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Refractory organic matter (RfOM) is ubiquitous in aquatic environment and plays various roles in regulating the fate, transport, toxicity, and bioavailability of chemical species, such as metals, emerging organic contaminants, and nanomaterials. RfOM is mainly represented by humic acids (HA) as the acid insoluble fraction of organic matrix. Considering the complex and multicomponent characteristic of HA, a detailed study was designed to elucidate the fate of molecular size fractions (MSFrs) of humic under solar irradiation in the presence of polyaniline (PANI)-modified TiO2 composites. Humic acid as a consortium of diverse molecular size fractions with different tendencies towards oxidation requires further assessment by UV–vis and fluorescence spectroscopic parameters complementary to previous studies on the photocatalytic degradation of RfOM by using TiO2 and PANI-TiO2 composites. Absorbance-based removal efficiencies under initial and post-photocatalytic conditions showed a re-formation trend during photocatalysis in the presence of PANI and TiO2 where higher MSFrs were transformed to lower MSFrs that was apparent for < 3 kDa fraction. Completely different profiles were observed for PT-41 and PT-81 indicating similar degradation pathways independent of PANI ratio in the composite. As confirmed by the investigated parameters, formation of both 450 kDa and 220 kDa MSFrs were evident under all conditions indicating in situ generation of higher MSFrs. The eligibility of coupled absorbance-fluorescence measurements to discern molecular size distribution of humic acid via oxidative degradation was also investigated. Excitation-emission matrix (EEM) contour plots emphasized the ratio dependency of PANI modification of TiO2 and revealed sample specific variations that were more pronounced in terms of the emergence of tyrosine- and tryptophan-like aromatic proteins. [ABSTRACT FROM AUTHOR]

This study applied ultraviolet/peroxymonosulfate (UV/PMS) and UV/hydrogen peroxide (UV/H2O2) processes to the advanced treatment of membrane bioreactor (MBR) effluent. The degradation efficiency of refractory organic matter and the reaction mechanisms of the two processes were systematically investigated. The results showed that the degradation efficiency of the UV/PMS processes was significantly lower than that of the UV/H2O2 process when the PMS concentration was significantly lower than the H2O2 concentration, e.g. the UV254 removals under optimal conditions were 72.92% and 82.21%, respectively. Additionally, the UV/PMS process could operate over a broader pH range. The degradation efficiency of the UV/PMS process was slightly increased by HCO3– and Cl- due to the activation of PMS, while in the UV/H2O2 process, HCO3- and Cl- depressed the degradation efficiency by competing with organic matter to react with reactive oxygen species (ROS). After the two processes, the aromaticity, humification, condensation degree, and molecular weight of refractory organic matter in the MBR effluent were considerably decreased. Fulvic- (HA) and humic-like substances (FA) were greatly degraded by the two processes. The UV/PMS had a superior degradation efficiency for macromolecular HA in the early stage of the reaction, and the UV/H2O2 could degrade HA to protein-like substances in the latter stage of the reaction. These differences between the two processes could be attributed to the dominance of different ROS, with SO4•- and HO• dominating in the UV/PMS, and HO• dominating in the UV/H2O2. The results of this study provide theoretical support for the application of MBR effluent treatment. Highlights Comparison on the MBR effluent treatment of UV/PMS and UV/H2O2 is studied. UV/PMS process can better destroy humic-like substances in the early reaction stage. Humic-like substances are transformed into protein-like compounds in UV/H2O2 process. UV/PMS and UV/PMS performs differently due to their different dominant ROS. [ABSTRACT FROM AUTHOR]

Sludge lysis liquid is a highly concentrated solution containing macromolecular organic matter produced during thermal hydrolysis of sludge. Anaerobic digestion is commonly used to achieve degradation conversion and resource recovery. However, during the thermal conversion process, the presence of refractory organic matter such as Melad reaction products can result in low anaerobic conversion efficiency and methane yield. To address the issue, this study proposes a method for the intensive treatment and resource recovery of sludge lysis liquid using a microbial electrolysis-assisted anaerobic digestion (ME-AD) system. The study aimed to investigate the degradation efficacy of macromolecular organic matter and the conversion efficiency of short-chain fatty acids (SCFAs). The results of the study showed that the direct treatment of raw lysis liquid with ME-AD improved the anaerobic degradation efficiency compared to the usual treatment, which involved a 5-fold dilution of lysis liquid. The COD removal rate was 40.2% in the renewal batch cycle, which was 15.6% higher than the conventional anaerobic conversion. Additionally, the complex organic matter in the intensively degraded sludge lysis liquid was converted to SCFAs, which were produced at a maximum concentration of 40.0×10^5 mg/L during the fifth day of intensive anaerobic fermentation. Among the SCFAs, acetic acid had the highest percentage at 68.1%. This study provides a new approach to address the treatment of sludgelys is liquid and utilization of sludge resources.

Polyaniline (PANI) is a promising conducting polymer for surface modification of TiO2 to overcome limitations of the use of visible light and attain increased photocatalytic efficiency for the removal of organic contaminants. In this study, a series of polyaniline modified TiO2 (PANI-TiO2) composites were prepared by using "in-situ" chemical oxidation polymerization method. The composites were systematically characterized by Fourier transform infrared spectroscopy (equipped with an attenuated total reflection accessory, FTIR-ATR), Raman spectroscopy, X-ray diffractometry (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDAX), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL), nitrogen (N2) physisorption (Brunauer − Emmett − Teller surface area (SBET) and Barrett-Joyner-Halenda (BJH) pore size analysis), thermogravimetry-derivative thermogravimetry (TG-DTG) techniques. XRD patterns of PANI-TiO2 composites confirmed both the amorphous phase of PANI and the crystalline character of TiO2. TG/DTG analysis complemented the XRD profiles that the interactions between PANI and TiO2 resulted in a more stable PANI-TiO2 matrix. SEM images displayed the dominant morphology as dandelion-like shapes of PANI being more pronounced with increasing PANI ratios in PANI-TiO2 composites. UV-DRS profiles revealed that the band gap energies of the composites were lower than bare TiO2 expressing a shift to the visible light region. Both PL and UV-DRS analyses confirmed the band-gap reduction phenomenon of PANI modification of TiO2. The incorporation of PANI into TiO2 resulted in a reduction of the surface area of TiO2. The composites were subsequently subjected to photocatalytic activity assessment tests using humic acid (HA) as a model of refractory organic matter (RfOM) under simulated solar irradiation (Uyguner-Demirel et al. Environ Sci Pollut Res 30 85626-85638, 2023). The morphological and structural changes attained upon application of photocatalysis were also evaluated by FTIR-ATR, Raman spectroscopy, XRD, and SEM-EDAX methods in a comparable manner. The FTIR-ATR spectral features of PANI, RfOM and all composites displayed peaks with slight shifts under pre- and post- photocatalytic conditions as well as following dark surface interactions. Besides exhibiting noticeable photocatalytic performance, PANI-TiO2 composites were also proven to maintain stability under non-selective oxidation conditions in the presence of a complex organic matrix. The prepared PANI-TiO2 composites overcoming the limitations of UVA light active bare TiO2 photocatalysis could possibly find a beneficial use as potential catalysts in solar photocatalytic applications. [ABSTRACT FROM AUTHOR]

