The disinfected bacteria will be a photoreactivation under the irradiation of the sunlight,and the light intensity plays an important role in the bacteria resurrection.The effect of light intensity on photoreactivatio...The disinfected bacteria will be a photoreactivation under the irradiation of the sunlight,and the light intensity plays an important role in the bacteria resurrection.The effect of light intensity on photoreactivation of Escherichia coli(E.coli) and Enterococcus faecalis(E.faecalis) in secondary effluents which were disinfected respectively by pure UV and UV-TiO_2 was investigated.The results show that the disinfection efficiency of UV-TiO_2 is much higher than that of the pure UV disinfection.The photoreactivation rate of E.coli is much higher in pure UV disinfection than in UV-TiO_2 photocatalytic disinfection.Under high light intensity in UV-TiO_2 disinfection,high resurrection rate can be induced.However,a higher resurrection rate can be introduced even under low light intensity in pure UV disinfection alone.Meanwhile,UV-TiO_2 disinfection has a strong inhibition effect on E.faecalis photoreactivation.When the light intensity is lower than 21 μW/cm^2,nearly no resurrection of E.faecalis occurs after 72 h resurrection irradiation,and a little resurrection rate is observed only under a strong photoreactivating light intensity.展开更多
China's Horqin Sandy Land,a formerly lush grassland,has experienced extensive desertification that caused considerable carbon(C) losses from the plant-soil system.Natural restoration through grazing exclusion is a...China's Horqin Sandy Land,a formerly lush grassland,has experienced extensive desertification that caused considerable carbon(C) losses from the plant-soil system.Natural restoration through grazing exclusion is a widely suggested option to sequester C and to restore degraded land.In a desertified grassland,we investigated the C accumulation in the total and light fractions of the soil organic matter from 2005 to 2013 during natural restoration.To a depth of 20 cm,the light fraction organic carbon(LFOC) storage increased by 221 g C/m2(84%) and the total soil organic carbon(SOC) storage increased by 435 g C/m2(55%).The light fraction dry matter content represented a small proportion of the total soil mass(ranging from 0.74% in 2005 to 1.39% in 2013),but the proportion of total SOC storage accounted for by LFOC was remarkable(ranging from 33% to 40%).The C sequestration averaged 28 g C/(m2·a) for LFOC and 54 g C/(m2·a) for total SOC.The total SOC was strongly and significantly positively linearly related to the light fraction dry matter content and the proportions of fine sand and silt+clay.The light fraction organic matter played a major role in total SOC sequestration.Our results suggest that grazing exclusion can restore desertified grassland and has a high potential for sequestering SOC in the semiarid Horqin Sandy Land.展开更多
Experimental and theoretical analysis were made on the natural humic acid removal and the membrane fouling of ultrafiltration (UF) with in-line coagulation. The results showed dissolved organic carbon (DOC) and UV254 ...Experimental and theoretical analysis were made on the natural humic acid removal and the membrane fouling of ultrafiltration (UF) with in-line coagulation. The results showed dissolved organic carbon (DOC) and UV254 removals by the UF with in-line coagulation at pH 7 were increased from 28% to 53% and 40% to 78% in comparison with direct UF treatment respectively. At the same time, the analysis of high performance liquid chromatography showed that UF with coagulation had significant improvement of removal of humic acid with molecular weights less than 6000 Da in particular. Compared to direct UF, the in-line coagulation UF also kept more constant permeate flux and very slight increase of transmembrane pressure during a filtration circle. Two typical membrane fouling models were used by inducing two coefficients Kc and Kp corresponding to cake filtration model and pore narrowing model respectively. It was found that membrane fouling by pore-narrowing effect was effectively alleviated and that by cake-filtration was much decreased by in-line coagulation. Under the condition of coagulation prior to ultrafiltration at pH 7, the cake layer formed on the membrane surface became thicker, but the membrane filtration resistance was lower than that at pH 5 with the extension of operation time.展开更多
This article focused on the influences of fulvic acid and humic acid on aluminum speciation in drinking water.Factors including the concentration of residual chlorine and pH value had been concerned.Aluminum species i...This article focused on the influences of fulvic acid and humic acid on aluminum speciation in drinking water.Factors including the concentration of residual chlorine and pH value had been concerned.Aluminum species investigated in the experiments included inorganic mononuclear,organic mononuclear,mononuclear,polymer,soluble,and suspended forms.It was found that the effects of fulvic acid and humic acid on aluminum speciation depended mainly on their molecular weight.Fulvic acid with molecular weight less than 5000 Dalton had little influence on aluminum speciation;while fulvic acid with molecular weight larger than 5000 Dalton and humic acid would increase the concentration of soluble aluminum significantly even at concentration below 0.5 mg/L(calculated as TOC).Aluminum species,in the present of fulvic acid with molecular weight larger than 5000 Dalton and humic acid,were more stable than that in the present of fluvic acid with molecular mass less than 5000 Dalton,and varied little with reaction time.Within pH range 6.5-7.5,soluble aluminum increased notably in water with organic matter.As the concentration of residual chlorine increased,the effects of fulvic acid and humic acid became weak.The reactions between humic acid,fulvic acid with large molecular weight,and aluminum were considered to be a multi-dentate coordination process.With the consideration of aluminum bioavailability,reducing the concentration of fulvic acid and humic acid and keeping the pH value among 6.5-7.5 were recommended during drinking water treatment.展开更多
Study on soil phosphorus(P) fraction is an important aspect in probing the mechanisms of soil P accumulation in farmland and mitigating its losing risk to the environment. We used a sequential extraction method to eva...Study on soil phosphorus(P) fraction is an important aspect in probing the mechanisms of soil P accumulation in farmland and mitigating its losing risk to the environment. We used a sequential extraction method to evaluate the impacts of long-term fertilization and straw incorporation on inorganic, organic, and residual P(Pi, Po, and Pre) fractions in the plow layer(0–20 cm) of acidic paddy soil in southern China. The experiment comprised of six treatments:(i) no fertilizer control(CK);(ii) straw incorporation and green manure(SG);(iii) nitrogen and P fertilizer(NP);(iv) NP+SG;(v) NP+K fertilizer(NPK); and(vi) NPK+SG. The results showed that, compared to the initial total soil P content(TSP, 600 mg kg–1 in 1990), long-term(20 years) combined continuous P fertilizer and SG significantly increased P accumulation(by 13–20%) while single fertilization(39.3 kg P ha–1 yr–1) could maintain soil P status at the most. The average soil P fractions comprised of extractable Pi, Po, and Pre by 51.7, 33.4, and 14.9% in total soil P, respectively. With comparison of no fertilizer addition(CK), long-term single fertilization significantly(P<0.05) increased the accumulation of Na HCO3–, Na OH–, and HCl– extractable Pi fractions accounting for two- to three-fold, while SG increased the accumulation of Na HCO3– and Na OH– extractable Piand Po accounting for 12–60%. Though the mobilization of Pre fractions was not significant(P>0.05), our data indicate that SG may partially substitute for fertilizer P input and minimizing soil P accumulation and subsequent environmental risk in the subtropical paddy soil.展开更多
