The update of pipeline was quick over the last few years and the plastic pipes were widely used in the drinking water distribution systems (DWDSs), especially in the small-diameter pipes. In this study, the iron adsorptive characteristics and the affecting factors in unplasticized poly(vinyl chloride) (PVC-U) pipe were investigated. Results showed that the average amount of iron in the 10-year-old PVC-U pipe’s interior surface was 2.80 wt% which was almost 187 times larger than that in a new one. Goethite (α-FeOOH) and magnetite (Fe₃O₄) were the major iron compounds in the scales which covered on the old pipes’ interior surface and showed loose and porous images under a scanning electron microscope. Moreover, the influence of the iron concentration on the adsorption amount and rate was discussed. The adsorption amount was significantly influenced by iron concentration, but similar adsorption rate was discovered. Notably, iron was quantitatively adsorbed by PVC-U pipe during the experimental period in accordance with the pseudo second order kinetic model. Meanwhile, regression model and response surface methodology were used to analyze the regular of iron adsorption in different concentrations of chloride (Cl⁻), sulfate (SO₄ ²⁻), and hydroxyl (OH⁻). It can be concluded that Cl⁻ and OH⁻ showed the strong ability of iron adsorption which were larger than SO₄ ²⁻.

As a major organic component in aquatic sediments, black carbon (BC) could act as super surface sorbent for contaminants in soils or sediments due to its relatively structured carbon matrix with high degree of porosity and extensive surface area. In this work, the adsorption characteristics of Pb²⁺ were studied using BCs as adsorbents, which were extracted from four particle sizes of sediment from Lake Wuliangsuhai (WLSH), under conditions of different pH, BC content, and ionic strength. The results showed BC content near to 1 % of sediments from WLSH, in which BC1, BC2, BC3, and BC4 composited about 1.8, 1.6, 1.1, and 0.8 % in the sediment fractions of >180, 180–63, 63–32, and <32 μm, respectively. The specific surface area and the Pb²⁺ sorption capacity were increased with decreasing the particle size of BCs. Correspondingly, the adsorption percentage of Pb²⁺ increased with increasing initial pH and BC content but declined as the increase of ionic strengths. The Pb²⁺ sorption capacity was reached maximum at pH 5–6. Compared pre- to post-sorption BCs by SEM-EDS and FTIR, although the carboxyl (C=O) and phenol (OH) groups on BC fractions contributed to Pb²⁺ sorption, the main adsorption mechanism of BCs was the surface sorption at pH <6. Relatively, the contribution of BCs accounted for about 18 % of Pb²⁺ sorption capacity on sediments. This work is helpful to understand the environmental effects of different size fractions BCs extracted from natural sediments.

Monensin (MON) and salinomycin (SAL), known as polyether ionophore antibiotics (IPAs), are extensively used in livestock industry and can enter the environment via animal manure and agricultural runoff. Although some studies have investigated the environmental fate and transformation of IPAs, the lack of information on IPAs’ aqueous-phase chemical properties is a major hindrance for further in-depth research. This study was able to experimentally determine the acidity constants (pKa), metal-complex dissociation constants (Kdᵢₛₛ), and intrinsic aqueous solubility of MON species, and some of these properties of SAL. The pKₐ value of MON was found to be 4.5, close to other aliphatic carboxylic acids and the predicted value by the computer program ChemAxon. The metal-complex dissociation constants of MON were estimated to be 0.058 and 0.573 with sodium ion (Na⁺) and potassium ion (K⁺), respectively. The Kdᵢₛₛ value of SAL with sodium ion was found to be 1.31. Compared to the previous values determined in organic solvents, the Kdᵢₛₛ of MON in aqueous phase are several orders of magnitude higher but maintain the same relative selectivity toward metal ions (Na⁺ versus K⁺). The determined pKa and Kdᵢₛₛ values were also used to assess the aqueous solubility limits of different IPA species under different pH and metal ion concentrations. Results from this study provide more accurate information for the properties of IPAs. The obtained constants can be applied to predict the speciation of IPAs in various aquatic systems and help shed light on the environmental fate of IPAs.

