Senesi G S, Dell'Aglio M, Gaudiuso R, De Giacomo A, Zaccone C, De Pascale O, Miano T M, Capitelli M
IMIP-CNR-Bari, Via Amendola 122/D, Bari 70126, Italy.
Environ Res. 2009 May;109(4):413-20. doi: 10.1016/j.envres.2009.02.005. Epub 2009 Mar 9.
Soil is unanimously considered as one of the most important sink of heavy metals released by human activities. Heavy metal analysis of natural and polluted soils is generally conducted by the use of atomic absorption spectroscopy (AAS) or inductively coupled plasma optical emission spectroscopy (ICP-OES) on adequately obtained soil extracts. Although in recent years the emergent technique of laser-induced breakdown spectroscopy (LIBS) has been applied widely and with increasing success for the qualitative and quantitative analyses of a number of heavy metals in soil matrices with relevant simplification of the conventional methodologies, the technique still requires further confirmation before it can be applied fully successfully in soil analyses. The main objective of this work was to demonstrate that new developments in LIBS technique are able to provide reliable qualitative and quantitative analytical evaluation of several heavy metals in soils, with special focus on the element chromium (Cr), and with reference to the concentrations measured by conventional ICP spectroscopy. The preliminary qualitative LIBS analysis of five soil samples and one sewage sludge sample has allowed the detection of a number of elements including Al, Ca, Cr, Cu, Fe, Mg, Mn, Pb, Si, Ti, V and Zn. Of these, a quantitative analysis was also possible for the elements Cr, Cu, Pb, V and Zn based on the obtained linearity of the calibration curves constructed for each heavy metal, i.e., the proportionality between the intensity of the LIBS emission peaks and the concentration of each heavy metal in the sample measured by ICP. In particular, a triplet of emission lines for Cr could be used for its quantitative measurement. The consistency of experiments made on various samples was supported by the same characteristics of the laser-induced plasma (LIP), i.e., the typical linear distribution confirming the existence of local thermodynamic equilibrium (LTE) condition, and similar excitation temperatures and comparable electron number density measured for all samples. An index of the anthropogenic contribution of Cr in polluted soils was calculated in comparison to a non-polluted reference soil. Thus, the intensity ratios of the emission lines of heavy metal can be used to detect in few minutes the polluted areas for which a more detailed sampling and analysis can be useful.
土壤被一致认为是人类活动释放的重金属最重要的汇之一。对天然土壤和污染土壤的重金属分析通常是通过对充分获取的土壤提取物使用原子吸收光谱法(AAS)或电感耦合等离子体发射光谱法(ICP - OES)来进行的。尽管近年来新兴的激光诱导击穿光谱技术(LIBS)已被广泛应用,并且在简化传统方法的情况下,越来越成功地用于土壤基质中多种重金属的定性和定量分析,但该技术在能够完全成功应用于土壤分析之前仍需要进一步确认。这项工作的主要目的是证明LIBS技术的新进展能够对土壤中的几种重金属提供可靠的定性和定量分析评估,特别关注元素铬(Cr),并参考通过传统ICP光谱法测量的浓度。对五个土壤样品和一个污水污泥样品进行的初步定性LIBS分析检测到了多种元素,包括铝(Al)、钙(Ca)、铬(Cr)、铜(Cu)、铁(Fe)、镁(Mg)、锰(Mn)、铅(Pb)、硅(Si)、钛(Ti)、钒(V)和锌(Zn)。其中,基于为每种重金属构建的校准曲线的线性度,即LIBS发射峰强度与通过ICP测量的样品中每种重金属浓度之间的比例关系,也可以对铬、铜、铅、钒和锌等元素进行定量分析。特别是,铬的一组三线发射谱线可用于其定量测量。对各种样品进行的实验的一致性得到了激光诱导等离子体(LIP)相同特性的支持,即典型的线性分布证实了局部热力学平衡(LTE)条件的存在,并且为所有样品测量的激发温度相似且电子数密度相当。与未受污染的参考土壤相比,计算了污染土壤中铬的人为贡献指数。因此,重金属发射谱线的强度比可用于在几分钟内检测出需要进行更详细采样和分析的污染区域。