Abstract  A small-scale flow-through limestone column was used to evaluate the effect of common coexisting organic and inorganic compounds on the electrochemical dechlorination of trichloroethylene (TCE) in karst media. Iron anode was used to produce ferrous ions and promote reducing conditions in the column. The reduction of TCE under 90 mA current, 1 mL min-1 flow rate, and 1 mg L-1 initial TCE concentration, was inhibited in the presence of humic acids due to competition for direct electron transfer and/or reaction with atomic hydrogen produced at the cathode surface by water electrolysis. Similarly, presence of 10 mg L-1 chromate decreased TCE reduction rate to 53%. The hexavalent chromium was completely reduced to trivalent chromium due to the ferrous species produced from iron anode. Presence of 5 mg L-1 selenate decreased the removal of TCE by 10%. Chromium and selenate complexation with dissolved iron results in formation of aggregates, which cover the electrodes surface and reduce TCE dechlorination rate. Presence of 40 mg L-1 nitrates caused reductive transformation of TCE up to 80%. Therefore, TCE removal is influenced by the presence of other contaminants that are present as a mixture in groundwater in the following order: humic acid, chromate, selenate, and nitrate.

Abstract  Sewage sludge was amended with calcium-based bentonite with addition of no more than 10% in dry weight during the 52-day aerobic composting process, the variations of temperature, pH, organic carbon, EC, total nitrogen, nitrate(NH4+-N) and ammonium(NO3--N) were investigated, as well as the compost detoxification(germination test), heavy metals(Zn, Cu, Pb, Cd) passivation and estrone(E1) elimination. The results showed that the amendment facilitated the thermophilic phase, promoted the compost heat inactivation and brought the organic carbon mineral up to more than 15.27% -19.71%. During the composting, the compost pH increased at the beginning and then gradually decreased before reaching values of 6.76-7.05, while the amendments alleviated the dramatic pH value fluctuation. The bentonite amendment reduced the salinity of the compost with final product EC remarkably lower than 1132 μS·cm-1 of the control treatment, and the effect was enhanced with the increase of addition amount. The total nitrogen content increased with time, and there was a remarkable ammonia loss in the beginning stage for the control treatment, while the bentonite addition could facilitate the total nitrogen content increase by reducing the ammonia loss. With the composting variation, the contents of NH4+-N increased and then decreased while the NO3--N content increased gradually. The bentonite addition had a slight inhibitory effect on the plant germination but did not influence the compost maturity and detoxification; meanwhile, the amendment improved the heavy metal passivation and reduced the E1 content, especially from 90.48 to 28.27 μg·kg-1 with 5% treatment during the composting. The study indicated that bentonite addition of lower than 5% was acceptable for the sludge compost amendment, which had great potential in sludge hygienization, detoxification, heavy metal passivation and E1 elimination.

Abstract  The C4 grass Spartina alterniflora is known for its unique salt tolerance and strong preference for ammonium (NH4+) as a nitrogen (N) source. We here examined whether Spartina's unique preference for NH4+ results in improved performance under drought stress. Manipulative greenhouse experiments were carried out to measure the effects of variable water availability and inorganic N sources on plant performance (growth, photosynthesis, antioxidant, and N metabolism). Drought strongly reduced leaf number and area, plant fresh and dry weight, and photosynthetic activity on all N sources, but the reduction was most pronounced on NH4+. Indeed, the growth advantage seen on NH4+ in the absence of drought, producing nearly double the biomass compared to growth on NO3-, was entirely obliterated under both intermediate and severe drought conditions (50 and 25% field capacity, respectively). Both fresh and dry weight became indistinguishable among N sources under drought. Major markers of the antioxidant capacity of the plant, the activities of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase, showed higher constitutive levels on NH4+. Catalase and glutathione reductase were specifically upregulated in NH4+-fed plants with increasing drought stress. This upregulation, however, failed to protect the plants from drought stress. Nitrogen metabolism was characterized by lower constitutive levels of glutamine synthetase in NH4+-fed plants, and a rise in glutamate dehydrogenase (GDH) activity under drought, accompanied by elevated proline levels in leaves. Our results support postulates on the important role of GDH induction, and its involvement in the synthesis of compatible solutes, under abiotic stress. We show that, despite this metabolic shift, S. alterniflora's sensitivity to drought does not benefit from growth on NH4+ and that the imposition of drought stress equalizes all N-source-related growth differences observed under non-drought conditions.

