A REVIEW OF HEAVY METAL ADSORPTION BY MARINE ALGAE

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｔｏｘｉｃｉｔｙｏｆｈｅａｖｙｍｅｔａｌｓｒｅｌｅａｓｅｄｉｎｔｏｔｈｅｅｎｖｉｒｏｎｍｅｎｔｈａｓｒｅｃｅｎｔｌｙｔｒｉｇｇｅｒｅｄａｎｕｍｂｅｒｏｆｓｔｕｄｉｅｓａｉｍｉｎｇａｔｔｈｅｒｅｍｏｖａｌｏｆｍｅｔａｌｉｏｎｓｆｒｏｍａｑｕｅｏｕｓｓｏｌｕｔｉｏｎｓ (ＦｏｕｒｅｓｔａｎｄＶｏｌｅｓｋｙ ,1 997;ＦｅｈｒｍａｎｎａｎｄＰｏｈｌ,1 993 ;ＫｕｙｕｃａｋａｎｄＶｏｌｅｓｋｙ,1 989) .Ｉｔｗａｓｆｏｕｎｄｔｈａｔｔｈｅａｃｃｕｍｕｌａｔｉｏｎｏｆｈｅａｖｙｍｅｔａ…     

EFFECTS OF COMPOSITION AND STRUCTURE OF ALGINATES ON ADSORPTION OF DIVALENT METALS

Results of a series of experiments(on the adsorption of divalent metal ions by dried alginic acid, Na and Ca alginates of different composition and block structure) conducted in this systematic study of the effects of the composition and structure of alginates on the static adsorption equilibrium of divalent metal ions indicate that the properties of alginate adsorption to divalent metal ions are highly different, depending not only on the cations used, but also on the form and structure of the alginates. There is close correlation between the adsorption properties and the structure of the alginates. The selectivity coefficient of Na alginate for Cd-Sr ion exchange tends to increase with the increase of the M/G ratio in alginate, whereas the adsorption capacity of Ca alginate for Cu~(2+) ion decrease with the increase of the G-block or the average length of the G-block ((?)_G) and the total adsorption capacity of alginic acid is found to vary in the same order as the F_(MM)(diad frequency) in alginate in     

KINETICS OF LEAD ADSORPTION BY XIAMEN BAY SEDIMENTS

The kinetics of Pb adsorption in seawater by surface sediments from Xiamen Bay was simulated and the effects of seawater conditions were studied . When water temperature changed from 20 to 30℃, pH from 5 to 8 and salinity from 30 to 4 . the adsorption rate increased by about 50% , one order of magnitude and 5 times, respectively . A negative exponential relation between the adsorption rate and salinity has been found . The adsorption processes can be simulated by the exchange- equilibrium kinetic model . Adsorption rate constant, apparent activation energy and equilibrium adsorptive capacity have been quantitatively determined . The adsorption of Pb by sediments is essentially a chemical action .     

Effects of composition and structure of alginates on adsorption of divalent metals

Results of a series of experiments (on the adsorption of divalent metal ions by dried alginic acid, Na and Ca alginates of different composition and block structure) conducted in this systematic study of the effects of the composition and structure of alginates on the static adsorption equilibrium of divalent metal ions indicate that the properties of alginate adsorption to divalent metal ions are highly different, depending not only on the cations used, but also on the form and structure of the alginates. There is close correlation between the adsorption properties and the structure of the alginates. The selectivity coefficient of Na alginate for Cd-Sr ion exchange tends to increase with the increase of theM/G ratio in alginate, whereas the adsorption capacity of Ca alginate for Cu²⁺ ion decrease with the increase of the G-block or the average length of the G-block and the total adsorption capacity of alginic acid is found to vary in the same order as theF _MM(diad frequency) in alginate in the mixed solution of Sr²⁺, Ba²⁺ and Cd²⁺. Contribution No. 2166 from the Institute of Oceanology, Chinese Academy of Sciences.     

