Heavy metal sorption and desorption capacity of soils containing endogenous contaminants

Our plain-English summary of Heavy metal sorption and desorption capacity of soils containing endogenous contaminants, by E.F. Covelo, F.A. Vega, M.L. Andrade (Journal of Hazardous Materials, 2007).

The study

• Authors: E.F. Covelo, F.A. Vega, M.L. Andrade
• Journal: Journal of Hazardous Materials
• Published: 2007;143(1-2):419-30
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Soils on serpentinites in some regions of northwestern Spain have been the subject of agricultural management practices involving the use of fertilizers and various types of organic waste containing heavy metals. Although such practices have facilitated crop growth, they have also raised the natural contents in heavy metals of the soils. In this work, three ferralic Cambisols and another three mollic Leptosols with high Cr and Ni contents were used to study competitive sorption and desorption of six heavy metals via K(d100), which was employed as a measure of the ability of the soils to adsorb and retain each metal. Lead was found to be the metal sorbed and retained to the greatest extent, and Cd, Ni and Zn those sorbed and retained in the smallest amounts. Although the ferralic Cambisols were found to contain greater amounts of natural heavy metals, they exhibited an increased ability to adsorb and retain the body of metals relative to the mollic Leptosols by effect of their increased contents in clay and Fe, Mn and Al oxides, in addition to their higher ion-exchange capacity. Based on the results, Pb and Cu are strongly bound, and Zn, Cd and Ni weakly bound, to the soils. The ferralic Cambisols exhibited an increased capacity to adsorb and retain Cd, Ni, Zn and--especially--Cr than the mollic Leptosols; the latter, however, proved more effective in adsorbing and retaining Cu and Pb by virtue of their increased organic matter contents. Copper sorption and retention, and Pb retention, were found to be correlated with the content in organic matter and that in vermiculite--which was only present in the mollic Leptosols--in the clay fraction.

In plain English

This laboratory study examined soils, not people, and did not study asbestos or health. The authors collected topsoil from six soils formed on serpentinitic rock in the province of Coruña, northwestern Spain: three ferralic Cambisols and three mollic Leptosols with naturally high chromium and nickel contents. They exposed the soils to solutions of six heavy metals in competition (cadmium, chromium, copper, nickel, lead and zinc) at 5 to 300 mg per litre, buffered at pH 4.5. They then measured how much of each metal the soils took up and how much they kept after a desorption step. Lead was taken up and kept most by all soils, and cadmium, nickel and zinc were always last. The Leptosols retained near-zero amounts of those three. Overall, the Cambisols took up and retained more of the metals combined, which the authors ascribed to their higher clay, iron, manganese and aluminium oxide contents and higher cation-exchange capacity. The Leptosols had higher copper sorption. The authors concluded that lead and copper bind strongly to these soils, and zinc, cadmium and nickel more weakly.

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 batch sorption and desorption experiment on soil samples (competitive sorption of several metals at once)
• Who was studied: six topsoils (0 to 30 cm) developed on serpentinitic rocks in the province of Coruña, NW Spain: three Ferralic Cambisols (FC1, FC2, FC3) and three Mollic Leptosols (ML1, ML2, ML3)
• Exposure: laboratory addition of Cd, Cr, Cu, Ni, Pb and Zn in nitrate form at 5 to 300 mg per litre, buffered at pH 4.5; comparisons made at an added concentration of 100 mg per litre (Kd100). No asbestos exposure was studied.
• Main results:
  • Lead was preferentially sorbed and retained by all six soils. Cadmium, nickel and zinc were invariably last in the sorption and retention sequences.
  • After desorption, the Mollic Leptosols (ML1, ML2, ML3) retained no cadmium, nickel or zinc, with near-zero Kd100 values (Table 6 shows a zinc retention value of 3.15 L/kg in ML3).
  • For all metals combined (Kd100sp), the Ferralic Cambisols had higher sorption (14.29 to 15.06 L/kg) and retention (157.41 to 219.8 L/kg) than the Mollic Leptosols (sorption 3.59 to 4.63 L/kg; retention 54.87 to 88.41 L/kg). FC3 had the highest sorption and FC1 the highest retention.
  • The Mollic Leptosols had higher copper sorption and higher copper and lead retention capacity than the Cambisols, based on principal component analysis.
  • Copper sorption and retention, and lead retention, were correlated with organic matter content and with vermiculite in the clay fraction.
• The authors' conclusion: The authors concluded that lead and copper bind strongly, and zinc, cadmium and nickel more weakly, to the studied soils. They also wrote that the results suggest a need to control heavy metal contents of amendments and fertilizers applied to these soils.
• Limitations the authors state:
  • Most sorption and desorption isotherms were irregular because of soil heterogeneity and competition between metals for binding sites, especially for desorption and for cadmium, nickel and zinc.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Serpentinite, vermiculite.

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