Abstract  The continuous flow reactor was used to treat simulated ammonia nitrogen wastewater by inoculating the sludge after filtration and adding a suspended filler. Regulations of free ammonia (FA), free nitrous acid (FNA), and dissolved oxygen (DO) in the reactor were the key to achieving a successful start-up of the pilot scale nitrosation reactor. The results show that the enrichment of ammonium oxidizing bacteria (AOB) and the elimination of nitrite oxidizing bacteria (NOB) are achieved by adjusting the operational mode of high DO, low DO, FA, and FNA in the reactor operation. The nitrite production rate (NPR) in the reactor was 1.27 kg·(m3·d)-1 and the nitrogen accumulation rate (NAR) was stable at 98% at the end of the start-up period. qPCR was used to study the difference in the functional microorganisms (AOB, NOB) between the beginning and the end of the start-up period. The results show that the copy number of microbial AOB grew from 5.3×109 copies·mL-1 to 1.6×1011 copies·mL-1. The copy number of NOB decreased from 1.1×1010 copies·mL-1 to 1.2×109 copies·mL-1, because of the joint regulation of DO, FA, FNA to suppress NOB.

Abstract  Carbon and nitrogen in soils play an important role in the global carbon and nitrogen cycle. The enhancement of ultraviolet radiation (predominantly UV-B) resulting from the depletion of stratospheric ozone has raised significant concern. The effects of UV-B radiation on soil carbon and nitrogen transformation is connected directly to the physical and chemical properties of the soil. In order to clearly understand the effects of soil moisture on UV-B radiation, this study collected soil samples from two paddy fields with different levels of organic matter in a subtropical region of China. The response of the total organic carbon (TOC), dissolved organic carbon (DOC), ammonia nitrogen (NH4+ -N), nitrate nitrogen (NO3- -N) and cumulative net nitrogen mineralization to UV-B radiation under three different moisture gradients (W1=25%, W2=50%, and W3=100%) were monitored in laboratory for 120 h. After this period, the results were compared with a control treatment (CK) and it was found that:the TOC content had significantly decreased under UV-B radiation (p<0.05). From low to high moisture content (W1, W2 and W3), the TOC decreased by 9.9%, 4.5% and 6.3%, respectively for soil with low organic matter (L), and by 10.9%, 5.6% and 6.3%, respectively for soil with high organic matter (H), under UV-B radiation. However, UV-B radiation was found to enhance the DOC content in the soil compared with the CK. Furthermore, the DOC for soil moisture contents under 100% (W3) was higher than for other moisture contents (W1, W2). The measured DOC increased by 21.5% (W1), 9.4% (W2), and 26.3% (W3) for soil with L. In addition, the measured DOC increased by 26.7% (W1), 14.2% (W2) and 33.8% (W3) for soil with H under UV-B radiation after 120 h. Compared with control treatment (CK), UV-B radiation decreased the NH4+ -N content significantly, but there was an increased NO3- -N content. The decrease of the NH4+ -N content was largest for W3 and smallest for W1. The increase in NO3- -N content was largest for W2 and smallest for W1 for the two soil samples under UV-B radiation. UV-B radiation demonstrated an obvious effect on the cumulative net nitrogen mineralization (p<0.05) after 24 h compared with the CK and the effect of different soil moisture treatment was also significant (p<0.05). Overall, light degradation played a major role in the stabilization of soil organic matter, soil moisture, and UV-B radiation could accelerate the loss of soil organic carbon and has a major impact on the transformation of mineral nitrogen in the soil. Therefore, in agricultural production systems, completely bare surfaces should be avoided. For example, paddy rice-upland crop rotation systems could reduce the use of fallow periods.

