Dissolved black carbon (DBC) within aquatic dissolved organic matters demonstrates potent photochemical activity, yet its effects on emerging contaminant transformation and structure-reactivity relationships remain inadequately characterized. In this study, benzodiazepines were employed as model emerging contaminants to investigate the photoactivity, mediation effect, and structural-activity relationships of five DBC samples and four well-studied dissolved humic substances (DHSs) under simulated sunlight irradiation. DBC efficiently generated superoxide anions (O2·-), singlet oxygen (1O2), and triplet excited states, thereby facilitating the phototransformation of benzodiazepines. Under DBC mediation, midazolam and flurazepam achieved transformation rates of 61.1-99.5% and 19.0-84.6%, respectively, within 8 h, exceeding direct phototransformation efficiencies (1.3-13.3%). Triplet excited states were identified as the dominant reactive intermediates, contributing more than 46.7% to the photoreactions. At equivalent total organic carbon levels, DBCs averagely exhibited 1.3-, 2.7-, and 3.3-fold higher photoactivity (O₂·-, ¹O₂, and triplet excited states) alongside 2.5- and 4.7-fold enhanced benzodiazepine (midazolam and flurazepam) transformation compared to DHSs based on quantum yield measurements. Phototransformation pathways of benzodiazepines via DBC-mediation included ¹O₂ oxidation and charge transfer with triplet excited states, generating charge-separated intermediates that subsequently induce ring cleavage and coupling reactions. The molecular structures of DBC and DHS were characterized using UV-visible spectroscopy and Fourier transform-ion cyclotron resonance mass spectrometry. To elucidate the structure-reactivity relationship, Spearman rank correlation analysis, structural equation modeling, and orthogonal partial least squares regression were employed. The results identify molecular weight, aromaticity, and oxidation degree as key structural determinants of photoactivity. Low-molecular-weight compounds containing condensed aromatic structures and lignins demonstrate superior photoactivity in DBC/DHS structures, driving triplet excited-state and ¹O₂ formation, while O2·- might be generated from different structures. This study elucidated DBC mediation mechanisms and structure-reactivity relationships in benzodiazepine phototransformation, identifying low-molecular-weight fractions containing condensed aromatic and lignin moieties as dominant photoactive drivers in aquatic environment.

Sulfur Black 1 (SB1) is a widely used dye in the textile industry. Its dyeing process generates significant amounts of wastewater containing high-molecular-weight, refractory, and toxic organic pollutants, along with sulfate. This study proposed a novel sulfur-circular process integrating persulfate-based advanced oxidation process (AOP), microbial sulfate reduction, and gas stripping-adsorption to simultaneously remove SB1 and recover sodium sulfide (Na2S) from dyeing wastewater. In a 542-day trial, persulfate activation by zero-valent iron particles generated sulfate radicals (SO4•-) and hydroxyl radicals (•OH), achieving 98% oxidative degradation of SB1 in simulated dyeing wastewater. The AOP-treated wastewater, which contained biodegradable organic by-products and sulfate, was subsequently treated in an upflow anaerobic packed-bed sulfidogenic reactor (UAPSR). In the UAPSR, 42.7‒64.2% of sulfate was reduced, producing 60‒150 mg S/L dissolved sulfide. Meanwhile, the organic AOP by-products were efficiently mineralized, with a total organic carbon removal efficiency of about 80%. Fermentative bacteria (e.g., Lactococcus and Acidipropionibacterium) converted high-molecular-weight organic oxidation by-products into low-molecular-weight organics, which were further mineralized by sulfate-reducing bacteria (e.g., Desulfobacter and Desulfovibrio). Functional genes related to sulfur and carbohydrate metabolisms were also identified. Moreover, over 99% of dissolved sulfide in the UAPSR effluents was stripped and then absorbed with a NaOH solution, enabling the recovery of Na2S as a low-cost solubilizer recycled for the SB1 dyeing process. This study offers essential fundamentals for developing cost-effective and closed-loop technologies to treat wastewater containing refractory dyes and other persistent organic pollutants.

