Oxalate Extraction Research Articles

Ultrasonic-induced crystallization for efficient extraction of hazardous sodium oxalate with ultra-low alkali loss in alumina industry: From laboratory-scale to continuous pilot-scale

Since sodium oxalate (Na2C2O4) in Bayer liquor seriously threatens the sustainable development of the alumina (Al2O3) industry, efficient extraction of Na2C2O4 and reduction of alkali loss have received widespread attention. A new process for extracting Na2C2O4 from mother aluminate liquor by ultrasonic-induced crystallization (UIC) is established at laboratory scale. Due to the controlled sound field and cavitation effect, compared with conventional crystallization (CC) process, the UIC process increases the Na2C2O4 extraction rate from 61 % to 70 %, and reduces the alkali loss rate from 41 % to 19 %. Numerical simulation and sonochemiluminescence confirm that the cavitation effect is mainly concentrated near the axis and at the tip of the titanium alloy horn, and the average life of the cavitation bubble is maintained at 0.9 ms. Density functional theory (DFT) calculations, crystal structure observations and simulations show that the UIC process successfully promotes the development of Na2C2O4 from long strips to lamellar forms, maintaining the safety of Al2O3 production. Additionally, UIC process operates stably on continuous pilot-scale (CPSC) system, with the Na2C2O4 extraction rate and TOC emission rate remaining at around 50 % and 85 % respectively. The UIC method for extracting Na2C2O4 is expected to generate annual profits of $ 267.3 million for China, while also providing support for the innovation and application of ultra-low alkali loss in Al2O3 industry.

Interaction between soy hull polysaccharide and mucin with sodium-/potassium-ion treatment: interfacial property

Abstract The interaction between soy hull polysaccharide and intestinal mucus is influenced by different ions. This study investigates the effects of various concentrations of Na+/K+ on the stability, interfacial activity, and viscoelasticity of the microwave-assisted ammonium oxalate extraction of soy hull polysaccharide (MASP) in simulated intestinal fluids (SIFs) in terms of particle size, zeta potential, surface hydrophobicity, Fourier-transform infrared spectroscopy, shear rheology, and microstructure. Results showed that 1.5 % Na+/K+ causes MASP and mucin in SIFs to bind through physical adsorption; the average particle size of the MASP/SIF miscible system increases from 1,659 to 1,881 and 1,736 nm. When the ion strength is 0.5 %, MASP rapidly reduces the SIF interfacial tension. The addition of Na+/K+ causes a slight redshift in the protein amide I band and an increase in the α-helix content with respect to the decrease in the β-turn and β-sheet corner content. Furthermore, 0.5 % content of Na+ and K+ causes small MASP particles to adsorb onto the surface of mucin, while 1.5 % content of Na+ and K+ causes MASP particles to arrange above mucin after 12 h. These findings provide reference for a deeper understanding of the selection of macroelements (sodium and potassium) in the intake of polysaccharide.

Challenges in geochemical modelling of metal(loid) solubility and binding mechanisms along a soil profile at a multi-contaminated site

Recognising the need for robust models in predicting groundwater contamination risks from metal(loid)s in contaminated topsoil, this study focuses on the geochemical behaviour of As, Cd, Cu, Pb, Sb and Zn in one of Sweden's most heavily contaminated areas. Samples were collected from the waste zone and underlying subsoil down to 5 m and batch experiments were carried out to assess pH-dependent solubility. The results indicate that Cd, Cu, Pb and Zn are efficiently immobilized in the waste zone, while As(V) and Sb(V) are more easily leached. With the exception of Pb and Cu at high pH, the mobilized metals appear to be predominantly in a truly dissolved state, as confirmed by ultrafiltration at 10 kDa.Speciation modelling using Visual MINTEQ did not suggest a significant role of precipitates such as Zn or Pb arsenates and phosphates, although their involvement could not be ruled out. To better understand sorption/desorption patterns, a multi-surface geochemical model was established, drawing on the Stockholm Humic and CD-MUSIC models for organic matter and Fe/Al (hydr)oxide sorption. However, when default parameters were used, the model consistently overestimated the solubility of Cd, Cu, Pb and Zn in both the waste zone and the uncontaminated subsoil. In contrast, As(V) solubility was generally underestimated, also when the reactive surface area of the Fe- and Al (hydr)oxides was decreased in the model. The model's performance was better for Sb(V), though not without imperfections. When the parameters for organic matter were adjusted such that 100% of the solid-phase organic matter was active with respect to ion binding, but only 25% of the dissolved organic matter, the model description improved considerably for Pb and Cu in the upper soil layers. The model revealed distinct differences in the adsorption behaviour of the metal cations, with Pb being sorbed mostly to Fe/Al (hydroxides), whereas a considerable part of Cu was sorbed to organic matter, particularly in the waste zone.Possibly, the dissolution of easily weatherable metal-containing mineral phases may have contributed to the poor model performance for Cd, Zn and for Cu in the deeper soil layers, although other factors, such as a contribution of hydrous SiO2 or Mn oxides to metal binding, could not be ruled out. Metal sorption to carbonate phases may also have been a contributing factor in the waste zone. Lastly, the reactivity of Fe- and Al (hydr)oxides may have been overestimated by oxalate extraction when default parameters for high-surface-area ferrihydrite were applied.These findings provide valuable insights for environmental management and underscore the need for a more detailed characterization of metal(loid) sorption in contaminated soils, as well as the development of improved modelling strategies to enhance solubility predictions.

