7~Be: A Geochemical Tracer for Seasonal Erosion of Surface Soil in Watershed of Lake Hongfeng, Guizhou, China

7Be penetrative depth in undisturbed surface soil is within 4mm.^7Be activity shows exponential decrease with soil depth,which is expressed as a diffusion process.7Be penetrative depth in undisturbed surface soil is apparently deeper in the fall (0.22-0.37g cm^-1) than in the spring (0.11-0.28g cm^-2) at the same site;Whereas,^7Be apparent activity at the top of surface soil is higher in the spring (0.3-2.2Bq g^-1)than in the fall (0.2-0.5Bqg^-1) at the same site,The 7Be inventory(189-544Bq m^-2)changes with both locations and seasons.Although the ^7Be flux to the earth's surface increases with amount of precipitation,its maximum inventory in the soil profiles decreases to 30%-40% after the rainy period.Calculated by the diffusion equation,the erosion and accumulation rates of soil particles are agreeable with the observation in situ,Which shows that the rates in fall are 1.5 times those in spring.The eroded soil particles almost all have been removed on the tablelands rathel than transported into the drainage system.This indicates that the soil erosion process in the karst region is only partial transportation within a short distance.

Geochemical Speciation of Soil ~7Be, ^(137)Cs,^(226)Ra and ^(228)Ra as Tracers to Particle Transport

A brunisolic soil collected from an erosive forest land (HF-1-1) and a yellow soil from an accumulative shallow basin (HF-6-1) in the watershed of Lake Hongfeng (HF) were used for activity measurements of 7Be, 137Cs, 226Ra and 228Ra in different geochemical speciation. More than 85% of 7Be, 137Cs, 226Ra and 228Ra in the soils were bound to organic, Fe-Mn oxy-hydroxide and residual fractions. They could move with soil particles and be used as tracers for the erosion and/or accumulation of soil particles. 7Be geochemical speciation in the soils agreed with its trace for seasonal particle transport. 137Cs geochemical speciation was suitable for tracing soil particle accumulation and for sediment dating. 226Ra and 228Ra were combined in crystalline skeleton of clay minerals and mainly remained as residues in the soils and little was bound to the soluble, exchangeable and carbonate fractions. The differentiation of 226Ra/228Ra activity ratios in different geochemical fractions in the soils could be used as a parameter to trace accumulation and /or erosion of soil particles.

Tree-Ring Carbon Isotopic Constraints on Carbon-Water Exchanges between Atmosphere and Biosphere in Drought Regions in Northwestern China

The comparison between the carbon isotope and the index of ring width of a pine disc from the Tuomuer Peak region in Xinjiang shows that the effects of climate changes on the tree-ring growth and carbon isotopic fractionation varies with time. The reason is probably relative to the characters of climate changes and adaptability of the tree-ring growth to climate changes. The relationships between the atmospheric CO2 level and the revised δ13Cair by the tree-ring carbon isotope indicate that the carbon cycle is not in a steady state, but under a stage-change condition in this area. It also can be concluded that the ratio of CO2 from the terrestrial eco-system has increased, and the flux of CO2 exchange between the atmosphere and the biosphere was gradually increasing over the past century. In addition, the results also confirm the validity and superiority of the carbon isotope to the research of the water-use efficiency.

Atmospheric pollutants transport tracks revealed from ^(131)I, ^(137)Cs, and ^(134)Cs leaked from Fukushima accident and ~7Be and ^(210)Pb observed at Guiyang of China

A massive earthquake measuring 9.0 on the Richter scale that occurred on March 11, 2011, on Honshu Island, Japan, caused radioactivity leakage from the Fukushima Nuclear Power Plant, which led to the leakage of artificial nuclides(131I, 137 Cs, and 134Cs) and their global transportation by atmospheric circulation. This paper reports a systematic comparative observation on radioactive concentrations of natural nuclides(7Be and 210Pb) and artificial nuclides(131I, 137 Cs, and 134Cs) at the surface level, measured in weekly continuous aerosol sampling at Mount Guanfeng, Guiyang, China, from March 17, 2011 to April 28, 2011. During this period, the variations in the nuclide concentrations associated with their transport paths were analyzed with 315 hour back-trajectories of air mass initialized 500 m above the surface level at Guiyang. The results show that the pollutants of nuclear leakage from the Fukushima accident were transported to the Guiyang region of China via two significant pathways. In the first pathway the first wave of nuclear pollutants were transported from west to east in air masses at higher altitudes via global atmospheric circulation. The nuclear pollutants encircled the Earth almost once and after about 10 days to two weeks, between March 24 and March 31, 2011, intruded Guiyang from the northwestern region of China. In the second pathway, the nuclear pollutants from the Fukushima region arrived at Guiyang between April 7 and April 14, 2011, via air masses at lower altitudes that moved southwards because of the squeezing of the northeast Asian weather system and then by the influence, in succession, of the northeastern and southeastern air currents in the low-latitude region. The first transport pathway for atmospheric pollutants is on a global scale and based on air masses at higher altitudes, and the second transport pathway is on an eastern Asia regional scale and based on the air masses at lower altitude.

