Evolution of iron minerals in a 100 years-old Technosol. Consequences on Zn mobility

Abstract

International audienceThe prediction of the long term trace element mobility in anthropogenic soils would be a way to anticipate land management and should help in reusing slightly contaminated materials. In the present study, iron (Fe) and zinc (Zn) status evolution was investigated in a 100-year old Technosol. The site of investigation is an old brownfield located in the Nord-Pas-de-Calais region (France) which has not been reshaped since the beginning of the last century. The whole soil profile was sampled as a function of depth, and trace elements mobility at each depth was determined by batch leaching test. A specific focus on Fe and Zn status was carried out by bulk analyses, such as selective dissolution, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Fe and Zn status in the profile samples was also studied using laterally resolved techniques such as μ-particle induced X-ray emission (μ-PIXE) and μ-Rutherford backscattering spectroscopy (μ-RBS). The results indicate that (i) Fe is mainly under Fe(III) form, except a minor contribution of Fe(II) in the deeper samples, (ii) some Fe species inherited from the past have been weathered and secondary minerals are constituted of metal-bearing sulphates and Fe (hydr)oxides, (iii) ferrihydrite is formed during pedogenesis (iv) 20 to 30% more Fe (hydr)oxides are present in the surface than in depth and (v) Zn has tetrahedral coordination and is sorbed to phases of increasing crystallinity when depth increases. Zn-bearing phases identified in the present study are: complex Fe, Mn, Zn sulphides, sulphates, organic matter, and ferrihydrite. Soil formation on such material does not induce a dramatic increase of Zn solubility since efficient scavengers are concomitantly formed in the system. However, Technosols are highly heterogeneous and widely differ from one place to another. The behavior examined in this study is not generic and will depend on the type of Technosol and on the secondary minerals formed as well as on the nature and amount of organic matter

A meta‐analysis of carbon content and stocks in Technosols and identification of the main governing factors

“…Overall, exponential and log-log models tend to High contents of SOC* are reported at various depths: 18 observations have SOC* content higher than 20% between 0 and 10 cm of average sampling depth, and nine more observations have SOC* content higher than 20% at above 35, 120 and 180 cm average sampling depth (three observations each). These nine last observations concern industrial soils from Coussy et al (2017). It is worth noting that the maximum SOC* content value of this graph is encountered at 180 cm average sampling depth.…”

“…Standard deviation associated with SOC* content is 7.45%. Maximum SOC* content is 48.7%; it relates to a deep horizon (175-185 cm) of industrial soil that includes coal and slag fragments (Coussy et al, 2017). The high difference between mean and median is explained by a high quantity of values above 10% of SOC*: 66 data over the 687 (9.6% of the data).…”

“…Among the 19 outliers of industrial soils, four pieces of data concern soils developed in an ash settling pond (Uzarowicz, Kwasowski, Spiewak, & Switoniak, 2018), 13 concern different horizons of a Technosol made of smelter slags (containing high amounts of coal, Coussy et al, 2017;Dagois et al, 2016), and two concern fly ashenriched soils (Hartmann, Fleige, & Horn, 2010).…”

Quantum mechanics of rectilinear orbits of the Coulomb-Kepler problem

“…It turns out that the observables do not depend on the KS phase Φ, see (3). As a consequence, the mean values of the position and velocity depend on the difference φ: =Φ − Φ , only.…”

“…(3-72) in [4]. Rutherford backscattering spectrometry (RBS) is a widely used analytical tool in the sciences [10]; for recent works see for instance: in solid state and surface physics [16,5], in earth science [3], in astrophysics [6], or in archaeology [9]. As compared to scattering theory which is concerned with asymptotic states, here we start with a wave function which is prepared at time t = 0 for a finite distance and can be continuously followed for t > 0.…”