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.     

Characterization of the interactions between tetracycline antibiotics and microbial extracellular polymeric substances with spectroscopic approaches

The antibiotics have attracted global attentions for their impact on aquatic ecosystem. The knowledge about the fate of antibiotics encountering extracellular polymeric substances (EPS) is, however, limited. In this study, we investigated the interacting mechanisms of tetracycline (TC) to EPS extracted from aerobic activated sludge. The contributions of the main components of EPS, extracellular proteins, and polysaccharides were evaluated using bovine serum albumin and alginate sodium, respectively. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance indicated that hydroxyl, carboxyl, and amino groups were the domain chemical groups involved in the interaction between TC and EPS, and the binding of TC onto EPS changed the structure of these chemical groups, thus causing shifts in their UV–visible absorption spectra. In addition, we found that extracellular proteins, rather than polysaccharides, were the major active contents involved in the interaction. Three-dimensional excitation–emission matrix fluorescence spectroscopy showed that the fluorophores in EPS were clearly quenched by TC and the static quenching process was observed, implying the complex formation of TC and EPS. Furthermore, thermodynamic analysis indicated that the binding of TC with EPS is spontaneous and dominated by electrostatic forces.     

Distribution of nutrients,heavy metals,and PAHs affected by sediment dredging in the Wujin'gang River basin flowing into Meiliang Bay of Lake Taihu

This paper's survey of the pollution of the Wujin'gang River is important because it is one of the main rivers flowing into Meiliang Bay of Lake Taihu in eastern China. Trace metals (TMs) in this paper are described according to their pollution index (P _i). Cluster analysis and correlation analysis are utilized for group sites and to assess co-contamination. Toxicity effect analysis was conducted using individual sediment quality guideline quotients (SQGQs) and mean SQGQs. The results showed that sediment from the Wujin'gang River basin was affected by nutrients, heavy metals, and polycyclic aromatic hydrocarbons (PAHs), which are an essential contamination source for both Meiliang Bay and Zhushan Bay of Lake Taihu. The discharge of TMs has significant correlations to total nitrogen (TN) and total phosphorus (TP); however, no significant correlations were observed between the content of PAHs and TMs. Toxicity effect results show that sediment in the Wujin'gang River basin threatens sediment-dwelling organisms. The harmful effect was mainly caused by heavy metals especially Cd, Cr, Ni, and Cu. Sediment dredging is an effective way to control pollution from internal rivers especially for the pollution of TN and heavy metals in the Wujin'gang River basin.     

Toxicity of urban highway runoff in Shanghai to Zebrafish (Danio rerio) embryos and luminous bacteria (Vibrio qinghaiensis.Q67)

Pollution from urban highway runoff has been identified as one of the major causes of the deterioration of receiving water quality. The purpose of this study is to assess the toxicity of urban storm water samples in Shanghai using the zebrafish (Danio rerio) embryo test and the bacterial luminescence (Vibrio qinghaiensis) assay. The toxicity of highway runoff from seventeen storm events was investigated in both grab and composite samples. Zebrafish embryos were exposed to the runoff samples and development parameters including lethality, spontaneous movements in 20 s, heart beat rate, hatching rate, and abnormality of zebrafish embryos were observed after 24, 48, 72, and 96 h of exposure. Inhibition rates of luminescence intensity were also recorded. The results showed that in the zebrafish embryo toxicity tests, both grab and composite samples increased the lethality, reduced the percentage with spontaneous movements and heart beats, inhibited the hatching of embryos, and induced morphological abnormalities. In the Vibrio qinghaiensis toxicity test, all the grab samples inhibited the luminescence, while some of the composite samples promoted it, which indicated that different types of toxicants might have been affecting the species. The multivariate statistics analysis indicated that heavy metal (zinc, manganese, and copper) and PAHs might mainly contribute to the toxicity of runoff samples.     

Enhanced electrokinetic remediation of lead-contaminated soil by complexing agents and approaching anodes

Optimizing process parameters that affect the remediation time and power consumption can improve the treatment efficiency of the electrokinetic remediation as well as determine the cost of a remediation action. Lab-scale electrokinetic remediation of Pb-contaminated soils was investigated for the effect of complexant ethylenediaminetetraacetic acid (EDTA) and acetic acid and approaching anode on the removal efficiency of Pb. When EDTA was added to the catholyte, EDTA dissolved insoluble Pb in soils to form soluble Pb–EDTA complexes, increasing Pb mobility and accordingly removal efficiency. The removal efficiency was enhanced from 47.8 to 61.5 % when the EDTA concentration was increased from 0.1 to 0.2 M, showing that EDTA played an important role in remediation. And the migration rate of Pb was increased to 72.3 % when both EDTA and acetic acid were used in the catholyte. The “approaching anode electrokinetic remediation” process in the presence of both EDTA and acetic acid had a higher Pb-removal efficiency with an average efficiency of 83.8 %. The efficiency of electrokinetic remediation was closely related to Pb speciation. Exchangeable and carbonate-bounded Pb were likely the forms which could be removed. All results indicate that the approaching anode method in the presence of EDTA and acetic acid is an advisable choice for electrokinetic remediation of Pb-contaminated soil.     

