保存、分析方法等因素对土壤中硝态氮测定的影响

为探明土壤中硝态氮测定的影响因素,采用黑土、潮土、红壤为材料,研究样品的保存方法、浸提剂种类、分析方法、实验用水及试剂纯度对土壤中硝态氮测定的影响。结果表明,测定土壤硝态氮时,土样在冷冻条件下保存优于冷藏条件。冷冻条件下保存可在45 d内完成测试,而冷藏保存则需在7 d内完成测试。采用0.01 mol/L CaCl2和2 mol/L KCl为浸提剂时,对土壤中硝态氮的测定结果无显著差异。紫外比色法的测定结果与林业标准法(LY/T1230-1999)相比无显著差异,但显著高于流动注射法,且紫外比色法与流动注射法之间有显著相关性。流动注射法的测定结果与林业标准法相比也无显著差异。实验用水的杂质可使土壤中硝态氮的测定结果显著偏高,对其进行加热煮沸、蒸馏及无氨化蒸馏后可显著降低水中杂质的含量。

Effects of Preservation,Analysis Method on Determination of Nitrate in Soils

To analyze factors influencing the determination of nitrate in soils,the effects of sample preservation method,extracting agent,analysis method,purity of water and chemical reagents on the determination of nitrate in three typical soils including black soil,alluvial soil and red soil,were investigated.The results showed that the cryopreservation method was better than the cold preservation for the collected soil samples.Analysis of nitrate in soils kept in freezing and cooling conditions should be finished within 45 d and 7 d,respectively.There were no significant difference between 0.01mol/L CaCl2 and 2 mol/L KCl used for extraction of nitrate.No significant difference was found in analyzed results between the standard method for forestry soils (LY/T 1230-1999) and the UV spetrophotometry,whereas values of UV spetrophotometry were significantly higher than that of the continuous flow injection analysis method,and an obvious correlation was found between them.The use of impure water would make results higher,techniques with respect to boiling,distillation,and distillation for ammonia removal of water could eliminate the effect of impurity.