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The degradation rates and kinetics of one commonly used iodinated contrast medium, iohexol, were investigated and compared during ultraviolet (UV) photolysis, UV/H 2 O 2 and UV/ S 2 O 8 2 − advanced oxidation processes (AOPs). Results indicate that the iohexol degradation rate increased in the order of UV/H 2 O 2 < UV irradiation < UV/ S 2 O 8 2 − and followed pseudo-first-order kinetics. Increasing persulfate concentration significantly increased iohexol degradation rate, whereas increasing H 2 O 2 concentration caused reverse effect. Radical scavenging test results show that UV photolysis, OH and radicals all contributed to iohexol degradation during UV/ S 2 O 8 2 − , but OH was the main contributor during UV/H 2 O 2 and was consumed by excess H 2 O 2. The kinetic models of iohexol degradation by both AOPs were developed, and the reaction rate constants with OH and were calculated as 5.73 (±0.02) × 108 and 3.91 (±0.01) × 1010 M−1 s−1, respectively. Iohexol degradation rate remained stable at pH 5–9 during UV irradiation and UV/H 2 O 2 , but gradually decreased at pH 5–7 and remained stable at pH 7–9 during UV/ S 2 O 8 2 −. The presence of anions displayed inhibitory effects on iohexol degradation during UV/ S 2 O 8 2 − in the order of Cl − > HCO 3 − ≫ S O 4 2 − . UV/ S 2 O 8 2 − AOP exhibited high degradation efficiency and stability on the basis of UV irradiation, which can be applied as a promising degradation method for iohexol. UV/ S 2 O 8 2 − AOP can effectively mineralize iohexol to CO 2 but promoted the generation of toxic iodoform (CHI 3), and the subsequent chlorination had the potential to reduce the content of disinfection by-products; therefore, further evaluation of possible environmental hazards is warranted. • The degradation efficiency of iohexol increased in the order of UV/H 2 O 2 < UV irradiation < UV/ S 2 O 8 2 − . • The iohexol degradation by UV/H 2 O 2 oxidation was mainly contributed by OH radical without UV photolysis. • The rate constants of iohexol reacting with OH and · S O 4 − were calculated as 5.73 (±0.02) × 108 and 3.91 × 1010 (±0.01) M−1 s−1, respectively. • pH has a negligible impact on iohexol degradation during UV irradiation and slight influence during UV/ and UV/H 2 O 2. • Higher concentrations of chloride and bicarbonate (≥2 mM) inhibited iohexol degradation. [ABSTRACT FROM AUTHOR]

It is known that during spermatogenesis, pluripotent germ cells differentiate to become efficient delivery vehicles to the oocyte of paternal DNA, and the process is easily damaged by external poison. In this study, the effects of fluoride on the body weight, fluoride content in femur, testosterone levels in serum and testis, sperm quality, and the expressions of Y chromosome microdeletion genes and protein levels were examined in testes of Kunming male mice treated with different concentrations of 0, 25, 50, 100 mg/L of NaF in drinking water for 11 weeks, respectively. The results showed that compared with the control group, fluoride contents in three treatment groups were significantly increased and the structure of testes was seriously injured. The testosterone contents and the sperm count were decreased. Sperm malformation ratio was distinctly elevated. The expressions of Sly and HSF2 mRNA were markedly reduced in 100 mg/L NaF group and Ssty2 mRNA expression was dramatically decreased in 50 and 100 mg/L NaF groups. Meanwhile, the protein levels of Ssty2 and Sly were significantly reduced in 50 and 100 mg/L NaF groups and HSF2 protein levels were significantly decreased in 100 mg/L NaF group. These studies indicated that fluoride had toxic effects on male reproductive system by reducing the testosterone and sperm count, and increasing the sperm malformation ratio, supported by the damage of testicular structure, as a consequence of depressed HSF2 level, which resulted in the down-regulation of Ssty2 and Sly mRNA and protein. [ABSTRACT FROM AUTHOR]

