Gross nitrogen transformations and N2O emission sources in sandy loam and silt loam soils

The soil type is a key factor influencing N(nitrogen)cycling in soil;however,gross N transformations and N_(2)O emission sources are still poorly understood.In this study,a laboratory 15N tracing experiment was carried out at 60%WHC(water holding capacity)and 25℃to evaluate the gross N transformation rates and N_(2)O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province,China.The results showed that the gross rates of N mineralization,immobilization,and nitrification were 3.60,1.90,and 5.63 mg N/(kg·d)in silt loam soil,respectively,which were 3.62,4.26,and 3.13 times those in sandy loam soil,respectively.The ratios of the gross nitrification rate to the ammonium immobilization rate(n/ia)in sandy loam soil and silt loam soil were all higher than 1.00,whereas the n/ia in sandy loam soil(4.36)was significantly higher than that in silt loam soil(3.08).This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil,and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO_(3)–leaching.Under aerobic conditions,both nitrification and denitrification made contributions to N_(2)O emissions.Nitrification was the dominant pathway leading to N_(2)O production in soils and was responsible for 82.0%of the total emitted N_(2)O in sandy loam soil,which was significantly higher than that in silt loam soil(71.7%).However,the average contribution of denitrification to total N_(2)O production in sandy loam soil was 17.9%,which was significantly lower than that in silt loam soil(28.3%).These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.

Key Problems and Countermeasures in CO_(2)Flooding and Storage

Based on literature research in combination with the practice of CO_(2)flooding and storage in Jilin Oilfield,this study assesses the key problems in CO_(2)flooding and storage,proposing the corresponding countermeasures from five aspects of CO_(2)gas source condition,namely geological condition evaluation,scheme design incoordination with other production methods,economic and effectiveness evaluation,together with dynamic monitoring and safety evaluation.The results show that CO_(2)flooding is the most economic and effective CO_(2)storage method.In eastern China,inorganic origin CO_(2)gas reservoirs are widely developed and are especially the most enriched in the Paleozoic carbonate rock strata and the Cenozoic Paleogene–Neogene system,which provide a rich resource base for CO_(2)flooding and storage.In the future,CO_(2)generated in the industrial field will become the main gas source of CO_(2)flooding and storage.The evaluation of geological conditions of oil and gas reservoirs is the basis for the potential evaluation,planning scheme design and implementation of CO_(2)flooding and storage.CO_(2)storage should be below the depth of 800 m,the CO_(2)flooding and storage effects in lowpermeability oil reservoirs being the best.CO_(2)geological storage mechanisms primarily consist of tectonic geological storage,bound gas storage,dissolution storage,mineralization storage,hydrodynamic storage and coalbed adsorption storage.The practice of CO_(2)flooding and storage in Jilin Oilfield demonstratesthat the oil increment by CO_(2)flooding is at least 24%higher than by conventional water flooding.The most critical factor determining the success or failure of CO_(2)flooding and storage is economic effectiveness,which needs to be explored from two aspects:the method and technology innovation along with the carbon peaking and carbon neutrality policy support.After CO_(2)is injected into the reservoir,it will react with the reservoir and fluid,the problem of CO_(2)recovery or overflow will occur,so the dynamic monitoring and safety evaluation of CO_(2)flooding and storage are very important.This study is of great significance to the expansion of the application scope of CO_(2)flooding and storage and future scientific planning and deployment.

Preparation of Ta-Doped TiO2 Using Ta2O5 as the Doping Source

A novel method for preparing Ta-doped Ti02 via using Ta2 05 as the doping source is proposed. The preparation process combines the hydrothernlal fluorination of Ta2O5 and the subsequent formation of Ta-doped TiO2 sol. The results show that the doped sample annealed at 393 K generates an unstable intermediate NH4 TiOF3, which converts into anatase TiO2 with the increase of temperature. After annealing at ≥673K, the Ta-doped TiO2 nanocrystals with the grain size 〈20nm are obtained. Both the XRD and TG-DSC results confirm that Ta doping prevents the anatase-rutile crystal transition of TiO2. The band gap values of the doped samples, as obtained by UV-vis diffuse reflectance spectra, are smaller than that of pure anatase TiO2. The first-principle pseudopotential method calculations indicate that Ta5＋ lies in the TiO2 lattice at the interstitial position.