Antioxidant Active Polysaccharides Extracted with Oxalate from Wild Blackthorn Fruits (Prunus spinosa L.).

Although several therapeutic effects have been attributed to wild blackthorn fruits, their use is still negligible. Purification of the antioxidant-active fraction, obtained from wild blackthorn fruits by hot ammonium oxalate extraction (Ao), yielded seven fractions after successive elution with water, sodium chloride and sodium hydroxide solutions. The purified fractions differ in carbohydrates, proteins, and phenolics. About 60% of the applied Ao material was recovered from the column, with the highest yields eluted with 0.25 M NaCl solution, accounting for up to 70 wt% of all eluted material. Analyses have shown that two dominant fractions (3Fa and 3Fb) contain 72.8-81.1 wt% of galacturonic acids, indicating the prevalence of homogalacturonans (HG) with a low acetyl content and a high degree of esterification. The low content of rhamnose, arabinose and galactose residues in both fractions indicates the presence of RG-I associated with arabinogalactan. In terms of yield, the alkali-eluted fraction was also significant, as a dark brown-coloured material with a yield of ~15 wt% with the highest content of phenolic compounds of all fractions. However, it differs from other fractions in its powdery nature, which indicates a high content of salts that could not be removed by dialysis.

Microscale heterogeneity of phosphorus species associated with secondary mineral phases in the B horizons of two boreal Podzols

Poorly crystalline Al and Fe minerals have high sorption capacities for phosphate anions. However, there is still uncertainty about the molecular-level distribution of phosphorus (P) species between Al and Fe mineral phases, which can be relevant for bioavailability. The present study employed synchrotron X-ray microscopic techniques to distinguish between Al- and Fe-associated P phases in two Podzol B horizons (Flakaliden and Skogaby). First, P species were clustered into major groups depending on the main element association (Al-P, Fe-P, Ca-P + organic P) according to the color of P-containing spots in the tricolor μ-XRF quantitative maps that combined P, Al, and Fe fluorescence intensities. Second, the results were analyzed using quantitative linear combination fitting (LCF) of the P K-edge μ-XANES spectra. Third, in cases when the results diverged, a careful visual comparison between the diagnostic features of the XANES spectra of the samples and the reference standards was made. In 45 of 54 investigated spots, the color method and XANES-LCF produced consistent results. In 2 spots where the results were inconsistent, the diagnostic features of the XANES spectra agreed with the color method but not with XANES-LCF. In 39 of the 47 spots where the major P phase could be identified, Al-P was found to predominate. Ca-P was the major phase in 5 spots, Fe-P in 2, and organic P in 1. Most of the Al-P probably consisted of PO4 adsorbed to imogolite-type materials (ITM), as evidenced by oxalate extraction and Fourier Transform Infrared (FTIR) spectroscopy, although at Skogaby, adsorbed organic P may have played an important additional role. Overall, the P speciation showed substantial spatial heterogeneity, particularly in the upper B horizon of the Skogaby soil and in the lower B horizon of the Flakaliden soil. In conclusion, Al-P, particularly ITM-adsorbed PO4, is the main P phase in the B horizons of the studied Podzols, which may have implications for bioavailability as ITM is more easily dissolved than Fe oxides. Also, the combination of XANES-LCF, colors of the μ-XRF maps, and diagnostic features of the XANES spectra led to robust estimates of the major P phases in soil microsites.

