Polypropylene microplastics aging under natural conditions in winter and summer and its effects on the sorption and desorption of nonylphenol.

Plastics in the environment undergo various aging effects. Due to the changes in physical and chemical properties, the sorption behavior of aged microplastics (MPs) for pollutants differs from that of pristine MPs. In this paper, the most common disposable polypropylene (PP) rice box was used as the source of MPs to study the sorption and desorption behavior of nonylphenol (NP) on pristine and naturally aged PPs in summer and winter. The results show that summer-aged PP has more obvious property changes than winter-aged PP. The equilibrium sorption amount of NP on PP is summer-aged PP (477.08 µg/g) > winter-aged PP (407.14 µg/g) > pristine PP (389.29 µg/g). The sorption mechanism includes the partition effect, van der Waals forces, hydrogen bonds and hydrophobic interaction, among which chemical sorption (hydrogen bonding) dominates the sorption; moreover, partition also plays an important role in this process. Aged MPs' more robust sorption capacity is attributed to the larger specific surface area, stronger polarity and more oxygen-containing functional groups on the surface that are conducive to forming hydrogen bonds with NP. Desorption of NP in the simulated intestinal fluid is significant owning to intestinal micelles' presence: summer-aged PP (300.52 µg/g) > winter-aged PP (291.08 µg/g) > pristine PP (287.12 µg/g). Hence, aged PP presents a more vital ecological risk.

A Novel Spectrophotometric Method for Determination of Percarbonate by Using N, N-Diethyl-P-Phenylenediamine as an Indicator and Its Application in Activated Percarbonate Degradation of Ibuprofen.

Sodium percarbonate (SPC) concentration can be determined spectrophotometrically by using N, N-diethyl-p-phenylenediamine (DPD) as an indicator for the first time. The ultraviolet-visible spectrophotometry absorbance of DPD•+ measured at 551 nm was used to indicate SPC concentration. The method had good linearity (R2 = 0.9995) under the optimized experimental conditions (pH value = 3.50, DPD = 4 mM, Fe2+ = 0.5 mM, and t = 4 min) when the concentration of SPC was in the range of 0-50 µM. The blank spiked recovery of SPC was 95-105%. The detection limit and quantitative limit were 0.7-1.0 µM and 2.5-3.3 µM, respectively. The absorbance values of DPD•+ remained stable within 4-20 min. The method was tolerant to natural water matrix and low concentration of hydroxylamine (<0.8 mM). The reaction stoichiometric efficiency of SPC-based advanced oxidation processes in the degradation of ibuprofen was assessed by the utilization rate of SPC. The DPD and the wastewater from the reaction were non-toxic to Escherichia coli. Therefore, the novel Fe2+/SPC-DPD spectrophotometry proposed in this work can be used for accurate and safe measurement of SPC in water.

Transport and interaction of cadmium and active sludge extracellular polymeric substances in saturated sand influenced by ionic strength and composition.

Artificial groundwater recharge with reclaimed water (secondary effluent from wastewater treatment plants) has become an important approach to solving water scarcity worldwide. Microorganisms in activated sludge can secrete many extracellular polymeric substances (EPS). However, information on the impact of EPS on the movement of heavy metals in porous media and their environmental effects on underground networks is limited. To assess this risk, we extracted EPS from the aerobic section of a wastewater treatment plant using hot sodium hydroxide and conducted experiments using one-dimensional sand columns to investigate how ion composition and strength affect the movement and interaction of cadmium (Cd) and EPS in porous media. The results showed that EPS facilitated Cd migration in porous media. Sodium (Na) and calcium (Ca) ions promoted the migration of Cd in porous media and EPS-Cd complexation. The effect of Ca was more significant than that of Na. As the Na adsorption ratio increased, the migration ability of Cd in porous media and the complexation ability of EPS with Cd decreased. Therefore, when estimating the migration of EPS and Cd in subsurface environments, careful consideration should be given to prevent the risk of groundwater pollution.

Performance of ultraviolet/persulfate process in degrading artificial sweetener acesulfame.

