The Moon provides a unique environment for investigating nearby astrophysical events such as supernovae.Lunar samples retain valuable information from these events,via detectable long-lived“fingerprint”radionuclides...The Moon provides a unique environment for investigating nearby astrophysical events such as supernovae.Lunar samples retain valuable information from these events,via detectable long-lived“fingerprint”radionuclides such as^(60)Fe.In this work,we stepped up the development of an accelerator mass spectrometry(AMS)method for detecting^(60)Fe using the HI-13tandem accelerator at the China Institute of Atomic Energy(CIAE).Since interferences could not be sufficiently removed solely with the existing magnetic systems of the tandem accelerator and the following Q3D magnetic spectrograph,a Wien filter with a maximum voltage of±60 kV and a maximum magnetic field of 0.3 T was installed after the accelerator magnetic systems to lower the detection background for the low abundance nuclide^(60)Fe.A 1μm thick Si_(3)N_(4) foil was installed in front of the Q3D as an energy degrader.For particle detection,a multi-anode gas ionization chamber was mounted at the center of the focal plane of the spectrograph.Finally,an^(60)Fe sample with an abundance of 1.125×10^(-10)was used to test the new AMS system.These results indicate that^(60)Fe can be clearly distinguished from the isobar^(60)Ni.The sensitivity was assessed to be better than 4.3×10^(-14)based on blank sample measurements lasting 5.8 h,and the sensitivity could,in principle,be expected to be approximately 2.5×10^(-15)when the data were accumulated for 100 h,which is feasible for future lunar sample measurements because the main contaminants were sufficiently separated.展开更多
The electrical conductivity of suspensions and their supernatants from the electrodialyzed clay fractions of latosol, yellow-brown soil and black soil equilibrated with nitrate solutions were determined at different f...The electrical conductivity of suspensions and their supernatants from the electrodialyzed clay fractions of latosol, yellow-brown soil and black soil equilibrated with nitrate solutions were determined at different field strengths using a short high-voltage pulse apparatus to demonstrate the Wien effect in soil suspensions and to investigate factors affecting it. It was found that Wien effect was much stronger in suspensions with a clay content of 30 g kg-1 from the soils equilibrated with a 1 × 10-4 KNO3 solution than in their supernatants.The threshold field strength (TFS), at which the relative conductivity is equal to 1.05, i.e., the Wien effect begins to be obvious, of the yellow-brown soil suspensions (clay content of 30 g kg-1) equilibrated with different nitrate solutions of a concentration of 1 × 10-4/z mol L-1 , where z is the valence, varied with the type of nitrates, being lowest for NaNO3 (47 kV cm-1) and highest for Ca(NO3)2 (98 kV cm-1). At high field strengths (larger than 130 kV cm-1), the relative conductivities of yellow-brown soil suspensions containing different nitrates diminished in the order: NaNO3 ＞ KNO3 ＞ Mg(NO3)2 ＞ Zn(NO3)2 ＞ Ca(NO3)2. The rates and intensities of the Wien effect in the suspensions of the three soils equilibrated with 5 × 10-5 molL-1 Ca(NO3)2 solution were in the order of the yellow-brown soil ＞ the latosol ＞ the black soil. The results for the yellow-brown soil suspensions (clay concentration of 30 g kg-1) equilibrated with KNO3 solutions of various concentrations clearly demonstrated that the more dilute the solution, the lower the TFS, and the larger the relative conductivity of the suspensions at high field strengths. The results for yellow-brown soil suspensions with different clay concentrations indicated that as the clay concentration increased, the low field electrical conductivity, EC0, also increased, but the TFS decreased, and the Wien effect increased.展开更多
