4-methylphenol produced in freshwater sediment microcosms is not a bisphenol A metabolite

Mud matters: exploring the quality and composition of Estonia's curative mud deposits

The study focuses on the current state of curative mud deposits in Estonia as of 2022, examining changes over the past decade and providing essential information on curative mud quality. Total of 64 curative mud samples were collected in 2022, marking the first investigation into hazardous substances such as phenols, petroleum products, and pesticides. The study encompassed analyses of organic and mineral matter content, grain size, microbiology, and heavy metal concentrations, totalling 1649 measurements. Comparisons with previous data revealed stable organic matter concentrations in lake and marine sediments over the last decade. Microbiological contamination in curative mud samples was relatively low, indicating cleanliness. Petroleum product concentrations varied, with Haapsalu at 42 mg/kg, Värska at 118.6 mg/kg, and Käina below the limit of quantification. Phenol concentrations were generally below the limit of quantification, except for Värska. Pesticides were found in Värska samples, but in other sediments, levels were below the limit of quantification. Average heavy metal concentrations in curative mud decreased between 2013-2014 and 2022, remaining below the target value. The study's results are crucial for curative mud-related entrepreneurship in Estonia, facilitating compliance with the new regulatory standards. The comprehensive data obtained will contribute to the consistency and efficacy of curative mud-related practices in the country.

The relative contributions of Mn(III) and Mn(IV) in manganese dioxide polymorphs to bisphenol A degradation

Polymorphs of MnO2 comprise Mn(III) and Mn(IV), which are both strong oxidants capable of BPA degradation, but their relative contributions are unclear. To advance process understanding, the reactivities of biogenic MnO2 prepared using Roseobacter sp. AzwK-3b and synthetic MnO2 (i.e., hexagonal and triclinic birnessite) toward BPA were compared. Both colloidal and particulate biogenic MnO2, as well as triclinic birnessite, showed insignificant reactivity towards BPA, but degradation did occur when pyrophosphate (PP), a ligand for Mn(III), was present. Despite higher Mn(III) content of triclinic birnessite (38.6 %), only hexagonal birnessite with an Mn(III) content of 30.4 % degraded BPA without PP, and no rate increases were observed following the addition of PP. Similarly, colloidal MnO2 degraded BPA with nearly double the rate measured with particulate MnO2 (i.e., 1.24 ± 0.10 versus 0.73 ± 0.08 h-1), even though the Mn(III) contents were only 10 % different. The Mn(III) release rates from each MnO2 polymorph in the presence of PP correlated more strongly with the observed BPA degradation rates than with Mn(III) content, suggesting that both Mn(III) release rate and Mn(III) content govern MnO2-mediated BPA degradation. In natural settings, Mn(III) generally occurs in complexed form suggesting that laboratory testing should include ligands to derive environmentally relevant information about MnO2-mediated degradation of BPA and other compounds of concern.

Mn(III)-mediated bisphenol a degradation: Mechanisms and products

Bisphenol A (BPA) is a high production volume chemical with potential estrogenic effects susceptible to abiotic degradation by MnO₂. BPA transformation products and reaction mechanisms with MnO₂ have been investigated, but detailed process understanding of Mn(III)-mediated degradation has not been attained. Rapid consumption of BPA occurred in batch reaction vessels with 1 mM Mn(III) and 63.9 ± 0.7% of 1.76 ± 0.02 μmol BPA was degraded in 1 hour at circumneutral pH. BPA was consumed at 1.86 ± 0.09-fold higher rates in vessels with synthetic MnO₂ comprising approximately 13 mol% surface-associated Mn(III) versus surface-Mn(III)-free MnO₂, and 10-35% of BPA transformation could be attributed to Mn(III) during the initial 10-min reaction phase. High-resolution tandem mass spectrometry (HRMS/MS) analysis detected eight transformation intermediates in reactions with Mn(III), and quantum calculations proposed 14 BPA degradation products, nine of which had not been observed during MnO₂-mediated BPA degradation, suggesting mechanistic differences between Mn(III)- versus MnO₂-mediated BPA degradation. The findings demonstrate that both Mn(III) and Mn(IV) can effectively degrade BPA and indicate that surface-associated Mn(III) increases the reactivity of synthetic MnO₂, offering opportunities for engineering more reactive oxidized Mn species for BPA removal.

Degradation of Adsorbed Bisphenol A by Soluble Mn(III)

Bisphenol A (BPA), a high production volume chemical and potential endocrine disruptor, is found to be associated with sediments and soils due to its hydrophobicity (log K_OW of 3.42). We used superfine powdered activated carbon (SPAC) with a particle size of 1.38 ± 0.03 μm as a BPA sorbent and assessed degradation of BPA by oxidized manganese (Mn) species. SPAC strongly sorbed BPA, and desorption required organic solvents. No degradation of adsorbed BPA (278.7 ± 0.6 mg BPA g^-1 SPAC) was observed with synthetic, solid α-MnO₂ with a particle size of 15.41 ± 1.35 μm; however, 89% mass reduction occurred following the addition of 0.5 mM soluble Mn(III). Small-angle neutron scattering data suggested that both adsorption and degradation of BPA occurred in SPAC pores. The findings demonstrate that Mn(III) mediates oxidative transformation of dissolved and adsorbed BPA, the latter observation challenging the paradigm that contaminant desorption and diffusion out of pore structures are required steps for degradation. Soluble Mn(III) is abundant near oxic-anoxic interfaces, and the observation that adsorbed BPA is susceptible to degradation has implications for predicting, and possibly managing, the fate and longevity of BPA in environmental systems.

