Seasonal trend of particulate PAHs at Gosan, a background site in Korea between 2001 and 2002 and major factors affecting their levels     

Ji Yi Lee  Yong Pyo Kim  Chang-Hee Kang  Young Sung Ghim   《Atmospheric Research》2006,82(3-4):680

The concentrations of particulate Polycyclic aromatic hydrocarbons (PAHs) were measured at Gosan, a background site in Korea for 1 year between November 2001 and November 2002. The total concentrations of 14 PAH compounds at Gosan were between 0.52 and 14.76 ng m^− 3 and about 3–15 times higher than those at other rural or remote sites in the world. Seasonal trend was observed for particulate PAHs concentrations at Gosan with higher levels during heating season due to increased fossil fuel usage and the movement of air parcels from Asian continent. Principal component factor analysis (PCF) for PAHs showed three factors; combination of coal combustion and vehicular emission, natural gas combustion, and unidentified one. However, PCF for the combined data of PAHs, inorganic ions, and elements revealed that the unidentified factor consists of crustal species, sea salts, and four PAH compounds. Thus, this factor is thought to be transport of crustal species with organics from combustion sources. The major variables which determine the sources of PAHs are the heating season and the movement of air parcels from Asian continent.  相似文献   

Comparison of satellite measurements of the low-latitude nighttime upper ionosphere with IRI     

Heejun Kim  Kyoungwook Min  Jaeheung Park  Jaejin Lee  Ensang Lee  Hyosub Kil  Vitaly P. Kim  Sunmie Park 《Journal of Atmospheric and Solar》2006,68(18):2107-2118

In this paper, we report the results of our comparison study between satellite measurements and the International Reference Ionosphere (IRI) model on the seasonal and longitudinal changes of the low-latitude nighttime topside ionosphere during the period of solar maximum from June 2000 to July 2001. Satellite measurements were made by KOMPSAT-1 and DMSP F15 at 685 km altitude and 840 km altitude, respectively. The results show that the IRI2001 model gives reasonable density estimations for the summer hemisphere and the March equinox at both altitudes. However, the observed wintertime densities are smaller than the predictions of the IRI2001 model, especially at a higher (840 km) altitude, manifesting strong hemispheric asymmetries. The observed electron temperatures generally reside between the two estimations of IRI2001, one based on the Aeros–ISIS data and the other based on Intercosmos, and the latter estimation better represents the observations. With more or less monotonic increase with latitude, the temperature profiles of the IRI2001 model do not predict the enhancement seen around 15° magnetic latitude of the winter hemisphere. Longitudinal variation, probably caused by the zonal winds, is seen in all seasons at both altitudes, while the IRI2001 model does not show a large variation. The observed density and temperature show significant changes according to the F10.7 values in the whole low-latitude region from 40°S to 40°N geomagnetic latitude. The effect is manifested as increases in the density and temperature, but not in the hemispheric asymmetry or in the longitudinal variation.  相似文献   

Cascadia边缘与天然气水合物共生沉积物中有机质碳、氮同位素组成及意义   总被引：1，自引：1，他引：1  

于晓果  李家彪  龚建明  陈建芳  金肖兵  Young-Joo Lee  李宏亮  徐杰 《中国科学D辑》2006,36(5):421-429

Hydrate Ridge南高点ODP204航次5个站位54个沉积物样品中有机碳C, N同位素组成及C/N比值表明沉积物中的有机质主要来自海洋. 对1245B孔的系统分析表明天然气水合物的发育改变了沉积物中有机碳和氮同位素的成岩演化轨迹, 水合物发育处δ¹⁵N值和C/N比值同时变低, 且δ¹³C值相对较重; 在水合物稳定带内δ¹⁵N值的亏损将近2‰. 水合物发育处沉积物中氮含量的增加和δ¹⁵N值的亏损, 推断可能与天然气水合物发育处沉积物中细菌(包括古细菌)的固氮作用有关. 沉积物中有机质中碳、氮同位素的分布与沉积环境的变化同步响应, 同时亦反映流体活动的变化.  相似文献   

现场室内两用大型直剪仪研制(I)：结构设计   总被引：9，自引：2，他引：9  

闵弘  刘小丽  魏进兵  邓建辉  谭国焕  李焯芬 《岩土力学》2006,27(1):168-172

直剪仪是测定岩土体抗剪强度参数应用最为普遍的一种试验仪器。从直剪仪的结构和大型直剪仪的研制两个方面对直剪仪的研究现状做了介绍，在此基础上，对新近研制的现场室内两用大型直剪仪的结构组成、工作机理及其特点进行了详细分析。该大型直剪仪与常规直剪仪相比，具有较大的优越性，其测试结果更加准确。适用范围广，测试精度高，可应用于现场和室内试验。  相似文献   

