氯化钾中杂质铵含量及对土壤铵态氮测定的影响

Ammonium Contents in Potassium Chloride Impurities and its Impact on Soil NH_4^+-N Determination

对用连续流动分析仪测定土壤NH4+-N时有负值出现的现象进行了初步研究。测定了14种市售氯化钾中杂质铵的含量,选用其中4种对采自陕西杨凌、长武、合阳等地的14个土壤样品NH4+-N做了测定。结果表明:14种市售氯化钾NH4+-N含量范围为1.7～49.1 mg kg-1;当氯化钾浸提剂含NH4+-N小于1.3 mg L-1时,对土壤NH4+-N的测定基本没有影响,当大于2.6 mg L-1时,会使某些土壤NH4+-N值不同程度降低甚至为负值。为避免杂质干扰,可事先用简便的点滴法粗略定量浸提剂中的NH4+-N,当其大于1.3 mg L-1时,最好更换氯化钾,当大于2.6 mg L-1时,必须更换,以保证结果的可靠性。

Preliminary study was carried out on the negative value of soil NH4＋-N concentration measured by Continuous Flow Analytical System.Impurity contents in 14 kinds of commercially available potassium chloride were measured,and four kinds of potassium chloride were chosen to measure NH4＋-N contents in 14 soil samples which collected from Yangling,Changwu,Heyang,etc.The results showed that NH4＋-N contents in 14 kinds of commercially available potassium chloride were in the range of 1.7 mg kg-1 to 49.1 mg kg-1.When the NH4＋-N contents in potassium chloride were less than 1.3 mg L-1,soil NH4＋-N measurement would not be affected;when the NH4＋-N contents in potassium chloride extraction reagent were higher than 2.6 mg L-1,the values of soil NH4＋-N contents would decrease or even be negative.In order to avoid interference of impurities,extraction reagent measuring NH4＋-N content should be measured at first： if the NH4＋-N concentrations were over 1.3 mg L-1,it is best to change potassium chloride;if the values were over 2.6 mg L-1,it must be changed to ensure the reliability of the results.