Measurements of the streaming potential of clay soils from tropical and subtropical regions using self-made apparatus

The streaming potential has been wildly used in charged parallel plates, capillaries, and porous media. However, there have been few studies involving the ζ potential of clay soils based on streaming potential measurements. A laboratory apparatus was developed in this study to measure the streaming potential (ΔE) of bulk clay soils’ coupling coefficient (C) and cell resistance (R) of saturated granular soil samples. Excellent linearity of ΔE versus liquid pressure (ΔP) ensured the validity of measurements. The obtained parameters of C and R can be used to calculate the ζ potential of bulk soils. The results indicated that the ζ potentials measured by streaming potential method were significantly correlated with the ζ potentials of soil colloids determined by electrophoresis (r ²?=?0.960**). Therefore, the streaming potential method can be used to study the ζ potentials of bulk clay soils. The absolute values of the ζ potentials of four soils followed the order: Ultisol from Jiangxi?>?Ultisol from Anhui?>?Oxisol from Guangdong?>?Oxisol from Hainan, and this was consistent with the cation exchange capacities of these soils. The type and concentration of electrolytes affected soil ζ potentials. The ζ potential became less negative with increased electrolyte concentration. The ζ potentials were more negative in monovalent than in divalent cationic electrolyte solutions because more divalent cations were distributed in the shear plane of the diffuse layer as counter-cations on the soil surfaces than monovalent cations at the same electrolyte concentration.     

Degradation of aqueous Rhodamine B by plasma generated along the water surface and its enhancement using nanocrystalline Fe-, Mn-, and Ce-doped TiO2 films

The degradation of aqueous Rhodamine B (RhB) was examined using a dual-channel spark switch module designed to regulate the steepness of pulsed high voltage with microsecond rise time. Depending on the energy per pulse, a spark along the water surface (SPWS) or streamer along the water surface (STWS) was formed. STWS was found to have a better degradation effect and energy efficiency toward RhB than SPWS at the same power; however, addition of H₂O₂ amounts resulted in increased degradation, the effect being more pronounced using SPWS. The initial concentration of RhB also appeared to influence the rate constant of the degradation reaction. Furthermore, TiO₂ films doped with Fe, Mn, and Ce were found to enhance the degradation performance of plasma. A possible reaction mechanism of plasma formation along the water surface was concluded by determination of the main inorganic products in the liquid and gas phases.     

Reduction of Fusarium rot and maintenance of fruit quality in melon using eco-friendly hot water treatment

Significant losses in harvested fruit can be directly attributable to decay fungi and quality deterioration. Hot water treatment (HWT) has been demonstrated to be an effective and economic environment-friendly approach for managing postharvest decay and maintaining fruit quality. In this study, the effects of HWT (45 °C for 10, 15, 20, and 25 min) on in vitro growth of Fusarium oxysporum, in vivo Fusarium rot, and natural decay of melon were investigated. HWT inhibited spore germination and germ tube elongation of F. oxysporum. Protein impairment and ATP consumption triggered by HWT contributed to the inhibitory effect. Results of in vivo studies showed that HWT effectively controlled Fusarium rot and natural decay of melon. Correspondingly, HWT induced a significant increase in content of total phenolic compounds and lignin of melon. These findings indicate that the effects of HWT on Fusarium rot may be associated with the direct fungal inhibition and the elicitation of defense responses in fruit. Importantly, HWT used in this study had beneficial effects on fruit quality as well. HWT may represent an effective non-chemical approach for management of postharvest Fusarium rot.     

