Side-effects of organic and inorganic pollutants on soil nitrification and respiration

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Oxidation of antimony(Ⅲ) in soil by manganese(Ⅳ) oxide using X-ray absorption fine structure

The oxidation of antimony(III) in soils was studied using X-ray absorption fine structure(XAFS)spectra.An andosol soil sample and artificial soil samples(SiO_2 blended with iron(III) hydroxide and manganese(IV) oxide) were used herein.After adding antimony(III) oxide to all soil samples,the oxidation process was observed by recording the XAFS spectra of Sb K-edge,Fe Kedge,and Mn K-edge.The results indicated that manganese(IV) oxide played an important role in the oxidation of Sb(III);however iron(III) hydroxide was not directly related to the reaction.During a 2-hr continuous Sb K-edge X-ray absorption near edge structure(XANES) measurement with an interval of 1 min of one of the artificial soil samples(SiO_2+ MnO_2+ Sb_2O_3),a pseudo-first-order reaction was determined with an average estimated rate of 0.52 ± 0.04 hr-1.Compared to the lower oxidation rate of andosol,it is suggested that because of the low concentration of Mn(IV) in natural soils,the oxidation process of Sb(III) might be relatively slow and require more time to convert Sb(III) to Sb(V).     

Immobilization of microorganisms using carrageenan gels coated with chitosan and application to biodegradation of 4 chlorophenol

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Fouling of nanofiltration membrane by effluent organic matter： Characterization using different organic fractions in wastewater

The UF membrane with molecular weight cutoff (MWCO) ranging from 2 kDa to 100 kDa and XAD-8 resin were employed to identify the characteristic of molecular weight (MW) distribution of wastewater effluent organic matter (EfOM) in terms of TOC and UV254, as well as the amounts of the hydrophilic/hydrophobic organic fractions in different MW ranges. Then, the nanofiltration (NF) membrane fouling experiments were carried out using the above fractionated water to investigate the effect of MW distribution and hydrophilic/hydrophobic characteristics of EfOM on the membrane flux decline using the fractionated water samples above. The experimental results have shown that 45.61% of the total organics belongs to the low MW one, among which the percentage of the hydrophilic organics with low MW (less than 2 kDa) was up to 28.07%, while that of the hydrophobic organics was 17.54%. In particular, the hydrophilic fraction was found to be the most abundant fraction in the effluents. MW distribution has a significant effect on the membrane fouling. When the MW was less than 30 kDa, the lower the MW, the larger was the specific flux decline, while in the case of MW higher than 30 kDa, the higher the MW, the larger was the specific flux decline, and the decline degree of low MW organics was larger than the high MW one. With the same MW distribution range, specific flux decline of the hydrophilic organic was considerably slower than that of the hydrophobic organic, which indicated that the hydrophobic organic fractions dominantly contribute to the flux decline.     

Sorption of Triton X-100 on soil organic matter fractions：Kinetics and isotherms

Kinetics and isotherms of Triton X-100 sorption on soil,base-extracted soil(BE),humic acid (HA) and humin (HM) were investigated respectively to get better understanding on characteristics of the surfactant sorptiun onto different soil organic matters(SOMs).It was demonstrated that the kinetics results could be satisfactorily described by the pseudo-second order model.The half of the time to reach equilibrium(t1/2) for different sorbents followed the sequence of soil>HA>BE>HM.Furthermore,the calculated equilibrium sorption capacity(Ceq) was found in the sequence of HA>BE>HM>soil,which agreed well with the experimental results.The isotherms of Triton X-100 sorption on soil and HA could be well described by the S-type isotherm,but BE and HM by the L-type.The isotherms of all the four sorbents were found reasonably fitted to the Langmuir equation.The Kd value,defined as the ratio of Triton X-100 in sorbent and in the equilibrium solution for given concentrations,generally followed the order of HM>HA>soil>BE.Separated HM and HA showed high affinity for Triton X-100,but the HA and HM in soil and BE were tightly bounded by the minerals.Thus,the HA on the soil surface might dominate the sorption,whereas the bounded HM would play a key role upon the surfactants being penetrated inside the soil.     

