Nitrogen in Chinese coals

Three hundred and six coal samples were taken from the main coal mines of twenty-six provinces, autonomous regions, and municipalities of China. The method of Kjeldahl-Gunning Analysis was used to measure the nitrogen contents in the samples. Nitrogen in coals is principally of organic nature. A weak positive correlation between coal rank and nitrogen content is inferred in the study. The distribution of nitrogen in each geological age, coal-cumulating area and province＇s coals was studied. The contents of nitrogen in Chinese coals show approximately a normal distribution, and 90% of the values range from 0.52% to 1.41%, the average nitrogen content in Chinese coals is designated as the arithmetic mean, 0.98%.     

Heavy metal concentrations and Pb isotopic composition in urban and suburban aerosols of Hong Kong and Guangzhou, South China-Evidence of the long-range transport of air contaminants

Rapid urbanization and industrialization in South China has placed a great strain on the environment and human health. In the present study, the total suspended particulate matter （TSP） in the urban and suburban areas of Hong Kong and Guangzhou, the two largest urban centres in South China, was sampled from December 2003 to January 2005. The samples were analyzed for their concentrations of major elements （Al, Fe, Mg and Mn） and trace metals （Cd, Cr, Cu, Pb, V and Zn）, and for Pb isotopic composition. Elevated concentrations of metals, especially Cd, Pb, V and Zn, were observed in the urban and suburban areas of Guangzhou, showing significant atmospheric trace element pollution. Distinct seasonal patterns were observed in the heavy metal concentrations of aerosols in Hong Kong, with higher metal concentrations during the winter monsoon period, and lower concentrations during summer time. The seasonal variations in metal concentrations of the aerosols of Guangzhou were less distinct, suggesting the dominance of local sources of pollution around the city. The Pb isotopic composition in the aerosols of Hong Kong had higher ^206Pb/^207Pb and ^208Pb/^207Pb ratios in winter, showing the influence of Pb from the northern inland areas of China and the Pearl River Delta （PRD） region, and lower ^206Pb/^207Pb and ^208Pb/^207Pb ratios in summer, indicating the influence of Pb from the South Asian region and from marine sources.     

Sediment records of persistent organic pollutants （POPs） in relation to regional economic development： A comparison study in both Pearl River Delta and Yangtze River Delta, China

Persistent organic pollutants （POPs） are semi-volatile chemicals that are toxic to wildlife and human. Typical POPs include most organochlorine pesticides （OCPs）, polycyclic aromatic hydrocarbons （PAHs）, polychlorobiphenyls （PCBs）, polybrominated biphenyl ethers （PBDEs）, etc. Most POPs are hydrophobic, capable of accumulating and existing for a long time in the sediments. Well preserved, laminated sediment layers hence can serve as archives for POP pollution history in the sediment pool. Rapid economic growth has taken place since the early 1980s in most parts of China, of which the Yangtze River Delta, the Pearl River Delta and the Pan-Bohai Bay took the lead. Along with the brilliant regional economic development, the environmental quality has been severely deteriorated. For a more sustainable economic and social development, it is of vital need to understand the relationship between regional economic development and environmental pollution.     

Visible and near infrared reflectance spectroscopy for measuring soil heavy metal content as a quick method

