Development and application of a multi-task oriented deep learning model for quantifying drivers of air pollutant variations: A case study in Taiyuan, China.

Quantitative assessment of the drivers behind the variation of six criteria pollutants, namely fine particulate matter (PM2.5), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter (PM10), and carbon monoxide (CO), in the warming climate will be critical for subsequent decision-making. Here, a novel hybrid model of multi-task oriented CNN-BiLSTM-Attention was proposed and performed in Taiyuan during 2015-2020 to synchronously and quickly quantify the impact of anthropogenic and meteorological factors on the six criteria pollutants variations. Empirical results revealed the residential and transportation sectors distinctly decreased SO2 by 25 % and 22 % and CO by 12 % and 10 %. Gradual downward trends for PM2.5, PM10, and NO2 were mainly ascribed to the stringent measures implemented in transportation and power sectors as part of the Blue Sky Defense War, which were further reinforced by the COVID-19 pandemic. Nevertheless, temperature-dependent adverse meteorological effects (27 %) and anthropogenic intervention (12 %) jointly increased O3 by 39 %. The O3-driven pollution events may be inevitable or even become more prominent under climate warming. The industrial (5 %) and transportation sectors (6 %) were mainly responsible for the anthropogenic-driven increase of O3 and precursor NO2, respectively. Synergistic reduction of precursors (VOCs and NOx) from industrial and transportation sectors requires coordination with climate actions to mitigate the temperature-dependent O3-driven pollution, thereby improving regional air quality. Meanwhile, the proposed model is expected to be applied flexibly in various regions to quantify the drivers of the pollutant variations in a warming climate, with the potential to offer valuable insights for improving regional air quality in near future.

Unveiling the inhibition of chlortetracycline photodegradation and the increase of toxicity when coexisting with silver nanoparticles.

Silver nanoparticles (AgNPs) and antibiotics inevitably co-exist in water environment. Nonetheless, little is known regarding the interactions between AgNPs and antibiotics or the effects of AgNPs on environmental behavior of antibiotics, particularly on sunlight-driven transformation. In the present work, we found that AgNPs obviously inhibit the photochemical decay of chlortetracycline (CTC), and CTC boosts the dissolution of AgNPs. With the help of electron paramagnetic resonance (EPR) and quenching experiment, we ascertained that these results originated from the competition between AgNPs against CTC for capturing 1O2 generated from CTC photosensitization. 1O2 reacting with CTC contributed mostly to CTC photodegradation, while 1O2 as well reacting with AgNPs leads to release of Ag+. When compared to reaction of 1O2 with CTC, 1O2 is prone to react with AgNPs, based on lower Gibbs free energy of AgNPs reacting with 1O2. Therefore, upon CTC co-existing with AgNPs, the release of Ag+ was accelerated and the photodegradation of CTC was inhibited obviously. Furthermore, the accelerated release of Ag+ significantly increased their toxicity toward E. coli cells under simulate sunlight irradiation. Overall, the findings demonstrate how AgNPs interact with CTC and how these interactions affect the environmental behaviors of CTC or AgNPs, allowing more accurate assessments of the risk to ecosystems posed by AgNPs coexisting with antibiotics.

Unveil the mechanism of photosensitized fluoroquinolones enhancing chlortetracycline photodegradation under simulated sunlight: Batch experiments and DFT calculation.

