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Antimony (Sb) is more mobile in lacustrine sediments with seasonal warming. However, the mechanisms of Sb mobility in sediments are still unclear, especially considering the interactions among Sb, iron (Fe), manganese (Mn), and dissolved organic matter (DOM). In this study, high-resolution dialysis (HR-Peeper) and multi-spectral techniques simultaneously investigated changes in Sb, Fe, Mn, and DOM in two different ecological types (algal and grass) sediments with increasing temperature. We found that the dissolved Sb rapidly increased with the increase in temperature. The oxidation of Sb(III) to Sb(V) by Fe/Mn oxides in oxygen (O 2 ) rich overlying water and surface sediment layers was one of the reasons for Sb concentration enhancement in pore water. Further, using excitation-emission matrix and parallel factor analysis (EEM-PARAFAC), synchronous fluorescence (SF) spectroscopy, fourier transform infrared (FTIR) spectroscopy, and two-dimensional correlation spectroscopy (2D-COS) revealed that complexation with DOM was the other reasons for Sb concentration increasing in sediments. This was demonstrated by the similar distribution pattern and significant correlation between Sb and tryptophan-like components. Titration experiments further revealed that Sb was more stably bound to tryptophan-like components in the aromatic C-H (660 cm -1 ), alcoholic C-O (1115 cm -1 ), alkene CC (1615 cm -1 ), and carboxylic acid OH (3390 cm -1 ) groups. The tryptophan-like components from the algae region had a higher binding force than that from the macrophytes region. Our study effectively promotes an understanding of Sb mobilization in lacustrine sediments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Root-triggered microscale variations in O 2 distribution in the rhizosphere of young Phragmites australis are important for nutrient removal in sediments. In this study, the micro-scale O 2 dynamics and the small-scale changes of soluble reactive phosphorus (SRP) and ammonium (NH 4 + ) in the rhizosphere of P. australis were investigated using planar optodes and high-resolution dialysis (HR-Peeper), respectively. Results suggested that root O 2 leakage has a highly variable distribution depending on the stage of root growth, the site of O 2 leakage gradually shift from the entire emerging main roots to the main root tip and subsequently shifted the emerging lateral roots. The O 2 concentration increased in the rhizosphere with increasing light intensity and O 2 levels in the overlying water. Continuous O 2 release from the lateral roots causes the formation of iron plaque on the surface of lateral roots, which reduce the mobility of P by adsorption of iron plaque in the rhizosphere. The oscillation of oxic-anoxic root zones improves nitrogen removal through the processes of anammox, heterotrophic denitrification and nitrification. This work from the micro-scale demonstrates that the O 2 concentration is the spatio-temporal variations in the rhizosphere, and it presents an important role for nutrient removal in sediments., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Lake eutrophication and algal blooms may result in the mortality of macrozoobenthos. However, it is still not clear how macrozoobenthos decomposition affect phosphorus (P) mobility in sediments. High-resolution dialysis (HR-Peeper) and the diffusive gradients in thin films (DGT) technique were used in this study to assess the dissolved organic matter (DOM), dissolved/DGT-labile iron (Fe), P, and sulfur (S(-II)) profiles at a millimeter resolution. The decomposition of Bellamya aeruginosa significantly increased the internal loading of sediments P. The Fe(III) and sulfate were reduced under anaerobic conditions and promoted P desorption from sediments. This was supported by the significant increase in DGT-labile S(-II) and dissolved/DGT-labile P, Fe(II) and the significant positive correlation between Fe and P on day 8. The simultaneous increase in DOM and soluble reactive phosphorus (SRP) and the significant positive relationship between these factors were observed during the decomposition of B. aeruginosa. This suggested that complexation of DOM with metals may promotes the release of P from sediments., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Applications of aluminium (Al) salt or lanthanum (La) modified bentonite (LMB) have become popular methodologies for immobilizing phosphorus (P) in eutrophic lakes. The presence of humic substances, has been shown to inhibit this form of treatment due to the complexation with La/Al. However, the effects of other dissolved organic matter (DOM), especially that derived from phytoplankton (the dominant source in eutrophic lakes) are unknown. In this study, the interaction with La/Al of Suwannee River Standard Humic Acid Standard II (SRHA) and algae-derived DOM (ADOM) were investigated and compared. Differed to SRHA which was dominated by polyphenol-like component (76.8%, C1-SRHA), majority in ADOM were protein-like substance, including 41.9% tryptophan-like component (C2-ADOM) and 21.0% tyrosine-like component (C3-ADOM). Two reactions of complexation and coprecipitation were observed between SRHA/ADOM and La/Al. Complexation dominated at low metal inputs less than 10 μM and coprecipitation was the main reaction at higher metal inputs. For ADOM, the tryptophan-like component (C2-ADOM) was the important component to react with metal. The reaction rate for C2-ADOM with La were about two-third of that for C1-SRHA, indicating that the influence of C2-ADOM was significant during the P immobilization by La/Al-based treatment in eutrophic lakes. The P removal data in the presence of ADOM confirmed the significant inhibition of ADOM. In addition, based on the composition of coprecipitates and relatively biodegradable character of tryptophan-like substances (C2-ADOM), the coprecipitation of ADOM was assumed to reduce the stability of precipitated P in eutrophic lakes. The release of P from the potential