Treatment on thiodicarb in pesticide wastewater with walnut shells-derived carbon and its improved modification: adsorption behavior.

The health problems caused by water pollution cannot be ignored, and the contribution of pesticides to water pollution has also become increasingly unignorable. The modified semi-coke as an adsorbent for reducing pesticide pollution to water was obtained from activated semi-coke which was modified by nitric acid (HNO3). The semi-coke was obtained by carbonization using 60 mesh walnut shell powder. After acid-base deashing, the semi-coke is dipped into zinc chloride (ZnCl2) solution to obtain activated semi-coke. Through BET analysis, the specific surface areas of semi-coke, activated semi-coke and modified semi-coke were 26.8 m2/g, 243.9 m2/g, and 339.6 m2/g respectively. An extremely high adsorption capacity of the adsorbents which is used to treat wastewater was achieved. The optimum adsorption conditions for modified semi-coke on thiodicarb solution were 30 mg/L of thiodicarb solution, adsorbent dosage of 0.01 g, adsorption temperature of 25 °C and adsorption time of 90 min. The optimum adsorption amount of 29.54 mg/gsor was achieved (sor is the abbreviation for sorbent). Moreover, through kinetics study, the result manifests that the modified semi-coke adsorption process is more fitted to the second-order kinetic model. This study provided a research implication theoretically for the treatment of pesticides in water.

Distribution and sources of PM2.5-bound free silica in the atmosphere of hyper-arid regions in Hotan, North-West China.

The composition of atmospheric fine particulate matter (PM2.5) is complex and exhibits strong regional differences. Free silica (α-SiO2) in atmospheric particulate matter is carcinogenic and is an important component of respirable particulate matter in urban areas. Measurements determined that the concentration of silicon dioxide (α-SiO2) in PM2.5 in the urban area of Hotan City, China, was 8.02 µg·m-3 during the dust period and exceeded 1.77 µg·m-3 during the non-dust period. The proportion of α-SiO2 in PM2.5 was 8.07% during the dust period and 2.25% during the non-dust period. Atmospheric visibility during the dust period was mainly influenced by the content of atmospheric floating dust. Analysis of α-SiO2 pollution sources during the dust period showed that the air masses containing sand and dust originated from the desert hinterland. Following passage through oasis areas, the air mass was effectively reduced in the concentration of α-SiO2 in PM2.5. During the dusty period, α-SiO2 and PM2.5 originated from the same source in Hotan City. Moreover, wind speed was the main influencing factor for the α-SiO2 concentration. During the non-dust period, α-SiO2 and PM2.5 were not from the same source of pollution.

Humidity and PM2.5 composition determine atmospheric light extinction in the arid region of northwest China.

Atmospheric visibility can directly reflect the air quality. In this study, we measured water-soluble ions (WSIs), organic and element carbon (OC and EC) in PM2.5 from September 2017 to August 2018 in Urumqi, NW China. The results show that SO42-, NO3- and NH4+ were the major WSIs, together accounting for 7.32%-84.12% of PM2.5 mass. Total carbon (TC=OC+EC) accounted for 12.12% of PM2.5 mass on average. And OC/EC > 2 indicated the formation of secondary organic carbon (SOC). The levels of SO42-, NO3- and NH4+ in low visibility days were much higher than those in high visibility days. Relative humidity (RH) played a key role in affecting visibility. The extinction coefficient (bext) that estimated via Koschmieder formula with visibility was the highest in winter (1441.05 ± 739.95 Mm-1), and the lowest in summer (128.58 ± 58.00 Mm-1). The bext that estimated via IMPROVE formula with PM2.5 chemical component was mainly contributed by (NH4)2SO4 and NH4NO3. The bext values calculated by both approaches presented a good correlation with each other (R2 = 0.87). Multiple linear regression (MLR) method was further employed to reconstruct the empirical regression model of visibility as a function of PM2.5 chemical components, NO2 and RH. The results of source apportionment by Positive Matrix Factorization (PMF) model showed that residential coal combustion and vehicle emissions were the major sources of bext.

In situ ultrasound-assisted ion exchange synthesis of sphere-like AgClxBr1-x composites with enhanced photocatalytic activity and stability.

AgClxBr1-x composites with different halogen molar ratios (Cl/Br) were prepared by a facile ultrasound-assisted ion-exchange method. The formation of close contact between AgCl and AgBr facilitated the transportation of photoexcited charge carriers and contributed to the enhanced visible-light-driven photocatalytic degradation of different kinds of antibiotics. The AgClxBr1-x composites had a sphere-like morphology and tunable band gaps from 2.95 to 2.57 eV depending on Cl/Br mole ratios. Besides, the AgClxBr1-x composite was optimized by varying halogen mole ratios (Cl/Br) to achieve the highest photocatalytic activity. Results indicated that AgCl0.75Br0.25 showed the best photocatalytic degradation performance, which was about 2.36 and 2.78 times that of the single AgCl towards ciprofloxacin (CIP) and metronidazole (MNZ) degradation, respectively. Meanwhile, a possible photocatalytic degradation mechanism was discussed, and results indicated that the holes (h+) and •OH were the dominant active species in the AgCl0.75Br0.25 system.

[Effect of Liquid Water Content of Particles and Acidity of Particulate Matter on the Formation of Secondary Inorganic Components in Xinjiang Petrochemical Industrial Area].

