吉林省主要大豆种植区土壤重金属污染评价     

王冬艳  田艳芬  陆红 《吉林地质》2002,(Z1)

本文针对吉林省 5个主要大豆种植区重金属分析测试结果 ,选取国家颁布的《土壤环境质量标准》 (GB15 6 18- 95 )为评价标准 ,进行了重金属污染评价 ,其结果为 :只有敦化种植区铜、镍和桦甸种植区铜含量超标 ,并且为轻度污染。其它地区重金属污染指数 (Pi)小于1,即土壤未受到重金属污染  相似文献   

Notes on the marginal enrichment of Germanium in coal beds     

Ya. E. Yudovich   《International Journal of Coal Geology》2003,56(3-4):223-232

Germanium distribution in coal has long been a topic of interest. The enrichment of Ge near margins of coals, including the margins of partings within the coal, has been noted in many coals from numerous coalfields throughout the world. In this paper, a summary of literature on Ge geochemistry on the upper and lower margins of coal seams, with special emphasis on the literature of Russia, and the former Soviet Union, and Japan, is presented.  相似文献   

A very hydrous mantle under the western Pacific region: Implications for formation of marginal basins and style of Archean plate tectonics   总被引：7，自引：6，他引：1  

Tsuyoshi Komiya  Shigenori Maruyama 《Gondwana Research》2007,11(1-2):132

The western Pacific region has been refrigerated by the subducting cold oceanic plates since 450 Ma. However, the region is also characterized by the presence of many oceanic microplates less than 1300 km across, as well as active magmatism; the Philippine Sea plate is representative. We have compiled and examined petrochemical characters of drilled basalts of DSDP from the Philippine Sea plate, and conclude that the source mantle for oceanic basalts is rich in water ca. 0.2 wt.%, and is 50–60 °C lower than that for MORB. The extensive melting is due to the high water content in the source mantle.It is well known that some marginal basins apparently have greater depths than the major oceans. We calculated the age–depth correlation based on a model of transient half-space cooling at given parameters of temperatures of mantle and surface, 1280 and 0 °C, and the thermal diffusivity, 1 mm² s^− 1. The calculation shows the correlation of age-residual depth from a mid-oceanic ridge is 367 for the Philippine Sea, consistent with the bathymetric data. Moreover, the mid-oceanic ridge may be relatively deep because this region is underlain by the cooler mantle.Addition of water to the mantle peridotite lowers the solidus temperature and viscosity. Melting experiments of hydrous peridotite show that addition of 0.2 wt.% H₂O content lowers the solidus temperature by 150 °C. As a result, the mantle under the region may practically correspond to a ca. 90 °C hotter mantle than normal MORB-source mantle in terms of magmatism and rheology. Numerical simulation for a hotter mantle suggests that many small plates should be formed because of extensive heat release by active magmatism, consistent with many microplates in this region. The presence of many oceanic microplates may be analogous to Archean plate tectonics, characterized by a hotter mantle.  相似文献   

边缘海盆地的形成机制及其对中国东南地质研究的启示   总被引：11，自引：0，他引：11  

周祖翼  丁晓 《地球科学进展》1997,12(1):7-14

虽然有关边缘海的成因解释有“捕获机制”、弧后扩张(被动、主动)机制、陆内应力传播机制等,但迄今尚未有一种机制能统一解释所有边缘海的成因。边缘
海的成因不仅是经典的沟-弧-盆二维剖面问题,而应是一个包括平面图上大陆板块的变形在内的三维问题。边缘海的研究能给我国东部、特别是东南地区地质研究提供有益的启示,它包括:慎重鉴别古岛弧、对变质带、古洋壳及洋盆规模;充分注意小块体之间的碰撞,古转换断层在本区晚中生代岩浆活动、大陆增生过程中起重要作用;相关盆地内的沉积物记录着丰富的大陆碰撞、造山作用的信息。  相似文献   

Tectono sedimentary evolution of the Umm Ghaddah Formation (late Ediacaran-early Cambrian) in Jordan     

Belal S. Amireh  Mazen N. Amaireh  Abdulkader M. Abed 《Journal of Asian Earth Sciences》2008,33(3-4):194-218

The terrestrial Umm Ghaddah Formation of late Ediacaran-early Cambrian age was deposited in NE–SW elongated intracontinental rift system basins and sub-basins bounded by active listric half-graben faults. Basin fill consists of conglomerate facies association A, deposited in a fault-controlled transverse alluvial fan system that drained northwestward and graded laterally into sandstone facies association B, deposited by a braided river system flowing northeastward axial to the rift basin. The alluvial fan facies association was deposited by rock falls and non-cohesive debris flows of sediment gravity flow origin, and by sheetflood processes.The Umm Ghaddah Formation is dominated by a large-scale fining upward succession interpreted to reflect a gradual cessation of the Pan African Orogeny. Within this large-scale trend there are also minor fining and coarsening upward cycles that are attributed to repeated minor tectonic pulses and autocyclic shifting of the system.The distribution pattern of the Umm Ghaddah Formation and the underlying Ediacaran Sarmuj Conglomerates, Hiyala Volcaniclastics and Aheimir Volcanics in Jordan and adjacent countries in isolated extensional half-grabens and grabens formed during the extensional collapse phase of Arabia associated with the Najd Fault System seems to be unrelated to the present day Wadi Araba-Dead Sea transform fault system.  相似文献   

Rotifer abundance, biomass, and secondary production after the recovery of hydrologic connectivity between a river and two marginal lakes (São Paulo, Brazil)   总被引：1，自引：1，他引：0  

Silvia Maria Caglierani Casanova  Eliana Aparecida Panarelli  Raoul Henry   《Limnologica》2009,39(4):292-301

