Phosphate regime of sod-podzolic soil in natural and agrophytocenoses

The phosphate regime of sod-podzolic soil (heavy loam) of Cis-Urals under natural phytocenoses (mixed forest, cereal-grass meadow) and agrophytocenoses was studied. The influence of agricultural use of arable land on phosphate regime was evaluated in the long-term stationary experiment (year of establishment – 1978) and the eastern galega (Galega orientalis L.) (year of sowing – 1988). The total content of phosphorus in soil, quantity of its organic, mineral and plant available forms were studied, the fractional composition of mineral phosphates was considered (using Ginzburg-Lebedeva method). The total content of phosphorus in the upper soil layer in all studied objects varied from 1 030 to 1 350 mg/kg. Mineral phosphorus forms prevailed over organic ones in the soil. It was found that the fractional composition of mineral phosphates was 40–62% represented by iron phosphates and 31–48% by calcium phosphates, which is due to the characteristic features of the soil-forming rock – yellow-brown non-carbonate silt drape. Aluminum phosphates amounted to 8–12%. Long-term cultivation of crops during five cycles of the eight-field crop rotation led to a significant decrease in the content of organic phosphorus in the soil. The lower content of iron phosphates (1.6–1.8 times) and the higher content (1.3–2.0 times) of calcium phosphates, available for plants, were observed in the soil of long-term experiment when compared with natural phytocenoses. The content of plant available phosphorus in soil gradually decreased from 239 to 164 mg/kg from the moment of experiment establishment to the fifth rotation. Prolonged fertilizer application (N60P60K60) resulted in the significant increase in mineral and plant available phosphorus forms content in the soil. The residual phosphorus of fertilizers was noted in the Fe-P, Ca-PI and Ca-PII fractions. Under the eastern galega the quantitative and qualitative indicators of the phosphate regime of the soil did not differ significantly from their natural analogues.

XANES Study of Tribofilm Formation With Low Phosphorus Additive Mixtures of Phosphonium Ionic Liquid and Borate Ester

The development of low phosphorus engine oils is important to minimize phosphorus-induced exhaust catalyst poisoning and resulting in harmful emissions. In this study, low phosphorus oil formulations were prepared by using an ashless additive mixture of borate ester (SB) with ionic liquid composed of a phosphonium cation and phosphate anion (P_DEHP) at 350 and 700 ppm phosphorus. Tribological properties of this binary additive system were evaluated using a reciprocating cylinder on a flat test configuration. Favorable interaction between P_DEHP and SB resulted in a significant reduction in friction coefficient and wear volume, in particular for P_DEHP(700P) + SB oil blend. Time-scale analysis of tribofilm formation was determined by running the tribological experiments for 5, 15, and 60 min duration. Electrical contact resistance (ECR) results revealed that the addition of P_DEHP at 350 ppm of phosphorus to SB at 500 ppm of boron can reduce the incubation time from 300 to 100 s for stable tribofilm formation. X-ray absorption near-edge spectroscopy (XANES) analysis of tribofilms indicates that the tribofilm mechanism for additive mixtures of P_DEHP and SB initially involves the formation of boron oxide-based films, which later interact with phosphorus to form boron phosphates in addition to iron phosphates. Incorporation of the high amount of boron phosphates in addition to boron oxide/acid and iron phosphates in the tribofilms contributed to the improved tribological performance of P_DEHP(700P) + SB oil. XANES results reveal that tribofilms formed due to the interaction of SB and P_DEHP evolve to a cross-linked structure, wherein the chain length of polyphosphates is increased with the increase in rubbing time.

Structure, morphology, size and application of iron phosphate

Iron phosphates have rich chemical structures with various morphologies and sizes. Since they are environment friendly with good biocompatibility, they have good performances in the fields of catalysis and battery electrode material rising in recent years, as well as in the traditional fields like agriculture and steel. They also have important applications in adsorption, separation and concentration due to their unique structural characteristics. In this paper, iron phosphates are classified based on their common characteristics such as structure, morphology and size, and their application in the past two decades is reviewed, with emphasis on their application in adsorption, separation and concentration of different species. Further, their application in adsorption, separation and concentration of heavy metals is prospected.

Investigation of Biogenic Passivating Layers on Corroded Iron

This study evaluates mechanisms of biogenic mineral formation induced by bacterial iron reduction for the stabilization of corroded iron. As an example, the Desulfitobacterium hafniense strain TCE1 was employed to treat corroded coupons presenting urban natural atmospheric corrosion, and spectroscopic investigations were performed on the samples’ cross-sections to evaluate the corrosion stratigraphy. The treated samples presented a protective continuous layer of iron phosphates (vivianite Fe2+3(PO4)2·8H2O and barbosalite Fe2+Fe3+2(PO4)2(OH)2), which covered 92% of the surface and was associated with a decrease in the thickness of the original corrosion layer. The results allow us to better understand the conversion of reactive corrosion products into stable biogenic minerals, as well as to identify important criteria for the design of a green alternative treatment for the stabilization of corroded iron.

INFLUENCE OF PRECURSORS ON THE CONTENT OF MINERAL PHOSPHORUS FRACTIONS IN THE SOILS OF RICE FIELDS IN THE ROSTOV REGION.

The article is devoted to the problem of phosphoric nutrition of rice on chestnut soils of the northernmost zone of rice cultivation in Russia. The paper reveals the role of water-soluble fractions of phosphorus, aluminosilicates, iron phosphates and calcium phosphates in the nutrition of rice plants during the growing season. The influence of the previous culture on the content and consumption of these fractions was established.