Using 137Cs tracing technique to estimate wind erosion rates in the typical steppe region,northern Mongolian Plateau

Wind erosion is one of the major factors of land degradation in the typical steppe region, northern Mongolian Plateau. Using ^137Cs tracing technique, we estimated the wind erosion rates of different pastures and abandoned farmland at Bayannur and Karakorum in Mongolia. The pastures and cutting grassland at Bayannur were slightly eroded by wind, with the rates of 64.58-169.07 t·km^-2.a^-1. The abandoned farmland in Karakorum, however, was strongly eroded by wind, with annual surface soil loss of 4.05 mm. a^-1, and wind erosion rates up to 6723.06 t· km^-2. a^-1. The total loss of surface soil due to wind erosion has been 17.4 cm since the cultivation of the steppe land in the 1960s. The wind ero- sion rate at the abandoned farmland was much higher than that at the typical steppe sites, showing that the cultivation led to serious wind erosion in the typical steppe region, northern Mongolian Plateau. By contrast, traditional livestock grazing resulted in less disturbance to the surface soil, and did not induce to devastating wind erosion, which plays an important role in maintaining the stability of the steppe ecosystem in the northern Mongolian Plateau.     

Preliminary results of the study on wind erosion in the Qinghai-Tibetan Plateau using137Cs technique

The worldwide fallout of caesium-137 (¹³⁷Cs) associated with the nuclear weapon tests during the 1950s and 1960s has provided a valuable man-made tracer for studies of soil erosion and sediment delivery. But relatively few researchers have used it to estimate wind erosion. In this note, the¹³⁷Cs technique is introduced into the studies of wind erosion and its modern processes in the Qinghai-Tibetan Plateau. Two¹³⁷Cs reference inventories of 982.11 and 2 376.04 Bq · m⁻² were established preminarily, distributed in the south and middle-north parts of the studied area respectively. By analyzing the patterns of¹³⁷Cs depth profiles from sampling sites, the aeolian processes of erosion and deposition in nearly 40 years have been revealed, i.e. the shrub coppice dunes (S1) and semi-fixed dunefields (S3) experienced the alternation of erosion and deposition, while the grasslands (S4, S6 and S7) and dry farmlands (S5) suffered erosion only. By using¹³⁷Cs model, the average wind erosion rates for shrub coppice dune (S1), semi-fixed dune fields (S3), dry farmlands (S5) and grasslands (S4, S6 and S7) were estimated to be 84.14, 69.43, 30.68 and 21.84 t · ha¹ · a⁻¹ respectively, averaging 47.59 t · ha⁻¹ · a⁻¹ for the whole plateau, which can be regarded as of the medium erosion standard. These results derived from Cs for the first time have significant implications for the further research of wind erosion and desertification control in the Qinghai-Tibetan Plateau.     

Distribution characteristics of ^137Cs in wind-eroded soil profile and its use in estimating wind erosion modulus

~~Distribution characteristics of ~(137)Cs in wind-eroded soil profile and its use in estimating wind erosion modulus1.Tamura, T, Jacobs, D. G, Structural implications in cesium sorp-tion, Health Physics, 1960, 6(2): 391-398. 2.Rogowshi, A. S., Tamura, T, Movement of 137Cs by runoff, erosion and infiltration on the alluvial captina silt loam, Health Physics, 1965, 11(12): 1333-3340. 3.Owens, P. N., Walling, D. E., He, Q. P., The behaviour of bomb-derived caesium-137 fallout in …     

Characteristics of 137Cs deposition in steppe area

Soil wind erosion in the semiarid steppe area was studied using the ¹³⁷Cs tracing technique. Comparisons of ¹³⁷Cs deposition characteristics between different soil profiles indicated that slight aeolian activities occurred on sandy grasslands and semi-fixed dunes with erosion/deposition rates of less than 0.108 cm/a, whereas they were intense on semi-shifting dunes with erosion/deposition rates of higher than 1.35 cm/a.     