大孔树脂纯化菠萝皮黄酮类化合物的研究

通过静态吸附与解吸实验,比较7种树脂对菠萝皮黄酮类化合物的吸附和解吸特性,筛选出较优的菠萝皮黄酮类化合物吸附剂,并检测吸附流速、上样液浓度、pH值、洗脱流速、洗脱剂体积分数等动态吸附性能。结果表明:AB-8树脂具有较好的吸附和解吸效果,吸附流速1mL/min、上样液浓度2.25mg/mL、pH值6、洗脱流速0.5mL/min、洗脱剂体积分数90%条件下,AB-8型大孔树脂可用于菠萝皮黄酮类化合物的分离纯化。     

Decomposition of algal lipids in clay-enriched marine sediment under oxic and anoxic conditions

A series of laboratory incubation experiments were conducted to examine the decomposition of algal organic matter in clay-enriched marine sediment under oxic and anoxic conditions. During the 245-day incubation period, changes in the concentrations of TOC, major algal fatty acid components (14:0, 16:0, 16:1, 18:1 and 20:5), and n-alkanes (C₁₆–C₂₃) were quantified in the samples. Our results indicate that the organic matters were degraded more rapidly in oxic than anoxic conditions. Adsorption of fatty acids onto clay minerals was a rapid and reversible process. Using a simple G model, we calculated the decomposition rate constants for TOC, n-alkanes and fatty acids which ranged from 0.017–0.024 d⁻¹, 0.049–0.103 d⁻¹ and 0.011 to 0.069 d⁻¹, respectively. Algal organic matter degraded in two stages characterized by a fast and a slow degradation processes. The addition of clay minerals montmorillonite and kaolinite to the sediments showed significant influence affecting the decomposition processes of algal TOC and fatty acids by adsorption and incorporation of the compounds with clay particles. Adsorption/association of fatty acids by clay minerals was rapid but appeared to be a slow reversible process. In addition to the sediment redox and clay influence, the structure of the compounds also played important roles in affecting their degradation dynamic in sediments.     

SYNTHESIS AND PROPERTIES OF SULFHYDRYL CHITOSAN

A new adsorbent for heavy metal ions, sulfhydryl chitosan (S-chitosan), was produced by treatment of chitosan with sulhydryl acetic acid in the presence of sulfuric acid as a catalyst. Its structure was confrrmed by elemental analysis and FI‘-IR spectra analysis. The adsorption properties of sulthydryl chitosan for Cu(Ⅱ ), Cd(Ⅱ ), Pb(Ⅱ), Cr(Ⅲ) and Ni(Ⅱ) were investigated, and the effect of pH value on adsorption, adsorption kinetics, and selective adsorption was examined. It was shown that S-chitosan has good adsorption for Pb(Ⅱ), Cu(Ⅱ) and Cd(Ⅱ) like chitosan, is also insoluble in acid solution; has good adsorption kinetic properties for heavy metal ions; and can be used in acid solution. The adsorption capacities of S-chitosan can be affected by media acidity. The adsorbed Cu(Ⅱ) Cd(Ⅱ) and Pb(Ⅱ) could be eluted by diluted chlorhydric acid.     

Optimization of preparative separation and purification of total polyphenols from Sargassum tenerrimum by column chromatography

Polyphenols from the ethanol extracts of Sargassum tenerrimum (ST) with potent antiallergic effects were studied to optimize separation process through column chromatography. The adsorption and desorption characteristics of three widely used adsorbents: macroporous resin, silica gel, and polyvinylpolypyrrolidone (PVPP), were critically evaluated respectively and studied for the optimization of preparative separation of polyphenols. Static operations on these adsorbents showed that macroporous resin had the best adsorption and desorption capability among the three adsorbents. Dynamic adsorption and desorption with macroporous resin packed column were also conducted to optimize the parameters such as: with the optimal values shown in brackets, the concentration of extract solution (4 times diluted), pH value (6–7), adsorption speed (3 BV h⁻¹, bed volumes/per hour), concentration of ethanol (80%), elution speed (3 BV h⁻¹) and elution volume (7 BV). The chromatographic process so optimized gave a purity of 62.43% from the crude polyphenols, providing a promising basis for large scale preparation of bioactive polyphenols upon further scaling up tests.     

