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1.
Nearly a century of mining activities upstream have contaminated Lake Coeur d’Alene and its tributaries with Pb, Zn, and other heavy metals. Heavy metal concentrations in sediments of the Coeur d’Alene watershed have been shown to be inversely proportional to the sediment size fraction; thus, analysis on a very small scale is essential to determine the mobility and stability of heavy metals in this environment. Micron-scale synchrotron-based methods were used to determine the association of heavy metals with solid phases in sediments of the Coeur d’Alene River. Bulk X-ray diffraction (XRD), extended X-ray absorption fine structure spectroscopy, and synchrotron-based microfocused XRD combined with microfocused X-ray fluorescence mapping indicate the presence of crystalline Pb- and Zn-bearing mineral phases of dundasite [Pb2Al4(CO3)4(OH)8·3H2O], coronadite [PbMn8O16], stolzite [PbWO4], mattheddleite [Pb10(SiO4)3.5(SO4)2Cl2], bindheimite [Pb2Sb2O7], and smithsonite [ZnCO3]. Likely phases for Zn and Pb adsorption were ferrihydrite, diaspore [AlO(OH)], manganite [Mn(III)O(OH)], muscovite [KAl2(Si3Al)O10(OH,F)2], biotite [K(Fe,Mg)3AlSi3O10(F,OH)2], and montmorillonite [Na0.3(Al,Mg)2Si4O10(OH)2·8H2O]. The large predominance of Fe and Mn (hydr)oxides over other sorbent minerals suggests that the metal sorption behavior is dominated by these (hydr)oxide phases.  相似文献   

2.
A freshwater wetland at the Experimental Lakes Area in northwestern Ontario stored most of the SO4 2? received annually from precipitation, runoff and experimental additions. The S budget was determined for a small fen spray irrigated with H2SO4 and HNO3. Annual S retention was greatest during the first year of experimental addition of H2SO4 (73% of input in 1983). Retention was lowest (22%) in 1984, a year of lower than average precipitation with a long hot summer. During years with hot, dry summers, SO4 2? was produced from the reoxidation of reduced S compounds in the peat and released to surface waters. The autumn SO4 2? pulse was accompanied by the release of Ca and Mg but was not accompanied by a H+ release as has been detected in eastern Ontario and southern Norway, areas which receive more acidic precipitation.  相似文献   

3.
In this study, photocatalytic degradation of bisphenol A (BPA) was investigated using two types of catalysts (TiO2 and ZnO) with various metal ion concentrations and amounts of added H2O2. A kinetic test was performed to observe the changes of BPA over time under UV irradiation in a photocatalytic reactor. Experimental results demonstrated that degradation efficiency of ZnO was higher than that of TiO2. The degradation rate increased as catalyst dosage increased until reaching optimum dosage, after which degradation rate decreased. The addition of H2O2 improved the degradation efficiency of BPA, with the degradation efficiency increasing with the amount of H2O2. All metal ions, including Fe2+, Ni2+, and Cu2+, inhibited the degradation of BPA by ZnO at natural pH, whereas Fe2+ and Ni2+ enhanced degradation efficiency of BPA at acidic pH. Comparison of BPA degradation with H2O2 only, ZnO/H2O2, Fe2+/H2O2, and ZnO/Fe2+/H2O2 revealed that Fe2+/H2O2 was more efficient than other processes at lower pH (pH?=?3.44), whereas ZnO/H2O2 the most efficient at higher pH (pH?=?6.44). These results indicate that ZnO/H2O2 process was observed to be the most efficient of all processes. Degradation efficiency of BPA by ZnO was also influenced by additional parameters, including H2O2 concentration, metal ions, and solution pH.  相似文献   

4.
The potential for sulfate retention is an important soil feature for buffering of atmospheric acid deposition. We studied the effects of increasing additions of different neutral salts and acids on mobilization and retention of SO4 2- in acid forest soils. Soils containing up to 11 mmol SO4 2- kg-1 were equilibrated with H2O, NaCl, MgCl2, and HCl. Release of SO4 2- was highest with H2O and NaCl additions and lowest when HCl was used. Increasing the ionic strength of the added solutions caused decreasing SO4 2- concentrations in equilibrium solution. Decreasing pH in equilibrium solution was found to be the reason for the decrease in release. Even when the pH was < 4, the SO4 2- release decreased. We assume that this finding resulted from the fact that in the soils studied the SO4 2- sorption was controlled by the high contents of Fe oxides/hydroxides. Experiments with Na2SO4, MgSO4, and H2SO4 demonstrated that the B horizons already containing high amounts of SO4 2- were still able to retain SO4 2-. Sulfate retention increased in the order Na2SO4 < MgSO4 < H2SO4, which corresponds to increasing H+ availability. The higher SO4 2- retention along with MgSO4 compared to Na2SO4 may be caused by higher potential of Mg to mobilize soil acidity compared to Na.  相似文献   