The degradation of the artificial sweetener acesulfame (ACE) was investigated using an ultraviolet (UV)365-activated peroxydisulfate (PDS) process. The results demonstrated that the ACE reaction rate with the UV/PDS process followed pseudo first-order kinetics (R2 > 0.9) under various conditions. A high dosage of PDS, alkaline condition, and the existence of NO3- and Cl- enhanced ACE degradation; however, a high dosage of ACE, the existence of HCO3-, humic acid, and fulvic acid, and a real water matrix did not facilitate the degradation of ACE. Four types of transformation products were detected in the degradation of ACE by UV/PDS, and the primary degradation pathways were oxidation, hydroxyl substitution, hydrolysis, and hydration. The hydroxyl radicals played a predominant role (71.31%) in the degradation of ACE by the UV/PDS process, followed by sulfate radicals (14.57%) and UV photolysis (8.83%). Both the degradation and mineralization rates of ACE using the UV/PDS process had significant advantages over that of the UV/H2O2 process regarding ACE degradation, indicating that the UV/PDS process is more promising for treating water containing ACE.

Degradation of norfloxacin in aqueous solution with UV/peroxydisulfate.

The frequent detection of antibiotics in water bodies gives rise to concerns about their removal technology. In this study, the degradation kinetics and mechanisms of norfloxacin (NOR), a typical fluoroquinolone pharmaceutical, by the UV/peroxydisulfate (PDS) was investigated. NOR could be degraded effectively using this process, and the degradation rate increased with the increasing dosage of PDS but decreased with the increasing concentration of NOR. In real water, the degradation of NOR was slower than that in ultrapure water, which indicated that laboratory results cannot be directly used to predict the natural fate of antibiotics. Further experiments suggested that the degradation of NOR was the most fast under neutral condition, the existence of HA or FA inhibited the degradation of NOR, and the presence of inorganic ions (NO3 -, Cl-, CO3 2- and HCO3 -) had no significant effect on degradation of NOR. Total organic carbon (TOC) removal rate (40%) indicated NOR was not completely mineralized, and six transformation products were identified, and possible degradation pathways of NOR had been proposed. It can be prospected that UV/PDS technology could be used for advanced treatment of wastewater containing fluoroquinolones.

Photoconversion of 2-Chloronaphthalene in Water.

The photoconversion of 2-chloronaphthalene (CN-2) in water in a simulated sunlight system was investigated. The photoconversion efficiency, photoproducts and mechanisms were inspected, and the effects of inorganic ions (NO3-, NO2-) and fulvic acid (FA) were discussed. The results showed that CN-2 could be transformed in water under the irradiation. NO3- and NO2- promoted the photoconversion of CN-2 owing to ·OH generated by the photolysis of NO3- and NO2-; FA at a lower concentration promoted the photoconversion, but it had an inhibition effect at a higher concentration. It was demonstrated that the acidic conditions promoted the photoconversion of CN-2 by the active groups such as superoxide radical anion, hydrogen peroxide and hydroxyl radical produced in the system. Eight photoproducts of CN-2 were characterized by the GC-MS method and the possible photoconversion mechanisms were proposed accordingly.

The photoconversion of gamma-hexachlorocyclohexane under UV irradiation in water, snow and ice.

The photochemistry of organic pollutants has received increasing attention in ice and snow. In this work, the photoconversion of gamma-hexachlorocyclohexane (γ-HCH) under UV irradiation was investigated in water, snow and ice. The photoconversion rate, products and mechanisms were inspected, and the effect of inorganic ions (NO2(-), NO3(-), HCO3(-) and Fe(2+)) was discussed. The results showed that γ-HCH could be photoconverted in water, snow and ice, with the photoconversion rate being fastest in snow, and slowest in ice. All photoconversion could be described by the first-order kinetics model. In water, snow and ice, the common photoproducts of γ-HCH were alpha-hexachlorocyclohexane (α-HCH) and pentachlorocyclohexene. α-HCH was generated by a change in the bonding of a chlorine atom in γ-HCH; pentachlorocyclohexene was generated by the removal of a molecule of chlorine hydride from a molecule of γ-HCH. Different concentrations of NO2(-), NO3(-) and HCO3(-) all inhibited the photoconversion of γ-HCH, and the inhibition effect decreased with increasing concentrations of NO2(-) and NO3(-), but increased with the increasing concentrations of HCO3(-). Different concentrations of Fe(2+) promoted the photoconversion of γ-HCH in water and ice, but had little effect in snow.