The seasonal variation characteristics of the water quality of the Jinpen Reservoir and the impacts of rainfall runoff on the reservoir were investigated. Water quality monitoring results indicated that, during the st...The seasonal variation characteristics of the water quality of the Jinpen Reservoir and the impacts of rainfall runoff on the reservoir were investigated. Water quality monitoring results indicated that, during the stable stratification period, the maximum concentrations of total nitrogen, total phosphorus, ammonia nitrogen, total organic carbon, iron ion, and manganese ion in the water at the reservoir bottom on September6 reached 2.5 mg/L, 0.12 mg/L, 0.58 mg/L, 3.2 mg/L, 0.97 mg/L, and 0.32 mg/L, respectively. Only heavy storm runoff can affect the main reservoir and cause the water quality to seriously deteriorate. During heavy storms, the stratification of the reservoir was destroyed, and the reservoir water quality consequently deteriorated due to the high-turbidity particulate phosphorus and organic matter in runoff. The turbidity and concentrations of total phosphorus and total organic carbon in the main reservoir increased to 265 NTU, 0.224 mg/L, and 3.9 mg/L, respectively.Potential methods of dealing with the water problems in the Jinpen Reservoir are proposed. Both in stratification and in storm periods, the use of measures such as adjusting intake height, storing clean water, and releasing turbid flow can be helpful to safeguarding the quality of water supplied to the water treatment plants.展开更多
Medical stone-based porous ceramics as a carrier were prepared by ultra-fine grinding and low-temperature sintering method. Nano-TiO2 thin films were loaded on the carrier by chemical liquid deposition method using ti...Medical stone-based porous ceramics as a carrier were prepared by ultra-fine grinding and low-temperature sintering method. Nano-TiO2 thin films were loaded on the carrier by chemical liquid deposition method using titanium tetrachloride as a precursor. The micro-morphology and microstructure of the synthesized samples were characterized using X-ray diffraction, scanning electron microscopy with energy dispersive spectrometry, and mercury injection method. The photo-catalytic activity of the TiO2 thin films was investigated by degrading formaldehyde. The main crystalline phase in the TiO2 thin films calcined at 550 C is anatase with the average particle size about 10nm. The specific surface area of the carrier-coated nano-TiO2 increases from 3.68 to 5.32 m2/g. The formaldehyde removal rate of the TiO2/medical stone-based porous ceramics irradiated under an ultraviolet lamp for 120min reaches 85.6%.展开更多
Salix psammophila and Caragana korshinskii are two typical shrubs in the southern Mu Us Sandy Land of China which are threatened by increasing water deficits related to climate change and large-scale human activities(...Salix psammophila and Caragana korshinskii are two typical shrubs in the southern Mu Us Sandy Land of China which are threatened by increasing water deficits related to climate change and large-scale human activities(e.g. coal mining and oil exploitation). In this study, we assessed their vulnerability to xylem embolism and the related anatomical traits in two-year-old regenerated shoots of these two shrubs to understand how they cope with drought environment. We also evaluated the in situ hydraulic safety margins to hydraulic failure from measurements of annual predawn and midday leaf water potentials. The results showed that S. psammophila stems had a higher water transport capacity than C. korshinskii stems. The stem xylem water potentials at 12%, 50% and 88% loss of conductivity were –1.11, –1.63 and –2.15 MPa in S. psammophila, respectively, and –1.37, –2.64 and –3.91 MPa in C. korshinskii, respectively. This suggested that C. korshinskii was more resistant to cavitation than S. psammophila. Compared with S. psammophila, C. korshinskii had shorter maximum vessel length, lower vessel density, smaller conductive area and higher wood density, which may contribute to its more resistant xylem. The in situ hydraulic safety margins indicated that even during the driest periods, both shrubs lived well above the most critical embolism thresholds, and the hydraulic safety margin was wider in C. korshinskii than in S. psammophila, suggesting that the regenerated shoots of both shrubs could function normally and C. korshinskii had greater hydraulic protection. These results provide the basis for an in-depth understanding of the survival, growth and functional behavior of these two shrubs under harsh and dry desert environments.展开更多
An 8-week feeding experiment was performed to evaluate the effect of dietary genistein on growth performance,body composition,and digestive enzymes activity of juvenile Nile tilapia(Oreochromis niloticus).Four isonitr...An 8-week feeding experiment was performed to evaluate the effect of dietary genistein on growth performance,body composition,and digestive enzymes activity of juvenile Nile tilapia(Oreochromis niloticus).Four isonitrogenous and isoenergetic diets were formulated containing four graded supplements of genistein:0,30,300,and 3 000 μg/g.Each diet was randomly assigned in triplicate to tanks stocked with 15 juvenile tilapia(10.47±1.24 g).The results show that 30 and 300 μg/gdietary genistein had no significant effect on growth performance of Nile tilapia,but the higher level of genistein(3 000 μg/g)significantly depressed the final body weight and specific growth rate.There was no significant difference in survival rate,feed intake,feed efficiency ratio or whole body composition among all dietary treatments.An assay of digestive enzymes showed that the diet containing 3 000 μg/ggenistein decreased stomach and hepatopancreas protease activity,and amylase activity in the liver and intestine,while a dietary level of300 μg/g genistein depressed stomach protease and intestine amylase activities.However,no significant difference in stomach amylase activity was found among dietary treatments.Overall,the results of the present study indicate that a high level of dietary genistein(3 000 μg/g,or above) would significantly reduce the growth of Nile tilapia,partly because of its inhibitory effect on the activity of major digestive enzymes.Accordingly,the detrimental effects of genistein,as found in soybean products,should not be ignored when applied as an alternative ingredient source in aquaculture.展开更多
