科尔沁沙地土地利用与耕作方式对土壤风蚀的影响   总被引：2，自引：1，他引：2  

张华  季媛  苗苗 《干旱区地理》2006,29(6):861-866

土壤风蚀造成的直接生态后果是土地资源的退化。在春播前两次沙尘暴事件中,对科尔沁沙地几种具有代表性的土地类型的土壤风蚀量及土壤特性进行了野外测定、分析,结果表明:(1)在同一沙尘暴天气下,由于土地利用和耕作方式的不同,土壤风蚀量存在着差异,新垦农地和翻耕农地的风蚀量显著高于未垦草地、免耕农地和麻黄地;免耕农地则与未垦草地的风蚀量相差不大,风蚀危害较轻;麻黄地几乎不受风蚀侵害。新垦农地、翻耕农地、免耕农地、未垦草地、麻黄地两次观测的土壤风蚀量平均值依次为24.59、15.60、2.26、1.46和0.22 g/h.cm2。(2)基于土壤特性计算的土壤退化指数结果表明,新垦农地和翻耕农地发生了较为严重的退化。  相似文献   

Lake-Level Fluctuations and Small-Scale Vegetation Patterns During the Late Glacial in The Netherlands     

Johanna A. A. Bos  Sjoerd J. P. Bohncke  C. Roel Janssen 《Journal of Paleolimnology》2006,35(2):211-238

Late glacial changes in the vegetation were studied in and around a former lake on the southeastern side of a coversand ridge near Milheeze (southern Netherlands). Analyses of microfossils and macroremains and AMS ¹⁴C dating were performed on four sediment cores along a transect from sand ridge to the lake centre. Small-scale vegetation patterns and lake-level fluctuations were reconstructed in detail based on the information provided by the transect. For the first time in The Netherlands, cores along a transect within one lake were used to reconstruct the amplitude of late glacial lake-level fluctuations. Near Milheeze, a small and shallow lake was formed during the Bølling. The large increase in the water level during the Bølling and early Allerød, and the transition to more eutrophic conditions at the start of the Allerød, were probably related to the disappearance of permafrost. During the Allerød, open birch and pine woodlands developed in the area. In the lake, organic deposits accumulated, and the lake size and depth fluctuated. At the start of the Younger Dryas, higher lake water levels were recorded and woodlands became more open as a result of both a drop in the temperature and an increase in the effective precipitation. During the late Younger Dryas the lake water level dropped as the climate became drier and temperatures slightly increased. Accumulation of organic deposits in the lake ceased at the end of the Younger Dryas, which was caused by a drop in the water level in combination with the hydroseral succession process within the lake itself. The climatic signal reflected in the late glacial flora and lake-level fluctuations agree well with other published data from The Netherlands.  相似文献   

Biological and Geochemical Record of Anthropogenic Impacts in Recent Sediments from Lake Pupuke, Auckland City, New Zealand     

Paul Augustinus  Michael Reid  Sofia Andersson  Yanbin Deng  Mark Horrocks 《Journal of Paleolimnology》2006,35(4):789-805

Frozen sediment cores from Lake Pupuke in Auckland City, New Zealand, contain a high resolution decadal to annual scale record of changing lake paleoenvironments and geochemistry that reflects changing landuse and hydrology in the catchment over the past c. 190 years. A reliable chronology is available from AMS ¹⁴C and ²¹⁰Pb dating of the sediments, with the timing of the older part of the record supported by the first appearance of pollen of introduced Pinus and Plantago lanceolata associated with European settlement of Auckland in the early 1840s. Diatom stratigraphy, sediment elemental and carbon isotope geochemistry reflect changes in sediment sources and lake conditions commensurate with European development of the Lake Pupuke catchment, in particular enhanced algal productivity controlled by the influx of nutrients after c. 1920 AD. Attempts to prevent nuisance algal blooms in 1933, 1934 and 1939 using CuSO₄ addition produced Cu spikes in the sediment that allowed confirmation of the accuracy of the ²¹⁰Pb chronology. Hence, the elemental and isotopic composition of the Lake Pupuke sediments reflect the timing of significant anthropogenic activities, rather than climatic variations, that have occurred within the watershed over the past c. 190 years. The comparison of records of land use change in the catchment with the multi-proxy record of changes in the sediments usually allowed unambiguous identification of the signatures of change and their causes.  相似文献   

Vertical distribution and water solubility of phosphorus and heavy metals in sediments of the St. Lucie Estuary, South Florida, USA   总被引：2，自引：0，他引：2  