Surface modification of TiO2 with polyaniline (PANI) conducting polymer has been used to achieve visible light photoresponse, thereby increasing solar photocatalytic activity. In this study, photocatalytic performances of PANI-TiO2 composites with different mole ratios were synthesized by the in situ chemical oxidation polymerization method and tested for the degradation of a model refractory organic matter (RfOM), namely humic acid in an aqueous medium under simulated solar irradiation in a comparative manner. Adsorptive interactions under dark conditions and interactions under irradiation were investigated as contributing factors to photocatalysis. Degradation of RfOM was monitored in terms of UV–vis parameters (Color436, UV365, UV280, and UV254) and fluorescence spectroscopic parameters as well as the mineralization extent by dissolved organic carbon contents. The presence of PANI exerted an enhancement in photocatalytic degradation efficiency compared to pristine TiO2. The synergistic effect was more pronounced in lower PANI ratios whereas higher PANI ratios reflected a retardation effect. Degradation kinetics were assessed by pseudo-first-order kinetic model. For all UV–vis parameters analyzed, highest and lowest rate constants (k) were attained in the presence of PT-14 (2.093 × 10−2 to 2.750 × 10−2 min−1) and PT-81 (5.47 × 10−3 to 8.52 × 10−3 min−1), respectively. Variations in selected absorbance quotients, i.e., A254/A436, A280/A436, and A253/A203, were distinctive and compared with respect to irradiation time and photocatalyst type. Upon use of PT-14, a steady decreasing profile with respect to irradiation time was attained for A253/A203 quotient as 0.76–0.61, followed by a rapid decrease to 0.19 in 120 min. The incorporation effect of PANI into TiO2 composite could be visualized in A280/A365 and A254/A365 quotients exhibiting an almost constant and parallel trend. As a general trend, decrease in the major fluorophoric intensity FIsyn,470 with photocatalysis was observed under extended irradiation conditions; however, an abrupt decline was remarkable in the presence of PT-14 and PT-18. Fluorescence intensity decrease correlated well with spectroscopic evaluation of rate constants. A thorough evaluation of spectroscopic parameters of UV–vis and fluorescence can provide significant information for practical applications in control of RfOM in water treatment. [ABSTRACT FROM AUTHOR]

With the advancement of the landfill stabilization process of municipal solid waste, landfill leachate containing a large amount of refractory organic matter is formed. In this study, homogeneous Fenton and heterogeneous Fenton-like (activation by zero valent iron (Fe0), pyrite (FeS2) and magnetite (Fe3O4) as solid iron materials) processes have been compared for the removal of refractory organics from landfill leachate. The removal efficiency of organics in the Fenton process was slightly higher than those in the Fenton-like processes. The removal efficiencies based on total organic carbon, UV absorbance at 254 nm (UV254) and colour number in the Fenton process were as high as 57.42%, 71.63% and 81.03%, respectively. In the Fenton-like processes, the Fe0/H2O2 process achieved 35.74%, 66.24% and 86.29% removal efficiencies, respectively. Moreover, the degradation effect on refractory organic substances proved to be better. In the Fenton-like processes, the activation mechanisms with Fe0 and FeS2 involve the homogeneous activation of Fe2+ in solution and heterogeneous activation of iron oxides produced during the reaction, respectively. With Fe3O4, the activation mechanism is mainly a heterogeneous process involving its intrinsic iron oxide constituents. This study may provide a theoretical basis for the treatment of refractory organics in landfill leachate. [ABSTRACT FROM AUTHOR]

Water pollution control has become a challenge facing the whole society, and the original water treatment technology cannot be well promoted in practical applications. The proposal of the bacteria-algae symbiosis system not only effectively removes nutrients such as nitrogen and phosphorus, heavy metals and refractory organics in sewage, but also absorbs CO2 in the air, improves the removal efficiency of sewage contaminants, and integrates social and economic benefits technology. This article summarizes the status quo of sewage treatment technology in my country, introduces the mechanism of bacteria and algae symbiosis system to remove contaminants in water, and explains how immobilization technology affects the treatment efficiency of bacteria and algae symbiosis system. The technical research of sewage has made an outlook. [ABSTRACT FROM AUTHOR]

Swine wastewater effluent is a key source of water contamination since it contains high levels of nutrients, including nitrogen and phosphorus, as well as nitrates and refractory organic matter (ROM). ROM refers to organic compounds that are usually resistant to microbial degradation. When swine wastewater effluent containing high levels of ROM is subsequently discharged into rivers and streams without being adequately treated, purification costs for drinking water increase and there remains a possibility for harmful substances to enter the human body. In this study, we introduce new methods for setting total organic carbon (TOC) water quality standards for discharging swine wastewater effluent containing high levels of ROM after treatment. To set the TOC water quality standards, various analysis methods based on statistics, technology, and experience based on operational data of livestock-manure treatment facilities were applied. In addition, the achievability of the proposed TOC standards in livestock-manure treatment facilities and the financial burden of their implementation on livestock farms were also reviewed. Here, we set tentative values that include all of our results derived from each methodology and set the TOC standards to levels that can be achieved through the normal operation of swine-wastewater treatment facilities (60 mg/L for public treatment facilities and 140 mg/L for treatment facilities operated by individual farms). When setting TOC standards, both single and combined methodologies should be considered and employed after comprehensively assessing livestock management policies, regional conditions, and the burden on stakeholders. [ABSTRACT FROM AUTHOR]

In this study, the transformation and degradation mechanisms of refractory organic matter in biologically treated leachate from a semi-aerobic aged refuse biofilter (SAARB) in a nano-Fe3O4 enhanced ozonation process (nFe3O4-O3) were investigated in batch experiments. A continuous experiment then confirmed the effectiveness of the process for SAARB effluent treatment. In a batch experiment, the effects of influencing factors, including nFe3O4 dosage, O3 dosage and initial pH on the treatment performance of nFe3O4-O3 process, were comprehensively investigated. The results showed that when the nFe3O4 dosage = 6 g L−1, O3 dosage = 0.15 L minute−1 and initial pH = 7, the total organic carbon, absorbance at 254 nm and colour number removal efficiencies were 40.58%, 62.55% and 89.80%, respectively. In addition, most of the humic- and fulvic-like substances in the SAARB effluent were removed, and the condensation degree, aromaticity and humification degree of the organics were substantially reduced. The morphology and elemental valence state analysis showed that the nFe3O4 in the process was relatively stable and could form an nFe3O4-organic complex. Therefore, the probability of organics reacting with hydroxyl radical increased and the oxidation efficiency was enhanced. In the continuous experiment, both the O3 dosage and hydraulic retention time (HRT) were the key influencing factors. The treatment efficiency of the nFe3O4-O3 process was enhanced at a higher O3 dosage and longer HRT. The electrical energy consumption of the continuous nFe3O3-O3 process was calculated to be 17.72 kW h m−3 in SAARB effluent treatment. This study proved the feasibility of biologically treated landfill leachate treatment by the nFe3O3-O3 process. [ABSTRACT FROM AUTHOR]

