C/N对污泥厌氧发酵产酸类型及代谢途径的影响

研究了污泥的初始C/N对污泥发酵产酸类型的影响及产酸代谢途径.初始C/N在12时,形成的是乙酸型发酵类型;当初始C/N在56左右,可实现丙酸型发酵类型;而当C/N处于156时,则形成丁酸型发酵.不同发酵产酸类型的形成是由优势产酸菌群的改变导致的.末端限制性片段长度多态性分析(T-RFLP)微生物种群的结果表明,构成乙酸型发酵类型的主要优势菌群为消化链球菌属;而丙酸型发酵类型中的优势菌群则为丙酸杆菌属;梭菌属则是丁酸型发酵类型中的优势产酸功能菌.有机酸代谢途径中关键酶活性检测结果表明,在低C/N条件下,乙酸的累积主要是通过氨基酸之间的Stickland反应形成,而随着C/N值的增大,导致丙酸和丁酸累积的主要代谢途径转变为糖酵解的丙酮酸途径.     

Organic matter and amino acid concentrations in surface sediments of Vembanad Lake – a tropical estuary, west coast of India

The surface sediments of Vembanad Lake, a tropical estuary on the west coast of India, were analyzed for carbon (TC, TOC, TIC), nitrogen (TN), amino acids and two amino sugars. C/N ratios for the surface sediments vary from 1.0–21.8, indicating terrestrial sources of organic matter. Various biogeochemical indicators based on amino acids such as Asp/β-ala and Glu/γ-aba ratios revealed that the organic matter in the 5- to 10-cm surface sediments was fresh and had not undergone extensive degradation. However, the Gluam/Galam ratio for surface sediments of Vembanad Lake varies from 0.4–2.1, indicating the dominance of bacterial biomass in the sediments. Organic matter in the sediments was found to be highly reactive, with a reactivity index ranging from 2.4–7.4, suggesting rapid remineralization. Electronic Publication     

Road to full bioconversion of biowaste to biochemicals centering on chain elongation: A mini review

Production of biochemicals from waste streams has been attracting increasing worldwide interest to achieve climate protection goals. Chain elongation(CE) for production of mediumchain carboxylic acids(MCCAs, especially caproate, enanthate and caprylate) from diverse biowaste has emerged as a potential economic and environmental technology for a sustainable society. The present mini review summarizes the research utilizing various synthetic or real waste-derived substrates available for MCCA production. Additionally, the microbial characteristics of the CE process are surveyed and discussed. Considering that a large proportion of recalcitrantly biodegradable biowaste and residues cannot be further utilized by CE systems and remain to be treated and disposed, we propose here a loop concept of bioconversion of biowaste to MCCAs making full use of the biowaste with zero emission. This could make possible an alternative technology for synthesis of value-added products from a wide range of biowaste, or even non-biodegradable waste(such as, plastics and rubbers). Meanwhile, the remaining scientific questions, unsolved problems, application potential and possible developments for this technology are discussed.     

UPLC法同时快速测定湿地土壤中的五种低分子量有机酸

研究了超高效液相色谱（UPLC）法同时测定湿地土壤中柠檬酸、草酸、苹果酸、酒石酸和丁二酸等5种有机酸的方法,并测定了武昌湖、巢湖和鄱阳湖湿地土壤样品中的有机酸组成含量,为揭示有机酸在土壤-植物-根际环境中的转运、分配和分泌提供理论依据。结果表明：利用UPLC法可以快速地分离5种有机酸,比HPLC分离时间缩短1倍左右;各有机酸的加标回收率为99.17%～103.55%,相对标准偏差为0.48%～1.92%,检测限为0.05～0.18 mg/kg,该方法线性关系优良（R²>0.997）;除了鄱阳湖湿地土壤样品的酒石酸未能检测出,其他湿地土壤样品中的5种有机酸都能检测出;不同湿地土壤样品的优势有机酸种类不同,武昌湖湿地土壤中的柠檬酸和苹果酸对有机酸总量贡献较大,巢湖湿地土壤中的柠檬酸对有机酸总量的贡献最大,鄱阳湖湿地土壤中丁二酸占有机酸总量的比例小于10%;湿地土壤有机酸含量多集中在土壤深度为30～50 cm处,这与该区域植物根系分布及微生物活性较高有关。     

基于稳定碳同位素的济南市二元羧酸类SOA的污染特征与形成机制

为研究济南市冬季PM_2.5中二元羧酸类二次有机气溶胶（SOA）的来源、液相形成机制及影响因素,于2016年1-2月昼夜共采集46个PM_2.5样品,并对二元羧酸类SOA （包括二元羧酸、酮羧酸与α-二羰基化合物）与左旋葡聚糖的昼夜变化特征进行分析.研究结果表明,二元羧酸、α-二羰基化合物与左旋葡聚糖均呈昼低夜高的变化特征,而酮羧酸的昼夜变化特征与之相反.二元羧酸类SOA的分子组成特征以草酸（C₂）的浓度最高,其次是丁二酸（C₄）和丙二酸（C₃）,与受生物质燃烧较显著的二元羧酸类SOA的分子组成是相同的.C₂/总二元羧酸的浓度（TDACs）、甲基乙二醛（mGly）/乙二醛（Gly）、C₂/SO₄^2-比值的昼夜变化特征与稳定碳同位素（δ¹³C）的组成特征均表明济南市冬季夜晚气溶胶的氧化程度比白天深.C₂及其前体物（Gly、mGly）与SO₄^2-、相对湿度（RH）、液相水含量（LWC）与气溶胶的实际酸度（pH_is）的相关性均较强,表明C₂及其前体物是在液相中经酸催化氧化反应产生的.夜晚二元羧酸类化合物的δ¹³C值高于白天,且随着含碳量的升高二元羧酸的δ¹³C值随之降低.C₂的δ¹³C值随气溶胶的老化而偏正,这是由于同位素动力学效应（KIEs）导致的.     

