Potential use of Rare Earth Oxides as Tracers for Soil Erosion and Aggregation Studies

Abstract

Most existing soil loss data are spatially‐averaged, though various tracing techniques have been used for obtaining spatially‐distributed data. Spatially‐distributed soil erosion data are needed for validating physically‐based erosion prediction models and for better understanding soil erosion dynamics. The objectives of this study were to evaluate the feasibility of using rare earth element (REE) oxides directly as tracers for soil erosion studies by examining their binding ability with soil materials, and also to test a quick acid‐extraction procedure. Five REE oxide powders were directly mixed with a Miami silt loam soil (fine‐loamy, mixed, mesic Typic Hapludalfs) and then leached with deionized water in a soil box to evaluate the mobility of REEs. Following leaching, soil samples were sectioned in 25‐mm increments and analyzed for REEs. The REE‐tagged soil was wet sieved to obtain REE concentrations in each aggregate size group. A simple acid‐leaching method was used to extract REEs from all soil samples. The extracts were analyzed by Inductively Coupled Plasma‐Mass Spectrometry (ICP‐MS) techniques. The data indicated that the maximum coefficient of variation of the proposed procedure was <10% for all REEs. The REE oxides were uniformly incorporated into soil aggregates of different sizes (>53 μm) and were bound with silt‐size particles. This finding shows that the direct use of REE oxides is feasible, which should be superior to other REE‐tagged particulate tracers because it eliminates the need of tagging exotic particles with REEs. Also, direct mixing of a trace amount of REEs does not substantially alter physicochemical properties of soil particles and aggregates. This work has shown that REE oxides have a great potential for tracing soil erosion and aggregation.

Effects of soil type on leaching and runoff transport of rare earth elements and phosphorous in laboratory experiments

“…The results showed that Ce migrated downward approximately 1 cm every year in acid soils, 0.2 cm in neutral soils, and almost none in alkaline soils. Zhang et al (2001) investigated Ce and Nd transport characteristics with the leaching experiment of soil columns, and it was found that even if the REEs amount reached 50% of the desorption rate of surface soils and the rainfall amount in the simulated rainfall experiments reached 1,000 mm, in most cases the migration depth of Ce and Nd was within 4 cm in nine different kinds of soils. In a few cases, the REEs were leached to a depth of 10 cm, but no 141 Ce and 147 Nd were detected in the leachate.…”

Multiple rainfall event pollution transport by sustainable drainage systems: the fate of fine sediment pollution

“…The REO tracers used for the car park, roof and road were Nd, Sm, Gd, Tb; Y, La, Ce, Pr; Dy, Ho, Er, Yb, respectively. The sediment was tagged following the detailed methodology described by Zhang et al (2001Zhang et al ( , 2003, at a tracer concentration rate of 10 g/kg of sediment (Allen et al 2015), and released evenly onto the urban surfaces only once at the beginning of the sampling period. Tagged sediment was designed to mimic naturally occurring urban sediment pollution, in both mass and particle size distribution (PSD).…”

Traçadores: o uso de agentes químicos para estudos hidrológicos, ambientais, petroquímicos e biológicos

“…Esta técnica é especialmente notável pela alta especificidade e sensibilidade, como pode-se observar no trabalho de revisão deste tema de Bonardi e colaboradores. 78 A utilização de traçadores radioativos também tem fornecido imensa contribuição para o estudo de processos ambientais, tais como o estudo dos processos de erosão, 82 7 Be meia vida de 53 dias, são formados naturalmente na atmosfera e depositados na superfície por precipitação, distribuindo-se em diferentes profundidades do solo. Esses dois elementos, quando utilizados em conjunto como traçadores, fornecem uma identificação mais precisa do processo de erosão nos rios.…”