This study applied two advanced oxidation processes dominated by different reactive oxygen species (ROS), microwave-iron-hydrogen peroxide (Microwave/ZVI/H 2 O 2) and microwave-iron-peroxydisulfate (MW Microwave/ZVI/PDS), to the degradation of refractory organic matter in the membrane bioreactor (MBR) effluent from landfill leachate treatment. The two processes were systematically compared according to their degradation efficiencies and transformation mechanisms toward refractory organic matter in MBR effluent. Controlled experiments and an influential factor analysis showed that the total organic carbon (TOC) removal efficiencies of the Microwave/ZVI/H 2 O 2 and Microwave/ZVI/PDS processes were 74.48% and 64.40%, respectively. After treatment by the two processes, fulvic-like substances with a low molecular weight and high fluorescence frequency, and humic-like substances with a large molecular weight, stable chemical structure, and high aromaticity were substantially degraded. In addition, the Microwave/ZVI/H 2 O 2 process had a better TOC removal efficiency than the Microwave/ZVI/PDS process over a wider pH range (3−11), which was mainly attributed to the different dominant ROS in the two processes. Both Fe 3 O 4 and FeOOH were found in the reacted ZVI of the two processes, and the reaction mechanisms included Fenton-like reactions and adsorption-precipitation by iron (hydro)oxides, which were promoted by microwave irradiation. This study provided a theoretical reference for the efficient treatment of MBR effluent. • Advanced oxidation of MBR effluent by MW/ZVIPDS and MW/ZVI/H 2 O 2 is studied. • MW/ZVI/H 2 O 2 has a better mineralization effect on organic matter in MBR effluent. • MW/ZVIPDS has a stable treatment performance over a wider pH range. • Humic- and fulvic-like substances are greatly degraded by MW/ZVI/PDS and MW/ZVIH 2 O 2. [ABSTRACT FROM AUTHOR]

As the typical quarternary ammonium compounds (QACs), benzalammonium bromide (BK) are frequently detected in sewage sludge. This study explored the responses of methane production from digestion sludge at present different BK addition. Experimental results indicated that BK stress seriously inhibited the methane production at the pre-anaerobic digestion stage, but the final cumulative methane production (∼ 1124.0 ± 40.2 mL/g VSS) was similar in these digesters. While BK obviously promoted the release and transformation of organic substances, but severely inhibited the rate of methane production. In addition, the relative abundances of hydrogenotrophic methanogens were significantly decreased from 69.38% to 38.57%, but the acetotrophic methanogens enhanced from 26.75% to 58.86% with BK exposure from 0 to 8.69 mg/g VSS. Correspondingly, BK addition could impact the key functional genes involved in the major methanogenic metabolic pathways and energy metabolism. This work shed light on the effect of BK on methane production under anaerobic sludge digestion system, and provide useful information to understand the relevant mechanism. [Display omitted] • Benzalammonium bromide stress significantly inhibited 17.2% methane production efficiency. • 8.69 mg BK/ kg VSS significantly enhanced 1.5 times soluble COD release than in the control. • Higher level of benzalammonium bromide reduced the H 2 -dependant methanogens. • Acetoclastic methanogenesis had an advantage over other methanogenesis with BK exposure. [ABSTRACT FROM AUTHOR]

This study applied ultraviolet/peroxymonosulfate (UV/PMS) and UV/hydrogen peroxide (UV/H 2 O 2 ) processes to the advanced treatment of membrane bioreactor (MBR) effluent. The degradation efficiency of refractory organic matter and the reaction mechanisms of the two processes were systematically investigated. The results showed that the degradation efficiency of the UV/PMS processes was significantly lower than that of the UV/H 2 O 2 process when the PMS concentration was significantly lower than the H 2 O 2 concentration, e.g. the UV 254 removals under optimal conditions were 72.92% and 82.21%, respectively. Additionally, the UV/PMS process could operate over a broader pH range. The degradation efficiency of the UV/PMS process was slightly increased by HCO 3 - and Cl - due to the activation of PMS, while in the UV/H 2 O 2 process, HCO 3 depressed the degradation efficiency by competing with organic matter to react with reactive oxygen species (ROS). After the two processes, the aromaticity, humification, condensation degree, and molecular weight of refractory organic matter in the MBR effluent were considerably decreased. Fulvic- (HA) and humic-like substances (FA) were greatly degraded by the two processes. The UV/PMS had a superior degradation efficiency for macromolecular HA in the early stage of the reaction, and the UV/H - and Cl - depressed the degradation efficiency by competing with organic matter to react with reactive oxygen species (ROS). After the two processes, the aromaticity, humification, condensation degree, and molecular weight of refractory organic matter in the MBR effluent were considerably decreased. Fulvic- (HA) and humic-like substances (FA) were greatly degraded by the two processes. The UV/PMS had a superior degradation efficiency for macromolecular HA in the early stage of the reaction, and the UV/H 2 O 2 could degrade HA to protein-like substances in the latter stage of the reaction. These differences between the two processes could be attributed to the dominance of different ROS, with SO 4 •- and HO • dominating in the UV/PMS, and HO • dominating in the UV/H 2 O 2 . The results of this study provide theoretical support for the application of MBR effluent treatment. Highlights Comparison on the MBR effluent treatment of UV/PMS and UV/H 2 O 2 is studied.UV/PMS process can better destroy humic-like substances in the early reaction stage.Humic-like substances are transformed into protein-like compounds in UV/H 2 O 2 process.UV/PMS and UV/PMS performs differently due to their different dominant ROS.

Stable isotopes of water (δ2H, δ18O) and δ13CTIC were used as a tool to trace the recharge processes, natural carbon (organic and inorganic) source and dynamics in the aquifers of the central Gangetic basin, India. Stable isotope (δ2H, δ18O) record of groundwater (n = 105) revealed that the groundwater of Piedmont was recharged by meteoric origin before evaporation, while aquifers of the older and younger alluvium were recharged by water that had undergone evaporation loss. River Ganges and its tributaries passing through this area have very little contribution in recharging while ponds play no role in the recharging of adjacent aquifers. The connectivity of shallow aquifers of aquitard formation (comprised of clay/sandy clay with thin patches of fine grey sand), i.e. 25–60 m below ground level (bgl) with the main upper aquifer (at a depth of >120 m bgl) was found to be higher in older and younger alluvium. Negative values of δ13CTIC (median −9.6 ‰; range −13.2 to −5.4 ‰) and high TIC (median 35 mM; range 31–46 mM) coupled with low TOC (median 1.35 mg/L; range 0.99–1.77 mg/L) indicated acceleration in microbial activity in the younger alluvium, especially in the active floodplain of river Ganges and its proximity. [ABSTRACT FROM AUTHOR]

Aiming at the excellent performance of advanced oxidation technology (AOP) in removing organic matter, the efficiency and mechanism of Fe0 activated H 2 O 2 , PMS and PDS in the removal of refractory organic matter in bio-treated landfill leachate (BTL) were systematically compared. The results showed that the removal effect of the three systems on organic matter was affected by the dosage of oxidant, the dosage of zero-valent iron, the initial pH value and the reaction time. After treatment with the three systems, the content of humic substances and aromatic organics in MBR effluent and the degree of molecular polymerization could be effectively reduced. Due to different ROS dominance in the three systems, there were differences in the efficacy of organic matter removal. The activation mechanism of Fe0 included homogeneous activation of Fe2+ and heterogeneous activation of in situ formation of iron oxides. Finally, considering various factors, such as the organic removal effect, oxidant toxicity, sludge yield, economy and potential impact of byproducts, the Fe0-H 2 O 2 system was superior to the other systems in the selection of treating refractory organics in landfill leachate MBR effluent. [Display omitted] • The Fe0-H 2 O 2 , Fe0-PMS and Fe0-PDS systems were compared. • The removal mechanism includes homogeneous activation and heterogeneous activation. • The main ROS showed the difference in the removal of organic matter. • The Fe0-H 2 O 2 is more suitable for the treatment of BTL in this study. [ABSTRACT FROM AUTHOR]