The photocatalytic film Ce doped V x O y /TiO 2 was loaded on cordierite honeycomb (CHC), and this composite was prepared by sol-gel and dipping method, with Ce, oxides of V and TiO 2 as dopant and key substances, respectively. Using gaseous 1,2-dichlorobenzene to replace dioxin as target pollutant, dual degradation experiments at 140–280 °C were carried out (thermal decomposition and photodegradation), and the effects of preparation conditions on catalytic activity were investigated: doping amount of Ce, dipping time in the gel, the concentration of ammonium metavanadate (NH 4 VO 3 ) solution, dipping time in NH 4 VO 3 solution, sintering temperature. The gaseous samples were taken before and after the reactor and analyzed by gas chromatography. According to the results, the optimal preparation conditions were determined, and the corresponding removal rate was above 95% after 90 min of degradation at 280 °C. The composite was examined by ultrasonic to analyze the adhesive strength between the film and CHC, and further characterized by XRD and SEM. Furthermore, flue gas from waste incinerator was chosen as target pollutant, which contained PCDD/Fs, the industrial sidestream degradation experiment was carried out and showed excellent removal efficiency of the composite, the removal rate of PCDD/Fs reached ca. 90% after 90 min of degradation. [ABSTRACT FROM AUTHOR]

Modeling of cometabolic kinetics is important for better understanding of degradation reaction and in situ application of bio-remediation. In this study, a model incorporated cell growth and decay, loss of transformation activity, competitive inhibition between growth substrate and non-growth substrate and self-inhibition of non-growth substrate was proposed to simulate the degradation kinetics of phenol and trichloroethylene (TCE) by Pseudomonas putida. All the intrinsic parameters employed in this study were measured independently, and were then used for predicting the batch experimental data. The model predictions conformed well to the observed data at different phenol and TCE concentrations. At low TCE concentrations (<2mgl−1), the models with or without self-inhibition of non-growth substrate both simulated the experimental data well. However, at higher TCE concentrations (>6mgl−1), only the model considering self-inhibition can describe the experimental data, suggesting that a self-inhibition of TCE was present in the system. The proposed model was also employed in predicting the experimental data conducted in a repeated batch reactor, and good agreements were observed between model predictions and experimental data. The results also indicated that the biomass loss in the degradation of TCE below 2mgl−1 can be totally recovered in the absence of TCE for the next cycle, and it could be used for the next batch experiment for the degradation of phenol and TCE. However, for higher concentration of TCE (>6mgl−1), the recovery of biomass may not be as good as that at lower TCE concentrations. [Copyright &y& Elsevier]

Prometryn is a herbicide that is widely used and frequently detected in aqueous environment and soil. Prometryn is chemically stable, biologically toxic, and easily to accumulate in living bodies, which can cause accumulate in the environment and acute and chronic toxicity to living creatures. In this study, factors affecting the degradation kinetics of prometryn chlorination were studied, including solution pH, bromide and ammonium concentrations, and temperature. Prometryn reacted quickly with aqueous chlorine following the pseudo-first-order kinetics. The maximum pseudo-first-order rate constant (k app) appeared at pH 5 with the observed rate constant (k obs) as 190. 08 h−1; the minimum value of k app reached at pH 9 with k obs as 5.26 h−1. The presence of Br− and increase of temperature both accelerated the degradation rate of prometryn during chlorination. The activation energy was calculated as 31.80 kJ/mol. Meanwhile 6 disinfection by-products (DBPs) were detected, namely: chloroform (CF), trichloroacetonitrile (TCAN), dichloroacetonitrile (DCAN), dichloroacetone, trichloronitromethane (TCNM), and trichloroacetone. Solution pH significantly affected the formation and distribution of DBPs. CF was the most formed carbonated DBP (C-DBP) with the maximum of 217.9 μg/L at pH 8, and its formation was significantly higher in alkaline conditions. For nitrogenated DBPs (N-DBPs), the yields of DCAN and TCAN were significantly higher in acidic conditions, while the maximum of TCNM achieved in neutral conditions. Because the toxicity of N-DBPs is higher than that of C-DBPs, the pH should be controlled in neutral or slight alkaline conditions during prometryn chlorination to effectively control DBP formation and reduce the related toxicity. [Display omitted] • Prometryn chlorination followed pseudo-first-order kinetics. • The highest prometryn degradation rate happened at pH 5. • Br− promote prometryn degradation during chlorination, while NH 4 + inhibited it. • The degradation rate of prometryn increased with increasing temperature. • Solution pH should be controlled at around 7 to reduce the toxicity of DBPs. [ABSTRACT FROM AUTHOR]

