Comparative study of two carbon fiber cathodes and theoretical analysis in microbial fuel cells on ocean floor

Cathode activity plays an important role in the improvement of the microbial fuel cells on ocean floor(BMFCs). A comparison study between Rayon-based(CF-R) and PAN-based carbon fiber(CF-P) cathodes is conducted in the paper. The two carbon fibers were heat treated to improve cell performance(CF-R-H CF-P-H), and were used to build a new BMFCs structure with a foamy carbon anode. The maximum power density was 112.42 mW m-for CF-R-H, followed by 66.6 mW m-2 for CF-R, 49.7 mW m-2 for CF-P-H and 21.6 mW m-2 for CF-P respectively. The higher specific area and deep groove make CF-R have a better power output than with CF-P. Meanwhile, heat treatment of carbon fiber can improve cell power, nearly two-fold higher than heat treatment of plain fiber. This improvement may be due to the quinones group formation to accelerate the reduction of oxygen and electron transfer on the fiber surface in the three phase boundary after heat treatment. Compared to PAN-based carbon fiber, Rayon-based carbon fiber would be preferentially selected as cathode in novel BMFCs design due to its high surface area, low cost and higher power. The comparison research is significant for cathode material selection and cell design.     

Zn's role in dissolution of al sacrificial anodes

The role of alloying elements in the dissolution of aluminium sacrificial anodes was investigated. The effect of indium on the electrochemical performance of anode and the relationship between indium and impurities, such as silicon and iron, were studied. The distribution of indium in aluminium alloy was detected. The electrochemical behaviour of In-implanted aluminium alloy was also studied. The experimental results indicate that indium activates the surface of aluminium alloy and improves the electrochemical performance of alloy containing more amounts of impurity. Indium combines with silicon and iron. More satisfactory properties were obtained when the alloy's proportion of content of In to that of (Si+Fe) is about 1∶(8∼10). The electrochemical properties of Al alloy, especially the surface activity of the anode were improved by ion implantation. Indium segregates in the alloy. The amount of Si and Fe in the In-rich segregated phase is richer than that in the matrix. It is proposed that the In-rich segregated phase particles activate the surface and promote the dissolution process of the aluminium sacrificial anode.     

Oxidation Modification of Polyacrylonitrile-Based Carbon Fiber and Its Electro-Chemical Performance as Marine Electrode for Electric Field Test

A novel sensor for ocean electric field testing has been fabricated by polyacrylonitrile-based on carbon fibers with electro-chemical oxidation.The surface profile characteristics of the carbon fibers were characterized by scanning electron microscope,Fourier transform infrared spectra and contact angle.Cyclic voltammetry and Tafel curves have been used to study its electro-chemical performances.Two identical electrodes in sea water as the electric field sensor will swiftly respond to applied electric field which causes positive and negative ions to move in opposite direction,resulting in a electric potential difference(ΔE).Test result indicates that the offset potential is typically below 1 m V with a drift of 60-170μVd^-1.Typical self noise level is 1.07 nV√Hz^1/2@1 Hz.The electric field response indicates that the modified electrode pair shows better response to AC sine signal of amplitude and frequency(5 mV and 1 mHz)respectively than its blank.The electric field response model of the modified electrodes is creatively presented according to its electric double layer capacitance and Faraday pseudo-capacitance.Many advantages of the carbon fiber electric field electrode will make it have potential application prospect.     

Soil organic carbon contents,aggregate stability,and humic acid composition in different alpine grasslands in Qinghai-Tibet Plateau

Alpine grassland soils on Qinghai-Tibet Plateau store approximately 33.5 Pg of organic carbon(C) at 0–0.75 m depth and play an important role in the global carbon cycle.We investigated soil organic C(SOC),water-soluble organic C(WSOC),easily oxidizable organic C(EOC),humic C fractions,aggregate-associated C,aggregate stability,and humic acid(HA) composition along an east-west transect across Qinghai-Tibet Plateau,and explored their spatial patterns and controlling factors.The contents of SOC,WSOC,EOC,humic C fractions and aggregate-associated C,the proportions of macroaggregates(2-0.25) and micro-aggregates(0.25-0.053 mm),and the aggregate stability indices all increased in the order alpine desert alpine steppe alpine meadow.The alkyl C,O-alkyl C,and aliphatic C/aromatic C ratio of HA increased as alpine desert alpine meadow alpine steppe,and the trends were reverse for the aromatic C and HB/HI ratio.Mean annual precipitation and aboveground biomass weresignificantly correlated with the contents of SOC and its fractions,the proportions of macro- and microaggregates,and the aggregate stability indices along this transect.Among all these C fractions,SOC content and aggregate stability were more closely associated with humic C and silt and clay sized C in comparison with WSOC,EOC,and macro- and microaggregate C.The results suggested that alpine meadow soils containing higher SOC exhibited high soil aggregation and aggregate stability.Mean annual precipitation should be the main climate factor controlling the spatial patterns of SOC,soil aggregation,and aggregate stability in this region.The resistant and stable C fractions rather than labile C fractions are the major determinant of SOC stocks and aggregate stability.     