Responses of free amino acids in rice seedlings during cyanide metabolism

Responses of free amino acids to botanical assimilation of free cyanide were investigated. Young rice seedlings (Oryza sativa L. cv. XZX 45) were grown in nutrient solution amended with free cyanide (KCN). Cyanide was analyzed in solution as well as in plant materials to estimate the phyto-assimilation potential. Free amino acids in different parts of plants were also measured to determine metabolic responses to KCN exposure. Phyto-assimilation of KCN was obvious, and the rates were positively correlated to the concentration supplied. Although changes in total amino acid content in plant materials were negligible during KCN metabolism (p?>?0.05), responses of different amino acids to KCN treatments were quite different. All treatments with KCN increased the content of proline (Pro) and isoleucine (Ile) in roots significantly compared with control (p?<?0.05), while changes of aspartic acid, lysine, and histidine in roots were more evident at higher KCN treatments (p?<?0.05). Results indicate that the content of Pro, Ile, and tyrosine showed pronounced increase in shoots of rice seedlings exposed to KCN at 1.44 mg CN/L or higher (p?<?0.05). Other amino acids slightly changed in all plant materials exposed to KCN (p?>?0.05). Results indicate that specific amino acids in rice seedlings showed positive response to non-toxic concentrations of exogenous KCN. These findings could provide additional insights into the inducible mechanisms underlying the involvement of amino acids in KCN metabolism.     

电渗透脱水污泥干燥特性曲线及干燥模型

通过电渗透脱水技术及自然风干技术两种预处理方式降低污泥含水率，当污泥初始含水率相近时，研究经两种方式处理后污泥的干燥特性曲线，并对电渗透脱水污泥干燥特性曲线的优势情况进行探讨。在40—120℃的低温条件下，研究电渗透脱水污泥（泥饼厚度为3．5mm）的干燥特性曲线并分析其干燥特性。通过所得电渗透脱水污泥的干燥特性曲线，引人薄层污泥干燥模型进行数值分析。结果表明，在实验条件下，电渗透脱水污泥的干燥速率要优于自然风干污泥的干燥速率。随着温度的升高，电渗透脱水污泥的干燥速率随之升高，干燥到所需含水率的时间则随之减少。Logarithmic模型比其他模型更适合描述薄层电渗透脱水污泥在低温条件下的干燥特性。     

3种运行模式下CAST工艺脱氮性能

以模拟城市污水为处理对象，采用循环式活性污泥法（CAST）反应器，对3种运行模式（M1：常规模式，M2：缺氧好氧模式、M3：缺氧好氧交替模式）下系统的脱氮性能进行了研究，比较了各模式下CAST反应器的氨氮和总氮的去除效率，并对各模式下典型周期内氮基质浓度变化进行了考察，以确定系统的脱氮模式。结果表明，在氨氮去除不成为限制条件（去除率〉90％）的条件下，3种运行模式下系统总氮的平均去除率分别为67．3％、70．6％和82．4％，以缺氧好氧交替模式下的最高；M1、M2和M3均可实现亚硝酸型硝化，但随着温度的升高，亚硝酸型硝化逐渐消失。静态实验分析表明，3种模式下系统的氨氧化速率大小次序为：vN：M1〉vN：M2〉vN：M3，反硝化速率大小次序为：vDN,M2〉vDN,M3〉vDN,M1。     

Major ionic compositions of fine particulate matter in an animal feeding operation facility and its vicinity

Animal feeding operations (AFOs) produce particulate matter (PM) and gaseous pollutants. Investigation of the chemical composition of PM_2.5 inside and in the local vicinity of AFOs can help to understand the impact of the AFO emissions on ambient secondary PM formation. This study was conducted on a commercial egg production farm in North Carolina. Samples of PM_2.5 were collected from five stations, with one located in an egg production house and the other four located in the vicinity of the farm along four wind directions. The major ions of NH₄⁺, Na⁺, K⁺, SO₄^2?, Cl^?, and NO₃^? were analyzed using ion chromatography (IC). In the house, the mostly abundant ions were SO₄^2?, Cl^?, and K⁺. At ambient stations, SO₄^2?, and NH₄⁺ were the two most abundant ions. In the house, NH₄⁺, SO₄^2?, and NO₃^? accounted for only 10% of the PM_2.5 mass; at ambient locations, NH₄⁺, SO₄^2?, and NO₃^? accounted for 36–41% of the PM_2.5 mass. In the house, NH₄⁺ had small seasonal variations indicating that gas-phase NH₃ was not the only major force driving its gas–particle partitioning. At the ambient stations, NH₄⁺ had the highest concentrations in summer. In the house, K⁺, Na⁺, and Cl^? were highly correlated with each other. In ambient locations, SO₄^2? and NH₄⁺ had a strong correlation, whereas in the house, SO₄^2? and NH₄⁺ had a very weak correlation. Ambient temperature and solar radiation were positively correlated with NH₄⁺ and SO₄^2?. This study suggests that secondary PM formation inside the animal house was not an important source of PM_2.5. In the vicinity, NH₃ emissions had greater impact on PM_2.5 formation.

