The concentration quenching and crystallographic sites of Eu^(2+) in Ca_2BO_3Cl

A yellow phosphor, Ca2BO3CI：Eu2＋, is prepared by the high-temperature solid-state method. Under the condition of excitation sources ranging from ultraviolet to visible light, efficient yellow emission can be observed. The emission spectrum shows an asymmetrical single intensive band centred at 573 nm, which corresponds to the 4f65dl→4f7 transition of Eu2＋. Eu2＋ ions occupy two types of Ca2＋ sites in the Ca2BO3C1 lattice and form two corresponding emission centres, respectively, which lead to the asymmetrical emission of Eu2＋ in Ca2BO3C1. The emission intensity of Eu2＋ in Ca2BO3C1 is influenced by the Eu2＋ doping concentration. Concentration quenching is discovered, and its mechanism is verified to be a dipole-dipole interaction. The value of the critical transfer distance is calculated to be 2.166 nm, which is in good agreement with the 2.120 nm value derived from the experimental data.

Adsorption equilibrium, kinetics, and dynamic separation of Ca2+ and Mg2+ ions from phosphoric acid–nitric acid aqueous solution by strong acid cation resin

The separation of Ca2+and Mg2+ions from phosphoric acid-nitric acid aqueous solution is very significant for the neutralization process of nitrophosphate fertilizer.This paper studied the adsorption equilibrium,kinetics,and dynamic separation of Ca2+and Mg2+ions by strong acid cation resin,and the effects of phosphoric acid and nitric acid on the adsorption process were investigated.The results reveal that the adsorption process of Ca2+and Mg2+ions in pure water on resin is in good agreement with the Langmuir isotherm model and their maximal adsorption capacities are 1.86 mmol·g-1 and 1.83 mmol·g-1,respectively.The adsorption kinetics of Ca2+and Mg2+ions on resin fits better with the pseudo-first-order model,and the adsorption equilibrium in pure water is reached within 10 min contact time,while at the present of phosphoric acid,the adsorption rate of Ca2+and Mg2+ions on resin will go down.The dynamic separation experiments demonstrate that the designed column adsorption is able to undertake the separation of metal ions from the mix acids aqueous solution,but the dynamic operation should control the flow rate of mix acid solution.Besides nitric acid solution was proved to be effective to completely regenerate the spent resin and achieve the recyclable operation of separation process.

Effects of Ca2+concentrations on accumulations of mineral elements in the components of Pteroceltis tatarinowii

The bark of Pteroceltis tatarinowii is a raw material for manufacturing Xuan Paper. The effects of Ca2+ concentrations on the accumulation of mineral elements in the bark, leaf and root of Pteroceltis tatarinowii were studied under controlled condi-tions. The types of Hoagland nutrient solution with three Ca2+ concentrations levels (200, 400 and 600 靏g-1) and a control (without Ca2+) were designed to culture Pteroceltis tatarinowii. After 6 months, contents of seven mineral elements including Ca, K, Mg, Mn, Zn, Cu and Na in the root, leaf and bark were analyzed. The results indicated that Ca accumulations content in the root, leaf and bark had positively relation with Ca2+ concentrations (200, 400, 600 靏g-1), and the order of the Ca content in the three components was root】leaf】bark. Ca content in the root treated with 600 靏g-1 Ca2+ concentrations was 5.5 times as high as that of the control, and about 1.4 times as high as that of the root treated in 200 and 400 靏/g Ca2+ concentrations respectively. On the contrary, K and Mg contents in the root, leaf and bark were negatively related to Ca2+ concentrations, especially in the bark, and their accumulation trend followed the order of leaf】root】bark. K content in the bark treated with 600 靏g-1 Ca2+ con-centrations was 39.3% of that of the control, and was 79.0% and 91.8% of that of the bark treated with 200 靏g-1 and 400靏g-1 Ca2+ concentrations respectively; Mg content in the bark treated with 600 靏g-1 Ca2+ concentrations was 23.4% of that of the control, and was 27.1% and 35.4% of that of the bark treated with 200 and 400 靏g-1 Ca2+ concentrations respectively. Com-pared with the control, the general tendency of Mn, Zn and Cu content decreased with increasing of Ca2+ concentrations and their contents were in the order: root】leaf】bark. Based on the results of this study, the experiment has been useful for providing academic bases in improving the bark quality of Pteroceltis tatarinowii on non-limestone soil.