Immobilization of activated sludge using improved polyvinyl alcohol （PVA） gel

The microbial immobilization method using polyvinyl alcohol(PVA)gel as an immobilizing material was improved and used for entrapment of activated sludge.The oxygen uptake rate(OUR)was used to characterize the biological activity of immobilized activated sludge.Three kinds of PVA-immobilized particles of activated sludge,that is,PVA-boric acid beads,PVA-sodium nitrate beads and PVA-orthophosphate beads were prepared,and their biological activity was compared by measuring the OUR value.The bioactivity of both autotrophic and heterotrophic microorganisms of activated sludge was determined using different synthetic wastewater media (containing 250 mg/L COD and 25 mg/L NH_4~ -N).The experimental results showed that the bioactivity and stability of the three kinds of immobilized activated sludge was greatly improved after activation.With respect of the bioactivity and the mechanical stability,the PVA-orthophosphate method may be a promising and economical technique for microbial immobilization.     

Effect of temperature and moisture on soil organic carbon mineralization of predominantly permafrost peatland in the Great Hing’an Mountains, Northeastern China

Boreal peatlands represent a large global carbon pool.The relationships between carbon mineralization,soil temperature and moisture in the permafrost peatlands of the Great Hing'an Mountains,China,were examined.The CO2 emissions were measured during laboratory incubations of samples from four sites under different temperatures(5,10,15,and 20°C) and moisture contents(0%,30%,60%,100% water holding capacity(WHC) and completely water saturated).Total carbon mineralization ranged from 15.51 to 112.92 mg C under the treatments for all sites.Carbon mineralization rates decreased with soil depth,increased with temperature,and reached the highest at 60% WHC at the same temperature.The calculated temperature coefficient(Q10) values ranged from 1.84 to 2.51 with the soil depths and moisture.However,the values were not significantly affected by soil moisture and depth for all sites due to the different peat properties(P 0.05).We found that the carbon mineralization could be successfully predicted as a two-compartment function with temperature and moisture(R2 0.96) and total carbon mineralization was significantly affected by temperature and moisture(P 0.05).Thus,temperature and moisture would play important roles in carbon mineralization of permafrost peatlands in the Great Hing'an Mountains,indicating that the permafrost peatlands would be sensitive to the environment change,and the permafrost peatlands would be potentially mineralized under future climate change.     

Ca2+ and SO42− interactions with dissolved organic matter: Implications of groundwater quality for CKDu incidence in Sri Lanka

It has recently been proposed that recalcitrant dissolved organic carbon(DOC) in groundwater plays a potent etiological role in the peculiar distribution of chronic kidney disease of unknown etiology(CKDu).This study aims to elucidate the interactions of Ca~(2+)and SO_4~(2-)with a model organic fraction of humic acid(SHA) to determine the possible relationship of CKDu incidence with the DOC in drinking water.XPS and FT-IR methods respectively determined the surface functional groups and chemical composition of protonated dissolved organic carbon(HDOC) in a CKDu high-risk zone(HR) of Sri Lanka and in SHA.Higher surface C composition(87.9%) and lower O(11.4%) were observed for HDOC from the HR region than for SHA(C: 73.8%, O: 24.7%).Aromatic C with less Ocontaining functional groups was observed in HDOC.The IR band at 1170 cm~(-1) confirms the formation of organic sulfonate(C–SO_3~-) on SHA.A band at 1213 cm~(-1) due to organic sulfonate in HDOC from the CKDu HR region was also identified.The IR band at 866 cm~(-1) evidenced the formation of CaCO_3 on SHA above pH 7.4.XPS data confirmed the presence of sulfur oxidation states corresponding to SO_3~(2-)and SO_4~(2-)at 168.9 eV and 170.1 eV binding energies,respectively.The binding energies at 347 eV and 351 eV for Ca 2p_(3/2) and Ca 2p_(1/2) eV,respectively, confirmed the bidentate complexation of Ca~(2+)with COO-and sulfonate groups on SHA.The organic sulfonate formed is postulated as a uremic toxicant.     