5.
In the current study, the leachability of lead from the PbO-Fe2O3-SiO2-Na2O vitrification system was examined by the application of DIN 38414 S4 and TCLP (Toxicity Characteristic Leaching Procedure) standard leaching tests. Various compositions, containing industrial or artificially created solid waste, were examined. Among the main conclusions from the results obtained was that the initial lead content, expressed as PbO and varied between 4–24% w/w, does not influence directly the release of lead from the vitrified samples. The other oxides, as well as other factors e.g. crystal formation on the glass surface, proved to be more important. Similar data were obtained regarding the content of iron oxide (the initial content of Fe2O3 varied from 30–54% w/w), although in this case the sodium concentrations measured in the leachates were generally found to increase with increasing initial iron oxide content and with the respective formation of crystals. The stoichiometry of lead and sodium, as measured in the leachates, was not constant for all the examined cases, showing that the mechanism of release depends upon the initial compositions and the presence of crystals on the glass surface. Improved results, regarding leachability and homogeneity without the presence of crystallites on the glass surface, were obtained when the initial ratio SiO2/Na2O (% w/w) was 2.33. By maintaining this ratio and when the examined waste was gradually added in the initial composition, the results obtained, concerning sodium concentration and pH values, can be described mathematically, by introducing an appropriate constant factor.  相似文献   

6.
A novel silicate mesoporous material, SBA-15 supported Fe2O3, was synthesized by post-synthesis method via ultrasonic-assisted route. The desulfurization test from a gas mixture containing 0.1 vol% H2S was carried out over SBA-15 supported Fe2O3 in a fixed-bed system at atmospheric pressure and room temperature. The effects of the chemical nature of Fe2O3 and the textural properties of the material on desulfurization capacity were studied. Materials before and after the desulfurization test were characterized using nitrogen adsorption, XRD, TEM, FTIR, XPS, ICP and other standard methods. The characterization results suggest that modification process does not change the two-dimensional hexagonal mesostructure of SBA-15. Iron species disperses inside channels and the outside surface in the crystalline phase of iron oxide. The material with iron content of 31.3 wt% presented highest H2S uptake capacity. Structural properties of the material also play important roles in desulfurization performance besides the catalytic effects of iron oxide. The basic feature of material and enough oxygen supply are benefit for the reaction. SBA-15 supported Fe2O3 can be an effective alternative to capture H2S from gas streams.  相似文献   

7.
Theory and experimental results have shown that neutral salts in the precipitation or supplied to the ground by other means reduce the acidification of soils by acid precipitation. This salt effect is caused by the cation exchange occurring after the entry of the rain water into the soil.The acid components of precipitation consist of H2SO4, HNO3 and HCl and of NH4+ after nitrification in the soil. The magnitude of the salt effect depends on the relative bonding energy of H3O+ and of Ca2+, Mg2+, Na+, K+, NH4+ in the soil as well as on the concentrations of H3O+ and the above cations in the precipitation. The salt effect may be considerable in very acid soils. It decreases with rising pH to become very small or negligible in neutral soils, chiefly due to the increasing bonding energy of H3O+ in this direction.The adverse effect of acid precipitation, therefore, is likely to be less in very acid soils, such as podsols, than in slightly acid and neutral soils with low buffering capacity against pH change. Soil texture and calcite content are very important factors in this respect as fine material and calcite increase the buffering.  相似文献   

8.
Retention of S04 2? was investigated in Galician soils throughout an intense regime of acidification. Experiments consisted of the addition of an H2SO4 solution (pH 2.7) to columns of 6 soils of contrasting properties over 1, 2, or 5 months. Leachates were obtained continuously throughout the experiment for analysis, and analysis made of the solid fractions after 1, 2 or 5 months. The greatest capacities for retention of S04 2? were found in soil developed from serpentine and micaschist; the lowest in soils from granite, slate and sandy sediments. The surface horizons, especially those rich in organic matter, displayed low retention of 5042-. The amount of S04 2? adsorbed throughout the experiment depended on the content of crystalline forms of Fe and with the Fe and Al extracted with dithionite-citrate.The low retention of S04 2? in the organic horizons and the slightly negative relation with the organic matter suggest an inhibitory effect of the organic matter on the S04 2? retention process. Results of the study show, that under conditions of moderate acidity, SO4 2? retention occurs in the form of adsorption; in strongly acidic conditions, the precipitation of aluminium-sulphate minerals may provide an additional retention mechanism.  相似文献   