Hydroxyl radical dominated ibuprofen degradation by UV/percarbonate process: Response surface methodology optimization, toxicity, and cost evaluation.

Ibuprofen (IBP) is a typical nonsteroidal anti-inflammatory drug with a wide range of applications, large dosages, and environmental durability. Therefore, ultraviolet-activated sodium percarbonate (UV/SPC) technology was developed for IBP degradation. The results showed that IBP could be efficiently removed using UV/SPC. The IBP degradation was enhanced with prolonged UV irradiation time, with the decreasing IBP concentration and the increasing SPC dosage. The UV/SPC degradation of IBP was highly adaptable to pH ranging from 4.05 to 8.03. The degradation rate of IBP reached 100% within 30 min. The optimal experimental conditions for IBP degradation were further optimized using response surface methodology. IBP degradation rate reached 97.3% under the optimal experimental conditions: 5 µM of IBP, 40 µM of SPC, 7.60 pH, and UV irradiation for 20 min. Humic acid, fulvic acid, inorganic anions, and natural water matrix inhibited the IBP degradation to varying degrees. Scavenging experiments of reactive oxygen species indicated that hydroxyl radical played a major role in the UV/SPC degradation of IBP, while carbonate radical played a minor role. Six IBP degradation intermediates were detected, and hydroxylation and decarboxylation were proposed as the primary degradation pathways. An acute toxicity test, based on the inhibition of luminescence in Vibrio fischeri, indicated that the toxicity of IBP during UV/SPC degradation decreased by 11%. An electrical energy per order value of 3.57 kWh m-3 indicated that the UV/SPC process was cost-effective in IBP decomposition. These results provide new insights into the degradation performance and mechanisms of the UV/SPC process, which can potentially be used for practical water treatment in the future.

Effects of saline-alkali stress on bacterial and fungal community diversity in Leymus chinensis rhizosphere soil.

The salinization of grassland in arid and semi-arid areas is a serious environmental issue in China. Halophytes show extreme salt tolerance and are grown in saline-alkaline environments. Their rhizosphere microorganisms contribute significantly to plant stress tolerance. To study bacterial and fungal community structure changes in Chinese ryegrass (Leymus chinensis) rhizosphere soil under salt and alkali stress, pot experiments were conducted with different salt and alkali stress intensities. High-throughput sequencing was conducted, and the microbial diversity, community structure, and driving factors were analyzed in rhizosphere soil. The salinization of grassland in arid and semi-arid areas is a serious environmental issue in China. Halophytes show extreme salt tolerance and grow in saline-alkaline environments. A total of 549 species of bacteria from 28 phyla and 250 species from 11 phyla of fungi were detected in the rhizosphere soil of Leymus chinensis with different saline-alkali gradients. Alpha diversity analysis along saline-alkali gradients showed that bacterial community richness and diversity were the highest in the moderate saline-alkali group (pH = 8.28, EC = 160.4 µS·cm-1), while fungi had high richness and diversity in the control group (pH = 7.35, EC = 134.5 µS·cm-1). The bacteriophyta Proteobacteria, Acidobacteria, Plantomycetes, and the eumycota Ascomycota, Basidiomycota, and Glomeromycota were found with relative abundances of more than 10%. Saline-alkali gradients had significant effects on the abundance of the bacterial and fungal groups in the rhizosphere. The distribution of bacterial colony structure was not significant at the species level (P > 0.05). However, there were significant differences in the distribution of fungal structure and considerable differences in the composition of fungal species among the moderate saline-alkali group, severe saline-alkali group, and control group (P < 0.05). Correlation analysis showed that the bacterial phylum Gemmatimonadetes had a highly significant positive correlation with pH and EC (P < 0. 01). Saline-alkali stress significantly inhibited the abundance of the bacteria Latescibacteria, Cyanobacteria, and Bacteroides, and the fungi Zoopagomycota, Mortierllomycota, and Cryptomycota (P < 0. 05). Compared with fungi, bacterial community composition was most closely correlated with soil salinization. This report provided new insights into the responses of relationships between rhizosphere soil microorganisms and salt and alkali tolerance of plants.