Phosphorus release from rewetted agricultural peat soils varies strongly in dependence of the phosphorus resorption capacity

Rewetting of drained agricultural lowland peat soils is followed by the risk of increased phosphorus (P) release to downstream systems, thereby challenging their restoration as nutrient sinks for years to decades. While extensive knowledge is available on P mobilization under anaerobic conditions caused by reductive (Fe(III))-oxide dissolution, the net P release to the aqueous phase (PSol) is only poorly understood due to unknown significance of P re-sorption to aluminum (Al) oxides and non-reduced Fe(III)-oxides. We therefore hypothesize that PSol is a function of the sorption capacity and P saturation of Al-oxides and non-reduced Fe(III)-oxides. A comprehensive set of 47 Danish topsoil and subsoil samples from agricultural lowlands were incubated for up to 148 days in the laboratory under anoxic and water-saturated conditions at room temperature. Oxalate-extractable Fe, Al and P (Feox, Alox and Pox) varied by three orders of magnitude, with Feox ranging between 1.8 and 1590 mmol kg−1; Alox and Pox also showed high variation with maximum contents of 883 and 153 mmol kg−1, respectively. Bicarbonate-dithionite generally extracted 2 times less Fe, Al and P (FeBD, AlBD, PBD) than oxalate. Oxalate extraction data were used to calculate the degree of P saturation (DPS) and P sorption capacity (PSC). The extent of Fe(III)-oxide reduction measured as 0.1 M HCl extractable Fe(II)HCl was well described by first-order kinetics with rate constants ranging between 0.01 and 0.3 d-1.The estimated maximum Fe(II)HCl produced (Fe(II)max) ranged between 3 and 1490 mmol Fe(II) kg−1, with Feox corresponding to Fe(II)max values very closely. For most soils almost full dissolution of the entire Feox pool was achieved within 21 days of incubation. PSol concentrations, measured in the soil solution extract, ranged between 0.05 and 5.05 mg L-1, increasing with incubation time for most of the soils. While PSol was not correlated with FeBD:PBD and Feox:Pox, DPS, total P (PT) or total Fe (FeT):PT ratio, the investigations revealed a strong reciprocal relationship between the residual sorption capacity (RSC) of the soils, i.e., PSC subtracted the Fe(III)-oxides reduced, and the PSol/Pox ratio. Moreover, the results showed low or lack of P release to the aqueous phase, even for the soil samples where all Feox pools were reduced, if the RSC of the soil was above 100 mmol kg−1. This highlights the importance of redox-stable Al-oxides to capture mobilized P from rewetted lowland peat soils.

Additional phosphorus intensity analysis needed to identify phosphorus requirement on acid sandy soils with high Olsen-P contents

Meeting the crops requirement for phosphorus (P) is crucial to reach the yield potential. Therefore, it is essential to determine soils´ ability to supply the crop with P to identify soils in need of P fertilization and to know where P fertilization is redundant. Thirty-two field experiments with increasing rates of mineral P fertilizers (0, 7.5, 15, 30 and 60 kg P ha−1) to spring barley were carried out from 2020 to 2022 on sandy soils developed on marine or non-marine deposits in Jutland, Denmark. Soil P extraction methods representing both intensity (P extracted with demineralized water, P-water or 0.01 M calcium chloride, P-CaCl2) and quantity tests (P extracted with 0.05 M sodium bicarbonate, Olsen-P) were evaluated by their relationship with relative yields. The examined soils had pH values between 4.6 and 6.7 and total P contents between 305 and 1309 mg P kg−1 soil. Yield increased after P fertilization on twelve soils in Northern Jutland (relative yields < 90 %). Yield responsiveness occurred in all three experimental years despite differences in precipitation and temperatures among the years. Olsen-P contents were not related to yield response, and all responsive soils had moderate or high soil P status according to the Olsen-P test (>20 mg P kg−1 soil). Contents of P-CaCl2 were significantly related to the relative yields (R2 =0.39), and slightly more of the variation in relative yields was explained by the P-CaCl2 to Olsen-P ratio (R2 =0.43). Ten of the twelve response soils were detected with the suggested critical threshold value of 0.02 for the P-CaCl2 to Olsen-P ratio. Soils responsive to P fertilization on older marine (Yoldia) and moraine deposits had higher contents of amorphous aluminium oxides determined by oxalate extraction than the non-responsive soils (+41 mmol mmol kg−1), whereas four lowland soils on younger marine (Litorina) deposits responded to P-fertilization despite low contents of oxalate extractable aluminium. We conclude that an additional P intensity test with CaCl2 extraction offered a much better identification of acid sandy soils requiring P fertilization than relying on the Olsen-P test alone.