Formation of bound residues (BR) has generally been considered as a detoxification process for organic contaminants. BR is an indispensable component for risk assessment of pesticides. In this study, BR of 14C-pyraoxystrobin in three soils cultivated for 100 days were characterized in light fraction (LF), loosely combined humus (LCH), stably combined humus (SCH), humic acid (HA), fulvic acid (FA), and humin. Isotope labeling technique was used to detect the distribution of BR of 14C-pyraoxystrobin in the six fractions of soil organic matter (SOM). The results showed that the amount of total BR was positively correlated with the SOM content (p < 0.05). The BR of 14C-pyraoxystrobin in cambisol soil was largest at 31.26 ± 0.04% of the induced radioactivity. During the whole incubation period, the BR of pyraoxystrobin in LCH of the three soils were consistently higher than that in SCH, and the amount of BR in FA was consistently greater than that in HA. The BR of 14C-pyraoxystrobin bound with humin increased over time. In addition, a degradation product 3-(4-chlorophenyl)-1-methyl-1 H -pyrazol-5-ol (M1) from the hydrolysis of pyraoxystrobin was detected in cambisol soil, indicating the bonding of M1 with the HA separated from LCH (HA LCH) via ester or ether linkages. The results provide new insights into the fate of BR of pyraoxystrobin in soils and may help to develop an understanding for the risk assessment of pyraoxystrobin and other strobilurin fungicides. Image 1 • The distribution of BR of 14C-pyraoxystrobin in SOM fractions was studied. • The BR of pyraoxystrobin was rarely distributed in light fraction. • The detection of M1 can explain the high efficiency of HA LCH in cambisol soil. [ABSTRACT FROM AUTHOR]

Imidacloprid (IMI) is a widely used neonicotinoid insecticide effective against sucking and some chewing insects. Translocation and metabolism of IMI in plants are related to food safety. In this study, 14C-labeled IMI was used to investigate its translocation, transformation, radioactive IMI metabolites and possible metabolic pathways in cabbage. The amount of IMI accumulated in the edible part of cabbage accounted for 80.3–95.4% of the applied amounts by foliar application. There was a tendency to transport from edible parts to inedible parts. The proportions of extractable IMI decreased gradually from 92.4% to 83.0% in edible parts, greater than that in inedible parts over the experiment (0–19 days), while the bound residues showed an opposite trend. The half-life of IMI was determined as 33.0 and 63.0 days in the edible parts and whole plant, respectively. Five radioactive components including the parent IMI were detected by HPLC-LSC. The relative content of M1 was less than 0.01 mg kg−1, which was not required to identify according to the metabolic scheme proposed by the US Environmental Protection Agency. The metabolites N-nitro(1-6-chloro-3-pyridylmethyl)-4,5-dihydroxyimidazol-2-imine (M2), N-nitro(1-6-chloro-3-pyridylmethyl)-4/5-hydroxyimidazole-2-imine (M3) and 1/3-(1-6-chloro-3-pyridylmethyl)-2,4-imidazodione (M4) were identified by LC-QTOF-MS. The primary metabolism of IMI in cabbage included hydrolysis and oxidation. The residue level and daily intake values of IMI in cabbage were estimated to be 0.033–0.078 mg kg−1 and 9.56–20.01 ng d−1 kg−1, respectively, which were far below the maximum residue level and allowable daily intake values. • 14C labeling tracer and LC-QTOF-MS were utilized in this study. • Foliar application resulted in imidacloprid remaining mostly in edible cabbage tissue. • Imidacloprid underwent hydrolysis and oxidation with three metabolites in cabbage. • The MRL/ADI value of imidacloprid in cabbage were far below the recommended values. [ABSTRACT FROM AUTHOR]

