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紫色土坡地侵蚀产沙过程的~7Be法初探 总被引：1，自引：0，他引：1
利用环境放射性核素示踪技术研究土壤侵蚀是传统土壤侵蚀监测技术的重要补充手段。宇宙成因核素7Be具有半衰期短和在表土分布浅等特点,能够用于指示短时间尺度的坡面侵蚀堆积过程。采用7Be技术与泥沙颗粒分析相结合,定量判读了模拟降雨下紫色土坡面侵蚀过程演变。结果表明,对于20°坡面,7Be法指示的坡面侵蚀方式转折点与侵蚀泥沙颗粒变化得到的结果基本一致。7Be在表征侵蚀过程演变时具有独特的优势,可以将坡面片蚀发育过程随降雨时间的变化明显地识别出来。这对防治坡面侵蚀,特别是细沟侵蚀的发生具有重要意义。 相似文献
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三峡库区紫色土7Be剖面分布及季节变化 总被引：1，自引：0，他引：1
7Be是一种宇宙成因放射性核素.由于其来源明确、半衰期短、测试相对容易,可用于<1 a时间尺度内的环境过程示踪和定量研究.7Be在土壤中的剖面分布特征及其本底值是建立定量模型、估算侵蚀沉积速率和调查表土迁移过程的基础.对三峡库区为期1 a的无扰动紫色土7Be浓度的测定结果表明,7Be主要分布于质量深度0～20.0 kg/m2(0～1.5 cm)的表层土壤,其中0～3.0 kg/m2(0～2 mm)的最表层7Be比活度最高,向下随深度增加呈指数减少,20.0 kg/m2以下土层基本不含7Be.采样期间土壤7Be总面积活度介于172.4～328.6 Bq/m2,平均246.1 Bq/m2,并呈现春季最高,秋季最低;春夏高,秋冬低的季节性变化特征.植被截留可能是减少土壤7Be浓度的重要因素. 相似文献
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137 Cs is an artificial radionuclide with a half-life of 30.2 years,which was released into the environment as a byproduct of atmospheric testing of nuclear weapons during the period of 1950s to 1970s with a peak deposition in 1963.137 Cs fallout was strongly and rapidly adsorbed by soil particles when it deposited on the ground mostly with precipitation.Its following movements will associate with the adsorbed particles.137 Cs tracing technique has been widely used in soil erosion and sedimentation studies since 1980s.This paper introduces the basis of the technique and shows several case studies of assessment of soil erosion rates,investigation of sediment sources and dating of reservoir deposits by using the technique in the Loess Plateau and the Upper Yangtze River Basin. 相似文献
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Taihu Lake is a mutiple-function fresh water lake situated in the delta of Yangtze River. Nowadays, the serious pollution mainly created by industry and residents'' life has made the water quality of the lake decline continuously. Eutrophication is the main characteristic of the water pollution. The water pollution not only affect the several functions of the lake, but also cause the changes of the aquatic biological community.The pollution control strategies to be adopted include the treatment of the industrial waste water and residents'' life sewage, as well as the agricultural non-point polluting source. Ecological engineering is the useful measure for diminishing the nutrition salts in water. On the basis of pollution control, the ecological restoration methods include the transplanting of the emerged and/loading anchored aquatic plants at first and the restoration of the submerged plants in the next. 相似文献
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137Cs和210Pbex是湖泊沉积物断代常用的两种核素,沉积物中核素的深度分布,不但随核素的大气沉降量变化,也与流域环境变化和沉积后核素的再分布有关.我国环境复杂,人类活动强烈,137Cs和210Pbex深度分布的非理想曲线常见于我国一些湖泊的沉积物.本文简要介绍了湖泊沉积物137Cs和210Pbex深度分布理想曲线和断代基本原理,在参阅大量有关中国湖泊沉积物137Cs和210Pbex断代文献的基础上,讨论了137Cs和210Pbex非理想深度分布曲线的解泽和沉积物断代的几个常见问题.主要观点如下:1)我国湖泊沉积物不存在所谓的1974年和1986年蓄积峰;2)一些湖泊沉积出现的非单峰型137Cs深度分布曲线,可能与人类活动或湖流扰动湖泊底泥、流域侵蚀产沙环境变化和137Cs主要来源于冰川融水补给等因素有关;3)沉积物中的核素垂向运移,不改变剖面中1963年137Cs蓄积峰的位置,不影响其断代标志意义;4)流域环境突发事件引起的沉积剖面中的137Cs和210Pbex明显异常,是断代的可靠标志等.最后介绍了根据沉积剖面137Cs和210Pbex总量与本底值对比,求算沉积速率的核素质量平衡法. 相似文献
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侧扫声呐是海洋科学调查中常用的仪器设备,针对此类声学探测设备出台相关检测、检定等计量化的标准势在必行。本文介绍了侧扫声呐的工作原理和技术参数,针对侧扫声呐分辨能力和扫宽能力这两个性能指标,提出了一种评价方法。最后通过海上试验,对比分析了3种常用的侧扫声呐仪器的分辨能力和扫宽能力,为侧扫声呐系统的选用和引进提供参考。 相似文献
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新疆石河子近40a气候变化特征 总被引：7，自引：3，他引：4
以新疆石河子气象局1967～2006年年平均气温、降水量和无霜期观测资料为研究对象,运用线性拟合、3a滑动平均和Mann--Kendall方法进行趋势和突变分析。结果表明：近40a石河子年平均气温呈上升趋势,平均增温率达到0．51℃／10a,秋季增暖率较大,夏季和冬季增暖率较小;年降水量呈上升趋势,春季趋向于暖干,冬季趋向于暖湿;石河子气温突变时间是1988年,降水突变时间是1969年和1993年;受平均气温升高的影响,无霜期天数增加率为4．74d／10a,近40a共增加19d。 相似文献
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MingyiFENG XinbaoZHANG AnbangWEN XiubinHE 《国际泥沙研究》2004,19(1):60-65
Radionuclides are used as tracers of sediments in areas where no plot data or field monitoring data are not available. Caesium-137 can provide important information on both soil loss rates and sediment sources. The 137Cs technique is employed to assess soil erosion rates in forest and grass lands in the Upper Yangtze River Basin, China. The study area includes 6 forestlands and 4 grasslands in 8 counties and cities over the eastern part of the basin. The ^137Cs reference inventories ranged from 620.9 Bq m-2 to 2560.3 Bq m^-2. For the 6 forestlands, the average 137Cs inventory over a field ranges from 960.8 Bq m^-2 to 2560.3 Bq m^-2. The average erosion rate is estimated from the ^137Cs measurements between 0 to 588 t km^-2yr^-1. For the 4 grasslands, the average ^137Cs inventory ranges from 119.0 Bq m2 to 869.7 Bq m^-2. The average rate of erosion from grassland varies from 0 to 4435 t km^-2 yrl. Where the erosion was more severe, the ^137Cs inventory was lower. The results showed that there is no clear relationship between ^137Cs inventory, slope length and slope gradient on uncultivated land. The erosion rates for uncultivated land and cultivated land is compared. The result indicates that the erosion rates on uncultivated land is much lower than those on cultivated slopes and the severity of the soil erosion is closely related to vegetation cover. 相似文献