Export and remineralization of POM in the Southern Ocean and the South China Sea estimated from 210Po/210Pb disequilibria

Disequilibria between ^210Po and ^210Pb in the upper water and their potential applications as a proxy of particle export and remineralization were examined in the Southern Ocean （station IV3） and the South China Sea （NS44）. ^210po was deficit in surface waters but excessive relative to ^210Pb in subsurface waters. Good positive correlation between ^210Po and particulate organic carbon （POC） indicated deficits and excess of ^210Po resulted from particulate organic matter （POM） export and remJneralization respectively, which was also supported by the decreased δ^13C and increased δ^15N downwards as a result of particle remineralization. On the basis of ^210Po/^210Pb box-model, POC export flux out of the surface waters were 1.2 mmol C. m^-2. d^-1 and 2.3 mmol C. m^-2. d^-1 for station NS44 and IV3, respectively. In the subsurface waters, remineralization fluxes of ^210Po were 0.062 Bq. m^-2.d^-1 and 0.566 Bq.m^-2.d^-1 for station NS44 and IV3 along with the recycle efficiency of 52±26% and 119±52%, respectively. Remineralized fluxes of POM derived from ^210Po and exported POC were 0.6 mmol C.m^-2.d^-1 and 2.7 mmol C. m^-2. d^-1 for NS44 and IV3. This study suggested that ^210Po was a powerful tracer of particle export and remineralization.     

A novel Pd/silicalite-1 composite membrane for hydrogen separation

A novel Pd/silicalite-1 composite membrane supported on the macroporous tubular stainless steel substrate was successfully fabricated by electroless plating at 303 K. The structure, morphology and gaseous permeability of the membrane were detected by X-ray diffractiometry （XRD）, scanning electron microscopy （SEM） and single-gas permeation test, respectively. Results confirm the formation of a thin, smooth, and continuous Pd/silicalite-1 composite membrane. The obtained composite membrane shows a high H2 permeance of 1.15×10^-6 mol. m^-2. s^-1. Pa^-1 with moderate H2 selectivity of 250 for H2/N2 at 773 K, at 0.1 MPa pressure drop, suggesting the potential application for H2 separation.     

Pollen flux and vertical dispersion in coniferous and deciduous broadleaved mixed forest in the Changbai Mountains

The pollen flux in coniferous and deciduous broadleaved mixed forest in the Changbai Mountains is presented in one year's experiments. The results indicate that arboreal pollen percentages are more than 65% and pollen flux is higher than 5000 grain·cm-2·a-1,while less than 2% and lower than 1000 grain·cm-2·a-1 for shrubby pollen,and less than 20% and lower than 3000 grain·cm-1·a-1 for herbaceous pollen for most samples at different heights. The pollen assemblages are similar to those in the samples under 8 m height where Pinus and Ouercus are dominant and followed by the few non-local pollen types,and Fraxinus percentages are high with a few non-local pollen types at 16 m to 32 m height as well as non-local pollen clearly increased at 40 m height. Comparisons between pollen assemblages and vegetation composition suggest that similarities are higher for pollen trap samples than for surface moss samples.     

The climate influence of anthropogenic land-use changes on near-surface wind energy potential in China

There is considerable interest in the potential impact of climate change on wind energy in China. The climate change of near-surface wind energy potential in China under the background of global warming and its association with anthropogenic land-use changes are investigated by calculating the difference in surface wind speeds between the NCEP/NCAR reanalysis data and the observations since the reanalysis dataset contains the influence of large-scale climate changes due to greenhouse gases, it is less sensitive to regional surface processes associated with land types. The surface wind data in this study consist of long-term observations from 604 Chinese Roution Meteorological Stations and the NCEP/NCAR reanalysis data from 1960-1999. The results suggest that the observed mean wind speeds significantly weakened and the near-surface wind power trended downward due to urbanization and other land-use changes in the last 40 years. The mean wind energy weakened by -3.84 W·m^-2 per decade due to the influence of anthropogenic land-use change, which is close to the observed climate change （-4.51 W·m^-2/10 a）.     