Scientometric analysis and scientific trends on microplastics research.

In recent years, the environmental pollution of microplastics has attracted much attention. To date, there have been a lot of researches on microplastics and a series of studies published. In this study, by bibliometric analysis method to evaluated the development and evolution on microplastics research trends and hot spots. A total of 2872 literature information was collected from the Web of Science (2004-2020), which was used for bibliometric visual analysis by CiteSpace. It was possible to see the contributing countries, institutions, authors, keywords, and future study directions in the microplastics sectors by looking at the visual representation of the results. (1) Since 2004, scientific advancements in this sector have advanced significantly, with a significant increase in speed since 2012. (2) China and the United States are the world's leading researchers in microplastics. (3) The study of microplastics was multidisciplinary, comprising researchers from the fields of ecology, chemistry, molecular biology, environmental science, and oceanography. (4) In recent years, researchers have concentrated their attention on the distribution and toxicity of microplastics in the environment, as well as their coupled pollution with heavy metal contaminants. In conclusion microplastics study in environmental science has become increasingly popular in recent years. Topics include dispersion, toxicity, and coupled pollution with heavy metal pollutants. Researchers in a wide range of fields are involved in microplastics research. Furthermore, policies and regulations about microplastics in global were summarized, and membrane technology has potential to remove microplastics from water. The above findings help to clearly grasp the content and development trend of microplastics research, point out the future research direction for scholars, and promote microplastics research and pollution prevention and control.

Photochemical degradation kinetics and mechanisms of norfloxacin and oxytetracycline.

The photochemical degradation of norfloxacin (NOR) and oxytetracycline (OTC) was investigated under ultraviolet (UV) irradiation. The results indicated that both NOR and OTC can be degraded, whereas the reaction rates decreased with increasing concentration of NOR and OTC. The degradation rates of NOR and OTC (5 µM) were 0.0256 min-1 and 0.0140 min-1. Acidic conditions inhibited the degradation of NOR; however, alkaline conditions promoted the degradation of NOR. Meanwhile, the degradation of OTC was promoted by alkaline conditions but hardly affected by acidic conditions. In real water, the degradation of NOR was slower than that in ultrapure water, whereas the degradation of OTC was faster in real water. NOR produced five degradation products, with pathways mainly comprising hydroxylation and defluorination. OTC produced three degradation products, with its degradation pathways mainly consisting of deep oxidation, dehydration, and secondary alcohol oxidation. During the UV photolysis process, the mineralization rates of NOR and OTC (5 µM) were 9.83% and 6.87% after 60-min irradiation. This work can provide a theoretical basis for understanding the migration and transformation behavior of antibiotics in the water environment.

Photochemical degradation of ß-hexachlorocyclohexane in snow and ice.

Hexachlorocyclohexane (HCH), a typical organochloride pesticide, is one of the persistent organic pollutants. Despite the ban on technical grade HCH, it has been continuously observed at a steady level in the environment. The photochemical degradation of ß-HCH in snow and ice under ultraviolet (UV) irradiation was investigated in this study. The effects of pH as well as common chemical components in snow on the degradation kinetics were investigated. In addition, the photodegradation products were determined and the reaction mechanism was hypothesized. The results showed that under UV irradiation, ß-HCH can be photolyzed in snow and ice, with the photochemical degradation process conforming to the first-order kinetic equation. Changing the pH and adding Fe2+ had minimal effect on the photochemical degradation kinetics, while the presence of acetone, NO2-, NO3- and Fe3+ significantly inhibited the process. The addition of hydrogen peroxide slightly inhibited the photochemical degradation of ß-HCH. Finally, the reaction rate, products and degradation mechanism of ß-HCH in snow were compared with those in the ice phase. The photochemical degradation rate of ß-HCH in snow was approximately 24 times faster than that in the ice phase. The photolysis product of ß-HCH in snow was α-HCH, produced by the isomerization of ß-HCH. However, in ice, in addition to α-HCH, pentachlorocyclohexene was produced by dechlorination. The results of this study are helpful in understanding the transformation of organochlorine pesticides in snow and ice, as well as in providing a theoretical basis for snow and ice pollution prevention and control.