Using pXRF and Vis-NIR for characterizing diagnostic horizons of fine-textured podzolic soils in subtropical forests

Proximal soil sensing is a promising tool to quantify soil properties through spectral data and machine learning algorithms for application in pedological investigations. However, the relationship between pedological characteristics and sensor signals is difficult to be elucidated with machine learning models. This study aimed to establish direct linkages between pedological features and data from proximal sensors, namely portable X-ray fluorescence spectrometry (pXRF) and visible and near-infrared spectroscopy (Vis-NIR). Ten podzolic soil profiles, including seven Spodosols, two Ultisols, and one Inceptisol, were described and sampled from Central Taiwan. Principal component analysis (PCA) and k-means clustering method revealed that the major variances of the pXRF were affected by the amounts of spodic materials and organic carbon derived from plant debris. For Vis-NIR, a remarkable absorption of Fe-oxides was observed in the B horizons, and the major variations of Vis-NIR spectra extracted by PCA represented the influence of metal-complexed organic carbon and clay. The principal components (PC) of pXRF and Vis-NIR can be used to separate soil horizons, especially the E horizons were clearly separated as indicated by its high user’s and producer’s accuracies. However, the B and C horizons were poorly separated by the PCs and k-means clustering method. Moreover, the PCs can be used directly to predict the nanocrystalline Fe and Al and the optical density of the oxalate extract. Ten soil profiles were classified based on the predicted values, and nine out of ten soil profiles were in agreement with their classification using chemical extractions. The proposed pXRF and Vis-NIR approaches predicted the chemical criteria of diagnostic horizons and facilitated fast determination of Spodosols.

Structure characterization and calcium ions induced emulsion gel properties of pectic polysaccharide from Fructus aurantii

A novel pectic polysaccharide was extracted from Fructus aurantii using ammonium oxalate extraction, whose primary structure and emulsification properties were investigated for the first time. Fructus aurantii ammonium oxalate-extracted pectin (FAOP) was a highly methyl-esterified pectin with a 60.36% methyl-esterification degree and a relative weight-average molecular weight (Mw) of 1.30 × 106 Da. The backbone of FAOP was composed of a 2:3 molar ratio of →4)-α-GalpA-(1→ and →4)-α-GalpA-6-O-methyl-(1→ linkage, which contained an ∼57.04% linear homogalacturonan (HG) structural domain. In addition, neutral sugar side chains, such as arabinan and galactan belonging to the rhamnogalacturonan I (RG-I) region, were identified. Subsequently, the effects of Ca2+ on the properties of oil-in-water emulsions were investigated by droplet size, zeta potential, rheological properties and emulsion stability. Results indicated that FAOP formed a solid-like gel emulsion and exhibited excellent emulsion stability when the Ca2+ concentration was 5 mM. At this concentration, the droplet size was the smallest, the backscatter signal (BS) was almost unchanged; the Turbiscan stability index (TSI) value was the lowest, and tanδ (G"/G′) was less than 1. These findings indicated that the improved emulsion stability of FAOP by the introduction of Ca2+ was related to the emulsion gel network structure. These results indicated the potential application of Fructus aurantii pectin as a food stabiliser and thickener.

Evaluating wetland soil carbon stability related to iron transformation during redox oscillations

Redox shifts threaten to reduce the massive soil organic carbon (SOC) stocks in wetlands. However, ferrous iron [Fe(II)] oxidation may stabilize wetland SOC by reducing phenol oxidative activity, inhibiting CO2 emissions, and promoting SOC association with ferric Fe [Fe(III)] (oxyhydr)oxides. Yet the prevalence and efficacy of this mechanism are not clear. Here we select six contrasting soils from fens and bogs with different pH for microcosm incubation under cyclic redox conditions, with or without Fe(II) addition, and compared to static oxic incubation. CO2 emissions, microbial composition, enzyme activities, Fe species, and organic matter properties were measured to test the related mechanism. We found that compared to static oxic conditions, the response of Fe(II) to cyclic redox conditions (indicated by the response ratio of −0.48 to 0.53) was positively correlated with that of phenol oxidative activity and cumulative CO2 at the end of the incubation. Redox cycling had little effect on Fe-bound SOC (assessed by the modified citrate-bicarbonate-dithionite extraction), although Fe(II) addition increased Fe-bound SOC in all soils under cyclic redox owing to the production of short-range-ordered Fe(III) (oxyhydr)oxides (quantified by oxalate extraction). Furthermore, Fe(II) addition decreased CO2 emissions from three soils with pH > 6 but increased CO2 emissions from the Sphagnum-dominated soil, which had elevated Fe(II) levels after the incubation. These findings highlight the SOC stabilization potential of Fe(II) addition to wetland soils experiencing redox oscillations by promoting the accumulation of Fe-bound SOC as well as decreasing CO2 emissions (in response to phenol oxidative activity), especially in non-Sphagnum-dominated freshwater wetlands with relatively high pH.