The apparent copper complexing capacity of seawater and the interaction of copper with humic matter

The anodic stripping voltammetry with physically-coating mercury film electrode was used to investigate the complexing action of trace heavy metals in seawater with organic ligands. The apparent copper complexing capacity of seawater was determined by titrating the organic ligands in natural seawater with standard ionic copper solution. The complexing actions of copper in seawater with humic acid (HA) or fulvic acid (FA) were investigated by titrating copper in seawater with HA or FA solution. The equilibrium time, electrodeposition potential, and effect of pH etc. were investigated respectively. The results show that the interaction of copper in seawater with organic matter is a fast process. At natural pH, HA or FA tend to act with copper in seawater to form nonlabile complexes. During experimental electrode process, these complexes did not significantly dissociate. The experimental results were calculated according to 1∶1 complex formation.     

ON THE DIVISION OF NORTH BOUNDARY OF SUBTROPICAL ZONE ACCORDING TO THE COMPOSITIONS AND PROPERTIES OF SOIL HUMUS

In this paper predecessorsˊ achievements about the division between subtropical zone and warm temperate zone on the south slope of Funiu Mountain are firstly summarized,and the cause why these viewpoints about the division are different also has been presented.Seven soil profiles at different heights above sea level are dug along the south slope of Funiu Mountain.Many compositions and properties of soil humus have been analyzed in laboratory.A comprehensive study has been made about the division according to the compositions and properties of soil humus with mathematical method.During the analysis process eitht indexes have been used,such as altitude,organic carbon,humic acid(HA),fulvic acid(FA),the ratio of humic acid and fulvic acid(HA/FA),two extinction coefficients(E4,E6), and their ratio (E4/E6).The result indicates that the boundary is at about 1000 meters above sea level.     

Purification and Characterization of a Novel Lipase from Antarctic Krill

Lipase from Antarctic krill,with a molecular weight of 71.27kDa,was purified with ammonium sulfate precipitation and a series of chromatographic separations over ion exchange(DEAE)and gel filtration columns(Sephacryl S-100),resulting in 5.2%recovery with a 22.4-fold purification ratio.The optimal pH and temperature for enzyme activity were 8.0 and 45℃,respectively.Purified lipase had Km and Vmax values of 3.27mmolL−1 and 2.4Umg−1,respectively,using p-nitrophenyl laurate as the substrate.Lipase activity was enhanced by adding Ca2+and Mg2+ions in the concentration ranges of 0–0.5mmolL−1 and 0–0.3mmolL−1,respectively,while the activity was inhibited by a further increase in these ion concentrations.Fe3+and Cu2+ions showed obvious inhibitory effects on enzyme activity,and the inhibition rates were 71.8%and 53.3%when the ion concentrations were 0.5mmolL−1.     

Study on Al-Zn-In Alloy as Sacrificial Anodes in Seawater Environment

Electrochemical properties including conventional electrochemical properties: open circuit potential, polarization potential, electrochemical capacity, morphology of surface dissolution, and the initial polarization properties of Al-Zn-In-Mg-Ti and Al-Zn-In-Si sacrificial anodes are investigated in the sea. The curves of anode output current and work potential with time, the impact of area ratio of cathode to anode on anode output current is discussed, and the initial polarization properties are investigated with cyclic voltammetry(CV) finally. The results show that for the two anodes, the current efficiency got in the sea environment is higher than the data of the 4-day-accelerated test in laboratory and the corrosion morphology is more uniform in the sea. With the same exposed area, the current efficiency of Al-Zn-In-Mg-Ti anode is higher than that of Al-Zn-In-Si in the sea. For both anodes, the current efficiency becomes larger with the increase of the area ratio of cathode to anode. The two anodes can output larger current in strong polarization state. The situation is consistent with the results that small area anode released higher current in the sea trial. The difference rests with that Al-Zn-In-Mg-Ti anode output far greater current than that of the Al-Zn-In-Si under the same polarization potential. The initial polarization property of the Al-Zn-In-Mg-Ti anode is better than Al-Zn-In-Si anode.     