Ocean color reveals phase shift between marine plants and yellow substance   总被引：3，自引：0，他引：3  

Chuanmin Hu Zhongping Lee Muller-Karger  E. Carder  L. Walsh  J.J. 《Geoscience and Remote Sensing Letters, IEEE》2006,3(2):262-266

Daily high-resolution Sea-viewing Wide Field-of-view Sensor (SeaWiFS) images of the central North Atlantic Ocean (1998-2003) show that temporal changes in the absorption coefficient of colored dissolved organic matter (CDOM) or "yellow substance" follow changes in phytoplankton pigment absorption coefficient in time. CDOM peaks (between January and March) and troughs (late summer and fall) followed pigment peaks and troughs by approximately two and four weeks, respectively. This phase shift is additional strong evidence that CDOM in the marine environment is derived from phytoplankton degradation. The common assumption of linear covariation between chlorophyll and CDOM is a simplification even in this ocean gyre. Due to the temporal changes in CDOM, chlorophyll concentration estimated based on traditional remote sensing band-ratio algorithms may be overestimated by about 10% during the spring bloom and underestimated by a similar 10% during the fall. These observations are only possible through use of synoptic, precise, accurate, and frequent measurements afforded by space-based sensors because in situ technologies cannot provide the required sensitivity or synoptic coverage to observe these natural phenomena.  相似文献   

Analysis of the 16S-23S rDNA intergenic spacers (IGSs) of marine vibrios for species-specific signature DNA sequences   总被引：7，自引：0，他引：7  

Lee SK  Wang HZ  Law SH  Wu RS  Kong RY 《Marine pollution bulletin》2002,44(5):412-420

Vibrios are widespread in the marine environment and a few pathogenic species are known to be commonly associated with outbreaks of diarrheal diseases in humans due to the consumption of raw or improperly cooked seafood. However, there are also many Vibrio species which are potentially pathogenic to vertebrate and invertebrate aquatic animals, and of which little is known. In an attempt to develop rapid PCR detection methods for these latter class of vibrios, we have examined the 16S-23S intergenic spacers (IGSs) of 10 lesser-known Vibrio species and successfully developed species-specific primers for eight of them--Vibrio costicola, V. diazotrophicus, V. fluvialis, V. nigripulchritudo, V. proteolyticus, V. salmonicida, V. splendidus and V. tubiashii. The IGS amplicons were amplified using primers complementary to conserved regions of the 16S and 23S rRNA genes, and cloned into plasmid vectors and sequenced. Analysis of the IGS sequences showed that 37 ribosomal RNA (rrn) operons representing seven different IGS types have been cloned from the 10 vibrios. The three IGS types--IGS(0), IGS(IA) and IGS(Glu)--were the most prevalent forms detected. Multiple alignment of representative sequences of these three IGS types from different Vibrio species revealed several domains of high sequence variability, which were used to design species-specific primers for PCR. The specificity of the primers were evaluated using total DNA prepared from different Vibrio species and bacterial genera. The results showed that the PCR method can be used to reliably detect eight of the 10 Vibrio species in marine waters in this study.  相似文献   

The Reykjanes Ridge: structure and tectonics of a hot-spot-influenced, slow-spreading ridge, from multibeam bathymetry, gravity and magnetic investigations     

R.C Searle  J.A Keeton  R.B Owens  R.S White  R Mecklenburgh  B Parsons  S.M Lee   《Earth and Planetary Science Letters》1998,160(3-4):463-478

