Monoammonium phosphate (1 mol L-1), monopotassium phosphate (1 mol L-1) and aluminum ohloride (5×10-3 mol L-1) were used to investigate the influence of pH on the formation of NH4-taranakite and K-taranakite in s...Monoammonium phosphate (1 mol L-1), monopotassium phosphate (1 mol L-1) and aluminum ohloride (5×10-3 mol L-1) were used to investigate the influence of pH on the formation of NH4-taranakite and K-taranakite in systems with a high NH4H2PO4 or KH2PO4 concentration. The experimental data indicated that the reaction products of aluminum with NH4H2PO4 or KH2PO4 changed with the pH in the systems. In a pH range of 2.5 to 10.0, as the pH increased, the products in either ammonium or potassium system followed the sequence: taranakite, amorphous (NH4, K)2AlH(PO4)2 .4H2O, and then crystalline (NH4, K)AlPO4OH.2H2O. However, the pH ranges of the formation of these products in ammonium system were different from potassium system. NH4-taranakite formed from pH 2.75 to PH 5.75, whereas K-taranakite formed in the pH range of 3.00 to 5.00. From the theoretical calculation by a computer program (GEOCHEM version 2.0), NH4-taranakite and K-taranakite could form at the pH from 1.50 to 8.30 and from 1.25 to 8.45,respectively. These pH ranges were much wider than the experimental results. The difference between the experimental data and theoretical data was attributed to the lack of kinetic data and/or the incompleteness and inaccuracy of the thermodynamic data in the data base of the program. The PH ranges of the formation of the taranakites indicated that the taranakites could exist in the immediate vicinity of phosphate fertilizer zone as reaction products of phosphate fertilizers with soils, especially acidic soils, resulting in the fixation of not only phosphate but also nitrogen and/or potassium in soils.展开更多
Limited information is available concerning the mineralogy of paddy soils in the southeastern China.Using chemical methods in conjunction with X-ray diffractometry, we studied the mineral composition of three paddy so...Limited information is available concerning the mineralogy of paddy soils in the southeastern China.Using chemical methods in conjunction with X-ray diffractometry, we studied the mineral composition of three paddy soils: Jinghua (paddy soil on Quaternary red clay), Fuyang (Hapl-percogenic loamy paddy soil), and Shaoxing (gleyic clayey paddy soil). All the soils contained quartz, mica, vermiculite, chlorite and kaolinite, and the distribution of these minerals varied with soil particle size fractions. The clay fraction of the F’uyang and Shaoxing soils also contained smectite. Although X-ray data did not show the presence of smectite in the Jinghua soil, this mineral was identified by the chemical method, suggesting a transitional property of the mineral in the soil. Hydroxy-Al interlayered minerals were also present in the clay fraction.The amount of smectite in the soils was 31.6 (Shaoxing), 16.5 (Fuyang), and 21.4 (Jinghua) g kg-1; for vermiculite it was 33.3 (Shaoxing), 16.5 (Fuyang), and 8.5 (Jinghua) g kg-1. Smectite was only found in the clay fraction. In contrast, amounts of vermiculite in soil particle size fractions were 3.0～11.4 (sand),2.1～6.0 (coarse silt), 4.6～18.9 (medium silt), 0.9～40.0 (fine silt), and 17.0～108 (clay) g kg-1. The amount of noncrystalline aluminosilicates in the soils in g kg-1 decreased in the order: Shaoxing (2.4) > Jinghua (1.9) > Fuyang (1.7). This study has provided useful mineralogical information that is fundamental in future developmellt of management strategies of the soils.展开更多
文摘Monoammonium phosphate (1 mol L-1), monopotassium phosphate (1 mol L-1) and aluminum ohloride (5×10-3 mol L-1) were used to investigate the influence of pH on the formation of NH4-taranakite and K-taranakite in systems with a high NH4H2PO4 or KH2PO4 concentration. The experimental data indicated that the reaction products of aluminum with NH4H2PO4 or KH2PO4 changed with the pH in the systems. In a pH range of 2.5 to 10.0, as the pH increased, the products in either ammonium or potassium system followed the sequence: taranakite, amorphous (NH4, K)2AlH(PO4)2 .4H2O, and then crystalline (NH4, K)AlPO4OH.2H2O. However, the pH ranges of the formation of these products in ammonium system were different from potassium system. NH4-taranakite formed from pH 2.75 to PH 5.75, whereas K-taranakite formed in the pH range of 3.00 to 5.00. From the theoretical calculation by a computer program (GEOCHEM version 2.0), NH4-taranakite and K-taranakite could form at the pH from 1.50 to 8.30 and from 1.25 to 8.45,respectively. These pH ranges were much wider than the experimental results. The difference between the experimental data and theoretical data was attributed to the lack of kinetic data and/or the incompleteness and inaccuracy of the thermodynamic data in the data base of the program. The PH ranges of the formation of the taranakites indicated that the taranakites could exist in the immediate vicinity of phosphate fertilizer zone as reaction products of phosphate fertilizers with soils, especially acidic soils, resulting in the fixation of not only phosphate but also nitrogen and/or potassium in soils.
文摘Limited information is available concerning the mineralogy of paddy soils in the southeastern China.Using chemical methods in conjunction with X-ray diffractometry, we studied the mineral composition of three paddy soils: Jinghua (paddy soil on Quaternary red clay), Fuyang (Hapl-percogenic loamy paddy soil), and Shaoxing (gleyic clayey paddy soil). All the soils contained quartz, mica, vermiculite, chlorite and kaolinite, and the distribution of these minerals varied with soil particle size fractions. The clay fraction of the F’uyang and Shaoxing soils also contained smectite. Although X-ray data did not show the presence of smectite in the Jinghua soil, this mineral was identified by the chemical method, suggesting a transitional property of the mineral in the soil. Hydroxy-Al interlayered minerals were also present in the clay fraction.The amount of smectite in the soils was 31.6 (Shaoxing), 16.5 (Fuyang), and 21.4 (Jinghua) g kg-1; for vermiculite it was 33.3 (Shaoxing), 16.5 (Fuyang), and 8.5 (Jinghua) g kg-1. Smectite was only found in the clay fraction. In contrast, amounts of vermiculite in soil particle size fractions were 3.0～11.4 (sand),2.1～6.0 (coarse silt), 4.6～18.9 (medium silt), 0.9～40.0 (fine silt), and 17.0～108 (clay) g kg-1. The amount of noncrystalline aluminosilicates in the soils in g kg-1 decreased in the order: Shaoxing (2.4) > Jinghua (1.9) > Fuyang (1.7). This study has provided useful mineralogical information that is fundamental in future developmellt of management strategies of the soils.
