非饱和土抗剪强度随含水量变化的试验研究

在土力学中,非饱和土的抗剪强度一直是研究人员所关注的重点。土体的抗剪强度随含水量的不同变化明显。试验以云南某重塑土为研究对象,采用常规直接剪切试验为手段,对不同含水量土样的抗剪强度参数进行测定。试验结果表明,土样的抗剪强度不是单调地随含水量的增加而降低,而是呈现出有起有伏的抛物线状,对进一步认识土体强度随含水量变化规律有积极意义。     

Trophic importance of diatoms in an intertidal Zostera noltii seagrass bed: Evidence from stable isotope and fatty acid analyses

A current predominant paradigm emphasizes the role of epiphytic algae for invertebrates in most seagrass food webs. However, in some intertidal Zostera noltii beds, epiphyte biomass is very low compared to microphytobenthos and seagrass biomasses. We assessed the role of microphytobenthos in a temperate intertidal Z. noltii bed by combining stable isotope and fatty acid (FA) analyses on primary producers, composite sources — suspended particulate organic matter (SPOM) and sediment surface organic matter (SSOM) — and the main macrofaunal consumers. Z. noltii showed high δ¹³C (−9.9‰) and high 18:2(n-6) and 18:3(n-3) contents. Microphytobenthos was slightly more ¹³C-depleted (−15.4‰) and had high levels of diatom markers: 14:0, 16:1(n-7)c, 20:5(n-3). Low mean δ¹³C (−22.0‰) and large amounts of diatom and bacteria (18:1(n-7)c) markers indicated that SPOM was mainly composed of a mixture of fresh and decayed pelagic diatoms. Higher mean δ¹³C (−17.9‰) and high amounts of diatom FAs were found in SSOM, showing that microphytobenthic diatoms dominate. Very low percentages of 18:2(n-6) and 18:3(n-3) in consumers indicated a low contribution of Z. noltii material to their diets. Grazers, deposit and suspension-deposit feeders had δ¹³C close to microphytobenthos and high levels of diatom FAs, confirming that microphytobenthos represented the main part of their diet. Lower δ¹³C and higher amounts of flagellate FAs – 22:6(n-3) and 16:4(n-3) – in suspension feeders indicated that their diet resulted from a mixture of SPOM and microphytobenthos. These results demonstrate that invertebrates do not consume high amounts of seagrass and highlight the main role of benthic diatoms in this intertidal seagrass bed.     

The response of phytoplankton to iron enrichment in Sub-Antarctic HNLCLSi waters: Results from the SAGE experiment

Areas of high nutrients and low chlorophyll a comprise nearly a third of the world’s oceans, including the equatorial Pacific, the Southern Ocean and the Sub-Arctic Pacific. The SOLAS Sea-Air Gas Exchange (SAGE) experiment was conducted in late summer, 2004, off the east coast of the South Island of New Zealand. The objective was to assess the response of phytoplankton in waters with low iron and silicic acid concentrations to iron enrichment. We monitored the quantum yield of photochemistry (F_v/F_m) with pulse amplitude modulated fluorometry, chlorophyll a, primary productivity, and taxonomic composition. Measurements of F_v/F_m indicated that the phytoplankton within the amended patch were relieved from iron stress (F_v/F_m approached 0.65). Although there was no significant difference between IN and OUT stations at points during the experiment, the eventual enhancement in chlorophyll a and primary productivity was twofold by the end of the 15-day patch occupation. However, no change in particulate carbon or nitrogen pools was detected. Enhancement in primary productivity and chlorophyll a were approximately equal for all phytoplankton size classes, resulting in a stable phytoplankton size distribution. Initial seed stocks of diatoms were extremely low, <1% of the assemblage based on HPLC pigment analysis, and did not respond to iron enrichment. The most dominant groups before and after iron enrichment were type 8 haptophytes and prasinophytes that were associated with ∼75% of chlorophyll a. Twofold enhancement of biomass estimated by flow cytometry was detected only in eukaryotic picoplankton, likely prasinophytes, type 8 haptophytes and/or pelagophytes. These results suggest that factors other than iron, such as silicic acid, light or physical disturbance limited the phytoplankton assemblage during the SAGE experiment. Furthermore, these results suggest that additional iron supply to the Sub-Antarctic under similar seasonal conditions and seed stock will most likely favor phytoplankton <2 ??m. This implies that any iron-mediated gain of fixed carbon will most likely be remineralized in shallow water rather than sink and be sequestered in the deep ocean.     

