三种海洋微藻生长期脂肪酸组成研究

球等鞭金藻、盐藻和小球藻脂肪酸组成气相色谱分析的结果表明 ,三种海洋微藻在指数生长期总多不饱和脂肪酸含量 (TPUFA)明显比稳定生长期高 ,而总饱和脂肪酸含量 (TSFA)在指数生长期间相对较低。球等鞭金藻的DHA ,小球藻的EPA和盐藻的C18∶3均在培养后的第 6d均达最大值。     

苯甲酸类化合物好氧生物降解性研究

采用从城市污水处理场活性污泥中培养的混合菌种,研究了苯甲酸、邻一、间一、对-苯二甲酸的生物降解。考察了在50,200,400和600mg/l四个浓度梯度下,四种化合物的浓度与生物降解性的关系。研究了苯环上不同羧基数量和取代基位置不同所表现出的降解难易程度上的差异。研究结果表明,在试验周期内,上述四种化合物均有不同程度的降解,四种化合物的可降解性为:邻-苯二甲酸>苯甲酸>对-苯二甲酸>间-苯二甲酸,在评价实验体系的降解性时引入了体系中细菌对化合物的负荷(mg·l~(-1)/个·ml~(-1)),使采用不同菌种量、不同化合物浓度的不同实验装置的研究结果有了相对的可比性。     

腐殖酸对铜的吸附与解吸特征

采用铜离子选择电极研究了铜在腐殖酸两组分(富里酸FA、胡敏酸HA)中的吸附-解吸特征,以及介质pH对这种吸附-解吸的影响。结果表明,腐殖酸对铜的吸附量为FA>HA,吸附强度为HA>FA,解吸量FA-Cu>HA-Cu。腐殖酸两组分对铜的吸附,当介质pH为4.00～7.00时,很好地符合Langmuir等温吸附方程;当pH<4.0时,符合Freundlich方程。FA、HA与铜作用的条件稳定常数与介质pH有关,pH提高则条件稳定常数增大;但在低pH段和高pH段,其增长规律不一致,当4.00相似文献   

离子色谱法同时测定柠檬酸发酵液中无机阴离子和有机酸

本文建立了以ＮａＯＨ为淋洗液，甲醇为有机改进剂，阴离子交换分离，化学抑制型电导检测，快速测定柠檬酸发酵液中有机酸和ＳＯ＾２－４，ＰＬ＾３－４的离子色谱新方法，方法简单，灵敏，用于样品分析，结果令人满意。     

Chemical recognition of queen cells by honey bee workersApis mellifera (Hymenoptera: Apidae)

Summary Honey bee workers are able to nurse or to destroy and thus to recognize the capped queen cells containing a pupa. Fatty acid esters, especially methyl oleate, methyl palmitate and ethyl oleate were found in significant amounts on the queen pupal cuticle. Methyl oleate, the major component, along with smaller amounts of methyl linoleate and methyl linolenate, were involved in the recognition of queen cells by workers. In natural conditions of the colony, queen cells containing a paraffin pupal lure with methyl oleate were accepted 5.9 days by workers, releasing about 1.8 queen pupa equivalents during that period, when control cells (without ester) were kept only 2.1 days. Although these esters are non specific to honey bees, they are of great importance in social regulation of the honey bee colony.     

Tissue distribution of absorbed humic acids

Distribution of humic acids (HA) in rats was studied using radioiodinated HA injected intraperitoneally. Distribution of ¹²⁵I was also studied for comparison. The distribution pattern of HA differed greatly from that of ¹²⁵I. Except in the thyroid and skin, ¹²⁵I was excreted from the body within 24 hours, whereas a large proportion of HA remained in the liver, kidney, skin, thyroid, bone and muscle. The difference in the distribution pattern and organ/serum radioactivity ratio suggests different kinetics for ¹²⁵I and ¹²⁵I-HA. The distribution pattern of HA correlated very well with the increased prevalences of organ diseases in the blackfoot disease endemic area, as reflected in epidemiologic studies. It is hypothesised that HA-metal complexes are possible etiological factors of diseases such as goitre, hepatoma, bladder cancer, vascular disease and diabetes mellitus, and that free radicals are the common causative factor.     