This study achieves a better operational simplicity for the phycoremediation of reverse osmosis (RO) concentrate using Scenedesmus quadricauda microalgae. Under continuous illumination with CO 2 supplementation, algal growth in the RO concentrate resulted in a conversion of polymeric organic matter (a mixture of humic substances and polysaccharides) to biodegradable fractions and their prompt removal along with inorganic nutrients (NO 3 − and PO 4 3− ). The algal-induced degradation of humic-like substances which are typically refractory to microbial decomposition was demonstrated in an indirect manner. In this study, we also investigated the effects of algal treatment on the growth of Escherichia coli and removal of trace organic compounds (TOrCs) from the RO concentrate. Our results indicate that algal treatment of the RO concentrate using aeration with 10% (v/v) CO 2 under continuous illumination is highly feasible as a safe and inexpensive technology to remove non- or slowly-biodegradable organic matter, reduce enteric bacteria, and attenuate TOrCs in wastewater. However, the results should not be generalized, but critically discussed, due to limitations of using the synthetic RO concentrate in evaluating the performance of wastewater remediation with microalgae. [ABSTRACT FROM AUTHOR]

Herein, we report a novel reactive nanostructured membrane (RNM) which integrated functionalities of effective peroxymonosulfate activation and advection-enhanced mass transfer rates, synthesized by anchoring nano-Co 3 O 4 inside the nanochannel of Ti 3 C 2 MXene as a co-catalyst, which was simultaneously embedded into a nickel foam support (denoted as Co/Ti 3 C 2 RNM). The outstanding properties were mainly attributed to electron migration regulation through the nanoconfinement effect and the d-band center of the Co/Ti 3 C 2 heterostructure close to the energy of the Fermi level. A 75.5 − 85.8% 1,4-dioxane (1,4-D) degradation in actual groundwater and bio-treated landfill leachate was achieved under a low pressure using a peristaltic pump and a high permeate flux of 237.8 L·m−2·h−1, corresponding to an ultrafast residence time of 3.7 s, in a single-pass flow-through mode. Singlet oxygen and Co(IV)-oxo species were mainly responsible for the 1,4-D removal. This study provides a strategy for the synthesis method of RNM combining the advantages of high catalytic activity and permeate flux. [Display omitted] • Ti−O−Co led to improved electron transfer and enhanced PMS activation. • The d-band center of Co/Ti 3 C 2 heterostructure close to the energy of Fermi level. • A high permeate flux of 237.8 L·m−2·h−1 corresponding to an ultrafast reaction time of 3.7 s was obtained. • Electron migration regulation through the nanoconfinement effect contributing to the catalytic activity. [ABSTRACT FROM AUTHOR]

The development of ultra-efficient, sustainable, and easily accessible catalytic particle (CP) is a useful strategy for hydroxyl radical generation in the three-dimensional electrolytic system (3D ECs). Herein, a crystalline fused CP composed of coal gangue, activated sludge, and iron sludge, were synthesized for refractory organic matter electrocatalytic combustion in a boron-doped diamond (BDD) 3D ECs. A rough and SnO 2 semiconductor metal oxide pellet-anchored continuous interface was created through a one-pot calcination method. In determination of the CP agglomeration mechanism, XRD and XPS results displayed that discrete component of SiO 2 , Al 2 O 3 , and Na 2 O were transformed into a homogeneous quartz albite NaAlSi 3 O 8 phase, and SnO 2 -Sb 2 O 5 components formed and spread in the whole ball structure during high-temperature molding process. The newly designed CP exhibited incomparable phenol degradation capacity. The dichromate oxidizability (COD Cr) removal efficiency of phenolic wastewater increased 14.3 % compared to the commercial active carbon packed system. The electrocatalytic oxidation capacity of CP was evaluated comprehensively under various working condition, e. g. different cathodes, present or absent of Cl- and persulfate agents, and with or without microbubble coupling. Our experimental results showed that considerable COD Cr removal efficiency of 86.3 % was obtained with microbubble coupling oxidation using cell voltage 6.0 V and treating time 120 mins. Besides these, the designed CP presented outstanding stability, and COD Cr removal efficiency slightly decreased 7.1 % after 10 cycle repetitions. The use of solid waste as the main material for CPs production not only realizes harmless treatment of solid wastes but also improve the 3D ECs significantly. [Display omitted] • A Sustainable and effective catalytic particle was manufactured using solid waste. • Catalytic particle exhibited excellent catalytic activity and cycling stability. • Compared with activated carbon, COD Cr degradation efficiency was improved by 14.3 %. [ABSTRACT FROM AUTHOR]

• Ozone pretreatment combined with PD/A was proposed for COD and N removal from NFC. • Ozone pretreatment reduced 25% of refractory organics and enhanced biodegradability. • NH 4 + and NO 3 – produced by ozone oxidation can be removed by PDA simultaneously. • Enhanced N removal with effluent TN below Chinese standards limitation of 40 mg/L. Treatment of nanofiltration concentrate (NFC) from landfill leachate is challenging due to its complex composition and high concentration of refractory organic matter. This study proposed a combined process of ozone pretreatment and partial denitrification/anammox (PD/A) for treating NFC, exploring the feasibility of using ozone-oxidized NFC as a carbon source for partial denitrification. The ozone oxidation process was employed to degrade the refractory organic compounds. With an ozone flow rate of 1.2 L/min and a reaction time of 50 min, the chemical oxygen demand (COD) removal efficiency of NFC was 20.83%, and the volatile fatty acid (VFA) content reached a maximum value of 104.37 mg/L. Meanwhile, the process significantly increased the ammonia and nitrate concentrations in the NFC. Then, PD/A process was applied to remove nitrogen from the NFC. Results showed that PD/A can effectively remove nitrogen from the NFC without additional carbon source. Using VFA produced in the ozone oxidation stage as carbon source, the reactor achieved a nitrogen removal efficiency of approximately 70%, resulting in an effluent with a total nitrogen below 40 mg/L, which satisfied the relevant standards in China. This study provides new insights into the application of ozone oxidation and PD/A in treating NFC from leachate. [ABSTRACT FROM AUTHOR]