9.
Coastal areas in the southeastern USA are prone to hurricanes and strong storms that may cause salt-water influx to freshwater aquatic sediments. These changes in environmental conditions may impact sediment processes including nitrogen (N) cycling. The relative abilities of sediment microbial communities from two freshwater golf course retention ponds that drain into the adjacent wetlands, and two proximal saline wetland ponds, to remove nitrate (NO3−) were compared to assess whether low concentrations of sulfide changed N-transformation processes. Microcosms were incubated with NO3-N (300 μg g dw−1) alone, and with NO3-N and sulfide (H2S) (100 and 200 μg g dw−1). Nitrous oxide (N2O), nitrite (NO2−), NO3−, ammonium (NH4+), SO42− and acid volatile sulfides were analyzed over time. The acetylene block technique was used to measure denitrification in sediment microcosms with no added H2S. Denitrification was measured without acetylene (C2H2) addition in microcosms with added H2S. With no added H2S, denitrification was greater in the freshwater retention ponds than in the wetland ponds. Although low H2S concentrations generally increased NO3-N removal rates at all sites, lag periods were increased and denitrification was inhibited by low sulfide in the freshwater sediments, as evidenced by the greater concentrations of N2O that accumulated compared to those in the wetland sediments. In addition to the inability of the freshwater sediments to convert N2O to N2 in the absence of C2H2, anomalously high transient NO2-N concentrations accumulated in the retention pond samples. NH4-N formation generally decreased due to H2S addition at the freshwater sites; NH4-N formation increased initially at the wetland sites, but was greater when no H2S was added. Storm events that allow influx of SO42−-containing seawater into freshwater systems may change the dominant N species produced from nitrate reduction. Even low concentrations of sulfide produced incomplete denitrification and decreased formation of NH4+ in these coastal freshwater sediments.  相似文献   

10.
The application of the synchrotron technique of the third generation in soil science has permitted researchers to perform a quantitative mineralogical microanalysis in undisturbed samples and to reveal the relationship between the microelements and the solid phase of soils. Three principal methods are used in this technique: microfluorescence (μXRF), microdiffraction (μXRD), and the expanded analysis of the fine structure of the adsorption spectra. By the data of EXAFS spectroscopy, secondary arsenic was found to occur in three forms in soils, i.e., As adsorbed on iron hydroxides, scorodite (FeAsO4 · 2H2O, and As5+ containing jarosite. Despite the high share of carboxyl groups in the organic substance of soils, lead is more readily chelated by the functional groups of aromatic rings to form bidentant complexes. Lead phosphates are the most stable form of Pb in soils. One of the phosphates, i.e., pyromorphite Pb5(PO4)3Cl has been found in ore tailings, lawn soils, soils near some chemical plants, and in soils within geochemical anomalies. The secondary Zn compounds are represented by Zn-containing silicate (kerolith) Si4Zn3O10(OH)2 and, to a lesser extent, by zinc fixed by manganese oxides (birnessite) and iron hydroxides (feroxyhyte).  相似文献   

11.
Equations are developed to predict the distribution of Fe2+ between solid and solution phases in a reduced soil undergoing oxidation at different pHs, based on cation-exchange equilibria and electrical neutrality in the solid and solution. The equations satisfactorily explained experimental results. They are incorporated in the model of Fe2+ diffusion and oxidation developed in Part II, and the model is also extended to allow for O2 consumption in processes other than Fe2+ oxidation. The resultant predictions are tested against measured profiles of Fe(II), Fe(III) and pH in cylinders of reduced soil exposed to O2 at one end. When oxidation rate constants measured in stirred soil suspensions were used to run the model, the predicted rates of O2 consumption were too great and the spread of the oxidation front too small. Satisfactory agreement was achieved for oxidation rate constant values about one-eighth of those measured in the stirred suspensions. The findings are consistent with the rate of Fe2+ oxidation in soil being controlled by access of O2 to Fe2+ sorption sites, as suggested in Part I. The revised model allows a study of the effects of Fe2+ oxidation on the mobility of other cations in reduced soils, e.g. nutrient cations in the rice rhizosphere. Fez+ oxidation and the accompanying acidification may greatly impede cation mobility in reduced soils.  相似文献   