Study of multiresidue analytical method for organonitrogen and organophosphorus pesticides in soil and water

A gas chromatographic method without derivatization was developed for the residue analysis of 10 organonitrogen and 9 organophosphorus pesticides in soil and water. The samples were blended or shaken with acetone for extraction. The extracts were cleaned up by coagulation, then, re-extracted with three 50 ml portions of dichloromethane. The final residue was detected by gas chromatography equipped with NPD. All of the 19 pesticides were completely separated at a constant temperature. The method described above was applicable to the simultaneous determination of 10 organonitrogen and 9 organophosphorus pesticides .in soil and water with the satisfactory recovery (from 82.42% to 103.57%), coefficient of variance (from 0.17% to 12.57%) and limit of detection (from 0.0006 ppm to 0.058 ppm).     

Preparation of calibration standard of organic vapours using the diffusion tube method

This paper describe the theoretical consideration, experimental results and applications of diffusion tube, used for preparing the calibration standard of organic vapours. This dynamic procedure entirely eliminates the adsorption effect, which is important in static procedures. Its concentration range is wider than that of the permeation tube. The diffusion tube technique is therefore a very accurate, simple and easy-to-make device. It is quite useful in the determination of organic pollutants existing in the environment.     

Removal of inorganic arsenic from water using metal organic frameworks

<正>It has been estimated that between 94 million and 220 million people around the world are at risk of consuming drinking water that contain arsenic concentrations higher than 10 μg/L( Podgorski and Berg, 2020),     

High capacity adsorption of antimony in biomass-based composite and its consequential utilization as battery anode

Antimony is more than an emerging pollutant in water but a scare resource. In this study, we report an adsorbent with the record capacity so far from the balanced view of Sb(III) and Sb(V). The composite adsorbent was fabricated by encapsulating hollow Fe₃O₄ nanosphere with the EDTA grafted chitosan, and it has superhigh adsorption capacity of for 657.1 mg/g for Sb(III) and 467.3 mg/g for Sb(V), respectively. The mechanism study reveals that the adsorption of Sb initializes from the Fe₃O₄, propagates along the chitosan with hydrogen bond, and terminates at the inner sphere complex with the EDTA moiety in the adsorbent. In view of the ultra-high adsorption capacity of the adsorbent, the recovered adsorbent that contains abundant (>36.4%) highly dispersed antimony nanoparticles (600-FCSE-Sb) is applied to Li-ion battery anode after reduction. This article provides a new idea for connecting water treatment and electric energy storage.     

Removal of gaseous volatile organic compounds via vacuum ultraviolet photodegradation: Review and prospect

Volatile organic compounds (VOCs) have attracted much attention for decades as they are the precursors of photochemical smog and are harmful to the environment and human health. Vacuum ultraviolet (VUV) photodegradation is a simple and effective method to decompose VOCs (ranging from tens to hundreds of ppmV) without additional oxidants or catalysts in the air at atmospheric pressure. In this paper, we review the research progress of VOCs removal via VUV photodegradation. The fundamentals are outlined and the key operation factors for VOCs degradation, such as humidity, oxygen content, VOCs initial concentration, light intensity, and flow rate, are discussed. VUV photodegradation of VOCs mixture is elucidated. The application of VUV photodegradation in combination with ozone-assisted catalytic oxidation (OZCO) and photocatalytic oxidation (PCO) systems, and as the pre-treatment technique for biological purification are illustrated. Based on the summary, we propose the challenges of VUV photodegradation and perspectives for its future development.     