Abstract  Stabilisation of ammoniacal nitrogen from solid waste and leachate significantly improved by combining novel processes like SHARON (single reactor system for high activity ammonia removal over nitrite) and ANAMMOX (anaerobic ammonium oxidation) with advantages of lower carbon requirements, aeration and N2O emissions. This paper deals with establishing combined SHARON-ANAMMOX processes in situ pilot-scale landfill bioreactors (LFBR). Molecular analysis in LFBR with changes in nitrogen, hydrazine, hydroxylamine confirmed aerobic and anaerobic ammonium oxidising bacteria (AOB & ANAMMOX) as key players in SHARON-ANAMMOX processes. In situ SHARON-ANAMMOX process was established in LFBR with total nitrogen and ammoniacal nitrogen removal efficiency of 84% and 71%, respectively at NLR of 1.2 kgN/m3/d in 147 d, compared to ammoniacal nitrogen removal of 49% at NLR of 1.0 kgNH4-N/m3/d in 336 d feasible in Control LFBR. Nitrogen massbalance demonstrated in situ SHARON-ANAMMOX advantageous than control LFBR with higher nitrogen transformation to N2 (50.8%) and lower residual nitrogen in solid waste (7.7%).

Abstract  Methanotrophic based process can be the remedy to offset the wastewater treatment facilities increasing energy requirements due to methanotroph's unique ability to integrate methane assimilation with multiple biotechnological applications like biological nitrogen removal and methanol production. Regardless of the methanotrophic process end product, the challenge to maintain stable microbial growth in the methanotrophs cultivation bioreactor at higher cell densities is one of the major obstacles facing the process upscaling. Therefore, a series of consecutive batch tests were performed to attentively investigate the biomass density influence on type I methanotrophs bacterial growth. In addition, food to microorganisms (F/M), carbon to nitrogen (C/N) and nitrogen to microorganisms (N/M) ratio effect on the microbial activity was studied for the first time. It was clarified that the F/M ratio is the most influencing factor on the microbial growth at higher biomass densities rather than the biomass density increase, whereas C/N and N/M ratio change, while using nitrate as the nitrogen source, does not influence methanotrophs microbial growth. These study results would facilitate the scaling up of methanotrophic based biotechnology by identifying that F/M ratio as the key parameter that influences methanotrophs cultivation at high biomass densities.

Abstract  Photocatalytic reduction of aqueous nitrate has been thoroughly studied over noble metals doped and pristine TiO2 synthesized by a customized single step microwave assisted hydrothermal method. The synthesized catalysts are systematically characterized using XRD, Raman spectroscopy, FE-SEM, HR-TEM, XPS, diffuse reflectance spectroscopy, and PL measurements. The characterization reveals the successful synthesis of highly crystalline doped and undoped nano-TiO2. The photocatalytic rate of aqueous nitrate reduction over undoped TiO2 is found to be higher than that of noble metal doped TiO2. Mechanistic studies of the photocatalytic reduction are carried out with the help of different hole (oxalic acid, and methanol) and electron (sodium persulfate) scavengers, which reveal that the photogenerated electrons are the primary agents toward efficient nitrate photoreduction. Detailed studies have revealed that the noble metal doping in TiO2 helps in efficient photogeneration of H-2 compared to the undoped analogue, however, the in situ produced H-2 is found to be inefficient in reducing NO3-. The conduction band position from first principle calculations with respect to the nitrate and hydrogen reduction potentials derived from cyclic voltammetry provide insights to the electron transfer process in determining the reaction pathway.