In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ i...In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ in OTC-1 and 3-5℃ in OTC-2 in the alpine meadow ecosystem on the Qinghai- Tibetan Plateau.Results show that the annual air temperatures under OTC-1 and OTC-2 were 1.21℃ and 3.62℃ higher than the Control,respectively.The entirely-frozen period of shallow soil in the active layer was shortened and the fully thawed period was prolonged with temperature increase.The maximum penetration depth and duration of the negative isotherm during the entirely-frozen period decreased, and soil freezing was retarded in the local scope of the soil profile when temperature increased.Meanwhile, the positive isotherm during the fully-thawed period increased,and the soil thawing was accelerated.Soil moisture under different manipulations decreased with the temperature increase at the same depth. During the early freezing period and the early fully- thawed period,the maximum soil moisture under the Control manipulation was at 0.2 m deep,whereas under OTC-1 and OTC-2 manipulations,the maximum soil moisture were at 0.4-0.5 m deep. These results indicate that elevated temperatures led to a decrease of the moisture in the surface soil.The coupled relationship between soil temperature and moisture was significantly affected by the temperature increase.During the freezing and thawing processes, the soil temperature and moisture under different manipulations fit the regression model given by the equationθV=a/{1+exp[b(TS+c)]}+d.展开更多
The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experie...The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experienced severe desertification in recent decades due to its fragile ecology together with inappropriate human activities. Currently, the landscape of the Horqin Sandy Land is dominated by irrigated croplands and sand dunes with different degrees of vegetation cover, as the region has become the most important part of the semiarid agro-pastoral ecotone of northern China. In this study, we compared soil physical and chemical properties under different land-use and cover types(irrigated cropland, rainfed cropland, sandy grassland, fixed dunes, and mobile dunes). We found that soil particle size distribution; organic C, total N, and total mineral element, microelement, and available microelement and nutrient contents; p H; CEC; and bulk density differed significantly among the land-use and cover types. In general, soil quality was highest in the cropland, intermediate in the sandy grassland, and lowest in the dunes. The most important soil quality attribute, soil organic carbon(SOC) storage, decreased in the following order: irrigated cropland(5,699 g/m^2) > sandy grassland(3,390 g/m^2) > rainfed cropland(2,411 g/m^2) > fixed dunes(821 g/m^2) > mobile dunes(463 g/m^2). SOC was significantly positively correlated with a large proportion of the other soil physico-chemical parameters. Our results suggest that the key issue in restoration of the degraded soils will be to increase SOC storage, which would also create a high potential for sequestering soil C in desertified areas of the Horqin Sandy Land.展开更多
The effectiveness of enhancing treatment of water with low turbidity through combined effects of permanganate oxidation, PAM aiding coagulation and sludge recycling was investigated through continuous bench scale stud...The effectiveness of enhancing treatment of water with low turbidity through combined effects of permanganate oxidation, PAM aiding coagulation and sludge recycling was investigated through continuous bench scale studies. In comparing with ferric chloride coagulation, only recycling sedimentation sludge was ineffective in enhancing treatment of water with low turbidity. PAM with recycled sludge showed positive effects, and the additional permanganate dosing exhibited the best potential of favoring coagulation, which leaded to much lower effluent turbidity and CODMn. Additionally, it was observed that the optimal permanganate dosage was 0.4 mg/L and the higher permanganate dosage exhibited inhibiting effects for pollutants removal. SEM analysis indicated that the flocs were loosely formed and the particle diameter was critically low for ferric chloride coagulation process. Comparatively, the addition of PAM and permanganate with recycled sludge facilitated the aggregation of tinny particles onto compact PAM polymer chains, therefore contributing to the formation of compact flocs with high particle diameter. The combined employment of recycled sludge, PAM and permanganate showed the best potential of favoring coagulation, mainly through synergistic effects between seeding, polymer bridging and increasing effective collision in mechanism. Additionally, the variation of Fe and Mn concentration after recycling and sedimentating units was studied for the processes, and the main species was also investigated for elements Fe and Mn. Sludge recycling and permanganate addition did not increase Fe and Mn concentration in the sedimented water.展开更多
The application of vortex generators in tube-finned heat exchangers is very universal.The vortex generators can generate secondary flow,and as we all know secondary flow can obviously strengthen heat transfer.To use v...The application of vortex generators in tube-finned heat exchangers is very universal.The vortex generators can generate secondary flow,and as we all know secondary flow can obviously strengthen heat transfer.To use vortex generators much more efficiently in the circle tube-finned heat exchangers,the intensity correlation study between secondary flow and heat transfer is needed.22 different structures of circle tube-finned heat exchangers were numerically studied,including the plain fin cases and the cases with vortex generators.In addition,the influence of fin spacing,transverse and longitudinal tube pitch,heights and attack angle of vortex generators,positions of vortex generators and shape of vortex generators on heat transfer and fluid flow are studied,too.The non-dimensional parameter Se is applied to quantify the secondary flow intensity.The results show that Se can describe the secondary flow intensity very well.There is very close corresponding relationship between overall averaged Nu and volumetrically averaged Se for all the researched cases and the relational expression is obtained.However,there is no one-to-one correlation not only between Re and f but also between volumetrically averaged Se and f for all the studied cases.展开更多
Understanding the soil taxonomy and distribution characteristics of the permafrost region in the Qinghai-Tibet Plateau(QTP) is very important. On the basis of extensive field surveys and experimental analysis, this st...Understanding the soil taxonomy and distribution characteristics of the permafrost region in the Qinghai-Tibet Plateau(QTP) is very important. On the basis of extensive field surveys and experimental analysis, this study carries out soil taxonomic classification of the permafrost region in the QTP. According to Chinese Soil Taxonomy, the soil of the permafrost region in the QTP can be divided into 6 Orders(Histosols, Aridosols, Gleyosols, Isohumosols, Cambosols, Primosols), 11 Suborders, 19 Groups and 24 Subgroups. Cambosols are the dominant soil type in the permafrost region, followed by Aridosols. From the east to the west of the permafrost region in the QTP, the soil type gradually changes from Cambosols to Aridosols, showing a meridional zonality. The eastern region is dominated by Cambosols, with no obvious latitudinal zonality. From the south to the northwest of the western region, the dominance of Aridosols and Cambosols gradually transited to Aridosols, presenting a latitudinal zonality. The soil in the western region shows a poor vertical zonality, while the distribution of suborders of Cambosols in the eastern region shows a more obvious vertical zonality. The result indicates that precipitation and vegetation are the main factors that influence the zonal distribution of soil. The permafrost in the east has some effect on the vertical soil zonality, but the effect is weakened in the west.展开更多