Fluoroquinolones (FQs), as the most commonly used antibiotics, are ubiquitous in the aquatic environment. The FQs' self-sensitization process could generate reactive oxygen species (ROS), which could react with other coexisting organic pollutants, impacting their transformation behaviors. However, the FQs' influences and mechanisms on the photochemical transformation of coexisting antibiotics are not yet revealed. In this study, we found ofloxacin (OFL) and norfloxacin (NOR), the two common FQs, can obviously accelerate chlortetracycline (CTC) photodegradation. In the presence of OFL and NOR (i.e., 10 µM), CTC photodegradation rate constants increased by 181.1% and 82.9%, respectively. With the help of electron paramagnetic resonance (EPR) and quenching experiments, this enhancement was attributed to aromatic ketone structure in FQs, which absorbed photons to generate ROS (i.e., 3OFL*, 3NOR*,1O2, and •OH). Notably, 3OFL* or 3NOR* was dominantly contributed to the enhanced CTC photodegradation, with the contribution ratios of 79.9% and 77.3% in CTC indirect photodegradation, respectively. Compared to CTC direct photodegradation, some new photodegradation products were detected in FQs solution, suggesting that 3OFL* or 3NOR* may oxide CTC through electron transfer. Moreover, the higher triple-excited state energy of OFL and NOR over DFT calculation implied that energy transfer from 3OFL* or 3NOR* to CTC was also theoretically feasible. Therefore, the presence of FQs could significantly accelerate the photodegradation of coexisting antibiotics mainly via electron or energy transfer of 3FQs*. The present study provided a new insight for accurately evaluating environmental behaviors and risks when multiple antibiotics coexist.

Importance of Chain Length in Propagation Reaction on •OH Formation during Ozonation of Wastewater Effluent.

During the ozonation of wastewater, hydroxyl radicals (•OH) induced by the reactions of ozone (O3) with effluent organic matters (EfOMs) play an essential role in degrading ozone-refractory micropollutants. The •OH yield provides the absolute •OH formation during ozonation. However, the conventional "tert-Butanol (t-BuOH) assay" cannot accurately determine the •OH yield since the propagation reactions are inhibited, and there have been few studies on •OH production induced by EfOM fractions during ozonation. Alternatively, a "competitive method", which added trace amounts of the •OH probe compound to compete with the water matrix and took initiation reactions and propagation reactions into account, was used to determine the actual •OH yields (Φ) compared with that obtained by the "t-BuOH assay" (φ). The Φ were significantly higher than φ, indicating that the propagation reactions played important roles in •OH formation. The chain propagation reactions facilitation of EfOMs and fractions can be expressed by the chain length (n). The study found significant differences in Φ for EfOMs and fractions, precisely because they have different n. The actual •OH yield can be calculated by n and φ as Φ = φ (1 + n)/(nφ + 1), which can be used to accurately predict the removal of micropollutants during ozonation of wastewater.

Photoaging processes of polyvinyl chloride microplastics enhance the adsorption of tetracycline and facilitate the formation of antibiotic resistance.

Microplastics (MPs), antibiotics and microorganism ubiquitously coexist in aquatic environments. MPs inevitably undergo photoaging processes in aquatic environments, affecting the interactions between MPs and antibiotics and the antibiotic resistance of microorganism. In this study, the impact of photoaging processes of MPs on their adsorption behavior of tetracycline (TC) and related formation of antibiotic resistance were investigated. It was found that the photoaging processes significantly increased the adsorption capacity of TC onto MPs, with the Qe increasing from 0.387 to 0.507 mg/g at 288 K and from 0.507 to 0.688 mg/g at 308 K. The site energy distribution (SED) analysis further confirmed that the enhanced adsorption capacity was attributed to more high-energy adsorption sites acquired from MPs photoaging processes. Moreover, the enhanced adsorption of TC further facilitated the formation of seven antibiotic resistance genes (i.e., tetA, tetB, tetC, tetD, tetE, tetG, tetK) when MPs adsorbed with TC was covered by biofilm. This study helps comprehensively understand the environmental behaviors of co-existing MPs, antibiotics and microorganisms, providing a theoretical basis for evaluating and mitigating their coexistence risks.

Effect of allelochemicals sustained-release microspheres on the ingestion, incorporation, and digestion abilities of Daphnia magna Straus.