Capacities and failure modes of suction bucket foundation with internal bulkheads

Suction bucket foundations can be divided into four compartments by cruciform internal bulkheads, thereby yielding better capacity in certain conditions than those without internal bulkheads. As yet, no systematic study has been conducted regarding the effects of cruciform internal bulkheads on the capacities of suction bucket foundations. In this study, we established a large number of finite element models of suction bucket foundations with and without cruciform internal bulkheads and of solid embedded circular foundations. We found the uniaxial capacities and failure modes of suction bucket foundations with various depth ratios to remain basically unaffected by internal bulkheads in uniform clays. However, in inhomogeneous clay with high strength heterogeneity, we observed the uniaxial moment and horizontal capacities and corresponding failure modes of suction bucket foundations with a low depth ratio to be obviously affected by internal bulkheads. In this case, the uniaxial moment capacities, in particular, as well as the horizontal capacities of suction bucket foundations with cruciform internal bulkheads become obviously greater than those without internal bulkheads. Under combined loading, we found the failure envelopes of suction bucket foundations with and without cruciform internal bulkheads and of solid circular foundation to also be basically consistent in uniform clays. However, in inhomogeneous clay with high strength heterogeneity, cruciform internal bulkheads can obviously change the shapes of the failure envelopes of bucket foundations with a small depth ratio. We conclude that when the acting vertical load or foundation depth is relatively small, suction bucket foundations with cruciform internal bulkheads can be subjected to larger moment and horizontal loads in soft clays with high strength heterogeneity.     

CO_2改性水玻璃砂的热强度、高温强度和发气性

研究了CO2改性水玻璃砂的热强度、高温强度和发气性,结果表明,随着粘结剂加入量的增加,热强度、高温强度和发气性增大;粘结剂种类不同,型砂的热强度、高温强度和发气性不同;其中,l#改性树脂改性水玻璃18#的热强度、高温强度均比普通水玻璃高,发气量则小于普通水玻璃;用扫描电镜分别观察了普通和改性水玻璃砂在加热温度为600℃、800℃、1000℃、1200℃时的高温炉内折断断口,解释了改性水玻璃砂比普通水玻璃砂高温强度高的原因。     

Optimization of Culturing Condition and Medium Composition for the Production of Alginate Lyase by a Marine Vibrio sp. YKW-34

Carbohydrases secreted by marine Vibrio sp. YKW-34 with strong Laminaria cell wall degrading ability were screened, and among them alginate lyase was found to be dominant. The effects of medium composition and culturing condition on the production of alginate lyase by marine Vibrio sp. YKW-34 in flask were investigated in this study. In the culture medium of marine broth, no alginate lyase was produced. The activity of the alginate lyase, after being induced, reached 5 UmL^-1. The best inoculum volume and inoculum age were 10% and 12h, respectively. The optimal temperature for alginate lyase production was 25℃. The fermentation medium was composed of 0.5% of Laminaria powder and 0.2% of KNO3 with an initial acidity of pH 8.0. Alginate could induce alginate lyase production but not as efficiently as Laminaria powder did. The addition of fucoidan, cellulose and glucose had negative effect on the alginate lyase production. Other kinds of nitrogen sources, such as yeast extract, beef extract and peptone, had positive effect on the growth of the microorganism and negative effect on alginate lyase production. In addition, the time course of alginate lyase production under the optimized condition was described. The optimal harvest time was 48 h.     

Preparation of adsorbent with magnesium sulfate and straw pulp black liquor and its phenol adsorption properties

A magnesia adsorbent was prepared from straw pulp black liquor and magnesium sulfate for the first time, and its adsorption of phenol from aqueous solution was examined. The characteristics of the adsorbent were tested through chemical analysis, surface analysis, X-ray diffraction and FT-IR spectroscopy. The effects of various factors, such as dose, adsorption time and adsorption temperature, on phenol adsorption behavior were studied. The results show that the adsorption processes can be fitted to the isotherm Langmuir model very well. It was found that the adsorption process was strongly influenced by temperature and the optimal temperature for phenol removal was 40 °C. The optimum adsorption time was 10 min, and desorption would happen afterwards. Between the models of Langmuir and Freundlich, the adsorption process of phenol onto magnesia fitted the Langmuir equation better.     