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 of the catchment, in sharp decrease of the 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⁻² a⁻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 14335 t km⁻² a⁻¹ in 1994 to 7034 t km⁻² a⁻¹ in 1995 and 3517 t km⁻² a⁻¹ in 1996, while the yield of the gully area varied between 44944 and 62136 t km⁻² a⁻¹ during the period of 1994–1996 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 from 23% in 1994 to 15% in 1995 and 6% in 1996, while the contribution from the gully area increased from 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.     

Effect of Cl- on photosynthetic bicarbonate uptake in two cyanobacteria Microcystis aeruginosa and Synechocystis PCC6803

Photosynthetic inorganic carbon utilization was investigated in two cyanobacteria Microcystis aeruginosa and Synechocystis PCC6803 grown in standing culture. Photosynthetic rates for the two algae reached about 10 times the theoretical CO₂ supply rate at low dissolved inorganic carbon (DIC) of 100 μmol/L, and the rates were unaffected by the addition of 20 mmol/L Na⁺, indicating that the two algae possessed Na+-independent HCO^-₃ utilization for photosynthesis under low DIC. Their photo- synthetic rates at low DIC were inhibited by higher Cl^- and the degrees of inhibition were increased with the rise of CI^- concentration, and in the presence of Diphenylamine-2-carboxylate (DPC), a reported Cl^- channel inhibitor, the rates decreased by 74%－82%, implying that putative DPC-sensitive Cl^- channels participate in Na+-independent HCO₃^- uptake for photosynthesis. The experiment of intracellular 14C-DIC accumulation for photosynthesis showed that internal DIC pools decreased by about 80% with 200 μmol/L DPC and by 64%－70% with 100 mmol/L Cl^-. The experiment of chlorophyll a fluorescence quenching showed that initial rates and extents of fluorescence quenching obviously decreased with 200 μmol/L DPC or 100 mmol/L Cl^-. The two experiments gave further evidence that putative DPC-sen- sitive Cl^- channels participate in Na+-independent HCO^-₃ uptake for photosynthesis in the two algae grown in standing culture.     

Soil erosion rates and characteristics of typical alpine meadow using <Superscript>137</Superscript>Cs technique in Qinghai-Tibet Plateau

Alpine meadow is the predominant ecosystem in Qinghai-Tibet Plateau.The firm turf of alpine meadow formed by sub-surface anfractuous roots can be effective in conserving water and soil.Alpine meadow is a primary contributor to the Chinese Water Tower.For quantitative assess anti-erosion ability of alpine meadow,this paper selected three typical meadow slopes with>60% vegetation coverage to evaluate soil erosion rates using 137Cs.The results showed that(1)soil erosion intensity of typical alpine meadow was slight to light.Erosion rates were 464 t km–2 a–1 in Malong Village,415 t km–2 a–1 in Yeniugou Town and 875 t km–2 a–1 in Zhenqin Town respectively;(2)soil erosion rates were correlated negatively with vegetation coverage,and the relationship was clearer at the slope scale than plot scale;(3)the relationship between soil erosion and vegetation coverage showed that vegetation coverage was a predominant factor in retaining soil and water on slopes.With complete turf and high vegetation coverage, alpine meadow was of great significance for soil conservation and prevention of soil erosion.     

Southwest monsoon changes indicated by oxygen isotope of ostracode shells from sediments in Qinghai Lake since the late Glacial

The δ 18O records of ostracode shells in sediments of core QH-2000 from Qinghai Lake can be used as a better proxy to reflect monsoon changes. Low monsoon precipitation between 17.5 and 11 cal. ka BP is indicated by positive δ 18O values averaging 2.37‰. A fast shift in δ 18O from positive at 11 cal. ka BP to negative at 10 cal. ka BP indicates sharp increase of monsoon precipitation. An interval of generally high monsoon precipitation is observed between 10 and 6 cal. ka BP with δ 18O values averaging -2.15‰. Decrease of monsoon precipitation between 6 and 2.5 cal. ka BP is indicated by positive δ 18O values. δ 18O keeps positive values averaging 3.0‰ between 2.5 and 0 cal. ka BP suggesting low high monsoon precipitation. The climatic changes indicated by δ 18O records of ostracode shells in sedi- ments of core QH-2000 from Qinghai Lake and our broader regional comparison show that the climate in Qinghai Lake since the late Glacial is probably controlled by southwest monsoon other than southeast monsoon.     

