Studies on growth rate and grazing mortality rate by microzooplankton of size-fractionated phytoplankton in spring and summer in the Jiaozhou Bay,China

Dilution experiments were performed to examine the growth rate and grazing mortality rate of size-fractionated phytoplankton at three typical stations, inside and outside the bay, in the spring and summer of 2003 in the Jiaozhou Bay, China. In spring, the phytoplankton community structure was similar among the three stations, and was mainly composed of nanophytoplankton, such as, Skeletonema costatum and Cylindrotheca closterium. The structure became significantly different for the three stations in summer, when the dominant species at Stas A, B and C were Chaetoceros curvisetus, Pseudo-nitzschia delicatissima, C. affinis, C. debilis, Coscinodiscus oculus-iridis and Paralia sulcata respectively. Tintinnopsis beroidea and T. tsingtaoensis were the dominant species in spring, whereas the microzooplankton was apparently dominated by Strombidium sp. in summer. Pico- and nanophytoplankton had a relatively greater growth rate than microzooplankton both in spring and summer. The growth rate and grazing mortality rate were 0.18~0.44 and 0.12~1.47 d-1 for the total phytoplankton and 0.20~0.55 and 0.21~0.37 d-1 for nanophytoplankton in spring respectively. In summer, the growth rate and grazing mortality rate were 0.38~0.71 and 0.27~0.60 d-1 for the total phytoplankton and 0.11~1.18 and 0.41~0.72 d-1 for nano- and microphytoplankton respectively. The carbon flux consumed by microzooplankton per day was 7.68~39.81 mg/m3 in spring and 12.03~138.22 mg/m3 in summer respectively. Microzooplankton ingested 17.56%~92.19% of the phytoplankton standing stocks and 31.77%~467.88% of the potential primary productivity in spring; in contrast, they ingested 34.60%~83.04% of the phytoplankton standing stocks and 71.28%~98.80% of the potential primary productivity in summer. Pico- and nanophytoplankton appeared to have relatively greater rates of growth and grazing mortality than microphytoplankton during the experimental period. The grazing rate of microzooplankton in summer was a little bit greater than that in spring because of the relatively higher incubation temperature and different dominant microzooplankton species. Microzooplankton preferred ingesting nanophytoplankton to microphytoplankton in spring, while they preferred ingesting picophytoplankton to nanophytoplankton and microphytoplankton in summer. Compared with the results of dilution experiments performed in various waters worldwide, the results are in the middle range.

Comparing the soil quality changes of different land uses determined by two quantitative methods

Soil quality is one of the most important environmental factors in sustaining the global biosphere and developing sustainable agricultural practices. A study was initiated in Wolong Nature Reserve, Sichuan Province, China to elucidate the soil quality changes of natural secondary succession, forest planting and agricultural practices after deforestation in the humid mountainous region. The soil qualities of six land use types (natural forestland, grassland, shrub land, secondary forestland, cultivated land and reforested land) were compared using two quantitative methods: the integrated soil quality index(QI) and soil deterioration index(DI). The QI values of natural forestland, grassland, shrub land, secondary forestland, cultivated land, reforested land were 0.8039, 0.3277, 0.9127, 0.6881, 0.0285 and 0.3183, respectively. The DI values were 0%, -14%, 12%, 1%, -26% and -18% respectively. Both indexes suggested that shrub land can restore soil properties. To compare the two methods more directly, a deduced index QI′ based on QI value was developed. The results showed that DI and QI′had a very high linear correlation coefficient (r=0.9775) despite the values were different. Both methods were efficient in evaluating the soil quality levels and DI was a more simple way in soil quality assessment, while QI could show more ecological meanings.

The effects of spring-neap tide on the phytoplankton community development in the Jiaozhou Bay, China