Hydrothermal vent fluids contain thermally modified dissolved organic matter (DOM) originally entrained from sediments and seawater. We hypothesized that in hydrothermal systems DOM molecular composition is modulated by (i) fluid contribution, (ii) thermal decomposition and pH, and (iii) aspects particular to the vent system. Hence, solid phase extracted (SPE) DOM samples collected along the Mid-Atlantic Ridge (MAR) were molecularly characterized via 15 Tesla Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The molecular character of an oceanic DOM sample was also determined before and after thermal (300 °C) decomposition at acidic and neutral pH. Multivariate statistical analysis indicated that DOM composition was strongly influenced by fluid contribution (Mg 2+ concentration between 12 and 54 mM), which correlated positively with measured temperature (between 8 and 375 °C). In comparison, pH of the fluids (between 2.5 and 6.9) had a minor influence. Seafloor pressure, used as a theoretical maximum fluid temperature at the seafloor, separated the fluids collected at Menez Gwen from deeper locations, due to the higher abundance of peptide, carboxyl-rich alicyclic (CRAM) and aromatic molecular formulae at Menez Gwen. Compared with seawater DOM, thermally decomposed DOM had on average lower molecular mass, lower O/C ratios, fewer double bond equivalents, and fewer CRAM formulae but higher aromaticity - the same molecular features displayed by MAR hydrothermal fluids. The study provides evidence that thermal reworking plays a major role in shaping DOM mixtures from hydrothermal fluids along the MAR, which partly represent thermally reworked marine DOM that survived hydrothermal circulation. [ABSTRACT FROM AUTHOR]

Swine wastewater is one of the most serious pollution sources, and it has attracted a great public concern in China. Anaerobic digestion technology is extensively used in swine wastewater treatment. However, the anaerobic digestion effluents are difficult to meet the discharge standard. The results from batch experiments showed that plenty of refractory organic matter remained in the effluents after mesophilic anaerobic digestion for 30 days. The effluent total COD (tCOD) and soluble COD (sCOD) were 483 and 324 mg/L, respectively, with the sCOD/tCOD ratio of 0.671. Fluorescence excitation-emission matrix (EEM) coupled with parallel factor analysis (PARAFAC) revealed that the dissolved organic matter in the effluents was tryptophan-like substance, humic acid substance, and fulvic acid substance. Based on the appearance time during anaerobic digestion, tryptophan-like substance and humic acid substance were inferred to originate from the raw swine wastewater, and the fulvic acid substance was inferred to be formed in the anaerobic digestion. This work has revealed the source of residual organic matter in anaerobic digestion of swine wastewater and has provided some valuable information for the post-treatment. [ABSTRACT FROM AUTHOR]

Spectroscopic and chromatographic changes in dissolved organic matter (DOM) characteristics of influent and treated sewage were investigated for a wastewater treatment plant (WWTP) with a biological advanced process. Refractory DOM (R-DOM) was defined as the dissolved organic carbon concentrations of the samples after 28-day incubation for this study. Specific UV absorbance (SUVA), hydrophobicity, synchronous fluorescence spectra and molecular weight (MW) distributions were selected as DOM characteristics. The percent distribution of R-DOM for the effluent was much higher than that of the influent, indicating that biodegradable DOM was selectively removed during the process. Comparison of the influent versus the effluent sewage revealed that SUVA, fulvic-like fluorescence (FLF), humic-like fluorescence (HLF), the apparent MW values were enhanced during the treatment. This suggests that more aromatic and humic-like compounds were enriched during the biological process. No significant difference in the DOM characteristics was observed between the original effluent (i.e., prior to the incubation) and the influent sewage after the incubation. This result suggests that the major changes in wastewater DOM characteristics occurring during the biological advanced process were similar to those for simple microbial incubation.

[Display omitted] • Exploiting ROM for advanced N removal via AMX from mature leachate was studied. • High TN and TOC removal (94.50 %, 27.12 %) were obtained with NLR of 2.4 kg N/(m3·d). • Prolonging HRT was beneficial to N removal and SMP, humus, fulvic acid utilization. • Anaerolineaceae abundance increased (21.63% to 49.21%) enhancing ROM utilization. Anammox is an efficient low-carbon nitrogen removal technology for mature landfill leachate (MLL). However, it produces 11 % nitrate theoretically, which needs further removal. In this study, the mechanisms of exploiting refractory organic matter (ROM) from an MLL as an inner carbon source for advanced nitrogen removal via anammox were systematically analyzed, and the effects of hydraulic retention time on nitrogen and ROM removal/utilization were investigated. Without any external carbon source, a total nitrogen and organic carbon removal efficiency of 94.50 % and 27.12 %, respectively, were achieved, with a nitrogen loading rate of 2.4 kg N/(m3·d). The abundances of norank_f_norank_o_SBR1031 , OLB13 , and norank_f_A4b , which had the capacity to degrade ROM, increased from 21.63 % to 49.21 %. This study reveals that the ROM in an MLL can be exploited for synchronous advanced nitrogen and organic matter removal. [ABSTRACT FROM AUTHOR]

Microbial cycling of dissolved dimethylsulfoniopropionate (DMSPd) and the fate of DMSP-sulfur were measured in the northern Gulf of Mexico off the Louisiana coast in September 2011 using the tracer [sup 35]S-DMSPd. Salinity ranged from 31.2 ppt in the Mississippi River plume to 36.5 ppt offshore. Total DMSP concentrations were significantly higher at the river-influenced stations (12-27 nM) than offshore (6-14 nM). From 8.7 to 27% of the measured DMSPd, equivalent to 0.1 to 0.23 nM, was refractory (i.e. non-bioavailable). We subtracted refractory DMSPd from the measured DMSPd concentrations when calculating DMSPd consumption rates with the tracer [sup 35]S-DMSPd. DMSPd consumption and bacterial production were respectively 8 and 7 times higher in the river plume compared with offshore. Incorporation of DMSP-sulfur into biomass was almost three times higher in river-influenced water, whereas the dimethylsulfide (DMS) yield was 3.5 times lower in the river plume compared with offshore. Accordingly, DMSP contributed over 3 times more to the bacterial demand for both carbon and sulfur in the river-influenced water. Despite lower DMS yields in the river plume, the fast DMSP turnover resulted in a 2.7-times higher DMS production compared with offshore waters. Mississippi River inputs and the resulting high productivity led to a rapid turnover of DMSP and high DMS production in the river plume compared with oligotrophic Gulf of Mexico waters. Failure to account for refractory DMSPd when using the [sup 35]S-DMSP method will lead to significant overestimation of the DMSPd turnover flux and its contributions to C and S cycling. [ABSTRACT FROM AUTHOR]

Heavy oil-produced water (HOPW) is a by-product during heavy oil exploitation and can cause serious environmental pollution if discharged without adequate treatment. Commercial biochemical treatment units are important parts of HOPW treatment processes, but many are not in stable operation because of the toxic and refractory substances, salt, present. Therefore, pilot-scale experiments were conducted to evaluate the performance of hydrolytic acidification-biological filter with airlift aeration (HA-BFAA), a novel HOPW treatment system. Four strains isolated from oily sludge were used for bioaugmentation to enhance the biodegradation of organic pollutants. The isolated bacteria were evaluated using 3-day biochemical oxygen demand, oil, dodecyl benzene sulfonic acid, and chemical oxygen demand (COD) removals as evaluation indices. Bioaugmentation enhanced the COD removal by 43.5 mg/L under a volume load of 0.249 kg COD/m day and hydraulic retention time of 33.6 h. The effluent COD was 70.9 mg/L and the corresponding COD removal was 75.0 %. The optimum volumetric air-to-water ratio was below 10. The removal ratios of the total extractable organic pollutants, alkanes, and poly-aromatic hydrocarbons were 71.1, 94.4, and 94.0 %, respectively. Results demonstrated that HA-BFAA was an excellent HOPW treatment system. [ABSTRACT FROM AUTHOR]

