Spatial distribution of Cd and Cu in soils in Shenyang Zhangshi Irrigation Area （SZIA）, China

Heavy metal contamination of soils, derived from sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides, and so on, has been of wide concern in the last several decades. The Shenyang Zhangshi Irrigation Area （SZIA） in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years. This study investigated the spatial distribution and temporal variation of soil cadmium （Cd） and copper （Cu） contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd and Cu in soils was analyzed and then the spatial distribution and temporal variation of Cd and Cu in soils were modeled using Kriging methods. The results show that long-term sewage irrigation had caused serious Cd and Cu contamination in soils. The mean and the maximum of soil Cd are markedly higher than the levels in second grade standard soil （LSGSS） in China, and the maximum of soil Cu is close to the LSGSS in China in 2004 and is more than the LSGSS in China in 1990. The contamination magnitude of soil Cd and the soil extent of Cd con- tamination had evidently increased since sewage irrigation ceased in 1992. The contamination magnitude of soil Cu and the soil extent of Cu contamination had evidently increased in topsoil, but obviously decresed in subsoil. The soil contamination of Cd and Cu was mainly related to Cd and Cu reactivation of contaminated sediments in Shenyang Xi River and the import of Cd and Cu during irrigation. The eluviation of Cd and Cu in contaminated topsoil with rainfall and irrigation water was another factor of temporal-spatial variability of Cd and Cu contamination in soils.     

Aerosol oxalate and its implication to haze pollution in Shanghai, China

A total of 238 samples of PM2.5and TSP were analyzed to study the characteristics,sources,and formation pathways of aerosol oxalate in Shanghai in four seasons of 2007.The concentrations of oxalate were0.07–0.41 lg/m3in PM2.5and 0.10–0.48 lg/m3in TSP,respectively.Oxalate displayed a seasonal variation of autumn[summer[winter[spring in both PM2.5and TSP and was dominantly present in PM2.5in all samples.Correlation between oxalate and K?and high ratio of oxalate/K?suggested that biomass burning was a secondary source of aerosol oxalate in Shanghai,in addition to urban VOCs sources(vehicular and industrial emissions),especially in autumn.Secondary formation accounted for the majority of aerosol oxalate in Shanghai,which was supported by the high correlation of oxalate with nssSO42-,K?and NO3-,proceeding from different mechanisms.Relatively high ambient RH together with high cloud cover was found benefiting the secondary formation of aerosol oxalate.The in-cloud process(aqueous-phase oxidation)was proposed to be likely the major formation pathway of aerosol oxalate in Shanghai,which was supported by the high correlation of oxalate with nss-SO42-and K?,dominant residence of oxalate in droplet mode and result of favorable meteorological condition analysis.High correlation of oxalate and NO3-reflected the OH radical involved oxidation chemistry of the two species in the atmosphere and also suggested that gas-particle surface reactions and the evaporation–condensation process were both possible secondary formation pathways of aerosol oxalate in coarser particle mode([1.0 lm).As a major water-soluble organic compound in aerosols,concentration of oxalate showed a distinct negative correlation to the atmospheric visibility,which implied that aerosol organic compounds could play an important role in haze pollution as well as in air quality in Shanghai.     

Cellular distribution of arsenic and other elements in hyperaccumulator<Emphasis Type="Italic">Pteris nervosa</Emphasis> and their relations to arsenic accumulation

Synchrotron radiation X-ray fluorescence spectroscopy (SRXRF) was used to study the cellular distributions of arsenic and other elements in root, petiole, pinna of a newly discovered arsenic hyperaccumulator, Pteris nervosa. It was shown that there was a trend in P nervosa to transport arsenic from cortex tissue to vascular tissue in root, and keep arsenic in vascular during transportation in petiole, and transport arsenic from vascular tissue to adaxial cortex tissues in midrib of pinnae. More arsenic was accumulated in mesophyll than in epidermis in pinnae. The distributions of some elements, such as K, Ca, Mn, Fe, Cu, Zn, in petiole, midrib and pinna were similar to that of arsenic, indicating that those cations might cooperate with arsenic in those transportation processes; whereas the distributions of CI and Br in pinna were the reverse of that of arsenic, indicating that those anions might compete with arsenic in pinna of P. nervosa.     