The seed of Zanthoxylum bungeanum (Z. bungeanum) is a by-product of pepper production and rich in unsaturated fatty acid, cellulose, and protein. The seed oil obtained from traditional producing process by squeezing or extracting would be bad quality and could not be used as edible oil. In this paper, a new preparation method of Z. bungeanum seed kernel oil (ZSKO) was developed by comparing the advantages and disadvantages of alkali saponification-cold squeezing, alkali saponification-solvent extraction, and alkali saponification-supercritical fluid extraction with carbon dioxide (SFE-CO₂). The results showed that the alkali saponification-cold squeezing could be the optimal preparation method of ZSKO, which contained the following steps: Z. bungeanum seed was pretreated by alkali saponification under the conditions of adding 10 %NaOH (w/w), solution temperature was 80 °C, and saponification reaction time was 45 min, and pretreated seed was separated by filtering, water washing, and overnight drying at 50 °C, then repeated squeezing was taken until no oil generated at 60 °C with 15 % moisture content, and ZSKO was attained finally using centrifuge. The produced ZSKO contained more than 90 % unsaturated fatty acids and no trans-fatty acids and be testified as a good edible oil with low-value level of acid and peroxide. It was demonstrated that the alkali saponification-cold squeezing process could be scaled up and applied to industrialized production of ZSKO.

The main objective of this study was to investigate the optimum conditions for the Fenton-like process on phenol degradation, using Mn²⁺ as a supporting catalyst in the Fenton reaction. The effect of the independent factors [H₂O₂], [Fe²⁺], [Mn²⁺] and t (reaction time) was evaluated on the efficiency of phenol degradation at two pHs (3 and 5). The experimental arrangement adopted was the Box-Behnken delineation, with the phenol concentration after the treatments suggested as response variable. At less acidic pH (5), regardless of [Mn²⁺], it was observed that the conventional Fenton process was the most efficient alternative, considering the optimum condition: 2.65 mmol L⁻¹ for [H₂O₂], 0.36 mmol L⁻¹ for [Fe²⁺], and 90 min for t. It was observed that the addition of Mn²⁺ helped the phenol degradation at more acidic pH (3), obtaining the optimum condition: 6.17 mmol L⁻¹ for [H₂O₂], 0.36 mmol L⁻¹ for [Fe²⁺], 1.09 mmol L⁻¹ for [Mn²⁺], and 90 min for t.

The Tablas de Daimiel National Park (TDNP), a floodplain wetland located in the Upper Guadiana Basin (central Spain), receives pollution from wastewater treatment plants (WWTPs) discharging their treated sewage effluents (TSEs) to tributary channels to the wetland. The TSEs suffer transformations on their way to the TDNP, but the water quality is controlled only at the point of discharge. In this work, we analyse the change in water quality of the TSE from four urban WWTPs in the surroundings of the TDNP (Alcázar de San Juan, Daimiel, Manzanares and Villarrubia de los Ojos towns). The water samples were taken at the outlet of the plants and in the receiving environments, to analyse the water quality transformation of the TSE. The different discharge configurations of each WWTP have been related with the water quality transformation of their TSE, to interpret the influence of the hydro-geomorphology in the improvement or deterioration of the water quality of TSE. We found that the discharge of TSE into slow flow channels with macrophyte vegetation facilitates water self-purification but, with time, the accumulation of sludge in the beds of the effluents tends to be the cause of the deterioration of the water quality.

The performance and mechanisms of 4-nitrophenol (4-NP) degradation by the Fe⁰/bisulfite system were systematically investigated for the first time. The evidences presented in this study verified that O₂ was a crucial factor that affected the mechanism of Fe⁰/bisulfite-driven 4-NP degradation. In the Fe⁰/bisulfite/O₂ system, Fe⁰ acted as a supplier of Fe²⁺ to catalyze bisulfite oxidation that induced a chain reaction to produce reactive radicals for 4-NP degradation. While under N₂ purging condition, bisulfite worked as a specified reductant that facilitated the transformation of Fe³⁺ to nascent Fe²⁺ ions, which principally accounted for the reductive removal of 4-NP. The application of a weak magnetic field (WMF) efficiently improved the removal rate of 4-NP and did not alter the mechanisms in both Fe⁰/bisulfite/O₂ and Fe⁰/bisulfite/N₂ processes. The secondary radicals, HO·, SO₄ ·⁻, and SO₅ ·⁻, were considered as the most possible active oxidants contributing to the oxidative removal of 4-NP and even partial mineralization under an oxic condition. Compared with anoxic conditions, the performance removal of 4-NP by the WMF-Fe⁰/bisulfite/O₂ system showed less pHᵢₙᵢ dependence. To facilitate the application of WMF-Fe⁰/bisulfite/O₂ technology in real practice, premagnetization of Fe⁰ was employed to combine with bisulfite/O₂ and proved to be an effective and applicable method for 4-NP removal.