Abstract  Internet of things is one of the rapidly growing fields for delivering social and economic benefits for emerging and developing economy. The field of IOT is expanding its wings in all the domains like medical, industrial, transportation, education, mining etc. Now-a-days with the advancement in integrated on chip computers like Arduino, Raspberry pi the technology is reaching the ground level with its application in agriculture and aquaculture. Water quality is a critical factor while culturing aquatic organisms. It mainly depends on several parameters like dissolved oxygen, ammonia, pH, temperature, salt, nitrates, carbonates etc. The quality of water is monitored continuously with the help of sensors to ensure growth and survival of aquatic life. The sensed data is transferred to the aqua farmer mobile through cloud. As a result preventive measures can be taken in time to minimize the losses and increase the productivity.

Abstract  Effects of four amino acids, L-asparagine, L-cysteine, L-citrulline, and L-glutamine in different concentrations (0, 0.5, 1, and 2 mg dm(-3)) combined with 2 mg dm(-3) indole-3-butyric acid, on in vitro rooting and biochemical constituents of cherry rootstocks CAB-6P (Prunus cerasus L.) and Gisela 6 (P. canescens x P. cerasus) were investigated. In CAB-6P, root number and root fresh mass (FM) were maximum at 0.5 mg dm(-3) cysteine. All amino acids reduced root length in CAB-6P and root number as well as root FM in Gisela 6. In Gisela 6, 0.5 mg dm(-3) asparagine or 2 mg dm(-3) glutamine reduced root length. In CAB-6P, 100 % rooting was achieved in the control and with 1 and 2 mg dm(-3) cysteine or 1 mg dm(-3) citrulline. In Gisela 6, the rooting percentage was maximum (76.92 %) with 0.5 mg dm(-3) asparagine. Callus FM in CAB-6P was the greatest at 1 mg dm(-3) and in Gisela 6 at 2 mg dm(-3) citrulline. Callusing was 100 % in the majority of treatments for CAB-6P and 92.31 % for Gisela 6 with 0.5 or 2 mg dm(-3) citrulline. Cysteine, citrulline, and glutamine diminished chlorophyll content in Gisela 6 whereas in CAB-6P all four amino acids hardly affected it. Carotenoid and porphyrin content in CAB-6P was decreased due to asparagine (0.5 or 1 mg dm(-3)). Porphyrin content in CAB-6P was also reduced by adding 0.5 or 1 mg dm(-3) cysteine or 2 mg dm(-3) citrulline. In Gisela 6, all amino acids decreased carotenoid and porphyrin content. In CAB-6P, all treatments except 0.5 mg dm(-3) glutamine or 2 mg dm(-3) asparagine increased leaf sucrose content. In roots, both sucrose and proline content were increased only at 1 mg dm(-3) cysteine whereas in leaves only 0.5 mg dm(-3) asparagine caused a 3-fold increase in proline content. A decrease in root proline in CAB-6P was observed due to asparagine, citrulline, or glutamine. In Gisela 6, decreased leaf sucrose and proline content was recorded at 2 mg dm(-3) cysteine. All amino acids did not alter root sugar content remarkably whereas root proline content was raised by adding 0.5 mg dm(-3) glutamine or 1 mg dm(-3) cysteine.

Abstract  The present investigation describes interactions between Cyanex 923 and benzene/xylene at 300 K. The experimental values of molar volume, dielectric constant, refractive index, molar polarisation and molar refraction of pure Cyanex 923, benzene and xylene and their binary mixture over the entire mole fraction range have been determined. The excess parameters, Kirkwood correlation parameter, Gibb's free energy of mixing for these binary mixtures have been evaluated. The excess parameters have been tested using Redlich-Kister equation. The results indicate very weak interactions between Cyanex 923 and benzene/xylene. (C) 2016 Elsevier B.V. All rights reserved.

