Capturing the colloidal microplastics with plant-based nanocellulose networks

Microplastics accumulate to various aquatic organisms causing serious health issues, and they have raised concerns about human health by entering our food chain. The recovery techniques for the most challenging colloidal fraction even for the analytical purposes are limited. Here we show how hygroscopic nanocellulose network acts as an ideal capturing material even for the tiniest nanoplastic particles. We reveal that the entrapment of particles from the aqueous environment is a result of the network’s hygroscopic nature - a feature which is further intensified with the high surface area. We determine the nanoplastic binding mechanisms using surface sensitive methods, and interpret the results with the random sequential adsorption (RSA) model. The microplastic uptake does not rely on any specific interfacial interaction but rather on the water transport behavior of nanocellulose. These findings hold potential for the explicit quantification of the microplastics from different environments, and eventually, provide solutions to collect those directly on-site where they are produced.

Swelling properties of clays, a major risk factor for the infrastructure projects

Swelling and shrinking properties refers to significant positive or negative variations of volumes due to absorbtion or dessication of water in fine soils under natural or anthropic regime of moisture. These physical phenomena are worldwide spread and had important engineering consequences with associates cost of damages of several billion annually in all climate areas. In spite of the fact that these geotechnical properties are studied for more than eight decades, the particularities of these peculiar relations between water, mineral composition and geomechanical behavior are still unrevealed entirely. In Romania, swell/shrink soils are reported in all regions at different depths, but rarely related to geotechnical engineering accidents such as slope slides or road failures. This work presents some obvious relations between the hydrogeological structure, the presence of “large swell/shrink soils”, their mineralogical composition and geomechanical properties and the ubiquitous landslides on Peri Carpathians Hills. Large infrastructure projects offer the opportunities to put into evidence the swelling properties of Upper Pliocene-Lower Pleistocene deposits, which supports the Holocene alluvial deposits of Argeş River. Analyzed samples allow us to define some basic correlations between plasticity index, colloidal fraction, dry density, swelling pressures or free swelling and mineralogical composition.

The Release of Incidental Nanoparticles During the Weathering of Gunshot Residue in Soils of a Shooting Range in Ontario, Canada

Gunshot residue is emitted as fine particulate matter upon the ignition of percussion-sensitive explosives among other additives in a firearm barrel. The particulates condense from a vapor phase and contain material from the Pb-Sb-Ba-bearing primer, S-bearing gunpowder, and the Pb-bearing bullet fragments. Shooters can inhale or ingest the fine particulates which also attach to their hands, clothing, and other surfaces. Estimation of the bioavailability of the emitted toxic Pb- and Sb-bearing particulates requires detailed knowledge of their mineralogical composition and those of their weathering products. For this purpose, gunshot residue particulates have been collected from soils in front of a firing line of a shooting range in Ontario, Canada. Bulk mineralogical and chemical features of the soils have been characterized using X-ray powder diffraction, inductively coupled plasma-mass spectrometry, and scanning electron microscopy. The focused ion-beam technique has been used to extract a section containing numerous altered gunshot residue particulates from a soil grain. Subsequent transmission electron microscopy shows for the first time that gunshot residue particulates are composed of metallic δ-Pb, α-Sb, galena (PbS), and an unidentified Ba-bearing phase. Weathering of the gunshot residue particulates results in the formation of incidental nanoparticles (i.e., not purposely engineered to occur at the nanometer scale) in the form of δ-Pb, massicot, PbO, and galena. The formation and mobilization of some of these nanoparticles within the soil grain suggest that their release during the weathering of bullets and gunshot residue contributes to the release of Pb into the environment. Hydrocerussite, Pb3(CO3)2(OH)2, cerussite, PbCO3, and massicot and anglesite, PbSO4, are the major secondary Pb-phases in and around altered GSR particulates. These phases form during the weathering of metallic Pb, massicot, and galena nanoparticles in a Ca-carbonate rich environment. Secondary Sb-bearing phases are valentinite, Sb2O3, and amorphous Sb-Pb phases (Sb:Pb ratio = 2:1–4:1). The latter phases have partially replaced large proportions of the Ca-carbonates surrounding the gunshot residue particulates. The larger abundance of the amorphous Sb-Pb phases relative to valentinite suggests that their solubility most likely controls the release of Sb into the bulk soil. The SEM and TEM characterizations and chemical analyses of mineral surface coatings and the colloidal fraction of a leachate from the collected surficial soils indicate that Pb occurs predominantly in the colloidal fraction, is often associated with sulfate-bearing colloids, and is sequestered in sulfate and carbonate/hydroxide coatings.