Extraction, characterization, and antioxidant properties of cell wall polysaccharides from the pericarp of Citrus Reticulata cv. Chachiensis

The pericarp of Citrus reticulata cv. Chachiensis (PCRC) had been used as a traditional herbal medicine in southeast and eastern Asia, and it was also an important source of nutraceuticals and functional food ingredients. In the present study, the cell wall polysaccharides were sequentially extracted from PCRC using different solvents, resulting in five pectic fractions and two hemicellulose fractions, namely water-soluble pectin (WSP), hot water-soluble pectin (HWSP), chelator-soluble pectin (CSP), diluted acid-soluble pectin (HSP), sodium carbonate-soluble pectin (NSP), 1 mol/L KOH soluble hemicellulose (KSH-1) and 4 mol/L KOH soluble hemicellulose (KSH-2). The seven fractions were characterized in terms of composition, structure, thermal, rheological, and antioxidant properties. The pectin fractions were classified as high-methoxy pectin with a degree of methyl esterification (DM) between 56.89% and 62.20%. Ammonium oxalate extraction provided the CSP fraction with the highest content of galacturonic acid (75.18%) and the lowest degree of acetylation (0.03). HWSP was considered to be an aggregative of homogalacturonan (HG) and rhamnogalacturonan I (RG-I) containing side chains of galactans and arabinans. Thermal analysis indicated that HWSP had the highest thermal stability than other fractions. All fractions exhibited the characteristics of non-Newtonian fluids, with NSP showing the highest apparent viscosity. Assays for antioxidant activities suggested WSP had the highest DPPH radical scavenging activity while NSP had the highest hydroxyl radical scavenging activity. The result could be a good basis for the applications of cell wall polysaccharides, especially pectin, of PCRC in the preparation of functional food products.

High manganese redox variability and manganate predominance in temperate soil profiles as determined by X-ray absorption spectroscopy

Manganese speciation is a key to understanding the fate of contaminants, nutrients, and organic matter in soils. To date, quantification of Mn species in bulk soils has been performed mainly by sequential extraction methods and rarely supported by spectroscopic analysis. In order to obtain quantitative information on the Mn species inventory of soils, we investigated 46 soil horizons (<2-mm fraction, 45.1–2,280 mg/kg Mn) of nine typical Central European soils (Cambisols, Chernozems, Luvisols, Podzol, Stagnosol) by chemical Mn analyses and Mn K-edge X-ray absorption spectroscopy, and related speciation results to major soil properties. Amounts of Mn2+, Mn3+, and Mn4+ and the average oxidation state of Mn were evaluated by linear combination fitting (LCF) of X-ray absorption near edge structure (XANES) spectra. Additionally, we used extended X-ray absorption fine structure (EXAFS) spectroscopy to identify and quantify major Mn species. For this, EXAFS spectra of 20 organic and mineral soil samples from five soils (Cambisols, Chernozem, Luvisol) were analyzed by LCF and shell fitting. XANES analyses revealed a high Mn redox variability in organic surface layers, with Mn2+ being most abundant (≤100%, x¯ = 54%), followed by Mn3+ (≤80%, x¯ = 32%) and Mn4+ (≤55%, x¯ = 14%). Mineral soil horizons contained significantly less Mn2+ (≤56%, x¯ = 23%), about equal quantities of Mn3+ (≤68%, x¯ = 31%), and were enriched in Mn4+ (≤89%, x¯ = 46%). EXAFS analyses implied the presence of six major Mn species groups: manganates, organically complexed Mn, Mn(III) oxyhydroxides, silicate-bound Mn, Mn oxides without tunnel- or layer structure, and physisorbed Mn. In litter horizons, Mn was mainly present in organic complexes (58–91%, x¯ = 78%) and as physisorbed Mn (≤15%), but individual horizons also comprised manganates, Mn(III) oxyhydroxides, and silicate-bound Mn. Manganates, likely mixtures of phyllomanganates with hexagonal layer symmetry and tectomanganates, dominated in all mineral soil horizons (37–94%, x¯ = 67%). Correlation analysis showed that manganates dissolve completely during dithionite-citrate and acid ammonium oxalate extractions, and suggested that Mn4+-rich manganates preferentially form under less acidic soil conditions, partly by oxidation of organically complexed Mn(II), and that they are enriched in the soil clay fraction. Mineral soil horizons also contained minor quantities of organically complexed Mn (≤39%, x¯ = 11%), silicate-bound Mn (≤30%, x¯ = 8%), Mn(III) oxyhydroxides (≤37%, x¯ = 7%), Mn oxides without tunnel- or layer structure (≤18%, x¯ = 5%), and physisorbed Mn (≤14%, x¯ <1%). The detection of Mn(III) oxyhydroxides such as feitknechtite (β-MnOOH) or groutite (α-MnOOH) as well as the spinel hausmannite (Mn3O4) in acidic soils is remarkable, since their formation is normally linked to neutral or alkaline pH conditions. Minor contributions of silicate-bound Mn indicate the release of Mn from primary minerals already at early stages of soil formation, and low concentrations of physisorbed Mn suggest that exchangeable Mn is rapidly converted into manganates in oxic soils. The predominance of manganates in mineral soils has far-reaching implications for the functioning of soils and biogeochemical element cycles, as these minerals play an important role in metal binding, plant nutrition, and redox-related processes.

