Investigating the fate of persistent organic pollutants in water distribution systems (WDSs) is of great significance for preventing human health risks. The role of iron corrosion scales in the migration and transformation of organics in such systems remains unclear. Herein, we determined that hydroxyl (•OH), chlorine, and chlorine oxide radicals are generated by Fenton-like reactions due to the coexistence of oxygen vacancy-related Fe(II) on goethite (a major constituent of iron corrosion scales) and hypochlorous acid (HClO, the main reactive chlorine species of residual chlorine at pH ∼ 7.0). •OH contributed mostly to the decomposition of atrazine (ATZ, model compound) more than other radicals, producing a series of relatively low-toxicity small molecular intermediates. A simplified kinetic model consisting of mass transfer of ATZ and HClO, •OH generation, and ATZ oxidation by •OH on the goethite surface was developed to simulate iron corrosion scale-triggered residual chlorine oxidation of organic compounds in a WDS. The model was validated by comparing the fitting results to the experimental data. Moreover, the model was comprehensively applicable to cases in which various inorganic ions (Ca2+, Na+, HCO3-, and SO42-) and natural organic matter were present. With further optimization, the model may be employed to predict the migration and accumulation of persistent organic pollutants under real environmental conditions in the WDSs.

In this study, a facile approach for simultaneous determination of dopamine (DA) and tryptophan (TRP) using a 3D goethite-spongin-modified carbon paste electrode is reported. The prepared electrode exhibited excellent electrochemical catalytic activity towards DA and TRP oxidation. The electrochemical sensing of the modified electrode was investigated using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Through differential pulse voltammetry analysis, two well-separated oxidation peaks were observed at 28 and 77 mV, corresponding to the oxidation of DA and TRP at the working electrode, with a large peak separation of up to 490 mV. DA and TRP were determined both individually and simultaneously in their dualistic mixture. As a result, the anodic peak currents and the concentrations of DA and TRP were found to exhibit linearity within the ranges of 4-246 μM for DA and 2 to 150 μM for TRP. The detection limits (S/N = 3) as low as 1.9 μM and 0.37 μM were achieved for DA and TRP, respectively. The proposed sensor was successfully applied to the simultaneous determination of DA and TRP in human urine samples with satisfactory recoveries (101% to 116%).

Rice is one of the most important staple food crops; however, it is prone to cadmium (Cd) accumulation, which has negative health effects. Therefore, methods to reduce Cd uptake by rice are necessary. At present, there is limited research on the effects of co-application of silicon (Si) and goethite in mitigating Cd stress in rice. Furthermore, the specific mechanisms underlying the effects of their combined application on iron plaque formation in rice roots remain unclear. Therefore, this study analyzed the effects of the combined application of Si and goethite on the biomass, physiological stress indicators, Cd concentration, and iron plaques of rice using hydroponic experiments. The results revealed that co-treatment with both Si and goethite increased the plant height and dry weight, superoxide dismutase and catalase activities, photosynthetic pigment concentration, and root activity. Moreover, this treatment decreased the malondialdehyde concentration, repaired epidermal cells, reduced the Cd concentration in the roots by 57.2 %, and increased the number of iron plaques and Cd concentration by 150.9 % and 266.2 % in the amorphous and crystalline fractions, respectively. The Cd/Fe ratio in amorphous iron plaques also increased. Our findings suggest that goethite serves as a raw material for iron plaque formation, while Si enhances the oxidation capacity of rice roots. The application of a combination of Si and goethite increases the quantity and quality of iron plaques, enhancing its Cd fixation capacity. This study provides theoretical evidence for the effective inhibition of Cd uptake by iron plaques in rice, providing insights into methods for the remediation of Cd contamination.