Multi-level complexity in the use of plant allelochemicals by aposematic insects

Summary As recognized by Miriam Rothschild as early as the 1960s and repeatedly emphasized in her papers, the use, misuse, or non-use of plant allelochemicals by insects is extremely variable and difficult to predict, at many levels of time, space, and biological organization. Although certain patterns that reoccur have been important in the development of ecological theory, the optimization of cost-benefit equations involving two or three trophic levels, each with large numbers of individuals, populations, and species in erratic and complex interactions, produces unexpected and fascinating scenarios. The development of rapid colorimetric and chromatographic analyses for several types of plant allelochemicals, notably certain groups of alkaloids, cardiac and cyanogenic glycosides, phenolics, terpenes, and glucosinolates, has permitted a detailed investigation of the variation and flow of these substances in natural organisms and ecosystems. The results of these analyses, in our hands mostly for pyrrolizidine alkaloids (PAs), do not suggest a straightforward classical choice by the aposematic insect to simply sequester or synthesize its defences. Rather, they reveal a confusing variety of diffuse and complex patterns that become increasingly closer to chaos as they are multiplied across structures, species, sexes, stages, sites, seasons, and selective regimes. We present a model reflecting results of analyses at this chemoecological interface. Depending upon an initial option, involving the recognition (or not) of a plant allelochemical, the herbivore will face thereafter options to ingest it (or not), and then to tolerate and absorb (or detoxify and excrete), modify (or not), passively, actively or selectively accumulate, turn over (or not), distribute (or concentrate), and use this compound in a variety of growth, defense, or reproductive functions. The herbivore can also quantitatively or qualitatively regulate the intensity or dispersion of its attack on the plant tissues, in order to modify feedback loops of selection on the plant and its chemicals which exist in most of the earlier steps, or those with its predators and parasites that occur in the later ones. Options that lead to mutualism through positive feedback loops will tend to accumulate and become rapidly fixed by natural selection. Additional variations and anomalies such as automimicry, chemical mimicry, sexual dimorphism and communication, selective sequestration and passing-up of allelochemicals, special glands and structures, and synergism effects, are among the secondary complications of this model that have occupied much thought, time, experimental labor, and polemical space in chemical ecology journals and meetings. Examination of the tendencies and results at various points in the model can be used to explain these features and to make further predictions, plan experiments, and devise activity-based bioassays and new chemical analyses. These may lead some day to new and more robust visions of the major patterns of chemical transfer at this widespread and important natural interface.     

多氯联苯复合污染土壤的微生物群落结构多样性变化

土壤微生物群落结构多样性是指示土壤生态系统稳定性及其功能的重要传感器。采用磷脂脂肪酸(Phospholipid fatty acids,PLFAs)方法,对长江三角洲地区某POPs高风险区PCBs长期复合污染土壤的微生物群落结构多样性进行了初步研究。结果表明,PCBs重度污染土壤中格兰氏阴性菌(16:1w9、cy17:0等)和厌氧微生物(18:1w7)的PLFAs组分含量较多,而格兰氏阳性菌(如i15:0、i17:0等)、放线菌(16:0(10Me))及真菌(18:2ω6,9)和好氧性微生物的PLFAs含量较低,表明PCBs污染土壤中微生物群落结构与组成发生了明显变化。这一结果为PCBs降解微生物资源的定向筛选提供了科学依据。     

模拟淹水条件下紫色土镉的释放特征及影响因素

研究了在模拟淹水条件下紫色土镉的释放迁移特征及影响因素 .结果表明 ,土壤初始镉污染水平、水体初始酸度和有机酸组成显著影响土壤镉向水体的迁移释放 .土壤初始镉浓度每增加 1mg·kg-1,淹水平衡后水体中镉的浓度增加 0 0 0 6—0 0 0 7mg·L-1.当水体初始pH <6时 ,镉的释放量随pH的降低呈线性增加 ,每降低一个pH单位 ,水中镉浓度平均将增加 0 0 6mg·L-1.水体中多种有机物共存时对土壤重金属的释放存在复杂的交互作用 .草酸、柠檬酸、EDTA以及草酸、柠檬酸、富里酸、EDTA共存时显著促进土壤镉的释放 ;而草酸、柠檬酸、富里酸共存时 ,反而抑制了土壤镉的释放 .讨论了淹水过程中镉的释放与体系pH、Eh 变化之间的关系 .     

Influence of Agricultural Antibiotics and 17β-Estradiol on the Microbial Community of Soil

Agricultural pharmaceuticals are a major environmental concern because of their hazardous effects on human and wildlife. This study analyzed phospholipid ester-linked fatty acids (PLFAs) and quinones to investigate the effects of a steroid (17β-estradiol) and agricultural antibiotics (chlortetracycline and tylosin) on soil microbes in the laboratory. Two different types of soil were used: Sequatchie loam (0.8% organic matter) and LaDelle silt loam (9.2% organic matter). The soils were spiked with 17β-estradiol and antibiotics, alone or in combination. In Sequatchie loam, 17β-estradiol significantly increased the microbial biomass, especially the biomarkers for beta proteobacteria (16:1ω7c, 18:1ω7c, Cy17:0, and UQ-8). The coexistence of antibiotics decreased the stimulatory effect of 17β-estradiol on the microbial community. In LaDelle silt loam, there were no significant differences in total microbial biomass and their microbial community structure among the treatments. Overall, 17β-estradiol changed the microbial community of soil and the presence of antibiotics nullified the effect of 17β-estradiol. However, the effects of 17β-estradiol and antibiotics on soil microbes were sensitive to the soil properties, as seen in the LaDelle silt loam.