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71.
Xinbin FENG Shaofeng WANG Guangle QIU Yamin HOU Shunlin TANG 《中国地球化学学报》2006,25(B08):243-244
Guizhou is located in the Circum-Pacific Global Mercuriferous Belt, and mercury concentrations in soil in this area are enriched. In-situ total gaseous mercury (TGM) exchange fluxes between air and soil surface were intensively measured at four sampling sites in Guiyang from 21 May to 16 June, 2003, and five sites in the Lanmuchang mercury mining area in December 2002 and May 2003, respectively. The in-situ Hg flux measurement was conducted with a dynamic flux chamber (DFC) of quartz. Overall, net emissions were obtained from all sampling sites. Soil mercury concentration and solar radiation have been proved to be the two most important parameters to control mercury emissions from soil. Meanwhile, rain events can enhance mercury emission rate significantly. 相似文献
72.
Georg Schettler Jens Mingram Jörg F. W. Negendank Liu Jiaqi 《Journal of Paleolimnology》2006,35(2):271-288
Palaeovariations of the atmospheric 210Pb flux in Northeast China (Long Gang area, Jilin province), quantified by high resolution 210Pb measurements on seasonally laminated sediments of Lake Sihailongwan are presented on decadal scale. The mean flux of unsupported
210Pb between 1790 and 1970 for the centre of the lake basin is 517 Bq m−2 yr−1 with maximum deviations between −23% and +27% of this value. Flux rates above this average were found between 1783 and 1813,
around 1836, and between 1860 and 1901. The mean 210Pbexc flux rates derived were clearly lower around 1821, 1908, 1930, and 1953. The 210Pbexc flux reached its minimum of 344 Bq m−2 yr−1 during the period 1977–1982. The atmospheric flux of unsupported 210Pb is correlated with the precipitation frequency during the summer monsoon and shows coinciding variability with geochemical
proxies that document the groundwater inflow into the lake. Al2O3-rich dust of remote provenance scavenged by wet-deposition in the rainy season is the major carrier of the atmospheric 210Pbexc flux. 相似文献
73.
74.
Georg Schettler Qiang Liu Jens Mingram Jörg F. W. Negendank 《Journal of Paleolimnology》2006,35(2):239-270
The varved sediments of the dimictic Lake Sihailongwan (Long Gang mountain area, Jilin Province, Northeast China) represent
a palaeoclimatic archive which documents the local precipitation frequency during the summer monsoon, and variations in the
aeolian flux of dust with their remote sources in the arid and semi-arid regions of inner Asia. Based on a detailed discussion
of sediment genesis in Lake SHL, dust flux rates and palaeohydrological conditions were reconstructed on a decadal scale over
the past 220 years. The aeolian influx by dry and wet deposition was quantified and characterised in its chemical composition.
Photosynthetic production in the lake is positively correlated with the inflow of nutrient-rich groundwater. The groundwater
discharge largely reflects the strength of the summer monsoon. Net accumulation rates for biogenic silica were determined
for annually laminated sediments from the centre of the U-shaped lake basin based on sediment data. In a Si-balance model
of the modern lake, the depositional flux of biogenic silica could be independently quantified on the base of hydrochemical
monitoring data. Comparison of the both estimates allowed to asses the focussing of the particle flux in the lake. Though
water retention in Lake SHL is rather high (ca. 30 years), changes in the hydrological conditions are sensitively recorded
in the sediments because (i) nutrient-rich groundwater discharges into the productive zone of the lake, (ii) a substantial
proportion of the total dissolved Si-inventory of the mixed lake (ca. 30%) is annually consumed by diatom growth, and (3)
sediment accumulation is substantially focussed towards the flat bottom of the lake basin. The bulk siliciclastic sediment
fraction (ca. 75 wt.%) largely originates from influx of dust of remote provenance. In sediment thin-sections, the dry-deposited
dust fraction is microscopically identifiable as seasonal silt layer. Aeolian input by wet-deposition shows a distinctly higher
variability than the influx of dust by dry-deposition. As diatom production, wet-deposition of dust is positively correlated
with the rainfall during the summer monsoon. The inferred positive correlation between rainfall and dust flux during the summer
monsoon implies that dust deposition is determined by the out-wash efficiency of mineral particles for a permanent high atmospheric
dust concentration over Northeast China in the last 220 years. 相似文献
75.