Allelochemicals sustained-release microspheres (ACs-SMs) exhibited great inhibition effect on algae, however, few studies have focused on ACs-SMs toxicity on invertebrate. In this study, the effects of single high-concentration ACs (15 mg/L, SH-ACs), repeated low-concentration ACs (3 × 5 mg/L, RL-ACs) and ACs-SMs containing 15 mg/L ACs exposure on the ingestion, incorporation, and digestion of Daphnia magna Straus (DS) were investigated by stable isotope 15N labeling method. Meanwhile, the diversity and abundance of microflora in DS guts were determined by 16S rRNA genes and cloning methods. The results showed that SH-ACs exposure caused 50% and 33.3% death rates for newborn and adult DS, while RL-ACs exposure caused 10% death rate for newborn DS and no obvious effect on the activity of adult DS. And ACs-SMs exposure did not diminish the motility of both newborn and adult DS, indicating the lower acute toxicity of ACs-SMs. Furthermore, SH-ACs inhibited the ingestion (-6.45%), incorporation (-47.1%) and digestion (-53.8%) abilities of DS and reduced the microbial abundance (-27.7%) in DS guts. Compared with SH-ACs, RL-ACs showed relatively low impact on the ingestion (-3.23%), incorporation (-5.89%) and digestion (-23.9%) abilities of DS. Interestingly, ACs-SMs enhanced the ingestion (+9.68%), incorporation (+52.9%) and digestion (+51.3%) abilities of DS and increased the microbial abundance (+10.7%) in DS guts. Overall ACs and ACs-SMs reduced the diversity of microflora in DS guts. In conclusion, ACs-SMs can release ACs sustainably and prolong the sustained release time, which not only effectively reduce the toxicity of ACs, but also had positive effects on DS.

A new and systematic review on the efficiency and mechanism of different techniques for OPFRs removal from aqueous environments.

Organic phosphorus flame retardants (OPFRs), as a new type of emerging contaminant, have drawn great attention over the last few years, due to their wide distribution in aquatic environments and potential toxicities to humans and living beings. Various treatment methods have been reported to remove OPFRs from water or wastewater. In this review, the performances and mechanisms for OPFRs removal with different methods including adsorption, oxidation, reduction and biological techniques are overviewed and discussed. Each technique possesses its advantage and limitation, which is compared in the paper. The degradation pathways of typical OPFRs pollutants, such as Cl-OPFRs, alkyl OPFRs and aryl OPFRs, are also reviewed and compared. The degradation of those OPFRs depends heavily upon their structures and properties. Furthermore, the implications and future perspectives in such area are discussed. The review may help identify the research priorities for OPFRs remediation and understand the fate of OPFRs during the treatment processes.

Inhibitory effects of antioxidant moieties in humic substances on phototransformation of chlortetracycline mediated by the algae extracellular organic matter.

In algae rich waters, sunlight-driven transformation of antibiotics could be accelerated via sensitization by algae extracellular organic matter (EOM), and this photosensitization process will be affected by coexisting humic substances. In this study, we explored the effect and mechanism of humic substances on photodegradation of chlortetracycline (CTC) mediated by EOM. We found that humic substances exhibited a marked inhibitory effect on the EOM-mediated photodegradation of CTC. Given that humic substances exhibited little effects on the EOM-mediated formation of triplet state species, the quenching effect of humic substances on reactive species was excluded. The inhibitory effect of humic substances was mainly attributed to the back reduction of CTC oxidation intermediates by the antioxidant moieties in humic substances. The ozone oxidation treatment for humic substances was applied to destroy antioxidant moieties. After ozonation, the inhibitory effects of humic substances were greatly decreased, confirming the dominant role of antioxidant moieties in humic substances, which inhibited CTC photodegradation mediated by EOM via reducing oxidation intermediates of CTC. This back reduction was further verified to be exergonic via reactive Gibbs free energy, indicating the back reduction by humic substances of CTC oxidation intermediates could occur spontaneously. The present study will be helpful for predicting the fate and risk of CTC in algae rich water environments, and is of great significance for the study of phototransformation of other antibiotics.

A review: Application of allelochemicals in water ecological restoration--algal inhibition.