12.
根据泾阳泾河高漫滩沉积剖面中128个样品的元素、化合物含量与粒度分析,研究了泾阳泾河高漫滩剖面沉积特征与洪水变化.结果表明,元素Ma,Ni,Cu,Zn,Ga,Pb,Ba,Rb,V和化合物Al2O3,Fe2O3,K2O含量在剖面各层中变化明显,分辨率高,能够清晰地指示洪水以及降水量的变化.JYa剖面分为18个沉积层,指示了18次大小不同的洪水和18个降水较多的年份.沉积物粒度细,元素Mn,Ni,Cu,Zn,Ga,Pb,Rb,V和化合物Al2O3Fe2O2,K2O含量高,元素Ba含量低,指示沉积时洪水强度小,洪水水位低,降雨量少.沉积物粒度粗,元素Mn,Ni,Cu,Zn,Ga,Pb,Rb,V和化合物Al2O3,Fe2O3,K2O含量低;元素Ba含量高,指示沉积时洪水强度大,洪水水位高,降雨量多.在这18次洪水事件中,在同一次洪水沉积层内形成了两个以上薄层的元素和化合物含量、粒度成分的微小变化,指示多数期次的洪水发生时期常有两个以上洪峰出现.泾阳泾河高漫滩第14,12,13,8,5,1层洪水沉积反映了泾河泾阳段全流域性的年降水量增加,且年降水量至少达到约800 mm.  相似文献   

13.
The aim of this study was to investigate the removal of both polycyclic aromatic hydrocarbons (PAHs) and heavy metals from field-contaminated sediments by activated persulfate oxidation. Various chemicals, including hydroxypropyl-??-cyclodextrin (HPCD), S,S-ethylenediaminedisuccinic acid (EDDS), tetrasodium pyrophosphate (Na4P2O7), and hydrochloric acid (HCl), were applied individually before or after activated persulfate oxidation to enhance the co-removal of both types of pollutants. It was found that the organic removal efficiency was not significantly enhanced by increasing the concentration of HPCD from 2.5 to 5.0?mM. The removal efficiency of heavy metals was not improved even at an excess amount of EDDS after activated persulfate oxidation. However, the addition of EDDS acted as the Fe2+ carrier for activated persulfate oxidation. In addition, no significant enhancement of heavy metal removal was observed by increasing the concentrations of Na4P2O7 and HCl from 0.01 to 0.1?M after activated persulfate oxidation. However, comparing 0.1?M HCl with 0.1?M Na4P2O7, HCl was shown to be more effective in promoting the removal of organic pollutants. With further adjustments on the experimental conditions, the highest removal amount of metals and PAHs was achieved by adding 2?M of HCl with 3?days mixing, followed by Fe2+-activated persulfate oxidation (PS/Fe2+ molar ratio at 4:1) for further 6?h mixing. The removal efficiency of low and high molecular weight PAHs was about 70 and 20?%, respectively, while the removal efficiency of metals was 70, 100, 40, 65, 65, 80, and 100?% for Cr, Cu, Hg, Mn, Ni, Pb, and Zn, respectively.  相似文献   

14.
Concentrations of dialysable silica in equilibrium with Al2O3-SiO2-H2O sols at pH 4.5–5.0 confirm the formation of a poorly ordered non-dialysable proto-imogolite species with an Al : Si ratio near 2, close to that of imogolite. Sols with Al : Si>2 give nearly constant levels of free silica in solution in the range 2–6 μg/cm3, indicating equilibrium between proto-imogolite and aluminium hydroxide species. These findings indicate that imogolite-like precipitates in acid soils will buffer silica in solution to within this range during leaching episodes. Imogolite is more stable than a previous estimate suggested, and a revised value for its free energy of formation is proposed: ΔG0f(298.15) = -2929.7 kJ/mol. In Fe2O3-SiO2-H2O sols, the Fe : Si ratio of the non-dialysable species varies smoothly from 11 to 3 as free silica in solution ranges from 4 to 35 μg/cm3. Such sols are much less colloidally stable than hydroxyaluminium silicate sols, but mixed Al2O3—Fe2O3—SiO2—H2O sols are almost as stable as iron-free sols up to a Fe : Al ratio of 1.5. Thus migration of Al and Fe as mixed hydroxide sols can account for the almost constant ratio of Al to Fe with depth in oxalate extracts from Bs horizons of podzols.  相似文献   

