The effect of alkyl chain length on the degradation of alkylimidazolium- and pyridinium-type ionic liquids in a Fenton-like system

Background, aim, and scope  Ionic liquids are regarded as essentially “green” chemicals because of their insignificant vapor pressure and, hence, are a good alternative to the emissions of toxic conventional volatile solvents. Not only because of their attractive industrial applications, but also due to their very high stability, ionic liquids could soon become persistent contaminants of technological wastewaters and, moreover, break through into natural waters following classical treatment systems. The removal of harmful organic pollutants has forced the development of new methodologies known as advanced oxidation processes (AOPs). Among them, the Fenton and Fenton-like reactions are usually modified by the use of a higher hydrogen peroxide concentration and through different catalysts. The aim of this study was to assess the effect of hydrogen peroxide concentration on degradation rates in a Fenton-like system of alkylimidazolium ionic liquids with alkyl chains of varying length and 3-methyl-N-butylpyridinium chloride. Materials and methods  The ionic liquids were oxidized in dilute aqueous solution in the presence of two different concentrations of hydrogen peroxide. All reactions were performed in the dark to prevent photoreduction of Fe(III). The concentrations of ionic liquids during the process were monitored with high-performance liquid chromatography. Preliminary degradation pathways were studied with the aid of ¹H NMR. Results  Degradation of ionic liquids in this system was quite effective. Increasing the H₂O₂ concentration from 100 to 400 mM improved ionic liquid degradation from 57–84% to 87–100% after 60 min reaction time. Resistance to degradation was weaker, the shorter the alkyl chain. Discussion  The compound omimCl was more resistant to oxidation then other compounds, which suggests that the oxidation rates of imidazolium ionic liquids by OH· are structure-dependent and are correlated with the n-alkyl chain length substituted at the N-1-position. The level of degradation was dependent on the type of head group. Replacing the imidazolium head group with pyridinium increased resistance to degradation. Nonetheless, lengthening the alkyl chain from four to eight carbons lowered the rate of ionic liquid degradation to a greater extent than changing the head group from imidazolium to pyridinium. 1H-NMR spectra show, in the first stage of degradation, that it is likely that radical attack is nonspecific, with any one of the carbon atoms in the ring and the n-alkyl chain being susceptible to attack. Conclusions  The proposed method has proven to be an efficient and reliable method for the degradation of imidazolium ionic liquids by a Fenton-like reagent deteriorated with lengthening n-alkyl substituents and by replacing the imidazolium head group with pyridinium. The enhanced resistance of 1-butyl-3-methylpyridinium chloride when the resistance of imidazolium ionic liquids decreases with increasing H₂O₂ concentration is probably indicative of a change in the degradation mechanism in a vigorous Fenton-like system. H-NMR spectra showed, in the first stage of degradation, that radical attack is nonspecific, with any one of the carbon atoms in the ring and the n-alkyl chain being susceptible to attack. Recommendations and perspectives  Since ionic liquids are now one of the most promising alternative chemicals of the future, the degradation and waste management studies should be integrated into a general development research of these chemicals. In the case of imidazolium and pyridinium ionic liquids that are known to be resistant to bio- or thermal degradation, studies in the field of AOPs should assist the future structural design as well as tailor the technological process of these chemicals     

采油废水中多环芳烃的生态风险评价

先利用C-18固相萃取小柱富集大港油田港东联合处理站污水处理站的采油废水中16种多环芳烃(PAHs,即萘、苊烯、苊、芴、菲、蒽、荧蒽、芘、、苯并[a]蒽、苯并[b]荧蒽、苯并[k]荧蒽、苯并[a]芘、茚并[1,2,3-cd]芘、二苯并[a,h]蒽和苯并[g,h,i]苝),再用气相色谱/质谱(GC/MS)分析测定其浓度,以评价PAHs的去除率和生态风险。结果表明:(1)采油废水经处理后,COD、石油类去除率分别达到82.27%、91.06%;外排水COD、石油类达到《污水综合排放标准》(GB 8978—1996)一级标准要求,优于中国采油废水处理的一般水平。(2)采油废水主要以2、3环的PAHs为主,约占总量的93%以上。(3)苯并[a]芘超过《地表水环境质量标准》(GB 3838—2002)中限值。(4)处理前的采油废水中蒽、菲和苯并[a]芘具有一定的生态风险;处理后的外排水中萘、蒽、菲、荧蒽、苯并[a]芘的暴露浓度(PEC)/预测无效应浓度(PNEC)均小于1,目前尚未对环境造成威胁。但是8种PAHs(苊烯和苯并类PAHs除外)总和表现出较大的毒性,需要引起重视。     