Problems caused by harmful algal blooms have attracted worldwide attention due to their severe harm to aquatic ecosystems, prompting researchers to study applicable measures to inhibit the growth of algae. Allelochemicals, as secondary metabolites secreted by plants, have excellent biocompatibility, biodegradability, obvious algal inhibiting effect and little ecological harm, and have promising application prospect in the field of water ecological restoration. This review summarized the research progress of allelochemicals, including (i) definition, development, and classification, (ii) influencing factors and mechanism of algal inhibition, (iii) the preparation methods of algal inhibitors based on allelochemicals. The future research directions of allelochemicals sustained-released microspheres (SRMs) were also prospected. In the future, it is urgent to explore more efficient allelochemicals, to study the regulation mechanism of allelochemicals in natural water bodies, and to improve the preparation method of allelopathic algal suppressant. This paper proposed a feasible direction for the development of allelochemicals SRMs which exhibited certain guiding significance for their application in water ecological restoration.

Comparison of the oxidation of halogenated phenols in UV/PDS and UV/H2O2 advanced oxidation processes.

UV/peroxydisulfate (PDS) and UV/hydrogen peroxide (H2O2) can effectively degrade halophenols (HPs, e.g., 2,4-bromophenol and 2,4,6-trichlorophenol); meanwhile, information about the discrepancies in the related degradation kinetics and mechanisms of these two processes is limited. To gain this knowledge, the degradation of two typical HPs (i.e., bromophenols and chlorophenols) in UV/PDS and UV/H2O2 processes were investigated and compared. The results showed that the degradation rates of HPs with different substitution positions in the UV/PDS process were in the order of para-substituted HPs (i.e., 4-BP and 4-CP) > ortho-substituted HPs (i.e., 2-BP and 2-CP) > meta-substituted HPs (i.e., 3-BP and 3-CP), while in the UV/H2O2 process, these rates were in the order of para-substituted HPs > meta-substituted HPs > ortho-substituted HPs. These discrepancies were ascribed to the different reaction activities of SO4˙- and HO˙ with HPs, which were calculated based on the competition method. Further density functional theory (DFT) calculations suggested that SO4˙- reacts more readily with HPs via electron transfer than HO˙. In the presence of water matrices (such as Cl-, HCO3 - and natural organic matter (NOM)), the degradation of 2-BP in both UV/PDS and UV/H2O2 treatment processes was inhibited due to the scavenging of free radicals by these background substances. The degradation products and pathways further confirmed that SO4˙- is a strong one-electron oxidant that reacts with HPs mainly via electron transfer, while HO˙ reacts with HPs via electron transfer and hydroxyl addition.

Degradation behaviors of Isopropylphenazone and Aminopyrine and their genetic toxicity variations during UV/chloramine treatment.

Combination of ultraviolet and chloramine (i.e., UV/chloramine) treatment has been attracting increasingly attention in recent years due to its high efficiency in removing trace organic contaminants. This study investigated the degradation behaviors of two pyrazolone pharmaceuticals (i.e., Isopropyl phenazone (PRP) and Aminopyrine (AMP)) and their genetic toxicity variations during UV/chloramine treatment. The results showed that chloramine could hardly degrade PRP and AMP, while UV/chloramine greatly increased the observed first-order rate constant (kobs) of PRP and AMP degradation. The quenching and probe experiments illustrated that the reactive chlorine species (RCS) contributed dominantly to PRP removal, and hydroxyl radical (HO•) was the major contributor to the degradation of AMP, while the reactive amine radicals (RNS) could hardly degrade them. The overall degradation rates of PRP and AMP decreased as pH increased from 6.5 to 10. The kobs of PRP and AMP increased along with NH2Cl dosage increasing and reached a plateau at higher concentrations (0.2-0.5 mM). The present background carbonate (HCO3-, 1-10 mM), chloride (Cl-, 1-10 mM) and natural organic matter (NOM, 5-10 mg-C L-1) exhibited inhibition impacts on PRP and AMP degradation. In addition, the intermediates/products of PRP and AMP were identified and their general degradation pathways were proposed to be hydroxylation, deacetylation, and dephenylization. Specifically, Cl-substitution was inferred during PRP degradation, while demethylation in tertiary amine group was only observed in AMP degradation. These mechanisms including the main reactive sites of PRP and AMP were further confirmed by the frontier orbitals calculation. Moreover, the results of the genetic toxicity according to the micronucleus test of Viciafaba root tip indicated that UV/chloramine treatment could partially reduce the genetic toxicity of PRP and AMP.