Abstract An analysis of the Cd and mineral nutrients accumulation of upland rice was performed in an experimental field with hard-ridged plots containing three soils with exogenous Cd addition at rates of 0, 0.25, 0.5, 1, 2, 4, 8, 16 mg kg−1 five years prior to commence this experiment. Aims of this investigation were to study uptake, translocation, and accumulation of Cd by an upland rice (Huyou2) and effects of Cd addition on the accumulation of Fe, Zn, Ni, Ca, and Mg. The results demonstrate the mean Cd content in the plant parts, from highest to lowest, were as follows: root, stem, leaf, and brown rice. The Cd content in the brown rice of the upland rice was below the limit of Cd in rice (0.2 mg kg−1) from China (GB 2762-2017) when the amount of Cd added was ≤ 1 mg kg−1. This observation can be attributed to lower TF soil-grain of Cd in upland rice. Significant differences were observed between Cd concentrations present in brown rice from the three soils which can be mainly attributed to the differences in DTPA-extractable soil Cd because of different soil pH. Addition of high concentrations of Cd to soil was found to reduce Fe, Zn, Mg, and increased Ni uptake by the roots and their accumulation in brown rice. Altogether, results of this study suggest that it may be possible to cultivate upland rice in slightly Cd-polluted soils and Cd toxicity and accumulation in upland rice can be minimized by optimizing the macro and micronutrient composition of the soil. Graphical abstract Image 1 Highlights • Cd in the grains of the upland rice were below 0.2 mg kg−1 when the Cd added was ≤ 1 mg kg−1. • TFs within the rice plant declined with increasing soil Cd with a turning point at 0.25 mg Cd kg−1. • Higher Cd inhibited the accumulation of Fe, Zn, Ca, and Mg in the brown rice. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the mechanism of low Cd accumulation in crops using edible amaranth ( Amaranthus mangostanus L.) as a model. Fifteen amaranth cultivars were grown in long-term contaminated soil, and the differences in soil Cd mobilization, root uptake, and root-shoot translocation between low- and high-Cd accumulating cultivars were examined. The transport pathways of Cd across the root were further identified in Hoagland nutrient solution using the Ca channel blocker La 3+ , the ATP inhibitor 2, 4-dinitrophenol (DNP), and a nutrition-deficient culture. Cd concentrations in amaranth cultivars varied about six-fold and showed an elevated trend as the concentration of Ca and Zn increased (p < 0.01), but did not exhibit any correlation with Mg and Fe. The concentrations of essential metals (Ca, Mg, Zn, and Fe) in the rhizosphere of low-Cd cultivars were significantly lower than those of high-Cd cultivars, and decreased with decreasing levels of soluble rhizosphere exudates. These findings indicated that low co-mobilization of Cd with essential metals mediated by root-induced exudates of low-Cd cultivars contributed to its low accumulation in amaranth. Uptake of Cd was inhibited along with Ca by La 3+ and DNP, but was promoted by Ca or Fe deficiency treatment. Therefore, the Ca pathway is likely the mode of Cd entry into amaranth roots, although Zn and Fe transporters may also be involved. Low-Ca cultivars exhibited lower Cd uptake capability than high-Ca cultivars. The low translocation efficiency of Cd from root to shoot also contributed to its low content accumulation in edible parts of amaranth. [ABSTRACT FROM AUTHOR]

Al-powder-supported Pd, Rh, and Rh-Pd catalysts were synthesized through a spontaneous redox reaction in aqueous solutions. These catalysts hydrodebrominated 4- and 4,4′-bromodiphenyl ethers in supercritical carbon dioxide at 200 atm CO 2 containing 10 atm H 2 and 80 °C in 1 h. Diphenyl ether was the major product of Pd/Al. Rh/Al and Rh-Pd/Al further hydrogenated two benzene rings of diphenyl ether to form dicyclohexyl ether. The hydrogenolysis of C O bonds on diphenyl ether over Rh/Al and Rh-Pd/Al was observed to generate cyclohexanol and cyclohexane (<1%). With respect to hydrodebromination efficiency and catalyst stability, Rh-Pd/Al among three catalysts is suggested to be used for ex situ degradation of polybrominated diphenyl ethers in supercritical carbon dioxide. [ABSTRACT FROM AUTHOR]

Highlights: [•] The kinetics of dinoseb chlorination can be described by a second-order model. [•] Dinoseb chlorination is subject to hydroxylation, oxidation and substitution reactions. [•] High concentrations of TCNM and CF were generated and the yields varied with Cl2/C, time and pH. [•] TCNM formation favors acid pHs during dinoseb chlorination. [Copyright &y& Elsevier]

