Using LIBS to investigate elemental content in plants and composts during soil remediation processes

Laser Induced Breakdown Spectroscopy (LIBS) is a fast and multi-elemental analytical technique particularly suitable for the qualitative and quantitative analysis of several elements in solid samples including metal alloys for metallurgy and jewellery, and cultural heritage materials. Due to negligible or virtually absent pre-treatments of samples, high sensitivity, simultaneous multielemental detection of major and trace elements, and especially capability for microanalysis with low sample consumption, LIBS has been recently used also for analysis of environmental samples, i.e., meteorites, soils, sediments, and vegetables. In the present work, the authors test the feasibility of the LIBS technique to be used during the remediation/restore of soils by plants (phytoremediation) and compost application. In detail, Cr, Cu, Fe, Pb, and Zn content were investigated in four plant species (i.e., Atriplex halimus, Brassica napus, Rucola sativa, and Sorghum bicolor) and two different composts, and concentration values compared with those obtained by ICP-OES. Although the LODs for the LIBS-detected elements were sometimes quite higher if compared with other analytical techniques, data obtained underline the capability of LIBS method for the monitoring of the studied elements in plants growing in polluted soils, also allowing to calculate a "translocation" factor between roots and leaves. Good results were obtained also for composts. Furthermore, as some metals like Cu and Fe have to be considered, below certain concentrations, micronutrients, the authors propose the application of the LIBS in investigating deficit in plant uptake (e.g., Fe-chlorosis), and/or to evaluate the concentration of nutrients (e.g., Ca, Mg, Mn) in amendments/fertilizers.