不同因素对柠檬酸浸提-硅钼蓝比色法测试土壤有效硅的影响及优化措施

Influence of Different Factors on the Detection of Available Silicon in Soil by Citric Acid Leaching-Silica Molybdenum Blue Colorimetric Method and Its Optimization Measures

准确测定土壤中有效硅含量可以了解土壤硅素肥力状况,有助于指导施肥、改善土壤质量。同时土壤中有效硅含量作为第三次全国土壤普查必测的一项参数,有利于全面摸清土壤硅的含量水平。通过改变浸提方式、浸提剂浓度以及显色方式等参数对柠檬酸浸提-硅钼蓝比色法测试土壤有效硅进行考察,对测试过程中的影响因素进行分析,并进行针对性的优化,最后对改进后的测试条件进行方法学研究。结果表明,浸提时间不足、浸提剂浓度偏低以及显色时温度不稳定均会导致所测的有效硅含量偏低。采用连续振荡2 h的方式浸提、增加浸提剂浓度为0.050 mol/L、显色过程全程于35℃水浴中操作等措施可以较好地减少误差,获得更准确的结果。改进后的方法线性良好,相关系数r为0.999 6,检出限为1.0 mg/kg,精密度RSD(n=6)最大为2%,准确度相对误差最大为-4.7%。测定结果可靠,可以为第三次全国土壤普查内业检测提供参考和借鉴。

Accurate detection of soil available silicon content is beneficial to understand the fertility status of silica in soil and provide guidance for fertilization and improve soil qualities.At the same time,the available silicon content in soil is a mandatory parameter of the third national soil survey,which is conducive to comprehensively understanding the level of silicon content in soil.In this paper,the detection of available silicon in soil by citric acid leaching-silica molybdenum blue colorimetric method was discussed by changing the leaching method,leaching agent concentration and color rendering method.The influencing factors of the detecting process were analyzed.Meanwhile,the targeted optimization was carried out,and finally the optimal detection parameters were methodologically studied.The results showed that insufficient leaching time,low leaching agent concentration and unstable temperature during color rendering resulted in the low available silicon content detected.The method of continuous oscillation for 2 h,increasing the concentration of leaching agent to 0.050 mol/L,operating in 35℃ water bath during the whole process of color development better reduced the error,and more accurate results were obtained.The improved method had good linearity,with the correlation coefficient(r)was 0.9996,the detection limit was 1.0 mg/kg,the maximum precision RSD(n=6)was 2%,and the maximum relative error of accuracy was-4.7%.The detection results were reliable and can provide references for the third national soil survey.