Assessing the origin and fate of Cr, Ni, Cu, Zn, Pb, and V in industrial polluted soil by combined microspectroscopic techniques and bulk extraction methods

Our plain-English summary of Assessing the origin and fate of Cr, Ni, Cu, Zn, Pb, and V in industrial polluted soil by combined microspectroscopic techniques and bulk extraction methods, by R. Terzano, M. Spagnuolo, B. Vekemans, et al (Environmental Science & Technology, 2007).

The study

• Authors: R. Terzano, M. Spagnuolo, B. Vekemans, W. De Nolf, K. Janssens, G. Falkenberg, S. Fiore, P. Ruggiero
• Journal: Environmental Science & Technology
• Published: 2007;41(19):6762-9
• Cited by: 45 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The major geochemical forms of Cr, Ni, Cu, Zn, Pb, and V in a soil from an industrial polluted site in the south of Italy were determined by means of synchrotron X-ray microanalytical techniques such as coupled micro-X-ray fluorescence/micro-X-ray diffraction and micro-X-ray absorption near edge structure spectroscopy in combination with bulk extraction methods (sequential extraction procedures, EDTA extractions, and toxicity leaching characteristic procedure tests). Cr, Ni, Zn, and Cu were found in spinel-type geochemical forms (chromite, trevorite, franklinite, zincochromite, and cuprospinel) and often in association with magnetite and hematite. Vwas mainly present as V(V) associated with iron-oxides or in the form of volborthite [Cu3(OH)2V2O7.2H2O]. Pb was speciated as minium (Pb3O4), lanarkite [Pb2O(SO4)], and, in association with Cr(VI), as crocoite (PbCrO4). In general, despite a high total concentration, metals appear to be speciated for the most part as rather insoluble geochemical forms. However, particular attention should be paid to Zn, Cu, V, and Pb that show non-negligible mobilizable fractions. On the basis of the geochemical forms identified, among others, two major former industrial activities were tentatively ascribed as being responsible for the observed major pollution: polyvinyl chloride and cement-asbestos productions.

In plain English

This was a laboratory study of soil chemistry, not a study of people or health. The authors sampled surface soil across a 60-hectare industrial polluted site in southern Italy. They studied the most heavily contaminated sample in detail, using synchrotron X-ray microscopy and chemical extraction tests. Chromium, vanadium, zinc, copper, nickel and lead all significantly exceeded Italian legal trigger values. Most of the chromium (93%) and nickel (77%) was in the least soluble fraction. A chemical (EDTA) extraction released 39% of the copper, about 30% of the zinc, 27% of the lead and 21% of the vanadium. All the metals passed a standard leaching test. Electron microscopy found asbestos fibers in the soil, but the article does not name the fiber type. The authors concluded that most of the metals were in rather insoluble forms and that zinc, copper, vanadium and lead deserved particular attention. They attributed the pollution most probably to two former industries on the site: polyvinyl chloride (PVC) production and the manufacture of cement-asbestos products.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory analysis of soil from a polluted industrial site: synchrotron X-ray microanalysis (micro-X-ray fluorescence, micro-X-ray diffraction, micro-XANES) combined with bulk chemical extraction tests (sequential extractions, EDTA extraction, TCLP leaching test)
• Who was studied: Surface soil (0 to 30 cm deep) sampled on a 100 m grid over 60 ha of an industrial polluted site in the south of Italy. The most heavily contaminated sample was chosen for detailed study, and seven thin sections were prepared from it.
• Exposure: Heavy metal contamination (chromium, including Cr(VI), nickel, copper, zinc, lead and vanadium) from former industrial activities on the site, which operated from the 1960s to the 1980s. Asbestos fibers were seen in the soil by SEM; no fiber type is named.
• Main results:
  • Total concentrations of chromium, vanadium, zinc, copper, nickel and lead in the studied soil all significantly exceeded the trigger values in Italian law (D.Lgs. 152/2006). Cr(VI) was also above the reference limits.
  • Asbestos fibers were found in the soil by scanning electron microscope (SEM) observation.
  • In the sequential extraction, chromium was almost completely (93%) in the residual, least soluble fraction.
  • 77% of the nickel was in the residual fraction, and EDTA-extractable nickel was 8%.
  • Lead was mainly in the reducible fraction (60%), and 27% of the lead was extractable by EDTA.
  • About 30% of the total zinc could be leached by EDTA extraction.
  • EDTA extraction dissolved 39% of the total copper.
  • Of the total vanadium, 16% was in the oxidizable fraction and 21% was extracted by EDTA.
  • All the metals passed the TCLP leaching test. The authors noted that the soil's alkaline pH contributed to preventing leaching.
• The authors' conclusion: The authors concluded that, despite high total concentrations, most of the metals were in rather insoluble forms, so the environmental danger was estimated to be much lower than expected. Zinc, copper, vanadium and lead needed particular attention because of their mobilizable fractions. They attributed the spinel-type metal pollution most probably to cement-asbestos products manufacture, and other forms (vanadium, lead pigments) to PVC production.
• Limitations the authors state:
  • The microscopic data come only from tiny portions of the whole sample.
  • The microscopic techniques could not clarify whether the metals were sorbed on hematite. The beamline was not bright enough for interpretable micro-EXAFS data, which could have resolved this.

Topics

Medical terms in this study, explained in our Lexicon: X-Ray Diffraction (XRD), Hematite.

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