Potassium （K） release characteristics in soil play a significant role in supplying available K. Information on K-release characteristics in soils of central Iran is limited. The objectives of this study were to dete...Potassium （K） release characteristics in soil play a significant role in supplying available K. Information on K-release characteristics in soils of central Iran is limited. The objectives of this study were to determine K release characteristics and correlations of K release rate constants with K extracted by different chemical methods in surface soils of ten calcareous soils of central Iran. The kinetics of K release in the soils was determined by successive extraction with 0.01 mol L-1 CaC12 in a period of 2-2017 h at 25±1℃. Soil K was extracted by distilled water, 0.5 mol L-1 MgNO3, 0.002 mol L-1 SrC12, 0.1 mol L-1 BaC12, 0.01 mol L-1 CaC12, 1 mol L-1 NaC1, 1 mol L-1 boiling HNO3, 1 mol L-1 NH4OAC, Mehlich 1, 0.002 mol L-1 SrC12 ＋ 0.05 mol L-1 citric acid, and ammonium bicarbonate-diethylenetriamine pentaacetic acid （AB-DTPA）. A plot of cumulative amounts of K released showed a discontinuity in slope at 168 h. Thus, two equations were applied to two segments of the total reaction time （2-168 and 168-2 017 h）. Cumulative amounts of K released ranged from 55 to 299 mg kg-1 in 2-168 h and from 44 to 119 mg kg-1 in 168-2 017 h. Release kinetics of K in the two time segments conformed fairly well to parabolic diffusion, simplified Elovich, and power function models. There was a wide variation in the K release rate constants. Increasingly higher average concentrations of soil K were extracted by distilled water, Mehlich 1, SrC12, CaC12, SrC12 ＋ citric acid, AB-DTPA, MgNO3, NaCI, NH4OAc, BaCI2, and HNO3. Potassium release rate constants were significantly correlated with K extracted. The results of this study showed that information obtained from mathematical modeling in two reaction time segments can help to estimate the K-supplying power of soils.展开更多
Source water reservoirs easily become thermally and dynamically stratified. Internal pollution released from reservoir sediments is the main cause of water quality problems. To mitigate the internal pollution more eff...Source water reservoirs easily become thermally and dynamically stratified. Internal pollution released from reservoir sediments is the main cause of water quality problems. To mitigate the internal pollution more effectively, a new method, which combined chemical stabilization with water lifting aerator （WLA） technology, was proposed and its effciency in inhibiting pollutant release was studied by controlled sediment-water interface experiments. The results showed that this new method can inhibit pollutant release from sediment effectively. The values of mean effciency （E） in different reactors 2#–5# （1# with no agent, 2# 10 mg/L polymeric aluminum chloride （PAC） was added, 3# 20 mg/L PAC was added, 4# 30 mg/L PAC was added, 5# 20 mg/L PAC and 0.2 mg/L palyacrylamide （PAM） were added） for PO43- were 35.0%, 43.9%, 50.4% and 63.6%, respectively. This showed that the higher the PAC concentration was, the better the inhibiting effciency was, and PAM addition strengthened the inhibiting effciency significantly. For Fe2＋, the corresponding values of E for the reactors 2#–5# were 22.9%, 47.2%, 34.3% and 46.2%, respectively. The inhibiting effect of PAC and PAM on Mn release remained positive for a relatively short time, about 10 days, and was not so effective as for PO43- and Fe2＋. The average effciencies in inhibiting the release of UV254 were 35.3%, 25.9%, 35.5%, 38.9% and 39.5% for reactors 2#–5#, respectively. The inhibiting mechanisms of the agents for different pollutants varied among the conditions and should be studied further.展开更多
文摘Potassium （K） release characteristics in soil play a significant role in supplying available K. Information on K-release characteristics in soils of central Iran is limited. The objectives of this study were to determine K release characteristics and correlations of K release rate constants with K extracted by different chemical methods in surface soils of ten calcareous soils of central Iran. The kinetics of K release in the soils was determined by successive extraction with 0.01 mol L-1 CaC12 in a period of 2-2017 h at 25±1℃. Soil K was extracted by distilled water, 0.5 mol L-1 MgNO3, 0.002 mol L-1 SrC12, 0.1 mol L-1 BaC12, 0.01 mol L-1 CaC12, 1 mol L-1 NaC1, 1 mol L-1 boiling HNO3, 1 mol L-1 NH4OAC, Mehlich 1, 0.002 mol L-1 SrC12 ＋ 0.05 mol L-1 citric acid, and ammonium bicarbonate-diethylenetriamine pentaacetic acid （AB-DTPA）. A plot of cumulative amounts of K released showed a discontinuity in slope at 168 h. Thus, two equations were applied to two segments of the total reaction time （2-168 and 168-2 017 h）. Cumulative amounts of K released ranged from 55 to 299 mg kg-1 in 2-168 h and from 44 to 119 mg kg-1 in 168-2 017 h. Release kinetics of K in the two time segments conformed fairly well to parabolic diffusion, simplified Elovich, and power function models. There was a wide variation in the K release rate constants. Increasingly higher average concentrations of soil K were extracted by distilled water, Mehlich 1, SrC12, CaC12, SrC12 ＋ citric acid, AB-DTPA, MgNO3, NaCI, NH4OAc, BaCI2, and HNO3. Potassium release rate constants were significantly correlated with K extracted. The results of this study showed that information obtained from mathematical modeling in two reaction time segments can help to estimate the K-supplying power of soils.
基金supported by the Major Science and Technology Program for Water Pollution Control and Treatment (No. 2009ZX07424-006)the National Natural Science Foundation of China (No. 50830303)the Program for Changjiang Scholars and Innovative Research Team in University of MOE of China (PCSIRT) (No.IRT0853)
文摘Source water reservoirs easily become thermally and dynamically stratified. Internal pollution released from reservoir sediments is the main cause of water quality problems. To mitigate the internal pollution more effectively, a new method, which combined chemical stabilization with water lifting aerator （WLA） technology, was proposed and its effciency in inhibiting pollutant release was studied by controlled sediment-water interface experiments. The results showed that this new method can inhibit pollutant release from sediment effectively. The values of mean effciency （E） in different reactors 2#–5# （1# with no agent, 2# 10 mg/L polymeric aluminum chloride （PAC） was added, 3# 20 mg/L PAC was added, 4# 30 mg/L PAC was added, 5# 20 mg/L PAC and 0.2 mg/L palyacrylamide （PAM） were added） for PO43- were 35.0%, 43.9%, 50.4% and 63.6%, respectively. This showed that the higher the PAC concentration was, the better the inhibiting effciency was, and PAM addition strengthened the inhibiting effciency significantly. For Fe2＋, the corresponding values of E for the reactors 2#–5# were 22.9%, 47.2%, 34.3% and 46.2%, respectively. The inhibiting effect of PAC and PAM on Mn release remained positive for a relatively short time, about 10 days, and was not so effective as for PO43- and Fe2＋. The average effciencies in inhibiting the release of UV254 were 35.3%, 25.9%, 35.5%, 38.9% and 39.5% for reactors 2#–5#, respectively. The inhibiting mechanisms of the agents for different pollutants varied among the conditions and should be studied further.
