一定程度上影响着全球变暖趋势,为了深入探究土壤侵蚀与有机碳的关系,利用137 Cs核示踪法,以黄土丘陵沟壑区典型流域王茂沟坡耕地、林地、草地和梯田四种土地利用为研究对象,分析了不同坡面下土壤侵蚀对SOC迁移和沉积的影响规律.结果表明:与该...     

有机酸对液培玉米吸收137Cs和90Sr的影响

利用液培方法研究胡敏酸钠等有机酸盐作用下玉米幼苗对放射性核元素137Cs和90Sr的吸收速率。研究结果表明:利用有机酸盐可以降低玉米幼苗对放射性核元素的吸收速率。1低活度放射性核素水平下,对照(不加有机酸盐)的玉米幼苗中发现了97%放射性核元素137Cs,而高活度放射性核素水平中为61%;有机酸盐不同程度地降低了玉米幼苗中放射性核元素137Cs的量。在低活度水平中四苯硼钠降低137Cs的量最多, 玉米仅吸收12%,而酒石酸钾钠处理中玉米吸收量最高,为45.5%。对137Cs的吸收率,在胡敏酸钠处理中为23.9%, EDTA-Na处理中为41.3%;在高活度放射性核素水平中吸收率的顺序为四苯硼钠11%,胡敏酸钠26%,酒石酸钾钠28.7%,EDTA-Na 37%。2低活度水平下,对照中放射性核元素90Sr的56%被玉米幼苗吸收,而高活度水平中达61%。有机酸盐在低活度水平中降低放射性核元素90Sr的顺序为胡敏酸钠 23.9%,EDTA-Na 26%,酒石酸钾钠28%和四苯硼钠36%;在高活度水平中为四苯硼钠11%,EDTA-Na 24%,胡敏酸钠26%,酒石酸钾钠 31%。3低活度和高活度水平中,四苯硼钠和胡敏酸钠降低玉米幼苗体内的放射性核元素性质为最佳。4所有有机酸盐处理与对照之间的差异都达到极显著水平。