Conventional methods for investigating soil heavy metal contamination based on raster sampling and chemical analysis are time consuming and relatively expensive. Reflectance spectroscopy within the visible-near-infrared （VNIR） region is known for being rapid, convenient, and accurate. Due to low abundance, heavy metals in soils cannot exhibit their inherently spectral features. The objective of this study were （1） to examine the possibility of reflectance spectra as a rapid method to assess Ni, Cr, Cu, Hg, Zn, As, Pb, and Cd in soils, and （2） to explore the mechanism by which to predict spectrally featureless heavy metals. Two research areas located in the south （120 samples） and north （61 samples） of Nanjing City were researched. Reflectance spectra of the samples were recorded on a Perkin-Elmer Lambda 900 spectrophotometer. Partial least-square regression （PLSR） approach was used to develop calibration equations between the spectral data and measured values for heavy metals. The prediction results of the two areas were consistent. Except for Cd all the other elements could be successfully predicted using the reflectance spectra. The prediction accuracy for Ni, Cr, and Cu was highest, while that for Hg and Cd was lowest. In order to further explore the physicochemical mechanism behind the relations between reflectance spectra and heavy metals, one more principal component analysis （PCA） was done for nine elements （eight heavy metals and Fe）. The results of PCA for the both areas were also consistent. Loading plot of factors 1 and 2 from the results of PCA showed that Ni, Cr and Cu, the prediction accuracy of which was highest, were clustered together with Fe. For the other elements that were less correlated with Fe, their prediction accuracy was also lower than that of the three elements. Fe is spectrally active and can exhibit its absorption features. Therefore, the inter-correlation between heavy metals and spectrally active total Fe is the major mechanism by which to predict spectrally featureless trace metals. This study for the two areas showed the potential of reflectance spectra to predict microelements in soils.     

Characteristics and genesis of hematite in Chinese loess and paleosol sequences： Mineral genetic restriction for magnetic susceptibility as paleoclimate proxy and iron geochemistry

Hematite is an important iron oxide mineral in loess-paleosol sequences in central China. Investigation of the mineralogical characteristics, genetic mechanism and relationship of hematite with other iron oxides and Fe-bearing minerals will help understand the geochemical process before and after eolian deposit, paleocliamte significance of magnetic susceptibility and reconstruct paleoclimate in central China. So, hematite and related minerals of the loess and paleosol units from Chinese Loess Plateau were investigated using optical microscope, X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, and high-resolution transmission microscopy （HRTEM）. The results show that there are five genetic types of hematite in loess-paleosol sequences of central China： （1） weathering of Fe-bearing silicate minerals, for instance, chlorite, will release iron that is precipitated as aggregates of hematite nano-crystals on mineral surfaces; （2） hematite combined with eolian magnetite grains that resulted from partial oxidation of magnetite, even though the partial oxidation may occur in the original area; （3） phase transformation from eolian goethite to hematite; （4） hematite formed on the edge and surface of maghemite because of dissolution and hematite recrystallization; and （5） eolian detrial hematite. The hematite formed from chemical weathering of Fe-bearing silicates with nanoporous texture because of dehydration from iron hydroxide is the most important genetic mechanism. It is proposed that the fact that hematite was formed from chemical weathering of Fe-bearing silicates is a main reason for the redness in paleosol units. However, too intense pedogenesis and high amounts of precipitation will promote oxidation of eolian magnetite and maghemite dissolution, which may result in the decreasing of magnetic susceptibility.     

Petrological, geochemical and chronological constraints for the tectonic setting of the Dongco ophiolite in Tibet

