RESEARCH ON THE LOCAL CORRECTION MODEL OF ATMOSPHERIC DRY DELAY IN GPS REMOTE SENSING WATER VAPOR

The precision of atmospheric dry delay model is closely correlated with the accuracy of GPS water vapor in the process of GPS (Global Position System) remote sensing. Radiosonde data (from 1996 to 2001) at Qingyuan are used to calculate the exact values of the atmospheric dry delay. Base on these calculations and the surface meteorological parameters, the local year and month correction models of dry delay at the zenith angle of 0° are established by statistical methods. The analysis result shows that the local model works better and is slight more sensitive to altitude angle than universal models and that it is not necessary to build models for each month due to the slight difference between year model and month model. Furthermore, when the altitude angle is less than 75°, the difference between curve path and straight path increases rapidly with altitude angle’s decrease.

Annual Fluxes of Heavy Metal Elements in Atmospheric Dry and Wet Depositions in the Pearl River Delta Economic Region, Guangdong Province

There are 158 sampling points to be set up in the Pearl River delta economic region. The collecting period is mostly one year, namely, from July 2007 to July 2008. The eight heavy metal elements of Cr, Ni, Cu, Pb, Zn, As, Hg, and Cd in 474 dry and wet deposition samples were tested in terms of the standard procedures. Their average annual fluxes have no obvious difference between dry deposition and wet deposition. So these elements might be at an equilibrium or quasi-equilibrium state between dry deposition and wet deposition.

Atmospheric Drying UHMWPE Membranes via Multiple Stage Extractant Exchange Drying Technique

Ultra-high molecular weight polyethylene(UHMWPE)membranes were prepared by 5 wt%UHMWPE/parafn oil gels via thermally induced phase separation method and dried in air without signifcant collapse.The UHMWPE membranes were annealed at 110℃ for increasing the pores size in order to decrease the capillary forces.Furthermore,a new multiple stage extractant exchange drying(MSEED)technique was adopted to decrease the shrinkage of the UHMWPE membranes.Specifcally,the parafn oil was extracted by dichloromethane,then dichloromethane was replaced by ethanol,next ethanol could be exchanged to other liquid which is non-afnity with UHMWPE,for example water.UHMWPE membranes(annealing for 25 min)dried by dichloromethane-ethanol-water-air process have the lowest volume shrinkage of 16.5%and the porosity is as high as 88.29%.Moreover,compared with supercritical CO_(2)(SC-CO_(2))drying,atmospheric drying UHMWPE membranes have a lower pure water permeance,but a higher carbon particles rejection.

Atmospheric deposition of inorganic nitrogen in a semi-arid grassland of Inner Mongolia, China

Due to increasing global demand for crop production and energy use, more and more reactive nitrogen（Nr） has been generated and emitted to the environment. As a result, global atmospheric nitrogen（N） deposition has tripled since the industrial revolution and the ecological environment and human health have been harmed. In this study, we measured dry and wet/bulk N deposition from July 2013 to December 2015 in a semi-arid grassland of Duolun County, Inner Mongolia, China. The samples of dry and wet/bulk N deposition were collected monthly with a DELTA（DEnuder for Long Term Atmospheric sampling） system and with Gradko passive samplers and a precipitation gauge. The measured results show that the annual mean concentrations of NH_3, NO_2, HNO_3, particulate NH_4~＋（pNH_4~＋） and particulate NO_3^-（pNO_3^-） in atmosphere were 2.33, 1.90, 0.18, 1.42 and 0.42 μg N/m3, respectively, and that the annual mean volume-weighted concentrations of NH_4~＋-N and NO_3^--N in precipitation were 2.71 and 1.99 mg N/L, respectively. The concentrations of Nr components（including NH_3, NO_2, HNO_3, p NH_4~＋, pNO_3^-, NH_4~＋-N and NO_3^--N） exhibited different seasonal variations. Specifically, NO_2 and HNO_3 exhibited higher concentrations in autumn than in summer, while the other Nr components（NH_3, pNH_4~＋, pNO_3^-, NH_4~＋-N and NO_3^--N） showed the highest values in summer. Based on measured concentrations of Nr components and their deposition velocities estimated using the GEOS-Chem global atmospheric chemical transport model, the calculated annual mean dry deposition fluxes were 3.17, 1.13, 0.63, 0.91 and 0.36 kg N/（hm^2·a） for NH_3, NO_2, HNO_3, p NH_4~＋ and pNO_3^-, respectively, and the calculated annual mean wet/bulk deposition fluxes were 5.37 and 3.15 kg N/（hm^2·a） for NH_4~＋-N and NO_3^--N, respectively. The estimated annual N deposition（including dry N deposition and wet/bulk N deposition） reached 14.7 kg N/（hm^2·a） in grassland of Duolun County, approaching to the upper limit of the N critical load（10–15 kg N/（hm^2·a））. Dry and wet/bulk deposition fluxes of all Nr components（with an exception of HNO_3） showed similar seasonal variations with the maximum deposition flux in summer and the minimum in winter. Reduced Nr components（e.g., gaseous NH_3 and p NH_4~＋ in atmosphere and NH_4~＋-N in precipitation） dominated the total N deposition at the sampling site（accounted for 64% of the total N deposition）, suggesting that the deposited atmospheric Nr mainly originated from agricultural activities. Considering the projected future increases in crop and livestock production in Inner Mongolia, the ecological and human risks to the negative effects of increased N deposition could be increased if no mitigation measures are taken.