Specification of the density of the mudflow mixture taking into account the clay-colloidal fraction

As a result of laboratory research, was obtained a formula for calculating the density of the mudflow mixture, taking into account the clay-colloidal fraction. The conditions for the formation of mudflows with different particle size distribution are determined. It was found that the formation and decay of the mudflow largely depend on certain ratios between the clay-colloid and rocky components of the mudflow, and not on the density of the mudflows and the percentage (weight) of water, as was presented in early scientific works. It is advisable to use the empirical formula, obtained in the work, to accurately calculate the density of mudflow mixtures for the prediction of mudflow phenomena in order to conduct effective and environmentally sound antimudflow measures.

Assessing the role of colloidal phosphorus delivery processes in groundwater-fed agricultural catchments

<p>Soil colloids with high sorbing capacities can enhance transport of phosphorus (P) from soils to groundwater and the delivery of P to surface water via groundwater pathways. However, only particulate and dissolved P fractions are generally monitored at the catchment scale.</p><p>To add important insights into the particulate to dissolved P concentration spectrum in the soil-water environment, the role of colloidal P delivery processes to surface water was studied in two agricultural catchments. The catchments were dominated by belowground pathways but had contrasting land use (arable and grassland). Particulate, coarse colloidal (0.20 – 0.45 μm) and finer colloidal (< 0.20 μm) P fractions were monitored along hillslopes in the free soil solution, shallow groundwater and stream water on a weekly basis for background characterisation and at higher frequency during rainfall events. An automated sampler was deployed in the stream and an automated, low-flow and low-disturbance sampler was developed to sample groundwater. Multi-parameter probes were also deployed to monitor stream water and shallow groundwater physico-chemical parameters. Stream discharge was measured at high frequency using a flow velocimeter in order to quantify P loads, apportion hydrological pathways and study concentration-discharge hysteresis.</p><p>Preliminary findings showed higher background P and unreactive P concentrations in the stream and groundwater in the grassland catchment. In the arable catchment (rainfall event in June 2019) P was mainly lost through deeper baseflow (92% of the total event flow) as reactive P in the finer colloidal fraction (0.070 mg P/ha) and only a small fraction lost as particulate unreactive P (0.008 mg P/ha). In the grassland catchment (rainfall event in October 2019), P was mainly lost through quickflow (37% of the total flow) even tough deeper baseflow was also important (33%). Losses were mainly reactive P in the finer colloidal fraction (13.6 mg P/ha) but also as unreactive P (4.5 mg P/ha). Concentration-discharge hysteresis suggested a smaller and easily mobilised P source in the arable catchment and a larger P source, followed by the mobilisation of a second but smaller source via a second hydrological surface pathway in the grassland catchment.</p><p>Further monitoring campaigns during more rainfall events in the grassland catchment are required to better understand colloidal P delivery and the spatial/temporal dynamics between rainfall events in relation to soil conditions and rainfall patterns. This will help to better target mitigations measures according to P species and fractions, hydrological flowpaths, and rainfall patterns – important in the context of a changing climate.</p>

The influence of diatomite rock on humus substances of sod-podsolic soil in conditions of agro ecosystems and physical-chemical mechanism of their interaction