Assessment of DDT and mercury levels in fish and sediments in the Iriri River,Brazil: Distribution and ecological risk

Abstract

In order to assess the risk of exposure of human populations to dichlorodiphenyltrichloroethane (DDT) and mercury, muscles of five fish species were analysed, along with the surface sediment of 14 Iriri River sampling sites. The fish specimens were sacrificed by the spinal section, prior to sex identification, body weight determination and total length. Considering the fish specimens studied, 11% of them showed concentrations of mercury higher than the maximum established by the World Health Organization for safe human consumption. A positive correlation between fish body weight and mercury concentration was observed, besides a positive correlation between the fish size and Hg concentration. Significant differences (P?<?0.05) were found between mean concentrations of DDT and metabolites among species of fish studied. In the Plagioscion squamossissimus species, the highest concentration of total DDT (151.4?ng/g) was found, while in Eugerres Brasilianus species, the lowest. However, the DDT levels in fish muscle of studied species are below the maximum set by FAO-Alimentarius CODEX. In the sediments, total DDT ranged from 11.58?ng/g to 48.4?ng/g, which is associated with the historical DDT use in the Amazon. According to sediment quality guidelines, these levels have a moderate toxic effect in almost all of the studied region.     

Estimation of thyroid doses and health risks resulting from the intake of radioactive iodine in foods and drinking water by the citizens of Tokyo after the Fukushima nuclear accident

The release of radioactive materials from the Fukushima nuclear power plant after the Great East Japan Earthquake on 11 March 2011 poses health risks. In this study, the intake of iodine 131 (I-131) in drinking water and foods (milk, dairy products, and vegetables) by citizens of Tokyo was estimated. The effects of countermeasures (restrictions on the distribution of foods and the distribution of bottled water for infants) on reducing intake were also evaluated. The average thyroid equivalent doses without countermeasures from 21 March 2011 were 0.42 mSv in adults, 1.49 mSv in children, and 2.08 mSv in infants. Those with countermeasures were 0.28, 0.97, and 1.14 mSv respectively, reductions of 33%, 35%, and 45%. Drinking water contributed more to intake by adults and children than foods. The intake of I-131 within the first 2 weeks was more than 80% of the estimated intake, owing to its short half-life, indicating that rapid countermeasures are important in reducing intake. The average risks of cancer incidence and mortality due to I-131 for infants were estimated to be 3 × 10⁻⁵ and 0.2 × 10⁻⁵, respectively, lower than the annual risks of traffic accidents, naturally occurring radioactive material (potassium 40), and environmental pollutants such as diesel exhaust particles.     

Challenges in assessing the toxic effects of polycyclic aromatic hydrocarbons to marine organisms: a case study on the acute toxicity of pyrene to the European seabass (Dicentrarchus labrax L.)

The acute toxicity (96 h) of pyrene (PY) to European seabass (Dicentrachus labrax) juveniles assessed in a semi-static bioassay (SSB) with medium renewal at each 12 h, and in a static bioassay (SB) without medium renewal was compared in laboratorial conditions (water PY concentrations: 0.07-10 mg L⁻¹). Main findings in the SSB that assessed mainly the toxicity of PY and its metabolites were: increased levels of bile PY metabolites in good agreement with the profile of lipid peroxidation levels (LPO) in exposed fish relating PY exposure and oxidative damage; increased levels of PY-type compounds in the brain indicating their ability to cross the blood-brain barrier; increased levels of these substances in liver and muscle which are edible tissues for humans thus raising concern on potential adverse effects on consumers of fish from PY contaminated areas; a significant inhibition of glutathione S-transferase activity suggesting its involvement in PY detoxication as toxicant scavenger; finally, an almost complete impairment of the swimming velocity at all the PY concentrations linking sub-individual to higher population level effects. In the SB, where the overall toxicity of PY, its metabolites and environmental degradation products was evaluated, 19% and 79% of PY decay in test media was found at 12 and 96 h, respectively. In general, the effects were similar to those of SSB but with significant effects being induced at higher PY concentrations indicating that the parental compound is more toxic than its environmental degradation products. The other main differences relatively to the SSB were: increased levels of PY-type substances in the liver suggesting more accumulation in this organ. Therefore, these findings highlight the need of carefully considering experimental design options when assessing the toxicity of readily degradable substances to marine fish, and stress the importance of taking into consideration the toxicity of environmental degradation products in addition to toxic effects of the parental substance and its metabolites for marine ecological risk assessment.     

