Laser-induced breakdown spectroscopy (LIBS) is a potential alternative to wet chemical methods for total soil phosphorus determination, but matrix effects related to physical and chemical sample properties need to be further understood. The aim of this study was to explore matrix effects linked to particle size distribution and chemical form of phosphorus on LIBS response and the ability of LIBS to predict total phosphorus in a range of different soil types. Univariate calibration curves were developed by spiking the soils with increasing doses of phosphorus, and limits of detection for LIBS determined phosphorous (P) (LIBS-P) were calculated. Different particle size distributions in otherwise identical soils were obtained by four milling treatments and effects of chemical form of phosphorus were examined by spiking soils with identical amounts of phosphorus in different chemical compounds. The LIBS-P response showed a high correlation (R2 > 0.99) with total phosphorus for all soils. Yet, the sensitivity of LIBS differed significantly among soils, as the slope of the calibration curves increased with increasing sand content, resulting in estimated limits of detection of 10 mg kg−1 for the sandiest and 122 mg · kg−1 for the most clayey soils. These limits indicate that quantitative evaluation of total phosphorus in sandy and loamy sandy soils by LIBS is feasible, since they are lower than typical total phosphorus concentrations in soil. A given milling treatment created different particle size distributions depending on soil type, and consequently different LIBS-P results. Thus, procedures that specify the required degree of homogenization of soil samples prior to analysis are needed. Sieving after milling could be an option, but that should be tested. The soils spiked with Fe(III) phosphate, potassium phosphate and phytic acid had similar LIBS-P, except for soils with hydroxyapatite, which resulted in markedly lower response. These results suggested that matrix effects related to the chemical nature of phosphorus would be minor for non-calcareous soils in humid regions, where apatites comprise only a small fraction of total phosphorus. Strategies to overcome matrix effects related to particle size and content of apatite-phosphorus by combining multivariate models and soil type groupings should be further investigated.

中文翻译：

---

EXPRESS：使用激光诱导分解光谱法测定土壤中的总磷：评估基质效应的不同来源

激光诱导击穿光谱 (LIBS) 是测定土壤总磷的湿化学方法的潜在替代方法，但需要进一步了解与物理和化学样品特性相关的基质效应。本研究的目的是探索与磷的粒径分布和化学形式相关的基质效应对 LIBS 响应的影响，以及 LIBS 预测一系列不同土壤类型中总磷的能力。单变量校准曲线是通过在土壤中增加磷剂量来制定的，并计算了 LIBS 测定的磷 (P) (LIBS-P) 的检测限。在其他方面相同的土壤中，通过四种研磨处理获得了不同的粒度分布，并通过在不同化合物中添加相同数量的磷的土壤来检查磷的化学形式的影响。LIBS-P 响应显示与所有土壤的总磷高度相关 (R2 > 0.99)。然而，LIBS 的灵敏度在土壤之间存在显着差异，因为校准曲线的斜率随着含沙量的增加而增加，导致最沙质的估计检测限为 10 mg kg-1，最粘质的为 122 mg · kg-1土壤。这些限制表明通过 LIBS 对沙质和壤质沙质土壤中的总磷进行定量评估是可行的，因为它们低于土壤中典型的总磷浓度。给定的研磨处理会根据土壤类型产生不同的粒度分布，从而产生不同的 LIBS-P 结果。因此，需要在分析之前指定所需的土壤样品均质程度的程序。研磨后筛分可能是一种选择，但应该进行测试。除含有羟基磷灰石的土壤外，添加了 Fe(III) 磷酸盐、磷酸钾和植酸的土壤具有相似的 LIBS-P，这导致响应显着降低。这些结果表明，对于潮湿地区的非钙质土壤，磷灰石仅占总磷的一小部分，与磷化学性质相关的基质效应较小。