We investigated the effect of supply air rate and temperature on formaldehyde emission characteristics in an environment chamber.A three-dimensional computational fluid dynamics(CFD) chamber model for simulating forma...We investigated the effect of supply air rate and temperature on formaldehyde emission characteristics in an environment chamber.A three-dimensional computational fluid dynamics(CFD) chamber model for simulating formaldehyde emission in twelve different cases was developed for obtaining formaldehyde concentration by the area-weighted average method.Laboratory experiments were conducted in an environment chamber to validate the simulation results of twelve different cases and the formaldehyde concentration was measured by continuous sampling.The results show that there was good agreement between the model prediction and the experimental values within 4.3 difference for each case.The CFD simulation results varied in the range from 0.21 mg/m3 to 0.94 mg/m3,and the measuring results in the range from 0.17 mg/m3 to 0.87 mg/m3.The variation trend of formaldehyde concentration with supply air rate and temperature variation for CFD simulation and experiment measuring was consistent.With the existence of steady formaldehyde emission sources,formaldehyde concentration generally increased with the increase of temperature,and it decreased with the increase of air supply rate.We also provided some reasonable suggestions to reduce formaldehyde concentration and to improve indoor air quality for newly decorated rooms.展开更多
Bio-ceramsite technology is one of the most effective technologies in the pretreatment of drinking water. In this work, bio-ceramsite was fabricated by Citrobacter freundii(C. freundii) immobilization on the ceramsite...Bio-ceramsite technology is one of the most effective technologies in the pretreatment of drinking water. In this work, bio-ceramsite was fabricated by Citrobacter freundii(C. freundii) immobilization on the ceramsite. The fi ndings of the current study suggest that the bio-ceramites showed biosorption abilities for Cd(II) and Pb(II) and the removal efficiency for Pb(II) is lower than Cd(II). The adsorption mechanism can be attributed to electrostatic attraction and covalent bond. The morphology of the cells changed after the adsorption of Cd(II) and Pb(II) due to the dissociation of the assembly of peptidoglycan and lipopolysaccharide. The fluorescence polarization has shown a significant decrease in membrane fluidity and an increase of permeability of cell membrane. The spectral profi le of C. freundii suggests the alteration of carbonyl, amide and phosphonic groups on the cell membrane.展开更多
To quantize the difficulty level of dust production on the surface of different types of farmland,the Marticorena threshold frictional velocity pattern was used in this study to simulate the dust threshold frictional ...To quantize the difficulty level of dust production on the surface of different types of farmland,the Marticorena threshold frictional velocity pattern was used in this study to simulate the dust threshold frictional velocity.The results showed that the dust threshold frictional velocity of desertification farmland was 7.39cm/s,while it was 29.05 cm/s after the wheat harvested and the farmland ploughed; the turning green period was 46.85 cm/s; shooting period was 98.93 cm/s,the uncovered and the establishment period of fruit tree farmland was 26.0 and 139.15 cm/s.It was concluded that,bare desertification farmland could be changed into source of dust release easier.展开更多
Improving the soil and biomass with coal is estimated at the international level as a way to enhance soil productiveness, fertility and also to mitigate climate change. Biochar employed to improve land scope and impou...Improving the soil and biomass with coal is estimated at the international level as a way to enhance soil productiveness, fertility and also to mitigate climate change. Biochar employed to improve land scope and impound carbon, is attracting a great deal of attention. Its characteristics of chemical, physical and biological properties, containing big surface area, CEC (Cation Exchange Capacity), high water-holding capacity, size of pore, volume, distribution, and element composition, affect its recognized influences, particularly on microbial communities. These are discovered in the agriculture lands, lands remediation and composting. However, incomplete information existed about biochar for several farmers or peasants in agriculture scope. Therefore, farmers or peasants and gardeners are facing new opportunities and defiance each day, from feeding global extending and expanding population, whilst meeting severe new emissions requirements, to create more food on fewer land area while reducing their environmental emissions. Widespread application and utilization of biochar in agricultural scope, forestry production, energy, environmental protection and additional areas, has interested awareness by scientists and investigators inside and/or outside the country. The objective of this paper is to provide a guide for the farmers or peasants and gardeners with an essential information about biochar and what the ability of biochar can be achieved in the soil, and which can provide the scientific reference for the biochar application, and to get high yield and good quality of crops in all of different soils.展开更多
基金Projects(51174090,51168026)supported by the National Natural Science Foundation of China
文摘The disinfected bacteria will be a photoreactivation under the irradiation of the sunlight,and the light intensity plays an important role in the bacteria resurrection.The effect of light intensity on photoreactivation of Escherichia coli(E.coli) and Enterococcus faecalis(E.faecalis) in secondary effluents which were disinfected respectively by pure UV and UV-TiO_2 was investigated.The results show that the disinfection efficiency of UV-TiO_2 is much higher than that of the pure UV disinfection.The photoreactivation rate of E.coli is much higher in pure UV disinfection than in UV-TiO_2 photocatalytic disinfection.Under high light intensity in UV-TiO_2 disinfection,high resurrection rate can be induced.However,a higher resurrection rate can be introduced even under low light intensity in pure UV disinfection alone.Meanwhile,UV-TiO_2 disinfection has a strong inhibition effect on E.faecalis photoreactivation.When the light intensity is lower than 21 μW/cm^2,nearly no resurrection of E.faecalis occurs after 72 h resurrection irradiation,and a little resurrection rate is observed only under a strong photoreactivating light intensity.
