Comparing Methods for Extracting Heavy Metals from Histosols for Establishing Quality Reference Values

Eduardo Lima ,Izabella Bezerra Coutinho,Nelson Moura Brasil Do Amaral ,Daniel Vidal Pérez

doi:10.1590/18069657rbcs20150097

Abstract

The diversity of methods for heavy metal extraction from soils complicates comparison of results used by environmental agencies to establish quality reference values. The aim of this study was to evaluate three soil digestion methods regarding the solubilizing capacity of Ba, Cr, Cu, Fe, Mn, Ni, Pb and Zn, and to propose a standard method to establish Quality Reference Values (QRVs) for Brazilian Histosols. Twenty soil samples were selected to evaluate the USEPA 3051, USEPA 3051A and Aqua Regia methods in a closed system. The methods tested were statistically similar regarding Cu, Fe and Mn extraction from soils. However, the methods can not be considered similar for Ba, Cr, Ni, Pb and Zn; Aqua Regia recorded the highest levels, except for Ba. The Aqua Regia method proved suitable for metal extraction from soils with organic characteristics and can be used to establish QRVs.

Highlights

Histosols are poorly evolved and fragile soils that formed under restricted drainage conditions or under humid, cold and water-saturated environments
The heavy metal contents in reference samples SRM 2709 and SRM 2782 recovered using the soil digestion methods are shown in table 3
The digestion methods showed different heavy metal solubilizing capacities that varied according to the element and chemical and physical characteristics of the Histosol samples

Summary

Introduction

Histosols are poorly evolved and fragile soils that formed under restricted drainage conditions or under humid, cold and water-saturated environments They have low geographical representativeness (approximately 1 %) compared to the other Brazilian soil orders; they play important economic, social and environmental roles (Valladares et al, 2008). They are extensively used by family farmers in subsistence production systems or even olericulture. Given their high organic matter content, they may accumulate pollutants and/or be degraded depending on the development of anthropic activities. Assessing the natural content of heavy metals in soils with low anthropic impact and proposing Quality Reference Values (QRVs) of specific heavy metals for Histosols is essential for monitoring these areas

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Conclusion