The development of the phytoplankton community was studied in the Jiaozhou Bay during the spring to neap tide in August2001, through three cruises and a 15 d continuous observation. This investigation indicates that diatom cell abundance increasedsharply following the end of a spring tide, from 9 cells/cm3 to a peak of 94 cells/cm3. The dominant species composition andabundance show a quick species sequence from spring to neap tide, and the dominant species at the start phase is Skeletomenacostatum, then changes to Chaetoceros curvisetus, finally it changes to Eucampia zodiacus. Silicate concentration increasesduring spring tide, as a result of nutrient replenishment from the watersediment interface, its initial average concentration inneap tide is 1.39 mmol/dm3 and reached the peak average concentration of 8.40 mmol/dm3 in spring tide. But the nitrogenconcentration dropped due to dilution by the low nitrogen seawater from the Huanghai Sea, its initial average concentration inneap tide is 67 mmol/dm3 and decreased to the average concentration of 54 mmol/dm3 in spring tide. The degree of siliconlimitation was decreased and phytoplankton, especially diatoms, responds immediately after nutrient replenishment in thewater column. Skeletonmea costatum, as one of the dominant species in the Jiaozhou Bay, shows a quicker response tonutrient availability than Eucampia zodiacus and Chaetoceros curvisetus. It is proposed that dominant species compositionand water column stability synchronously determine the development of phytoplankton summer blooms in the Jiaozhou bay.

Phosphorus Uptake and Utilisation Efficiencies of Different Wheat Cultivars Based on a Sand-Culture Screening System

A sand-based culture system using rock phosphate (P) was developed to simulate the situation in alkalinesoils, with respect to the dominant P form, and five wheat cultivars (Excalibur, Brookton, Krichauff, Westoniaand Sunco) were tested in this screening system to compare their P uptake and utilisation efficiencies. Resultsshowed that these cultivars differed significantly in their ability to acquire P from the sparingly available form(rock phosphate in this case). The accumulation of P by Brookton was three times that by Krichauff. Pconcentrations in plant tissues did not differ significantly, indicating that all cultivars were similar in Putilisation efficiency. A further experiment showed that the greater ability of a cultivar to take up P fromsparingly available form was related to the ability of a cultivar to acidify the rhizosphere. Seed P content wasa confounding factor in this system, and the use of relatively uniform seed with similar P content, preferablylow, was conducive to a successful outcome of the screening process.

The effects of land use and its patterns on soil properties in a small catchment of the Loess Plateau

Due to relatively strong human activities in the hilly area of Loess Plateau, the natural vegetation has been destroyed, and landscape pattern based on agricultural land matrix was land use mosaic composing of shrub land, grassland, woodland and orchard. This pattern has an important effect on soil moisture and soil nutrients. The Danangou catchment, a typical small catchment, was selected to study the effects of land use and its patterns on soil moisture and nutrients in this paper. The results are as follows: The comparisons of soil moisture among seven land uses for wet year and dry year were performed: (1) the average of soil moisture content for whole catchment was 12.11% in wet year, while it was 9.37% in dry year; (2) soil moisture among seven land uses was significantly different in dry year, but not in wet year; (3) from wet year to dry year, the profile type of soil moisture changed from decreasing type to fluctuation-type and from fluctuant type to increasing type; (4) the increasing trend in soil moisture from the top to foot of hillslope occurred in simple land use along slope, while complicated distribution of soil moisture was observed in multiple land uses along slope. The relationships between soil nutrients and land uses and landscape positions were analysed: (1) five nutrient contents of soil organic matter (SOM), total N (TN), available N (AN), total P (TP) and available P (AP) in hilly area were lower than that in other areas. SOM content was less than 1%, TN content less than 0.07%, and TP content between 0.05% and 0.06%; (2) SOM and TN contents in woodland, shrub land and grassland were significantly higher than that in fallow land and cropland, and higher level in soil fertility was found in crop-fruit intercropping land among croplands; (3) soil nutrient distribution and responses to landscape positions were variable depending on slope and the location of land use types.

Preliminary Study on the Responses of Three Marine Algae,Ulva pertusa(Chlorophyta),Gelidium amansii(Rhodophyta)and Sargassum enerve(Phaeophyta),to Nitrogen Source and Its Availability

An experiment was designed to select economically valuable macroalga species with high nutrient uptake rates. Such species cultured on a large scale could be a potential solution to eutrophication. Three macroalgae species, Ulva pertusa (Chlorophyta), Gelidium amansii (Rhodophyta) and Sargassum enerve (Phaeophyta), were chosen for the experiment because of their economic values and availability. Control and four nitrogen concentrations were achieved by adding NH + 4 and NO - 3. The results indicate that the fresh weights of all species increase faster than that of control after 5 d culture. The fresh weight of Ulva pertusa increases fastest among the 3 species. However, different species show different responses to nitrogen source and its availability. They also show the advantage of using NH + 4 than using NO - 3. U. pertusa grows best and shows higher capability of removing nitrogen at 200 μmol L -1 , but it has lower economical value. G. amansii has higher economical value but lower capability of removing nitrogen at 200 μmol L -1 . The capability of nitrogen assimilation of S. enerve is higher than that of G. amansii at 200 μmol L -1 , but the former’s increase of fresh weight is lower than those of other two species. Then present preliminary study demonstrates that it is possible to use macroalgae as biofilters and further development of this approach could provide biologically valuable information on the source, fate, and transport of N in marine ecosystems. Caution is needed should we extrapolate these findings to natural environments.