biodegradation of the coprecipitates and thus the possible decline of the performance of P immobilization by La/Al-based treatments is an important work in the future., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Iron (Fe) and manganese (Mn) reactions have been regarded as the primary factors responsible for the mobilization of phosphorus (P) in lake sediments, although their individual roles are hard to distinguish. In this study, in situ mobilization of P, Fe and Mn in sediments was assessed by high resolution spatio-temporal sampling of their labile forms using diffusive gradient in thin films (DGT) and suction device (Rhizon) techniques. It was found that the monthly concentration distributions showed greater agreement and better correlation coefficients between labile P and labile Fe, than those between labile P and labile Mn, implying that Fe plays a key role in controlling P release in sediments. Furthermore, better correlations were observed between hourly changes in concentrations of soluble reactive phosphorus (SRP) and soluble Fe(II), than those between SRP and soluble Mn. Changes were observed under simulated anaerobic incubation conditions, suggesting that P release was caused by the reductive dissolution of Fe oxides. This was supported by the lack of influences on P release from reductive dissolution of Mn oxides in the sediment-water interface and top sediment layers under the anaerobic incubations. In simulated algal bloom experiments, positive correlations and consistent changes were observed between SRP and soluble Fe(II) concentrations, but not between SRP and soluble Mn concentrations. This further demonstrated the Fe-dependent and Mn-independent release of P in sediments. Therefore, Fe redox reactions have a high impact on P mobilization in sediments, while Mn redox reactions appear to have negligible influences., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study assessed the effectiveness of dredging in controlling arsenic (As), selenium (Se), and antimony (Sb) contamination in sediments, by examining contaminant concentrations in sediments six years after dredging was completed. High-resolution diffusive gradients in thin films (DGT) and dialysis (HR-Peeper) techniques were used to monitor the concentrations of DGT-labile metalloids and soluble metalloids in sediments, respectively. Results revealed that dredging effectively remediated metalloid contamination in sediments only in April, July and/or January. Compared to non-dredged sediments, the concentrations of soluble and DGT-labile As, Se, and Sb in dredged sediments decreased on average by 42%, 52%, and 43% (soluble), and 54%, 50%, and 53% (DGT), respectively. The effectiveness of the dredging was primarily due to the transformation of metalloids from labile to inert fractions, which increased the ability of the sediments to retain the metalloids, and the slowed rate of resupplied metalloids from available solid pools. In contrast, negligible/negative effects of dredging were seen in October, and the concentrations of soluble and DGT-labile metalloids even increased in some profiles of dredged sediments. This was mainly caused by a release of the metalloids from algal degradation, which may offset the dredging effectiveness., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study investigated the effects of tubificid worm bioturbation on the lability of phosphorus (P) in microcosm sediments. High-resolution dialysis (HR-Peeper) and two types of diffusive gradients in thin films (DGT) (Zr-oxide DGT and ZrO-Chelex DGT) were used to measure soluble P and Fe, and labile P and Fe at a millimeter spatial scale. The worm bioturbation promoted P release (up to 511% of the control) to the overlying water on the 6th day, but it was reduced compared to the control (up to 171% of the control) from the 22nd day to the 102nd day because of the adsorption by Fe(III) oxyhydroxides. The worm bioturbation reduced the pore water soluble P concentration up to 48% and the DGT-labile P concentration up to 29% of the control from a sediment depth of -10 mm to approximately -130 mm before the 22nd day of incubation due to worm ingestion of sediment particles. Two-dimensional measurements of DGT-labile P also showed a much lower concentration of labile P around the worm burrow. This effect disappeared on the 53rd and 102nd day. However, the soluble P and DGT-labile P decreased again up to 41% and 38%, compared to the control from the sediment depth of -20 mm and -10 mm to approximately -130 mm, respectively, on the 152nd day of incubation due to the adsorption by Fe(III) oxyhydroxides. Soluble Fe(II) and DGT-labile Fe did not show significant changes from the worm bioturbation on the 6th day, but decreased up to 31% and 47% of the control after the 6th day. The results that worm ingestion of sediment particles is a significant driver of soluble and labile P reduction in the sediments before the 22nd day. After that, soluble and labile P reduction was attributed to P adsorption by Fe(III) oxyhydroxides., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The effects of chironomid larvae bioturbation on the lability of phosphorus (P) in sediments were investigated through sediment incubation for 140 days. High-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) techniques were applied to obtain soluble and labile P/Fe profiles at a millimeter resolution, respectively. The larvae bioturbation decreased concentrations of soluble/labile P and Fe by up to over half of the control at the sediment depths of influence up to 70 and 90 mm respectively. These effects continued over 116 days and disappeared on the 140th days due to eclosion of chironomid larvae. Labile P was highly correlated with labile Fe, while a weak correlation was observed between soluble P and soluble Fe. It was concluded that Fe(II) oxidation and its enhanced adsorption were the major mechanisms responsible for the decreases of soluble and labile P., (Copyright © 2015 Elsevier Ltd. All rights reserved.)