Comparison of different extract methods on extractable nitrogen in sediments from an urban polluted river

Abstract

以城市污染河道——南京仙林大学城九乡河表层沉积物为研究对象,探讨沉积物常用提取剂(1 mol/L KCl、2 mol/L KCl、4 mol/L KCl和0.01 mol/L CaCl₂)在不同液土比(5:1、10:1、50:1和100:1)条件下,对城市污染河道沉积物可提取态氮(NH₄⁺-N、NO₃^--N)测定的影响.结果表明:KCl的提取效果要优于CaCl₂,二者NH₄⁺-N提取量分别为312.17~479.23、177.52~339.31 mg/kg,NO₃^--N提取量分别为4.49~21.56、4.25~8.53 mg/kg;可提取态氮提取量随液土比增高而增大,其中1 mol/L KCl组,液土比100:1时NH₄⁺-N和NO₃^--N提取量分别比液土比5:1时增加41.97%和187.08%;NH₄⁺-N提取量随提取剂浓度增高而增大,NO₃^--N随提取剂浓度增高而降低;采用1 mol/L KCl提取剂、液土比100:1的组合联合提取城市污染河道沉积物中的NH₄⁺-N、NO₃^--N,提取效果较好.;To explore the influence of different extractant (1 mol/L KCl, 2 mol/L KCl, 4 mol/L KCl and 0.01 mol/L CaCl₂) and ratio of water to sediment (5:1, 10:1, 50:1 and 100:1) on the determination of extractable nitrogen in sediments from an urban polluted river, surface sediments of Jiuxiang River in Xianlin university town of Nanjing was used in the experiment. Result showed that KCl extract nitrogen more effectively than CaCl₂. The amount of NH₄⁺-N extracted by KCl and CaCl₂ ranged from 312.17 mg/kg to 479.23 mg/kg and 177.52 mg/kg to 339.31 mg/kg, respectively, while NO₃^--N extracted by them ranged from 4.49 mg/kg to 21.56 mg/kg and 4.25 mg/kg to 8.53 mg/kg, respectively. The amount of extractable nitrogen increased with water-sediment ratios. In the experiment group of 1 mol/L KCl, the extract amount of NH₄⁺-N and NO₃^--N increased by 41.97% and 187.08%when the ratio of water to sediment ranged from 5:1 to 100:1, respectively. The amount of NH₄⁺-N extracted increased with higher extractant concentrations, while NO₃^--N decreased with lower ones. The experiment suggested that 1 mol/L KCl as extractant and the water-sediment ratio of 100:1 make a better combination when using for extracting NH₄⁺-N and NO₃^--N from the urban river sediment.