Surface enhancement of molecular ion H2+yield in a 2.45-GHz electron–cyclotron resonance ion source

High current hydrogen molecular ion beam is obtained with a specially designed stainless steel liner permanent magnet2.45-GHz electron–cyclotron resonance（ECR） ion source（PMECR II） at Peking University（PKU）. To further understand the physics of the hydrogen generation process inside a plasma chamber, theoretical and experimental investigations on the liner material of the plasma chamber in different running conditions are carried out. Several kinds of materials, stainless steel（SS）, tantalum（Ta）, quartz, and aluminum（Al） are selected in our study. Experimental results show that stainless steel and tantalum are much better than others in H~＋_2 generation. During the experiment, an increasing trend in H~＋_2 fraction is observed with stainless steel liner after O_2 discharge inside the ion source. Surface analyses show that the roughness change on the surface after O_2 discharge may be responsible for this phenomenon. After these studies, the pure current of H~＋_2 ions can reach 42.3 mA with a fraction of 52.9%. More details are presented in this paper.

Enhanced Loading of ^(40)K from Natural Abundance Potassium Source with a High Performance 2D^+ MOT

40K is one of the most important atomic species for ultra-cold atomic physics. Due to the extremely low con- centration （0.012%） of 40K in natural abundance of potassium, most experiments use 4-10% enriched potassium source, which have greatly suffered from the extremely low annual production and significant price hikes in recent years. Using naturally abundant potassium source, we capture 5.4 × 10 6 cold 40K atoms with the help of a high performance of two-dimensional magneto-optical trap （2D＋ MOT）, which is almost three orders of magnitude greater than previous results without the 2D＋ MOT. The number of the 40K atoms is sufficient for most ultra-cold 40K experiments, and our approach provides an ideal alternative for the field.

Low-complexity 2D coherently distributed sources decoupled DOAs estimation method

The existing directions-of-arrival （DOAs） estimation methods for two-dimensional （2D） coherently distributed sources need one- or two-dimensional search, and the computational complexities of them are high. In addition, most of them are designed for special angular signal distribution functions. As a result, their performances will degenerate when deal with different sources with different angular signal distribution functions or unknown angular signal distribution functions. In this paper, a low-complexity decoupled DOAs estimation method without searching using two parallel uniform linear arrays （ULAs） is proposed for coherently distributed sources, as well as a novel parameter matching method. It can resolve the problems mentioned above efficiently. Simulation results validate the effectiveness of our approach.

Impact of animal manure addition on the weathering of agricultural lime in acidic soils＂ The agent of carbonate weathering

Fertilization and aglime(agricultural lime) application, as important agricultural activities in acid soil, exert an influence on the fluxes of carbon both between and within ecosystems. Animal manure added to soil can elevate the soil CO_2 and release organic acid due to microbial decomposition of the high organic matter content of animal manure. Additionally, the elevated CO_2 can accelerate carbonate weathering in alkaline soil, such as lime soil. However, in acidic soil, it is unclear whether the chemical weathering of additive aglime can be quickened by the elevated CO_2 due to animal manure addition. Thus, to ascertain the impact of animal manure addition on aglime weathering in acidic soil and to understand the weathering agent of aglime or underlying carbonate in the acidic soil profile, we established two contrasting profiles(control profile and manurial profile) in a cabbage-corn or capsicum-corn rotation in a field experiment site located in the Hua Xi district of Guiyang, China, and buried carbonate rock tablets at different depths of soil profiles to calculate the dissolution rate of carbonate rock by monitoring the weights of the tablets. The results indicated that soil CO_2 increased due to animal manure addition, but the rate of dissolution of the carbonate rock tablets was reduced, which was attributed to the increase in the p H in acidic soil after animal manure addition because the relationship between the dissolution rate of carbonate rock and soil p H indicated that the weathering rate of carbonate rock was controlled by pH and not by CO_2 in acidic soil. Thus, the contribution of H+ ions(mainly exchangeable acid) in acid soil as a weathering agent to the weathering of underlying carbonate(and/or aglime) may lead to the overestimation of the CO_2 consumption through chemical weathering at the regional/global scale using hydro-chemical methods.

Phase and particle of Y-doped Ni(OH)_2 prepared from different nickel sources and Na_2CO_3 amount

Multiple nano-sized a-Ni（OH）2was synthesized by ultrasonic-assisted precipitation under different conditions. The crystal structure and particle size distribution of the sample were characterized with X-ray diffraction（XRD）, infrared spectroscopy, and laser particle size analyzer（PSA）. The results show that the samples are anisotropic polycrystalline of a and b Ni（OH）2, and the ratio of a and b changes with the difference of nickel source, resulting in the largest ratio of a-Ni（OH）2using nickel nitrate as reactant. Larger amount of Na2CO3is conducive to the formation of a-Ni（OH）2; while the resultant phases are all b with the same conditions but no doping. The results of PSD indicate that the samples are about 100–120 nm in size, and the sample with nickel sulfate as nickel source has the minimum particle size. The three ions of nickel source appear in the absorption peaks in the Fourier transform infrared spectrum showing that the ions change the crystal structure of Ni（OH）2. EDS testing shows that Y and anion distribute in the lattice of aNi（OH）2uniformly.