光催化降解含乐果废水的研究

以半导体TiO2和自制复合型半导体Fe2O3/TiO2为催化剂对光催化降解乐果废水进行了研究.研究表明复合型光催化剂在可见光照下以及紫外光照下的活性都较好;而半导体TiO2只在紫外光照下才能降解乐果.控制催化剂TiO2的用量能提高对乐果的降解率.     

Bostick反演法误差修正

对于水平2层均匀介质模型,为提高Bostick反演法精度,推导希尔伯特变换近似所造成的误差公式,给出误差的数值计算方法,得到修正后的Bostick反演公式。对比2种方法反演结果发现,修正后的Bostick反演法能够更好地反映分界面及第2层介质的电阻率。     

A method for simulating sediment incipient motion varying with time and space in an ocean model(FVCOM):development and validation

We modified the sediment incipient motion in a numerical model and evaluated the impact of this modification using a study case of the coastal area around Weihai, China. The modified and unmodified versions of the model were validated by comparing simulated and observed data of currents, waves, and suspended sediment concentrations(SSC) measured from July 25~(th) to July 26~(th), 2006. A fitted Shields diagram was introduced into the sediment model so that the critical erosional shear stress could vary with time. Thus, the simulated SSC patterns were improved to more closely reflect the observed values, so that the relative error of the variation range decreased by up to 34.5% and the relative error of simulated temporally averaged SSC decreased by up to 36%. In the modified model, the critical shear stress values of the simulated silt with a diameter of 0.035 mm and mud with a diameter of 0.004 mm varied from 0.05 to 0.13 N/m~2, and from 0.05 to 0.14 N/m~2, respectively, instead of remaining constant in the unmodified model. Besides, a method of applying spatially varying fractions of the mixed grain size sediment improved the simulated SSC distribution to fit better to the remote sensing map and reproduced the zonal area with high SSC between Heini Bay and the erosion groove in the modified model. The Relative Mean Absolute Error was reduced by between 6% and 79%, depending on the regional attributes when we used the modified method to simulate incipient sediment motion. But the modification achieved the higher accuracy in this study at a cost of computation speed decreasing by 1.52%.     

Electrochemical properties of electrodes with different shapes and diffusion kinetic analysis of microbial fuel cells on ocean floor

Microbial fuel cell(MFC) on the ocean floor is a kind of novel energy-harvesting device that can be developed to drive small instruments to work continuously.The shape of electrode has a great effect on the performance of the MFC.In this paper,several shapes of electrode and cell structure were designed,and their performance in MFC were compared in pairs:Mesh(cell-1) vs.flat plate(cell-2),branch(cell-3) vs.cylinder(cell-4),and forest(cell-5) vs.disk(cell-6) FC.Our results showed that the maximum power densities were 16.50,14.20,19.30,15.00,14.64,and 9.95 mWm-2 for cell-1,2,3,4,5 and 6 respectively.And the corre-sponding diffusion-limited currents were 7.16,2.80,18.86,10.50,18.00,and 6.900 mA.The mesh and branch anodes showed higher power densities and much higher diffusion-limited currents than the flat plate and the cylinder anodes respectively due to the low diffusion hindrance with the former anodes.The forest cathode improved by 47% of the power density and by 161% of diffusion-limited current than the disk cathode due to the former’s extended solid/liquid/gas three-phase boundary.These results indicated that the shape of electrode is a major parameter that determining the diffusion-limited current of an MFC,and the differences in the elec-trode shape lead to the differences in cell performance.These results would be useful for MFC structure design in practical applica-tions.     