Dissolved black carbon enhanced the aquatic photo-transformation of chlortetracycline via triplet excited-state species: The role of chemical composition.

Dissolved black carbon (DBC), widely distributed in the aquatic environments, can accelerate sunlight-driven photo-transformation of micropollutants, however the photosensitization mechanisms are not clear. Herein, the DBC was extracted from bamboo biochar and fractionated by molecular weight (i.e. <10 k, <3 k, and <1 k Da). The effects of DBC on chlortetracycline (CTC) photolysis behaviors, and the role of chemical composition (i.e., molecular weight and chemical structure) in DBC-mediated photo-transformation were investigated. The results showed that DBC could accelerate CTC photodegradation significantly. At low DBC concentrations (<6.0 mg C/L), the photodegradation rate constant of CTC increased from 0.0299 to 0.0416 min-1 with the increasing DBC concentration. Via quenching experiment, the triplet excited-state of DBC was identified as the dominant reactive intermediate with >90% contribution to total CTC photodegradation. In addition, it was found that the photosensitive efficiency of DBC increased as the molecular weight decreased, and the stronger photosensitization ability exhibited in DBC with low-molecular weight was potentially attributed to its higher content of carbonyl compounds. The observed photosensitive efficiency of DBC sharply decreased after reduction by NaBH4, further confirming the key role of carbonyl compounds in the photosensitization process. Moreover, based on the result of photoproducts, the amidogen in CTC was verified to be susceptible to react with 3DBC*.

Photosensitization mechanism of algogenic extracellular organic matters (EOMs) in the photo-transformation of chlortetracycline: Role of chemical constituents and structure.

The ubiquitous algogenic extracellular organic matters (EOMs) could enhance solar photodegradation of antibiotics such as Chlortetracycline (CTC), however, the role of chemical constituents and structure in their photosensitizing process was not clear. In this paper, EOMs were extracted from chlorella vulgaris (CV-EOMs), scenedesmus meyen (SM-EOMs) and microcystis aeruginosa (MA-EOMs) to explore their photosensitive efficiencies and mechanisms. All of the EOMs showed higher photosensitive efficiencies than natural organic matter (NOM). The quenching assays and competitive kinetics experiments confirmed the dominant role of 3EOMs* in accelerating CTC photodegradation. The quantum yield coefficients of 3EOMs* (fTMP) of CV-EOMs, SM-EOMs, MA-EOMs, NOM were 139.89 ±â€¯5.46, 125.35 ±â€¯4.69, 91.76 ±â€¯3.53, and 72.84 ±â€¯4.45 L/(mol-photon), respectively. Specific chemical constituents and structure of EOMs were characterized by nuclear magnetic resonance (NMR), fourier transform ion cyclotron resonance mass spectrometry (FT-CIR-MS) and X-ray photoelectron spectroscopy (XPS). The results showed the positive linear correlation of fTMP with content of carbonyl groups in EOMs. In addition, reduction of carbonyl groups in EOMs by NaBH4 significantly decreased CTC photodegradation rate. Density Functional Theory (DFT) calculation suggested the susceptible excitation of carbonyl groups in EOMs under solar light was ascribed to the lowest required energy of electronic transition from HOMO to LUMO (assigned as n-π* transition). The energy of triplet excited-states benzophenone, p-methoxy acetophenone and acetophenone (the EOMs model compounds) was calculated to be 284.92, 288.85 and 265.50 kJ/mol, which were higher than that of CTC (i.e., 217.46 kJ/mol), indicating the energy transfer from excited triplet state to excited triplet state CTC was possible. This study provided mechanism insights into photosensitization effects of allogenic EOMs on photochemical fate of pollutants in aqueous environment.

Retraction Note to: SOX2 oncogenes amplified and operate to activate AKT signalling in gastric cancer and predict immunotherapy responsiveness.

The Editor-in-Chief is retracting this article (Tian et al 2014) due to concerns regarding peer review, authorship and originality of the article.

Chlorella vulgaris enhance the photodegradation of chlortetracycline in aqueous solution via extracellular organic matters (EOMs): Role of triplet state EOMs.