Seed yeast cultivation for salad oil manufacturing wastewater treatment

The mixture of five yeast strains obtained from soil could remove about 85% TOC of oil rich wastewater in batch test. While the highest MLSS was obtained at an N∶C of 1∶5, the oil removal decreased with the increase of N∶C during yeast sludge cultivation. Ammonium chloride was the best nitrogen source for yeast cultivation from the viewpoint of yeast growth and oil utilization. An ammonia concentration of over 1300 mg/L led to mass death of yeast at a pH of 5. The ammonia concentration should be controlled at a level of 1000 mg/L or lower.

Removal of aqueous phenol compound by vacuum membrane distillation

The effects of feed temperature and pH value on the removal of aqueous phenol wastewater by vacuum membrane distillation process are studied by experiments employing micro porous membranes of poly vinylidene fluoride (PVDF) and ploy tetrafluoro ethylene (PTFE) with nominal average pore sizes 0.22 mm and 0.20 mm, respectively. It is found that the optimal feed temperature for PVDF membrane is 50 ℃; and for PTFE membrane, 60 ℃. The pH value of the feed has little influence on the membrane fluxes and ion rejection ratios, while it influenced considerably on the selectivity. Increase of pH value of the feed is conducive to the increase of selectivity. In the same experimental conditions, PTFE membrane shows better separation performance than PVDF membrane does.

Simultaneous catalytic removal of NOx and diesel soot particulate over perovskite-type oxides and supported Ag catalysts

A series of perovskite type oxides and supported Ag catalysts were prepared, and characterized by X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). The catalytic activities of the catalysts as well as influencing factors on catalytic activity have been investigated for the simultaneous removal of NOx and diesel soot particulate. An increase in catalytic activity for the selective reduction of NOx was observed with Ag addition in these perovskite oxides, especially with 5% Ag loading. This catalyst could be a promising candidate of catalytic material for the simultaneous elimination of NOx and diesel soot.

Addition of anaerobic tanks to an oxidation ditch system to enhance removal of phosphorus from wastewater

The oxidation ditch has been used for many years all over the world as an economic and efficient wastewater treatment technology. It can remove COD, nitrogen and a part of phosphorus efficiently. In the experiment described, a pilot scale Pasveer oxidation ditch system has been tested to investigate the removal of phosphorus from wastewater. The experimental results showed that influent total phosphorus(TP) was removed for 35%-50%. After this, two anaerobic tanks with total volume of 11 m 3 were added to the system to release phosphorus. As a result, the TP removal efficiency increased by about 20%. At an anaerobic HRT of about 6 hours, a TP removal efficiency of 71% was achieved.

Particle reworking by the sediment-living polychaetes Perinereis aibuhitensis

The infaunal polychaete Perinereis aibuhitensis Grube, distributes widelyalong Asian coasts and estuaries. In this research the particle reworking function of P.aibuhitensis was investigated in Beitang Estuary, Tianjin. The result showed that P.aibuhitensis displayed significant particle mixing function, in which small grain sizesediment particles were mixed more than the large size ones. Some small grain sizesediment particles could be ingested by P. aibuhitensis and egested with fecal pellets.

Sustainable development pattern and the strategy in the Three Gorges Reservoir Areas

The development pattern, development situation, and existing problems of land exploitation in Zigui County, Three Gorges Reservoir Areas of China were presented. The sustainable development mode and its strategy in the Three Gorges Reservoir Areas was also discussed. A sustainable development framework for low mountain regions, middle mountain regions and high mountain regions was developed, and management countermeasures for structural optimization of complex ecosystems were advanced.

