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The Influence of Soil Moisture on Oxide Determination in Tropical Soils via Portable X‐ray Fluorescence
Author(s) -
Ribeiro Bruno Teixeira,
Weindorf David C.,
Silva Bruno Montoani,
Tassinari Diego,
Amarante Larissa Carvalho,
Curi Nilton,
Guimarães Guilherme Luiz Roberto
Publication year - 2018
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2017.11.0380
Subject(s) - soil water , water content , environmental science , moisture , soil texture , soil science , leaching (pedology) , saturation (graph theory) , soil test , weathering , environmental chemistry , mineralogy , chemistry , geology , mathematics , geochemistry , geotechnical engineering , organic chemistry , combinatorics
Core Ideas We verified the effect of soil moisture on portable X‐ray fluorescence (pXRF) results with undisturbed soil samples. Heavy oxides (Fe and Ti) are much less affected by soil moisture than light oxides (Si and Al). The power model described the effect of soil moisture on pXRF results for SiO 2 and Al 2 O 3 well A practical correction factor for SiO 2 and Al 2 O 3 was proposed for accurate in‐field measurements Portable X‐ray fluorescence (pXRF) has been used in many countries to assess the total elemental composition of soils and has agronomic, pedological, and environmental applications. This technique is still incipient in tropical developing countries like Brazil but has potential to improve and decrease the costs of research. Soil moisture is one of the most important factors influencing pXRF results. This pilot study evaluated how soil moisture affects elemental concentrations of oxides common in Brazilian soils (SiO 2 , Al 2 O 3 , Fe 2 O 3 , TiO 2 , and P 2 O 5 ) as assessed by pXRF. Undisturbed soil samples were collected from the surface and subsurface horizons of six representative Brazilian soils (representing ∼40% of the country) with variable texture, weathering, or leaching status. Soil moisture ranged from complete saturation to oven‐dry. During drying, six pXRF measurements were made and oxide contents were recorded. In all soils, the P 2 O 5 content was below the pXRF detection limit, and SiO 2 and Al 2 O 3 were strongly influenced by soil water content. As soil moisture increased, SiO 2 and Al 2 O 3 contents decreased (described by a power model, y = a – bx c ). The TiO 2 content was much less affected by soil moisture, whereas Fe 2 O 3 was not significantly affected by soil moisture. Soil texture and weathering status are closely related to variation in the SiO 2 and Al 2 O 3 contents determined by the pXRF with soil moisture. These findings are critical to the appropriate application of pXRF in tropical countries featuring oxide‐laden soils. For in‐field measurement of oxides affected by soil moisture (Si and Al), a practical correction factor was determined.