In urbanized areas, extracellular DNA (exDNA) is suspected of carrying genes with undesirable traits like virulence genes (VGs) or antibiotic resistance genes (ARGs), which can spread through horizontal gene transfer (HGT). Hence, it is crucial to develop novel approaches for the mitigation of exDNA in the environment. Our research explores the role of goethite, a common iron mineral with high adsorption capabilities, in exDNA adsorption processes. We compare well-crystalline, semi-crystalline, and nano goethites with varying particle sizes to achieve various specific surface areas (SSAs) (18.7-161.6 m2/g) and porosities. We conducted batch adsorption experiments using DNA molecules of varying chain lengths (DNA sizes: <11 Kb, <6 Kb, and <3 Kb) and assessed the impact of Ca2+ and biomacromolecules on the adsorption efficacy and mechanisms. Results show that porosity and pore structure significantly influence DNA adsorption capacity. Goethite with well-developed meso- and macroporosity demonstrated enhanced DNA adsorption. The accumulation of DNA on the goethite interface led to substantial aggregation in the system, thus the formation of DNA-goethite conjugates, indicating the bridging between mineral particles. DNA chain length, the presence of Ca2+, and the biomacromolecule matrix also affected the adsorption capacity and mechanism. Interactions between DNA and positively charged biomacromolecules or Ca2+ led to DNA compaction, allowing greater DNA accumulation in pores. However, a high concentration of biomacromolecules led to the saturation of the goethite surface, inhibiting DNA adsorption. AFM imaging of goethite particles after adsorption suggested the formation of the DNA multilayer. The study advances understanding of the environmental behavior of exDNA and its interaction with iron oxyhydroxides, offering insights into developing more effective methods for ARGs removal in wastewater treatment plants. By manipulating the textural properties of goethite, it\'s possible to enhance exDNA removal, potentially reducing the spread of biocontamination in urban and industrial environments.

Previous studies have reported the role of some species of acidophilic bacteria in accelerating the dissolution of goethite under aerobic and anaerobic conditions. This has relevance for environments impacted by acid mine drainage and for the potential bioleaching of limonitic laterite ores. In this study, natural well-characterized goethite mineral samples and synthetic goethite were used in aerobic and anaerobic laboratory batch culture incubation experiments with ferric iron-reducing, acidophilic bacteria, including the lithoautotrophic species Acidithiobacillus (At.) thiooxidans, At. ferrooxidans, and At. caldus, as well as two strains of the organoheterotrophic species Acidiphilium cryptum. All bacteria remained alive throughout the experiments and efficiently reduced soluble ferric iron in solution in positive control assays. However, goethite dissolution was low to negligible in all experimental assays with natural goethite, while some dissolution occurred with synthetic goethite in agreement with previous publications. The results indicate that ferric iron-reducing microbial activity at low pH is less relevant for goethite dissolution than the oxidation of elemental sulfur to sulfuric acid. Microbial ferric iron reduction enhances but does not initiate goethite dissolution in very acidic liquors.

Reducing iron by hydroxylamine (HA) can promote the generation of reactive oxygen species (ROS) in the Fenton reaction and play a crucial role in the degradation of organic pollutants. However, the performance of this system at wider environmental thresholds is still not sufficiently understood, especially in the highly alkaline environments resulting from human activities. Here, we assessed the impact of solution pH on organic pollutant degradation by goethite with the addition of HA and H2O2. The solid phase variation and ROS generation were analyzed using Mössbauer spectroscopy, X-ray absorption near edge structure spectroscopy, and electron paramagnetic resonance analysis. This study found that under alkaline conditions, the system can continuously scavenge organic pollutants through oxygen-mediated generation of free radicals. At lower pH levels, organic pollutant decomposition, exemplified by the breakdown of bisphenol A (BPA), is primarily driven by the Fenton reaction facilitated by iron. As pH increases, hydroxyl radical (•OH) production decreases, accompanied by decreased BPA removal efficiency. However, the removal efficiency of BPA increased significantly at pH > 9. At pH 12, the removal of BPA exceeded that of the acidic condition after one hour, which is consistent with observations in soil system studies. Unlike the Fenton reaction, which is not sensitive to oxygen content, the removal of BPA under alkaline conditions occurs only under aerobic conditions. H2O2 is hardly involved in the reaction, and the depletion of HA becomes a critical factor in the decomposition of BPA. Importantly, in contrast to acidic conditions, where the dramatic decomposition of BPA occurs mainly in the first 10 min, the decomposition of BPA under alkaline conditions continued to occur over the 2 h of observation until complete removal. For natural systems, the remediation of pollutants depends more on the active time of ROS than on their reactivity. Therefore, this idea can reference pollution remediation strategies in anthropogenically disturbed environments.