Significance and dynamics of drip water responding to rainfall in four caves of Guizhou, China

In rainy season, NaCI is adopted to trace sources of cave drip water, time scales of drip water responding to precipitation, and processes of water dynamics in four caves of Pearl watershed in Guizhou, China (Liangfeng cave in Libo, Qixing cave in Duyun, Jiangjun cave in Anshun and Xiniu cave in Zhenning). Because of the variety of karst cave surroundings, interconnections of water transporting ways, water dynamics processes etc., time scales of drip-water in four caves responding to rainfall is 0——40 d. According to the characteristics of water transport in cave roof, pathways of water movement, types of water head etc., drip water of four caves can be divided into five hydrodynamics types. The differences of time scales, and ways of water-soil and water-rock interaction during water transporting in cave roof make it difficult to correctly measure speleothem record and trace material sources. In addition, there exist great differences in water dynamic conditions among the four caves. So the interpretation of the paleoenvironment records of speleothem must be supported by the understanding of hydrodynamics conditions of different drip sites. Based on the data got from drip sites in four caves, drip conductivity accords with precipitation, which indicates that element contents in speleothem formed by drip water record the change of karst paleoenvironment. But results of multi-points study are needed to guarantee the correctness of interpretation.     

A study on responses of soil erosion and sediment yield to closing cultivation on sloping land in a small catchment using ^137Cs technique in the Rolling Loess Plateau, China

By comparison of volumes and ^137Cs Contents of the deposited sediments before and after 1993,changes of specific sediment yields and relative sediment contributions from the gully area and from the inter gully area after closing cultivation on the later area on a small catchment of Zhaojia Gully,in the Rolling Loess Plateau,are analyzed in this paper.Closing cultivation in a large scale has not resulted in decrease but increase of specific sediment yield and the relative sediment contribution of the inter-gully area,and in increase of the sediment yield and the contribution of the gully area,for a short term.The mean specific sediment yield of 29650 t km^-2a^-1 of 1994-1996 in the catchment was 2.2 times the average value of 13413 t km^-2 a^-1 for a long term.The specific sediment yield of the inter-gully area decreased from the 14335t km^-2a^-1 in 1994 to 7034 t km^-2 a^-1 in 1995 and 3517 t km^-1a^-1 in 1996 which was much greater than the value of 21118 t km^-2 a^-1 before 1993.The relative sediment contribution from the inter-gully area decreased form 23% in 1994 to 15% in 1995 and 6% in 1996,while the contribution from the gully area increased form 77% in 1994 to 85% in 1995 and 94% in 1996.It is suggested that compacting of ploughed soils resulted in increasing of the erosion resistance but in decreasing of the precipitation infiltration,therefore,the soil erosion reduced but the runoff amount increased on the inter-gully area.Increase of delivering runoff from the inter-gully area to the gully area should result in activeness of gully erosion and mass movements,consequently,in increase of the total sediment yield from the catchment.     

Microstructural evolution in the surface of Ti-10V-2Fe-3Al alloy by solution treatments

By solution treatments in vacuum and in air,the surface region of Ti-10V-2Fe-3Al exhibits different microstructures from the interior region of the alloy.When solution treated in vacuum,the microstructure of the specimen is composed of dominant β phase and a few of α " martensite in surface region,with a large amount of α" martensite and a little of β phase in interior.When solution treated in air,the specimen is characterized by dominant surficial a phase and interior β phase.In addition,the lattice parameter evolutions of a and β phases were observed in the surface region of the specimens by solution treatment in air.The mechanism for the surface effects is discussed in light of the structural stability and phase evolution in Ti-10V-2Fe-3Al alloy with solution treatments.     

Control of coupling among three major factors for formation of high-efficiency gas reservoir——A case study on the oolitic beach gas reservoir in Feixianguan Formation in the northeast Sichuan Basin

Through a case study of the high-efficiency gas reservoir in Feixianguan Formation in the northeast Sichuan Basin, quantitative and semi-quantitative analyses of key elements such as hydrocarbon generation, migration and accumulation, and reservoir evolution as well as their interplay in the critical moment of reservoir formation controlled by the energy field were carried out, by means of numerical modeling of the energy field. It was found that the climax time for Permian hydrocarbon generation was Late Triassic-Early Jurassic and accumulation of oil and gas has resulted in large-scale paleoreservoirs in paleostructural traps in Feixianguan Formation, a process facilitated by fractures connecting the sources. The paleoreservoirs have been turned into high-efficiency gas kitchens due to pyrolysis, which resulted from deep burial at a temperature of 170―210 ℃ as induced by tremendously thick sedimentation in the foreland basin of Daba Mountain in Late Jurassic-Cretaceous period. Meanwhile, abundant acid gas like H2S produced from thermo-chemical sulfate reduction (TSR) at high temperatures leads to extensive dissolution of dolostone in the paleoreservoirs, which may in turn result in modification of the reservoirs and preservation of the reservoir rock porosity. The present distribution of gas reservoirs was ultimately determined in the processes of adjustment, cooling and decompression of the paleoreservoirs resulting from intense deformation in the front of Daba Mountain during the Himalayan orogeny.     