The Effects of Etimicin and Gentamicin on Renal Endoplasmic Reticulum ^(45)Ca^(2+)-Uptake and Ca^(2+)-Mg^(2+)-ATPase Activity

Objective: To study the effects of etimicin (EM) and gentamicin (GM) on renal endoplasmic reticulum 45 Ca 2+ uptake and Ca 2+ Mg 2+ ATPase activity. Methods: Using 45 Ca 2+ incorporation technique and peacock blue spectrophotometry respectively. Results: EM and GM (≥3.4×10 4 mol·L 1 ) inhibited endoplasmic reticulum 45 Ca 2+ uptake (the rate of inhibition: ≥17.4% and ≥25.5%, respectively); EM and GM (3.4×10 2 mol·L 1 ) inhibited Ca 2+ Mg 2+ ATPase activity (the rate of inhibition: 24.2% and 29.2%, respectively). Conclusion: At high concentration, EM and GM elevated intracellular calcium which may be related to their nephrotoxicity.

Refinement and strengthening mechanism of Mg−Zn−Cu−Zr−Ca alloy solidified under extremely high pressure

Mg−Zn−Cu−Zr−Ca samples were solidified under high pressures of 2-6 GPa.Scanning electron microscopy and electron backscatter diffraction were used to study the distribution of Ca in the microstructure and its effect on the solidification structure.The mechanical properties of the samples were investigated through compression tests.The results show that Ca is mostly dissolved in the matrix and the Mg_(2)Ca phase is formed under high pressure,but it is mainly segregated among dendrites under atmospheric pressure.The Mg_(2)Ca particles are effective heterogeneous nuclei ofα-Mg crystals,which significantly increases the number of crystal nuclei and refines the solidification structure of the alloy,with the grain size reduced to 22μm at 6 GPa.As no Ca segregating among the dendrites exists,more Zn is dissolved in the matrix.Consequently,the intergranular second phase changes from MgZn with a higher Zn/Mg ratio to Mg7Zn3 with a lower Zn/Mg ratio.The volume fraction of the intergranular second phase also increases to 22%.Owing to the combined strengthening of grain refinement,solid solution,and dispersion,the compression strength of the Mg-Zn-Cu-Zr-Ca alloy solidified under 6 GPa is up to 520 MPa.

Defective maintenance of intracellular Ca^(2+) homeostasis is linked to increased muscle fatigability in the MG29 null mice

Mitsugumin 29 (MG29) is a transmembrane protein that is normally found in the triad junction of skeletal muscle. Our previous studies have shown that targeted deletion of mg29 from the skeletal muscle resulted in abnormality of the triad junction structure, and also increased susceptibility to muscle fatigue. To elucidate the basis of these effects, we investigated the properties of Ca2+-uptake and -release in toxin-skinned Extensor Digitorium Longus (EDL) muscle fibers from control and mg29 knockout mice. Compared with the control muscle, submaximal Ca2+-uptake into the sarcoplasmic reticulum (SR) was slower and the storage of Ca2+ inside the SR was less in the mutant muscle, due to increased leakage process of Ca2+ movement across the SR. The leakage pathway is associated with the increased sensitivity of Ca2+/caffeine -induced Ca2+ release to myoplasmic Ca2+. Therefore, the increased fatigability of mutant EDL muscles can result from a combination of a slowing of Ca2+ uptake, modification of Ca2+-induced Ca2+ release (CICR), and a reduction in total SR Ca2+ content.