基金supported by the National Natural Science Foundation of China (41271007,31170413)the National Science and Technology Support Program of China (2011BAC07B02)
文摘China's Horqin Sandy Land,a formerly lush grassland,has experienced extensive desertification that caused considerable carbon(C) losses from the plant-soil system.Natural restoration through grazing exclusion is a widely suggested option to sequester C and to restore degraded land.In a desertified grassland,we investigated the C accumulation in the total and light fractions of the soil organic matter from 2005 to 2013 during natural restoration.To a depth of 20 cm,the light fraction organic carbon(LFOC) storage increased by 221 g C/m2(84%) and the total soil organic carbon(SOC) storage increased by 435 g C/m2(55%).The light fraction dry matter content represented a small proportion of the total soil mass(ranging from 0.74% in 2005 to 1.39% in 2013),but the proportion of total SOC storage accounted for by LFOC was remarkable(ranging from 33% to 40%).The C sequestration averaged 28 g C/(m2·a) for LFOC and 54 g C/(m2·a) for total SOC.The total SOC was strongly and significantly positively linearly related to the light fraction dry matter content and the proportions of fine sand and silt+clay.The light fraction organic matter played a major role in total SOC sequestration.Our results suggest that grazing exclusion can restore desertified grassland and has a high potential for sequestering SOC in the semiarid Horqin Sandy Land.
基金The National Natural Science Foundation of China (No. 50138020)
文摘Experimental and theoretical analysis were made on the natural humic acid removal and the membrane fouling of ultrafiltration (UF) with in-line coagulation. The results showed dissolved organic carbon (DOC) and UV254 removals by the UF with in-line coagulation at pH 7 were increased from 28% to 53% and 40% to 78% in comparison with direct UF treatment respectively. At the same time, the analysis of high performance liquid chromatography showed that UF with coagulation had significant improvement of removal of humic acid with molecular weights less than 6000 Da in particular. Compared to direct UF, the in-line coagulation UF also kept more constant permeate flux and very slight increase of transmembrane pressure during a filtration circle. Two typical membrane fouling models were used by inducing two coefficients Kc and Kp corresponding to cake filtration model and pore narrowing model respectively. It was found that membrane fouling by pore-narrowing effect was effectively alleviated and that by cake-filtration was much decreased by in-line coagulation. Under the condition of coagulation prior to ultrafiltration at pH 7, the cake layer formed on the membrane surface became thicker, but the membrane filtration resistance was lower than that at pH 5 with the extension of operation time.
基金the National Natural Science Foundation of China (No.20507009)the Program for New Century Excellent Talents in University (NCET) of the Ministry of Education of China,the Natural Science Foundation of Jiangsu Province for Outstanding Young Scientist (No.BK2006518)and the International Foundation for Science (No.C/3958-1).