Double catholyte electrochemical approach for preparing ferrate-aluminum: a compound oxidant-coagulant for water purification

Ferrate is an excellent water treatment agent for its multi functions in oxidation, disinfection, coagulation and adsorption, but its coagulation ability depends on its dosage and is after its oxidation. This paper focuses on preparing a new kind of ferrate combined with alum to enhance its coagulation function for water purification. An effective electrolysis reactor was designed and employed in the test. Some key parameters in the process of electrolysis concerning the preparation efficiency, such as the current density, temperature and alkalinity were also investigated. The proper conditions for ferrate alum preparation were determined. Under the condition of 5V given voltage, 6h electrolyzing interval, below 2% alum concentration (in weight), a combined liquid ferrate alum products was successfully prepared, which contained 0.0294 mol/L FeO 2- 4 and 0.0302 mol/L total soluble ferron with 2% Al 2O 3. There was no insoluble ferron produced by controlling an optimum electrochemical condition.

Adsorption of Pb(Ⅱ)in Water by Niobate/Titanate Nanoflakes

A niobate/titanat nanoflakes(Nb/TiNFs)composite was synthesized via the hydrothermal method and used to remove Pb(Ⅱ)from water.XRD,TEM,and SEM results indicate that Nb/TiNFs appear as nanoflakes,of which the primary crystal phase is tri-titanate.Nb/TiNFs show rapid adsorption kinetics and the result fits well with the pseudo-second order model.The key mechanism of adsorption is ion-exchange between metal and-ONa/H.According to the Langmuir isotherm model,the maximum capacity of Pb(Ⅱ)is 488.323 mg·g^-1.The relatively low RL values indicate that Nb/TiNFs exhibit favorable adsorption of Pb(Ⅱ).Nb/TiNFs indicate high adsorption capacity over a broad pH range.Co-existing inorganic ions(Na+and Ca^2+)have a slight inhibition effect on adsorption,and HA moderately inhibits the adsorption of Pb(Ⅱ)on Nb/TiNFs.Because of the simple method of synthesis and high removal efficiency for heavy metals,Nb/TiNFs are a promising material in remediation of heavy metal polluted water.

Joint effects of microwave and chromium trioxide on root tip cells of Vicia faba

The mutagemc effects of microwave and chromium trioxide （CrO3） on Vicia faba root tip were studied. Micronucleus assay and chromosomal aberration assay were used to determine the mitotic index, the micronucleus frequency and chromosomal aberration frequency of Vicia faba root tip cells induced by microwave and CrO3. The results showed that the micronucleus frequency decreased, and that the mitotic index and chromosomal aberration frequency showed linear dose responses to CrO3, in treatment of microwave for 5 s. In microwave of 25 s, the mitotic index decreased, the micronucleus frequency and chromosomal aberration frequency increased with increase of CrO3 concentration. We concluded that microwave and CrO3 had antagonistic effect on the mitotic index of Vicia faba root tip cells, but had synergetic effect on micronucleus frequency and chromosomal aberration frequency of Viciafaba root tip cells.

EFFECT OF CRYOGENIC AND HEATING TREATMENT ON THE SOLUTION PROPERTIES OF NITROCELLULOSE

The effect of cryogenic and heating treatment on the solution properties of rigid polymer nitrocellulose(NC)indilute tetrahydrofuran solution were studied with a sealed viscometer and a size exclusion chromatograph(SEC),respectively.The experimental results show that the relative viscosity of NC solution decreases after repeated freezing-thawing treatment.The decreased viscosity value of NC could not be restored but decreased further after the solution beingre-heated.The experimental results of SEC are fully consistent with that of viscosity measurements.It is believed that theeffect of two treatments on NC solution both causes the apparent hydrodynamic volume to decrease.But they are assumed tobe ascribed to different mechanisms.

Acute and chronic effects of tributyltin on Chinese rare minnow（Gobicypris rarus）

The acute(12-h) and chronic (7 or 14-4) effects of tributyltin chloride(TBT) on a new type of test fish-Chinese rare minnow(Gobiocypris rarus) were studied.High accumulations of the pollutant in the fish muscle were observed after exposure.In chronic exposed group,hepatosomatic index and gonad somatic index occurred obvious changes.The ultrastructural findings showed a series of pathological changes such as the fractured or distorted nuclear,fomation of self-devouring bubble,many vacuoles existing in the exposed gill cells or hepatocytes,which demonstrated the toxic effects of tributyltin compounds on aquatic organisms.The results clearly showed that Chinese rare minnow was a new sensitive test fish,whose exposed system was suitable for the extensive organometallic toxicity studies.