Pharmaceutical residues in the environment and their transformation mechanism are important challenges in environmental pollution research. The present study investigated the transformation mechanisms and reaction kinetics of oxazepam, a representative of benzodiazepine pharmaceutical, with two typical water treatment oxidants including HOCl and ∙OH in aqueous solution through theoretical calculations and experimental verification. The results showed that oxazepam is a chiral molecule with two enantiomers in equal proportions. The reactions between oxazepam and HOCl can be classified into Cl-substitution, OH-substitution, and bond-fission reactions. Among these substitutions, the Cl-substitution reaction at the N23 site was most likely to occur. The bond-fission reactions were predominated by the cleavage of the C27-N29 bond, which could lead to further bond cleavage reactions. The reactions between oxazepam and ∙OH involved the addition and H-abstraction pathways, with the addition reactions at the C5, C13, and C17 sites being the top three major reaction pathways. The kinetics rate constants obtained by the density functional theory (DFT) calculation were 0.16 and 1.78 × 1011 M-1 s-1 for the reactions of oxazepam with HOCl (kHOCl, M-1 s-1) and ∙OH (k·OH, M-1 s-1) respectively, which are basically consistent with the experimental results. This comprehensive understanding of the reaction mechanisms of oxazepam with HOCl and ∙OH based on quantum chemical calculations is crucial for exploring the chlorination and advanced oxidation of benzodiazepine pharmaceuticals.

Textile effluents are important sources of pollutants in aquatic environments. The textile industry in China has been relocating from developed to less developed regions, yet the potential environmental impact of textile effluents remains unclear. Here, we investigated the acute toxicity of wastewater collected from different processing units of two textile wastewater treatment plants (WWTPs) in a large industrial park in Guangxi province (Southwest China), using whole effluent toxicity testing. Moreover, we explored the relationships between the toxicity of wastewater and its characteristics, including physicochemical parameters, heavy metals, fluorescence intensity, and non-persistent and persistent organic pollutants. Untreated textile effluents were highly toxic to all test organisms, with toxic units reaching 42.9 for lux-modified bacteria, 14.0 for green algae, 10.1 for duckweed, and 17.3 for zebrafish embryos. Their toxicity was reduced significantly but not removed completely, following treatment processes that included coagulation, anaerobic-aerobic process, Fenton oxidation process, chlorine disinfection and wetland treatment systems. In the wetland effluent, both toxicity and physicochemical parameters met the textile effluent discharge standards in China and other countries. The toxicity of wastewater was associated with various characteristics, such as chemical oxygen demand (COD), fluorescence intensity related to fulvic acid-like materials, 4-nonylphenol, bisphenol A, bis(2-ethylhexyl) phthalate, perfluorobutane sulfonic acid, and acenaphthene. These results suggest the effectiveness of the investigated WWTPs in treating textile effluents concerning both physicochemical parameters and acute toxicity. The present study highlights the importance of integrating ecotoxicological data alongside chemical data to enhance the risk assessment and evaluation of the environmental safety of effluent discharges.

Uranium contamination is a key issue in the sustainable development of nuclear energy. In this study, a cellulose/sericite hybrid aerogel with a layer-stacked network structure (MCC/AS-P) was prepared for uranium-contaminated wastewater treatment. Systematic characterization and multiple-batch static adsorption experiments were conducted to analyze the aerogel's preparation, adsorption, and desorption. The kinetics demonstrated a noticeable transition between mass transfer diffusion control and mass transfer control, approaching adsorption equilibrium within 8 min and 180 min, respectively, wherein polymer layers led to a more stable adsorption process. Adsorption isotherm and thermodynamic studies established that the theoretical adsorption capacity of MCC/AS-P for U(VI) at T = 298 K could reach 374.5 mg.g(-1). The adsorption behavior was endothermic and spontaneous, and the DFT calculations demonstrated that the adsorption energy of MCC/AS for UO22+ was 506.5 kcal/mol. Temperature, U(VI) concentration, and desorption can all lead to a transition of the dominant mechanism between chemisorption and physisorption. After six swelling-deswelling adsorption cycles, the adsorption efficiency remained above 80%, and the structure remained intact. Furthermore, the excellent performance in terms of interference resistance and chemical stability offers potential for practical application.