Influence of thermomechanical processing on microstructure,mechanical and strain hardening properties of single-phase Mg-4Li-0.5Ca alloy for structural application

The single-phase Mg-4Li-0.5Ca alloy was rolled at three different temperatures(250,300 and 350℃)and followed by annealing at 200°C for 10 min.To evaluate the mechanical properties,the tensile test was conducted at a constant strain rate of 10^(-3)s^(-1).Factors influencing the tensile strength and strain hardening properties were assessed by microscopy,XRD and EBSD analysis.Besides,Kocks-Mecking plots(K-M)were used to determine the different stages of strain hardening exhibited by the variously processed Mg-4Li-0.5Ca alloy test specimens.The ultimate tensile strength has decreased as hot-rolling temperature in creases with increased ductility.The strain hardening properties such as hardening capacity(Hc),strain hardening exponent(n)are increased significantly with an increase in hot rolling temperature and subsequent annealing.

EFFECTS OF CALDESMON, CALPONIN, AND TROPOMYOSIN ON THE MG^(2+)-ATPase ACTIVITIES OF SMOOTH MUSCLE MYOSIN

Objective To test whether in the absence of actin, actin-binding proteins such as caldesmon, calponin, and tropomyosin interact with the myosin of unphosphorylation, Ca 2+ -dependent phosphorylation (CDP), and Ca 2+ -independent phosphorylati-on (CIP) and stimulate myosin Mg 2+ -ATPase activities. Methods Mg 2+ -ATPase activities were measured to evaluate the effects of caldesmon, calponin, and tropomyosin on the myosin in unphosphorylation, CDP by myosin light chain kinase (MLCK), and CIP by MLCK. Results (1) At different incubation-time, i.e., 5, 10, 20, 40, and 60 minutes, the highest Mg 2+ -ATPase activity was ob-served when myosin was in the state of CDP, the medium was CIP of myosin, and the lowest was the unphosphorylated myosin. (2) In the absence of caldesmon, calponin, and tropomyosin, the Mg 2+ -ATPase activities from high to low were in the following order: CDP, CIP, and unphosphorylated myosin. However, in the presence of caldesmon, calponin, and tropo-myosin, the order of relative value of Mg 2+ -ATPase activities from high to low was unphosphorylated, CIP, and CDP of myosin respectively compared to the corresponding controls. Conclusions The results propose that caldesmon, calponin, and tropomyosin are capable of stimulating Mg 2+ -ATPase activity of smooth muscle myosin in Ca 2+ -independent manner, since Ca 2+ is not obligating for the stimulating effects of the three proteins. The common characteristic of the three proteins is that when myosin activities are low, their activations are relatively strong and this property might be involved in smooth muscle tension keeping.

Relationship of Intracellular Free Ca^(2+) Concentration and Calcium-activated Chloride Channels of Pulmonary Artery Smooth Muscle Cells in Rats under Hypoxic Conditions

To investigate the relationship between intracellular free Ca^2＋ concentration （[Ca^2＋ ]i ） and calcium-activated chloride （Clca） channels of pulmonary artery smooth muscle cells （PASMCs） in rats under acute and chronic hypoxic conditions, acute hypoxia-induced contraction was observed in rat pulmonary artery by using routine blood vascular perfusion in vitro. The fluorescence Ca^2＋ indicator Fura-2/AM was used to observe [Ca^2＋ ]i of rat PASMCs under normal and chronic hypoxic condition. The effect of Clca channels on PASMCs proliferation was assessed by MTT assay. The Clca channel blockers niflumic acid （NFA） and indaryloxyacetic acid （IAA-94） exerted inhibitory effects on acute hypoxia-evoked contractions in the pulmonary artery. Under chronic hypoxic condition, [Ca^2＋ ]i was increased. Under normoxic condition, [Ca^2＋ If was （123.634-18.98） nmol/ L, and in hypoxic condition, [Ca^2＋]i wag （281. 754-16.48） nmol/L （P〈0. 01）. Under normoxic condition, [Ca^2＋ ]i showed no significant change and no effect on Clca channels was observed （P〉 0. 05）. Chronic hypoxia increased [Ca^2＋ ]i which opened Clca channels. The NFA and IAA-94 blocked the channels and decreased [Ca^2＋ ]i from （281.75± 16.48） nmot/L to （117.66 ±15.36） nmol/L （P〈0.01）. MTT assay showed that under chronic hypoxic condition NFA and IAA-94 decreased the value of absorbency （A value） from 0. 459±0. 058 to 0. 224±0. 025 （P〈0. 01）. Hypoxia increased [Ca^2＋ ]i which opened Cl~ channels and had a positive-feedback in [Ca^2＋ ]i. This may play an important role in hypoxic pulmonary hypertension. Under chronic hypoxic condition, Clca channel may play a part in the regulation of proliferation of PASMCs.

