1 research outputs found
Environmental Risk Implications of Metals in Sludges from Waste Water Treatment Plants: The Discovery of Vast Stores of Metal-Containing Nanoparticles
Nanoparticle
(NP) assessment in sludge materials, although of growing
importance in eco- and biotoxicity studies, is commonly overlooked
and, at best, understudied. In the present study, sewage sludge samples
from across the mega-city of Shanghai, China were investigated for
the first time using a sequential extraction method coupled with single
particle inductively coupled plasma mass spectrometry (SP-ICP-MS)
to quantify the abundance of metal-containing NPs in the extraction
fractions and transmission electron microscopy to specifically identify
the nanophases present. In general, most sludges observed showed high
concentrations of Cr, Cu, Cd, Ni, Zn, and Pb, exceeding the maximum
permitted values in the national application standard of acid soil
in China. NPs in these sludges contribute little to the volume and
mass but account for about half of the total particle number. Based
on electron microscopy techniques, various NPs were further identified,
including Ti-, Fe-, Zn-, Sn-, and Pb-containing NPs. All NPs, ignored
by traditional metal risk evaluation methods, were observed at a concentration
of 10<sup>7</sup> −10<sup>11</sup> particles/g within the bioavailable
fraction of metals. These results indicate the underestimate or misestimation
in evaluating the environmental risks of metals based on traditional
sequential extraction methods. A new approach for the environmental
risk assessment of metals, including NPs, is urgently needed