Conventional biological treatment processes cannot efficiently and completely degrade nitroimidazole antibiotics, due to the formation of highly antibacterial and carcinogenic nitroreduction by-products. This study investigated the removal of a typical nitroimidazole antibiotic (ornidazole) during wastewater treatment by a biological sulfidogenic process based on elemental sulfur (S0-BSP). Efficient and stable ornidazole degradation and organic carbon mineralization were simultaneously achieved by the S0-BSP in a 798-day bench-scale trial. Over 99.8 % of ornidazole (200-500 mu g/L) was removed with the removal rates of up to 0.59 g/(m3 & sdot;d). Meanwhile, the efficiencies of organic carbon mineralization and sulfide production were hardly impacted by the dosed ornidazole, and their rates were maintained at 0.15 kg C/(m3 & sdot;d) and 0.49 kg S/(m3 & sdot;d), respectively. The genera associated with ornidazole degradation were identified (e.g., Sedimentocter, Trichococcus, and Longilinea), and their abundances increased significantly. Microbial degradation of ornidazole proceeded by several functional genes, such as dehalogenases, cysteine synthase, and dioxygenases, mainly through dechlorination, denitration, N-heterocyclic ring cleavage, and oxidation. More importantly, the nucleophilic substitution of nitro group mediated by in-situ formed reducing sulfur species (e.g., sulfide, polysulfides, and cysteine hydropolysulfides), instead of nitroreduction, enhanced the complete ornidazole degradation and minimized the formation of carcinogenic and antibacterial nitroreduction by-products. The findings suggest that S0-BSP can be a promising approach to treat wastewater containing multiple contaminants, such as emerging organic pollutants, organic carbon, nitrate, and heavy metals.

The contamination characteristics, migration patterns and health risks of per- and polyfluoroalkyl substances (PFAS) were investigated in 66 Chinese paper products by using target and non-target screening methods. Among 57 target PFASs, 5 and 6 PFASs were found in the hygiene paper products (

Coastal ecosystems, facing threats from global change and human activities like excessive nutrients, undergo alterations impacting their function and appearance. This study explores the intertwined microbial cycles of carbon (C) and nitrogen (N), encompassing methane (CH4), nitrous oxide (N2O), and nitrogen gas (N2) fluxes, to determine nutrient transformation processes between the soil-plant-atmosphere continuum in the coastal ecosystems with brackish water. Water salinity negatively impacted denitrification, bacterial nitrification, N fixation, and n-DAMO processes, but did not significantly affect archaeal nitrification, COMAMMOX, DNRA, and ANAMMOX processes in the N cycle. Plant species age and biomass influenced CH4 and N2O emissions. The highest CH4 emissions were from old Spartina and mixed Spartina and Scirpus sites, while Phragmites sites emitted the most N2O. Nitrification and incomplete denitrification mainly governed N2O emissions depending on the environmental conditions and plants. The higher genetic potential of ANAMMOX reduced excessive N by converting it to N2 in the sites with higher average temperatures. The presence of plants led to a decrease in the N fixers' abundance. Plant biomass negatively affected methanogenetic mcrA genes. Microbes involved in n-DAMO processes helped mitigate CH4 emissions. Over 93 % of the total climate forcing came from CH4 emissions, except for the Chinese bare site where the climate forcing was negative, and for Phragmites sites, where almost 60 % of the climate forcing came from N2O emissions. Our findings indicate that nutrient cycles, CH4, and N2O fluxes in soils are context-dependent and influenced by environmental factors and vegetation. This underscores the need for empirical analysis of both C and N cycles at various levels (soil-plant-atmosphere) to understand how habitats or plants affect nutrient cycles and greenhouse gas emissions.