Differentiation of fine-textured podzolic soils controlled by climate and landscape in Taiwan

Podzolization is considered to be facilitated by factors such as cool and humid climate, sufficient supply of certain types of organic acids, and coarse-textured parent materials. However, podzolic soils in subalpine areas in Taiwan are characterized by clay content higher than 30%, which differed from that in typical podzolic soils in temperate and boreal regions. This study examined the importance of factors controlling the differentiation of fine-textured podzolic soils in Taiwan. Samples from 31 pedons were examined in this study, and the pedons were grouped into four types, namely Spodosols, Ultisols, Inceptisols, and Inceptisols with placic horizons. Soil colors with 7.5YR 5/6 (the accumulation of spodic materials) and micromorphological observation of oriented clay coatings in the Spodosols confirmed the occurrence of podzolization and clay illuviation, and the selective extraction of Fe and Al confirmed that the Spodosols (Type I) had a higher accumulation of organometallic complexes than the other podzolic soils. A two-step mechanism, namely (1) clay illuviation at an early stage of pedogenesis and (2) podzolization after the canopy vegetation formed, was proposed for the formation of fine-textured Spodosols. Photomicrographs of the Ultisols (Type II) displayed clay hypocoatings masked by spodic materials, and argillic horizons were characterized by a high amount of nanocrystalline iron and high optical density of the oxalate extract. However, the accumulated nanocrystalline iron oxides in the Ultisols were due to the degradation of organic matter under high summer temperatures. Moreover, the leaching of iron in the albic horizons of the Ultisols was attributed to episaturation caused by high clay contents. The Inceptisols (Type III) were transitional soils before forming the Spodosols or the Ultisols, and high clay contents further induced episaturation and formed placic horizons in the Inceptisols (Type IV). Principal component analysis revealed that soil texture and precipitation were the main factors controlling the differentiation of podzolic soils in Taiwan. These factors determined the penetrability and leaching potential of soils, and only the coarse-textured soils with higher leaching potential had the chance of developing Spodosols. However, the developments of Ultisols and Inceptisols with placic horizons were controlled by air temperature and landscape, namely elevation and slope. The bleached E horizons in podzolic Ultisols were attributed to their flat landscape, which favored episaturation and caused the reduction of iron. Low elevation and high temperature in these regions also facilitated the degradation of organic matter and the accumulation of nanominerals.

Exploring alternate methods for predicting sorption-desorption parameters for environmental phosphorus loss assessment in poultry litter impacted soils.

Repeated applications of poultry litter (PL) in weathered soils cause soil phosphorus (P) accumulation and is a major environmental concern. Much remains unknown about the distribution of inorganic P (P i ) and organic P (P o ) forms along with their retention and release characteristics in soils that have had a history of PL application. The objectives of this study were to 1) determine P loss risk by investigating the distribution of P i and P o forms, P sorption-desorption parameters, and soil P saturation ratio (PSR; molar ratio of P/[Al + Fe]); and 2) predict the P sorption-desorption parameters using selected soil variables or soil test indicator, PSR. Forty soil samples from 10 random locations within seven pasture fields located in Piedmont soil region were selected and separated into four depths: 0–5, 5–15, 15–30, and 30–45 cm. These fields received annual PL applications ranging from 26 to 92 kg P ha -1 for the past 10 years. The P forms were determined using sequential P fractionation. Soil P retention characteristics were determined using Langmuir isotherm. Soil PSR was determined using oxalate extract (PSR Ox ). Surface 0–5 cm soils had significantly higher concentrations of labile P i , intermediately available P i , organic P pools, higher equilibrium P concentration (EPC), and PSR Ox compared to the lower depths, which indicated saturation of the P sorption sites from repeated PL application. Regression analyses used to predict P sorption-desorption parameters from soil test variables suggest inclusion of multiple soil variables, which may be time-consuming and not always feasible. The strong relationship between P sorption-desorption parameters and PSR Ox indicates that PSR Ox can be effectively used to predict P sorption-desorption parameters for the Piedmont soils without performing time-consuming batch isotherm experiments. Further studies would be needed to validate the relationship for other soil types under different environmental conditions. • P fractionation in poultry litter impacted soils identified intermediately available P i as the dominant pool in 0–5 cm soils. • Surface soils had lower P sorption capacity and higher desorption potential compared to the soils in lower depths. • P saturation ratio (PSR) was strongly related to P sorption-desorption parameters. • PSR can be effectively used to predict P sorption-desorption parameters for Piedmont soil region.