Improvement of Water and Wastewater Treatment Process Using Various Sound Waves—A Consideration from the Viewpoint of Frequency

Application of sound waves is one of the novel techniques for the improvement of water treatment process. In this study, various sound waves such as 1) ultrasonic wave, 2) music box, and 3) windbell were irradiated to water and wastewater for removing contaminants such as nitrate, phosphorus and BOD/COD. As a result, a possibility of improvement of water and wastewater treatment process using sound waves with various frequencies was proposed.

FOLLICULO-STELLATE CELLS OF THE RAT ANTERIOR PITUITARY RESPONDED TO ANGIOTENSIN Ⅱ BY INCREASING INTRACELLULAR Ca^(2+) CONCENTRATION

Objective The main purpose of this study was to investigate whether the folliculo stellate cells (FSC) respond to angiotensin(Ang)Ⅱ by increasing intracellular free Ca 2+ concentration ([Ca 2+ ]i),and where the origin of Ca 2+ mobilization is if that has occurred.Methods Pituitary cells in primary culture were prepared from male Wister rats(250g) by a conventional method and cultured in MEM supplemented with 4% normal rat serum.After 2 days in culutre,cells were loaded with 1 μmol/L fura PE3/AM for 1 h and subjected to a Ca 2+ imaging experiment with Quanti Cell 700 system.Excitation wavelengths of 340 and 380 nm were selected by means of a computer controlled filterwheel.Results The [Ca 2+ ]i of FSC in the rat anterior pituitary was elevated by Ang Ⅱ.The elevation of [Ca 2+ ]i of FSC induced by 0.1,1.0,10 and 100 nmol/L Ang Ⅱ was (56.33±6.18)( ±s ),(117.07±36.07),(175.59±40.01) and (216.02±11.52) nmol/L,respectively.The increase of [Ca 2+ ]i of FSC induced by 100 nmol/L Ang Ⅱ was not influenced by the medium without Ca 2+ (0Ca),but significantly suppressed by thapsigargin(TG),an inhibitor of ATPase.The rate of responsive FSC to Ang Ⅱ (100 nmol/L) was 61.84% which was obviously higher than that of pituitary endocrine cells(43.49%).Conclusion The present experiment demonstrates that the FSC in the rat anterior pituitary responds to Ang Ⅱ by increasing [Ca 2+ ]i,which raises the possibility that Ang Ⅱ released from either lactotrophs or gonadotrophs affects FSC through paracrine mechanism.The elevation of [Ca 2+ ]i induced by Ang Ⅱ presents a dosage dependent relation, and is possibly because of the release of Ca 2+ from an intracellular Ca 2+ pool(s).Fashions of Ca 2+ release are relative to the concentration of Ang Ⅱ.The results indicate that Ang Ⅱ functions as a paracrine factor among pituitary cells including FSC.

EFFECTS OF ACUPUNCTURE ON INTRACELLULAR FREE CALCIUM AND MAGNESIUM CONCENTRATIONS IN CARDIAC MYOCYTES OF HEMORRHAGIC HYPOTENSION RABBITS

