采用波长1 064 nm的调Q脉冲Nd∶YAG激光器和多通道小型光纤光栅光谱仪, 建立了一套激光诱导击穿光谱分析装置。 记录了系列土壤标准样品的激光诱导等离子体发射光谱, 详细研究了重金属原子Cr和Sr的特征辐射谱线信号强度、 标准偏差与数据采样方式以及采样平均次数的关系, 首次采用300个激光脉冲轰击样品表面同一点, 并取其中最大光谱信号后的200次激光轰击等离子体发射光谱的平均值进行分析的取样平均方式, 发现能较好地把对重金属Cr和Sr浓度分析测量的相对标准偏差（RSD）分别减小到9.02%和10.5%, 并得到了定量分析Cr和Sr等金属的定标曲线, 对Cr和Sr元素的检测灵敏度分别为25.3和15.2 μg·g-1, 优于目前国内外报道的结果。 研究表明我们的采用的数据采集、 分析定标方法对提高了LIBS技术在土壤中金属检测检测灵敏度和精密度具有很好的应用价值。

As a powerful and promising analytical technique, laser-induced breakdown spectroscopy (LIBS) has been undergoing a rapid development in the past years. LIBS technique allows for rapid, multi-elemental, in situ measurements, and has been proposed for real time soil analysis. Currently, a global effort is focused on how to further improve the analytical accuracy and repeatability of this promising technique. In the present paper, a method of laser induced breakdown spectroscopy (LIBS) for the determination of Cr and Sr in soil was established. The experimental instrument was mainly equipped with a pulsed 1 064 nm Nd∶YAG laser and a portable spectrometer. The behavior of shot to shot variation in spectra line intensity emitted by the laser plasma was studied. Data acquisition and processing procedures were experimentally optimized. The precision of the method was, in terms of RSD, 9.02% for Cr 425.44 nm and 10.5% for Sr 460.73 nm respectively (n=8). Detection limits were 25.3 mg·g-1 for Cr and 15.2 mg·g-1 for Sr in soil respectively. These results are better than the data reported in literature, indicating that the established LIBS method is suitable for the determination of heavy metal in soil.