Chronological record of the Early Mesozoic underplating in the northern margin of North China—U-Pb chronometry of zircons in the Late Mesozoic andesite from Western Liaoning

Cathodoluminescence spectroscopic analysis of zircons in the uppermost sanukites of the early Cretaceous Yixian Forma- tion in Western Liaoning reveals zoning structures of the zircons in the volcanic rocks. LA-ICP-MS chronometry shows that the central part of the zircons is remnant zircon with a U-Pb dating of 254 Ma,which is consistent with the age of the Early Mesozoic underplating granulites,and that the periphery is zircon crystallizing out of the host magma with a U-Pb dating of 116 Ma,which is highly consistent with the Ar-Ar dating of the host volcanic rocks.Compositions of the clinopyroxenes xenocrystals in the sanukites are similar to those of the clinopyroxenes in the underplating granulites,indicating that the granulites accreted to the lower crust in the Early Mesozoic have been reformed and disrupted by the upwelling diapers of the asthenosphere and taken part in formation of the sanukites in the Late Mesozoic.     

Tooth loss and alveolar remodeling in Sinosaurus triassicus (Dinosauria: Theropoda) from the lower jurassic strata of the Lufeng Basin, China

Pathological or traumatic loss of teeth often results in the resorption and remodeling of the affected alveoli in mammals. However, instances of alveolar remodeling in reptiles are rare. A remodeled alveolus in the maxilla of the Chinese theropod Sinosaurus (Lower Jurassic Lower Lufeng Formation) is the first confirmed example of such dental pathology in a dinosaur. Given the known relationship between feeding behavior and tooth damage in theropods (teeth with spalled enamel, tooth crowns embedded in bone) and the absence of dentary, maxillary, and premaxillary osteomyelitis, traumatic loss of a tooth is most likely the cause of alveolar remodeling. Based on the extent of remodeling, the injury and subsequent tooth loss were non-fatal in this individual.     

Measurement of ethylene and methane production in a temperate forest soil using inhibition of acetylene and carbon monoxide

We studied in the laboratory the effects of acetylene （C2H2） concentrations on the accumulation and consumption of ethylene and methane in a temperate pine forest soil, and in situ ethylene and methane production and flush effects of nitrogen sources on both productions in the pine forest stand （Pinus sylvestris L.）. The addition of C2H2 at concentrations more than 50 Pa C2H2 in the headspace caused a more than 95% reduction in rates of ethylene and methane consumption in forest soil compared to those with no C2H2. Furthermore, addition of acetylene within a range of 50 to 10, 000 Pa C2H2 induced a similar rate of methane accumulation in forest soil. Hence, it can be concluded that presence of more than 50 Pa C2H2 in the headspace is an effective method to measure methane production in forest soil. The addition of C2H2 at concentrations more than 50 Pa C2H2 induced an increasing concentration of ethylene in the headspace （P≤0.05）, indicating the reduction of acetylene to ethylene in forest soil. Using inhibition of 0.5 kPa C2H2 in combination with 5 kPa carbon monoxide that inhibits the reduction of acetylene in a short term, it was observed that there was a larger in situ methane production rate （218±26 μg C m^-2 h^-1（μg C per square meter per hour, the same below）） than in situ ethylene production rate （92±6 μg C m^-2 h^-1） in the pine forest soil. The addition of nitrogen sources such as urea, urea plus a nitrification inhibitor dicyandiamide, and potassium nitrate, could induce a 5-fold greater increase in rates of in situ ethylene and methane production compared to those in the control, particularly in the latter （P≤0.05）. The results can promote in situ measurement of ethylene and methane production in forest soils at different sites.     

Plasticity of functional epithelial polarity

The fundamental characteristics that allow vectorial transport across an epithelial cell are the differential sorting and insertion of transport proteins either in the apical or the basolateral plasma membrane, and the preferential association of endocytosis and exocytosis with one or the other pole of the cell. Asymmetrical cellular structure and function, being manifestations of terminal differentiation, might be expected to be predetermined and invariant. Here we show that the polarity of transepithelial H+ transport, endocytosis and exocytosis in kidney can be reversed by environmental stimuli. The HCO3- secreting cell in the cortical collecting tubule is found to be an intercalated cell possessing a Cl-/HCO3- exchanger in the apical membrane and proton pumps in endocytic vesicles that fuse with the basolateral membrane; the H+-secreting cell in the medullary collecting tubule has these transport functions on the opposite membranes. Further, the HCO3- -secreting cell can be induced to change its functional polarity to that of the H+-secreting cell by acid-loading the animal.     