Secondary species are dominant components of PM2.5 in Dushanzi, Xinjiang. It is crucial to investigate the conversion process of secondary components in the atmosphere for regional air pollution control. The water-soluble components were analyzed for samples collected from Dushanzi District of Xinjiang from September 2015 to July 2016. The results showed that the total water-soluble ions (TWSIs) showed a seasonal variation consistent with PM2.5, and the seasonal variation of the ions was in the order-winter (67.86 µg·m-3) > autumn (13.77 µg·m-3) > spring (10.09 µg·m-3) > summer (4.85 µg·m-3); secondary ions (NH4+, SO42-, and NO3-)-accounting for 98% of TWSIs in winter. The results of the aerosol thermodynamic model (E-AIM) that explores the particle liquid water and acidity in Dushanzi District showed that the particles in Dushanzi are acidic with an annual in-situ pH of 0.81, and the pH value of the winter samples was the highest (2.93). The seasonal variation of particles in water was of the order: winter (331.32 µg·m-3) > autumn (5.91 µg·m-3) > spring (5.46 µg·m-3) > summer (1.62 µg·m-3). The annual average nitrogen oxidation rate and sulfur oxidation rate were 0.13 and 0.47, respectively, indicating a secondary conversion of regional pollutants. Further analysis showed that the concentration of sulfate in the particle phase was significantly affected by liquid water content of particles and in-situ pH. The formation of nitrate was mainly caused by heterogeneous reactions under high water content of particle.

Distribution, sources, risks, and vitro DNA oxidative damage of PM2.5-bound atmospheric polycyclic aromatic hydrocarbons in Urumqi, NW China.

Research has focused on the impacts of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere due to their potential carcinogenicity. In this study, we investigated the seasonal variation, sources, incremental lifetime cancer risks (ILCRS), and vitro DNA oxidative damage of PAHs in Urumqi in NW China. A total of 72 atmospheric samples from Urumqi were collected over a year (September 2017-September 2018) and were analyzed for 16 PAHs that are specifically prioritized by the U.S Environmental Protection Agency (U·S EPA). The highest PAHs concentrations were in winter (1032.66 ng m-3) and lowest in spring (146.00 ng m-3). Middle molecular weight PAHs with four rings were the most abundant species (45.28-61.19% of the total). The results of the diagnostic ratio and positive matrix factorization inferred that the major sources of atmospheric PAHs in Urumqi were biomass burning, coking, and petrogenic sources (52.9%), traffic (30.1%), coal combustion (8.9%), and the plastics recycling industry (8.1%). ILCRS assessment and Monte Carlo simulations suggested that for all age groups PAHs cancer risks were mainly associated with ingestion and dermal contact and inhalation was negligible. The plasmid scission assay results showed a positive dose-response relationship between PAHs concentrations and DNA damage rates, demonstrating that toxic PAHs was the primary cause for PM2.5-induced DNA damage in the air of Urumqi.

One-pot sonochemical synthesis of 3D flower-like hierarchical AgCl microsphere with enhanced photocatalytic activity.

A highly uniform 3D flower-like hierarchical AgCl microsphere was prepared by sonochemical method with the existence of ß-dextrin. The 3D flower-like hierarchical structure can be ascribed to the existence of ß-dextrin, which provides nucleation sites for the growth of nanosheets because of the strong interaction between ß-dextrin and Ag+. The 3D flower-like hierarchical AgCl microspheres were assembled by numerous interleaving nanosheet petals with small thickness. Benefiting from the unique structural features, the as-prepared 3D flower-like hierarchical AgCl microsphere exhibited higher degradation efficiency with degrading 98.17% of methylene blue (MB) and 88.50% of tetracycline (TC) within 40 min, which were both remarkably higher than those of irregular AgCl under visible light irradiation. Besides, the photocatalytic degradation rate constant of 3D flower-like hierarchical AgCl microsphere (0.063 min-1) for MB was 3.94 times higher than that of irregular AgCl (0.016 min-1). Moreover, a possible mechanism for the formation and excellent photocatalytic performance of 3D flower-like hierarchical AgCl microsphere was also proposed.

Concentration characteristics, source apportionment, and oxidative damage of PM2.5-bound PAHs in petrochemical region in Xinjiang, NW China.

Polycyclic aromatic hydrocarbons (PAHs) are of considerable concern due to their potential as human carcinogens. Thus, determining the characteristics, potential source, and examining the oxidative capacity of PAHs to protect human health is essential. This study investigated the PM2.5-bound PAHs at Dushanzi, a large petrochemical region in Xinjiang as well as northwest China. A total of 33 PM2.5 samples with 13 PAHs, together with molecular tracers (levoglucosan, and element carbon), were analyzed during the non-heating and heating periods. The results showed that the PM2.5 concentrations were 70.22 ± 22.30 and 95.47 ± 61.73 µg/m3, while that of total PAHs were 4.07 ± 2.03 and 60.33 ± 30.80 ng/m3 in sampling period, respectively. The fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, and benzo[k]fluoranthene were the most abundant (top five) PAHs, accounting for 71.74 and 72.80% of total PAH mass during non-heating and heating periods. The BaP equivalent (BaPeq) concentration exceeded 1 ng/m3 as recommended by National Ambient Air Quality Standards during heating period. The diagnostic ratios and positive matrix factorization indicated that oil industry, biomass burning, coal combustion, and vehicle emissions are the primary sources. The coal combustion remarkably increased during heating period. The plasmid scission assay (PSA) results showed that higher DNA damage rate was observed during heating period. PAHs in PM2.5 such as Chr, BaP, and IcdP were found to have significantly positive correlations with the plasmid DNA damage rates. Additionally, the relationship among BaPeq and DNA damage rate suggested that synergistic reaction may modify the toxicity of PAHs.