土壤作为人类生存的重要物质基础和自然资源之一, 其营养元素含量不仅是农业生产的基础, 也是评价土壤质量的重要指标。 传统测定土壤中营养元素的方法以液体进样为主, 操作繁琐且对环境有一定的污染。 采用超高压制样技术与LIBS技术联用, 综合了绿色无污染的样品前处理技术以及操作简单、 可进行多元素同步快速检测的测定技术, 建立了高压制样-激光诱导击穿光谱技术测定土壤中的硅铝铁钾的分析方法。 通过对制样压力大小的对比研究发现, 当制样压力在2 000 kN时, 制备出的样品表面光滑、 平整, 具有更好的致密性, 测定精密度达到最好; 通过对LIBS仪器测定条件的优化, 发现在使用多位置采样的方式, 激光能量、 采集延迟、 光斑尺寸分别为0.8 mJ、 0.5 μs、 60 μm的条件下, 能够减小样片剥蚀产生的热效应及样片表面不均匀对测定结果造成的影响, 提高测定信背比, 从而提高测定结果的准确度和精密度。 在该方法优化后的条件下, 采用土壤成分分析标准物质, 以多变量做线性回归的定标曲线, 得到了较好的线性关系, 有效降低了基体效应对测定结果的影响。 通过国家一级土壤成分分析标准物质的验证, 除个别元素外, 方法测定营养元素的精密度范围均在0.31%~4.21%之间, 且测定结果与认定值基本一致。 该方法不仅操作简单、 能够避免传统方法带来的环境污染, 同时也能够实现多元素同时测定, 推动了LIBS技术在定量分析领域的进一步发展。

As one of the important material basis and natural resources for human survival, the content of nutrient elements in soil is not only the basis of agricultural production but also an important indicator for evaluating soil quality. The traditional method for determining soil nutrient elements is mainly based on liquid injection, which is cumbersome to operate and has certain environmental pollution. In this paper, the ultra-high pressure sample preparation technology is combined with LIBS technology, which integrates the green and pollution-free sample pretreatment technology and the determination technology that is simple to operate and can carry out multi-element synchronous and rapid detection. The analytical method for determining Silico, Aluminum, Iron and Potassium in soil by ultra-high pressure sample preparation and laser-induced breakdown spectroscopy technology is established. The comparative study on the sample preparation pressure found that when the sample preparation pressure is 2 000 kN, the surface of the prepared sample is smooth and flat, with better compactness and the best measurement precision. By optimizing the measurement conditions of the LIBS instrument, we found that the use of multiple location sampling, the laser energy, gate delay, and spot size were 0.80 mJ, 0.5 μs, and 60 μm, respectively, could reduce the influence of thermal effect caused by the ablation of the sample and sample surface unevenness on the measurement results. It increases the signal-to-background ratio of the measurement, thereby increasing the accuracy and precision of the measurement results. Under the optimized conditions of this method, we used the Certified Reference Materials for the Chemical Composition of Soils to do the calibration curve of linear regression with multiple variables. We obtained a good linear relationship, which reduced the influence of the matrix effect on the measurement results. According to the verification of the Certified Reference Materials for the Chemical Composition of Soils, except for individual elements, the method’s precision for determining nutrient elements is between 0.31%~4.21%, and the determination results are basically consistent with the certified values. This method is not only simple to operate and can avoid the environmental pollution caused by traditional methods, but it also can realize the simultaneous determination of multiple elements, which promotes the further development of LIBS technology in quantitative analysis.