The effect of grain size on the viscosity and yield stress of fine-grained sediments

In debris flow modelling,the viscosity and yield stress of fine-grained sediments should be determined in order to better characterize sediment flow.In particular,it is important to understand the effect of grain size on the rheology of fine-grained sediments associated with yielding.When looking at the relationship between shear stress and shear rate before yielding,a high-viscosity zone（called pseudoNewtonian viscosity） towards the apparent yield stress exists.After yielding,plastic viscosity（called Bingham viscosity） governs the flow.To examine the effect of grain size on the rheological characteristics of fine-grained sediments,clay-rich materials（from the Adriatic Sea,Italy; Cambridge Fjord,Canada; and the Mediterranean Sea,Spain）,silt-rich debris flow materials（from La Valette,France） and silt-rich materials（iron tailings from Canada） were compared.Rheological characteristics were examined using a modified Bingham model.The materials examined,including the Canadian inorganic and sensitive clays,exhibit typical shear thinning behavior and strong thixotropy.In the relationships between the liquidity index and rheological values（viscosity and apparent yield stress）,the effect of grain size on viscosity and yield stress is significant at a given liquidity index.The viscosity and yield stress of debris flow materials are higher than those of low-activity clays at the same liquid state.However the viscosity and yield stress of the tailings,which are mainly composed of silt-sized particles,are slightly lower than those of low-activity clays.     

Fractal dimensions of flocs between clay particles and HAB organisms

The impact of harmful algal blooms (HABs) on public health and related economics have been increasing in many coastal regions of the world. Sedimentation of algal cells through flocculation with clay particles is a promising strategy for controlling HABs. Previous studies found that removal efficiency (RE) was influenced by many factors, including clay type and concentration, algal growth stage, and physiological aspects of HAB cells. To estimate the effect of morphological characteristics of the aggregates on HAB cell removal, fractal dimensions were measured and the RE of three species of HAB organism, Heterosigma akashiwo, Alexandrium tamarense, and Skeletonema costatum, by original clay and modified clay, was determined. For all HAB species, the modified clay had a higher RE than original clay. For the original clay, the two-dimensional fractal dimension (D2) was 1.92 and three-dimensional fractal dimension (D3) 2.81, while for the modified clay, D2 was 1.84 and D3 was 2.50. The addition of polyaluminum chloride (PACl) lead to a decrease of the repulsive barrier between clay particles, and resulted in lower D2 and D3. Due to the decrease of D3, and the increase of the effective sticking coefficient, the flocculation rate between modified clay particles and HAB organisms increased, and thus resulted in a high RE. The fractal dimensions of flocs differed in HAB species with different cell morphologies. For example, Alexandrium tamarense cells are ellipsoidal, and the D3 and D2 of flocs were the highest, while for Skeletonema costatum, which has filamentous cells, the D3 and D2 of flocs were the lowest.     

A Laboratory Column Study on Particles Release in Remediation of Seawater Intrusion Region

In coastal areas, excessive exploitation of groundwater causes seawater intrusion. In artificial recharge of aquifer remediation process, the replacement of saltwater and freshwater with each other causes colloid release, and permeability also decreases. In this paper, the aquifer samples containing minimal clay mineral(mainly illite) in Dagu River aquifer were used. Adopting horizontal column experiments, we studied the influences of seepage velocity and ionic strength on particle release, as well as the relationship between them. In the column experiments, the Critical Salt Concentration(CSC) of the Dagu River aquifer was determined as 0.05 mol L~(-1) approximately. This result was basically consistent with the DLVO theoretical calculation. For the constant seepage velocity, the salinity descending rate and partical release were slower, and the peak of particle concentration was lower. However, the total amount of released particles was almost constant at different salinity descending rate. For constant salinity descending rates, the peak of particle concentration decreased as seepage velocity increased, but the total amount of released particles rose up. The experiments also indicated the existence of a critical seepage velocity, which dropped with the decrease of salt concentration. When the concentration of Na Cl solution decreased from 0.17 mol L~(-1) to 0.06 mol L~(-1), the critical seepage velocity decreased from 3 cm min~(-1)to 2.5 cm min~(-1), which is consistent to the results predicted by DLVO theory.     

