A strategy for enhancing anaerobic digestion of waste activated sludge: Driving anodic oxidation by adding nitrate into microbial electrolysis cell

Cathodic reduction of CO₂ and anodic oxidation of organic matters are crucial to methane-producing microbial electrolysis cell (MEC) applied in anaerobic digestion of waste activated sludge. However, cathodic CO₂ reduction is usually restrained by slow metabolism rates of H₂-utilizing methanogens and low electron-capturing capacity of CO₂, which consequently slows down the anodic oxidation that participates to sludge disintegration. Herein, a strategy with adding nitrate as electron acceptor to foster electronic transfer between the anode and cathode was proposed to improve anodic oxidation. Results showed that the average efficiency of anodic oxidation in the nitrate-added MEC increased by 55.9%. Accordingly, volatile suspended solid removal efficiency in the nitrate-added MEC was 21.9% higher than that of control MEC. Although the initial cumulative methane production in the nitrate-added MEC was lower than that of control MEC, the cumulative methane production in 24?days was 8.9% higher. Fourier transform infrared spectroscopy analysis indicated that anodic oxidation of MEC with nitrate accelerated the disintegration of sludge flocs and cell walls. Calculation on current signal further revealed that anodic oxidation driven by cathodic nitrate reduction was the main mechanism responsible for the improved sludge digestion.     

天然/模拟海水中2,4,6-三溴苯酚的光化学行为研究

有机溴代苯酚类污染物在水体中普遍存在,尤其在海洋环境中,除人为污染源外,它还存在广泛的天然来源.以2,4,6-三溴苯酚为模型化合物,以氙灯(λ290 nm)作为模拟太阳光源,研究了海水中溴代苯酚的光化学过程,并系统考察了溴代苯酚初始浓度、Cl~-、Fe(Ⅲ)和pH值等环境因素的影响.实验结果表明,在海水中,2,4,6-三溴苯酚能够快速发生光化学反应,通过产物分析发现其主要产物为通过光致脱溴氯代过程产生的2,4-二溴-6-氯苯酚,并且该产物随2,4,6-三溴苯酚初始浓度、Cl~-浓度、Fe(Ⅲ)浓度的增大及溶液pH值的降低而增加.以明亮发光杆菌为受试生物的毒理学实验表明,2,4,6-三溴苯酚在海水中光化学的前期,系统的毒性效应增强,而毒性的增加可能主要由光致氯代过程导致.     

若尔盖花湖沉积物氨氧化与反硝化功能基因丰度垂向分布特征及其环境响应

若尔盖湿地作为中国最大的泥炭沼泽区,是生物地球化学循环的重要场所.本文以若尔盖湿地的花湖为研究对象,采集0～47 cm的沉积物样品,通过实时荧光定量PCR(qPCR)技术,探究沉积物中氨氧化(amoA)和反硝化(nirS、nirK、nosZ clade I)功能基因丰度的垂向分布特征,及其对环境因子的响应.结果表明:花湖沉积物中古菌amoA基因丰度在垂向分布上呈下降趋势,而nirS基因丰度呈上升趋势;古菌和细菌的amoA基因丰度相近,nirS基因丰度则远高于nirK基因,且氨氧化功能基因丰度整体上比反硝化功能基因低1～2个数量级.总氮(TN)、总磷(TP)、氨态氮(NH~+_4-N)、硝态氮(NO~-_3-N)和亚硝态氮(NO~-_2-N)与古菌amoA基因丰度均呈显著正相关关系(p0.05),而与nirS基因丰度呈显著负相关关系(p0.05).这两种功能基因明显受到花湖沉积物中不同形式氮素浓度的影响与限制.通过研究花湖沉积物氨氧化与反硝化功能基因的垂向分布特征及其对环境的响应,可为深入了解高原湖泊沉积物中的氮循环机理提供参考.     