ImplicationsThe chemical composition of PM_2.5 inside and in the local vicinity of AFOs showed the impact of the AFO emissions on ambient secondary PM_2.5 formation, and the fate and transport of air pollutants associated with AFOs. The results may help to manage in-house animal facility air quality, and to develop regional air quality control strategies and policies, especially in animal agriculture-concentrated areas.     

突变灰盖鬼伞过氧化物酶降解刚果红的响应面法优化分析简

酶法降解偶氮染料刚果红是一个复杂的过程，受温度、pH、酶量、刚果红浓度和双氧水浓度显著影响。为研究各因素及因素间交互作用对刚果红降解影响，提高刚果红的降解率，分别使用单因素法和响应面分析法对刚果红降解条件进行了优化。单因素实验结果显示灰盖鬼伞过氧化物酶降解刚果红的最适条件为：pH 5.0、32℃、酶量4.98 U、双氧水0.1 mmol/L、刚果红20 mg/L，此时刚果红最高降解率为34.84%。然后选双氧水浓度、刚果红浓度和灰盖鬼伞过氧化物酶量作为3个因素，通过中心组合设计实验，用响应面法对刚果红降解进行优化分析，最后得到一个拟合度良好的二次多项方程模型（R²=0.9900）。方差分析结果显示，刚果红浓度和酶量是影响最显著的因素，双氧水与酶以及染料与酶之间的交互作用极显著。响应面分析优化后的反应体系为：双氧水浓度0.15 mmol/L，刚果红浓度为27.21 mg/L，酶为2.0 7 U，在此条件下，刚果红降解率达58.13%。     

氯化镁复配硫酸铝混凝性能及絮体特性

在研究氢氧化镁混凝特性的基础上,复配氯化镁和硫酸铝作为混凝剂,以高岭土配水水样为研究对象,运用iPDA在线监测技术对混凝过程絮体形成进行监测,探讨了单独使用氯化镁和硫酸铝以及二者复配使用的混凝效果和絮体特性,确定复配使用的各种条件。结果表明,对于浊度20 NTU,pH 11.5的高岭土配水水样,氯化镁、硫酸铝最佳投加量分别为7.2 mg/L(Mg2+计)和3 mg/L(Al3+计);硫酸铝跟氯化镁复配使用时,先投加硫酸铝,间隔30 s后投加氯化镁,混凝效果较好;在镁离子最佳投加量7.2 mg/L时,铝和镁最佳质量比在1∶3~1∶2之间;镁铝复配时其FI值明显大于单独作用时,即絮体尺寸大小:二者复配硫酸铝氯化镁,而且复配条件下Zeta电位值在零电势左右浮动,浮动范围小,更利于聚集沉淀;镁铝复配时发生了协同效应,弥补了单独使用氯化镁混凝过程的不足。     

偶氮类染料脱色率的定量构效关系

偶氮类染料的生产和使用过程中存在着三废多、难脱色和污染严重等问题,该染料是印染工业的主要污染物。选取偶氮类染料的分子结构参数和其光催化氧化脱色率之间建立定量结构活性关系(QSAR),进而得到回归方程,为印染废水处理和染料环境行为评价提供理论预测。结果表明,偶氮类染料的光催化氧化脱色率与其结构之间存在着线性相关性,线性方程为:D=0.647μ+66.277,(D为脱色率、μ为偶极矩)R=0.989方程具有预测能力。