Textile industry uses varieties of chemicals including perand polyfluoroalkyl substances (PFAS). PFAS are known to be persistent and incompletely removed in wastewater treatment plants (WWTPs). So far, little is known about what types of PFAS are used in the textile industry and their potential risks. Here we investigated PFAS in two WWTPs and a receiving river of a textile industrial park in Guangxi, China, by using both target and non-target analyses over a two-year period. The target analysis identified 11 specific PFAS, while the non-target analysis revealed a list of 648 different PFAS, including both legacy and emerging substances. Notably, perfluorooctanoic acid (PFOA) was still the most prevalent compound detected. Of particular concern was the finding that the investigated WWTPs, which employs an A/O (Anaerobic/Aerobic) process, exhibited a poor removal efficiency for PFAS. The average removal rate was only 22.0 %, indicating that the current treatment processes are inadequate in effectively mitigating PFAS contamination. Correlation analysis further highlighted the potential for PFAS to be transported from WWTPs to the receiving river, revealing a significant and strong positive correlation between the PFAS in the WWTP effluent and those of the river. Perfluorooctanesulfonic acid (PFOS) and two emerging PFAS (DTXSID30240816 and DTXSID90240817) were identified to have high ecological risks in the receiving river. Notably, these two emerging PFAS are homologues, and their presence in WWTPs has been poorly reported. The findings highlight the wide use and persistence of PFAS in current textile WWTPs, indicating potential long term risks to the receiving environment.

The removal of radioactive element thorium from the wastewater of rare earth (RE) industry is a significant concern in terms of environment. Here, we reported a kind of porous silica adsorbents functionalized by alpha-aminophosphorus extractants for ultra-selective adsorption of thorium from rare earths and other metals. Both adsorbents (ASG-AP modified with aminophosphonic acid and ASG-NP with neutral extractant) exhibit excellent adsorption selectivity towards thorium other than the coexisting ions (RE3+, Ca2+, Fe3+, Mg2+ and Al3+). The adsorption capacity of ASG-AP toward thorium reaches 131.1 mg g(-)(1). Using ASG-AP as the adsorbent, the concentration of thorium in simulated radioactive wastewater decreased significantly from 5.5 mg L-1 to 0.007 mg L-1. The selectivity was derived from the structure of adsorbents, the steric hindrance of the functional groups, and the chemical valence and size of Th(IV) species. The adsorption of thorium was an endothermic process obeyed the pseudo-second-order model and Langmuir isotherm model. XPS analysis and Density Functional Theory (DFT) calculation revealed that the P=O/P-OH and >N- functional groups were involved in the coordination of thorium cations. Taking the ultra-selectivity of the adsorbents, the mechanical strength and chemical/physical stability of silica into account, this kind of functionalized silica would act as promising adsorbents for the removal of trace thorium in the wastewater of rare earth industry.

Many organic chemicals are present in aquatic environments, but how to screen and prioritize these chemicals has always been a difficult task. Here we investigated organic chemicals in the West River Basin by using a developed non-target identification workflow. A total of 957 chemicals were tentatively identified, with 96 assigned as high confidence levels by matching with reference standards, MassBank spectral library, and using CompTox Chemistry Dashboard database as the compound library for MetFrag. More pesticides and their transformation products (e.g., metolachlor ESA, acetochlor ESA, deethylatrazine, and hydroxyatrazine) were detected in the wet season due to the increasing usage. High detection of pharmaceutical and personal care products and their transformation products in the tributaries was linked to rural farming and human activities. Irbesartan that is used to treat high blood pressure was recognized in the river and positive correlations between some detected chemicals and irbesartan were observed, indicating a domestic wastewater source. Ecological risks of the identified chemicals were calculated by toxicological prioritization ranking schemes, and 24 chemicals showed high ToxPi scores in the river. The results from this study show the presence of a large number of emerging organic chemicals in our waterways, and demonstrated conceptual schemes for integrating risk assessment into a non-target screening workflow.

Persulfate is considered as a promising oxidant, thus the improvement of waste activated sludge (WAS) treatment with persulfate was widely regarded as a promising technology and had been intensively investigated in recent years. However, doubts and debates about its technical and economic viability in full-scale scenarios have been raised. Interestingly, so far, no efforts have been made on either systematic summarization or critical thinking of the application of persulfate to improve WAS treatment. Therefore, it is time to assess whether and how to utilize persulfate in future WAS treatment. The present paper provided an extensive review of the mechanisms, potentials and application of persulfate in WAS treatment. The current understanding of the activation modes and mechanisms of persulfate in sludge treatment were described. Besides, the performance, mechanism and disadvantages of persulfate-based pretreatment in fermentation, digestion and dewatering process were discussed, and the role of persulfate on the removal and control of the toxicity in sludge was paid special attention. The results showed that the oxidant and interaction with microorganisms of persulfate played an important role in improving sludge treatment. Knowledge gaps and current limitations of the persulfate-based applications were identified, and perspectives on the development of persulfate-based applications were discussed. Persulfatebased technology has a great potential in improving WAS treatment, but the practical application of this technology still needs further development and larger scale demonstration. Overall, this review provided a comprehensive current understanding, future directions, and insights into issues related to the application of persulfate to improve WAS.