Abstract  The photocatalytic degradation of isoproturon, a persistent toxic herbicide, was investigated in the presence of natural iron oxide and oxalic acid and under UV irradiation. The influence of the relevant parameters such as the pH and the iron oxide and oxalic acid concentrations has been studied. The presence of natural iron oxide and oxalic acid in the system effectively allow the degradation of isoproturon, whereas the presence of t-butyl alcohol adversely affects the phototransformation of the target pollutant, thus indicating that an OH radical initiated the degradation mechanism. The degradation mechanism of isoproturon was investigated by means of GC-MS analysis. Oxidation of both the terminal N-(CH3)2 and isopropyl groups is the initial process leading to N-monodemethylated (NHCH3), N-formyl (N(CH3)CHO), and CHCH3OH as the main intermediates. The substitution of the isopropyl group by an OH group is also observed as a side process.

Abstract  Sludge production is an undesirable by-product of biological wastewater treatment. The oxic-settling-anaerobic (OSA) process constitutes one of the most promising techniques for reducing the sludge produced at the treatment plant without negative consequences for its overall performance. In the present study, the OSA process is applied in combination with ultrasound treatment, a lysis technique, in a lab-scale wastewater treatment plant to assess whether sludge reduction is enhanced as a result of mechanical treatment. Reported sludge reductions of 45.72% and 78.56% were obtained for the two regimes of combined treatment tested in this study during two respective stages: UO1 and UO2. During the UO1 stage, the general performance and nutrient removal improved, obtaining 47.28% TN removal versus 21.95% in the conventional stage. However, the performance of the system was seriously damaged during the UO2 stage. Increases in dehydrogenase and protease activities were observed during both stages. The advantages of the combined process are not necessarily economic, but operational, as US treatment acts as contributing factor in the OSA process, inducing mechanisms that lead to sludge reduction in the OSA process and improving performance parameters.

Abstract  Ammonia-oxidizing marine archaea (mAOA) have been divided into two groups based on ammonia monooxygenase subunit A gene (amoA) phylogeny and they link to preferred habitat (depth in the water column); one is the Shallow Marine Clade (SMC) and the other is the Deep Marine Clade (DMC). Several determinative factors have been proposed to account for their depth-dependent distributions, including light intensity, ammonia concentration, water temperature, and dissolved oxygen concentration. Here, we report the change in abundance of SMC and DMC mAOA in response to nitrogen source and water temperature in a long-term incubation experiment using natural seawaters obtained from mesopelagic and bathypelagic layers. The abundance of each type of mAOA was determined by Q-PCR assay targeting amoA. We found that the abundance of SMC after 266 days of incubation increased at all three incubation temperatures (4, 10, 20 degrees C), whereas the abundance of DMC was stable at low temperatures (4 degrees C and sometimes 10 degrees C) or decreased to below the detection limit at high temperatures (20 degrees C and sometimes 10 degrees C). The SMC abundance was higher in seawater cultures supplied with ammonium than in those supplied with nitrite, although DMC abundance was not responsive to ammonium concentration. These results imply that water temperature and ammonia concentration are significant factors in determining the vertical distribution of the SMC and DMC ecotypes of mAOA in the water column.

Abstract  Two types of nanofiltration membranes were tested to remove uranium dissolved in ammonium nitrate solution, and the influence of operating parameters as transmembrane pressure, tangential velocity and feed temperature was investigated. Experimental results showed NF270 membrane can reject more than 96 % uranium and allow most (90 % min) ammonium nitrate solution passed by, and with a permeate flux of 60 L/(m(2) . h). Nanofiltration seems to be a promising technology for the removal of uranium and recovery of ammonium nitrate simultaneously.