Z. L. He  M. Zhang  P. J. Stoffella  X. E. Yang 《Environmental Geology》2006,50(2):250-260

Accumulation and distribution of heavy metals and phosphorus in sediments impact water quality. There has been an increasing concern regarding fish health in the St. Lucie Estuary, which is related to increased inputs of nutrients and metals in recent decades. To investigate vertical changes of contaminants (P, Cd, Cr, Co, Cu, Ni, Pb, Zn, and Mn) in sediments of the St. Lucie Estuary in South Florida, 117 layer samples from six of the 210 to 420 cm depth cores were analyzed for their total and water-soluble P and heavy metals, clay, total Fe, Al, K, Ca, Mg, Na, and pH. Principal component analysis (PCA) was used in two sets of analytical data (total and water-soluble contaminant concentrations) to document changes of contaminants in each core of sediments. The PCA of total contaminants and minerals resulted in two factors (principal components). The first and second factors accounted for 61.7 and 17.2 % of the total variation in all variables, and contrast indicators associated with contaminants of P, Cd, Co, Cr, Ni, Pb, Zn, and Mn and accumulation of Fe and Al oxides, respectively. The first factor could be used for overall assessment of P and heavy metal contamination, and was higher in the upper 45–90 cm than the lower depths of each core. The concentrations of P and heavy metals in the surface layers of sediments significantly increased, as compared with those in the sediments deeper than 45–90 cm. The PCA of water-soluble contaminants developed two factors. The second factor (Cu–P) was higher in the upper than the lower depths of the sediment, whereas the highest score of the first factor (Cd–Co–Cr–Ni–Pb–Zn–Mn) occurred below 100 cm. The water-soluble Cu and P concentrations were mainly dependent on their total concentrations in the sediments, whereas the water-soluble Cd, Co, Cr, Ni, Pb, Zn, and Mn concentrations were mainly controlled by pH.  相似文献   

Vertical variation of phosphorus forms in surface sediments from Wuli Bay, Taihu Lake, China   总被引：1，自引：0，他引：1  

李军  刘丛强  王仕禄  朱兆洲  周志华  肖化云 《中国地球化学学报》2006,25(3):279-284

1IntroductionPhosphorus,an essential nutrient for the primaryproductivity in freshwater systems,is an important fac-tor controlling lacustrine eutrophication.Although ex-ternal input of phosphorus has been assumed as the vi-tal responsibility for the eutrophication of lakes(ZhuJun et al.,2005),the remobilization of phosphorus insediments has a distinct influence on it as well(Bostr m et al.,1982).The concentrations of totalphosphorus(Ptotal)in the sediments are often related tothe trophic st…  相似文献   

地震属性分析中水平切片的应用   总被引：6，自引：0，他引：6  

国洪伟  陈勃  刘和芝  刘伟  张秀丽 《物探化探计算技术》2005,27(1):10-15

利用地震数据体中含有的丰富地质信息,可以有效地进行储层预测。层拉平水平切片地层学解释方法是先将地震剖面目的层段做层拉平处理,然后对切片顺地层层面追踪,勾绘出各种地层现象,并以地层学的观点加以解释。该方法在吉林探区扶新南部地区的应用中,对于识别河道的展布趋势取得了较好的效果,而且发现了多期叠置的扇型沉积体。另外,还可指导反演数据体的解释,做到对岩性体从定性到定量的描述。  相似文献   

东准噶尔纸房地区晚石炭世巴塔玛依内山组陆相火山-沉积体系特征   总被引：24，自引：0，他引：24  

朱志新  李少贞  李嵩龄 《新疆地质》2005,23(1):14-18

东准噶尔巴塔玛依内山组是典型陆相火山．沉积体系(盆地)，主体由基性及中酸性火山熔岩组成，火山碎屑岩及火山碎屑沉积岩较少，通过对纸房地区晚石炭世巴塔玛依内山组陆相火山岩的岩石化学、地球化学特征进行系统研究，认为它属于造山期后固结初期，新陆壳裂谷向高原火山岩演化的同岩浆源、同沉积盆地、同火山作用的钙碱系列双峰式火山岩．  相似文献   

环境样品中痕量元素的化学形态分析Ⅱ．砷汞镉锡铅硒铬的形态分析   总被引：2，自引：6，他引：2  

何红蓼  倪哲明李冰 杨红霞 《岩矿测试》2005,24(2):118-128

环境中元素的生物有效性和毒性依赖于其存在的化学形态。文章依据文献的有关报道介绍砷、汞、镉、锡、铅、硒和铬在环境中的分布、毒性及它们在环境样品如水、土壤、沉积物和生物体中的形态分析方法,包括分析物的保存、提取、分离和检测。引用文献120篇。  相似文献   

超声与振荡提取沉积物中松散结合态磷的比较     

罗俊凌罗爱芹  张月琴 《岩矿测试》2005,24(3):193-196

用超声技术提取沉积物样品中松散结合态磷,并与振荡提取结果进行比较。结果表明,超声提取结果与振荡提取结果大致相当。超声提取耗时短,操作简单易行,测试结果精密度为3.8%(RSD,n=7),可以替代振荡方法提取沉积物中的松散结合态磷。  相似文献   

葛洲坝水利枢纽运行后泥沙冲淤变化分析   总被引：2，自引：1，他引：2       下载免费PDF全文

戴会超  何文社  袁杰  曹叔尤 《水科学进展》2005,16(5):691-695

对葛洲坝水利枢纽及其运行情况和河段特性进行了介绍。分析认为葛洲坝水利枢纽运行前后的入库水沙特性基本一致。探讨了库区冲淤变化特点、淤积量及其分布,冲淤过程及达到冲淤平衡的时间。对坝下游河床的冲淤过程、冲淤量、达到冲淤平衡的时间以及河床粗化,河底高程历年变化及同流量水位降低的原因、降低量及变化过程进行了分析总结。研究结果可为进一步探讨三峡水利枢纽与葛洲坝水利枢纽联合调度运用后水库泥沙淤积变化规律提供参考。  相似文献