137Cs tracing of lacustrine sediments in the Dalian Lake, Qinghai Province, China

Based upon the analysis of Cs and grain-size parameters, the total amounts of ¹³⁷Cs deposition by wind and water in the Dalian Lake of Gonghe Basin, Qinghai Province are defined. The vertical profile of ¹³⁷Cs in the lacustrine sediments exhibits three ¹³⁷Cs activity maxima and one minimum. The major maximum corresponds to the global ¹³⁷Cs fallout in 1963; the two secondary maxima correspond to the leakage of the Chernobyl reactor in 1986 and complete desiccation of the lake in 1994, respectively. The minimum corresponds to aeolian deposition caused by extensive reclamation in the late 1980s and early 1990s. The 137Cs data set was used to evaluate average sedimentation rate of the Dalian Lake since 1963. The deposition was stable in 1963-1986 and 1994-1998, and it was rapid during 1986-1994. This preliminary study reveals that l37Cs has the same potential to trace environmental changes introduce by human interference in arid/semiarid regions as in humid regions.     

Investigation of the cross-reaction mechanism of C<Subscript>6</Subscript>H<Subscript>5</Subscript>F-HNO<Subscript>2</Subscript> aqueous solution irradiated at 355 nm by transient absorbance spectrum technique

The transient absorption spectrum technique was employed to investigate the cross-reaction mechanism of C6H5F-HNO2 aqueous solution irradiated at 355 nm. The characteristic and the kinetic parameters of transient species were also detected. Hydroxyl radical derived from the photolysis of HNO2 was added to monofluorobenzene with a second-order rate constant of （5.83±0.17）×10^9 L·mol^-1·s^-1 to form an adduct, C6H5F…OH, which was able to react with HNO2 as the main reaction pathway with a rate constant of （8.3±0.1）×10^7 L·mol^-1·s^-1. The C6F6…OH adduct can also be decayed by elimination of H2O to yield monofluorophenyl radical C6H4F-. By GC-MS technique, the final products were identified to be monofluorophenol, nitro-monofluorobenzene, nitro-monofluorophenol and para-fluorobiphenyl.     

Identification of the deposited layers in landslides reservoir and investigation of the sediment yields during the later sixteenth century on the Hill Loess Plateau,China

There are many sediment trapping reservoirs in the Hill Loess Plateau. The Huangtuwa small catchment is selected as a research field where samples were collected in a sediment deposit profile with a vertical length of 12.73 m. By the variation of fine particle content and pollen concentration, 54 flood couples were identified. Taking the freeze-thawing disturbed texture as the sign of the latest flood couple in a year, it is ascertained that those 54 floods should happen in 31 years. Using pyramid volume calculation formula, the sediment yields of flood ranged between 716-30376 t· km^-2, The average sediment yield was 7106 t· km^-2, The annual sediment yields varied between 968-55579 t· （km^2· a）^-1, and the average value is 12629 t· （km^2· a）^-1. Compared with the modern annual sediment discharge of the Huaining River, the erosion rate in the Huangtuwa region 450 years ago was similar to the modern erosion rate. In the period from the 27th year to the 31st year, the average annual sediment yield increased sharply to 31309 t· （km^2· a）^-1. It implied that re-reclamation of the abandoned land in the catchment since the landslide disaster, where vegetation had rehabilitated already, caused very severe soil erosion in the catchment.     