The endophytic fungus Penicillium oxalicum isolated from Ligusticum chuanxiong Hort possesses DNA damage-protecting potential and increases stress resistance properties in Caenorhabditis elegans.

The chemical composition and antioxidant activity of extracts (POE) of Penicillium oxalate isolated from Ligusticum chuanxiong Hort have been investigated. However, the biological activity of POE is limited, and its antioxidant, stress resistance and DNA protection effects in vivo are unclear. The current study aims to explore the beneficial effects of POE on DNA damage protection in pBR322 plasmid and lymphocytes and stress resistance in Caenorhabditis elegans. The results showed that POE increased the survival rate of C. elegans under 35°C, UV and H2O2 stress, attenuated ROS and MDA accumulation, and enhanced the activity of some important enzymes (SOD, CTA, and GSH-PX). In addition, the POE-mediated stress resistance involved the upregulation of the expression of the sod-3, sod-5, gst-4, ctl-1, ctl-2, daf-16, hsp-16.1, hsp-16.2, and hsf-1 genes and acted dependently on daf-16 and hsf-1 rather than skn-1. Moreover, POE also reduced lipofuscin levels, but did not prolong the lifespan or damage the growth, reproduction and locomotion of C. elegans. Furthermore, POE showed a protective effect against DNA scission in the pBR322 plasmid and lymphocytes. These results suggested that P. oxalate extracts have significant anti-stress and DNA protection potential and could be potential drug candidates in the pharmaceutical field, thus greatly broadening the understanding of the biological effects of the endophytic fungus P. oxalate.

Impact of cell wall non-cellulosic and cellulosic polymers on the mechanical properties of flax fibre bundles

Fibre bundles are groups of elementary fibres glued together thanks to the middle lamella, and are the main fraction in plant fibre composites. In this study, relationship between the mechanical properties of flax fibre bundles, chemical composition and cellulose structure were investigated. To do so, a sequential biopolymer extraction was implemented. Fibre bundles were first depectinated by oxalate extraction, and then the hemicelluloses were extracted by LiCl/dimethyl sulfoxide (DMSO) and KOH. The oxalate extract consisted of homogalacturonans and type I rhamnogalacturonans, while the LiCl extract was composed mainly of glucomannans and the KOH extract of xyloglucans. The KOH stage resulted in the appearance of cellulose II in flax bundles. The extraction of pectin and hemicelluloses led to the disappearance of the middle lamella concomitant with a decrease in the tensile Young's modulus and maximum strength. Finally, the fibre bundle composition, ultrastructure and mechanical properties are discussed together in view of the thin middle lamella.

Organic materials with high P and low C:P ratio improve P availability for lowland rice in highly weathered soils: Pot and incubation experiments

AbstractBackgroundPhosphorus (P) deficiency remains a serious problem for lowland rice cultivation in Sub‐Saharan Africa. Locally available organic materials (OM) are potential amendment resources, but they vary widely in nutrient composition. How different OM affect P availability and rice production under different soil types remains poorly understood.AimsWe aimed to determine soil responses to OM application varying in carbon (C) and P contents on P uptake, rice production, and P availability.MethodsA pot experiment with eight different soils from lowland rice fields amended with four different farmer‐produced OM at an equal dose of 7.5 g kg–1 soil; and an incubation experiment with six soils amended with cellulose and two OM applied at the same C dose were conducted.ResultsAn OM associated with high P and low C:P ratio increased shoot biomass and P uptake of rice in all soils by two‐ and threefold, respectively, compared to the control treatment. Low P saturation in soils (low P:Fe in oxalate extract) produced greater OM effects. Shoot biomass and P uptake decreased significantly in one soil with a high P saturation following application of the other three OM. Although increased soil P solubilization was observed with the addition of fresh C, OM effects on P availability were mostly attributed to their direct P supply.ConclusionOM with high P and low C:P ratio is effective in improving P availability for rice in P‐deficient lowland rice soils.