Auxin transport inhibitors block PIN1 cycling and vesicle trafficking

Polar transport of the phytohormone auxin mediates various processes in plant growth and development, such as apical dominance, tropisms, vascular patterning and axis formation. This view is based largely on the effects of polar auxin transport inhibitors. These compounds disrupt auxin efflux from the cell but their mode of action is unknown. It is thought that polar auxin flux is caused by the asymmetric distribution of efflux carriers acting at the plasma membrane. The polar localization of efflux carrier candidate PIN1 supports this model. Here we show that the seemingly static localization of PIN1 results from rapid actin-dependent cycling between the plasma membrane and endosomal compartments. Auxin transport inhibitors block PIN1 cycling and inhibit trafficking of membrane proteins that are unrelated to auxin transport. Our data suggest that PIN1 cycling is of central importance for auxin transport and that auxin transport inhibitors affect efflux by generally interfering with membrane-trafficking processes. In support of our conclusion, the vesicle-trafficking inhibitor brefeldin A mimics physiological effects of auxin transport inhibitors.     

A chloride channel widely expressed in epithelial and non-epithelial cells.

Chloride channels have several functions, including the regulation of cell volume, stabilizing membrane potential, signal transduction and transepithelial transport. The plasma membrane Cl- channels already cloned belong to different structural classes: ligand-gated channels, voltage-gated channels, and possibly transporters of the ATP-binding-cassette type (if the cystic fibrosis transmembrane regulator is a Cl- channel). The importance of chloride channels is illustrated by the phenotypes that can result from their malfunction: cystic fibrosis, in which transepithelial transport is impaired, and myotonia, in which ClC-1, the principal skeletal muscle Cl- channel, is defective. Here we report the properties of ClC-2, a new member of the voltage-gated Cl- channel family. Its sequence is approximately 50% identical to either the Torpedo electroplax Cl- channel, ClC-0 (ref. 8), or the rat muscle Cl- channel, ClC-1 (ref. 9). Isolated initially from rat heart and brain, it is also expressed in pancreas, lung and liver, for example, and in pure cell lines of fibroblastic, neuronal, and epithelial origin, including tissues and cells affected by cystic fibrosis. Expression in Xenopus oocytes induces Cl- currents that activate slowly upon hyperpolarization and display a linear instantaneous current-voltage relationship. The conductivity sequence is Cl- greater than or equal to Br- greater than I-. The presence of ClC-2 in such different cell types contrasts with the highly specialized expression of ClC-1 (ref. 9) and also with the cloned cation channels, and suggests that its function is important for most cells.     

高等植物铝胁迫研究新进展

简单概述了近几年对植物铝毒及耐铝机制的研究进展。Al^3＋通过与细胞骨架的作用、引发细胞壁反应、诱导细胞死亡机制对植物产生毒害作用。植物可以改变细胞电位影响Al^3＋吸收、改善质膜透性和活性氧代谢、加强根系对铝吸收及向上运输的排斥来抵御铝毒害。     

Efflux-dependent auxin gradients establish the apical-basal axis of Arabidopsis

Axis formation occurs in plants, as in animals, during early embryogenesis. However, the underlying mechanism is not known. Here we show that the first manifestation of the apical-basal axis in plants, the asymmetric division of the zygote, produces a basal cell that transports and an apical cell that responds to the signalling molecule auxin. This apical-basal auxin activity gradient triggers the specification of apical embryo structures and is actively maintained by a novel component of auxin efflux, PIN7, which is located apically in the basal cell. Later, the developmentally regulated reversal of PIN7 and onset of PIN1 polar localization reorganize the auxin gradient for specification of the basal root pole. An analysis of pin quadruple mutants identifies PIN-dependent transport as an essential part of the mechanism for embryo axis formation. Our results indicate how the establishment of cell polarity, polar auxin efflux and local auxin response result in apical-basal axis formation of the embryo, and thus determine the axiality of the adult plant.     

An efflux transporter of silicon in rice

Silicon is an important nutrient for the optimal growth and sustainable production of rice. Rice accumulates up to 10% silicon in the shoot, and this high accumulation is required to protect the plant from multiple abiotic and biotic stresses. A gene, Lsi1, that encodes a silicon influx transporter has been identified in rice. Here we describe a previously uncharacterized gene, low silicon rice 2 (Lsi2), which has no similarity to Lsi1. This gene is constitutively expressed in the roots. The protein encoded by this gene is localized, like Lsi1, on the plasma membrane of cells in both the exodermis and the endodermis, but in contrast to Lsi1, which is localized on the distal side, Lsi2 is localized on the proximal side of the same cells. Expression of Lsi2 in Xenopus oocytes did not result in influx transport activity for silicon, but preloading of the oocytes with silicon resulted in a release of silicon, indicating that Lsi2 is a silicon efflux transporter. The identification of this silicon transporter revealed a unique mechanism of nutrient transport in plants: having an influx transporter on one side and an efflux transporter on the other side of the cell to permit the effective transcellular transport of the nutrients.     