纳米塑料颗粒在饱和多孔介质中的迁移规律

针对纳米塑料颗粒在饱和多孔介质中的迁移及其影响因素, 以纳米聚苯乙烯(PSNPs)作为典型纳米塑料颗粒, 通过实验和理论相结合的方法研究纳米塑料颗粒的迁移规律。以经典DLVO理论计算出PSNPs与石英砂颗粒之间的相互作用能, 分析预测PSNPs与石英砂之间的吸附、聚沉。在柱实验中, 以石英砂作为多孔介质填充到砂柱中, 让PSNPs在一维饱和砂柱中迁移, 研究不同条件下PSNPs的迁移行为和影响因素。结果表明, 当离子强度由1 mmol/L增至50 mmol/L(电解质为NaCl), PSNPs与石英砂颗粒之间的相互作用能的势垒则从215.13 KT逐渐降低至45.9 KT使得PSNPs更易于吸附在石英砂介质表面, 从而降低PSNPs在多孔介质中的迁移能力, PSNPs的穿透率由62.16%降至3.65%。当离子强度由0.1 mmol/L增至5 mmol/L(电解质为CaCl₂)时, 势垒则由33.72 KT降至14.03 KT, PSNPs的穿透率从82.46%降至4.27%。这些实验现象说明增加离子强度对PSNPs的穿透起到抑制作用, 且Ca2+比Na+具有更强的电荷屏蔽作用。同时提高PSNPs的初始浓度、流速和介质粒径均可增大PSNPs的穿透率, 而大粒径PNSPs颗粒的穿透率则较小。研究中构建了PSNPs实际运移与理论之间的关系, 进一步推进PSNPs的环境行为和机理研究, 为系统全面评价纳米塑料颗粒在土壤-地下水中的环境风险和生态安全提供科学依据。      

印度洋西北部海域鸢乌贼的触腕和腕足钓捕断裂强度

鱿鱼的腕足断裂强度是影响鱿钓脱钩率的重要因素。通过现场实测，分析了印度洋西北部海域鸢乌贼（Symplectoteuthis oualaniensis）的腕足断裂强度对手钓作业脱钩率产生的影响。结果表明，鸢乌贼的每根触腕仅能承受的拉力相当于体重的0．7倍，因此，钓捕过程中，因触腕断裂造成的脱钩率接近100％；而另外的第Ⅰ一Ⅳ腕足的断裂强度分别是其体重的2．30、2．05、2．06和1．87倍；5对腕足整体的平均脱钩率接近10％。     

印度洋西北部海域鸢乌贼的触腕和腕足钓捕断裂强度

鱿鱼的腕足断裂强度是影响鱿钓脱钩率的重要因素。通过现场实测,分析了印度洋西北部海域鸢乌贼(Symplectoteuthis oualaniensis)的腕足断裂强度对手钓作业脱钩率产生的影响。结果表明,鸢乌贼的每根触腕仅能承受的拉力相当于体重的0.7倍,因此,钓捕过程中,因触腕断裂造成的脱钩率接近100%;而另外的第I-IV腕足的断裂强度分别是其体重的2.30、2.05、2.06和1.87倍;5对腕足整体的平均脱钩率接近10%。     

A novel model to assess soil productivity in the dry-hot valleys of China

Accurate evaluation of soil productivity has been a long-standing challenge. Although numerous models for productivity assessment exist, most are cumbersome to use and require substantial parameter inputs. We developed a new empirical soil productivity model based on field investigations of soil erosion, soil physicochemical properties, and crop yields in the dry-hot valleys (DHVs) in China. We found that soil pH, and organic matter and available potassium contents significantly affected crop yields under eroded conditions of the DHVs. Moreover, available potassium content was the key factor affecting soil productivity. We then modified an existing soil productivity model by adding the following parameters: contents of effective water, potassium, organic matter, and clay, soil pH, and root weighting factor. The modified soil productivity model explained 63.5% of the crop yield. We concluded that the new model was simple, realistic, and exhibited strong predictability. In addition to providing an accurate assessment of soil productivity, our model could potentially be applied as a soil module in comprehensive crop models.     

Drying of Micro-Encapsulated Lactic Acid Bacteria—Effects of Trehalose and Immobilization on Cell Survival and Release Properties

Lactic acid bacteria (LAB) were encapsulated with alginate, gelatin and trehalose additives by the extrusion method and dried at 4 ℃. The microcapsules were generally spherical and had a wrinkled surface with a size of 1.7 mm ± 0.2 mm. Trehalose as a carbohydrate source in the culture medium could reduce acid production and performed no function in the positive proliferation of LAB. Using trehalose as a carbohydrate source and protective medium simultaneously had a benefit in the protection of LAB cells dur...