δ13C-δ18O Covariance:An Effective Indicator of Hydrological Closure for Lakes?

The correlation between the δ^13C and δ^13C-δ^18O in primary carbonates is affected by several factors such as hydrological balance, total CO2 concentrations, climatic condition and lake productivity. The influence of these factors on the δ^13C-δ^18O correlation may be different on different time scales. In this paper, two different-type lakes in southwestern China, Lake Erhai and Lake Chenghai, are selected to investigate the influence of climatic pattern on the δ^13C-δ^18O correlation and to evaluate the reliability of the δ^13C-δ^18O covariance as an indicator of hydrological closure. The results show that there exists good correlation between the δ^13C and δ^18O in Lake Erhai （overflowing open lake） and in Lake Chenghai （closed lake）. This suggests that the δ^13C-δ^18O covariance may be not an effective indicator of hydrological closure for lakes, especially on short time scales. On the one hand, a hydrologically open lake may display covariant δ^13C and δ^18O as a result of climatic influence. The particular alternate warm-dry and cold-wet climatic pattern in southwestern China may be the principal cause of the δ^13C-δ^18O covariance in Lake Erhai and Lake Chenghai. On the other hand, a hydrologically closed lake unnecessarily displays covariant trends between δ^13C and δ^18O because of the buffering effect of high CO2 concentration on the δ^13C shift in hyper-alkaline lakes. We should be prudent when we use the covariance between δ^13C and δ^18O to judge the hydrological closure of lake.

Sodic metasomatism in a dacite weathering profile in Pinxiang, Guangxi, China

The Pinxiang weathering profile is well developed on Early Triassic dacite lavas of the Baisi Formation. At the top of the profile is developed a red clay zone which is characterized mineralogically by kaolinite, iron oxide minerals, quartz, and a small amount of illite, montmorillonite and vermiculite. In going downwards the red clay zone gives way to a saprolite zone in which plagioclase pseudomorphs have been well preserved although replaced by kaolinite. Beneath the saprolite zone is the saprock zone characterized by less weathering for dacite. At the bottom of the weathering profile is the parent material, dacite, which is composed mainly of plagioclase, quartz, K-feldspar and biotite which have been largely altered into chlorite owing to submarine extrusion of dacite lavas. Some layers in the weathering profile show obvious sodium enrichment and potassium depletion relative to others. In the Al2O3-(CaO*+Na2O)-K2O triangular diagram, the weathering trends of these layers in the middle stage are remarkably deviated from normal ones. Both mineralogy and micro-morphology of these layers indicate such deviation resulted from sodic metasomatism of orthoclase.

Preparation and Characterization of Red Emitting Phosphor Ba_xCa_(3-x)(PO_4)_2∶Ce, Mn

Red emitting phosphor （BaCa）3 （PO4）2 ： Ce, Mn was prepared by solid state reactions. Effect of chemical component, preparation conditions on the performance of the phosphor was studied by using TGDTG, XRD and phosphor relative brightness meter. It is found that the host （ Bax Ca1-x ） 3 （PO4） 2 is present as a distorted Ca3（PO4）2 structure. Ce^3＋ acts as a sensitiser, and Mn^2＋ is activator. By energy transfer from Ce^3＋ to Mn^2＋, Mn^2＋ is activated and emits red light with wavelength around 650 nm. The phosphor powder shows the highest emitting brightness, when the con- centrations of Ce^3＋and Mn^2＋ are both at 0.15 mol.

^(10)Be/~7Be implies the contribution of stratosphere-troposphere transport to the winter-spring surface O_3 variation observed on the Tibetan Plateau

10Be/7Be is a stratospheric sensitive tracer.In this paper,measurements of 10Be/7Be and surface O3 from October 2005 to May 2006 at Mt.Waliguan (hereafter WLG,100.898°E,39.287°N,3810 m,a.s.l.),China global atmospheric watch (GAW) observatory,are introduced and used to investigate the stratosphere-troposphere transport (STT) and its impact on surface O3 on the Tibetan Plateau.The results show that the magnitude of STT is weak in winter,followed by strengthening from the end of winter to the middle of spring (from mid February to mid April) with large increases in 10Be,7Be,10Be/7Be and surface O3.At the end of spring (from the end of April to mid May in this paper),the STT weakened,and the continuous increase of surface O3 at WLG is produced by tropospheric photochemistry reactions.