西安市大气中多环芳烃的季节变化及健康风险评价

对西安市2009年6月-2010年5月空气中的总悬浮颗粒（TSP）和气态样品进行了连续采样,利用GC—MS对16种PAHs进行分析。∑PAHs浓度（气相＋颗粒相）范围为39．93～1032．46ng／m^3,平均值为197．34ng／m^3;其中,冬季大气中∑PAHs浓度最大,相对浓度的范围为31．21％～72．98％,而夏季的浓度最小;检测出16种2～6环的PAHs,其中以3—4环为主。利用特征分子比值法和因子分析进行源解析,发现研究区PAHs的主要来源为燃煤和机动车尾气排放。通过苯并（a）芘（BaP）等效毒性（BEQ）和苯并（a）芘等效致癌浓度（BaPE）进行健康风险评价,结果显示,西安大气中PAHs的毒性具有明显的季节差异,特别是秋季和冬季大气中PAHs对人类的健康存在较大的潜在威胁。     

基于层次分析和模糊评价的民航客机雷击风险管理

雷击作为严重威胁飞行安全的一个重要危险源,对其采取科学的手段进行评估,进而采取措施进行缓解,对提高民航的安全水平有着重要的意义。首先介绍了雷暴现象及其危害,并介绍了风险管理的基本概念。然后探讨了层次分析法和模糊综合评价方法在雷击风险管理中的应用。按照层次分析法和模糊评价法的基本过程对调查所得的数据进行了处理,得到了雷击事件的风险值,并给出了风险缓解措施。文章给出的方法对航空公司运行中的其它危险源同样有借鉴意义。     

变权综合法在航空公司风险评价中的应用研究

针对民航风险评价中大多数综合评价方法采取常权综合法,当评价指标体系中某些指标出现严重缺陷时,导致最终综合评价值与实际情况不符的现象,将变权综合法应用到民航风险评价中。给出变权综合法风险评价的基本步骤,以航空公司风险评价为例,建立评价指标体系,运用模糊数学知识对底层指标进行赋值,并对其进行标准量化,其次根据变权综合评价法的基本原理及民航行业高风险的特点,选择适合的状态变权公式,计算评价指标体系的状态变权及变权,最后由变权综合法的综合评价公式,计算出系统的风险评价值。通过与常权综合法的计算结果相比较,变权综合法能较好解决民航风险评价中常权综合法存在的问题,同时计算结果也验证了变权综合法的优越性、有效性和实用性。     

MTBE装置潜在危险性分析及物料泄漏扩散后果模拟研究

MTBE装置处理的物料（混合C4、甲醇）具有易燃易爆性,若发生物料泄漏,将导致装置发生火灾爆炸。为了确保装置安全平稳、长周期运行,基于MTBE装置工艺技术特点,全面系统分析了装置的潜在危险性,总结出导致装置发生火灾爆炸事故的主要因素-物料泄漏;在此基础上,采用挪威DNV公司的SAFETI定量风险评价软件,建立混合C4、甲醇泄漏扩散模型,对物料泄漏导致的主要事故类型（喷射火、池火等）进行模拟,得出泄漏扩散引发火灾爆炸事故的危害范围。结果表明：该模拟研究能够反映出泄漏扩散过程和破坏范围,取得了较真实的事故影响范围曲线图,可以为设计人员更加详细了解MTBE装置发生事故的危害性及企业加强重点部位监控、制定防范措施、编制事故应急预案提供重要参考依据。     

基于AHP-Fuzzy的高处坠落危险性评价研究

高处坠落事故在建筑安全生产事故中所占的比率最大。预防和控制高处坠落事故始终是建筑业应解决的重要问题,高处坠落危险性评价是预防与控制高处坠落事故的重要手段。以高处坠落风险为研究对象,通过对高处作业＂人—机—环境—管理＂复杂系统进行分析,建立生产人员素质因素、生产设备因素、环境条件因素、安全管理因素等4个大类和23个小类的危险性评价指标体系。在层次分析法和模糊综合评价法等研究基础上,构建了高处坠落风险的AHP-Fuzzy评价模型,确定了各层次的权重集。对给出的实例进行评价,评价结果符合实际情况。结果表明,基于AHP-Fuzzy的高处坠落危险性评价方法是可靠与实用的,并对高处坠落危险性的评判有指导意义。