The effects of electroacupuncture on hypotension and the concentrations of intracellular free calcium([Ca2+]i) and free magnesium([ Mg2+]i) in cardiac myocyte of rabbit were studied. The hemorrhapic hypotension was induced by losing blood from femoral artery of rabbit. [Ca2+]i and [Mg2+]i were determined by use of AN-CM-COM cation measurment system and the Fura-2-AM and Furaptra-AM ionic probes. [Ca2+]i was significantly decreased, while [Mg2+]i was increased, and the ratio of [Ca2+]i / [ Mg2+]i was decreased as the blood pressure went down with losing blood. The blood pressure and [ Ca2+ ] i of treatment group rabbits were significantly raised by electroacupuncturing the points of "Renzhong "and "Chengjiang", and the ratio of [ Ca2+] i / [ Mg2+]i was increased. The [Ca2+]i and [ Mg2+]i in cardiac myocyte of normal rabbits had no clear changes by electroacupuncture. It suggested that intracellular free calcium and magnesium ion in cardiac myocyte may play an important role in regulating blood pressure by acupunoture.

Propofol regulates Ca～(2+),Mg～(2+),Cu～(2+) and Zn～(2+) balance in the spinal cord after ischemia/reperfusion injury

This study assessed concentrations of Ca2＋, Mg2＋, Cu2＋ and Zn2＋ in blood serum and spinal cord tissues, as well as the possible mechanisms by which propofol may protect spinal cord tissues during ischemia/reperfusion injury. With prolonged duration of ischemia/reperfusion injury, serum Ca2＋ and Cu2＋ concentrations gradually increased, but Mg 2＋ and Zn2＋ concentrations gradually decreased. Seven days after spinal cord injury, changes in Ca2＋, Mg2＋, Cu2＋ and Zn2＋ concentrations were significant. After 7 days of reperfusion, changes in the concentrations of Ca2＋, Mg2＋, Cu2＋ and Zn2＋ in spinal cord homogenates were consistent with those in the serum. After propofol treatment, no significant changes in Ca2＋, Mg2＋, Cu2~ and Zn2＋ concentrations in serum and spinal cord homogenates were noted during ischemia/reperfusion injury. These findings suggest that propofol exerts protective effects against spinal cord injury by stabilizing or recovering metal ion balance in ischemic regions.

Mechanical properties and electronic structures of MgCu_2, Mg_2Ca and MgZn_2 Laves phases by first principles calculations

Mechanical properties and electronic structure of MgCu2, Mg2 Ca and MgZn2 phases were investigated by means of first principles calculations from CASTEP program based on density functional theory（DFT）. The calculated lattice parameters are in good agreement with the experimental and literature values. The calculated heat of formation and cohesive energies showed that MgCu2 has the strongest alloying ability and structural stability. Elastic constants of MgCu2, Mg2 Ca and MgZn2 were calculated, and the bulk moduli, shear moduli, elastic moduli and Poisson ratio were derived. The calculated results show that MgCu2, Mg2 Ca and MgZn2 are all ductile phases. Among the three phases, MgCu2 has the strongest stiffness and the plasticity of MgZn2 phase is the best. Melting points of the three phases were predicted using cohesive energy and elastic constants. Density of states（DOS）, Mulliken population, electron occupation number and charge density difference were discussed. Finally, Debye temperature was calculated and discussed.

不同Ca2+源、Mg2+源对固态发酵产纳豆激酶的影响

以枯草芽孢杆菌为试验菌株,研究不同Ca^2+源、Mg^2+源对固态发酵产纳豆激酶的影响。通过添加不同Ca^2+源、Mg^2+源的方式发酵制备纳豆,采用纤维蛋白平板法测定纳豆激酶活力,稀释涂布平板计数法测定纳豆中的活菌数,通过纳豆的颜色、香气、滋味和组织形态4个指标进行感官评价,分析不同的离子源对固态发酵产纳豆激酶的影响,筛选最佳的Ca^2+源、Mg^2+源制备纳豆。结果表明:在3种不同Ca^2+源中,CaCl 2为最佳Ca^2+源,添加量为0.04%(质量分数),制备的纳豆激酶活力最高,达到7786 IU/g,比空白组酶活力提高了57%,菌体量为5.4×107 CFU/g;3种不同Mg^2+中,MgSO4为Mg 2+源、添加量为0.72%(质量分数),制备的纳豆激酶活力最高,达到10591 IU/g,相比空白组提高了71%,菌体量达到7.8×10^7 CFU/g。