The Dongco ophiolite occurred in the middle-western segment of the Bangong-Nujiang suture zone. The thickness of the ophiolite suite is more than 5 km, which is composed, from bottom to top, of the mantle peridotite, mafic-ultramafic cumulates, basic sills (dykes) and basic lava and tectoni- cally emplaced in Jurassic strata (Mugagongru Group). The Dongco cumulates consist of dunite- troctolite-olivine-gabbro, being a part of DTG series of mafic-ultramafic cumulates. The basic lavas are characterized by being rich in alkali (Na2O K2O), TiO2, P2O5 and a LREE-rich type pattern dip- ping right with [La/Yb]=6.94―16.6 as well as a trace elements spider-diagram with normal anomaly of Th, Nb, Ta, Hf. Therefore, the Dongco basic lavas belong to ocean-island basalt (OIB) and dis- tinctly differ from mid-ocean ridge basalt (MORB) and island-arc basalt (IAB) formed in the plate convergence margin. The basic lavas have higher 87Sr/86Sr (0.704363―0.705007), lower 143Nd/144Nd (0.512708―0.512887) and εNd(t ) from 2.7― 5.8, indicating that they derive from a two-components mixing mantle source of depleted mantle (DM) and enriched mantle (EMI). From above it is ready to see that the Dongco ophiolite forms in oceanic island (OIB) where the mantle source is replaced by a large amount of enriched material, therefore it distinctly differs from these ophiolites formed in island-arc and mid-oecan ridge. Newly obtained SHRIMP U-Pb dating for zircon of the cumulate troctolite is 132 ± 3 Ma and whole-rock dating of ~(39)Ar/~(40)Ar for the basalt is 173.4 ± 2.7 Ma and 140.9 ± 2.8 Ma, indicating that the Dongco ophiolite formed at Early Cretaceous and the middle-western segment of the Bangong-Nujiang oceanic basin was still in the developing and evolving period at Early Cretaceous.     

Geochemistry and Sr-Nd isotope characteristics of tonalites in Zêtang,Tibet:New evidence for intra-Tethyan subduction

Tonalites from the island arc rock assemblage in the Zêtang segment of the Yarlung Zangbo suture zone were analyzed for major,trace elements (including REE) and Sr-Nd isotope. The experimental data demonstrate that the tonalites have the adakite-like characteristics,including high SiO2 (58%―63%),Al2O3 (18.4%―22.4%),Sr (810×10 6―940×10 6),Sr/Y (77―106),low HREE (Y=9×10 6―11×10 6,Yb= 1×10 6―1.3×10 6),with LREE enrichment and faint Eu positive anomaly. ISr (0.70421―0.70487) is rela-tively low whereas 143Nd/144Nd (0.512896―0.512929) and εNd(t) values ( 6.7― 7.3) are high. These fea-tures suggest that Zêtang tonalites were formed by the partial melting of subducted oceanic crust,with involvement of a small amount of oceanic sediments. The identification of Zêtang adakites,derived from slab melting,presents new evidence for the intra-Tethyan subduction and the previous sugges-tion about the existence of intra-oceanic island arc within Tethys.     

EFFECTS OF RIVER ICE ON STAGE-DISCHARGE RELATIONSHIPS——A CASE STUDY OF THE YELLOW RIVER

Using field observations at four gauging stations along the Inner Mongolia Reach of the Yellow River in China, this paper explores effects of the ice on the hydraulics of this river reach for four different conditions, namely: under open channel flow, during ice-running period, the ice-covered period, and the river break-up period. The rating curves were found to be well recognized under open channel situations, but were sometimes poorly defined and extremely variable under ice conditions. The results also show that the water level is insensitive to flowing ice prior to freeze-up. However, significant, but hardly surprising, variations were observed during ice-covered conditions. The rating curves for both the ice covered condition and river ice breakup period are developed and some related hydraulic issues are examined. Additionally, the impacts of the ice accumulation and associated riverbed deformation during ice period on the rating curves are discussed.     

Design and application of the method for isolating magnetotactic bacteria

A simple apparatus was designed to effectively isolate magnetotactic bacteria from soils or sediments based on their magnetotaxis. Through a series of processes including sample incubation, MTB harvesting, isolation, purification and identification, several strains of bacteria were isolated from the samples successfully. By Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray Analysis (EDXA), these bacteria were certificated to be magnetotactic bacteria. The phylogenetic relationship between the isolated magnetic strains and some known magnetotactic bacteria was inferred by the construction of phylogenetic tree based on 16SrDNA sequences. This apparatus has been proven to have the advantages of being inexpensive, simple to assemble, easy to perform and highly efficient to isolate novel magnetotactic bacteria. The research indicated that the combined approach of harvesting MTB by home-made apparatus and the method of plate colony isolation could purify and isolate magnetotactic bacteria effectively.