Profile Distribution of Soil Properties on Sloping Cropland in Yingwugou Small Watershed of the Dan River Basin

Based on 3 m×3 m grid in sloping cornfield with soil auger in Yingwugou Small Watershed of the Dan River Basin,a total of 39sampling points were collected,and soil water content and nutrient content were measured in different soil depths.Meanwhile,the soil properties of different depth have been analyzed by traditional statistical and geo-statistics approaches.The results showed:the mean value of total nitrogen and soil organic carbon reduced as soil depth increased in general.But soil water content increased as the soil depth increased.The change of total phosphorus with soil depth was not obvious.The total nitrogen,soil water content,soil organic carbon and total phosphorus presented a moderate intensity variation and strong spatial dependence.In the four sampling depths,semi-variance model can simulate spatial structure of total nitrogen,soil water content and total phosphorus in 0 to 10 cm and 10 to 20 cm well.But the spatial structure of soil organic carbon was not good,which could not be simulated with semi-variance model.The analysis with Kriging interpolation showed that,the total nitrogen,soil water content and total phosphorus presented layered distribution in 0 to 10 cm and 10 to 20 cm;when the spatial distribution changed to 10 to 20cm from 0 to 10 cm,the average total nitrogen content reduced to from 0.598 g/kg 0.310 g/kg,while the average soil water content and total phosphorus increased from 12.988%to 15.439%and from 0.229 g/kg to 0.366 g/kg,respectively.

Evaluation of self-healing ability of Ce-V conversion coating on AZ31 magnesium alloy

This study investigated the influence of cerium nitrate in vanadate solutions on the properties of Ce–V conversion coatings on AZ31 magnesium alloys,and evaluated the self-healing behavior of the Ce–V conversion coating for AZ31 magnesium alloy.The results showed that the additions of cerium nitrate prevented pentavalent vanadium from reducing to tetravalent vanadium in the coatings during conversion reaction process.Adding appropriate cerium nitrate to vanadate solution led to a thicker coating with a more compact CeVO_(4) layer.The corrosion behavior of the Ce–V conversion coating was investigated by the electrochemical tests and the scratch immersion test in 3.5 wt.%NaCl solution.The self-healing ability of the coating was confirmed from all tests.The surface analysis revealed that the self-healing effect of the Ce–V conversion coating was only provided by the release and migration of vanadium compounds.

A Novel 3D Supramolecular Framework of Poly[(5-(oxidediphenylphosphino)isophthalate)zinc(Ⅱ)]: Syntheses and Structure

A novel metal-organic framework, namely [Zn（C20H13OsP）]n （1）, has been hydro- thermally synthesized through the reaction of 5-（oxidediphenylphosphino）isophthalic acid （H2L） with Zn（II） salt. The title compound crystallizes in monoclinic, space group P21/c with a = 11.0966（10）, b = 14.5651（14）, c = 14.7311（15） A, fl = 130.022（6）°, C2oH13OsPZn, Mr = 429.64, V= 1823.3（3） ./k3, Dc = 1.565 g/cm3, F（000） = 872, g = 1.463 mm＂1, S = 1.054 and Z = 4. The final R = 0.0270 and wR = 0.0739 for 2769 observed reflections with 1 〉 20（/）. In the title complex, the Zn2（CO2）2 binuclear clusters are linked by L2- ligands to result in a pillared layer structure in the bc plane, which is a （4,4）-net composed of helical chains with opposite chirality by sharing Zn2（CO2）2 units. Adjacent＇layers are further associated together through Zn-O bonds involving the metal center and the oxygen atom of P=O group to achieve a 3D architecture, in which one-dimensional qua＆angled channel displays the interweaving of two pairs of coaxial double-helical chains with opposite chirality. The luminescence property and thermogravimetric analysis of the title complex were investigated.