Abstract  In this study, a simulated ammonium diuranate filtrate (ADUF) which was obtained by adding uranyl nitrate to a 35 g/L ammonium nitrate solution to adjust the uranium concentration to about 50 mg/L was treated by a nanofiltration process. Experiments were carried out on a plate membrane testing device with a trans-membrane pressure (TMP) range of 0.5 similar to 3.0 MPa, a crossflow velocity range of 10 similar to 50 cm/s and a temperature range of 5 similar to 35 degrees C. The results show that NF270 membrane has good rejection property for uranium and excellent permeability for ammonium nitrate. The ammonium nitrate concentration in the permeate is about 32 g/L which means the reject ratio of ammonium nitrate is only about 10%. Though NF270 membrane shows good uranium rejection property, the corresponding permeate flux is very high. When the trans-membrane pressure is 1.5 MPa, the uranium reject ratio is 96.8% and the the corresponding permeate flux is about 80 L/(m(2).h). It indicates a bright application prospect of nanofiltration process in the treatment of ADUF.

Abstract  In this study, an electrochemical/electro-Fenton oxidation (EC/EF) system was designed to degrade atrazine, by utilizing boron-doped diamond (BDD) and Fe@Fe2O3core-shell nanowires loaded active carbon fiber (Fe@Fe2O3/ACF) as the anode and the cathode, respectively. This EC/EF system exhibited much higher degradation rate, decholorination and mineralization efficiency of atrazine than the electrochemical (EC) and electrochemical/traditional electro-Fenton (EC/TEF) oxidation counterpart systems without Fe@Fe2O3core-shell nanowires. Active species trapping experiment revealed that Fe@Fe2O3could activate molecular oxygen to produce more OH through Fenton reaction, which favored the atrazine degradation. High performance liquid chromatography, high performance liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry were applied to probe the decomposition and mineralization of atrazine during this novel EC/EF process, which revealed that two intermediates of triazinons (the isomerization of hydroxylated atrazine) were generated during the electrochemical/electro-Fenton oxidation of atrazine in the presence of Fe@Fe2O3core-shell nanowires. The experimental and theoretical calculation results suggested that atrazine might be degraded via a triazinon ring opening mechanism, while the presence of Fe@Fe2O3notably accelerated the decholorination process, and produced more hydroxylated products to promote the generation of trazinons and the subsequent ring cleavage as well as the final complete mineralization. This work provides a deep insight into the triazine ring opening mechanism and the design of efficient electrochemical advanced oxidation technologies (EAOTs) for persistent organic pollutant removal.

Abstract  A thorium oxide nuclear fuel cycle should be one of the promising options in the current U-Pu cycle conducted in most countries utilizing the nuclear energy. To make this fuel cycle more reasonable, it is still necessary to innovate the reprocessing method of the spent ThO2 fuels. In accordance with our former development of a selective precipitation method for the spent UO2 fuel reprocessing, its basic technology can also be applied to the spent ThO2 fuel reprocessing. Prior to the molecular design of N substituted 2-pyrrolidone precipitants (NRPs), differences in the conditions of these spent fuel reprocessing processes especially for the concentrations of U(VI) and other relevant species were indicated. On this context, the demands in the spent ThO2 fuel reprocessing and requirements for the U(VI)-selective precipitant were summarized. Consequently, a confliction between the requirements arising from the fundamental conditions in the spent ThO2 fuel reprocessing has appeared. To overcome this situation, a structural motif of a double-headed NRP (DHNRP) was proposed as a new concept for molecular design of NRPs expected to be employed in the spent ThO2 fuel reprocessing. Accessibility of DUNRPs was successfully demonstrated by preparation of several compounds which follow this molecular design concept. (C) 2017 The Authors. Published by Elsevier Ltd.

Abstract  OBJECTIVE: To increase understanding of the biological mechanisms underlying the association, we investigated the individual relations to cognitive decline of the primary nutrients and bioactives in green leafy vegetables, including vitamin K (phylloquinone), lutein, β-carotene, nitrate, folate, kaempferol, and α-tocopherol.

METHODS: This was a prospective study of 960 participants of the Memory and Aging Project, ages 58-99 years, who completed a food frequency questionnaire and had ≥2 cognitive assessments over a mean 4.7 years.