HPLC法同步检测鲤鱼、对虾中喹乙醇与MQCA残留

建立了一种高效液相色谱法同时检测鲤鱼、对虾肌肉组织中喹乙醇（OLA）及其代谢物3-甲基-喹啉-2-羧酸（MQCA）的残留。采用0.3 mol/L 盐酸提取鲤鱼、对虾中的残留物, C18 固相萃取柱净化, 氮气吹干及流动相定容后, Waters2695 高效液相色谱仪在320 nm（MQCA）和372 nm（QLA）双波...     

高古罗糖醛酸含量的萱藻(Scytosiphon lomentarius)多糖细微结构研究

将青岛产幼生和成熟期萱藻(Scytosiphon lomentarius)提取分离得到多糖,经<'1>H-NMR分析,表明其为高古罗糖醛酸含量的褐藻胶,在对其G/M值分析基础上,进一步对其二糖嵌段F<,MM>,F<,MG>,F<,GM>,F<,GG>和三糖嵌段F<,GGG>,F<,GGM>,F<,MGM>,F<,MGG...     

吲哚乙酸对微拟球藻生长和脂肪酸含量的影响

研究不同浓度吲哚乙酸(Indole-3-Acetic Acid,IAA)对微拟球藻(Nannochloropsis oculata)生长和脂肪酸组成的影响。结果表明:在0.1 mg/L时,低于0.5 mg/L时IAA促进微拟球藻生长,但不影响叶绿素和不饱和脂肪酸合成;IAA促进生长作用最显著,最大比生长率为2.33 d-1。随浓度进一步增加,IAA促生长作用越来越小,并抑制叶绿素和不饱和脂肪酸合成;在5 mg/L时,IAA极显著抑制EPA合成。添加适当浓度IAA可促进藻细胞生长,缩短其生长周期。     

海南八门湾红树林柱状沉积物中有机生物标志物的分布和降解

对海南岛红树林柱样中有机生物标志物等生物地球化学参数进行了初步研究.结果显示红树林中有机碳(OC)与总氮(TN)比值范围为5.35-7.47,碳稳定同位素(δ13C)值范围为-25‰--22.9‰.脂肪酸与正构烷烃浓度分布范围分别为7.8-21.8μg·g-1(干重)和3.2-25μg·g-1(干重).在表层沉积物中,红树林植物、细菌与浮游生物的脂肪酸生物标志物各占总脂肪酸的25.4%、12.9%和7.5%,结合较低的OC/TN比值和较高的δ13C值,表征了当地微生物和外源浮游植物的有机质贡献.各类脂肪酸在柱样中表现出不同的降解特征:多不饱和脂肪酸(PUFAs)优先被降解,而长链脂肪酸(LCFAs)则较为稳定,没有明显的降解.碳优势指数(CPI)和平均碳链长度(ACL)显示,埋藏深度越深,有机物的生物化学改造程度越大.     

黑海参脂肪酸的气相色谱/质谱法分析

黑海参(Holothuria atra)体壁经Folch 法提取总脂, 用HCl-甲醇进行甲酯化处理, 以气相色谱/质谱法分析总脂中的脂肪酸组成。从黑海参中共分析出28 种化合物, 包括25 种脂肪酸甲酯和3 种脂肪醛二甲基缩醛。黑海参体壁中的饱和脂肪酸含量为22.93%, 以C_16:0(5.49%)和C_18:0(4.38%)为主; 不饱和脂肪酸含量为65.19%, 其中单不饱和脂肪酸33.86%, 主要为C_20:1(n-9)(15.90%); 多不饱和脂肪酸为31.33%, 主要为C_20:4(n-6)(19.57%)和C_20:5(n-3)(5.86%)。脂肪醛二甲基缩醛含量为7.28%, 表明黑海参体壁总脂中含有较丰富的缩醛型甘油酯。