Characterisation of acute toxicity, genotoxicity and oxidative stress posed by textile effluent on zebrafish

Textile industries are important sources of toxic discharges and contribute enormously to water deterioration, while little attention has been paid to the toxicity of textile effluents in discharge regulation. Bioassays with zebrafish were employed to evaluate the toxicity of wastewater samples collected from different stages at a textile factory and sewage treatment plants (STPs). Physico-chemical parameters, acute toxicity, genotoxicity and oxidative stress biomarkers were analyzed. The wastewater samples from bleaching, rinsing and soaping of the textile factory exhibited high acute toxicity and genotoxicity. The coexisting components of dye compounds, as assistants and oxidants, seemed to cause some effect on the toxic response. After treatment employing the anoxic-oxic (A/O) process in STPs, the color and the chemical oxygen demand (COD) were reduced by 40% and 84%, respectively, falling within the criteria of the Chinese Sewage Discharge Standard. In contrast, increases in acute toxicity and genotoxicity were observed in the anaerobic tank, indicating the formation of toxic intermediates. The genotoxicity of the effluent of the STP was not significantly different from that of the influent, suggesting the wastewater treatment processes were not effective in removing the genotoxicity of the dye wastewater. Results indicated that the effluent contains pro-oxidants since the activities of glutathione (GSH), malondialdehyde (MDA), and total anti-oxidation capacity (T-AOC) were all elevated. In addition, decreases in superoxide dismutase (SOD) and glutathione-S transferase (GST) activities observed can be interpreted as a cytotoxicity sign due to an over-production of reactive oxygen species (ROS). The results of the present study suggest that the STPs were not capable of reducing the toxicity of wastewater sufficiently. Further treatment is needed to remove the potential risks posed by textile effluent to ecosystems and human health, and employing a toxicity index is necessary for discharge regulation.     

炼油厂酸性水汽提装置存在的问题及对策

目前炼油厂酸性水汽提装置存在着诸如汽提净化水中氨含量过高、侧线抽出富氨气中硫化氢含量过高、汽提塔处理能力达不到设计负荷等问题。通过分析，提出了相应的改进对策，如加碱汽提、流程优化等。     

稀有鮈鲫神经发育相关基因的克隆、同源性分析及组织分布

作为重要的本土模式鱼类,稀有鮈鲫神经发育相关的生物学背景几乎空白,导致其在神经毒性评价方面的应用受到限制。本文从稀有鮈鲫脑部克隆得到了神经发育相关的神经生长因子(nerve growth factor;ngf)、脑源性神经营养因子(brain-derived neurotrophic factor;bdnf)、胶质纤维酸性蛋白(glial fibrillary acidic protein;gfap)、髓鞘相关糖蛋白(myelin-associated glycoprotein;mag)、P0蛋白(myelin protein zero;mpz)、微管蛋白α1(α1-tubulin)和Y染色体性别决定基因10(SRY-box containing gene 10;sox10)等基因的片段,并对其进化树及表达谱进行了分析。序列分析表明,bdnf的核苷酸序列与鲫鱼、鲤鱼的同源性最高,均为98%;gfap、ngf、mag和α1-tubulin与斑马鱼的同源性最高,分别为95%、92%、92%和96%;mpz与黑头软口鲦的同源性最高,为94%;sox10与鳙鱼同源性最高,达97%。表达谱分析结果表明,ngf、bdnf、mag、mpz、α1-tubulin和sox10基因均在脑组织中表达量最高,gfap在脊髓中表达量最高,上述结果为这一模式鱼类在神经发育学和神经毒性效应评价方面的应用奠定了基础。     

浑河冲洪积平原土壤及浅层地下水中铅的分布特征

为探讨浑河冲洪积扇土壤及浅层地下水中铅的含量、来源及其分布特征,对研究区50个土壤样品、5个地表水样品和22个浅层地下水样品进行了铅含量分析.结果表明,研究区土壤、地表水和浅层地下水均受到了一定程度的铅污染.表层土壤铅含量较高,在17.72—114.46 mg.kg-1之间,受人为污染影响较大;随土壤深度的增加铅含量呈现逐渐降低的趋势,其迁移规律与铬、砷、铜等重金属密切相关,受土壤性质和有机质含量的影响较大,为研究区土壤和浅层地下水环境风险评价及污染防治提供了科学依据.     