基金supported by the National Natural Science Foundation of China (No.50838005)the Changjiang Scholars and Innovative Research Team in University(No.IRT0853)the American Aluminum Foundation
文摘This article focused on the influences of fulvic acid and humic acid on aluminum speciation in drinking water.Factors including the concentration of residual chlorine and pH value had been concerned.Aluminum species investigated in the experiments included inorganic mononuclear,organic mononuclear,mononuclear,polymer,soluble,and suspended forms.It was found that the effects of fulvic acid and humic acid on aluminum speciation depended mainly on their molecular weight.Fulvic acid with molecular weight less than 5000 Dalton had little influence on aluminum speciation;while fulvic acid with molecular weight larger than 5000 Dalton and humic acid would increase the concentration of soluble aluminum significantly even at concentration below 0.5 mg/L(calculated as TOC).Aluminum species,in the present of fulvic acid with molecular weight larger than 5000 Dalton and humic acid,were more stable than that in the present of fluvic acid with molecular mass less than 5000 Dalton,and varied little with reaction time.Within pH range 6.5-7.5,soluble aluminum increased notably in water with organic matter.As the concentration of residual chlorine increased,the effects of fulvic acid and humic acid became weak.The reactions between humic acid,fulvic acid with large molecular weight,and aluminum were considered to be a multi-dentate coordination process.With the consideration of aluminum bioavailability,reducing the concentration of fulvic acid and humic acid and keeping the pH value among 6.5-7.5 were recommended during drinking water treatment.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX2-YW-T07)the National Natural Science Foundation of China (41171396)
文摘Study on soil phosphorus(P) fraction is an important aspect in probing the mechanisms of soil P accumulation in farmland and mitigating its losing risk to the environment. We used a sequential extraction method to evaluate the impacts of long-term fertilization and straw incorporation on inorganic, organic, and residual P(Pi, Po, and Pre) fractions in the plow layer(0–20 cm) of acidic paddy soil in southern China. The experiment comprised of six treatments:(i) no fertilizer control(CK);(ii) straw incorporation and green manure(SG);(iii) nitrogen and P fertilizer(NP);(iv) NP+SG;(v) NP+K fertilizer(NPK); and(vi) NPK+SG. The results showed that, compared to the initial total soil P content(TSP, 600 mg kg–1 in 1990), long-term(20 years) combined continuous P fertilizer and SG significantly increased P accumulation(by 13–20%) while single fertilization(39.3 kg P ha–1 yr–1) could maintain soil P status at the most. The average soil P fractions comprised of extractable Pi, Po, and Pre by 51.7, 33.4, and 14.9% in total soil P, respectively. With comparison of no fertilizer addition(CK), long-term single fertilization significantly(P<0.05) increased the accumulation of Na HCO3–, Na OH–, and HCl– extractable Pi fractions accounting for two- to three-fold, while SG increased the accumulation of Na HCO3– and Na OH– extractable Piand Po accounting for 12–60%. Though the mobilization of Pre fractions was not significant(P>0.05), our data indicate that SG may partially substitute for fertilizer P input and minimizing soil P accumulation and subsequent environmental risk in the subtropical paddy soil.
基金supported by the National Science and Technology Pillar Program(Grant No.2012BAC04B02)the National Natural Science Foundation of China(Grant No.51478378)
文摘The seasonal variation characteristics of the water quality of the Jinpen Reservoir and the impacts of rainfall runoff on the reservoir were investigated. Water quality monitoring results indicated that, during the stable stratification period, the maximum concentrations of total nitrogen, total phosphorus, ammonia nitrogen, total organic carbon, iron ion, and manganese ion in the water at the reservoir bottom on September6 reached 2.5 mg/L, 0.12 mg/L, 0.58 mg/L, 3.2 mg/L, 0.97 mg/L, and 0.32 mg/L, respectively. Only heavy storm runoff can affect the main reservoir and cause the water quality to seriously deteriorate. During heavy storms, the stratification of the reservoir was destroyed, and the reservoir water quality consequently deteriorated due to the high-turbidity particulate phosphorus and organic matter in runoff. The turbidity and concentrations of total phosphorus and total organic carbon in the main reservoir increased to 265 NTU, 0.224 mg/L, and 3.9 mg/L, respectively.Potential methods of dealing with the water problems in the Jinpen Reservoir are proposed. Both in stratification and in storm periods, the use of measures such as adjusting intake height, storing clean water, and releasing turbid flow can be helpful to safeguarding the quality of water supplied to the water treatment plants.
基金supported by the Natural Science Research Projects of the Education Department of Henan Province,China(No.2011B610005)
文摘Medical stone-based porous ceramics as a carrier were prepared by ultra-fine grinding and low-temperature sintering method. Nano-TiO2 thin films were loaded on the carrier by chemical liquid deposition method using titanium tetrachloride as a precursor. The micro-morphology and microstructure of the synthesized samples were characterized using X-ray diffraction, scanning electron microscopy with energy dispersive spectrometry, and mercury injection method. The photo-catalytic activity of the TiO2 thin films was investigated by degrading formaldehyde. The main crystalline phase in the TiO2 thin films calcined at 550 C is anatase with the average particle size about 10nm. The specific surface area of the carrier-coated nano-TiO2 increases from 3.68 to 5.32 m2/g. The formaldehyde removal rate of the TiO2/medical stone-based porous ceramics irradiated under an ultraviolet lamp for 120min reaches 85.6%.
基金supported by the National Natural Science Foundation of China(41371507)
文摘Salix psammophila and Caragana korshinskii are two typical shrubs in the southern Mu Us Sandy Land of China which are threatened by increasing water deficits related to climate change and large-scale human activities(e.g. coal mining and oil exploitation). In this study, we assessed their vulnerability to xylem embolism and the related anatomical traits in two-year-old regenerated shoots of these two shrubs to understand how they cope with drought environment. We also evaluated the in situ hydraulic safety margins to hydraulic failure from measurements of annual predawn and midday leaf water potentials. The results showed that S. psammophila stems had a higher water transport capacity than C. korshinskii stems. The stem xylem water potentials at 12%, 50% and 88% loss of conductivity were –1.11, –1.63 and –2.15 MPa in S. psammophila, respectively, and –1.37, –2.64 and –3.91 MPa in C. korshinskii, respectively. This suggested that C. korshinskii was more resistant to cavitation than S. psammophila. Compared with S. psammophila, C. korshinskii had shorter maximum vessel length, lower vessel density, smaller conductive area and higher wood density, which may contribute to its more resistant xylem. The in situ hydraulic safety margins indicated that even during the driest periods, both shrubs lived well above the most critical embolism thresholds, and the hydraulic safety margin was wider in C. korshinskii than in S. psammophila, suggesting that the regenerated shoots of both shrubs could function normally and C. korshinskii had greater hydraulic protection. These results provide the basis for an in-depth understanding of the survival, growth and functional behavior of these two shrubs under harsh and dry desert environments.