Antibiotic contamination in drinking water has attracted widespread attention. The pollution condition of six macrolide antibiotics (erythromycin-H2[KG-*2/5]O, clarithromycin, oleandomycin, roxithromycin, leucomycin, and tylosin) in two drinking water treatment plants was monitored, and the reaction mechanism of tylosin, a typical macrolide antibiotic, during chlorination disinfection treatment was investigated. The results showed that the six macrolide antibiotics can be widely detected in the drinking water treatment processes; however, their concentrations were generally very low. The concentrations of macrolide antibiotics in the influents and effluents ranged from 0.18 ng·L-1 to 3.97 ng·L-1 and 0.02 ng·L-1 to 1.91 ng·L-1, respectively. The removal rates of the six macrolides in the drinking water treatment were different, ranging from 18% (oleandomycin) to 100% (erythromycin- H2[KG-*2/5]O). The degradation of the six macrolides during chlorination was slow and greatly affected by water quality parameters. The chlorination degradation of tylosin followed the second-order reaction kinetic mode, with the kinetic rate constant of 0.77 L·(mol·s)-1 at pH 7.0. Nine chlorination degradation products of tylosin were detected, and the reaction pathways primarily included tertiary amine hydroxylation, aromatic oxidation, and epoxy addition.

Recent industrial relocation in China causes lots of environment concerns including risks of emerging contaminants (ECs). Herein, the occurrence, fate, removal and ecological risks of 34 per- and polyfluoroalkyl substances (PFAS), 17 endocrine disrupting chemicals (EDCs), 16 phthalate esters (PAEs), and 23 polycyclic aromatic hydrocarbons (PAHs) were investigated in two textile WWTPs (conventional and Fenton-modified) from a large textile industrial park in Southwest China. Totally 50 ECs were identified and the levels followed the order of PAEs > EDCs > PFAS ≈ PAHs. The EDCs predominated in textile washing and rinsing wastewater whereas the PAEs did in desizing wastewater. Biphasic correlations of log Kd and log P, molecular weight, and numbers of rings (r2 = 0.63-0.66, p < 0.01) were observed for PAHs, suggesting that hydrophobicity might not facilitate adsorption of super-hydrophobic PAHs onto activated sludge. 63-69% of detected ECs were effectively removed by two textile WWTPs with removal efficiencies ≥ 80%, which were much higher than previous reports. Fenton processing enhanced the removal efficiencies for long-chain PFAS rather than short-chain PFAS. The PAEs and EDCs posed a medium-to-high risk to aquatic organisms and were screened as the priority ECs. To date, such a comprehensive investigation for ECs has not been previously conducted in textile WWTPs and this study provides basic information about regional chemical emission inventory of ECs.

Triclocarban (TCC) is an antimicrobial agent commonly used in many household and personal care products, and has been found persistent in the aquatic environment. Here we elucidate the kinetics and mechanism of TCC degradation during chlorination process by density functional theory (DFT) calculation and experimental verification. Results showed that hypochlorous acid (HOCl)/hypochlorite (OCl−) reacted with TCC via Cl-substitution, OH-substitution and C–N bond cleavage pathways. The reactivity of OCl− (2.80 × 10−7 M−1 s−1) with TCC was extremely low and HOCl (1.96 M−1 s−1) played the dominant role in TCC chlorination process. The N site of TCC was the most reactive site for chlorination. The second-order rate constants, which are determined using density functional theory (DFT) (kTCC−chlorineC, 1.96 M−1 s−1), can be separated into reaction rate constants related to the reactions of HOCl and OCl− with different isomers of TCC (TCC2 and TCC6). The obtained kTCC−chlorineC was consistent with the experimental determined second-order rate constant (kTCC−chlorineE, 3.70 M−1 s−1) in chlorination process. Eight transformation products (TP348, TP382, TP127, TP161, TP195, TP330, TP204, and TP296) were experimentally detected for chlorination of TCC, which could also be predicted by DFT calculation. Explicit water molecules participated in the chlorination reaction by transmitting the proton and connecting with TCC, HOCl/OCl− and other H2O molecules, and obviously reduced the energy barrier of chlorination.