Biologically mediated abiotic degradation (BMAD) of bisphenol A by manganese-oxidizing bacteria

Bisphenol A (BPA), a chemical of environmental concern, is recalcitrant under anoxic conditions, but is susceptible to oxidative degradation by manganese(IV)-oxide (MnO₂). Microbial Mn(II)-oxidation generates MnO_2-bio; however, BPA degradation in cultures of Mn(II)-oxidizing bacteria has not been explored. We assessed MnO_2-bio-mediated BPA degradation using three Mn(II)-oxidizing bacteria, Roseobacter sp. AzwK-3b, Erythrobacter sp. SD-21, and Pseudomonas putida GB-1. In cultures of all three strains, enhanced BPA degradation was evident in the presence of Mn(II) compared to replicate incubations without Mn(II), suggesting MnO_2-bio mediated BPA degradation. Increased Mn(II) concentrations up to 100 µM resulted in more MnO_2-bio formation but the highest BPA degradation rates were observed with 10 µM Mn(II). Compared to abiotic BPA degradation with 10 μM synthetic MnO₂, live cultures of strain GB-1 amended with 10 μM Mn(II) consumed 9-fold more BPA at about 5-fold higher rates. Growth of strain AzwK-3b was sensitive to BPA and the organism showed increased tolerance against BPA in the presence of Mn(II), suggesting MnO_2-bio alleviated the inhibition by mediating BPA degradation. The findings demonstrate that Mn(II)-oxidizing bacteria contribute to BPA degradation but organism-specific differences exist, and for biologically-mediated-abiotic-degradation (BMAD), Mn-flux, rather than the absolute amount of MnO_2-bio, is the key determinant for oxidation activity.

Graphite-bridged indirect Z-scheme system TiO2-C-BiVO4 film with enhanced photoelectrocatalytic activity towards serial bisphenols

Due to the increase in the occurrence of bisphenols (BPs) in the environments, it is urgent to develop efficient and ecofriendly methods for their removal. A novel, indirect Z-scheme TiO₂-C-BiVO₄ film was prepared by a sol-gel method combined with hydrothermal carbonization. The doped graphite carbon was generated in situ from glucose, which acted as an electron-transfer bridge for the Z-scheme system to enhance the heterojunction tightness between TiO₂ and BiVO₄. This resulted in an increasing separation efficiency of photogenerated electrons and holes and a stronger redox ability of the TiO₂-C-BiVO₄ film for the degradation and detoxification of BPs. The degradation efficiency of BPs was over 95% in 240 min, except for that of 4,4'-sulphonyldiphenol (BPS) due to the presence of the OSO group, and all of the BPs were nearly completely mineralized when the reaction time reached 360 min. Consequently, the inhibition ratio towards Vibrio fischeri decreased significantly along with the loss and mineralization of aromatic intermediates during photoelectrocatalytic degradation. 2,2-bis(4-Hydroxyphenyl) butane (BPB), 4,4'-(1-phenylethylidene)-bisphenol (BPAP), and (4,4'-hexafluoroisopropylidene) diphenol (BPAF), with relatively high toxicity levels and lipophilicity and as toxic product precursors, require attention in terms of environmental safety. Overall, this work provides a promising and environmentally friendly way to remove BPs from water.

Fate of Bisphenol A in Terrestrial and Aquatic Environments

Bisphenol A (2,2-bis[4-hydroxyphenyl]propane, BPA), the monomer used to produce polycarbonate plastic and epoxy resins, is weakly estrogenic and therefore of environmental and human health interest. Due to the high production volumes and disposal of products made from BPA, polycarbonate plastic and epoxy resins, BPA has entered terrestrial and aquatic environments. In the presence of oxygen, diverse taxa of bacteria, fungi, algae and even higher plants metabolize BPA, but anaerobic microbial degradation has not been documented. Recent reports demonstrated that abiotic processes mediate BPA transformation and mineralization in the absence of oxygen, indicating that BPA is susceptible to degradation under anoxic conditions. This review summarizes biological and nonbiological processes that lead to BPA transformation and degradation, and identifies research needs to advance predictive understanding of the longevity of BPA and its transformation products in environmental systems.

Identification of 4-Hydroxycumyl Alcohol As the Major MnO2-Mediated Bisphenol A Transformation Product and Evaluation of Its Environmental Fate

Bisphenol A (BPA), an environmental contaminant with weak estrogenic activity, resists microbial degradation under anoxic conditions but is susceptible to abiotic transformation by manganese dioxide (MnO2). BPA degradation followed pseudo-first-order kinetics with a rate constant of 0.96 (±0.03) min(-1) in the presence of 2 mM MnO2 (0.017% w/w) at pH 7.2. 4-hydroxycumyl alcohol (HCA) was the major transformation product, and, on a molar basis, up to 64% of the initial amount of BPA was recovered as HCA. MnO2 was also reactive toward HCA, albeit at 5-fold lower rates, and CO2 evolution (i.e., mineralization) occurred. In microcosms established with freshwater sediment, HCA was rapidly biodegraded under oxic, but not anoxic conditions. With a measured octanol-water partition coefficient (Log K(ow)) of 0.76 and an aqueous solubility of 2.65 g L(-1), HCA is more mobile in saturated media than BPA (Log K(ow) = 2.76; aqueous solubility = 0.31 g L(-1)), and therefore more likely to encounter oxic zones and undergo aerobic biodegradation. These findings corroborate that BPA is not inert under anoxic conditions and suggest that MnO2-mediated coupled abiotic-biotic processes may be relevant for controlling the fate and longevity of BPA in sediments and aquifers.