RESULTS: In a linear mixed model adjusted for age, sex, education, participation in cognitive activities, physical activities, smoking, and seafood and alcohol consumption, consumption of green leafy vegetables was associated with slower cognitive decline; the decline rate for those in the highest quintile of intake (median 1.3 servings/d) was slower by β = 0.05 standardized units (p = 0.0001) or the equivalent of being 11 years younger in age. Higher intakes of each of the nutrients and bioactives except β-carotene were individually associated with slower cognitive decline. In the adjusted models, the rates for the highest vs the lowest quintiles of intake were β = 0.02, p = 0.002 for phylloquinone; β = 0.04, p = 0.002 for lutein; β = 0.05, p < 0.001 for folate; β = 0.03, p = 0.02 for α-tocopherol; β = 0.04, p = 0.002 for nitrate; β = 0.04, p = 0.003 for kaempferol; and β = 0.02, p = 0.08 for β-carotene.

CONCLUSIONS: Consumption of approximately 1 serving per day of green leafy vegetables and foods rich in phylloquinone, lutein, nitrate, folate, α-tocopherol, and kaempferol may help to slow cognitive decline with aging.

Abstract  Nitrate salt vapor deposition on the reflecting surface of a secondary concentrator placed on top of an open molten salt tank at 500 degrees C is investigated using a lab-scale setup over an 8h-exposure cycle. Deposition, consisting of mostly spherical particles, is characterized in terms of chemical composition using energy dispersive X-ray spectroscopy. The corresponding specular reflectance degradation both temporary (before washing off the salt deposits) and permanent (residual reflectance loss after cleaning), is measured at different incidence angles and at reference points located at different heights. Reflectance drop due to salt deposits is compared to the one resulting from dust deposition. Long-term reflectance degradation by means of corrosion needs to be further studied through suitable accelerated aging tests.

Abstract  There has been developed an approach to the production of graphene as a result of the thermal reduction of graphene oxide (GO). GO has been synthesized by the use of the modified Hummers method with utilization of sodium nitrate and concentrated sulfuric acid. A paper-like material of 40 - 60 mu m in thickness and 1.2 g/cm(3) in density was formed on a filter after deposition from dispersion. The material was cut onto samples of about 15x25 mm(2) in size which were experienced to the thermal treatment at various temperatures between 100 and 800 ... This resulted in a set of GO samples reduced to various degrees. The degree of reduction was determined on the basis of measurements of the conductivity. Along with that the evolution of samples density was studied as the annealing temperature was enhanced. The analysis of the X-ray photoelectron spectra of partially reduced GO permitted the determination of the dynamics of changing the chemical composition of the material in the process of the thermal treatment. The analysis of Raman spectra of the GO samples indicates rather high degree of the disordering of the material. A possibility of the usage of the material produced as a nanocarbon coating

Abstract  A novel, small-volume, strong cation-exchange column has been employed as an on-line pre-concentrator for samples introduced to the liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma. The column stationary phase was synthesized by a uniquemicrowave-assisted grafting of sulfonic acid groups onto nylon 6 capillary-channeled polymer (C-CP) fibers. The column material is robust with respect to attack in acidic sample media, with high permeability that obviates the need to use a high-pressure liquid chromatography pump. The column-loading flow rate, sample-load volume, and sample concentration were studied to demonstrate the utility of the column in improving the limits of detection (LOD) of silver in nitrate/nitric acid solutions. The eluted analyte signal intensity was found to be unaffected by column-loading flow rates from 100 to 800 mu L min(-1). When signal intensity was plotted against increasing sample-loading volumes and load concentrations, good linearity was observed (R-2 = 0.9939 and 0.9999). Overall, implementation of this novel column provides enhanced analytical performance for the LS-APGD-OES source with very minimal added experimental complexity. This is a key aspect as the microplasma is implemented on field-deployable platforms. It is imagined that the same fiber format could be easily adapted to larger size scales such as common to inductively-coupled plasma sources.