Morphology and Structure of SiO_2 Film Using Thermal Oxidation Process on(111)Silicon Crystals in Dry Oxygen Atmosphere

By means of scanning electron microscope(SEM)and high voltage electron microscope(HVEM)we have observed and analysed morphology and micro-structure of silicon oxide film with different thickness formed on(111)silicon monocrystal under dry oxygen atmosphere at 1100℃.Compared with their oxidation kinetic curves consisted of three stages,we suggested a mechanism on forming silicon oxide film.According to electron and X-ray diffraction analyses the silicon oxide films consisted of silica with different crystal structure.We also have discussed a stacking fault and a dislocation formed in the Si-Sio_2 interface region simulaneously forming silicon oxide film.

Assessment of Nitrogen Pollutant Sources in Surface Waters of Taihu Lake Region

The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system （GPS）. The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region.

Surface Rainfall and Cloud Budgets Associated with Mei-yu Torrential Rainfall over Eastern China during June 2011

Surface rainfall and cloud budgets associated with three heavy rainfall events that occurred over eastern China during the mei-yu season in June 2011 were analyzed using 2D cumulus ensemble model simulation data.Model domain mean rainfall showed three peaks in response to three prescribed ascending motion maxima,primarily through the mean moisture convergence during the torrential rainfall period.Prescribed ascending motion throughout the troposphere produced strong convective rainfall during the first （9 June） and third （17-18 June） rainfall events,whereas strong prescribed ascending motion in the mid and upper troposphere and weak subsidence near the surface generated equally important stratiform and convective rainfall during the second rainfall event （14 June）.The analysis of surface rainfall budgets reveals that convective rainfall was associated with atmospheric drying during the first event and moisture convergence during the third event.Both stratiform and convective rainfall responded primarily to moisture convergence during the second event.An analysis of grid data shows that the first and third mean rainfall maxima had smaller horizontal scales of the precipitation system than the second.

PREPARATION OF MULTI-WALLED CARBON NANOTUBES USING NiO CATALYST SYNTHESIZED BY HYDROTHERMAL METHOD

The Ni(OH)2/SiO2 binary colloid was prepared using Ni(NO3)2.6H2O and (C2H5O)4SiO4 as starting materials and was used to form NiO/SiO2. composite powder by hydrothermal method and desiccant method in open air respectively. Multi-walled carbon nanotubes (MWCNTs) were synthesized respectively by chemical vapor deposition using the NiO/SiO2 catalyst prepared by different methods. The phase and morphology of the catalysts and the morphology, output yield and purity of MWCNTs were compared by XRD, TEM and SEM. The results show that the catalyst powder prepared by hydrothermal method, compared with that by desiccant method, is smaller, better dispersion and has stronger catalytic activity. Pure MWCNTs with smaller tube diameter and narrow range could be obtained at a high yield using that NiO/SiO2 powder prepared by hydrothermal method as catalyst.

