Abstract
Sediment and soil contamination with toxic heavy metals, including cadmium (Cd2+) and lead (Pb2+), represents a major long-term remediation challenge. Resuspension of contaminated sediments into the water column, or the uptake of toxic metals from top soil, can lead to exposure of aquatic or terrestrial organisms, followed by bioconcentration, bioaccumulation and biomagnification, which may pose a threat to public health. We have developed a novel nanoscale engineered material, namely ligand-coated dense nanoparticles (Ligand DNPs), which contain a dense WO3 nanoparticle core and a shell functionalized with a metal-binding organic ligand (EDTA), to effectively sequester heavy metal ions deeper into the soil and sediments. We demonstrate that one application of Ligand DNPs can remove from 60% to almost 80% of the Cd and Pb in two different soil matrices, driving these metal ions deeper into the sediment or soil column via gravity, and making them less bioavailable. Ligand DNPs can provide a relatively fast, convenient, and efficient in-situ approach for the remediation of sediments and soils contaminated with heavy metals.
Highlights
Heavy metal contamination, such as cadmium (Cd) and lead (Pb), in various environmental media poses a severe threat to ecological and human health as long as they are bioavailable [1,2]
The Fourier transform infrared (FTIR) spectra of Ligand DNPs (S1 Fig in S1 File) indicated that Ligand DNPs presented peaks for C = O, N-H, C-N and C-NH2, which were attributed by the APTES coating layer functionalized by ethylenediaminetetraacetic acid (EDTA)
The stability of Ligand DNPs was evaluated in the soil-water system over a 7-day period
Summary
Heavy metal contamination, such as cadmium (Cd) and lead (Pb), in various environmental media (e.g. soil, sediments, water) poses a severe threat to ecological and human health as long as they are bioavailable [1,2]. There are natural sources of these elements, anthropogenic releases from activities such as metal mining and smelting [3,4,5], coal combustion [6], trace levels in fertilizers [7,8] and even some wastewater sludge and biosolids [9], can increase concentrations to high levels in soils and sediment beds of lakes and rivers These toxic elements can be bioavailable to terrestrial and aquatic organisms [10,11], including crop plants (e.g. rice, wheat) [12,13], and could be further bioaccumulated via the food chain causing damage to humans. These options are not economically feasible, when the contamination is very wide-spread as is the case of many contaminated farmlands and river beds.
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