The electrical conductivities (ECs) of suspensions containing 25 and 30 g kg-1 solids prepared from theelectrodialyzed clay fraction (＜ 2 μm in diameter) of latosol, yellow-brown soil, and black soil, dispersed inva...The electrical conductivities (ECs) of suspensions containing 25 and 30 g kg-1 solids prepared from theelectrodialyzed clay fraction (＜ 2 μm in diameter) of latosol, yellow-brown soil, and black soil, dispersed invarious nitrate solutions having concentrations of 1 × 10-4/z mol L-1, where z is the valence, and in distilledwater, were measured at field strengths ranging from 14 kV cm-1 to 210 kV cm-1. On the basis of analysesof the charge density and exchangeable ion composition on the surfaces of soil particles in the suspensions,and of the characters of the EC-field strength curves of the various suspensions, it was inferred that theincrement of EC (△EC) and/or relative electrical conductivity (REC) can indicate the bonding strengthbetween cations and soil particles. The bonding strengths of various cations with the soils diminished in theorder: K+ ＞ Zn2+ ＞ Mg2+ ＝ Ca2+ ＞ Na+ for latosol, Ca2+ ＞ Zn2+ ＞ Mg2+ ＝ K+ ＞ Na+ for yellow-brownsoil, and Zn2+ ＞Ca2+ ＞ Mg2+ ＞ K+ ＞ Na+ for black soil.展开更多
Suspensions of a latosol with a clay concentration of 30 g kg-1 were prepared from electrodialyzed clay fractions, less than 2 μm in diameter, five nitrate solutions with a concentration of 1 × 10-4/z mol L-1,wh...Suspensions of a latosol with a clay concentration of 30 g kg-1 were prepared from electrodialyzed clay fractions, less than 2 μm in diameter, five nitrate solutions with a concentration of 1 × 10-4/z mol L-1,where z is the valence, and five sodium salt solutions with a concentration of 3.3 × 10-5/z mol L-1. The direct current (DC) electrical conductivities (ECs) of the colloidal suspensions were measured at a constant temperature of 25 ℃, using a newly established method of measuring the Wien effect in soil suspensions at field strengths ranging from 13.5 to 150 kV cm-1, to determine their electrical conductivity-field strength relationships and to infer the order of the bonding strength (retaining force) between soil particles and various ions. The measurements with the latosol suspensions in NaNO3, KNO3, Ca(NO3)2, Mg(NO3)2 and Zn(NO3)2 solutions resulted in increments of the suspension ECs, △ECs, of 7.9, 5.0, 7.1, 7.0 and 5.8μS cm-1,respectively, when the applied field strength increased from 14.5 to 142 kV cm-1. As for the suspensions in NaNO3, NaCl, Na2SO4, Na3PO4 and Na3AsO4 solutions, the △ECs were 6.2, 5.3, 4.1, 4.0 and 3.7μS cm-1,respectively, when the applied field strength increased from 13.5 to 90 kV cm-1. Thus, it can be deduced that the retaining forces of the clay fraction of the latosol for the cations were in the descending order K+ ＞Zn2+ ＞ Mg2+ ≥ Ca2+ ＞ Na+, and for the anions in the descending order H2AsO-4 ＞ H2PO-4 ≥ SO42- ＞ Gl- ＞ NO-3.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12125509,12222514,11961141003,and 12005304)National Key Research and Development Project(No.2022YFA1602301)+1 种基金CAST Young Talent Support Planthe CNNC Science Fund for Talented Young Scholars Continuous support for basic scientific research projects。
文摘The Moon provides a unique environment for investigating nearby astrophysical events such as supernovae.Lunar samples retain valuable information from these events,via detectable long-lived“fingerprint”radionuclides such as^(60)Fe.In this work,we stepped up the development of an accelerator mass spectrometry(AMS)method for detecting^(60)Fe using the HI-13tandem accelerator at the China Institute of Atomic Energy(CIAE).Since interferences could not be sufficiently removed solely with the existing magnetic systems of the tandem accelerator and the following Q3D magnetic spectrograph,a Wien filter with a maximum voltage of±60 kV and a maximum magnetic field of 0.3 T was installed after the accelerator magnetic systems to lower the detection background for the low abundance nuclide^(60)Fe.A 1μm thick Si_(3)N_(4) foil was installed in front of the Q3D as an energy degrader.For particle detection,a multi-anode gas ionization chamber was mounted at the center of the focal plane of the spectrograph.Finally,an^(60)Fe sample with an abundance of 1.125×10^(-10)was used to test the new AMS system.These results indicate that^(60)Fe can be clearly distinguished from the isobar^(60)Ni.The sensitivity was assessed to be better than 4.3×10^(-14)based on blank sample measurements lasting 5.8 h,and the sensitivity could,in principle,be expected to be approximately 2.5×10^(-15)when the data were accumulated for 100 h,which is feasible for future lunar sample measurements because the main contaminants were sufficiently separated.
基金Project(Nos.49771046 and 49831005)supported by the National Natural Science Foundation of China.