Co-exposure soil studies of pollutants are necessary for an appropriate ecological risk assessment. Here, we examined the effects of two-component mixtures of metal oxide nanoparticles (ZnO NPs or goethite NPs) with the insecticide chlorpyrifos (CPF) under laboratory conditions in short-term artificial soil assays using Eisenia andrei earthworms. We characterized NPs and their mixtures by scanning electron microscopy, atomic force microscopy, dynamic light scattering and zeta potential, and evaluated effects on metal accumulation, oxidative stress enzymes, and neurotoxicity related biomarkers in single and combined toxicity assays. Exposure to ZnO NPs increased Zn levels compared to control in single and combined exposure (ZnO NPs + CPF) at 72 h and 7 days, respectively. In contrast, there was no indication of Fe increase in organisms exposed to goethite NPs. One of the most notable effects on oxidative stress biomarkers was produced by single exposure to goethite NPs, showing that the worms were more sensitive to goethite NPs than to ZnO NPs. Acetylcholinesterase and carboxylesterase activities indicated that ZnO NPs alone were not neurotoxic to earthworms, but similar degrees of inhibition were observed after single CPF and ZnO NPs + CPF exposure. Differences between single and combined exposure were found for catalase and superoxide dismutase (goethite NPs) and for glutathione S-transferase (ZnO NPs) activities, mostly at 72 h. These findings suggest a necessity to evaluate mixtures of NPs with co-existing contaminants in soil, and that the nature of metal oxide NPs and exposure time are relevant factors to be considered when assessing combined toxicity, as it may have an impact on ecotoxicological risk assessment.

The intricate organization of goethite nanorods within a silica-rich matrix makes limpet teeth the strongest known natural material. However, the mineralization pathway of goethite in organisms under ambient conditions remains elusive. Here, by investigating the multi-level structure of limpet teeth at different growth stages, it is revealed that the growth of goethite crystals proceeds by the attachment of amorphous nanoparticles, a nonclassical crystallization pathway widely observed during the formation of calcium-based biominerals. Importantly, these nanoparticles contain a high amount of silica, which is gradually expelled during the growth of goethite. Moreover, in mature teeth of limpet, the content of silica correlates with the size of goethite crystals, where smaller goethite crystals are densely packed in the leading part with higher content of silica. Correspondingly, the leading part exhibits higher hardness and elastic modulus. Thus, this study not only reveals the nonclassical crystallization pathway of goethite nanorods in limpet teeth, but also highlights the critical roles of silica in controlling the hierarchical structure and the mechanical properties of limpet teeth, thus providing inspirations for fabricating biomimetic materials with excellent properties.

Chromium (Cr) contamination, widely present in the environment, poses a significant threat to both ecology and human health. Microbial remediation technology has become a hot topic in the field of heavy metal remediation due to its advantages, such as environmental protection, low cost, and high efficiency. This paper focused on using various characterization and analysis methods to investigate the bioreduction effect and mechanism of microorganisms on Cr(VI) under various influencing factors. The main contents and conclusions were as follows: Shewanella oneidensis MR-1 was selected as the target strain for studying its reduction of Cr(VI) at different inoculation amounts, temperatures, pH values, time intervals, etc. The results indicated that S. oneidensis MR-1 exhibited an optimal reduction effect on Cr(VI) at pH 7 and a temperature of 35 °C. Additionally, electron shuttles (ESs), including humic acid (HA) and 9,10-antraquinone-2,6-disulfonate (AQDS), were introduced into the degradation system to improve the reduction efficiency of S. oneidensis MR-1. Upon adding goethite further, S. oneidensis MR-1 significantly enhanced its reducing ability by converting Fe(III) minerals to Fe(II) and reducing Cr(VI) to Cr(III) during electron transfer.

This study aimed to develop surface complexation modeling-machine learning (SCM-ML) hybrid model for chromate and arsenate adsorption on goethite. The feasibility of two SCM-ML hybrid modeling approaches was investigated. Firstly, we attempted to utilize ML algorithms and establish the parameter model, to link factors influencing the adsorption amount of oxyanions with optimized surface complexation constants. However, the results revealed the optimized chromate or arsenate surface complexation constants might fall into local extrema, making it unable to establish a reasonable mapping relationship between adsorption conditions and surface complexation constants by ML algorithms. In contrast, species-informed models were successfully obtained, by incorporating the surface species information calculated from the unoptimized SCM with the adsorption condition as input features. Compared with the optimized SCM, the species-informed model could make more accurate predictions on pH edges, isotherms, and kinetic data for various input conditions (for chromate: root mean square error (RMSE) on test set = 5.90 %; for arsenate: RMSE on test set = 4.84 %). Furthermore, the utilization of the interpretable formula based on Local Interpretable Model-Agnostic Explanations (LIME) enabled the species-informed model to provide surface species information like SCM. The species-informed SCM-ML hybrid modeling method proposed in this study has great practicality and application potential, and is expected to become a new paradigm in surface adsorption model.