15.
The activity of zinc (Zn) ions in the soil solution bathing plant roots is controlled by the simultaneous equilibrium of several competing reactions, such as surface exchange, specific bonding, lattice penetration, precipitation reactions, and the processes leading to the desorption of surface and lattice-bound ions. Desorption of Zn in 15 calcareous soils from southern Iran, treated with 10 mg Zn kg?1 soil as zinc sulfate (ZnSO4·7H2O) and 100 mg phosphorus (P) kg?1 soil as calcium phosphate [Ca(H2PO4)2H2O] and then equilibrated and extracted with diethylentriaminepentaacetic acid (DTPA), was studied in this experiment. The results were fitted to zero-order, first-order, second-order, third-order, parabolic diffusion, two-constant rate, Elovich, and simple Elovich kinetic models. Two-constant rate, simple Elovich, and parabolic diffusion models were determined to best describe Zn-desorption kinetics. Zinc desorption increased as Zn was applied but decreased with applied P.  相似文献   

16.
The detailed characterization of mineralogical changes with depth in pyrite-rich tailings from an abandoned mine provides insight into the future geochemical progression of the tailings. Based on the pH and mineralogical characterization, the Guryong mine tailings can be divided into four zones: jarosite zone, iron (Fe)-sulfate zone, Fe-oxyhydroxide and gypsum-bearing pyrite zone, and calcite-bearing pyrite zone. The jarosite zone was approximately 50 cm deep from the surface and had secondary gypsum (CaSO4·2H2O) and jarosite [KFe3(SO4)2(OH)6]. The pH of the jarosite zone ranged from 2.3 to 4.0, and the ratio of total Fe to total sulfur (S) ranged from 0.7 to 4.3. These results show that the solid phase, schwertmannite or jarosite, is associated with the total sulfate (SO4) content. The Fe-sulfate zone had low pH values caused by strong pyrite oxidation and greatest amounts of the secondary minerals and acid-leachable heavy metals. The Fe-oxyhydroxide and gypsum-bearing pyrite zone reflects partial alteration of pyrite resulting in the coexistence of secondary gypsum and primary pyrite. The calcite-bearing pyrite zone had pH values exceeding 7.0 at greater depths and contained primary calcite (CaCO3). However, the GS6 and GS10 profiles, which contained coarse particles near the water table, were the most acidic and their calcite contents were not dectected. The oxidation of pyrite is the most important factor in the mineral cycling of Guryong mine tailings, controlling the changes in pH, the precipitation of secondary mineral phases, and the behavior of heavy metals through the profile.  相似文献   

17.
To study the factors that influence the release of free H2S, flooded soils were incubated with plant material and either sodium sulphate or elemental sulphur. Residual sulphate, FeS and H2S were measured throughout the reaction. Less free H2S was evolved from a periodically waterlogged soil than from a well-drained soil of comparable HC1- and dithionite-soluble Fe content. With a readily soluble synthetic Fe2O3 as the source of Fe, a slight excess of Fe over the SO42– equivalent sufficed to prevent loss of H2S. The native organic matter in the well-drained Rothamsted top-soil seemed to have no effect in promoting loss of H2S, but the FeS:H2S ratio was strongly influenced by the nature of the plant material used as the source of energy. With either Na2SO4 or S, considerably more free H2S was evolved with lucerne than with rice blade. With S, the pH of the incubated mixtures was close to that of the nominally S-free system, whereas with Na2SO4 the mixture became quite alkaline. More free H2S was evolved under the more alkaline conditions obtained with Na2SO4, which suggests that it is the initial mobilization of Fe that governs the distribution of the reduced S, rather than the pH-solubility relations of FeS. An oxidized surface layer is very effective in retaining sulphur in the soil.  相似文献   