The response and anti-stress mechanisms of nitrifying sludge under long-term exposure to Cd Se quantum dots

The wide application of CdSe quantum dots(QDs)increases its stress risk to sewage treatment systems.This study evaluated the response of nitrification performance,floc characteristics and microbial community of nitrifying sludge under long-term exposure to CdSe QDs.Results showed CdSe QDs(≥1 mg/L)would decrease the activity of ammonia monooxygenase(AMO).Under the stress of 30 mg/L CdSe QDs,the activity of AMO was reduced by 66%,while the activities of hydroxylamine oxidase and nitrite oxidoreductase were enhanced by 19.1%and 26%,respectively.Thus,the final nitrification effects were not adversely affected,and the production rates of NO_(2)^(-)-N and NO_(3)^(-)-N were accelerated.Additionally,CdSe QDs improved biomass concentration in sludge and maintained the stability of sludge settleability.High throughput sequencing analysis showed that CdSe QDs evidently reduced the abundance and diversity of microbial community in nitrifying sludge.The abundances of amino acid metabolism and lipid metabolism were enriched.Moreover,CdSe QDs decreased the fluorescence intensity of tryptophan-like protein from 2,326 to 1,179 a.u.in loosely bound extracellular polymeric substances(EPSs)and from 3,792 to 3,117 a.u.in tightly bound EPSs.To relieve CdSe QD stress,the polysaccharide content increased from0.31 to 0.61 mg/g MLSS and intracellular antioxidant defense was activated.With CdSe QD level increasing to 30 mg/L,the total antioxygenic capacity and the activities of catalase were enhanced up to 411%and 143.2%,respectively.Thereby,CdSe QDs had little adverse effects on cell membrane integrity,microbial metabolism and the abundance of Nitrospirae.

Cytotoxicity and genotoxicity evaluation of urban surface waters using freshwater luminescent bacteria Vibrio-qinghaiensis sp.-Q67 and Vicia faba root tip

The freshwater luminescent bacteria Vibrio-qinghaiensis sp.-Q67 test and the Vicia faba root tip test associated with solid-phase extraction were applied for cytotoxicity and genotoxicity assessment of organic substances in three rivers, two lakes and effluent flows from two wastewater treatment plants （WWTPs） in Xi＇an, China. Although the most seriously polluted fiver with high chemical oxygen demand （COD） and total organic carbon （TOC） showed high cytotoxicity （expressed as TIIs0, the toxicity impact index） and genotoxicity （expressed as RMCN, the relative frequency of micronucleus）, no correlative relation was found between the ecotoxicity and organic content of the water samples. However, there was a linear correlative relation between TIIs0 and RMCN for most water samples except that from the Zaohe River, which receives discharge from WWTP and untreated industrial wastewaters. The ecotoxicity of the organic toxicants in the Chanhe River and Zaohe River indicated that cytotoxic and genotoxic effects were related to the pollutant source. The TII50 and RMCN were also found to correlate roughly to the dissolved oxygen concentration of the water. Sufficient dissolved oxygen in surface water is thus proved to be an indicator of a healthy water environmental condition.

Investigation and assessment of micropollutants and associated biological effects in wastewater treatment processes

Currently,the wastewater treatment plants(WWTPs)attempt to achieve the shifting from general pollution parameters control to reduction of organic micropollutants discharge.However,they have not been able to satisfy the increasing ecological safety needs.In this study,the removal of micropollutants was investigated,and the ecological safety was assessed for a local WWTP.Although the total concentration of 31 micropollutants detected was reduced by 83%using the traditional biological treatment processes,the results did not reflect chemicals that had poor removal efficiencies and low concentrations.Of the five categories of micropollutants,herbicides,insecticides,and bactericides were difficult to remove,pharmaceuticals and UV filters were effectively eliminated.The specific photosynthesis inhibition effect and non-specific bioluminescence inhibition effect from wastewater were detected and evaluated using hazardous concentration where 5%of aquatic organisms are affected.The photosynthesis inhibition effect from wastewater in the WWTP was negligible,even the untreated raw wastewater.However,the bioluminescence inhibition effect from wastewater which was defined as the priority biological effect,posed potential ecological risk.To decrease non-specific biological effects,especially of macromolecular dissolved organic matter,overall pollutant reduction strategy is necessary.Meanwhile,the ozonation process was used to further decrease the bioluminescence inhibition effects from the secondary effluent;≥0.34 g O 3/g DOC of ozone dose was recommended for micropollutants elimination control and ecological safety.