基金Supported by the National Natural Science Foundation of China(No.31170322)
文摘An 8-week feeding experiment was performed to evaluate the effect of dietary genistein on growth performance,body composition,and digestive enzymes activity of juvenile Nile tilapia(Oreochromis niloticus).Four isonitrogenous and isoenergetic diets were formulated containing four graded supplements of genistein:0,30,300,and 3 000 μg/g.Each diet was randomly assigned in triplicate to tanks stocked with 15 juvenile tilapia(10.47±1.24 g).The results show that 30 and 300 μg/gdietary genistein had no significant effect on growth performance of Nile tilapia,but the higher level of genistein(3 000 μg/g)significantly depressed the final body weight and specific growth rate.There was no significant difference in survival rate,feed intake,feed efficiency ratio or whole body composition among all dietary treatments.An assay of digestive enzymes showed that the diet containing 3 000 μg/ggenistein decreased stomach and hepatopancreas protease activity,and amylase activity in the liver and intestine,while a dietary level of300 μg/g genistein depressed stomach protease and intestine amylase activities.However,no significant difference in stomach amylase activity was found among dietary treatments.Overall,the results of the present study indicate that a high level of dietary genistein(3 000 μg/g,or above) would significantly reduce the growth of Nile tilapia,partly because of its inhibitory effect on the activity of major digestive enzymes.Accordingly,the detrimental effects of genistein,as found in soybean products,should not be ignored when applied as an alternative ingredient source in aquaculture.
基金founded by The National Science Foundation of China(No.40730634 andNo.40925002)
文摘In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ in OTC-1 and 3-5℃ in OTC-2 in the alpine meadow ecosystem on the Qinghai- Tibetan Plateau.Results show that the annual air temperatures under OTC-1 and OTC-2 were 1.21℃ and 3.62℃ higher than the Control,respectively.The entirely-frozen period of shallow soil in the active layer was shortened and the fully thawed period was prolonged with temperature increase.The maximum penetration depth and duration of the negative isotherm during the entirely-frozen period decreased, and soil freezing was retarded in the local scope of the soil profile when temperature increased.Meanwhile, the positive isotherm during the fully-thawed period increased,and the soil thawing was accelerated.Soil moisture under different manipulations decreased with the temperature increase at the same depth. During the early freezing period and the early fully- thawed period,the maximum soil moisture under the Control manipulation was at 0.2 m deep,whereas under OTC-1 and OTC-2 manipulations,the maximum soil moisture were at 0.4-0.5 m deep. These results indicate that elevated temperatures led to a decrease of the moisture in the surface soil.The coupled relationship between soil temperature and moisture was significantly affected by the temperature increase.During the freezing and thawing processes, the soil temperature and moisture under different manipulations fit the regression model given by the equationθV=a/{1+exp[b(TS+c)]}+d.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41271007, 31260089, and 31560161)the One Hundred Person Project of the Chinese Academy of Sciences (Y551821002)
文摘The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experienced severe desertification in recent decades due to its fragile ecology together with inappropriate human activities. Currently, the landscape of the Horqin Sandy Land is dominated by irrigated croplands and sand dunes with different degrees of vegetation cover, as the region has become the most important part of the semiarid agro-pastoral ecotone of northern China. In this study, we compared soil physical and chemical properties under different land-use and cover types(irrigated cropland, rainfed cropland, sandy grassland, fixed dunes, and mobile dunes). We found that soil particle size distribution; organic C, total N, and total mineral element, microelement, and available microelement and nutrient contents; p H; CEC; and bulk density differed significantly among the land-use and cover types. In general, soil quality was highest in the cropland, intermediate in the sandy grassland, and lowest in the dunes. The most important soil quality attribute, soil organic carbon(SOC) storage, decreased in the following order: irrigated cropland(5,699 g/m^2) > sandy grassland(3,390 g/m^2) > rainfed cropland(2,411 g/m^2) > fixed dunes(821 g/m^2) > mobile dunes(463 g/m^2). SOC was significantly positively correlated with a large proportion of the other soil physico-chemical parameters. Our results suggest that the key issue in restoration of the degraded soils will be to increase SOC storage, which would also create a high potential for sequestering soil C in desertified areas of the Horqin Sandy Land.
基金Sponsored by the National High Technology Research and Development Program of China(Grant No.2004AA601020)
文摘The effectiveness of enhancing treatment of water with low turbidity through combined effects of permanganate oxidation, PAM aiding coagulation and sludge recycling was investigated through continuous bench scale studies. In comparing with ferric chloride coagulation, only recycling sedimentation sludge was ineffective in enhancing treatment of water with low turbidity. PAM with recycled sludge showed positive effects, and the additional permanganate dosing exhibited the best potential of favoring coagulation, which leaded to much lower effluent turbidity and CODMn. Additionally, it was observed that the optimal permanganate dosage was 0.4 mg/L and the higher permanganate dosage exhibited inhibiting effects for pollutants removal. SEM analysis indicated that the flocs were loosely formed and the particle diameter was critically low for ferric chloride coagulation process. Comparatively, the addition of PAM and permanganate with recycled sludge facilitated the aggregation of tinny particles onto compact PAM polymer chains, therefore contributing to the formation of compact flocs with high particle diameter. The combined employment of recycled sludge, PAM and permanganate showed the best potential of favoring coagulation, mainly through synergistic effects between seeding, polymer bridging and increasing effective collision in mechanism. Additionally, the variation of Fe and Mn concentration after recycling and sedimentating units was studied for the processes, and the main species was also investigated for elements Fe and Mn. Sludge recycling and permanganate addition did not increase Fe and Mn concentration in the sedimented water.
基金supported by the National Natural Science Foundation of China(Nos.51868035,51866006,51468028)Foundation of a Hundred Youth Talents Training Program of Lanzhou Jiaotong Universitythe Science and Technology Plan of Gansu Province(No.18JR3RA121).