18.
不同施肥方法对双季稻区水稻产量及氮素流失的影响   总被引：8，自引：2，他引：8  
为保障粮食安全,减少稻田生态系统氮肥投入,提高氮肥利用率和减少氮素流失成为重要的农业和环境措施。本研究在位于湖南岳阳的农业部岳阳农业环境科学观测实验站开展为期1年的早稻、晚稻田间试验,比较了不施肥(T_1)、尿素常规施肥(T_2,施N 280 kg·hm~(-2)、P_2O_5 165 kg·hm~(-2)、K_2O 120 kg·hm~(-2))、控释肥常规施用(T_3,施N 230 kg·hm~(-2)、P_2O_5 165 kg·hm~(-2)、K_2O 120 kg·hm~(-2))、高量控释肥侧条施用(T_4,施N 230 kg·hm~(-2)、P_2O_5 138 kg·hm~(-2)、K_2O 120 kg·hm~(-2))、中量控释肥侧条施用(T5,施N 180 kg·hm~(-2)、P_2O_5 123 kg·hm~(-2)、K_2O 120kg·hm~(-2))及低量控释肥侧条施用(T6,施N 140 kg·hm~(-2)、P_2O_5 123 kg·hm~(-2)、K_2O 120 kg·hm~(-2))下氮肥的养分利用率、作物产量及氮素流失情况,以期为稻田氮素合理利用提供理论依据。研究结果表明,控释肥侧条施用可有效提高水稻的产量和氮肥利用率,减少面源流失。1)在减少稻田秧苗数量和氮肥施用量的条件下,T_4处理的水稻早晚稻产量分别比T_2处理增加13.17%和4.72%,与T_3处理相比亦分别增加7.27%和1.74%;2)侧条施肥处理有效降低了稻田氮素流失量,年氮流失量为0.466~0.673 kg×hm~(-2),比常规施肥处理降低地表径流氮流失量3.54%~29.36%;3)侧条施肥有效提高了氮肥利用率,T_4处理的氮肥利用率分别是T_2、T_3处理的1.70倍和1.22倍。因此,采用合适的施肥方式、配施适量控释氮肥可获得较高的产值和收益。高量控释肥侧条施用(T_4)是本研究区域最佳的施肥模式,对实现现代化农业生产的高产高效、资源节约和生态环境保护具有重要意义。  相似文献   

19.
The present research was done to study the ability of cyanobacterial species for removing heavy metals from sewage. As well, to estimate the growth and some metabolites of Beta vulgaris irrigated with sewage treated by cyanobacterial species. The best removal results were obtained by Anabaena oryzae compared to the other studied cyanobacteria. Whereas A. oryzae showed high removal efficiency for cadmium (Cd2+) followed by lead (Pb2+), zinc (Zn2+), iron (Fe2+), copper (Cu2+) and manganese (Mn2+) (88.5, 83.1, 68.8, 62.0, 55.2 and 42.4%, respectively). Irrigation of plants by untreated or treated sewage generally caused stimulation in the total proteins, proline, carbohydrates and ascorbic acid. B. vulgaris grown in soil irrigated with untreated sewage showed maximum catalase, peroxidase activity, hydrogen peroxide (H2O2) and lipid peroxidation compared to the other treatments. The heavy metals availability was relatively low in the plant irrigated with treated sewage by cyanobacterial species, so the antioxidants requirement was low and hence the induction of antioxidants was lower compared to the plant irrigated with untreated sewage.  相似文献   

20.
Abstract

The general concept that low‐water‐soluble phosphorus (P) fertilizers should be more agronomically effective when applied to acidic soils was developed based on sources containing mainly calcium (Ca)‐P compounds, but it may not hold true for sources with different chemical composition. To obtain information related to this issue, two important iron (Fe)–potassium (K)–P compounds present in superphosphates [Fe3KH8(PO4)6 · 6H2O, H8, and Fe3KH14(PO4)8 · 4H2O, H14] were prepared and characterized. These P sources were used to provide 30 and 60 mg P kg?1 as neutral ammonium citrate (NAC)+H2O‐soluble P. Reagent‐grade monocalcium phosphate (MCP) was used as a standard P source with high water solubility with an additional rate of 120 mg P kg?1 included. Also, mixtures of both Fe‐K‐P compounds and MCP were prepared to provide 0, 25, 50, 75, and 100% of the total P as MCP. All sources were applied to a clayey loamy acid soil (pH 5.3) classified as Rhodic Kanhapludult. The soil was incubated at two rates (0 and 10 g kg?1) of lime, which resulted in pH 5.4 and 6.8. Upland rice was cultivated to maturity. The H14 compound confirmed to be a highly effective source of P for the rice plants at both soil pH, as opposed to the H8, which was poorly effective when applied alone. When mixed with water‐soluble P (WSP), the H8 was able to provide P to the plants with the maximum yield of upland rice reached with 54.8 and 80.5% of WSP for pH 5.4 and 6.8, respectively. The high agronomic performance of the H14 compound clearly indicates that this low‐water‐soluble P source cannot be deemed as ineffective at high soil pH.  相似文献   

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