Atmospheric freeze drying of garlic slices based on freezing point depression

Garlic is difficult to dry due to browning reaction and degradation of heat-sensitive component.Freeze drying(FD)can keep good shape,color and nutrition of dried garlic,but it consumes long drying time and high energy.To shorten drying time and obtain high quality products,atmospheric freeze drying(AFD)was developed for drying garlic slices.The effects of different inlet air temperature programs on product quality and drying process were studied during AFD process.It was found that freeze point depression could lead to part of ice thawing resulting in product quality deterioration when the air temperature was not low enough.Based on this,a step-down-up temperature program was developed to reduce the drying time and provide good product quality.

Altitude-dependent distribution of 137Cs in the environment:a case study of Aragats massif, Armenia

This paper considers the distribution of technogenic 137Cs and naturally occurring radionuclides:238 U,232 Th and40 R concentrations in soils and 137Cs in atmospheric dry depositions by altitudinal belts of the Aragats mountain massif,Republic of Armenia.Undisturbed soil samples were collected at altitudes from 1000 to 3200 m.For the determination of geochemical variability,two soil sampling campaigns were undertaken.Atmospheric dry depositions were sampled from five stations at1100-3200 m collected onto organic fiber filters between June and December 2016.137Cs activity was measured using a high-purity Germanium detector coupled to a multichannel analyzer(Canberra).Results indicated that specific activity of 137Cs in soils at 1000 m is495-528 Bq m^-2,andat3200 mis10,500-11,470 Bq m^-2.No correlation observed for 137Cs versus naturally occurring radionuclides,which varies in distribution by altitude.Specific activities of 137Cs in dry atmospheric depositions varies from 1.06 at 846 m to2.37 Bq m^-2 per quarter at 3200 m and increases as the altitude increases.Activities of 137Cs in soil and dry atmospheric deposition correlated significantly,and 137Cs activity in soils and atmospheric dry depositions decrease as the absolute altitude decreases.The 50-year effective dose from exposure to 137Cs fallout varies with altitude from 0.007 to 1.42 m Sv.

Wet and dry deposition fluxes of heavy metals in Pearl River Delta Region(China):Characteristics,ecological risk assessment,and source apportionment

The atmospheric deposition of heavy metals poses serious risks to the ecological system and human health. To advance our knowledge of atmospheric dry/wet heavy metal deposition in the PRD region, monthly fluxes were examined based on soluble/insoluble fractions of five heavy metal elements（Cu, Pb, Cd, Cr and Zn） in samples collected from January 2014 to December 2015 at Guangzhou（urban） and Dinghushan（suburban） sites. The ratios of wet/dry deposition fluxes indicated that heavy metal deposition was governed by wet deposition rather than dry deposition in the PRD region. Affected by the shifting of the Asian monsoon, wet deposition fluxes exhibited significant seasonal variation between summer monsoon seasons（April to September） and winter monsoon seasons（October to February） in this region. Cd was classified as an extremely strong potential ecological risk based on solubility and the Hakanson ecological risk index. Source contributions to wet deposition were calculated by PMF, suggesting that dust, biomass burning, industries,vehicles, long-range transport and marine aerosol sources in Guangzhou, and Zn fertilizers,marine aerosol sources, agriculture, incense burning, biomass burning, vehicles and the ceramics industry in Dinghushan, were the potential sources of heavy metals.

Comparative study on the effects and efficiencies of three sublimation drying methods for mushrooms

Freeze drying(FD)yields the best quality of dried mushrooms but needs long drying time and higher cost.Air drying(AD)gives relatively poor product quality.In order to achieve faster drying along with high product quality,microwave freeze drying(MFD)and atmospheric freeze drying(AFD)were developed to dry mushrooms.By comparison of three sublimation drying processes,it was concluded that FD could lead to the best product quality,but cost the highest energy consumption.AFD mushrooms had the worst quality and longest drying time,but the lowest energy consumption.Compared with FD and AFD,MFD could get relatively acceptable quality and drying efficiency.As a result,MFD can be used to replace traditional FD,and AFD also should be popularized because of its low energy consumption.