Does Soil Drying in a Lab Affect Arsenic Speciation in Strongly Contaminated Soils?

Anna Karczewska,Agnieszka Dradrach,Bernard Gałka,Katarzyna Szopka

doi:10.3390/min12020223

Anna Karczewska, Agnieszka Dradrach + Show 2 more

Open Access

https://doi.org/10.3390/min12020223

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Abstract

This study examined the changes in extractability and fractionation of arsenic (As) that can be caused by the drying of strongly polluted anoxic soil samples. Two untreated and manure-amended soils were incubated for 7 and 21 days in flooded conditions. Thereafter, As water- and 1 M NH4NO3-extractability and As fractionation in a 5-step sequential extraction according to Wenzel were examined in fresh, oven-dried and air-dried samples. Soil treatment with manure considerably affected the results of the sequential extraction. Air-drying caused a significant decrease in As extractability with 1 M NH4NO3 and in As concentrations in the F1 fraction. The highest reduction of extractability (30–41%) was found in manure-treated soils. Oven-drying resulted in a smaller reduction (5–34%) of As extractability. These effects were explained by opposing processes of As mobilization and immobilization. Sequential extraction did not allow for balancing As redistribution due to drying, as As loss from the F1 fraction was smaller than the confidence intervals in the other fractions. The results showed that for the precise determination of As extractability in anoxic soils, fresh samples should be analyzed. However, oven-dried samples may be used for a rough assessment of environmental risk, As the order of magnitude of easily soluble As did not change due to drying.

Highlights

Academic Editor: Kyoung-Woong KimArsenic belongs to the most toxic elements; its high concentrations in the environment are always a matter of special concern [1,2]
The aim of this study was to examine the effects of two different drying methods on the extractability of As, and on its fractionation in soils heavily contaminated with tailings that were amended with an organic fertilizer and subjected to reducing conditions due to waterlogging
This study proved that soil sample pretreatment, i.e., drying, can significantly affect the extractability and fractionation of As in strongly polluted soils incubated under flooded conditions

Summary

Introduction

Academic Editor: Kyoung-Woong KimArsenic belongs to the most toxic elements; its high concentrations in the environment are always a matter of special concern [1,2]. The strong enrichment of soils in As usually occurs in the sites associated with its historical mining and processing. One of these such sites is Złoty Stok (formerly Reichenstein), a leading European producer of arsenic for over two centuries, until 1962 [3,4,5,6]. There is no need to emphasize that it is not the total concentrations, but primarily the soluble forms of toxic elements that determine the environmental risk associated with soil pollution. Soluble forms of elements are those that can be released As a result of changing soil conditions, such As acidification, decomposition, or dissolution of solid soil components crucial for the binding of particular elements, for instance, the reductive dissolution of Mn and Fe (hydr)oxides in the case of

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