Molecular characterization of transformation and halogenation of natural organic matter during the UV/chlorine AOP using FT-ICR mass spectrometry

UV/chlorine process, as an emerging advanced oxidation process (AOP), was effective for removing micro-pollutants via various reactive radicals, but it also led to the changes of natural organic matter (NOM) and formation of disinfection byproducts (DBPs). By using negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS), the transformation of Suwannee River NOM (SRNOM) and the formation of chlorinated DBPs (Cl-DBPs) in the UV/chlorine AOP and subsequent post-chlorination were tracked and compared with dark chlorination. In comparison to dark chlorination, the involvement of ClO^?, Cl^?, and HO^? in the UV/chlorine AOP promoted the transformation of NOM by removing the compounds owning higher aromaticity (AI_mod) value and DBE (double-bond equivalence)/C ratio and causing the decrease in the proportion of aromatic compounds. Meanwhile, more compounds which contained only C, H, O, N atoms (CHON) were observed after the UV/chlorine AOP compared with dark chlorination via photolysis of organic chloramines or radical reactions. A total of 833 compounds contained C, H, O, Cl atoms (CHOCl) were observed after the UV/chlorine AOP, higher than 789 CHOCl compounds in dark chlorination, and one-chlorine-containing components were the dominant species. The different products from chlorine substitution reactions (SR) and addition reactions (AR) suggested that SR often occurred in the precursors owning higher H/C ratio and AR often occurred in the precursors owning higher aromaticity. Post-chlorination further caused the cleavages of NOM structures into small molecular weight compounds, removed CHON compounds and enhanced the formation of Cl-DBPs. The results provide information about NOM transformation and Cl-DBPs formation at molecular levels in the UV/chlorine AOP.     

Diverse molecular compositions of dissolved organic matter derived from different composts using ESI FT-ICR MS

Dissolved organic matter (DOM) derived from various composts can promote significant changes of soil properties. However, little is known about the DOM compositions and their similarities and differences at the molecular level. In this study, the molecular compositions of DOM derived from kitchen waste compost (KWC), green waste compost (GWC), manure waste compost (MWC), and sewage sludge compost (SSC) were characterized by electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The molecular formulas were classified into four subcategories: CHO, CHON, CHOS, and CHONS. The KWC, MWC, and SSC DOM represented the highest fraction (35.8%-47.4%) of CHON subcategory, while the GWC DOM represented the highest fraction (68.4%) of CHO subcategory. The GWC DOM was recognized as the nitrogen- and sulfur-deficient compounds that were less saturated, more aromatic, and more oxidized compared with other samples. Further analysis of the oxygen, nitrogen-containing (N-containing), and sulfur-containing (S-containing) functional groups in the four subcategories revealed higher organic molecular complexity. Comparison of the similarities and differences of the four samples revealed 22.8% ubiquitous formulas and 17.4%, 11.1%, 10.7%, and 6.3% unique formulas of GWC, KWC, SSC, and MWC DOM, respectively, suggesting a large proportion of ubiquitous DOM as well as unique, source-specific molecular signatures. The findings presented herein provide new insight into the molecular characterization of DOM derived from various composts and demonstrated the potential role of these different compounds for agricultural utilization.     

Kinetics of antimony biogeochemical processes under pre-definite anaerobic and aerobic conditions in a paddy soil

While the transformation of antimony(Sb) in paddy soil has been previously investigated, the biogeochemical processes of highly chemical active Sb in the soil remain poorly understood. In addition, there is a lack of quantitative understanding of Sb transformation in soil. Therefore, in this study, the kinetics of exogenous Sb in paddy soils were investigated under anaerobic and aerobic incubation conditions. The dissolved Sb(V) and the Sb(V) extracted by diffusive gradient technique decreased u...     

