Characterization of Environmental Nano- and Macrocolloid Particles Extracted from Selected Soils and Biosolids

Abstract

Environmental nanoparticles found in soil systems and biosolids may pose a considerable risk to groundwater quality as contaminant carriers. Little effort has been invested in the characterization of natural nanocolloids compared to corresponding macrocolloids. This study involved physicochemical, mineralogical, and morphological characterizations of nanocolloids and macrocolloids fractionated from three Kentucky soils and one biosolid. Particle size and morphology were investigated using scanning/transmission electron microscopy and dynamic light scattering. Mineralogical composition was determined by X-ray diffraction and thermogravimetric and Fourier-transform infrared spectroscopy analyses. Zeta potentials and cation exchange capacities assessed surface charge and chemical reactivity. The estimated average hydrodynamic diameter of nanoparticles was nearly twice the ideal 100 nm range, apparently due to irregular particle shapes and partial aggregation. Nanoparticles were also found attached to surfaces of macrocolloids, forming macro-nano aggregates and obscuring some of their physical and chemical characteristics. However, nanocolloids exhibited greater surface reactivity, likely due to their smaller size, poor crystallinity, and morphological shape distortions. In spite of some behavior modification due to nanoaggregation phenomena, nanocolloids appeared to be much more potent vectors of contaminant transport in subsurface environments than their macrosize fractions. Nevertheless, their heterogeneous nature brings to light important considerations in addressing pollution prevention and remediation challenges.

Nanostructures and properties of an Oxisol under no-tillage and mechanical chiseling

“…Another type of nanoparticle/nanostructures formed has darker colors, with no definition of edges and a lumpy shape (Figures 2 and 3). This shape description resembles that in the study of Ghezzi et al (2014), who related it to Fe oxides. In almost all treatments except T6, the hexagonal and lumpy nanoparticles seem interconnected in some places.…”

“…Selvíria, Mato Grosso do Sul, Brazil. The solutions collected during sonication were subsequently centrifuged (model NT 815, NOVATECNICA ®) for 36 min at 4,970 rpm at 20ºC, to separate structures and particles smaller than 200nm (Ghezzi et al, 2014). After centrifugation, 25 mL of the supernatant was removed and filled in a plastic jar at 4°C (Tang et al, 2009).…”

“…In this sense, some studies have investigated the role of iron oxides, aluminum hydroxide and kaolinites in the interaction with organic matter and its stability (Shen, 1999;Pédrot et al, 2011;Keiluweit et al, 2012;Ghezzi et al, 2014;Adhikari & Yang, 2015;Feng et al, 2015). According to Vendrame et al (2011), these minerals are abundant in the composition of Savannah soils, therefore, it is of paramount importance to study the behavior of the nanoparticles of these soils to deepen the understanding of how management practices are affecting these soils.…”

“…The characterization of soil nanoparticles by means of electron microscopy has had promising results, for providing information about the morphology of these nanoparticles, improving the understanding of the mechanisms by which they are linked (Keiluweit et al, 2012;Ghezzi et al, 2014;Archanjo et al, 2017).…”

Trace contaminants in the environmental assessment of organic waste recycling in agriculture: Gaps between methods and knowledge

“…There is also evidence that colloids are present in OW. For example, nano-ZnS is a major Zn species in raw liquid OW (Kim et al, 2014;Le Bars et al, 2018), and organic colloids have been observed in biosolids (Ghezzi et al, 2014).…”