Influence of Organic Matter on the Transport of Mineral Colloids in the River-Sea Transition Zone

The River-Sea Transition Zone has a significant impact on marine ecosystems, especially at present, due to increased anthropogenic pressure on rivers. The colloidal form of river runoff has not been practically studied, unlike the dissolved and suspended one, but this form is particularly important for the transport of river substances. The mechanisms of substance transfer were studied using model systems (colloidal clay, Fe(OH)3 sol), particle aggregation was estimated by changes in optical density, turbidity and particle size. The influence of the nature of dissolved organic matter (DOM) and salinity on colloid transport was studied. It was found that humic substances (HS) (recalcitrant DOM) stabilize mineral colloids with increasing salinity, while their interaction with chitosan (labile DOM) promotes flocculation and further precipitation in the mixing zone. In natural conditions, labile DOM can be released during viral lysis of bacteria or salt stress of biota. It was shown that clay particles modified with HS are flocculated more effectively than pure clays. HS can facilitate the transport of Fe(OH)3 into the outer part of the mixing zone even in the presence of flocculants. The flocculation mechanism and modern views on this process are considered

Foliar Application of Humic-Stabilized Nanoferrihydrite Resulted in an Increase in the Content of Iron in Wheat Leaves

The objective of this study was to synthesize iron (hydr)oxide nanoparticles (IONPs) stabilized by humic substances, and to estimate the feasibility of their use for foliar application on iron deficient plants. The IONPs were synthesized by rapid hydrolysis of iron(III) nitrate in a solution of potassium humate. The iron speciation and nanoparticle morphologies were characterized using X-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy. The obtained sample of IONPs was applied at concentrations of 1- and 10-mM Fe, and 0.2% urea was used as an adjuvant. Wheat plants (Triticum aestivum L. cv. L15) were used for the iron uptake test. For both of the concentrations tested, spraying the nanoparticles resulted in a 70–75% higher iron content in wheat leaves compared to ferric ammonium salt of ethylenediaminetetraacetic acid (Fe-EDTA). The synergistic effect of humic substances acting as a surfactant seemed to promote an increase in the iron uptake of the ferrihydrite nanoparticles compared to the aqueous Fe-EDTA solution used in this study. We concluded that humic-stabilized IONPs are much better suited to foliar application as compared to soil amendment when applied as a source of iron for plants. This is because humic substances act as a capping agent for nanoparticles and the surfactants enhance iron penetration into the leaf

Foliar Application of Humic-Stabilized Nanoferrihydrite Resulted in an Increase in the Content of Iron in Wheat Leaves

The objective of this study was to synthesize iron (hydr)oxide nanoparticles (IONPs) stabilized by humic substances, and to estimate the feasibility of their use for foliar application on iron deficient plants. The IONPs were synthesized by rapid hydrolysis of iron(III) nitrate in a solution of potassium humate. The iron speciation and nanoparticle morphologies were characterized using X-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy. The obtained sample of IONPs was applied at concentrations of 1- and 10-mM Fe, and 0.2% urea was used as an adjuvant. Wheat plants (Triticum aestivum L. cv. L15) were used for the iron uptake test. For both of the concentrations tested, spraying the nanoparticles resulted in a 70–75% higher iron content in wheat leaves compared to ferric ammonium salt of ethylenediaminetetraacetic acid (Fe-EDTA). The synergistic effect of humic substances acting as a surfactant seemed to promote an increase in the iron uptake of the ferrihydrite nanoparticles compared to the aqueous Fe-EDTA solution used in this study. We concluded that humic-stabilized IONPs are much better suited to foliar application as compared to soil amendment when applied as a source of iron for plants. This is because humic substances act as a capping agent for nanoparticles and the surfactants enhance iron penetration into the leaf