Algae, which are ubiquitous in surface waters (e.g., lakes, ponds, wetlands) may play an important role in sunlight-driven transformation of compounds. This study is to investigate the role of algae (Chlorella Vulgaris) in chlortetracycline (CTC) photolysis and explore the photosensitive mechanism. The algae were found to significantly accelerate the photodegradation rate of CTC and extracellular organic matters (EOMs) were confirmed to be the major active substances. Triplet state EOMs (3EOMs*) were verified to be the dominant reactive species with 93% contribution to the indirect photodegradation rate of CTC, while ·OH and 1O2 contributed minor (7%). The steady-state concentration of 3EOMs* was determined by probe compounds (2,4,6-trimethylphenol) to be 3.50 × 10-14-1.88 × 10-13 M with the increase of EOMs from 2.0 to 8.0 mg L-1. The rate constant for reaction of 3EOMs* with CTC was calculated to be 3.17 × 109 M-1s-1. 3EOMs* were found to react with CTC mainly via electron transfer, on basis of susceptible reaction of 3EOMs* with the hydroxyl and amidogen groups in CTC. In addition, the energy transfer of 3EOMs* to CTC was possible according to the higher energy of 3EOMs* than that of triplet CTC.

Spatial distribution of and seasonal variations in endosulfan concentrations in soil, air, and biota around a contaminated site.

Soil, air, tree bark, rice, wheat, invertebrates, and chicken tissues around a typical endosulfan-contaminated site were analyzed in each season in each of two years. The total endosulfan (the sum of α-, ß-endosulfan and endosulfan sulfate) were significantly different in soil and air samples collected in the four seasons (P < 0.01) and the mean concentrations were 6.53 ng/g dry weight (d.w.) and 2.40 ng/m3, respectively, in autumn, 3.32 ng/g d.w. and 2.48 ng/m3, respectively, in winter, 2.10 ng/g d.w. and 0.93 ng/m3, respectively, in spring, and 1.03 ng/g d.w. and 0.83 ng/m3, respectively, in summer. The total endosulfan concentrations in tree bark, rice, wheat, and invertebrates were 23.0-278 (mean 95.5) ng/g d.w., 7.36-35.5 (mean 17.4) ng/g d.w., 34.3-158 (mean 83.1) ng/g d.w., and 401-4354 (mean 2125) ng/g lipid weight, respectively. The total endosulfan concentrations in the chicken gizzard, heart, liver, and meat samples were 552, 212, 699, and 221 ng/g lipid weight, respectively. The endosulfan concentrations in soil, air, and biota around the site were strongly influenced by endosulfan emissions from the site, and the concentrations had decreased to half the initial concentrations six months after endosulfan production stopped. The invertebrate and chicken bioconcentration and biomagnification factors indicated that endosulfan accumulated in the invertebrates and chicken tissues was slightly biomagnified by chickens.

Organochlorine pesticides in soil, air, and vegetation at and around a contaminated site in southwestern China: Concentration, transmission, and risk evaluation.

Remediation and management of contaminated sites have become a prevalent problem under the current situation in China. The present study was conducted to investigate the concentration, transmission, and health risk of organochlorine pesticides (OCPs) in soil, air, and vegetation at and around a typical pesticide-contaminated site located in southwestern China. Exchange flux between soil and air was calculated to investigate the transmission of OCPs. Hexachlorocyclohexane (ΣHCHs, top soil: 19.1 mg/kg d.w., air: 52.3 ng/m3, vegetation: 0.17 mg/kg d.w.) and dichlorodiphenyltrichloroethane (ΣDDTs, top soil: 200 mg/kg d.w., air: 130 ng/m3, vegetation: 0.78 mg/kg d.w.) were the dominant pollutants at the contaminated site. Around the site, the soil, air, and vegetation samples had higher OCP concentrations than those in the normal areas, which were found to be dominated by ΣHCHs (top soil: 129 ng/g d.w., air: 5.09 ng/m3, vegetation: 81.8 ng/g d.w.) and ΣDDTs (top soil: 360 ng/g, air: 7.47 ng/m3, vegetation: 189 ng/g d.w.). The fugacity fractions of OCPs (>0.7) showed a net volatilization from soil into air, indicating that soil is an obvious pollution source for the atmosphere, especially at the site. Through human health risk evaluation, serious carcinogenic risk (CRn) and hazardous index (HIn) were found at the site (CRn: 7.4 × 10-6-1.04 × 10-4, HIn: 0.02 to 8.97) and the nearby areas (CRn: 3.37 × 10-6 for adults and 1.68 × 10-6 for children on average).