Triclosan is a widely used biocide against microorganisms and is ubiquitously distributed in the environment. Triclosan can be accumulated into plants from soil and hydroponic media. However, little information is currently available on the comparative fate of triclosan in plants under soil and hydroponics cultivation conditions and factors governing uptake. Therefore, this study was designed to comparatively elucidate the uptake mechanism of 14C-triclosan in youdonger (Brassica campestris subsp. Chinensis var. communis) grown under different soils and hydroponics and clarify dominant uptake factors. Results showed that 77.2% of 14C were accumulated in youdonger grown in a hydroponic system, while only 1.24%–2.33% were accumulated in the two soil-planting systems. In addition, the bioconcentration factor (BCF) of 14C-triclosan in soil-plant systems was approximately 400-fold smaller than that in the hydroponics. In the soil-planting system, a strong linear correlation was found between concentrations of triclosan in soil pore water and youdonger plant (R2 > 0.85, p < 0.01) at different incubation times. Therefore, triclosan in pore water might be a good indicator to estimate its accumulation in plants and is significantly affected by soil pH, clay, and organic matter contents. The estimated average dietary intakes of triclosan for youdonger grown in hydroponic and soil-planting systems were estimated to be 1.31 ng day−1 kg−1 and 0.05–0.12 ng day−1 kg−1, respectively, much lower than the acceptable dietary intakes of triclosan (83 μg day−1 kg−1), indicating no significant human health risks from youdonger consumption. This study provided insights into uptake routes of triclosan into youdonger plants from both soil and hydroponic systems, bioavailability of triclosan in different soils, and further assessment of human exposure to triclosan from youdonger. [Display omitted] • The BCF of triclosan in hydroponics was nearly 400 times that in soil-plant system. • The free triclosan was a crucial factor on uptake into the vegetable. • Triclosan in soil pore water was affected by soil pH, clay and OM. • No appreciable health risk to human via the consumption of the vegetable. [ABSTRACT FROM AUTHOR]

Abstract: Chlortoluron chlorination is studied in the pH range of 3–10 at 25±1°C. The chlorination kinetics can be well described by a second-order kinetics model, first-order in chlorine and first-order in chlortoluron. The apparent rate constants were determined and found to be minimum at pH 6, maximum at pH 3 and medium at alkaline conditions. The rate constant of each predominant elementary reactions (i.e., the acid-catalyzed reaction of chlortoluron with HOCl, the reaction of chlortoluron with HOCl and the reaction of chlortoluron with OCl−) was calculated as 3.12 (± 0.10)×107 M−2 h−1, 3.11 (±0.39)×102 M−1 h−1 and 3.06 (±0.47)×103 M−1 h−1, respectively. The main chlortoluron chlorination by-products were identified by gas chromatography–mass spectrometry (GC–MS) with purge-and-trap pretreatment, ultra-performance liquid chromatography–electrospray ionization-MS and GC-electron capture detector. Six volatile disinfection by-products were identified including chloroform (CF), dichloroacetonitrile, 1,1-dichloropropanone, 1,1,1-trichloropropanone, dichloronitromethane and trichloronitromethane. Degradation pathways of chlortoluron chlorination were then proposed. High concentrations of CF were generated during chlortoluron chlorination, with maximum CF yield at circumneutral pH range in solution. [Copyright &y& Elsevier]

Abstract Atmospheric fine particulate matters (PM 2.5) pose significant risks to human health through inhalation, especially in the rapidly developing China due to air pollution. The harmful effects of PM 2.5 are determined not only by its concentrations and hazardous components from diverse sources, but more by their bioavailable fractions actually absorbed by human body. To accurately estimate the inhalation risks of airborne metals, a physiologically based bioaccessibility method combining Simulated Lung Fluid (SLF) extraction and Diffusive Gradients in Thin-films (DGT) approaches was developed, representing the dissolution of particulate metals into lung fluid and the subsequent lung absorption of free metal cations in solution, respectively. The new method was used to compare the lung bioaccessibility of typical trace metals in PM 2.5 from three China megacities (Shanghai and Nanjing in the east, Guangzhou in south) during heavy pollution seasons. Generally, the SLF bioaccessibility (%) simulating the solubility of particulate metals in alveolar lung fluid was in order of Ni > Cd > Mn » Pb, while the succeeding DGT bioaccessibility representing labile metal fractions in solution phase absorbed directly by lung was lower and ranked as Ni ∼ Mn > Cd » Pb, thus Ni and Cd posed relatively higher potential risks owing to their high air pollution level and higher pulmonary bioaccessibility. Due to varied particle sources such as coal combustion and traffic emissions, some airborne metal concentrations (Pb, Ni) showed inconsistent spatial patterns with bulk PM 2.5 concentrations, and also varied bioaccessibility in different regions. The framework for PM 2.5 pollution risk assessments should be refined by considering both aerosol components and associated pollutants' bioaccessibility. Graphical abstract Image 1 Highlights • Different airborne metals show varied pulmonary bioaccessibility. • Airborne metal bioaccessibility varied with sources. • Lung fluid extraction simulates solubility of particulate metals. • DGT evaluates labile metals in solution efficiently absorbed by lung. • Aerosol risks should consider components and human bioaccessibility. [ABSTRACT FROM AUTHOR]

