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Non-labile silver species in biosolids remain stable throughout 50 years of weathering and ageing.
Citation:
Donner, E., K. Scheckel, R. Sekine, R. Popelka-Filcoff, J. Bennett, G. Brunetti, R. Naidu, S. McGrath, AND E. Lombi. Non-labile silver species in biosolids remain stable throughout 50 years of weathering and ageing. D.O. Carpenter, and E.Y. Zeng (ed.), ENVIRONMENTAL POLLUTION. Elsevier Science Ltd, New York, NY, 205:78-86, (2015).
Impact/Purpose:
This paper presents an overview of biosolids Ag chemistry in historic and contemporary biosolids sourced from the UK, USA and Australia from the 1950s until today by drawing on a unique collection of archived, stockpiled and contemporary biosolids samples. Characteristics of biosolids Ag chemistry determined in this study included total Ag measurement by neutron activation analysis (NAA); the assessment of Ag lability by 110mAg isotopic dilution (E-values); and Ag speciation by X-ray Absorption Near Edge Spectroscopy (XANES). Two major questions were addressed: 1) whether the speciation and lability of Ag in biosolids from different sources and production eras differs, and 2) whether Ag chemistry in biosolids changes significantly upon weathering and ageing.
Description:
Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that biosolids Ag concentrations have decreased significantly over recent decades. XANES revealed the importance of reduced-sulfur binding environments for Ag speciation in materials ranging from freshly produced sludge to biosolids weathered under ambient environmental conditions for more than 50 years. Isotopic dilution with 110mAg showed that Ag was predominantly non-labile in both fresh and aged biosolids (13.7% mean lability), with E-values ranging from 0.3 to 60 mg/kg and 5 mM CaNO3 extractable Ag from 1.2 to 609 µg/kg (0.002 - 3.4% of the total Ag). This study indicates that at the time of soil application, biosolids Ag will be predominantly Ag-sulfides and characterised by low isotopic lability.
