Abstract
Chromium is an element that possess several oxidation states and can easily pass from one to another, so its behavior in soils is very complex. For this reason, determining its fate in the environment can be difficult. In this research work we tried to determine which factors affect the chromium fractionation in natural soils, conditioning chromium mobility. We paid special attention to the parent material. For this purpose, extraction experiments were carried out on spiked soils incubated for 50–60 days, using H2O, CaCl2 and diethylenetriaminepentaacetic acid (DTPA). The most efficient extraction rate in all soils was achieved using water, followed by CaCl2 and DTPA. We obtained models with an adjusted R2 of 0.8097, 0.8471 and 0.7509 for the H2O Cr, CaCl2 Cr and DTPA Cr respectively. All models were influenced by the amount of chromium added and the parent material: amphibolite and granite influenced the amount of H2O Cr extracted, and schist affected the other two fractions (CaCl2 and DTPA). Soil texture also played an important role in the chromium extraction, as well as the amounts of exchangeable aluminum and magnesium, and the bioavailable phosphorus. We concluded that it is possible to make relatively accurate predictions of the behavior of the different Cr fractions studied, so that optimized remediation strategies for chromium-contaminated soils can be designed on the basis of a physicochemical soil characterization.
Highlights
Chromium is one of the most common elements on earth: it occupies the seventh position in terms of abundance, but most of this element is found in the earth’s core or in the mantle [1]
Extraction experiments were carried out on spiked soils incubated for 50–60 days, using H2O, CaCl2 and diethylenetriaminepentaacetic acid (DTPA)
All models were influenced by the amount of chromium added and the parent material: amphibolite and granite influenced the amount of H2O Cr extracted, and schist affected the other two fractions (CaCl2 and DTPA)
Summary
Chromium is one of the most common elements on earth: it occupies the seventh position in terms of abundance, but most of this element is found in the earth’s core or in the mantle [1]. The most stable and common forms in nature are the trivalent, Cr(III) and the hexavalent chromium, Cr(VI) [4]. Both species of Cr present very different characteristics, and their movement and retention in the soil is conditioned by different factors: for example, the retention of Cr(III) is greatly affected by the texture, and it is more retained in silty soils that present high pH; while Cr(VI) is better retained when the soil pH drops, or when organic matter or iron oxides are added (materials positively charged) [5]
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