Rotifera density, biomass, and secondary production on two marginal lakes of Paranapanema River were compared after the recovery of hydrologic connectivity with the river (São Paulo State, Brazil). Daily samplings were performed in limnetic zone of both lakes during the rainy season immediately after lateral inflow of water and, in the dry period, six months after hydrologic connectivity recovery. In order to identify the factors that affect rotifer population dynamics, lake water level, volume, depth, temperature, transparency, dissolved oxygen, pH, alkalinity, conductivity, suspended solids, nutrients, and chlorophyll-a were determined. Variations of water physical and chemical factors that affect rotifer population were related to the lake-river degree of connection and to water level rising after drought. The water lateral inflow from the river resulted in an increase in lake water volume, depth, and transparency and a decrease in water pH, alkalinity, and suspended solids. The lake with the wider river connection, more frequent biota exchange, and larger amount of particulate and dissolved materials was richer and more diverse, while rotifer density, biomass, and productivity were lower in both periods studied. Density, biomass, and secondary production were higher in the lake with the smaller river connection and the higher physical and chemical stability. Our results show that the connectivity affects the limnological stability, associated to seasonality. Stable conditions, caused by low connectivity in dry periods, were related with high density, biomass and secondary production. Conversely, instability conditions in rainy periods were associated to elevated richness and diversity values, caused by exchange biota due to higher connectivity.  相似文献   

Long-term community changes on a high-latitude coral reef in the Greater St Lucia Wetland Park, South Africa   总被引：1，自引：0，他引：1  

Schleyer MH  Kruger A  Celliers L 《Marine pollution bulletin》2008,56(3):493-502

South African coral reefs are limited in size but, being marginal, provide a model for the study of many of the stresses to which these valuable systems are being subjected globally. Soft coral cover, comprising relatively few species, exceeds that of scleractinians over much of the reefs. The coral communities nevertheless attain a high biodiversity at this latitude on the East African coast. A long-term monitoring programme was initiated in 1993, entailing temperature logging and image analysis of high resolution photographs of fixed quadrats on representative reef. Sea temperatures rose by 0.15 degrees C p.a. at the site up to 2000 but have subsequently been decreasing by 0.07 degrees C p.a. Insignificant bleaching was encountered in the region during the 1998 El Nino Southern Oscillation (ENSO) event, unlike elsewhere in East Africa, but quantifiable bleaching occurred during an extended period of warming in 2000. Peak temperatures on the South African reefs thus appear to have attained the coral bleaching threshold. While this has resulted in relatively little bleaching thus far, the increased temperatures appear to have had a deleterious effect on coral recruitment success as other anthropogenic influences on the reefs are minimal. Recruitment success diminished remarkably up to 2004 but appears again to be improving. Throughout, the corals have also manifested changes in community structure, involving an increase in hard coral cover and reduction in that of soft corals, resulting in a 5.5% drop in overall coral cover. These "silent" effects of temperature increase do not appear to have been reported elsewhere in the literature.  相似文献   

松江铜锌矿床成矿规律及周边隐伏矿体的成矿预测     

迟祥 《矿产与地质》1999,13(4):204-207

松江矽卡岩型铜、锌、钨、钼多金属矿床是一个中等规模、隐伏的矽卡岩型矿床。矿床产于中生代花岗闪长岩和古生代钙铝质岩石的接触带中,矿体受构造和岩性控制。分析矿床的成矿地质条件,总结成矿规律,寻找隐伏矿、边缘矿、扩大区内的工业储量,延长矿山寿命,具有十分重要的意义。  相似文献   

Aggregatstabilitetsanalyse     

Henrik Madsen M. Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):70-78

Madsen, Henrik, 1975: Aggregatstabilitetsanalyse. Geografisk Tidsskrift 74: 70–78. København, juni 1, 1975.

A method to describe the stability and size distribution of soil aggregates by dry sifting. The profit and disadvantages of the method are discussed. A methematical adaption is given and further the influence of humus on the soil aggregates is discussed, as well as the possibility of the method for giving significant values in relation to soil erosion.  相似文献   

Greenhouse gas mitigation in Chinese agriculture: Distinguishing technical and economic potentials     

《Global Environmental Change》2014

China is now the world's biggest annual emitter of greenhouse gases with 7467 million tons (Mt) carbon dioxide equivalent (CO₂e) in 2005, with agriculture accounting for 11% of this total. As elsewhere, agricultural emissions mitigation policy in China faces a range of challenges due to the biophysical complexity and heterogeneity of farming systems, as well as other socioeconomic barriers. Existing research has contributed to improving our understanding of the technical potential of mitigation measures in this sector (i.e. what works). But for policy purposes it is important to convert these measures into a feasible economic potential, which provides a perspective on whether agricultural emissions reduction (measures) are low cost relative to mitigation measures and overall potential offered by other sectors of the economy. We develop a bottom-up marginal abatement cost curve (MACC) representing the cost of mitigation measures applicable in addition to business-as-usual agricultural practices. The MACC results demonstrate that while the sector offers a maximum technical potential of 402 MtCO₂e in 2020, a reduction of 135 MtCO₂e is potentially available at zero or negative cost (i.e. a cost saving), and 176 MtCO₂e (approximately 44% of the total) can be abated at a cost below a threshold carbon price ≤¥ 100 (approximately €12) per tCO₂e. Our findings highlight the relative cost effectiveness of nitrogen fertilizer and manure best management practices, and animal breeding practices. We outline the assumptions underlying MACC construction and discuss some scientific, socioeconomic and institutional barriers to realizing the indicated levels of mitigation.  相似文献