Petrographic and geochemical characterization of seep carbonate from Alaminos Canyon,Gulf of Mexico

Seep carbonates were collected from the Alaminos Canyon lease area, Gulf of Mexico. The carbonates are present as slabs and blocks. Bivalve shell and foraminifer are the dominant bioclasts in carbonate. Pores are common and usually filled with acicular aragonite crystals. XRD investigation shows that aragonite is the dominate mineral （98%）. Peloids, clotted microfabirc and botryoidal aragonite are developed in carbonate and suggest a genesis linked with bacterial degradation of the hydrocarbons. The δ^13C value of bioclasts in carbonate is from -4.9‰ to -0.6‰, indicating that the carbon source is mainly from sea water as well as the small portion incorporation of the seep hydrocarbon. The microcrystalline and sparite aragonite shows the δ^13C value from -31.3‰ to -23.4‰, suggesting that their carbon is derived mainly from microbial degradation of crude oil. ^14C analyses give the radiocarbon age of about 10 ka. Rare earth elements （REE） analyses of the 5% HNO3-treated solution of the carbonates show that the total REE content of the carbonates is low, that is from 0.752 to 12.725 μg·g^-1. The shale-normalized REE patterns show significantly negative Ce anomalies. This suggests that cold seep carbonate is most likely formed in a relatively aerobic environment.     

Direct electrochemistry and electrocatalysis of horseradish peroxidase in MnO2 nanosheet film

A novel material MnO2 nanosheet has been used as the support matrix for the immobilization of horseradish peroxidase （HRP）. HRP entrapped in MnO2 nanosheet film exhibits facile direct electron transfer with the electron transfer rate constant of 6.86 s^-1. The HRP/MnO2 nanosheet film gives a reversible redox couple with the apparent formal peak potential （E^0＇） of -0.315 V （vs. Ag/AgCl） in pH 6.5 phosphate buffer solution （PBS）. The formal potential E^0＇ of HRP shifts linearly with pH with a slope of -53.75 mV.pH^-1, denoting that an electron transfer accompanies single-proton transportation. The immobilized HRP shows an electrocatslytic activity to the reduction of H2O2. The response time of the biosensor for H2O2 is less than 3 s, and the detection limit is 0.21 μmol · L^-1 based on signal/noise = 3.     

The minimization of non-equilibrium plasma source at high pressure

The density of plasma produced by atmospheric non-equilibrium plasma source is the function of energy dissipation rate in ionization electric field and gas particles momentum. The experiment shows that the plasma density highly rises with the increasing of energy dissipation rate and gas particles momentum. When the energy dissipation rate of activation field is 2.18 Wh/m^3 and the average gas particles momentum is 109×10^-22 g· m/s, the air throughput of plasma source whose volume is only 2.5 cm^3 can be up to 12 m^3/h and the density of plasma can be up to 10^10 cm^-3. The research can develop a method of producing minitype plasma source which is low energy consumption but high ion concentration used for chemical industry, environmental engineering and military.     

Styrene polymerization catalyzed by nickel complexes bearing hydroxyindanone-iminate ligands

Activated by methylaluminoxane, mononuclear bis（hydroxyindanone-iminate）nickel complexes Ni[ArN=CC2H3（CH3）C6H2（R）O]2 （Ar = 2,6-i-Pr2C6H3, R=Me（1）, R=CI（2）, and R=H（3）） showed good activity for the styrene polymerization. The effect of many reaction parameters including the AI/Ni ratio, temperature, and reaction time on catalytic activities of catalytic systems and the molecular weights of the obrained polystyrene was ascertained. The highest activity of 1.34×10^5g（PS）·mol^-1（Ni）·h^-1 was obtained under the optimum reaction condition. The ^13C NMR spectra of the polymers revealed that the polymer was isotactic-rich atactic polystyrene. And the coordination mechanism was confirmed by the analyses of the polymer chain end-groups.     

An in-situ DRIFTS study in the reaction between NO x and soot on BaAl2O4

The interactions between NO, O2 and their mixture on BaAl2O4, as well as the reaction of NOx with soot in the presence of O2, have been investigated using Diffuse Reflectance Infrared Fourier Transform Spectroscopy （DRIFTS）. NO adsorption produces only nitrites species in the absence of O2. NO2 adsorption produces nitrates species besides nitrites species. The produced nitrites will further react with O2, Osurf^-. and Olattice^2- to form nitrates. The reaction of NOx with soot begins with the reaction of nitrates with soot oxygenated complex （C（O））, which is regarded as the key and rate determining step. A reaction pathway is proposed for the catalyzed reaction of NOx with soot in the presence of O2.