The UV/chlorine process, by combining chlorination with UV irradiation, has been recently considered as a highly efficient advanced oxidation process (AOP) technology in water treatment. Nitrobenzene (NB), benzoic acid (BA), and p-chlorobenzoic acid (pCBA) are widely used as model probe compounds in the UV/chlorine system to calculate the second-order rate constants of the specific radical reaction with target contaminates by a competitive kinetics method. A comprehensive understanding of probe compounds' reaction mechanism with reactive radicals is critical for investigation of the UV/chlorine reaction system. Here, we evaluated the radical-mediated reaction kinetics and mechanism of NB, BA, and pCBA in the UV/chlorine process using theoretical calculations and experimental studies. The main reactive radicals •OH, •ClO, and •Cl in the UV/chlorine process for the initial reaction with NB, BA, and pCBA can be explained by H-abstraction and addition pathways. The ΔE 0,≠ values for the •OH reaction with NB, BA, and pCBA were in the range of 5.0-8.0, 3.7-8.2, and 3.4-8.2 kcal mol-1, respectively. The ΔE 0,≠ values for •ClO and •Cl reactions with these three probe compounds were higher than those of •OH, indicating slower •ClO- and •Cl-initiated reactions than that of the •OH-initiated reaction. The theoretically calculated radical-mediated reaction kinetic rate constants (k CP C) for NB, BA, and pCBA were 4.58 × 10-3, 1.28 × 10-2, and 1.6 × 10-2 s-1, respectively, which was consistent with the experimentally determined pseudo-first-order rate constant (k CP RR) in the UV/chlorine process. Interestingly, theoretical calculations showed that •ClO and •Cl played an important role in subsequent reactions of NB-OH radicals, converting to hydroxylated and chlorinated products, which were further confirmed by experimental products' identification. The findings from this study indicated that quantum chemistry calculations provide an effective means to investigate the reaction kinetics and mechanism of chemicals in the UV/chlorine process.

Blue carbon (C) ecosystems (mangroves, salt marshes, and seagrass beds) sequester high amounts of C, which can be respired back into the atmosphere, buried for long periods, or exported to adjacent ecosystems by tides. The lateral exchange of C between a salt marsh and adjacent water is a key factor that determines whether a salt marsh is a C source (i.e., outwelling) or sink in an estuary. We measured salinity, particulate organic carbon (POC), and dissolved organic carbon (DOC) seasonally over eight tidal cycles in a tidal creek at the Chongming Dongtan wetland from July 2017 to April 2018 to determine whether the marsh was a source or sink for estuarine C. POC and DOC fluxes were significantly correlated in the four seasons driven by water fluxes, but the concentration of DOC and POC were positively correlated only in autumn and winter. DOC and POC concentrations were the highest in autumn (3.54 mg/L and 4.19 mg/L, respectively) and the lowest in winter and spring (1.87 mg/L and 1.51 mg/L, respectively). The tidal creek system in different seasons showed organic carbon (OC) export, and the organic carbon fluxes during tidal cycles ranged from –12.65 to 4.04 g C/m 2 . The intensity showed significant seasonal differences, with the highest in summer, the second in autumn, and the lowest in spring. In different seasons, organic carbon fluxes during spring tides were significantly higher than that during neap tides. Due to the tidal asymmetry of the Yangtze River estuary and the relatively young stage, the salt marshes in the study area acted as a strong lateral carbon source.