Application of a hybrid gravity-driven membrane filtration and dissolved ozone flotation(MDOF)process for wastewater reclamation and membrane fouling mitigation

This study proposed a novel membrane filtration and dissolved ozone flotation integrated(MDOF) process and tested it at pilot scale. Membrane filtration in the MDOF process was operated in gravity-driven mode, and required no backwashing, flushing, or chemical cleaning. Because ozone was added in the MDOF process, ozonation, coagulation, and membrane filtration could occur in a single reactor. Moreover, in situ ozonation occurred in the MDOF process, which differs from the conventional pre-ozonation membrane filtration process. Significant enhancement of turbidity removal was further achieved through the addition of membrane filtration. Membrane fouling was mitigated in the MDOF process compared to the MDAF process. In situ ozonation in the MDOF process decreased the fluorescence intensity and transformed the high MW dissolved organics into small MW compounds. For the fouling layer, the extracellular polymeric substance(EPS) contents and cake layer morphology were analyzed. The results indicated that the contents of EPS decreased. Furthermore, a thinner and more loosely structured cake layer formed in the MDOF process. Because coagulation and ozonation occurred simultaneously in a single reactor, the generation of hydroxyl radicals was enhanced through the catalytic effect of Al-based coagulants on ozone decomposition, which further alleviated membrane fouling in the MDOF process.

Distribution characteristics of available trace elements in soil from a reclaimed land in a mining area of north Shaanxi,China

Through field and laboratory tests we studied the temporal and spatial variation in the soil content of four available trace elements:copper(Cu),iron(Fe),manganese(Mn)and zinc(Zn),to analyze their distribution characteristics in reclaimed mining land under different reclamation conditions.The available trace elements content varied considerably with different land reclamation patterns.Extended reclamation time was helpful for the recovery of the available trace element content in the soil,and after more than eight years of soil reclamation,the content of available trace elements was closer to or greater than that in soil under natural conditions.Various treatment measures significantly influenced the content and distribution of available trace elements in the soil,and reasonable artificial treatments,including covering the soil and growing shrubs and herbaceous plants,increased the content of available trace elements.

Nitrogen-retaining property of compost in an aerobic thermophilic composting reactor for the sanitary disposal of human feces

Aerobic composting is a method for the sanitary disposal of human feces as is used in bio-toilet systems.As the products of composting can be utilized as a fertilizer,it would be beneficial if the composting conditions could be more precisely controlled for the retention of fecal nitrogen as long as possible in the compost.In this study,batch experiments were conducted using a closed aerobic thermophilic composting reactor with sawdust as the bulk matrix to simulate the condition of a bio-toilet for the sanitary disposal of human feces.Attention was paid to the characteristics of nitrogen transformation.Under the controlled conditions of temperature at 60°C,moisture content at 60%,and a continuous air supply,more than 70%fecal organic removal was obtained,while merely 17%fecal nitrogen loss was observed over a two-week composting period.The nitrogen loss was found to occur mainly in the first 24 h with the rapid depletion of inorganic nitrogen but with an almost unchanged organic nitrogen content.The fecal NH4-N which was the main component of the inorganic nitrogen(>90%)decreased rapidly in the first day,decreased at a slower rate over the following days,and finally disappeared entirely.The depletion of NH4-N was accompanied by the accumulation of NH3 gas in the ammonia absorber connected to the reactor.A mass balance between the exhausted NH3 gas and the fecal NH4-N content in the first 24 hours indicated that the conversion of ammonium into gaseous ammonia was the main reason for nitrogen loss.Thermophilic composting could be considered as a way to keep a high organic nitrogen content in the compost for better utilization as a fertilizer.

Dynamic membrane bioreactor performance enhancement by powdered activated carbon addition:Evaluation of sludge morphological,aggregative and microbial properties

The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane(DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes(protists and metazoans)and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC(BPAC), which promoted the enrichment of Acinetobacter(13.9%), Comamonas(2.9%), Flavobacterium(0.31%) and Pseudomonas(0.62%), all contributing to sludge flocs formation and several(such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance.