Purpose: The main goal of this work was to determine the pyrogenic carbon (PyC) distribution in surficial sediments for the last 40 km of the Guadiana River (SW Iberian Peninsula). In addition, the changes in the contribution of terrestrial and marine organic matter (OM) sources and their relationship with the PyC contents were assessed. Materials and methods: Sediments were collected from 22 stations within the lower course of the Guadiana River. All the samples were analyzed for total organic carbon (TOC), total nitrogen (TN), organic carbon to nitrogen atomic ratios (C/N), and stable carbon isotope ratio (δC) as indicators of changes in the sources of OM. PyC was determined according to the chemo-thermal oxidation method (CTO-375). Results and discussion: TOC ranged from 0.25 to 2.37 %dw. The greatest TOC contents were located in sediments collected at the middle estuary. The C/N values ranged from 7.7 to 12.7, with slight relative increase in the marine input compared to pre-Alqueva times. Similar C/N ranges are representative of native soil OM, lacustrine OM, and local sedimentary OM. The δ C values of the sediment samples ranged from -25.0 to -27.6 ‰ illustrating a signature of C higher plants, marsh-plants, lacustrine plants, and freshwater algae present in the area of study and in the forests located upstream. PyC ranged between 0.17 and 0.74 gkg, with the highest contents measured in samples located close to urbanized areas. Sediments collected at the middle estuary, within a rural area, showed the lowest proportions of PyC relative to the percent of TOC (≤4 % TOC). The negative relationship between PyC to TOC ratio and TOC contents confirmed the selective preservation of PyC to degradation in the sedimentary OM of the Guadiana estuary. The carbon isotope composition of the final material after applying the CTO-375 method (hereafter called δC) was ˂-30 ‰, suggesting that the PyC fraction was mainly composed of a mixture of fossil fuels and C-charred biomass. Nevertheless, selective loss of the less recalcitrant OM fractions due to degradation and/or chemical alteration might contribute to lighter carbon isotope values of PyC. Conclusions: Geochemical data showed that sedimentary OM was composed of a mix of different OM sources, with a slight increase in the marine input after the Alqueva dam went into operation. The PyC content was higher close to urbanized areas of the Guadiana River estuary. The selective preservation of PyC in the sedimentary OM of the Guadiana estuary was observed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Supply of co-substrate to algae-bacteria consortia enhances antibiotics degradation. • Co-substrate improved SDZ degradation more significantly than SMX degradation. • Co-substrate induced the secretion of microalgal EPS with high protein ratios. • Supplementation of co-substrate could decrease peroxide damage to cells. • The symbiotic bacterial diversities were analyzed by high throughput sequencing. Both co-cultivation and co-substrate addition strategies have exhibited massive potential in microalgae-based antibiotic bioremediation. In this study, glucose and sodium acetate were employed as co-substrate in the cultivation of microalgae-bacteria consortium for enhanced sulfadiazine (SDZ) and sulfamethoxazole (SMX) removal. Glucose demonstrated a two-fold increase in biomass production with a maximum specific growth rate of 0.63 ± 0.01 d−1 compared with sodium acetate. The supplementation of co-substrate enhanced the degradation of SDZ significantly up to 703 ± 18% for sodium acetate and 290 ± 22% for glucose, but had almost no effect on SMX. The activities of antioxidant enzymes, including peroxidase, superoxide dismutase and catalase decreased with co-substrate supplementation. Chlorophyll a was associated with protection against sulfonamides and chlorophyll b might contribute to SDZ degradation. The addition of co-substrates influenced bacterial community structure greatly. Glucose enhanced the relative abundance of Proteobacteria , while sodium acetate improved the relative abundance of Bacteroidetes significantly. [ABSTRACT FROM AUTHOR]

• GONs doping boosted the electrooxidation ability of Ti 4 O 7 REM. • 1 wt % GONs doping significantly reduced the charge-transfer resistance. • The •OH yield of 1%GONs@Ti 4 O 7 REM improves 2.5–2.8 times. • GONs doping can facilitate the stability of Ti 4 O 7 REM. • Energy cost (EE/O) for treating 1,4-D was observed at only 0.34–0.74 kWh/m3. Although Ti 4 O 7 ceramic membrane has been recognized as one of the most promising anode materials for electrochemical advanced oxidation process (EAOP), it suffers from relatively low hydroxyl radical (•OH) production rate and high charge-transfer resistance that restricted its oxidation performance of organic pollutants. Herein, we reported an effective interface engineering strategy to develop a Ti 4 O 7 reactive electrochemical membrane (REM) doped by graphene oxide nanoparticles (GONs), GONs@Ti 4 O 7 REM, via strong GONs–O–Ti bonds. Results showed that 1% (wt%) GON doping on Ti 4 O 7 REM significantly reduced the charge-transfer resistance from 73.87 to 8.42 Ω compared with the pristine Ti 4 O 7 REM, and yielded •OH at 2.5–2.8 times higher rate. The 1,4-dioxane (1,4-D) oxidation rate in batch experiments by 1%GONs@Ti 4 O 7 REM was 1.49×10−2 min−1, 2 times higher than that of the pristine Ti 4 O 7 REM (7.51×10−3 min−1) and similar to that of BDD (1.79×10−2 min−1). The 1%GONs@Ti 4 O 7 REM exhibited high stability after a polarization test of 90 h at 80 mA/cm2, and within 15 consecutive cycles, its oxidation performance was stable (95.1–99.2%) with about 1% of GONs lost on the REM. In addition, REM process can efficiently degrade refractory organic matters in the groundwater and landfill leachate, the total organic carbon was removed by 54.5% with a single-pass REM. A normalized electric energy consumption per log removal of 1,4-D (EE/O) was observed at only 0.2–0.6 kWh/m3. Our results suggested that chemical-bonded interface engineering strategy using GONs can facilitate the EAOP performance of Ti 4 O 7 ceramic membrane with outstanding reactivity and stability. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] The molecular composition of A-horizons under different land-use was characterized. [•] We found contrasting composition of NaOH-extractable and non-extractable SOM for each land-use. [•] The molecular composition of SOM offers potential to reconstruct soil (pre)history. [Copyright &y& Elsevier]

In this study, the transformation and degradation mechanisms of refractory organic matter in biologically treated leachate from a semi-aerobic aged refuse biofilter (SAARB) in a nano-Fe 3 O 4 enhanced ozonation process (nFe 3 O 4 -O 3 ) were investigated in batch experiments. A continuous experiment then confirmed the effectiveness of the process for SAARB effluent treatment. In a batch experiment, the effects of influencing factors, including nFe 3 O 4 dosage, O 3 dosage and initial pH on the treatment performance of nFe 3 O 4 -O 3 process, were comprehensively investigated. The results showed that when the nFe 3 O 4 dosage = 6 g L -1 , O 3 dosage = 0.15 L minute -1 and initial pH = 7, the total organic carbon, absorbance at 254 nm and colour number removal efficiencies were 40.58%, 62.55% and 89.80%, respectively. In addition, most of the humic- and fulvic-like substances in the SAARB effluent were removed, and the condensation degree, aromaticity and humification degree of the organics were substantially reduced. The morphology and elemental valence state analysis showed that the nFe 3 O 4 in the process was relatively stable and could form an nFe 3 O 4 -organic complex. Therefore, the probability of organics reacting with hydroxyl radical increased and the oxidation efficiency was enhanced. In the continuous experiment, both the O 3 dosage and hydraulic retention time (HRT) were the key influencing factors. The treatment efficiency of the nFe 3 O 4 -O 3 process was enhanced at a higher O 3 dosage and longer HRT. The electrical energy consumption of the continuous nFe 3 O 3 -O 3 process was calculated to be 17.72 kW h m -3 in SAARB effluent treatment. This study proved the feasibility of biologically treated landfill leachate treatment by the nFe 3 O 3 -O 3 process.