砂岩型铀矿成矿过程中腐殖酸的化学作用

研究表明,腐殖酸在铀成矿过程中的化学作用受多种因素制约,如pH值、温度和离子强度等。由于腐殖酸和富啡酸结构中的一些单元与一些小分子的芳香有机酸相似,因此,利用小分子的芳香有机酸来代替腐殖酸,研究不同条件下腐殖酸对铀成矿的影响,并获得了不同形式铀的配合物,证明了铀在含腐殖酸环境中的赋存状态。     

Photochemical production of dissolved inorganic carbon from suwannee river humic acid

The photochemical mineralization of dissolved organic carbon(DOC) to dissolved inorganic carbon(DIC) is a key process in carbon cycling.Using a Suntest CPS solar simulator,Suwannee River humic acid(SRHA) was photooxidated to examine the effects of O2 levels,the wavelength of incident light,and the concentration of Fe on the photoproduction of DIC.Increasing the O2 abundance enhanced photodegradation of SRHA.The rate of DIC photoproduction under air saturation in the first 24 h(4.40 μmol/(L h)) was increased...     

Effects of iron electrovalence and species on growth and astaxanthin production of Haematococcus pluvialis

To increase the cell concentration and the accumulation of astaxanthin in the cultivation of Haematococcus pluvialis, effects of different iron eleetrovalencies (Fe2+-EDTA and Fe3+-EDTA) and species (Fe-EDTA, Fe(OH)32x and FeC6H5O7) addition on cell growth and accumulation of astaxanthin were studied. Results show that different iron electrovalencies have various effects on cell growth and astaxanthin accumulation of H. pluvialis. Compared with Fe3+-EDTA, Fe2+-EDTA stimulate more effectively the formation of astaxanthin. The maximum astaxanthin content (30.70 mg/g biomass cell)was obtained under conditions of 18 μmol/L Fe2+-EDTA, despite the lower cell density (2.3x105 cell/ml)in such condition. Fe3+-EDTA is more effective than Fe2+-EDTA in improving the cell growth. Especially,the maximal steady-state cell density, 2.9x105 cell/ml was obtained at 18 μmol/L Fe3+-EDTA addition. On the other hand, all the various species of iron (EDTA-Fe, Fe(OH)32x, FeC6H5O7) are capable to improve the growth of the algae and astaxanthin production. Among the three iron species, FeC6H5O7 performed the best. Under the condition of a higher concentration (36 μmol/L) of FEC6H5O7, the cell density and astaxanthin production is 2 and 7 times higher than those of iron-limited group, respectively. The present study demonstrates that the effects of the stimulation with different iron species increased in the order of FeC6H5O7, Fe(OH)32x/x and EDTA-Fe.     

Effects of iron and humic acid on competition between Microcystis aeruginosa and Scenedesmus obliquus revealed by HPLC analysis of pigments

Iron is a vital micro nutrient for growth of bloom-forming Microcystis aeruginosa and competition with other algae,and its availability is affected by humic acid.The effect of iron and humic acid on growth and competition between M.aeruginosa and Scenedesmus obliquus was assessed.The results showed the growth of M.aeruginosa and S.obliquus in mono-cultures was inhibited by humic acid at low iron concentrations(0.01 mg/L);the maximum inhibition ratios were 67.84% and 38.31%,respectively.The inhibition of humic acid on the two species was significantly alleviated when iron concentrations were1.00 mg/L,with the maximum inhibition rate reduced to 5.82% for M.aeruginosa and to 23.06% for S.obliquus.S.obliquus was the dominant species in mixed cultures,and the mutual inhibition between M.aeruginosa and S.obliquus at low iron concentration was greater than that at high iron concentration.The inhibition of S.obliquus on M.aeruginosa was reduced at low iron concentrations;it increased at high iron concentrations,as concentrations of humic acid rose.     

Influences of hydrological regime on heavy metal and saltion concentrations in intertidal sediment from Chongming Dongtan,Changjiang River estuary,China

The tidal flat along the Changjiang(Yangtze) River estuary has long been reclaimed for the agricultural purposes, with the prevailing hydrological conditions during such pedogenic transformations being of great importance to their successful development. In this study, samples of surface sediment from Chongming Dongtan, situated at the mouth of the Changjiang River estuary, were collected and analyzed in order to understand how hydrological management can influence the concentrations of heavy metals and salt ions in pore water, and chemical fractionation of heavy metals during the reclamation process. We performed a series of experiments that simulated three dif ferent hydrological regimes: permanent flooding(R1), alternative five-day periods of wetting and drying(R2), continuous field capacity(R3). Our results exhibited good Pearson correlations coefficients between heavy metals and salt ions in the pore water for both R1 and R2. In particular, the concentrations of salt ions in the pore water decreased in all three regimes, but showed the biggest decline in R2. With this R2 experiment, the periodic concentration patterns in the pore water varied for Fe and Mn, but not for Cr, Cu, Pb and Zn. Neither the fractionation of Ni nor the residual fractions of any metals changed significantly in any regime. In R1, the reducible fractions of heavy metals(Cr, Cu, Zn and Pb) in the sediment decreased, while the acid extractable fractions increased. In R2, the acid extractable and the reducible fractions of Cr, Cu, Zn and Pb both decreased, as did the oxidizable fraction of Cu. These data suggest that an alternating hydrological regime can reduce both salinity and the availability of heavy metals in sediments.     