Effect of different carbon sources on performance of an A2N- MBR process and its microbial community structure

Effect of different carbon sources on purification performance and change of microbial community structure in a novel AzN-MBR process were investigated, The results showed that when fed with acetate, propionate or acetate and propionate mixed （ 1 ： 1 ） as carbon sources, the effluent COD, NH4＋- N, TN and TP were lower than 30, 5, 15 and 0.5 mg-L-1, respectively. However taken glucose as carbon source, the TP concentration of effluent reached 2.6 1 mg.L-1. Process analysis found that the amount of anaerobic phosphorus release would be the key factor to determine the above effectiveness. The acetate was beneficial to the growth of Candidatus Accumulibacter associated with biological phosphorus removal, which was the main cause of high efficiency phosphorus removal in this system. In addition, it could eliminate the Candidatus Competibacter associated with glycogen-accumulating organisms and guarantee high efficiency phosphorus uptake of phosphorus accumulating organisms in the system with acetate as carbon source.

Meteorological Tower Observed CO_(2)Flux and Footprint in the Forest of Xiaoxing’an Mountains,Northeast China

The Xiaoxing’an Mountains,located in the temperate monsoon climate zone in Northeast China,have the largest and most complete virgin Korean pine forest in Asia,which has great potential for carbon sequestration.Based on the observational data of the eddy-covariance system at Wuying National Climate Observatory in January 2015–November 2017,the CO_(2)flux in the forest ecosystem around the observatory was quantitatively studied and the distribution characteristics of the flux source area were analyzed by the Kljun model and the Agroscope Reckenholz–Tänikon footprint tool,providing references for assessing the carbon source/sink potential of the unique forest area.The results showed that the annual total carbon flux around the observatory in 2015,2016,and 2017 was−756.84,−834.73,and−629.37 gC m−2,respectively,higher than that of other forest ecosystems.The forest of the study area in the Xiaoxing’an Mountains was a strong carbon sink,with the strongest carbon fixation capacity in June and weakest in October,and the carbon flux of each month was less than zero.The flux source area under stable atmospheric conditions was larger than that under unstable conditions,and the source area was larger in the nongrowing season than in the growing season.The size of the source area was largest in winter,followed by spring,autumn,and summer.The maximum length of the source area was 1614.12 m(5639.33 m)under unstable(stable)conditions when the flux contribution rate was 90%.The peak flux contribution was located near the sensor(i.e.,within 200 m)in all seasons.The contribution of the source area from the coniferous and broadleaved mixed forest on the west side of the observatory was greater than(3.4 times)that from the Korean pine forest on the east side.

Calculation of Response Function for Bonner Sphere Spectrometer Based on Geant4

In order to make further studies on fusion neutron diagnosis on HL-2A /HL-2M,we have developed and succeeded in the calculation of the Response Function for a Bonner sphere spectrometer,which consists of eight polyethylene spheres with ^3He proportional counters inside.The response function of the Bonner spectrometer to neutrons is of fundamental importance for its neutron spectrum unfolding procedure and is directly related to the quality of the unfolded spectrum.In this paper,we calculated the response function to neutrons from 10^-9 MeV to100 MeV by Geant4.In order to test the accuracy of the Geant4 simulation,we apply it to measure an ^241Am-Be neutron source,and the measured neutron counts of the spectrometer and simulated counts are found to be highly consistent,with a relative error up to 9.3%.This has proven the calculation of the neutron response of the Bonner sphere spectrometer by Geant4 to be quite accurate.