Abstract: Mature landfill leachate was anaerobically co-digested with synthetic wastewater to evaluate the degradability and methane productivity in various mixing ratios. The proportion of leachate was increased in three equal steps from 0% to 100%, and then decreased again through the same steps back to 0%. Both COD removal efficiency and methane production decreased as the leachate proportion in the influent was increased. When the influent contained 100% leachate, and when 33% synthetic wastewater was reintroduced, methane production was suppressed relative to COD removal. During the same phases, accumulated, suggesting an excess of mineralization versus uptake. After 100% leachate was supplied, methane yield decreased to near zero, and the production of methane remained suppressed relative to COD reduction even as more synthetic wastewater was reintroduced, until 100% synthetic wastewater was resupplied. This decline in methane yield might be caused by deterioration of methanogenic bacterial activity following treatment of 100% leachate. [Copyright &y& Elsevier]

The concentrations of dissolved organic carbon and nitrogen (DOC and DON, respectively) were measured in Shiraho fringing reef (Japan), using a high-temperature catalytic-oxidation method. When the seawater on the reef flat (shallow lagoon) was isolated from the surrounding ocean due to the low tide, the concentrations of DOC and DON on the reef flat were 66-75 and 4.8-5.7 μmol l, respectively. The DOC and DON concentrations were higher than those of the adjacent outer ocean (57-58 and 3.8 μmol l, respectively), suggesting that the coral reef functioned as a net source of dissolved organic matter for the surrounding ocean. In order to investigate long-term bacterial decomposition of the reef-derived DOC (RF-DOC), the seawater samples collected on the reef flat and at the adjacent ocean were incubated in the dark for 1 year. Regression analysis using an exponential curve that considered two degradability pools (labile and refractory) fitted the mineralization of the RF-DOC very well ( r > 0.89). According to the regression analysis, the DOC produced on the reef flat was composed of the labile fraction of 63-94% (average 77%) and the refractory fraction of 6-37% (average 23%). It was concluded that some of the DOC that was produced in the coral reef ecosystem was exported to the surrounding ocean if the reef flat had a water residence time less than several months. The exported organic matter may support microbial communities in the ocean as an energy source. [ABSTRACT FROM AUTHOR]

Coral mucus released from Acropora formosa and Montipora digitata was incubated with bacteria under dark conditions for 1 year to evaluate the quantitative degradability. All the mucus samples showed a similar decomposition pattern: about 80% of total organic carbon (TOC) in the mucus was mineralized within 1 month, while some mucus was slowly decomposed over the 1 year. Regression analysis using an exponential curve considering three degradability pools (labile, semilabile, and refractory) fitted the changes of the TOC concentrations very well ( r > 0.99). Compiling the data on the two coral species, the labile organic C in the coral mucus had mineralization rates of 10-18% d and accounted for 79-87% of the initial TOC in the mucus. Semilabile organic C had mineralization rates of 0.3−1.6% d and accounted for 11−18% of the initial TOC. Refractory organic C accounted for 6% at most. These results suggest that not all coral mucus is rapidly decomposed by bacteria but some mucus remains as semilabile and refractory organic matter for several months. [ABSTRACT FROM AUTHOR]

Spectroscopic and chromatographic changes in dissolved organic matter (DOM) characteristics of influent and treated sewage were investigated for a wastewater treatment plant (WWTP) with a biological advanced process. Refractory DOM (R-DOM) was defined as the dissolved organic carbon concentrations of the samples after 28-day incubation for this study. Specific UV absorbance (SUVA), hydrophobicity, synchronous fluorescence spectra and molecular weight (MW) distributions were selected as DOM characteristics. The percent distribution of R-DOM for the effluent was much higher than that of the influent, indicating that biodegradable DOM was selectively removed during the process. Comparison of the influent versus the effluent sewage revealed that SUVA, fulvic-like fluorescence (FLF), humic-like fluorescence (HLF), the apparent MW values were enhanced during the treatment. This suggests that more aromatic and humic-like compounds were enriched during the biological process. No significant difference in the DOM characteristics was observed between the original effluent (i.e., prior to the incubation) and the influent sewage after the incubation. This result suggests that the major changes in wastewater DOM characteristics occurring during the biological advanced process were similar to those for simple microbial incubation. [ABSTRACT FROM AUTHOR]

An already established analytical method for the quantification of freshwater refractory organic matter (often called humic substances) has been applied to organic matter from a wastewater treatment plant's effluent and a number of downstream locations impacted by the treatment plant. The method is based on measuring the peak currents obtained by adsorptive stripping voltammetry of the complex formed by freshwater refractory organic matter in the presence of trace amounts of Mo(VI). Organic matter is first concentrated by reverse osmosis, then fractionated according to its polarity by the sequential application of DAX-8 and XAD-4 resins. The results obtained show that the voltammetric method measures the refractory organic matter present in the different sewage-derived fractions and that the response obtained follows the trend expected for the fractionation method used (i.e. more hydrophobic fractions largely give the strongest signals). These results have been compared with those obtained from IHSS substances. The results of this study are of particular significance in that it shows that, when applied to surface waters, the voltammetric method measures any refractory organic matter present, irrespective of its origin. [ABSTRACT FROM AUTHOR]

Abstract: Black carbon (BC), presenting the residue from incomplete combustion processes of fossil fuels and vegetation, has received special interest as a possible carbon sink in soils and sediments. In spite of this, there is still a need to develop accurate and comparable analytical protocols to determine the amount of BC stored in different environmental matrices and to characterise potentially interfering materials in the analysis of BC. Therefore in this study a melanoidin, a sample from the Green River Shale, a lignite and a bituminous coal were characterised by means of elemental analysis, thermogravimetry–differential scanning calorimetry (TG–DSC), pyrolysis coupled with gas chromatography–mass spectrometry (Py-GC/MS) and 13C NMR spectroscopy. Thermal analysis (TG–DSC) indicated larger contributions of labile OM in the melanoidin and in the shale samples than in the lignite and the bituminous coal, although the coals showed an intense exothermal peak at temperatures higher than 550°C. This behaviour is in agreement with high thermal recalcitrance of the latter and was also found in earlier studies of BC-rich material. Comparable to the latter, Py-GC/MS of the coals reveals considerable amounts of lignin-derived products. This and the similar thermal behaviour of both refractory materials aggravate their discrimination during BC-analysis. The pyrogram of the melanoidin reveals an important contribution of furanes and pyrane-like structures that derive from carbohydrates. NMR spectroscopy supports that those compounds are original constituents of the melanoidin rather than solely pyrolysis products. Considering that those compounds are typically formed during charring of N-containing biomass, their contribution to the BC structure should not be neglected if one seeks for a better understanding of BC structural properties. For the shale sample, both analytical pyrolysis and 13C NMR spectroscopy confirm a high contribution of long alkyl-C chains. Due to their high hydrophobicity such structures can stand chemical oxidation and their presence in soil and sediment samples can obscure BC quantification by those methods. This study indicates that present approaches for BC-identification that are based on the assumption of BC being mostly a highly condensed polyaromatic network, have to be taken with caution and modified in accordance with a more heterogeneous composition of BC containing considerable fractions of only partly charred biopolymers. [Copyright &y& Elsevier]

