Linkages between soil microbial stability and carbon storage in the active layer under permafrost degradation

The Qinghai-Tibet Plateau(QTP)distributes the largest extent of high-altitude mountain permafrost in the world(Zou et al.,2017),which has different characteristics from high-latitude permafrost(Yang et al.,2010)and stores massive soil carbon.

Lindane Degradation and Effects on Soil Microbial Activity

The degradation of U-14C-lindane in two Egyptian soils was determined in a three-month laboratory incubation. Lindane mineralization was slow and limited in both soils. Evolution of 14CO2 increased with time but only reached 3. 5 to 5. 5 % of the initial 14C-concentration within 90 days. At that time both soils contained about 88 % of the applied radiocarbon; 33 % to 37% of the initial dose was unextractable and assumed bound to the soils. The methanol-ex-tractable 14C primarily contained lindane with traces of minor metabolites. Radiorespirometry was used to eva1uate the effect of lindane on soil microbial activity. Low concentrations of the insecticide initially supressed 14CO2 evolution from U-14C-glucose and microbial activity was significantly inhibited by 10 mg lindane/kg soil.

Sonocatalytic activity of LuFeO_3 crystallites synthesized via a hydrothermal route

LuFeO3 crystallites of different sizes and morphologies were synthesized via a hydrothermal route. The sonocatalytic properties of the as-synthesized samples were investigated by degrading various organic dyes, including acid orange 7 （AOT）, rhodamine B （RhB）, methyl orange （MO）, and methylene blue （MB）, under ultrasonic irradiation, revealing that they exhibit excellent sonocatalytic activity toward the degradation of these dyes. Particularly, the synthesized bar-like particles with lengths of-3 μm and widths of-1μm have the highest sonocatalytic activity, and the degradation percentage of AO7 reaches 89% after 30 min of sonocatalysis. The effects of inorganic anions such as CI-, NO3-, SO42-, PO43-, and HCO3- on the sonocatalysis efficiency were investigated. Hydroxyl radicals （·OH） detected by fiuorimetry using terephthalic acid as a probe molecule were found to be produced over the ultrasonic-irradiated LuFeO3 particles. The addition of ethanol, which acts as a· OH scavenger, leads to quenching of ＂OH radicals and a simultaneous decrease in the dye degrada- tion. This suggests that ＂OH is the dominant active species responsible for the dye degradation.

Spatio-temporal patterns of satellite-derived grassland vegetation phenology from 1998 to 2012 in Inner Mongolia, China

Spatio-temporal variations of vegetation phenology, e.g. start of green-up season（SOS） and end of vegetation season（EOS）, serve as important indicators of ecosystems. Routinely processed products from remotely sensed imagery, such as the normalized difference vegetation index（NDVI）, can be used to map such variations. A remote sensing approach to tracing vegetation phenology was demonstrated here in application to the Inner Mongolia grassland, China. SOS and EOS mapping at regional and vegetation type（meadow steppe, typical steppe, desert steppe and steppe desert） levels using SPOT-VGT NDVI series allows new insights into the grassland ecosystem. The spatial and temporal variability of SOS and EOS during 1998–2012 was highlighted and presented, as were SOS and EOS responses to the monthly climatic fluctuations. Results indicated that SOS and EOS did not exhibit consistent shifts at either regional or vegetation type level; the one exception was the steppe desert, the least productive vegetation cover, which exhibited a progressive earlier SOS and later EOS. Monthly average temperature and precipitation in preseason（February, March and April） imposed most remarkable and negative effects on SOS（except for the non-significant impact of precipitation on that of the meadow steppe）, while the climate impact on EOS was found to vary considerably between the vegetation types. Results showed that the spatio-temporal variability of the vegetation phenology of the meadow steppe, typical steppe and desert steppe could be reflected by the monthly thermal and hydrological factors but the progressive earlier SOS and later EOS of the highly degraded steppe desert might be accounted for by non-climate factors only, suggesting that the vegetation growing period in the highly degraded areas of the grassland could be extended possibly by human interventions.

Degradation of platinum electrocatalysts for methanol oxidation by lead contamination

Platinum exhibits high electrocatalytic activity toward various reactions but might be poisoned by some species. This communication reports a new finding that the electrocatalytic activity of platinum for methanol oxidation will be largely lost in a lead-contaminated environment. This activity loss is demonstrated in an electrochemical cell using a lead counter electrode for measuring the activity of platinum electrode towards methanol oxidation. The recorded methanol oxidation current in this cell is significantly decreased compared with that using a platinum counter electrode. The possible mechanism is related to the adsorption of trace lead ions from the lead counter electrode, as confirmed by comparing the calculated binding energies of platinum and lead ions with oxygen ion. This report is of great importance for reliably designing and efficiently managing direct methanol fuel cells, because trace lead might be present in various components in the fuel cell systems or in air and attention should be paid to its negative effect.