The degradation kinetics, pathways and disinfection by-products (DBPs) formation of iopamidol by chlorine and chloramines were investigated in this paper. The chlorination kinetics can be well described by a second-order model. The apparent second-order rate constants of iopamidol chlorination significantly increased with solution pH. The rate constants of iopamidol with HOCl and OCl − were calculated as (1.66 ± 0.09) × 10 −3 M −1 s −1 and (0.45± 0.02) M −1 s −1 , respectively. However, the chloramination of iopamidol fitted well with third-order kinetics and the maximum of the apparent rate constant occurred at pH 7. It was inferred that the free chlorine (i.e., HOCl and OCl − ) can react with iopamidol while the combined chlorine species (i.e., NH 2 Cl and NHCl 2 ) were not reactive with iopamidol. The main intermediates during chlorination or chloramination of iopamidol were identified using ultra performance liquid chromatography - electrospray ionization-mass spectrometry (UPLC-ESI-MS), and the destruction pathways including stepwise deiodination, hydroxylation as well as chlorination were then proposed. The regular and iodinated DBPs formed during chlorination and chloramination of iopamidol were measured. It was found that iodine conversion from iopamidol to toxic iodinated DBPs distinctly increased during chloramination. The results also indicated that although chloramines were much less reactive than chlorine toward iopamidol, they led to the formation of much more toxic iodinated DBPs, especially CHI 3 . [ABSTRACT FROM AUTHOR]

Vermi-biofilter (VF) System could be an efficient sludge treatment unit in regard of rates and extents of total chemical oxygen demand (TCOD) removal, particularly the first 10 days earthworm-treated. This study characterized the organic matter in sludge before and after VF system treatment, with or without earthworm stage. The 60 days earthworm-treated VF system reached a TCOD removal of 10,450 mg/L, bulk DOC removal of 89.5 mg/L, and earthworm density increase from 32 g/L to 43 g/L in sludge EBOM in 60 days of VF system operation. The aromatic proteins, soluble microbial byproduct-like fluorescent compounds and carboxylic components, aliphatic components (C-H related), hydrocarbon and carbohydrate materials were identified to be principally increased by 10 days earthworm-treated and then degradation in the nest days under VF system. [ABSTRACT FROM AUTHOR]

Combining pre-oxidation with activated carbon adsorption was explored as an ideal approach for removing iodine from water source to eliminate the formation of Iodinated trihalomethanes (I-THMs). Compared with permanganate and monochloramine, chlorine is more suitable as pre-oxidant to obtain higher active iodine species (HOI/I 2). Active iodine species adsorption using both powdered activated carbon (PAC) and granular activated carbon (GAC) can be well fitted the pseudo-second-order kinetic model indicating that chemical adsorption was the dominant mechanism for HOI/I 2 adsorption. The average pore size of activated carbons was the most strongly correlated with the adsorption capacity (R2 > 0.98), followed by methylene blue (R2 > 0.76), pore volume (R2 > 0.70) and iodine number (R2 > 0.67). Moreover, three models, including intraparticle diffusion, Byod kinetic, and diffusion-chemisorption were used to illustrate the mechanisms of HOI/I 2 adsorption. Chemical adsorption was the dominant mechanism for HOI/I 2 adsorption. In summary, at the molar ratio of [NaClO] and [I−] as 1.2, pre-chloriantion time of 5 min, subsequently dosage of 15 mg/L of PAC E with 20 min adsorption can remove 79.8% iodine. In addition, the combined process can eliminate 61%–87.2% of I-THMs in the subsequent chlor(am)ination. The results indicate that pre-chlorination combined with PAC can effectively removed HOI/I 2 and attenuate I-THMs formation in the subsequent disinfection process. [Display omitted] • Optimizing prechlorination can enhance HOI/I 2 formation, facilitating subsequent adsorption. • Active iodine species (HOI/I 2) were chemically adsorpted by PACs and GACs. • HOI/I 2 adsorption followed pseudo-second-order kinetics. • Film diffusion was the rate-limiting process for HOI/I 2 adsorption on activated carbon. • Pre-chlorination with PAC adsorption can effectively remove HOI/I 2 and attenuate I-THM formation. [ABSTRACT FROM AUTHOR]