基于聚类分析的海南岛雷电灾害易损度风险区划

利用1998-2009年全国雷电灾害汇编资料、海南岛18个气象台站雷暴资料、海南闪电定位网观测资料和海南省统计年鉴的区域经济、人口数据,选取了表征海南岛雷电灾害致灾因子、孕灾环境和承灾体特征的指标变量。采用R型聚类分析方法对影响易损度的指标进行了筛选和检验。以雷暴日数、50 kA以上平均地闪密度、雷灾频数、人员伤亡频数和区域经济易损模数等5个指标为依据变量,用欧氏距离(Euclidean distance)计算了各样本的相似性测度,应用Q型聚类中的Ward’s法(离差平方和法)进行了层次聚类分析,并用Q型迭代聚类分析法进行了聚类解验证,开展了海南岛雷电灾害风险区划。结果表明:海口属于易损度高风险的第1类地区,该类地区雷电灾害综合易损值高达3.89;文昌、澄迈、临高、定安、屯昌和琼海为易损度次高风险的第2类地区;儋州、琼中、白沙、通什和保亭为中等风险的第3类地区;昌江、东方、乐东、万宁、陵水和三亚为较弱风险的第四类地区。     

Effects of humidity on minimum ignition energy of gaseous epoxypropane/air mixtures

The minimum ignition energy (MIE) is an important property for designing safety standards and understanding the ignition process of combustible mixtures. The minimum ignition energy (MIE) of gaseous epoxypropane/air mixtures is measured using capacitive spark discharge. The effect of humidity on MIE is studied. It is shown that the MIE is not constant when the relative humidity increases from 40% to 88% at room temperature. The relative humidity has no significant influence on the MIE of gaseous epoxypropane/air mixtures at the lower volume fraction of gaseous epoxypropane in air. But, it has significant influence on that at the higher volume fraction. The MIEs of gaseous epoxypropane/air mixtures vary with the fraction of gaseous epoxypropane in air and the humidity. The lowest value of MIE (0.12 mJ) of gaseous epoxypropane/air mixtures is reached at around 10% in the examined ranges of the concentrations for the humidity 40%. The lowest values of MIE (0.1 mJ) of the mixtures are reached also at around 10% in the examined ranges of the concentrations for the humidity 66% and 88% respectively.     

冷冻胁迫对芦荟叶肉细胞原生质体中Ca2+、Na+分布的影响

低温和冻害是造成巨大农业损失和植物死亡的主要逆境因子。为揭示冷冻胁迫对植物细胞中离子分布的影响,选择芦荟细胞原生质体为受试材料,使用离子选择性微电极检测了经冷冻处理后的芦荟原生质体在低渗液中破裂时产生的Ca~(2+)浓度脉冲信号,并同时检测Na~+浓度脉冲信号作为对比。研究了冷冻温度、解冻时间和ZnO NPs处理等因素对冷冻胁迫下芦荟原生质体中Ca~(2+)分布的影响。结果表明,与未经冷冻处理的原生质体相对比,经过冷冻处理的原生质体破裂后,其Ca~(2+)脉冲信号前沿处发生明显的"凹陷",这说明,原生质体中Ca~(2+)分布出现分层现象,靠近细胞中心浓度较高而细胞膜附近浓度较低。这一分层现象在温度为-7℃时开始出现,原生质体解冻5 h后仍未消失。经过ZnO NPs预处理后再进行冷冻的原生质体,其Ca~(2+)脉冲凹陷深度明显减小。而当用ZnO NPs处理解冻后的原生质体时,其Ca~(2+)分层现象消失。冷冻胁迫下芦荟原生质体内Ca~(2+)分布发生显著变化,表明原生质体内Ca~(2+)分布变化与其抗寒反应存在一定关系。与Ca~(2+)相反,Na~+的分布几乎不受冷冻因素的影响。ZnO NPs处理对冷冻芦荟原生质体中Ca~(2+)浓度分布分层有明显的缓解作用,表明一定浓度范围的ZnO NPs在缓解冷冻造成的Ca~(2+)流动性下降,维持细胞Ca~(2+)分布的调控能力方面,具有一定的积极影响。