The Effect of Growing Media on the Vitamin C and Chlorophyll Content of Gelinggang Microgreen

Cassia alata L. (called Gelinggang) was a type of herbal plant used as a skin and diarrhea medicine. However, there has been no further research related to gelinggang microgreens. Therefore, this study utilizes gelinggang as a microgreen. This study aimed to determine the growth media’s effect on chlorophyll and ascorbic acid in gelinggang microgreens. In this study, gelinggang seed was grown in organic soil and rockwool for about 14 days at room temperature (27±1°C). The chlorophyll of acetone extract and ascorbic acid of sodium oxalate extract of this microgreen were determined using UV-Vis spectrophotometric methods. There was a difference between organic soil and rockwool as growing media on the vitamin C and chlorophyll gelinggang microgreen. The study showed that microgreens on organic soil had the highest chlorophyll content, while microgreens on rockwool had the highest vitamin C content. Thus gelinggang microgreens high in phytochemicals compounds could be used as health-promoting food ingredients.

Chemical and mineralogical properties of Guanajibo clay (Plinthic Kandiudults)

A profile of Guanajibo clay (Plinthic Kandiudults) was evaluated to determine the ironstone content in the horizons and its chemical, physical and mineralogical properties. The mineralogy was characterized by X-ray diffraction (XRD) and the iron and aluminum oxide content determined by selective dissolution, using citrate-bicarbonate dithionite (CBD) and ammonium oxalate (OX) extractions. Soil color and the color of ground ironstone were determined with Munsell color charts. Soil texture, pH, and effective cation exchange capacity (ECEC) were also evaluated. The highest content of ironstone per unit mass was found in the Ap horizon (4.6%), decreasing in the Bt (0.9%) and Btv1 (1.0%) horizons. An increase in ironstone content was observed in the Btv2 horizon (3.8%), which suggests that this horizon was formed from alluvial deposits containing ironstone. No ironstone was found in the Btv3 horizon. The texture of the Ap horizon was a sandy clay, and the other horizons had a clay texture. Clay content reached a maximum value of 92.8% in the Btv3. The ECEC was low for the whole profile, ranging from 2.37 cmolc/kg in the Ap horizon to 4.37 cmolc/kg in the Btv3 horizon. The low ECEC is indicative of mineralogy dominated by highly weathered clay minerals like kaolinite and iron and aluminum oxides. The XRD analysis confirmed the presence of kaolinite, goethite, quartz, hematite and gibbsite in the clay fraction (&lt; 2 mm) of the soil. A small peak corresponding to 2:1 clay minerals, probably Al-hydroxy interlayer vermiculite or montmorillonite, was observed in clay samples from the Ap, Bt and Btv1 horizons. The major mineral components of the ironstone were goethite, kaolinite and quartz. The fine earth fraction (150 µm) of the Btv1 horizon had a 2.8% CBD extractable iron content and a ratio of OX/CBD less than 0.10, meeting the two requirements established by Soil Taxonomy to qualify as plinthic. The other horizons met the requirement of OX/CBD ratios of less than 0.10, but had less than 2.5% iron extractable by the CBD method. Soil management practices that prevent soil erosion must be implemented in this soil to ward off exposure of plinthite to the surface and its irreversible hardening to ironstone.

Assessing and predicting phosphorus phytoavailability from sludge incineration ashes

Incineration of municipal sludge and agri-food by-products generates large quantities of ash that can be used in agriculture as phosphorus fertilizer. The fertilizing potential of sludge incineration ash (SIA) from 12 cities in Canada and the United States was tested in a greenhouse experiment against a synthetic fertilizer (TSP: triple superphosphate), a natural fertilizer (RP: rock phosphate), and a control without any P fertilizer. Two soil types were used: clay and sandy loam. A reliable a priori indicator of SIA P bioavailability was determined using the random forest method. SIA application increased ryegrass P uptake. The SIA relative P effectiveness (RPE), compared to the TSP, varied from 5.1% to 46.2% depending on the sludge origin and P solubility. SIA RPE was greater than RP for the clay soil but similar for the sandy loam soil. The neutral ammonium citrate (NAC) extraction, sometimes inappropriately used to characterize P availability of sludge and by-products, explained only 53% of the RPE variation. The random forest analysis showed that the oxalate extraction (Al, P, and Fe) is a better indicator (R2 = 0.94) of relative availability of SIA than the NAC P solubility (R2 = 0.86), and that Al content is the factor that influences most SIA P solubility. Based on our findings, we recommend the use of the Al, Fe, and P oxalate extraction to predict the SIA P availability, instead of the widely used NAC method which extracts only P.