Abstract  It is globally accepted that soil carbon (C) dynamics are at the core of interlinked environmental problems, deteriorating soil quality and changing climate. Its management remains a complex enigma for the scientific community due to its intricate relationship with soil nitrogen (N) availability and moisture-temperature interactions. This article reviews the management aspects of soil C dynamics in light of recent advances, particularly in relation to the availability of inorganic N pools and associated microbial processes under changing climate. Globally, drastic alterations in soil C dynamics under changing land use and management practices have been primarily attributed to the variation in soil N availability, resulting in a higher decomposition rate and a considerable decline in soil organic C (SOC) levels due to increased soil CO2 emissions, degraded soil quality, and increased atmospheric CO2 concentrations, leading to climate warming. Predicted climate warming is proposed to enhance SOC decomposition, which may further increase soil N availability, leading to higher soil CO2 efflux. However, a literature survey revealed that soil may also act as a potential C sink, if we could manage soil inorganic N pools and link microbial processes properly. Studies also indicated that the relative, rather than the absolute, availability of inorganic N pools might be of key importance under changing climate, as these N pools are variably affected by moisture-temperature interactions, and they have variable impacts on SOC turnover. Therefore, multi-factorial studies are required to understand how the relative availability of inorganic N pools and associated microbial processes may determine SOC dynamics for improved soil C management.

Abstract  High frequency in-situ measurements of nitrate can greatly reduce uncertainty in nitrate flux estimates. Water quality databases maintained by various federal and state agencies often consist of pollutant concentration data obtained from periodic grab samples collected from gauged reaches of a stream. Regression models, such as the LOAD ESTimator (LOADEST), are frequently used to model variations in concentrations associated with changes in water discharge to provide integrated solute flux measurements. However, uncertainty in the relationships between nutrient concentration and flow may lead to errors in the corresponding flux estimates. In this study, a high frequency, in-situ measurement of nitrate concentration was implemented to ascertain uncertainty in the concentration/discharge relationship caused by nitrate hysteresis. It was found that observed nitrate hysteresis, as influenced by complex storm/watershed interactions, was not readily predictable. Therefore, it can lead to substantial nitrate flux uncertainty, based on periodic grab sample monitoring approaches. Scientists and engineers should take advantage of the proposed findings in future studies to enhance the quality of the associated decision making processes.

Abstract  The sun-photometer data from 2011 to 2013 at Panyu site (Panyu) and from 2007 to 2013 at Dongguan site (Dg) in the Pearl River Delta region, were used for the retrieving of the aerosol optical depth (AOD), single scattering albedo (SSA), Ångström exponent (AE) and volume size distribution of coarse- and fine-mode particles. The coarse-mode particles presented low AOD (ranging from 0.05±0.03 to 0.08±0.05) but a strong absorption property (SSA ranged from 0.70±0.03 to 0.90±0.02) for the wavelengths between 440 and 1020nm. However, these coarse particles accounted for <10% of the total particles. The AOD of fine particles (AODf) was over 3 times as large as that of coarse particles (AODc). The fine particles SSA (SSAf) generally decreased as a function of wavelength, and the relatively lower SSAf value in summer was likely to be due to the stronger solar radiation and higher temperature. More than 90% of the aerosols at Panyu site were dominated by fine-mode absorbing particles, whereas about 90% of the particles at Dg site were attributed to fine-mode scattering particles. The differences of the aerosol optical properties between the two sites are likely associated with local emissions of the light-absorbing carbonaceous aerosols and the scattering aerosols (e.g., sulfate and nitrate particles) caused by the gas-phase oxidation of gaseous precursors (e.g., SO2 and NO2). The size distribution exhibited bimodal structures in which the accumulation mode was predominant. The fine-mode volume showed positive dependence on AOD (500nm), and the growth of peak value of the fine-mode volume was higher than that of the coarse volume. Both the AOD and SSA increased with increasing relative humidity (RH), while the AE decreased with increasing RH. These correlations imply that the aerosol properties are greatly modified by condensation growth.