Energy dispersive X‐ray fluorescence analysis to estimate the maximum temperature reached in burned soils from an Amazonian region

Abstract

Determining the maximum temperature reached in soil during burning is important when evaluating fire intensity. Forest conversion is an ongoing process in the Amazon ecosystem. It is of utmost importance to predict fire effects on soil properties and avoid damaging environmental systems. Spectroscopic methods combined with multivariate statistics may provide chemical and mineralogical information from soil. This study aims at predicting the maximum temperature reached in Oxisols from an Amazonian region in Brazil. Slash‐and‐burn and pasture samples collected after fire events and unburned forest soil samples submitted to heating (250–800 °C) were investigated. Energy‐dispersive X‐ray fluorescence (EDXRF) was used to acquire chemical data. The experimental procedure is rapid and requires minimal sample preparation and no hazardous chemical reagents. The EDXRF data, combined with partial least squares regression, were applied in controlled‐heated samples from five different sites of forest, pasture, and slash‐and‐burn areas. Estimated temperatures for burned samples ranged from 317 to 609 °C. Considering the instrumental advantages and the achieved results, the use of EDXRF combined with multivariate analysis is a feasible alternative technology to evaluate fire effects in soil.

Multivariate Analysis with XRD Data as a Fingerprinting Technique to Study Burned Soils

“…Prior to heating, samples were left to air dry at room temperature for 24 h, then grounded and sieved to grain size < 125 µm in order to obtain homogeneous samples. Simulated burning inside a muffle was performed to characterize mineralogical changes in the soil due to heating [13]. Temperature levels studied were 25 (no heating), 250, 400, 530, 600 and 800 °C.…”

“…Approximately 5.0 g of sample was heated in a porcelain capsule, Prior to heating, samples were left to air dry at room temperature for 24 h, then grounded and sieved to grain size < 125 µm in order to obtain homogeneous samples. Simulated burning inside a muffle was performed to characterize mineralogical changes in the soil due to heating [13]. Temperature levels studied were 25 (no heating), 250, 400, 530, 600 and 800 • C. Approximately 5.0 g of sample was heated in a porcelain capsule, from 40 • C to the temperature peak, remaining for 20 min at this temperature.…”