With the increased detections of commonly used pharmaceuticals in surface water and wastewater, extensive attentions were paid recently to the fate and transport of these pharmaceuticals in the environment. Amitriptyline (AMI) is a tricyclic antidepressant widely applied to treat patients with anxiety and depression. In this study, the removal of AMI with palygorskite clay (PFl-1) was investigated under different physico-chemical conditions and supplemented by instrumental analyses. The uptake of AMI on PFl-1 was well fitted by the Langmuir isotherm with an adsorption capacity of 0.168 mmol g −1 at pH 6–7. The AMI uptake was fast and reached equilibrium in 15 min. The X-ray diffraction patterns showed no shift of the (110) peak position of palygorskite after AMI uptake. However, the (001) peak position of the minor component smectite (about 10%) shifted to lower angle as the amounts of AMI input increased. These results suggested surface uptake of AMI on palygorskite and interlayer uptake of AMI in smectite. As smectite is a common component of palygorskite clays, its role in assessing the properties and performances of palygorskite clays for the uptake and removal of contaminants should not be neglected. Overall, the high affinity of AMI for PFl-1 and strong retention of AMI on PFl-1 suggested that it could be a good adsorbent to remove AMI from wastewater. Palygorskite clays can also be a sink for many cationic pharmaceuticals in the environmental of the arid regions. [ABSTRACT FROM AUTHOR]

Organic chloramines (OCs) have become one of the research focuses in the field of drinking water treatment due to its limited oxidation and sterilization ability as well as potential cytotoxicity and genetic toxicity to the public. Among widespread OCs, produced by chlorinating cytosine are a typical one exists during chlorine disinfection. OCs degradation during UV, chlorination and UV/chlorine processes were systematically investigated. UV irradiation at 254 nm could effectively degrade OCs by 96.6% after 60 min, mainly because N–Cl bond had significant UV absorption at 250–280 nm leading to the generation of Cl• and HO•. Direct chlorination had poor removal of OCs with the OCs concentration increased first and then decreased as time went by. On the other hand, the removal of OCs during UV/chlorination was much higher than that during chlorination, but was worse than that during UV alone. pH had a minor effect on OCs decomposition via UV irradiation, whereas the effect was pronounced in the chlorination and UV chlorine processes. UV wavelength can affect the degradation of OCs with efficiency decreased in the order of UV 254 > UV 265 > UV 275. The total yields of disinfection by-products (DBPs) during the degradation of OCs followed UV/chlorine > UV > chlorination. CH and DCAA were the two dominant types of DBPs among detected 7 DBPs. DBPs yield followed the order of UV254 > UV265 > UV275 at pH 6.0 and 7.0. After UV 265 irradiation, DBPs yield slightly decreased by 2.4%, 3.0% and 6.6% with the pH increased from 6.0 to 9.0. The results can provide theoretical basis for effective control of OCs in drinking water. [Display omitted] • Stable organic chloramines were produced during cytosine chlorination. • UV irradiation can effectively degrade the generated organic chloramine. • The concentrations of DOC and TN in the solution were negligibly changed during chlorination. • OCs photodecay efficiency decreased in the order of 254 nm > 265 nm > 275 nm. • DBPs yield from OCs followed the order of UV/chlorine > UV > chlorination. [ABSTRACT FROM AUTHOR]

Iopamidol is a commonly used iodinated X-ray contrast media in medical field, and its residue in water can react with disinfectants to form highly toxic iodinated disinfection by-products (I-DBPs). This study investigated the degradation of iopamidol and formation of DBPs, especially iodinated trihalomethanes (I-THMs), during ferrate (Fe(VI)) pre-oxidation and subsequent chlor(am)ination under raw water background. It was found that iopamidol degradation efficiency in raw water by Fe(VI) at pH 9 could reach about 80%, which was much higher than that at pH 5 and pH 7 (both about 25%). With Fe(VI) dose increasing, iopamidol removal efficiency increased obviously. During the iopamidol degradation by Fe(VI), IO 3 − was the dominant product among all the iodine species. After pre-treated by Fe(VI), yields of THM4 and I-THMs can be reduced in subsequent chlor(am)ination. Besides, pH was a crucial factor for Fe(VI) pre-oxidition controlling DBPs. With the pH increasing from 5 to 9, the yield of THM4 kept increasing in subsequent chlorination but showed the highest amount at pH 6 in subsequent chloramination. The yield of I-THMs increased first and then decreased with the increase of pH in both subsequent chlorination and chloramination. I-THM concentrations in chlorinated samples were lower than chloraminated ones under acidic conditions but became higher under neutral and alkaline conditions. The total CTI of THMs during Fe(VI)-chloramination was higher than that during Fe(VI)-chlorination under neutral condition, but sharply decreased under alkaline conditions. In summary, Fe(VI)-chloramination subsequent treatment under alkaline conditions should be an effective method for iopamidol removal and DBP control. [Display omitted] • Iopamidol removal efficiency by Fe(VI) is higher at pH > 7 than that at pH ≤ 7. • IO 3 − was a dominant iodine product during iopamidol degradation by Fe(VI). • Fe(VI)-chloramination is effective in reducing THMs under alkaline conditions. • The toxicity contribution of CHI 3 is the highest in Fe(VI)-chloramination. [ABSTRACT FROM AUTHOR]