The occurrence, fate, and environmental risk of 40 pharmaceutically active compounds (PhACs) from surface waters and sediments were comprehensively investigated in the Beijiang River, Xijiang River, and Maozhou River of the Pearl River basin, South China. Salicylic acid and diclofenac (antiinflammatory drugs), gemfibrozil (a lipid regulator), carbamazepine (an antiepileptic drug), diazepam (a psychoactive drug), and 2-methyl-4-chloro-phenoxyacetic acid (MCPA, a pesticide) were the most ubiquitous compounds in the studied region. The average concentrations of detected PhACs in surface waters and sediments ranged from 0.17 to 19.1 ng/L and 0.10 to 10.4 ng/g, respectively. Meanwhile, PhACs concentration in surface waters and sediments varied greatly among and within the Beijiang River, Xijiang River, and Maozhou River. The largest annual flux of PhACs of the Xijiang River and Beijiang River was more than 11 000 kg per annum, whereas only 25.7 kg/a in the Maozhou River. In addition, the estimated emissions of PhACs in the Beijiang River, Xijiang River, and Maozhou River ranged respectively from 0.28 to 4.22 kg/a, 0.12 to 6.72 kg/a, and 6.66 to 91.0 kg/a, and the back-estimated usage varied with a range from 12.0 to 293 kg/a, 6.79 to 944 kg/a, 368 to 17 459 kg/a. Moreover, the emissions of PhACs showed a close relationship with the gross domestic product (GDP) of each city along the Pearl River. The environmental risk assessment suggested that diazepam and ibuprofen had a moderate risk in this region.

The use of cocatalyst in Fenton-like reactions has been demonstrated as a reliable approach to improve their efficiency via accelerating the circulation of Fe3+/Fe2+. In this study, we for the first time used natural pyrite (FeS2) as a Fenton-like cocatalyst to improve the reactivity of Fe3+ instead of the widely investigated molybdenum disulfide that releases potential harmful molybdenum ions. The presence of FeS2 significantly improved the degradation of sulfamethoxazole (SMX) by Fe3+-peroxymonosulfate (PMS); near complete removal of SMX by FeS2-Fe3+-PMS was achieved, while no obvious removal of SMX by Fe3+-PMS was noticed. Meanwhile, the surface area-normalized rate constant of SMX degradation by FeS2-Fe3+-PMS was more than 18 times higher than that by MoS2-Fe3+-PMS. FeS2-Fe3+-PMS worked effectively in a wide range of pH values from 3.0 to 10.0. Although hydroxyl radicals, sulfate radicals, superoxide anion radicals, and singlet oxygen were recorded by electron paramagnetic resonance spectroscopy, only sulfate radicals were mainly responsible for the degradation. Sulfide ions were identified as one of the intermediates, but the reactive species generated by their interaction with PMS did not contribute to the degradation. FeS2 had a good stability by continually accelerating the circulation of Fe3+/Fe2+. The findings from this study reveal a highly efficient cocatalyst for Fenton-like reactions.

The effect of soluble cations on sorption in soils of a range of anionic PFAS is not well studied. We investigated the role of three common cations (Na+, Ca2+, and Mg2+) at varying solution concentrations on the sorption coefficients (K-d) of 18 anionic PFAS in two contrasting soils. The effective charge of the soil suspension (Zeta potential) became less negative as the concentration of these cations increased in the soil solutions. Perfluorinated compounds showed greater sorption than polyfluorinated compounds, with sulfonates of comparable chain lengths showing higher sorption than the carboxylates. We observed that the K-d values of several PFAS in the two soils were positively correlated with the concentration of cations in solution, especially in the presence of polyvalent cations (Ca2+ and Mg2+). The changes in sorption with cation concentration were more prominent for long-chain PFAS, with C > 10 PFAS being completely removed from solution at higher cation concentrations. The emerging PFAS (replacement compounds GenX and ADONA) showed negligible or little sorption (K-d < 0.6 L/kg). While several mechanisms contribute towards sorption of PFAS in the presence of cations, we conclude that the primary effect of cations is through screening of negative charges on head groups of PFAS and reorientation of molecules at the interface between organic matter surfaces and soil solution as well as charge neutralisation at soil solid surface. Screening of negative charges allows for greater hydrophobic interaction between hydrophobic tails of PFAS and soil surfaces resulting in greater sorption. Increasing cation concentrations in soil solutions could thus reduce mobility of PFAS through a soil profile.