We report a comprehensive morphological, gravity and magnetic survey of the oblique- and slow-spreading Reykjanes Ridge near the Iceland mantle plume. The survey extends from 57.9°N to 62.1°N and from the spreading axis to between 30 km (3 Ma) and 100 km (10 Ma) off-axis; it includes 100 km of one arm of a diachronous ‘V-shaped' or ‘chevron' ridge. Observed isochrons are extremely linear and 28° oblique to the spreading normal with no significant offsets. Along-axis there are ubiquitous, en-echelon axial volcanic ridges (AVRs), sub-normal to the spreading direction, with average spacing of 14 km and overlap of about one third of their lengths. Relict AVRs occur off-axis, but are most obvious where there has been least axial faulting, suggesting that elsewhere they are rapidly eroded tectonically. AVRs maintain similar plan views but have reduced heights nearer Iceland. They are flanked by normal faults sub-parallel to the ridge axis, the innermost of which occur slightly closer to the axis towards Iceland, suggesting a gradual reduction of the effective lithospheric thickness there. Generally, the amplitude of faulting decreases towards Iceland. We interpret this pattern of AVRs and faults as the response of the lithosphere to oblique spreading, as suggested by theory and physical modelling. An axial, 10–15 km wide zone of high acoustic backscatter marks the most recent volcanic activity. The zone's width is independent of the presence of a median valley, so axial volcanism is not primarily delimited by median valley walls, but is probably controlled by the lateral distance that the oblique AVRs can propagate into off-axis lithosphere. The mantle Bouguer anomaly (MBA) exhibits little mid- to short-wavelength variation above a few milliGals, and along-axis variations are small compared with other parts of the Mid-Atlantic Ridge. Nevertheless, there are small axial deeps and MBA highs spaced some 130 km along-axis that may represent subdued third-order segment boundaries. They lack coherent off-axis traces and cannot be linked to Oligocene fracture zones on the ridge flanks. The surveyed chevron ridge is morphologically discontinuous, comprising several parallel bands of closely spaced, elevated blocks. These reflect the surrounding tectonic fabric but have higher fault scarps. There is no evidence for off-axis volcanism or greater abundance of seamounts on the chevron. Free-air gravity over it is greater than expected from the observed bathymetry, suggesting compensation via regional rather than pointwise isostasy. Most of the observed variation along the ridge can be ascribed to varying distance from the mantle plume, reflecting changes in mantle temperature and consequently in crustal thickness and lithospheric strength. However, a second-order variation is superimposed. In particular, between 59°30′N and 61°30′N there is a minimum of large-scale faulting and crustal magnetisation, maximum density of seamounts, and maximum axial free-air gravity high. To the north the scale of faulting increases slightly, seamounts are less common, and there is a relative axial free-air low. We interpret the 59°30′N to 61°30′N region as where the latest chevron ridge intersects the Reykjanes Ridge axis, and suggest that the morphological changes that culminate there reflect a local temperature high associated with a transient pulse of high plume output at its apex.  相似文献   

Modeling the Fate and Transport of Household Chemicals in Septic Systems     

Sijin Lee  Drew C. McAvoy  James Szydlik  Jerald L. Schnoor 《Ground water》1998,36(1):123-132

  相似文献   

Assessment of the geological and hydrogeological environment at a site of government-level conflict in Incheon, Korea     

J. E. Lee  K. K. Lee 《Environmental Geology》1998,35(4):278-286

 The natural environment of an environmental conflict site in Incheon, Korea was assessed with a focus on the hydrogeological environment. Residents had made claims against a company because of health problems, including skin tumors. More specifically, the residents suspected that their drinking groundwater had been contaminated by glass fibers which had caused the health problems. Air, soil, and groundwater samples were analyzed to estimate whether environmental pollution could have caused the problems claimed by the residents. No specific evidence was found from this study to support the groundwater contamination by glass fibers, but groundwater contamination by leaked fuel oils was confirmed in the course of evaluating the glass fiber problem. Received: 16 May 1997 · Accepted: 18 August 1997  相似文献   

On the polarization of Hα scattered by neutral hydrogen in active galactic nuclei     

Hee-Won Lee  & Jong-Hyeun Yun 《Monthly notices of the Royal Astronomical Society》1998,301(1):193-202

Raman scattering by atomic hydrogen converts the UV continuum around Lyβ into optical continuum around Hα, and the basic atomic physics has been discussed in several works on symbiotic stars. We propose that the same process may operate in active galactic nuclei (AGN) and calculate the linear polarization of the broad emission lines Raman-scattered by high-column neutral hydrogen component. The conversion efficiency of the Raman scattering process is discussed and the expected scattered flux is computed using the spectral energy distribution of an AGN given by a typical power law. The high-column H  i component in AGN is suggested by many observations, encompassing the radio through UV and X-ray ranges.   When neutral hydrogen component with a column density ∼10²² cm⁻² is present around the active nucleus, it is found that the scattered Hα is characterized by a very broad width ∼20 000 km s⁻¹ and that the strength of the polarized flux is comparable to that of the electron-scattered flux expected from a conventional unified model of narrow-line AGN. The width of the scattered flux is mainly determined by the column density of the neutral scatterers where the total scattering optical depth becomes of order unity. The asymmetry in the Raman scattering cross-section around Lyβ introduces red asymmetric polarized profiles around Hα. The effects of the blended Lyβ and O  vi 1034 doublet are also investigated.   We briefly discuss the spectropolarimetric observations performed on the Seyfert galaxy IRAS 110548-1131 and the narrow line radio galaxy Cyg A. Several predictions regarding the scattering by the high-column neutral hydrogen component in AGN are discussed.  相似文献