Quality reference values for rare earth elements in soils from one of the last agricultural frontiers in Brazil

Yuri Jacques Agra Bezerra Da Silva,Marcos Paulo Rodrigues Teixeira,Ronny Sobreira Barbosa,Cácio Luiz Boechat,Tatiana Dos Santos Silva,Vijay P Singh,Ygor Jacques Agra Bezerra Da Silva,Eliabe Barros De Oliveira,Clístenes Williams Araújo Do Nascimento,Antonny Francisco Sampaio De Sena

doi:10.1590/1678-992x-2020-0069

Yuri Jacques Agra Bezerra Da Silva, Marcos Paulo Rodrigues Teixeira + Show 8 more

Open Access

https://doi.org/10.1590/1678-992x-2020-0069

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Abstract

ABSTRACT: Environmental impacts caused by the addition of rare earth elements (REEs) to agricultural soils are a growing concern. The sedimentary basin of the Gurgueia River is located in one of the last agricultural frontiers in Brazil; nevertheless, data regarding quality reference values (QRVs) for REEs in soils are still scarce. The objective of this study was therefore to determine the natural concentration and establish the QRVs of REEs in soils of Gurgueia watershed, Brazil. Fifty-five composite soil samples were collected at sites under no or minimal anthropic interference. The average REE natural concentrations in soils from the Gurgueia watershed were lower than those found in other regions of Brazil and worldwide, following the order (mg kg−1): Ce (14.01) > Nd (6.19) > La (5.52) > Pr (2.51) > Sm (1.45) > Gd (0.93) > Dy (0.63) > Er (0.42) > Yb (0.39) > Tb (0.28) > Eu (0.26) > Lu (0.20). The parent material was the main factor that controlled the distribution of REEs in soils. The QRVs in soils followed the order (mg kg−1): Ce (18.8) > Nd (7.92) > La (6.32) > Pr (3.3) > Sm (1.97) > Gd (1.35) > Dy (0.85) > Er (0.55) > Yb (0.47) > Tb (0.37) > Lu (0.25). These values serve as a basis to assist the development of legislation, including REE thresholds for Brazilian soils.

Highlights

Rare earth elements (REEs) are composed of 15 elements of the lanthanides (Z = 57-71)
The lowest concentrations of light rare earth elements (LREEs) and heavy rare earth elements (HREEs) in the soils from Gurguéia watershed are governed by parent material, with a predominance of soils originating from quartz sandstones
Silva et al (2016) showed that the parent material controlled the concentration of REEs in soils from the northeastern region of Brazil

Summary

Introduction

Rare earth elements (REEs) are composed of 15 elements of the lanthanides (Z = 57-71) These elements are usually separated into two groups known as light rare earth elements (LREEs; La-Eu) and heavy rare earth elements (HREEs; Gd-Lu) (Lara et al, 2018; Dinali et al, 2019; Silva et al, 2019). The increasing storage of REEs in soils has caused adverse impacts on the environment (Liu et al, 2019; Omodara et al, 2019) and human health (Bai et al, 2019; Pagano et al, 2019), especially in agricultural regions (Ramos et al, 2016; Silva et al, 2019; Jin et al, 2019). Knowledge on the background concentration and quality reference values (QRVs) is fundamental to manage soils properly, preventing risks to humans and environment (Nogueira et al, 2018)

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