Photodegradation of dissolved organic matter of chicken manure: Property changes and effects on Zn2+/Cu2+ binding property.

Untreated livestock manure contains high concentrations of dissolved organic matter (DOM), which can enter the environment through leaching and eluviation, showing an important impact on the environment. In this research, fresh chicken manure from a large-scale chicken farm was collected as the source of DOM. The infrared spectrum of the original DOM was characterized. TOC analysis, UV spectrum and 3D fluorescence spectrum were used to measure the properties of DOM before and after photodegradation. Infrared spectroscopy results show that chicken manure DOM may contain aliphatic and aromatic compounds, alcohols, phenols, polysaccharides and some protein substances; In three systems, the order of TOC removal rates of DOM was water + UV system (85%) > > water + simulated sunlight system (7.2%) > ice + simulated sunlight system (4.5%); Changes of UV spectra, fluorescence spectra, molecular weight distribution and pH value show that, in three systems, as the illumination time increased, photodegradation reduced pH value of the systems, aromaticity and humus contents of DOM, while increased the proportion of medium and/or small molecular weight components of DOM. The amounts of all these changes were proportional to DOM photodegradation rates in the system. The binding ability of DOM with Cu2+ and Zn2+ in water solution decreased significantly after the photodegradation.

Distribution and toxicity of polycyclic aromatic hydrocarbons during CaO-assisted hydrothermal carbonization of sewage sludge.

Hydrothermal carbonization (HTC) of sewage sludge (SS) with and without calcium oxide (CaO) introduction was conducted at 160-240 °C, and the yield and distribution of polycyclic aromatic hydrocarbons (PAHs) were evaluated for the first time. PAHs (2972.99 µg/kg) and toxic equivalent quantity (TEQ) (373.09 µg/kg) yields in SS decreased by 13.61% and 14.65%, respectively, after treatment at 160 °C and substantially increased as temperatures increased. More PAHs were distributed in the hydrochar than in the aqueous products. Hydrochar yields decreased linearly with temperature, thus increasing PAH concentration in hydrochar; 6221.98 µg/kg of PAHs in hydrocar at 240 °C exceeded agricultural use standard limits. PAH and TEQ yields at 200 °C decreased by 5.55-15.98% and 2.88-3.54%, respectively, when 3-9% CaO was added, which could be ascribed to CaO inhibition in the free radical reaction for PAH generation. Additionally, 6% CaO addition substantially weakened the acceleration effect of high temperatures on PAH formation; the decrease of PAH yield at 240 °C was 22.14%, which is higher than that at other temperatures. Consequently, the PAH concentration in hydrochar declined by 2.33-22.37%. PAH content in hydrochar obtained from CaO-assisted HTC of SS fell within agriculture use standard limit and exhibits potential for use as a soil conditioner. However, condition with a CaO amount of 15% would significantly increase TEQ yields. Considering both PAH and TEQ yields and the ecological risks of PAHs in hydrochar derived from HTC of SS, the appropriate reaction conditions were found to be 200 °C with 3-6% added CaO.

Assessment of major ions and trace elements in snow: A case study across northeastern China, 2017-2018.

A total of 60 snow samples from 16 sites across northeastern China were collected from December 2017 to March 2018. The snow samples were analyzed for pH value, major water-soluble ions (Cl-, NO3-, SO42-, Na+, NH4+, K+, Ca2+, and Mg2+), and trace elements (Mn, Cr, Cd, Ni, Cu, Zn, Pb, As, and Fe). The results indicated that snow was slightly alkaline (mean pH value 7.54); Ca2+ and SO42- were the major ions, contributing up to 33.87% and 22.72% of the major ions, respectively; Pb was the dominant element, contributing up to 62.84% of the trace elements. Both the concentration of major ions and trace elements peaked in the middle or later period of the entire snow season. Enrichment factor (EF) analysis indicated that ions (NO3-, NH4+, and Ca2+) and trace elements (Pb, As, Cu, and Zn) were severely enriched by anthropogenic activities. Compared with previous studies, which sampled snow from the high altitude and latitude regions, the concentrations of most of the ions and trace elements in this study were found to be 1-3 and 1-4 orders of magnitude higher, respectively, indicating a threat to human health.