臭氧氧化法处理焦化废水生化出水的反应动力学简

对臭氧氧化去除焦化废水生化出水COD的反应动力学及其影响因素进行了实验研究,结果表明,在臭氧投加量为8.50 mg/min,反应温度为20℃和初始pH为10.61条件下,对COD的降解符合表观一级反应动力学模型,其相关系数R²=0.9991,表观反应速率常数k_Abs=1.01×10^-3 s^-1。该条件下,臭氧氧化对COD的降解主要来源于高活性羟基自由基的强氧化作用。在不同的臭氧投加量（4.25~12.75 mg/min）、不同的反应温度（10~40℃）和不同的初始pH（3.76~12.53）下,COD的降解也同样遵循一级反应动力学规律。随着臭氧投加量的增大,COD降解的表观反应速率常数从（0.554×10^-3） s^-1增加到（1.06×10^-3） s^-1;随着反应温度的升高,表观反应速率常数从（0.427×10^-3） s^-1增加到（1.40×10^-3） s^-1,温度越高反应速率提高的幅度却越小;在初始pH3.76~10.61范围内,表观反应速率常数从（0.218×10^-3） s^-1增加到（1.01×10^-3） s^-1,在初始pH为12.53时表观反应速率常数下降到（0.857×10^-3） s^-1。     

共存物质对重金属絮凝剂 MCC 除镉性能的影响简

为进一步拓展天然高分子絮凝剂壳聚糖的应用范围,以壳聚糖、L-半胱氨酸为原料,通过酰胺化反应制备一种具有重金属捕集功能的高分子重金属絮凝剂-2-氨基-3-巯基丙酰壳聚糖（MCC）,研究了水体中常见的阴阳离子、有机配位剂及浊度对MCC除镉性能的影响,探讨了絮体形貌与絮体分形维数及絮凝除镉效果间的关系。结果表明,Na⁺、Cl^-、NO₃^-、F^-、SO₄^2-的存在对MCC除Cd²⁺均有促进作用,Ca²⁺表现为明显的抑制作用;低浓度的EDTA对除镉有促进作用,随着EDTA浓度的增大,逐渐转为抑制作用;低浓度的腐殖酸对MCC去除Cd²⁺有显著的促进作用;在一定范围内,浊度可促进 MCC对Cd²⁺的去除;絮体间空隙越多,絮体分形维数越小,除镉效果越好。     

气升回流一体化工艺处理生活污水简

针对分散型生活污水处理开发了气升回流一体化工艺,以校园生活污水为对象,研究其对生活污水中污染物的去除效果。该系统由好氧区、厌氧区、沉淀区和气升室组成,以曝气的剩余气体的气升作用实现混合液的回流,节省动力消耗。结果表明,本工艺对COD、氨氮及悬浮物（SS）有较好的去除效果,去除率分别达到80%、90%和75%左右,出水COD、NH₄⁺-N及SS平均浓度在40 mg/L、6.5 mg/L和10 mg/L左右。当进水COD在100~1 000 mg/L之间波动时,出水水质稳定。该工艺有较强的抗冲击负荷能力,且可实现剩余污泥的自消解。本工艺具有结构紧凑、占地少,运行费用低,维护简单的特点。     

粉末活性炭对三烯丙基异氰脲酸酯的吸附性能简

用静态吸附法考察粉末活性炭对水中三烯丙基异氰脲酸酯（CAIC）的吸附行为,采用单因素分析法对活性炭吸附化工废水中TAIC的工艺条件进行研究。实验结果表明,在TAIC模拟废水中,其TAIC初始浓度为800 mg/L,pH为7,在温度为298 K、转速为150 r/min的条件下,当活性炭的投加量达到4.4 g/L,吸附反应时间为50 min时,TAIC的去除效率最高为96.17%;对于实际废水,其TAIC初始浓度为1 500 mg/L,溶液pH为3,在温度为298 K、转速为150 r/min的条件下,当活性炭投加量达到10 g/L,吸附反应时间为2 h时,TAIC的去除效率最高为46.8%。这也是由于实际废水组分复杂,其他有机物存在一定的吸附竞争机制。     

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%。