Turnover of dissolved organic carbon fuels nocturnal CO_(2) emissions from a headwater catchment reservoir, Southeastern China: Effects of ecosystem metabolism on source partitioning of CO2 emissions

Dam reservoirs in headwater catchments, as critical zones for their proximity to terrestrial sources, play important roles in dissolved organic carbon(DOC) cycling. However, the effects of ecosystem metabolism(EM) on DOC cycling are not well known. Here, in-situ diurnal and monthly observations were conducted to measure EM(including gross primary production(GPP), ecosystem respiration(ER) and heterotrophic respiration(HR)), DOC turnover and CO_(2)emissions in a headwater catchment reservoir in Southeastern China in 2020. Our study showed the nocturnal CO_(2)emission rate was about twice as high as in daytime, and was strongly driven by EM. The values for DOC turnover velocity ranged from 0.10 to 1.59 m/day,and the average DOC turnover rate was 0.13 day-1, with the average removal efficiency of 12%. The contribution of respired DOC to daily CO_(2)emissions ranged from 17% to 61%. The accumulated efficiencies were estimated to be 13% for the selected 15 reservoirs throughout the Changjiang River network, corresponding to about 0.34 Tg C/year of the respired DOC.The modified CO_(2)flux was 0.75 Tg C/year, and respired DOC accounted for about 45% of total emitted CO_(2)from the 15 larger reservoirs. Our research emphasizes the necessity of incorporating the effects of EM into studies of reservoir DOC removal and COemissions.

Identification of causative compounds and microorganisms for musty odor occurrence in the Huangpu River,China

There are regular problems of musty odor in the Huangpu River,a major source of drinking water for Shanghai,China.In this study,the musty odor and its main causative compounds in the Huangpu River source water were confirmed through a yearly investigation using flavor profile analysis combined with HSPME-GC-MS analysis.The investigation showed that 2-methylisoborneol （2-MIB） with a concentration level between 28.6 and 71.0 ng/L was responsible for the musty odor in summer from July to September.Microscopic observation confirmed with the cloning results showed that Phormidium spp.,which accounted for 80%-95% of the algal cell density,was the microorganisms responsible for the production of 2-MIB and the estimated 2-MIB yield was 0.022 pg/cell.Results from a wide-area sampling campaign in the Huangpu River watershed showed that,other than the large tributaries receiving water from Tai Lake,several small creeks close to the intake may have contributed most of the 2-MIB and the Phormidium spp.to the Huangpu River source water.This study provides methodology for the investigation of odor causing compounds and microorganisms in river-type source water,and the result will be useful for water quality control in both source water and drinking water.

Size distribution,directional source contributions and pollution status of PM from Chengdu,China during a long-term sampling campaign

Long-term and synchronous monitoring of PMIo and PM2.s was conducted in Chengdu in China from 2007 to 2013. The levels, variations, compositions and size distributions were investigated. The sources were quantified by two-way and three-way receptor models （PMF2, ME2-2way and ME2-3way）, Consistent results were found： the primary source categories contributed 63.4% （PMF2）, 64.8% （ME2-2way） and 66.8% （ME2-Bway） to PMIo, and contributed 60.9% （PMF2）, 65.5% （ME2-2way） and 61.0% （ME2-3way） to PM2.s. Secondary sources contributed 31.8% （PMF2）, 32.9% （ME2-2way） and 31.7% （ME2-3way） to PMIo, and 35.0% （PMF2）, 33.8% （ME2-2way） and 36.0% （ME2-3way） to PM2.s. The size distribution of source categories was estimated better by the ME2-3way method. The three-way model can simultaneously consider chemical species, temporal variability and PM sizes, while a two-way model independently computes datasets of different sizes. A method called source directional apportionment （SDA） was employed to quantify the contributions from various directions for each source category. Crustal dust from east-north-east （ENE） contributed the highest to both PM^o （12.7%） and PMzs （9.7%） in Chengdu, followed by the crustal dust from south-east （SE） for PMao （9.8%） and secondary nitrate ＆ secondary organic carbon from ENE for PMzs （9.6%）. Source contributions from different directions are associated with meteorological conditions, source locations and emission patterns during the sampling period. These findings and methods provide useful tools to better understand PM pollution status and tn dovolon offoctive nolhltion control gtrateMeg.

Numerical study of the flow in the Yellow River with non-monotonous banks

A 2-D depth averaged RNG k- ε model is developed to simulate the flow in a typical reach of the Upper Yellow River with non-monotonic banks. In order to take account of the effect of the secondary flow in a bend, the momentum equations are modified by adding an additional source term. A comparison between the numerical simulation and the field measurements indicates that the improved 2-D depth averaged RNG k- ε model can improve the accuracy of the numerical simulation. An arc spline interpolation method is developed to interpolate the non-monotonic river banks. The method can also be reasonably applied for the 2-D interpolation of the river bed level. Through a comparison of the water surface gradients simulated in the seven bends of the studied reach, some analytical formulae are improved to reasonably calculate the longitudinal and transverse gradients in meandering river reaches. Furthermore, the positions of the maximum water depth and the maximum velocity in a typical bend are discussed.