Immobilization of TiO_2 nanoparticles on activated carbon fiber and its photodegradation performance for organic pollutants

The immobilization of titanium dioxide （TiO2） on activated carbon fiber （ACF）, （TiO2/ACF）, was accomplished by sol-gel-adsorption method followed by calcination at temperatures varying from 300 to 600℃ in an argon atmosphere. The material properties were determined by scanning electron microscope （SEM）, X-ray diffraction （XRD） and nitrogen adsorption. The photodegradation behavior of TiO2 /ACF was investigated in aqueous solutions using phenol and methyl orange （MO） as target pollutants. The effects of calcination temperature, photocatalyst dosage, initial solution pH and radiation time on the degradation of organic pollutants were studied. It was found that organic pollutants could be removed rapidly from water by the TiO2/ACF photocatalyst and the sample calcined at 500℃ exhibited the highest removal efficiency. Kinetics analysis showed that the photocatalytic degradation reaction can be described by a first-order rate equation. In addition, the possibility of cyclic usage of the photocatalyst was also confirmed. Moreover, TiO2 is tightly bound to ACF and can be easily handled and recovered from water. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.

Thermo-oxidative degradation of Nylon 1010 films:Colorimetric evaluation and its correlation with material properties

The thermo-oxidative aging behaviors of Nylon 1010 films were studied by various analytical methods,such as measuring the chromaticity,relative viscosity,carbonyl index,UV absorbance at 280 nm and elongation at break of the aged films.The thermo-oxidative aging plots of the results obtained via these various methods at different temperatures are subjected to the time-temperature superposition analysis,which are found to be well superposed.The b＊ values are used as X axis and the other results,i.e.,relative viscosity,carbonyl index,UV absorbance at 280 nm and elongation at break,are used as V axis,respectively.The relationship between the b values and the other results is obtained,from which we can derive the changes of physical and chemical properties at different b＊ values.Since the b＊ values can be quickly determined by using a portable spectrophotometer,the on-line evaluation of the thermo-oxidative aging of Nylon 1010 can be realized.

End-life Prediction of Commercial PLA Used for Food Packaging through Short Term TGA Experiments: Real Chance or Low Reliability?

A long-term （about nine months） isothermal degradation experiment of two different commercial polylactide （PLA） samples used for food packaging was carried out at a relatively low temperature （423 K）. Thermooxidative degradations of the same polymers were carried out in a thermogravimetric （TG） analyser, at higher temperatures （453 K 〈 T 〈 523 K）, under isothermal heating conditions. The obtained set of experimental TG data was used to determine the apparent activation energy （Ea） of degradation through two isothermal kinetic methods. The results from long-term experiment evidenced considerable mass loss for both PLA samples in the investigated period, but the experimental data were not in agreement with those from the short-term degradations at higher temperatures, thus suggesting a different degradation kinetics, and, then a low reliability of the lifetime predictions for polymers in service or degradation forecasts for the end of their life based on experiments at higher temperatures.

Reaction mechanism of dicofol removal by cellulase

It remains unclear whether dicofol should be defined as a persistent organic pollutant. Its environmental persistence has gained attention. This study focused on its degradation by cellulase. Cellulase was separated using a gel chromatogram, and its degradation activity towards dicofol involved its endoglucanase activity. By analyzing the kinetic parameters of cellulase reacting with mixed substrates, it was shown that cellulase reacted on dicofol and carboxyl methyl cellulose through two different active centers. Thus, the degradation of dicofol was shown to be an oxidative process by cellulase. Next, by comparing the impacts of tert-butyl alcohol（a typical OH free-radical inhibitor） on the removal efficiencies of dicofol under both cellulase and Fenton reagent systems, it was shown that the removal of dicofol was initiated by OH free radicals produced by cellulase. Finally, 4,4′-dichlorodibenzophenone and chloride were detected using gas chromatography mass spectrometry and ion chromatography analysis, which supported our hypothesis. The reaction mechanism was analyzed and involved an attack by OH free radicals at the orthocarbon of dicofol, resulting in the degradation product 4,4′-dichloro-dibenzophenone.