Chemical methods are generally chosen to monitor soil pollution but magnetic measurements proved to yield additional information at low cost and less time consumption. In this investigation, the novel use of rapid and non-destructive magnetic measurements to characterize Br levels in Xuzhou (China) urban roadside soils was reported. X-ray fluorescence spectrometry (XRF) was used to quantify Br in the soil samples. Data from 21 roadside soil samples confirm Br contamination, with a mean level of 4.36 mg kg−1 and a range of 2.4–8.7 mg kg−1. These values are higher than that of unpolluted soils in Xuzhou that averages 1.1 mg kg−1. Hierarchical clustering analysis shows Br in Xuzhou roadside soils is mainly from road traffic. Clear correlations between Br levels and simple magnetic parameters [mass specific susceptibility (χ
LF), susceptibility of anhysteretic remanent magnetization (χ
ARM), saturation isothermal remanence (SIRM)] are observed. The present study shows that these three magnetic parameters can be used as a proxy for Br levels in Xuzhou urban roadside soils. 相似文献
76.
Rui CHEN Xiaoli WANG Yonggang ZHANG Xueqi FU 《中国地球化学学报》2006,25(B08):128-129
The use of membranes is a widely employed, versatile, and effective separation process. One of the limiting aspects in applying microfiltration (MF) for wastewater treatment is that of problems with membrane fouling and consequent flux reduction. Membrane fouling occurs by the irreversible deposition of retained particles, colloids, macromolecules, salts, etc. at the membrane surface and/or inside the membrane. The predominant fouling mechanisms observed with MF membranes are classified as three categories: the build-up of a cake layer on the membrane surface, blocking of membrane pores, and adsorption of fouling material on the membrane surface or in the pore walls. Although many techniques have been developed to overcome fouling, studies on membrane cleaning still seem to be insufficient for practical membrane filtration systems. Current membrane cleaning technologies include hydraulic, chemical, and mechanical methods. Ultrasound (US) has been widely used as a method of cleaning materials because of the cavitation phenomenon. In this study, US cleaning technique was applied to removing the fouling of polyvinglidenefluoride (PVDF) MF membrane, which was used to treat yeast cell and isolated soybean protein (ISP) solution, respectively. The US employed 40 kHz frequency and the output power of 1.43-2.85 W/cm^2. The evolution of the cleaning effect is followed by the measurements of the flux recovery rate (FRstat) and the cleaning time cycle. Results showed that the membrane property, which was fouled by yeast cell solution, could be recovered by water cleaning with US irradiation. And the cleaning time with the same FRstat decreased with the increase of US intensity. 相似文献
77.
对中国大陆科学钻探主孔的岩心进行了声发射测量,确定了301~1531m深度的最大主应力。并与钻孔崩落法(深度1269~1655m)测量结果进行了对比,结果表明,声发射测量所得测值基本上落在钻孔崩落法测值的趋势线上,两种方法所得结果一致,说明测量结果可信。测量结果表明科学钻探主孔地应力大小随深度增加,在浅部301m最大主应力为13.4MPa,在深部1655m为55.2MPa。随深度的增加率为0.0279MPa/m。最大主应力方向为N54°±3.3°E,且方向不随深度变化。 相似文献
78.
安正泽 《中国地质灾害与防治学报》2005,16(1):69-71
文章通过对贵州省大方县以公鸡山地裂隙实地调查,认为地裂隙的形成主要与公鸡山一带地下采煤有关。即采煤虚脱,沿先存构造断裂拉张而成。同时叙述了地裂缝特征及危害,并提出防灾减灾措施。 相似文献
79.
80.