Rice grains are a methylmercury (MeHg) intake route for humans, especially in certain mercury (Hg)-contaminated areas. For rice plant growth, animal manure is commonly used as an organic fertilizer; however, its role in the formation of MeHg in paddy soils remains poorly understood. The aims of this study were thus to explore 1) the effect of chicken manure (CH) and cow manure (CO) addition on the production of soil MeHg and the accumulation of MeHg in rice plants and 2) the mechanism by which CH and CO addition affect the bioaccumulation of MeHg in grains. A pot experiment with different levels of CH and CO was carried out with newly deposited Hg-contaminated paddy soil. Two microcosm experiments were performed to explore the associated mechanisms. The results of the pot experiment showed that 0.1–1% CH and CO addition promoted the biomass of rice plants by 10–23% and increased the soil MeHg concentration by 34–143%, which exhibited a significant positive correlation with brown rice MeHg content. Organic fertilizer addition significantly increased MeHg bioaccumulation in rice plants and the ratio of MeHg to total Hg (THg) in brown rice. Organic fertilizer also increased the abundance of microbial methylators. The results of the microcosm experiments showed that organic fertilizer addition enhanced dissolved THg concentrations in soil and consequently increased the soil MeHg concentration. These results suggested that applying organic fertilizer to newly deposited Hg-contaminated soil may increase MeHg accumulation in grains due to enhanced Hg release and microbial methylator activity, leading to environmental health concerns. Image 1 • Organic fertilizer amendment increased the bioavailability of Hg in paddy soil. • Organic fertilizer amendment increased the production of net MeHg in paddy soil. • Organic fertilizer amendment increased the accumulation of MeHg in rice plants. [ABSTRACT FROM AUTHOR]

The formation and control of haloacetamides (HAcAms) in drinking water have raised high attention due to their high genotoxicity and cytotoxicity, especially the most cytotoxic one, diiodoacetamide (DIAcAm). In this study, the degradation of DIAcAm by UV/chlorination was investigated in terms of degradation kinetics, efficiency, influencing factors, oxidation products and toxicity evaluation. Results revealed that the degradation of DIAcAm by UV/chlorine process followed pseudo-first-order kinetics, and the rate constant between DIAcAm and OH radicals was determined as 2.8 × 109 M−1 s−1. The contribution of Cl to DIAcAm degradation by UV/chlorine oxidation was negligible. Increasing chlorine dosage and decreasing pH significantly promoted the DIAcAm degradation during UV/chlorine oxidation, but the presence of bicarbonate (HCO 3 −) and natural organic matter (NOM) inhibited it. The mass balance analysis of iodine species was also evaluated during UV/chlorine oxidation of DIAcAm. In this process, with DIAcAm decreasing from 16.0 to 0.8 μM-I in 20 min, IO 3 −, I− and HOI/I 2 increased from 0 to 6.3, 6.1 and 0.5 μM-I, respectively. The increase of CHO cell viability during DIAcAm degradation indicated that the toxicity of DIAcAm could be decreased by chlorination, UV irradiation and UV/chlorine oxidation treatments, in which UV/chlorine oxidation was more effective on toxicity reduction than chlorination and UV irradiation alone. Image 1 • UV/chlorine is more effective on DIAcAm degradation than UV and chlorination alone. • Kinetics models were established for DIAcAm degradation during UV/chlorine process. • DIAcAm degradation by UV/chlorine is remarkably affected by pH, HCO 3 − and NOM. • IO 3 −, I− and HOI/I 2 can be produced during UV/chlorine oxidation of DIAcAm. • DIAcAm toxicity can be reduced significantly by UV/chlorine oxidation. [ABSTRACT FROM AUTHOR]