文摘The electrical conductivity of suspensions and their supernatants from the electrodialyzed clay fractions of latosol, yellow-brown soil and black soil equilibrated with nitrate solutions were determined at different field strengths using a short high-voltage pulse apparatus to demonstrate the Wien effect in soil suspensions and to investigate factors affecting it. It was found that Wien effect was much stronger in suspensions with a clay content of 30 g kg-1 from the soils equilibrated with a 1 × 10-4 KNO3 solution than in their supernatants.The threshold field strength (TFS), at which the relative conductivity is equal to 1.05, i.e., the Wien effect begins to be obvious, of the yellow-brown soil suspensions (clay content of 30 g kg-1) equilibrated with different nitrate solutions of a concentration of 1 × 10-4/z mol L-1 , where z is the valence, varied with the type of nitrates, being lowest for NaNO3 (47 kV cm-1) and highest for Ca(NO3)2 (98 kV cm-1). At high field strengths (larger than 130 kV cm-1), the relative conductivities of yellow-brown soil suspensions containing different nitrates diminished in the order: NaNO3 ＞ KNO3 ＞ Mg(NO3)2 ＞ Zn(NO3)2 ＞ Ca(NO3)2. The rates and intensities of the Wien effect in the suspensions of the three soils equilibrated with 5 × 10-5 molL-1 Ca(NO3)2 solution were in the order of the yellow-brown soil ＞ the latosol ＞ the black soil. The results for the yellow-brown soil suspensions (clay concentration of 30 g kg-1) equilibrated with KNO3 solutions of various concentrations clearly demonstrated that the more dilute the solution, the lower the TFS, and the larger the relative conductivity of the suspensions at high field strengths. The results for yellow-brown soil suspensions with different clay concentrations indicated that as the clay concentration increased, the low field electrical conductivity, EC0, also increased, but the TFS decreased, and the Wien effect increased.
基金Project(Nos.49771046 and 49831005)supported by the National Natural Science Foundation of China and the Center for International Cooperation,Ministry of Foreign Affairs,State of Israel.
文摘The electrical conductivities (ECs) of suspensions containing 25 and 30 g kg-1 solids prepared from theelectrodialyzed clay fraction (＜ 2 μm in diameter) of latosol, yellow-brown soil, and black soil, dispersed invarious nitrate solutions having concentrations of 1 × 10-4/z mol L-1, where z is the valence, and in distilledwater, were measured at field strengths ranging from 14 kV cm-1 to 210 kV cm-1. On the basis of analysesof the charge density and exchangeable ion composition on the surfaces of soil particles in the suspensions,and of the characters of the EC-field strength curves of the various suspensions, it was inferred that theincrement of EC (△EC) and/or relative electrical conductivity (REC) can indicate the bonding strengthbetween cations and soil particles. The bonding strengths of various cations with the soils diminished in theorder: K+ ＞ Zn2+ ＞ Mg2+ ＝ Ca2+ ＞ Na+ for latosol, Ca2+ ＞ Zn2+ ＞ Mg2+ ＝ K+ ＞ Na+ for yellow-brownsoil, and Zn2+ ＞Ca2+ ＞ Mg2+ ＞ K+ ＞ Na+ for black soil.
基金Project supported by the National Natural Science Foundation of China (Nos. 49771046 and 49831005) the Center for International Cooperation, Ministry of Foreign Affairs, State of Israel.
文摘Suspensions of a latosol with a clay concentration of 30 g kg-1 were prepared from electrodialyzed clay fractions, less than 2 μm in diameter, five nitrate solutions with a concentration of 1 × 10-4/z mol L-1,where z is the valence, and five sodium salt solutions with a concentration of 3.3 × 10-5/z mol L-1. The direct current (DC) electrical conductivities (ECs) of the colloidal suspensions were measured at a constant temperature of 25 ℃, using a newly established method of measuring the Wien effect in soil suspensions at field strengths ranging from 13.5 to 150 kV cm-1, to determine their electrical conductivity-field strength relationships and to infer the order of the bonding strength (retaining force) between soil particles and various ions. The measurements with the latosol suspensions in NaNO3, KNO3, Ca(NO3)2, Mg(NO3)2 and Zn(NO3)2 solutions resulted in increments of the suspension ECs, △ECs, of 7.9, 5.0, 7.1, 7.0 and 5.8μS cm-1,respectively, when the applied field strength increased from 14.5 to 142 kV cm-1. As for the suspensions in NaNO3, NaCl, Na2SO4, Na3PO4 and Na3AsO4 solutions, the △ECs were 6.2, 5.3, 4.1, 4.0 and 3.7μS cm-1,respectively, when the applied field strength increased from 13.5 to 90 kV cm-1. Thus, it can be deduced that the retaining forces of the clay fraction of the latosol for the cations were in the descending order K+ ＞Zn2+ ＞ Mg2+ ≥ Ca2+ ＞ Na+, and for the anions in the descending order H2AsO-4 ＞ H2PO-4 ≥ SO42- ＞ Gl- ＞ NO-3.