Quantitative study on influences of terraced field construction and check-dam siltation on soil erosion

To study the influences of terraced field construction and check-dam siltation on soil erosion of a watershed, we built a simplified watershed model for the Loess Plateau hilly-gully region including terraced fields, slope farmlands, steep-slope grasslands, and dam farmlands and defined three states of watershed （i.e., pioneer, intermediate, and climax stages, respec- tively）. Then, the watershed soil erosion moduli at various stages were studied by using a revised universal soil loss equation. Our results show that the pioneer and climax stages are the extreme states of watershed soil-and-water conservation and control; in the pioneer stage the soil erosion modulus was 299.56 t.ha-l.a 1 above the edge of gully, 136.64 t.ha-La-1 below the edge of gully, and 229.74 t.ha-~.a-~ on average; in the climax stage, the soil erosion modulus was 39.10 t.ha .a-1 above the edge of gully, 1.10 t.ha-La-1 below the edge of gully, and 22.81 t-ha-La-1 on average; in the intermediate stage, the soil erosion modulus above the edge of gully exhibited an exponential decline along with the increase in terraced field area percentage, while the soil erosion modulus below the edge of gully exhibited a linear decline along with the increase in siltation height.

On the effect of Fe(Ⅲ) on proliferation of Microcystis aeruginosa at high nitrate and low chlorophyll condition

The impact of Fe concentrations on the growth of Microcystis aeruginosa in aquatic systems under high nitrate and low chlorophyll conditions was studied. The responses of cell density,total and cell chlorophyll-a intracellular Fe content and organic elemental composition of M.aeruginosa to different concentration gradients of Fe（Ⅲ） in the solutions were analysed. The results showed that the proliferation speeds of M. aeruginosa were：（1） decelerated when the Fe（Ⅲ） concentration was lower than 50 μg/L in the solutions,（2） promoted and positively related to the increase of Fe（Ⅲ） concentration from 100 to 500 μg/L in the solutions over the experimental period, and（3） promoted in the early stage but decelerated in later stages by excess adsorption of Fe by cells when the Fe（Ⅲ） concentration was higher than 500 μg/L in the solutions. The maximum cell density, total and cell chlorophyll-a were all observed at 500 μg Fe（Ⅲ）/L concentration. The organic elemental composition of M. aeruginosa was also affected by the concentration of Fe（Ⅲ） in the solutions, and the molecular formula of M. aeruginosa should be expressed as C7–7.5H14O0.8–1.3N3.5–5according to the functions for different Fe（Ⅲ）concentrations. Cell carbon and oxygen content appeared to increase slightly, while cell nitrogen content appeared to decrease as Fe（Ⅲ） concentrations increased from 100 to 500 μg/L in the solutions. This was attributed to the competition of photosynthesis and nitrogen adsorption under varying cell Fe content.

Thermodynamic prediction and experimental investigation of short-term dynamic membrane formation in dynamic membrane bioreactors:Effects of sludge properties

In dynamic membrane bioreactors(DMBRs), a dynamic membrane(DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR using nylon mesh(25 μm) as support material to filtrate sludge suspensions of variable properties from three different sources to evaluate the effects on the short-term DM formation process(within 240 min). Furthermore, the extended Derjaguin–Landau–Verwey–Overbeek(XDLVO) theory was applied to analyze the sludge adhesion and cohesion behaviors on the mesh surface to predict quantitative parameters of the short-term DM formation process(including initial formation and maturation stage). The filtration results showed that the order of the initial DM formation time(permeate turbidity <1 NTU as an indicator) was as follows: sludge with poor settleability and dewaterability < normal sludge <sludge with poor flocculability. Moreover, normal sludge(regarding settleability, dewaterability,flocculability, and extracellular polymeric substance) showed a more acceptable DM formation performance(short DM formation time, low permeate turbidity, and high permeate flux) than sludge with poor settleability, dewaterability and flocculability. The influence of sludge properties on the initial DM formation time corroborates the prediction of sludge adhesion behaviors by XDLVO theory. Additionally, the XDLVO calculation results showed that acid–based interaction, energy barrier, and secondary energy minimum were important determinants of the sludge adhesion and cohesion behaviors. Therefore, short-term DM formation process may be enhanced to achieve stable long-term DMBR operation through positive modification of the sludge properties.