纳滤膜脱除稀盐酸中Ca2+和Mg2+

采用纳滤膜技术处理含Ca^2+、Mg^2+的稀盐酸溶液,实现稀盐酸的回收。讨论了操作时间、盐含量、盐种类、酸度、运行压力、进料流量、进料温度等工艺条件对Ca^2+和Mg^2+脱除率和膜通量的影响,获得了适宜的操作条件;同时比较了单组分与双组分无机盐纯水溶液及酸性溶液的性能,研究了在不同条件下Ca^2+和Mg^2+的脱除效果。结果表明:在采用纳滤膜处理含双组分钙、镁离子(质量比为1∶1)总的质量分数分别为3×10^−4、2×10^−3和3×10^−3的稀盐酸溶液(wHCl=3%)时,Ca^2+的脱除率为80%~90%,Mg^2+的脱除率达到90%~100%;纳滤膜的适宜操作条件为压力0.4 MPa、温度30℃、进料流量396 L/h;酸性条件下更有利于Ca^2+和Mg^2+脱除,相对于中性条件下脱除率提高了25%左右,因此纳滤膜可应用于酸溶液的净化与回收利用。

Behavior of CaO and Calcium in pure Magnesium

Mg alloys exhibit a number of good properties such as low density, good castability and high specific strength. However, molten Mg and Mg alloys are ignited without the melt protective gases during melting and casting process due to their high reactivity. The purpose of this study is to investigate effects of Ca and CaO on pure Mg through microstructure observation, ignition test and phase analysis. With increasing Ca and CaO contents, the ignition resistance of Ca or CaO added pure Mg is increased and the grains are refined. As results of XRD and EDS, CaO is reduced to Ca in CaO added pure Mg. Mg2Ca phase is formed even in 0.1 wt.%CaO added pure Mg by reduction mechanism, while Mg2Ca phase is formed over 1.35 wt.% Ca added pure Mg.

Changes in erythrocyte membrane ATPases and plasma lipid peroxides in upper abdominal surgery under intravenous procaine-balanced anesthesia

AIM To observe the changes in erythrocyte membrane ATPases and plasma lipid peroxides (LPO) patients with in abdominal surgery under intravenous procaine-balanced anesthesia.METHODS By determining the ATPase activities of erythrocyte membrane, effects of upper abdominal surgery under intravenous procaine-balanced anesthesia on the function of erythrocytes were observed in 15 patients undergoing cholecystectomy and gastrectomy (5 males and 10 females, aged 45.9±10.20 years and weighed 60.60kg±11.93kg). All patients were free from severe renal, hepatic, pulmonary, cardiac, metabolic and endocrinological diseases and acute infection for at least 2 weeks before surgery. Patients receiving any drug known to affect carbohydrate metabolism prior to anesthesia were excluded from the study.RESULTS Erythrocyte membrane Na+, K+-ATPase, Mg2+-ATPase, Ca2+, Mg2+-ATPase activities were not significantly changed 60min-90min after incision as compared with 30min before anesthesia, but were decreased markedly 10min and 24 hours after completion of operation (P＜0.01). Plasma lipid peroxides (LPO) were increased significantly 24 hours after surgery (P＜0.01) following an initially marked but transient reduction. Plasma LPO changes were not correlated with erythrocyte membrane ATPase activities, r=-0.0396, -0.0097 and 0.4383, respectively (P＞0.05).CONCLUSION Abdominal surgical trauma under intravenous procaine-balanced anesthesia may be associated with the decreased ATPase activities of erythrocyte membrane and increased LPO in plasma.