Study on changes of plasmalemma permeability and some primary inorganic ions of Antarctic ice microalgae （Chlamydomonas sp. ICE-L） in the low-temperature stress

The changes of plasmalemma permeability and some primary inorganic ions of Antarctic ice microalgae （ Chlamydomonas sp. ICE-L） in the low-temperature stress were examined. The plasmalemma of 1CE-L could maintain the stability at the freezing condition of -6 ℃. That signifies that it could maintain the proper function of plasmalemma and stability of the intracellular environment during sea ice formation. The function of inorganic ions on low-temperature adaptation of ICE-L was investigated by using the X-ray microanalysis method. Low temperature （0 - -6 ℃ ） induces Ca^2 ＋ concentration increment of cytoplasm, but after 24 h the content decrease quickly to normal value. As a matter of fact, Ca^2 ＋ plays an important role as the second messenger in the low temperature adaptation of ICE-L. In addition, low temperature also influences on the other primary inorganic ions transfer and the cell maintains activity by keeping ratio balance among different ions. Above all, it is necessary for Antarctic ice microalgae to survive and breed by maintaining the stability of K^ ＋ content and the balance of Na^ ＋/Cl^ -.     

Phosphorus sorption-desorption characteristics of ditch sediments from different land uses in a small headwater catchment in the central Sichuan Basin of China

Investigation of phosphorus (P) sorption-desorption characteristics of drainage ditch sediments is important for better understanding on sediment P transport behaviors in ditches. Surface ditch sediment samples were collected from headwater sub-catchment of forestland, sloping cropland, paddy field, and residential area in a representative catchment in the central Sichuan Basin. These sediment samples were used for determination of P sorption-desorption characteristics by a batch equilibrium technique. Results showed that the maximum P sorption capacities (Qm) in the sediments ranged from 159.7 to 263.7 mg/kg, while higher Qm were observed in the ditch sediments from the paddy fields. The Qm was significantly and positively correlated with oxalate-extractable Fe and Al oxides (r=0.97 and 0.98, p < 0.01), clay fraction (r = 0.78, p < 0.05) and organic matter (r = 0.95, p < 0.01). Sediment pH, clay and organic matter influenced the P sorption through amorphous Fe and Al oxides. CaCO3 content was negatively correlated with the Qm (r = -0.83, p < 0.05), implying that saturated CaCO3 (> 50 g/kg) would not increase P sorption capacity in the ditch sediments. The ditch sediments featured a linear desorption curve, suggesting that P release risk would be enhanced with the increase of the P adsorption. The P desorption rate was positively correlated with Olsen P (r = 0.94, p < 0.01), but negatively related to the fine particle-size fractions (r = -0.92, p < 0.01), the sum of the amorphous Fe and Al oxides (r = -0.67, p < 0.05) and the P sorption capacity (r = -0.59, p < 0.05). The ditch sediments from residential area had a higher P release risk than that from the other ditches of forestland, sloping cropland and paddy field. The P sorption index (PSI) derived from single-point measurement was significantly correlated with the P sorption capacity (r = 0.99, p < 0.01), and could be used for estimating Qm as 1.64 times PSI plus 24.0 (Qm = 1.64 PSI + 24.0) for similar sediments with highly calcareous soils and sediments. Ditch cleaning and sediment removal for the ditch in residential area were recommended in this area to reduce the P release risk.     

克拉通岩石圈地幔的形成与破坏:大洋板块俯冲的贡献

克拉通是地球上最古老的大陆地块.克拉通之所以能够长期稳定存在,主要是因为它具有巨厚、刚性的岩石圈地幔.古老克拉通岩石圈地幔具有高度难熔(富Mg、贫Fe)的特点,其密度较下伏软流圈小,能够"漂浮"在软流圈之上而长期存在.古老克拉通岩石圈地幔是在地球早期壳幔分异之后形成的,其形成可能与大洋板块的俯冲作用密切相关.典型的克拉...