[Objective] The aim of the research was to reveal the influence mechanism of sediment-water exchange of nutrients in Chaohu Lake. [Method] The effects of environmental factors (overlying water, temperature, pH and dis...[Objective] The aim of the research was to reveal the influence mechanism of sediment-water exchange of nutrients in Chaohu Lake. [Method] The effects of environmental factors (overlying water, temperature, pH and dissolved oxygen concentration) on NH_4^+ release in sediment from Chaohu Lake were studied under controlled laboratory conditions. [Results] With the rising of temperature and the decrease of NH_4^+ concentration in overlying water, NH_4^+ released from sediment increased significantly. pH had a great effect on NH_4^+ release with a complicated mechanism. The largest release amount of NH_4^+ under anaerobic condition was about 6 times as much as that under aerobic condition. [Conclusion] This research would provide theoretical support for environmental management of Chaohu Lake in the project of leading water from the Yangtze River to Chaohu Lake.展开更多
A hydroponic experiment was conducted to study the effect of partial replacement of NO-3-N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill.). A completely randomized d...A hydroponic experiment was conducted to study the effect of partial replacement of NO-3-N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill.). A completely randomized design was established with three replications and five treatments, i.e., NO-3-N/NH4+-N of 100/0, 75/25, 50/50, 25/75 and 0/100. Results showed that 25% replacement of NO3--N by NH4+-N significantly (P = 0.05) improved fresh and dry weight, revealing that a proper percentage of NH4+-N was important for tomato nitrogen nutrition. This could increase the plant growth even though tomato was a crop that preferred nitrate nutrition. Also an increase in the proportion of NH4+-N in the nutrient solution led to a significant decrease (P = 0.05) in malate, citrate and fumarate. However, the 25% NH4+-N plus 75% NO3--N treatment had no significant effect (P = 0.05) on the 2-ketoglutarate, succinate or oxalic acid content, showing that only some organic acids in tomato plants were affected. Only pyruvate increased significantly (P = 0.05), and it only increased for 25% and 50% replacement of NO3--N by NH4+-N. Metabolism of these organic acids, especially malate, citrate and fumarate, should be further studied at the molecular level in vegetables applied with different nitrogen forms.展开更多
Effects of NHj concentiation, solution/soil ratio and temperature on NH_4^+adsorption were studied in a Eum-Orthic Anthrosol. The slopes of the soil NH_4^+ adsorptionisotherms and the fitted n, the coefficient for the...Effects of NHj concentiation, solution/soil ratio and temperature on NH_4^+adsorption were studied in a Eum-Orthic Anthrosol. The slopes of the soil NH_4^+ adsorptionisotherms and the fitted n, the coefficient for the adsorption intensity, and kappa, the coefficientrelated to adsorption capacity, of the Freundlich equation increased with increasing solution/soilratio (SSR) and with decreasing temperature (T). For the range of experimental conditions, the valueof delta q/delta c, the rate of change of the amount of NH_4^+ adsorbed in the soil solid phase (q)with respect to the equilibrium concentration of NH_4^+ in soil solution (c), was 0.840, indicatingthat q increased with increasing c. From 2 to 45 deg C, delta q/delta SSR, the rate of change of qwith respect to SSR, decreased from 2.598 to 1.996, showing that q increased with increasing SSR,while its increasing rate decreased with temperature. From SSR 1:1 to 20:1, delta q/delta T, therate of change of q with respect to T, decreased from -- 0.095 to -- 0.361, indicating that qdecreased with increasing temperature, and at the same time the negative effect of temperaturebecame larger as SSR increased. Thus under the experimental conditions the order of importance indetermining the amount of NH_4^+ adsorbed in the soil solid phase was delta q/delta SSR > deltaq/delta c > |delta q/delta T|, indicating that the greatest effect on the amount of NH_4^+ adsorbedwas with the solution/soil ratio; the equilibrium concentration of NH_4^+ had a lesser effect; andtemperature had the least effect.展开更多
文摘[Objective] The aim of the research was to reveal the influence mechanism of sediment-water exchange of nutrients in Chaohu Lake. [Method] The effects of environmental factors (overlying water, temperature, pH and dissolved oxygen concentration) on NH_4^+ release in sediment from Chaohu Lake were studied under controlled laboratory conditions. [Results] With the rising of temperature and the decrease of NH_4^+ concentration in overlying water, NH_4^+ released from sediment increased significantly. pH had a great effect on NH_4^+ release with a complicated mechanism. The largest release amount of NH_4^+ under anaerobic condition was about 6 times as much as that under aerobic condition. [Conclusion] This research would provide theoretical support for environmental management of Chaohu Lake in the project of leading water from the Yangtze River to Chaohu Lake.
基金Project supported by the National Natural Science Foundation of China (No. 30270790) and National Post-doctoral Foundation of China (No. 2003033494).
文摘A hydroponic experiment was conducted to study the effect of partial replacement of NO-3-N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill.). A completely randomized design was established with three replications and five treatments, i.e., NO-3-N/NH4+-N of 100/0, 75/25, 50/50, 25/75 and 0/100. Results showed that 25% replacement of NO3--N by NH4+-N significantly (P = 0.05) improved fresh and dry weight, revealing that a proper percentage of NH4+-N was important for tomato nitrogen nutrition. This could increase the plant growth even though tomato was a crop that preferred nitrate nutrition. Also an increase in the proportion of NH4+-N in the nutrient solution led to a significant decrease (P = 0.05) in malate, citrate and fumarate. However, the 25% NH4+-N plus 75% NO3--N treatment had no significant effect (P = 0.05) on the 2-ketoglutarate, succinate or oxalic acid content, showing that only some organic acids in tomato plants were affected. Only pyruvate increased significantly (P = 0.05), and it only increased for 25% and 50% replacement of NO3--N by NH4+-N. Metabolism of these organic acids, especially malate, citrate and fumarate, should be further studied at the molecular level in vegetables applied with different nitrogen forms.
基金Project supported by the National Natural Science Foundation of China (No. 49901009).
文摘Effects of NHj concentiation, solution/soil ratio and temperature on NH_4^+adsorption were studied in a Eum-Orthic Anthrosol. The slopes of the soil NH_4^+ adsorptionisotherms and the fitted n, the coefficient for the adsorption intensity, and kappa, the coefficientrelated to adsorption capacity, of the Freundlich equation increased with increasing solution/soilratio (SSR) and with decreasing temperature (T). For the range of experimental conditions, the valueof delta q/delta c, the rate of change of the amount of NH_4^+ adsorbed in the soil solid phase (q)with respect to the equilibrium concentration of NH_4^+ in soil solution (c), was 0.840, indicatingthat q increased with increasing c. From 2 to 45 deg C, delta q/delta SSR, the rate of change of qwith respect to SSR, decreased from 2.598 to 1.996, showing that q increased with increasing SSR,while its increasing rate decreased with temperature. From SSR 1:1 to 20:1, delta q/delta T, therate of change of q with respect to T, decreased from -- 0.095 to -- 0.361, indicating that qdecreased with increasing temperature, and at the same time the negative effect of temperaturebecame larger as SSR increased. Thus under the experimental conditions the order of importance indetermining the amount of NH_4^+ adsorbed in the soil solid phase was delta q/delta SSR > deltaq/delta c > |delta q/delta T|, indicating that the greatest effect on the amount of NH_4^+ adsorbedwas with the solution/soil ratio; the equilibrium concentration of NH_4^+ had a lesser effect; andtemperature had the least effect.