A Brief Study on pH, Exchangeable Ca²⁺and Mg²⁺in Farmlands under Tobacco-Rice Rotation in Xuancheng City of South Anhui

pH, exchangeable Ca2+ and Mg2+ of soil can influence the yield and quality of flue-cured tobacco. Xuancheng city is the dominant tobacco-planting region in Anhui province since 2008. A general soil survey was conducted in Xuancheng city to understand the current situations of pH, exchangeable Ca2+ and Mg2+ of farmlands under tobacco-rice rotation and to decide whether continuous applying dolomite powders to abate soil acidification. In total 124 topsoil samples (0-20 cm) were collected from the typical farmlands and soil pH, exchangeable Ca2+ and Mg2+ were measured. The results showed that soil pH and Ca2+ and Mg2+ in Xuancheng city were generally in the suitable grades, pH ranged from 4.56 to 8.42 with an average of 5.87, exchangeable Ca2+ ranged from 1.01 cmol(1/2Ca2+) kg-1 to 100.55 cmol(1/2Ca2+) kg-1 with an average of 11.07 cmol(1/2Ca2+) kg-1, and exchangeable Mg2+ ranged from 0.14 cmol(1/2Mg2+) kg-1 to 2.86 cmol(1/2Mg2+) kg-1 with an average of 0.81 cmol(1/2Mg2+) kg-1, all spanned from the low grades to the high grades. To the whole Xuancheng city, 37.10%, 62.10% and 72.58% of the surveyed farmlands were in the low grades of pH, exchangeable Ca2+ and Mg2+, respectively, while 52.42%, 25.00% and 20.97% of the farmlands were in the suitable grades, respectively. pH had an extremely significantly positive Napierian logarithm correlation with exchangeable Ca2+ and an extremely significantly positive power correlation with exchangeable Mg2+. In total about 338.2 kg·hm-2 of Ca2+ and 202.4 kg·hm-2 of Mg2+ are annually input into the farmlands, while about 110.4 kg·hm-2 of Ca2+ and 7.4 kg·hm-2 of Mg2+ are annually moved out from the farmlands, exchangeable Ca2+ and Mg2+ were annually increased by 225.2 kg·hm-2 and 187.6 kg·hm-2 in the farmlands, respectively. It is necessary to monitor the farmlands dynamically in order to decide whether continuous applying dolomite powders which should be dependent upon the specific conditions of individual farmlands.

Distribution of Exchangeable Calcium，Magnesium and Potassium as Affected by Fertilizer Application to Red Soil

A leaching experiment was carried out with repacked soil columns in laboratory to stndy the leachingprocess of a red soil derived from sandstone as affected by warions fertilization practices. The treatments wereCK (as a control), CaCO_3, CaSO_4, MgCO_3, Ca(H_2PO_4)_2, Urea, KCl, Mnltiple (a mixture of the above-mentioned fertilizers), and KNO_3. The fertilizers were added to the bare surface of the soil columns, andthen the columns were leached with 120 mL deionized water daily through peristaltic pumps over a periodof 92 days. At the end of leaching process, soils were sampled from different depths of the soil profiles, i.e.,0-5 cm, 5-10 cm, 10-20 cm, 20-40 cm, and 40-60 cm. The results showed when applying Ca, Mg, andK to the bare surface of the soil columns, exchangeable Ca￣(2+), Mg￣(2+), and K￣+ in the upper layer of thesoil profile increased correspondingly, with an extent depending mainly on the application rates of Ca, Mg,and K and showing a downward trend. CaCO_3, CaSO_4, MgCO_3, and Ca(H_2PO_4)_2 treatments had scarcelyany effect on movement of exchangeable K￣+, while CaCO_3, and CaSO_4 treatments significantly promotedthe downward movement of exchangeable Mg￣(2+) although these two treatments had no obvious effect onleaching losses of Mg. The fact that under Urea treatment, exchangeable Ca￣(2+) and Mg￣(2+) were higheras compared to CK treatment showed urea could prevent leaching of exchangeable Ca￣(2+) and Mg￣(2+). Theobvious downward movement of exchangeable Ca￣(2+) and Mg￣(2+) was noticed in KCl treatment. In Multipletreatment, the downward movement of exchangeable Ca￣(2+) and Mg￣(2+) was evident, while that of K￣+ was lessevident. Application of KNO_3 strongly promoted the downward movement of exchangeable Ca￣(2+) and Mg￣(2+)in the soil profile.