Mineral Nanoparticles in Waste: Potential Sources, Occurrence in Some Engineered Nanomaterials Leachates, Municipal Sewage Sludges and Municipal Landfill Sludges

Abstract

Environmental assessment of engineered nanoparticles (ENPs) currently suffers from lack of data on production, emission, behaviour and fate in natural compartments. This paper aims to bring factual data on production amounts of ENPs and emission of mineral elements in a colloidal or nanoparticulate forms stemming from products, (e.g. cosmetics, paints, concretes) and from two potential waste sinks, namely municipal sewage sludge and nonhazardous waste landfill sludge. Based on the declaration of production and importation of ENPs in France in 2014, we set out a classification of ENPs substances comprising carbon black, organic pigments, miscellaneous organic substances and mineral ENPs. These mineral ENPs were sub-classified on the basis of production and CLP ecotoxicological and hazard classifications. Major elements (Group #1) encompass ENPs substances ubiquitous in total contents, and also as a colloid fraction in waste leachates (Si, Ca, Ti, Al, Mg, Fe, Mn, P). Minor elements were divided as ENPs with soluble substances and dissolved metal ions non-classified as ecotoxic (Group #2: Ba, Bi, Cr (III), Sr, Zr, La, Pd, Mo, W, Y, Au) or with soluble substances classified as ecotoxic and hazard statement code in the CLP regulation (Group #3: Ce, Cu, Zn, Ni, Sb, Ag, Co). Paints, concrete and particularly cosmetics proved to be sources of ENPs. Colloidal forms of elements or ENPs were found in leachate obtained from paint (Si), in cosmetics leachates (Al, Si, Ti and Zn), and in one demolition concrete (Ti). No nanoparticulate forms or fraction of Ag, Ce, Ti and Zn were identified by TEM/EDS in municipal sewage sludge. However, sewage sludge could be a sink for Group #3 elements such as Ag and Ce, since their total concentrations were significant. Based on landfill leachates from municipal solid wastes, the colloidal fraction frequently contained elements of Group #3 (Ni, Zn, Cu, Co and Sb) but with low mean concentration and more rarely Ag and Ce, indicating that the fluxes of these elements from the landfill cells should be low, except for Ce. Landfills seem to not emit ENPs in their leachates. From a regulative aspect, monitoring of Ag in sewage sludge for agricultural use could be of concern.