A recently published method for quantifying refractory organic matter (often referred to as humic substances) in freshwaters was applied to a wide range of International Humic Substance Society (IHSS) humic compounds in order to (i) gain a better understanding of the mechanism of the voltammetric response which is the basis of the analytical method and (ii) provide guidance on choosing the optimal standard to be used. At the same time, the sensitivity of the technique has been increased by switching from the pulse mode initially proposed to the square-wave mode. The results obtained show that (i) differences in adsorption onto the electrode rather than differences in complexation strength are responsible for the differences in the intensity of the signal obtained for the different humic compounds, (ii) carboxylate, N- and S-containing groups do not play a role in the voltammetric signal. [ABSTRACT FROM AUTHOR]

Abstract: In Mediterranean ecosystems, forest fires are a common phenomenon. They involve the transformation of vegetation and litter, leaving charred residues and so influencing the carbon cycle by changing (a) the amounts of soil organic matter and (b) the proportions within it of pools with differing stability. In addition to affecting C cycles, fires also affect the amounts of N within soil organic matter, and its availability. Because of the difficulties associated with solvent-based methods for the investigation of char and other highly stable carbon forms within soil, physical methods based on pyrolysis have several advantages. We have used thermal analysis coupled with on-line analysis of evolved gas species to determine the proportions of soil organic matter of differing stability and the pattern of evolution of gaseous nitrogen-bearing species during heating. Burnt soil clearly has a lower content of labile organic matter than unburnt soil, and nitrogen is closely associated with more stable forms of soil organic matter. Using the decomposition temperatures observed from TG, triple shot pyrolysis–GC/MS shows clear differences between the molecular composition of burnt and unburnt samples. At 340 °C, the unburnt soil has a diverse content of polysaccharide-derived and aliphatic compounds, while the burnt soil yields only two furan compounds. At 520 °C, alkyl and aromatic compounds are observed, including PAHs from the burnt soil. The 600 °C shot is dominated by aromatic compounds, with no differences between burnt and unburnt samples. Taken together, the results of elemental analysis, TG–DSC–QMS and pyrolysis–GC/MS are a very helpful tools in the deciphering of changes in the soil organic matter properties, specifically the main changes observed are (a) to increase the proportion of thermally-stable components, and (b) to increase the proportion of nitrogen relative to C through the development of thermally stable heterocyclic N. [Copyright &y& Elsevier]

Abstract: In most natural sedimentary systems labile and refractory organic material (OM) occur concomitantly. Little, however, is known on how different kinds of OM interact and how such interactions affect early diagenesis in sediments. In a simple sediment experiment, we investigated how interactions of OM substrates of different degradability affect benthic nitrogen (N) dynamics. Temporal evolution of a set of selected biogeochemical parameters was monitored in sandy sediment over 116 days in three experimental set-ups spiked with labile OM (tissue of Mytilus edulis), refractory OM (mostly aged Zostera marina and macroalgae), and a 1:1 mixture of labile and refractory OM. The initial amounts of particulate organic carbon (POC) were identical in the three set-ups. To check for non-linear interactions between labile and refractory OM, the evolution of the mixture system was compared with the evolution of the simple sum of the labile and refractory systems, divided by two. The sum system is the experimental control where labile and refractory OM are virtually combined but not allowed to interact. During the first 30 days there was evidence for net dissolved-inorganic-nitrogen (DIN) production followed by net DIN consumption. (Here ‘DIN’ is the sum of ammonium, nitrite and nitrate.) After ∼30 days a quasi steady state was reached. Non-linear interactions between the two types of OM were reflected by three main differences between the early-diagenetic evolutions of nitrogen dynamics of the mixture and sum (control) systems: (1) In the mixture system the phases of net DIN production and consumption commenced more rapidly and were more intense. (2) The mixture system was shifted towards a more oxidised state of DIN products [as indicated by increased (nitrite+nitrate)/(ammonium) ratios]. (3) There was some evidence that more OM, POC and particulate nitrogen were preserved in the mixture system. That is, in the mixture system more particulate OM was preserved while a higher proportion of the decomposed particulate N was converted into inorganic N. It can be concluded that during the first days and weeks of early diagenesis the magnitude and composition of the flux of decompositional dissolved N-compounds from sediments into the overlying water was influenced by non-linear interactions of OM substrates of different degradability. Given these experimental results it is likely that the relative spatial distributions of OM of differing degradability in sediments control the magnitude and composition of the return flux of dissolved N-bearing compounds from sediments into the overlying water column. [Copyright &y& Elsevier]

Abstract: A method based on the peak obtained by adsorptive stripping voltammetry for the complex formed by organic matter in the presence of trace amounts of molybdenum(VI) has been tested for the determination of refractory organic matter, the so-called humic substances, in freshwaters. The method is rapid and particularly well-adapted to the determination of low amounts of refractory organic matter. It has a detection limit of 2.4μgCL−1 for 3min deposition time. The effect of the presence of other types of natural organic matter has been tested. The method has been applied to a wide variety of freshwaters at different trophic states. [Copyright &y& Elsevier]

Leachates produced at the La Zoreda landfill in Asturias, Spain, were recirculated through a simulated landfill pilot plant. Prior to recirculation, three loads of different amounts of Municipal Solid Waste (MSW) were added to the plant, forming in this way consecutive layers. When anaerobic digestion was almost completed, the leachates from the landfill were recirculated. After recirculation, a new load of MSW was added and two new recirculations were carried out. The organic load of the three landfill leachates recirculated through the anaerobic pilot plant decreased from initial values of 5108, 3782 and 2560 mg/l to values of between 1500 and 1600 mg/l. Despite achieving reductions in the organic load of the leachate, a residual organic load still remained that was composed of non-biodegradable organic constituents such as humic substances. Similar values of the chemical oxygen demand (COD) were obtained when the landfill leachate was treated by a pressurised anoxic–aerobic process followed by ultrafiltration. After recirculation through the pilot plant, physico-chemical treatment was carried out to reduce the COD of the leachate. The pH of the leachate was decreased to a value of 1.5 to precipitate the humic fraction, obtaining a reduction in COD of about 13.5%. The supernatant liquid was treated with activated carbon and different resins, XAD-8, XAD-4 and IR-120. Activated carbon presented the highest adsorption capacities, obtaining COD values for the treated leachate in the order of 200 mg/l. Similar results were obtained when treating with activated carbon, the leachate from the biological treatment plant at the La Zoreda landfill; in this case without decreasing the pH. [Copyright &y& Elsevier]