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO2 reduction: A review

Photocatalytic CO₂ reduction is an appealing strategy for mitigating the environmental effects of greenhouse gases while simultaneously producing valuable carbon-neutral fuels. Numerous attempts have been made to produce effective and efficient photocatalysts for CO₂ reduction. In contrast, the selection of competitive catalysts continues to be a substantial hindrance and a considerable difficulty in the development of photocatalytic CO₂ reduction. It is vital to emphasize different techniques for building effective photocatalysts to improve CO₂ reduction performance in order to achieve a long-term sustainability. Metal-organic frameworks (MOFs) are recently emerging as a new type of photocatalysts for CO₂ reduction due to their excellent CO₂ adsorption capability and unique structural characteristics. This review examines the most recent breakthroughs in various techniques for modifying MOFs in order to improve their efficiency of photocatalytic CO₂ reduction. The advantages of MOFs using as photocatalysts are summarized, followed by different methods for enhancing their effectiveness for photocatalytic CO₂ reduction via partial ion exchange of metal clusters, design of bimetal clusters, the modification of organic linkers, and the embedding of metal complexes. For integrating MOFs with semiconductors, metallic nanoparticles (NPs), and other materials, a number of different approaches have been also reviewed. The final section of this review discusses the existing challenges and future prospects of MOFs as photocatalysts for CO₂ reduction. Hopefully, this review can stimulate intensive research on the rational design and development of more effective MOF-based photocatalysts for visible-light driven CO₂ conversion.     

Potential applications of porous organic polymers as adsorbent for the adsorption of volatile organic compounds

Volatile organic compounds (VOCs) with high toxicity and carcinogenicity are emitted from kinds of industries, which endanger human health and the environment. Adsorption is a promising method for the treatment of VOCs due to its low cost and high efficiency. In recent years, activated carbons, zeolites, and mesoporous materials are widely used to remove VOCs because of their high specific surface area and abundant porosity. However, the hydrophilic nature and low desorption rate of those materials limit their commercial application. Furthermore, the adsorption capacities of VOCs still need to be improved. Porous organic polymers (POPs) with extremely high porosity, structural diversity, and hydrophobic have been considered as one of the most promising candidates for VOCs adsorption. This review generalized the superiority of POPs for VOCs adsorption compared to other porous materials and summarized the studies of VOCs adsorption on different types of POPs. Moreover, the mechanism of competitive adsorption between water and VOCs on the POPs was discussed. Finally, a concise outlook for utilizing POPs for VOCs adsorption was discussed, noting areas in which further work is needed to develop the next-generation POPs for practical applications.     

Adsorption and membrane separation for removal and recovery of volatile organic compounds

Volatile organic compounds(VOCs) are a crucial kind of pollutants in the environment due to their obvious features of severe toxicity, high volatility, and poor degradability. It is particularly urgent to control the emission of VOCs due to the persistent increase of concentration and the stringent regulations. In China, clear directions and requirements for reduction of VOCs have been given in the “national plan on environmental improvement for the 13th Five-Year Plan period”. Therefore, the de...     

Synergistic cytotoxicity of binary combinations of inorganic and organic disinfection byproducts assessed by real-time cell analysis

Chlorine, chlorine dioxide, and ozone are widely used as disinfectants in drinking water treatments. However, the combined use of different disinfectants can result in the formation of various organic and inorganic disinfection byproducts (DBPs). The toxic interactions, including synergism, addition, and antagonism, among the complex DBPs are still unclear. In this study, we established and verified a real-time cell analysis (RTCA) method for cytotoxicity measurement on Chinese hamster ovary (CHO) cell. Using this convenient and accurate method, we assessed the cytotoxicity of a series of binary combinations consisting of one of the 3 inorganic DBPs (chlorite, chlorate, and bromate) and one of the 32 regulated and emerging organic DBPs. The combination index (CI) of each combination was calculated and evaluated by isobolographic analysis to reflect the toxic interactions. The results confirmed the synergistic effect on cytotoxicity in the binary combinations consisting of chlorite and one of the 5 organic DBPs (2 iodinated DBPs (I-DBPs) and 3 brominated DBPs (Br-DBPs)), chlorate and one of the 4 organic DBPs (3 aromatic DBPs and dibromoacetonitrile), and bromate and one of the 3 organic DBPs (2 I-DBPs and dibromoacetic acid). The possible synergism mechanism of organic DBPs on the inorganic ones may be attributed to the influence of organic DBPs on cell membrane and cell antioxidant system. This study revealed the toxic interactions among organic and inorganic DBPs, and emphasized the latent adverse outcomes in the combined use of different disinfectants.