The paper provides an assessment of physical and chemical changes of humus substances in the sludge-colloidal fraction, isolated from the sod-podsolic sandy loamy soil, during its interaction with the diatomite rock of the Inzen deposit in conditions of agro ecosystem of the Nizhny Novgorod Region. The experience was a 3-year (2015-2017) microfield experiment, laid down on one of the fields of Elitkhoz. The diatomite was added to soil once during the summer season of 2014 in doses of 3, 6 and 12 t/ha, on which winter wheat, barley and peas were subsequently grown (varieties are zoned in the Volga-Viatskiy Region). Each year, upon completion of crop cultivation, a silo-colloidal fraction was isolated from selected soil samples by the Kachinsky gravimetric method and analyzed on an IR-Fourier-spectrometer, determining absorption spectra in frequency range of 4000-400 cm-. In soil samples the content of specific organic substance (humus) was also determined by the Thurin method with spectrophotometric termination. The studies revealed that interaction of diatomite with the organic soil matrix resulted in organosilanes RnSiH4-n (930 cm-), organosilanes oxygen-free Si-CH3 (1253 cm-) and oxygen-containing compounds Si-O-CH3 (1110 cm-), as well as siloxane bonds of Si-O-Si (570 cm-). The obtained facts directly indicate formation of silicon-containing organo-mineral complexes in sludge-colloidal fraction and participation of silicon in their formation. It is evident that an active diatomite represented by various silicon acids (HnSiOm) was involved in formation of these bonds. The use of diatomite has helped to maintain content of humus substances in soil at the control level, which can also confirm effects of interaction of silicon substances with organic part and, as a result, prevent its degradation. Based on the obtained results and analysis of scientific literature, a mechanism is proposed for possible physical-chemical interaction of active silicon substances with an organic component of the sludge-colloidal fraction of the sod-podsolic soil, which consists in polymerization of silicon on organo-mineral complexes (bonds -Si-O-Si-), as well as in interaction of the hydrolyzed part of humus substances with silicon with subsequent formation of organosilanes, which are subsequently connected with an organic Si-O-CH3 matrix. Due to the fact that organic matter of soils is involved in the formation of ecological stability of soil cover the established effects make it possible to speak about the increase of agro ecological stability of humus substances in sod-podsolic soil due to the use of diatomite rocks.

Reducing the Bitter Taste of Virgin Olive Oil Don Carlo by Microbial and Vegetable Enzymes Linked to the Colloidal Fraction

Bitter taste is a positive sensory attribute that correlates with the concentration of phenols in olive oil. However, excessive bitterness can be perceived by consumers as a negative attribute. The aim of this investigation was to improve the process of debittering Don Carlo extra virgin olive oil (EVOO), which is rich in phenols, through blending with newly produced Leccino EVOOs, which can provide high oleuropeinolytic activity. The debittering process of blending Don Carlo EVOO with two types of Leccino EVOOs (decanter and settled EVOO), was carried out during three months of storage in canisters placed in fixed positions, or periodically inverted to prevent sedimentation. The reduction in phenolic concentration and bitterness index (K225 value) reached maximum values of 51% and 42% respectively in Don Carlo EVOO mixed with Leccino settled EVOO after three months of storage in periodically inverted containers. Analytical indices and sensory analysis, in accord with bitterness index (K225) results, confirmed a reduction or elimination of bitter taste in the oil samples depending on the type of Leccino EVOO added, and the sample storage method. All analytical results remained within parameters established by the European Community regulations for commercial merceological class EVOO.

Characterization of the Natural Colloidal TiO2 Background in Soil

An increasing amount of TiO2 engineered nanoparticles (TNP) is released into soils and sediments, increasing the need for dedicated detection methods. Titanium is naturally present in soils at concentrations typically much higher than the estimated concentrations for TNP. Therefore, a precise knowledge of this natural background, including the colloidal fraction, is required for developing adapted strategies for detecting TNP. In this study, we characterized the natural colloidal Ti-background by analyzing eight soils with different properties and origins. A combination of X-ray fluorescence analysis and ICP-OES was used for determining the silicate bound fraction, which was a minor fraction for all soils (0–32%). The colloidal fraction obtained by extracting colloids from soil prior to ICP-OES measurements ranged between 0.3% and 7%. Electron microscopy and hydrodynamic chromatography confirmed that Ti in the form of colloids or larger particles was mostly present as TiO2 minerals with a fraction smaller than 100 nm. The size distribution mode of the extracted colloids determined using hydrodynamic chromatography ranged between 80 and 120 nm. The chromatograms suggested a broad size distribution with a significant portion below 100 nm. In addition to these data, we also discuss possible implications of our findings for the method development for detecting TNP in soils.