Land use conversion and fertilization have been widely reported to be important managements affecting the exchanges of greenhouse gases between soil and atmosphere. For comprehensive assessment of methane (CH₄) and nitrous oxide (N₂O) fluxes from hilly red soil induced by land use conversion and fertilization, a 14-month continuous field measurement was conducted on the newly converted citrus orchard plots with fertilization (OF) and without fertilization (ONF) and the conventional paddy plots with fertilization (PF) and without fertilization (PNF). Our results showed that land use conversion from paddy to orchard reduced the CH₄ fluxes at the expense of increasing the N₂O fluxes. Furthermore, fertilization significantly decreased the CH₄ fluxes from paddy soils in the second stage after conversion, but it failed to affect the CH₄ fluxes from orchard soils, whereas fertilizer applied to orchard and paddy increased soil N₂O emissions by 68 and 113.9 %, respectively. Thus, cumulative CH₄ emissions from the OF were 100 % lower, and N₂O emissions were 421 % higher than those from the PF. Although cumulative N₂O emissions were stimulated in the newly converted orchard, the strong reduction of CH₄ led to lower global warming potentials (GWPs) as compared to the paddy. Besides, fertilization in orchard increased GWPs but decreased GWPs of paddy soils. In addition, measurement of soil moisture, temperature, dissolved carbon contents (DOCs), and ammonia (NH₄ ⁺-N) and nitrate (NO₃ ⁻-N) contents indicated a significant variation in soil properties and contributed to variations in soil CH₄ and N₂O fluxes. Results of this study suggest that land use conversion from paddy to orchard would benefit for reconciling greenhouse gas mitigation and citrus orchard cultivation would be a better agricultural system in the hilly red soils in terms of greenhouse gas emission. Moreover, selected fertilizer rate applied to paddy would lead to lower GWPs of CH₄ and N₂O. Nevertheless, more field measurements from newly converted orchard are highly needed to gain an insight into national and global accounting of CH₄ and N₂O emissions.

Vinyl chloride (VC) is a frequent groundwater contaminant and a known human carcinogen. Bioremediation is a potential cleanup strategy for contaminated sites; however, little is known about the bacteria responsible for aerobic VC degradation in mixed microbial communities. In attempts to address this knowledge gap, the microorganisms able to assimilate labeled carbon (¹³C) from VC within a mixed culture capable of rapid VC degradation (120 μmol in 7 days) were identified using stable isotope probing (SIP). For this, at two time points during VC degradation (days 3 and 7), DNA was extracted from replicate cultures initially supplied with labeled or unlabeled VC. The extracted DNA was ultracentrifuged, fractioned, and the fractions of greater buoyant density (heavy fractions, 1.758 to 1.780 g mL⁻¹) were subject to high-throughput sequencing. Following this, specific primers were designed for the most abundant phylotypes in the heavy fractions. Then, quantitative PCR (qPCR) was used across the buoyant density gradient to confirm label uptake by these phylotypes. From qPCR and/or sequencing data, five phylotypes were found to be dominant in the heavy fractions, including Nocardioides (∼40 %), Sediminibacterium (∼25 %), Aquabacterium (∼17 %), Variovorax (∼6 %), and Pseudomonas (∼1 %). The abundance of two functional genes (etnC and etnE) associated with VC degradation was also investigated in the SIP fractions. Peak shifts of etnC and etnE gene abundance toward heavier fractions were observed, indicating uptake of ¹³C into the microorganisms harboring these genes. Analysis of the total microbial community indicated a significant dominance of Nocardioides over the other label-enriched phylotypes. Overall, the data indicate Nocardioides is primarily responsible for VC degradation in this mixed culture, with the other putative VC degraders generating a small growth benefit from VC degradation. The specific primers designed toward the putative VC degraders may be of use for investigating VC degradation potential at contaminated sites.