Development of a hyperspectral imaging technique using LA-ICP-MS to show the spatial distribution of elements in soil cores

Abstract

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a versatile analytical technique that can create qualitative images delineating the spatial distribution of elements in different samples. However, there is no demonstration of this technique in imaging the spatial distribution of elements in soil cores. Herein, we developed a hyperspectral imaging method using LA-ICP-MS to visualize the spatial distribution of selected elements in soil cores as a proof of concept. Soil cores were collected in plastic liners, frozen at −20°C; cut uniformly in halves using a band saw. The surface of the intact cores was ablated using a 213 nm laser optimized with the following parameters: spot size 100 µm, laser energy of 7 mJ, and scan speed of 220 µms−1. Two-dimensional images of the soil cores were created for Ca, Mg, P, K, Na, Zn, Fe, Co, and Mn using the iolite software. The new imaging method was very effective in showing that different crop management systems and fertilizer applications altered the levels and spatial distribution of Ca, Mg, P, K, Na, Zn, Fe, Co, and Mn in the evaluated soil cores. The results show that the developed method has great potential in multi elemental imaging of intact soil cores. This could have huge implications in environmental impact assessments, soil resource evaluation, agriculture crop production and the effectiveness of land use or land management systems in modulating the spatial distribution of elements within the soil.