Spatial distribution, transport dynamics, and health risks of endosulfan at a contaminated site.

We analyzed concentrations, distribution characteristics, and health risks of endosulfan (α and ß isomers, and endosulfan sulfate) in soils (top soils and soil profiles) and air, at and around a typical endosulfan production site in Jiangsu, China. The air-soil surface exchange flux is calculated to investigate transport dynamics of endosulfan. Concentrations at the production site ranged from 0.01 to 114 mg/kg d.w. in soil and 4.81-289 ng/m(3) in air, with very high concentrations occurring at the location of endosulfan emulsion workshop. In the surrounding area, endosulfan was detected in all samples, with concentrations ranging from 1.37-415 ng/g d.w. in soil and 0.89-10.4 ng/m(3) in air. In the contaminated site, endosulfan concentrations fluctuated with depth in the upper soil layers, then decreased below 120 cm. Soil and air within a distance of 2.0 km appear to be affected by endosulfan originating from the site. Even the health risk at the location of the endosulfan emulsifiable solution workshop was over seven times the acceptable value, the risk to nearby adults and children was low.

Preparation of Zinc Oxide-Starch Nanocomposite and Its Application on Coating.

A new production method of zinc oxide (ZnO)-starch nanocomposite was invented in this study. Starch was dissolved in zinc chloride (ZnCl2) solution (65 wt%) at 80 °C. Then, ZnO-starch nanocomposite was achieved when the pH of the solution was adjusted to 8.4 by NaOH solution (15 wt%). ZnO nanoparticles were also obtained when the generated ZnO-starch nanocomposite was calcined at 575 °C. The properties of ZnO-starch nanocomposite and ZnO nanoparticle were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the sizes of ZnO-starch composite and ZnO particle were 40-60 nm. UV blocking effect was observed from both ZnO-starch nanocomposite and ZnO nanoparticle. The ZnO-starch nanocomposite was used to directly coat the surface of plain paper with a laboratory paper coater. The surface strength and smoothness of paper were improved by the coating of ZnO-starch nanocomposite. The antibacterial property was also identified from the coated paper.

Seasonal variations in concentrations, distributions, and air-soil exchange fluxes of dioxin-like polychlorinated biphenyls in Shanghai, China.

Dioxin-like polychlorinated biphenyl (dl-PCB) concentrations in ambient air and soil in Shanghai, China, were measured to allow seasonal and spatial differences in the dl-PCB concentrations, profiles, distributions, fugacity fractions, and air-soil fluxes to be determined. The toxic equivalent (TEQ) DL-PCB concentrations in the air were higher in summer (mean 9.46 fg m(-3), range 1.32-26.3 fg m(-3)) than in winter (mean 4.57 fg m(-3), range 1.55-10.9 fg m(-3)). The DL-PCB concentrations in air were different in different areas, and the concentrations decreased in the order industrial areas > commercial and residential areas > suburban areas > rural area. The mean DL-PCB concentration in soil was 0.25 pg TEQ g(-1) dry weight (dw) and the range was 0.05-0.90 pg TEQ g(-1) dw. The highest DL-PCB concentration in soil was found in a sample from a commercial/residential area. The DL-PCB fluxes were negative (-216 pg m(-2) h(-1) in summer and -41.1 pg m(-2) h(-1) in winter), and the fugacity fractions were below 0.5, indicating that dl-PCBs in Shanghai are deposited from the air to the soil in all seasons. The net fluxes were higher in summer than in winter, and the deposition fluxes were higher in industrial areas than in other areas in both summer and winter.