Source characteristics of O_3 and CO_2 at Mt. Waliguan Observatory,Tibetan Plateau implied by using ~7Be and ^(210)Pb

The weekly averages of near-surface 7Be,210Pb,O 3,and CO2 concentrations at the Global Atmospheric Watch Observatory,Mt.Waliguan(101.98°E,36.287°N,3810 m a.s.l.) ,from October 2002 to January 2004 are presented.With the establishment of the new datasets of DCCW(Differential Concentrations in Contiguous Weeks) of 7Be,210Pb,and O 3,CO2(Δ7Be,Δ210Pb,ΔO3,ΔCO2,respectively,the impacts of upper-level downward transports and land-surface emissions on O3 and CO2 concentrations are implied by 7Be and 210Pb being as independent tracers.The relations amongΔ7Be,Δ210Pb,andΔO 3,ΔCO2 are examined statistically and compared.The results indicate that with the DCCWs,the interferences with the tracing significance of 7 Be and 210Pb from the seasonal wet scavenging of atmospheric aerosol are greatly reduced,and the weighting sources of O 3 or CO2 variations are more pronounced.Basically,the variability of surface O3 is controlled predominately by air mass transported from the upper atmosphere levels while the emission from the Continent Boundary Layer(CBL) has an obvious input for CO2.The relation betweenΔ210Pb andΔO3 reflects that influences of CBL emission are generally positive/negative for surface O3 budget in summer/winter,and the relation ofΔ7Be andΔCO2 also reveals that upper level downward transport has positive/negative inputs for CO2 in summer/winter.With the highly correlated relations between 7 Be and O3,a quantitative estimation is made of the stratospheric contributions to the budget of surface O3 at WLG:the monthly averages of stratospheric O3 range from 6×10 -9 to 8×10 -9(volume mixing ratio) in April and from June to August,and 2×10 -9 to 4×10 -9 in the remaining months.For the ultimate sources of the baseline concentration of surface O3,which consist of only stratospheric transport and tropospheric photochemistry production,the contribution from stratospheric transport is estimated to be about 20×10 -9 from May to July,and(12-15) ×10 -9 in the remaining months,and the total relative contribution rate is about 35%to 40%.

Characteristics of U-pattern distribution of high-concentration ^(210)Pb in surface air at central Guizhou,China

A better understanding of the variation of 210Pb concentrations in the surface air is the key to trace lake sedimentation and catchment erosion, to establish and vali-date the global diffusion model of contaminants, and to as-sess the impact of natural radiation on the ecological system. Basing on the study progresses of the sedimentation, the at-mospheric model and the unique environmental background in the Yunnan-Guizhou Plateau, and starting from December 20, 2001, we made use of a 500 NE Type aerosol sampler to collect filter samples, once a week in the past consecutive two years, in the surface air at Mt. Guanfeng, Guiyang City, China. Synchronous detailed γ -energy spectrometric obser-vations of 210Pb concentrations at both Chinese and U.S. laboratories have shown that the average monthly 210Pb concentration displays a regular U-patterns distribution of annual variations, with high values appearing in winter and low values in late spring and summer. The average annual 210Pb concentrations are estimated to be 2.77±0.63 mBq/m3, about 4 times the average maximum concentrations reported from quite a number of monitoring stations throughout the world. The possible factors affecting the sources of 210Pb in the surface air in the central part of Guizhou Province are: Release of 222Rn from the U-Ra series enriched in the soils; chemical weathering of carbonate rocks; the exploitation, processing and utilization of coal and phosphorous resources. The principal factor controlling the high 210Pb concentrations in the surface air in the central Guizhou and their annual U-pattern distribution is the release of 222Rn. The average monthly 210Pb concentrations show a good negative power- function relationship with increasing precipitation and also show a good negative linear-function relationship with the rise of air temperature in month grouping. Group No.1 (June to November) reflects a relatively low release of 222Rn from soils in relatively high temperature seasons; Group No.2 (December to May) mirrors a relatively high release of 222Rn from soils in relatively low temperature seasons. The average monthly 210Pb concentrations simulated in terms of the pre-cipitation and air temperature are in good consistency with the measured values, revealing that the regular U-pattern distribution characteristics of 210Pb concentrations in the surface air in the central Guizhou are controlled predomi-nantly by regional precipitation and air temperature. Meanwhile, it is also indicated that the magnitude of varia-tion of air temperature and precipitation within the same year also constrains the ratio of high values over low values of average monthly 210Pb concentrations. On a month time scale, precipitation and air temperature are a main factor affecting the release of 222Rn from soils (rocks). In this aspect strong evidence has been obtained.