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Calcium chloride washing of calcareous sediment from a freshwater canal: effect on the removal of potentially toxic elements and water aggregate stability

TitoloCalcium chloride washing of calcareous sediment from a freshwater canal: effect on the removal of potentially toxic elements and water aggregate stability
Tipo di pubblicazioneArticolo su Rivista peer-reviewed
Anno di Pubblicazione2019
AutoriBuscaroli, E., Sciubba Luigi, Falsone G., Cavani L., Brecchia M., Argese E., Marzadori C., Pourrut B., and Braschi I.
RivistaJournal of Soils and Sediments
Volume19
Paginazione3098-3107
ISSN14390108
Parole chiaveaggregate stability, calcareous soil, canal, heavy metal, inorganic compound, pH, physical property, Salinity, sediment pollution, Toxicity
Abstract

Purpose: Canal dredging and shaping produce considerable amounts of sediments whose reuse on- and off-site depends on their pollution level. This study explores the potential of a calcium chloride washing to remove potentially toxic elements (PTEs) from a freshly dredged calcareous sediment and to affect the aggregate stability of the washed sediment. Materials and methods: The ability of 0.5-M CaCl2 washing to restore the sediment samples polluted with Cu and Zn dredged from a freshwater canal was assessed. The distribution of the two metals among the sediment geochemical phases, the potential availability to plants (DTPA), and the water aggregate stability of particles were evaluated on the washed samples and compared to control. Results and discussion: In the most polluted sample ( 200 and 500 mg kg−1 of Cu and Zn, respectively), the washing decreased the amount of Cu by 26%, mainly in the sulfide/organic fraction, and of Zn by 10%, mainly in carbonates. A decrease in the dispersivity of clay fraction was observed due to the well-known effect of Ca2+ ions on flocculation of colloidal clay particles. At large scale, the aggregates formed by the interaction between large particles and flocculated clay showed lower water stability with respect to the control, thus suggesting the need to improve the physical properties of the treated material. Noteworthy, after 1 year of dry storage from washing, the average percentage of potentially bioavailable (DTPA) Cu and Zn (23 and 13% of pseudo-total amount, respectively) dropped with respect to the control (40 and 19%) and a concomitant carbonate increase (+33%) was observed. Conclusions: The CaCl2 washing is a promising method to reduce Cu and, to a minor extent, Zn in wet calcareous sediments dredged from freshwater canals. However, there is still room for improvement. The PTE fractions remaining in carbonates and organic component of washed sediment clearly indicate the potential of combining mild acidic pH values with calcium chloride in the washing to enhance the PTE removal. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

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URLhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85071716499&doi=10.1007%2fs11368-019-02298-3&partnerID=40&md5=fd4584c32b1965e5ebe9255f53ab71e3
DOI10.1007/s11368-019-02298-3
Citation KeyBuscaroli20193098