An H+-ATPase in opposite plasma membrane domains in kidney epithelial cell subpopulations

Vectorial solute transport by epithelia requires the polarized insertion of transport proteins into apical or basolateral plasmalemmal domains. In the specialized intercalated cells of the kidney collecting duct, the selective placement of an apical plasma membrane proton-pumping ATPase (H+-ATPase) and of a basolateral membrane anion-exchange protein results in transepithelial proton secretion. It is currently believed that amino-acid sequences of membrane proteins contain critical signalling regions involved in sorting these proteins to specific membrane domains. Recently, it was proposed that intercalated cells can reverse their direction of proton secretion under different acid-base conditions by redirecting proton pumps from apical to basolateral membranes, and anion exchangers from basolateral to apical membranes. But others have found that antibodies raised against the red cell anion-exchange protein (Band 3) only labelled intercalated cells at the basolateral plasma membrane, providing evidence against the model of polarity reversal. In this report, we have examined directly the distribution of proton pumps in kidney intercalated cells using specific polyclonal antibodies against subunits of a bovine kidney medullary H+-ATPase. We find that some cortical collecting duct intercalated cells have apical plasma membrane proton pumps, whereas others have basolateral pumps. This is the first direct demonstration of neighbouring epithelial cells maintaining opposite polarities of a transport protein. Thus, either subtle structural differences exist between proton pumps located at opposite poles of the cell, or factors other than protein sequence determine the polarity of H+-ATPase insertion.     

Basolateral KCl co-transport in a NaCl-absorbing epithelium

In NaCl-absorbing epithelia such as proximal renal tubule, small intestine and gallbladder, Na+-dependent Cl- entry across the luminal membrane is an electroneutral transport process that has been attributed to Na-Cl symport, Na-K-Cl symport, or a double (Na-H, Cl-HCO3) antiport. At the basolateral (antiluminal) membrane, Na+ extrusion can be attributed to the Na+-K+ pump, and Cl- transport could be explained in principle by electrodiffusion since the intracellular Cl- activity is higher than predicted for equilibrium distribution. However, in Necturus gallbladder, as in other epithelia, the electrodiffusional Cl- permeability of the membrane (PCl) is too low to account for the transepithelial Cl- transport rate. Because K+ is at a higher chemical potential in the cell than in the extracellular fluid, and because serosal Cl- substitutions have only small effects on membrane potential, the hypothesis of carrier-mediated electroneutral KCl co-transport was proposed. The experiments reported here were designed to test this hypothesis in Necturus gallbladder epithelium. Intracellular Cl- and K+ activities (aCli, aKi) were measured with ion-sensitive intracellular microelectrodes before, during and after ionic substitutions of the serosal (basolateral) bathing medium. The results demonstrate a Na+-independent basolateral membrane KCl symport.     

大肠杆菌耐药机制中激活外排泵和减少摄入量的研究进展

概述了大肠杆菌中激活外排泵和减少摄入量这两个重要的耐药机制和克服它们的新策略,主要包括近年来在理解外排泵系统的物理结构、功能和调控子中的进步和有利于开发以外排泵为靶位的药物研究进展。     

Neodymium cations Nd3+ were transported to the interior of Euglena gracilis 277

Euglena gracilis 277, a unicellular green alga, demonstrated remarkable ability to transport Nd3+ to the cell compartments. For a given amount of Nd3+ and cells, the results of ICP-AES indicated that the cellular uptake of Nd3+ was independent of Nd3+ concentration in the bulk solution. The average uptake of Nd3+ per cell (mNd) is proportional to a parameter ζ -- the ratio of neodymium content to the cell counts of the system. A novel approach for probing cellular neodymium by tetraiodotetra chlorofluorescein (I4TCF) has been devised. Data derived from the cryosections of I4TCF-Nd3+ stained cells and EDAX of the fast freezing ultrathin cryosections indicate that Nd3+ is distributed over the cell compartments. Chloroplasts are the major compartments as the residence of Nd3+ in the alga. The transport should be against a concentration gradient of Nd3+ on the order of five, even higher. It is proposed that a calcium ion channel would play an important role in the Nd3+ transportation.