腐殖酸铝盐絮凝体的动态特性

通过显微摄影分析研究了腐殖酸铝盐絮凝体成长的动态过程以及在混凝过程中絮凝体构造(分形维数)的变化规律.结果表明,在腐殖酸混凝过程中,随搅拌历时延长,絮凝体粒径不断成长变大,最终达到平衡状态.随着絮凝体的成长,其构造呈现由密实逐渐向疏松过渡的过程,空隙率变大,二维分形维数由初期的1.8左右下降到1.4左右.絮凝体分形维数D_f和粒径d_f之间具有D_f=Ad_f^-     

Kinetic analysis of waste activated sludge hydrolysis and short-chain fatty acids production at pH 10

The accumulation of short-chain fatty acids (SCFAs), a preferred carbon source for enhanced biological phosphorus removal microbes, was significantly improved when waste activated sludge (WAS) was fermented at pH 10. The kinetics of WAS hydrolysis and SCFAs production at pH 10 were investigated. It was observed that during WAS anaerobic fermentation at pH 10 the accumulation of SCFAs was limited by the hydrolysis process, and both the hydrolysis of WAS particulate COD and the accumulation of SCFAs followed first-order kinetics. The hydrolysis and SCFAs accumulation rate constants increased with a increasing of temperature from 10 to 35℃, which could be described by the Arrhenius equation. The kinetic data further indicated that SCFAs production at pH 10 was a biological process. Compared with the experiment of pH uncontrolled (blank test), both the rate constants of WAS hydrolysis and SCFAs accumulation at 20℃ were significantly improved when WAS was fermented at pH 10.     

顶空CO2对有机物厌氧发酵产挥发性脂肪酸的影响

研究了不同顶空CO2浓度对有机物厌氧发酵体系中底物转化速率、挥发性脂肪酸(VFA)产率及微生物相变化的影响.结果表明,顶空低浓度CO2有助于葡萄糖底物转化,在16h转化率达到93%以上,顶空高浓度CO2和对照组在20h时转化率分别为88.3%、87.6%.顶空高浓度CO2有助于乙酸积累,乙酸产率达8.2mmol/gCOD,分别是对照组和低浓度CO2组的1.52倍和1.87倍.顶空CO2浓度与同型产乙酸菌数量正相关,顶空低浓度CO2组fhs基因拷贝数为9.83×106/mL,高浓度CO2组fhs基因拷贝数为5.32×108/mL,对照组fhs基因拷贝数为6.97×107/mL.提高顶空CO2浓度有利于在混和培养环境中富集同型产乙酸菌.     

污水管网中无机氮类营养盐迁变规律

以一套长1 200 m的城市污水模拟管网为对象,采用人工配水方式,研究了管网中含氮化合物的变化情况,分析评价了沿程氮类营养盐的迁变转化特性.结果表明,以氯化铵为氮源基质,管网微生物将其同化合成生命所需的物质以进行细胞增殖.游离氨基酸、结合氨基酸、核酸是代谢产生的主要含氮有机化合物,其中氨基酸占溶解性有机氮(DON)的绝大多数.同时利用三维荧光光谱、尺寸排阻色谱技术对水中有机物的荧光特性及相对分子质量分布的表征结果显示,污水中有机物的特征荧光峰有所增多,主要以类蛋白、类微生物代谢产物为主,且荧光强度随管网沿程逐渐增强;水中的小分子营养盐在微生物的同化作用下转化为复杂的大分子有机物.     

Pollution profiles and physicochemical parameters in old uncontrolled landfills

The long-term effectiveness of the geological barrier beneath municipal-waste landfills is a critical issue for soil and groundwater protection. This study examines natural clayey soils directly in contact with the waste deposited in three landfills over 12 years old in Spain. Several physicochemical and geological parameters were measured as a function of depth. Electrical conductivity (EC), water-soluble organic carbon (WSOC), Cl⁻, NH₄⁺, Na⁺ and exchangeable NH₄⁺ and Na⁺ were used as parameters to measure the penetration of landfill leachate pollution. Mineralogy, specific surface area and cationic-exchange capacities were analyzed to characterize the materials under the landfills. A principal component analysis, combined with a Varimax rotation, was applied to the data to determine patterns of association between samples and variables not evident upon initial inspection. The main factors explaining the variation in the data are related to waste composition and local geology. Although leachates have been in contact with clays for long time periods (13-24 years), WSOC and EC fronts are attenuated at depths of 0.2-1.5 m within the clay layer. Taking into account this depth of the clayey materials, these natural substrata (>45% illite-smectite-type sheet silicates) are suitable for confining leachate pollution and for complying with European legislation. This paper outlines the relevant differences in the clayey materials of the three landfills in which a diffusive flux attenuation capacity (A_c) is defined as a function (1) of the rate of decrease of the parameters per meter of material, (2) of the age and area of the landfill and (3) of the quantity and quality of the wastes.