文摘The application of vortex generators in tube-finned heat exchangers is very universal.The vortex generators can generate secondary flow,and as we all know secondary flow can obviously strengthen heat transfer.To use vortex generators much more efficiently in the circle tube-finned heat exchangers,the intensity correlation study between secondary flow and heat transfer is needed.22 different structures of circle tube-finned heat exchangers were numerically studied,including the plain fin cases and the cases with vortex generators.In addition,the influence of fin spacing,transverse and longitudinal tube pitch,heights and attack angle of vortex generators,positions of vortex generators and shape of vortex generators on heat transfer and fluid flow are studied,too.The non-dimensional parameter Se is applied to quantify the secondary flow intensity.The results show that Se can describe the secondary flow intensity very well.There is very close corresponding relationship between overall averaged Nu and volumetrically averaged Se for all the researched cases and the relational expression is obtained.However,there is no one-to-one correlation not only between Re and f but also between volumetrically averaged Se and f for all the studied cases.
基金financially supported by the National Major Scientific Project of China "Cryospheric Change and Impacts Research" program "Research of permafrost hydrothermal process and its response to climate change" (Grant No. 2013CBA01803)Chinese Academy of Sciences (KJZD-EW-G03-02)
文摘Understanding the soil taxonomy and distribution characteristics of the permafrost region in the Qinghai-Tibet Plateau(QTP) is very important. On the basis of extensive field surveys and experimental analysis, this study carries out soil taxonomic classification of the permafrost region in the QTP. According to Chinese Soil Taxonomy, the soil of the permafrost region in the QTP can be divided into 6 Orders(Histosols, Aridosols, Gleyosols, Isohumosols, Cambosols, Primosols), 11 Suborders, 19 Groups and 24 Subgroups. Cambosols are the dominant soil type in the permafrost region, followed by Aridosols. From the east to the west of the permafrost region in the QTP, the soil type gradually changes from Cambosols to Aridosols, showing a meridional zonality. The eastern region is dominated by Cambosols, with no obvious latitudinal zonality. From the south to the northwest of the western region, the dominance of Aridosols and Cambosols gradually transited to Aridosols, presenting a latitudinal zonality. The soil in the western region shows a poor vertical zonality, while the distribution of suborders of Cambosols in the eastern region shows a more obvious vertical zonality. The result indicates that precipitation and vegetation are the main factors that influence the zonal distribution of soil. The permafrost in the east has some effect on the vertical soil zonality, but the effect is weakened in the west.
基金Funded by National Science Foundation(No.50778415 and No.50878177)
文摘We investigated the effect of supply air rate and temperature on formaldehyde emission characteristics in an environment chamber.A three-dimensional computational fluid dynamics(CFD) chamber model for simulating formaldehyde emission in twelve different cases was developed for obtaining formaldehyde concentration by the area-weighted average method.Laboratory experiments were conducted in an environment chamber to validate the simulation results of twelve different cases and the formaldehyde concentration was measured by continuous sampling.The results show that there was good agreement between the model prediction and the experimental values within 4.3 difference for each case.The CFD simulation results varied in the range from 0.21 mg/m3 to 0.94 mg/m3,and the measuring results in the range from 0.17 mg/m3 to 0.87 mg/m3.The variation trend of formaldehyde concentration with supply air rate and temperature variation for CFD simulation and experiment measuring was consistent.With the existence of steady formaldehyde emission sources,formaldehyde concentration generally increased with the increase of temperature,and it decreased with the increase of air supply rate.We also provided some reasonable suggestions to reduce formaldehyde concentration and to improve indoor air quality for newly decorated rooms.
基金Funded by the National High Technology Research and Development Program of China(863 Program)(No.2012AA100604)
文摘Bio-ceramsite technology is one of the most effective technologies in the pretreatment of drinking water. In this work, bio-ceramsite was fabricated by Citrobacter freundii(C. freundii) immobilization on the ceramsite. The fi ndings of the current study suggest that the bio-ceramites showed biosorption abilities for Cd(II) and Pb(II) and the removal efficiency for Pb(II) is lower than Cd(II). The adsorption mechanism can be attributed to electrostatic attraction and covalent bond. The morphology of the cells changed after the adsorption of Cd(II) and Pb(II) due to the dissociation of the assembly of peptidoglycan and lipopolysaccharide. The fluorescence polarization has shown a significant decrease in membrane fluidity and an increase of permeability of cell membrane. The spectral profi le of C. freundii suggests the alteration of carbonyl, amide and phosphonic groups on the cell membrane.
文摘To quantize the difficulty level of dust production on the surface of different types of farmland,the Marticorena threshold frictional velocity pattern was used in this study to simulate the dust threshold frictional velocity.The results showed that the dust threshold frictional velocity of desertification farmland was 7.39cm/s,while it was 29.05 cm/s after the wheat harvested and the farmland ploughed; the turning green period was 46.85 cm/s; shooting period was 98.93 cm/s,the uncovered and the establishment period of fruit tree farmland was 26.0 and 139.15 cm/s.It was concluded that,bare desertification farmland could be changed into source of dust release easier.
文摘Improving the soil and biomass with coal is estimated at the international level as a way to enhance soil productiveness, fertility and also to mitigate climate change. Biochar employed to improve land scope and impound carbon, is attracting a great deal of attention. Its characteristics of chemical, physical and biological properties, containing big surface area, CEC (Cation Exchange Capacity), high water-holding capacity, size of pore, volume, distribution, and element composition, affect its recognized influences, particularly on microbial communities. These are discovered in the agriculture lands, lands remediation and composting. However, incomplete information existed about biochar for several farmers or peasants in agriculture scope. Therefore, farmers or peasants and gardeners are facing new opportunities and defiance each day, from feeding global extending and expanding population, whilst meeting severe new emissions requirements, to create more food on fewer land area while reducing their environmental emissions. Widespread application and utilization of biochar in agricultural scope, forestry production, energy, environmental protection and additional areas, has interested awareness by scientists and investigators inside and/or outside the country. The objective of this paper is to provide a guide for the farmers or peasants and gardeners with an essential information about biochar and what the ability of biochar can be achieved in the soil, and which can provide the scientific reference for the biochar application, and to get high yield and good quality of crops in all of different soils.
