The thermal transformation mechanism of chlorinated paraffins: An experimental and density functional theory study

The increasing production and usage of chlorinated paraffins(CPs) correspondently increase the amount of CPs that experience thermal processes. Our previous study revealed that a significant amount of medium-chain chlorinated paraffins(MCCPs), short-chain chlorinated paraffins(SCCPs) as well as aromatic and chlorinated polycyclic aromatic hydrocarbons(Cl-PAHs) were formed synergistically during the thermal decomposition of CP-52(a class of CP products).However, the transformation mechanisms of CP-52 to these compounds are still not very clear.This article presents a mechanistic analysis on the decomposition of CP-52 experimentally and theoretically. It was found that CP-52 initially undergoes dehydrochlorination and carbon chain cleavage and it transformed into chlorinated and unsaturated hydrocarbons. Cyclization and aromatization were the most accessible pathways at low temperatures(200–400°C), both of which produce mostly aromatic hydrocarbons. As the temperature exceeds 400°C, the hydrocarbons could decompose into small molecules, and the subsequent radical-induced reactions become the predominant pathways, leading to the formation of Cl-PAHs. The decomposition of CP-52 was investigated by using density functional theory and calculations demonstrating the feasibility and rationality of PCB and PCN formation from chlorobenzene. The results improve the understanding of the transformation processes from CP-52 to SCCPs and Cl-PAHs as well as provide data for reducing their emissions during thermal-related processes.     

Electrogeneration of H(2) for Pd-catalytic hydrodechlorination of 2,4-dichlorophenol in groundwater

A novel electrolytic groundwater remediation process, which used the H₂ continuously generated at cathode to achieve in situ catalytic hydrodechlorination, was developed for the treatment of 2,4-dichlorophenol (2,4-DCP) in groundwater. Catalytic hydrodechlorination using Pd supported on bamboo charcoal and external H₂ showed that 2,4-DCP was completely dechlorinated to phenol within 30 min at pH ? 5.5. In a divided electrolytic system, the catalytic hydrodechlorination of 2,4-DCP in cathodic compartment by H₂ generated at the cathode under 20 and 50 mA reached 100% at 120 and 60 min, respectively. Two column experiments with influent pHs of 5.5 (unconditioned) and 2 were conducted to evaluate the feasibility of this process. The 2,4-DCP removal efficiencies were about 63% and nearly 100% at influent pHs of 5.5 and 2, respectively. Phenol was solely produced by 2,4-DCP hydrodechlorination, and was subsequently degraded at the anode. A low pH could enhance the hydrodechlorination, but was not necessarily required. This study provides the preliminary results of a novel effective electrolytic process for the remediation of groundwater contaminated by chlorinated aromatics.     

耐低温贫营养好氧反硝化菌群脱氮特性及安全性

针对微污染水体强化原位生物脱氮技术同时面临低温、贫营养及好氧问题,对实验室已分离筛选的贫营养好氧反硝化菌和耐低温好氧反硝化菌进行菌源重组,构建出高效耐低温贫营养好氧脱氮功能菌群T1(Y3+F3+H8)和T2(Y3+F4)。研究不同投菌量条件下菌群的脱氮特性,结果表明,投菌量对T1脱氮效果有一定影响,0.1、0.2和1.0 mg/L投量对NO3--N去除率为71%、91%和100%,总氮去除率为56%、34%和52%;T2菌群,当投量为0.2 mg/L时,对NO3--N、总氮去除率最大可达66%和59.48%。对菌群T1、T2进行生物安全性分析,采用次氯酸钠进行消毒,其生物灭活率均达到99.9%以上。     

絮团粘性分维数的概念及其分析模型

水处理中的絮团具有复杂的形态结构,分维数是描述这种结构的有力工具。通过分析固液体系的粘度与絮团分维数之间的关系,提出了絮团粘性分维数的新概念及粘性分维数测定的数学物理模型,并进行了实验验证。与常用的质量分维数、边界分维数、面积分维数、体积分维数、表面积分维数等相比,絮团的粘性分维数及其测定模型具有易于测量、可同时表征不同类型絮团、可定量分析絮凝产品组成等特点,从而为絮团形态结构的定性及定量研究开辟了新的途径。     

不同养殖模式池塘沉降颗粒营养物质组成特征

2012年4~10月采用自制沉降颗粒收集装置收集主养草鱼和黄颡鱼池塘生态系统中沉降颗粒物,开展了颗粒物质的垂直沉降量以及沉降颗粒中碳氮磷等营养物质的组成及沉降通量的季节变化特征的研究。结果表明:养殖可以显著提高池塘颗粒物质的垂直沉降量,主养草鱼池塘中颗粒物质垂直沉降量显著高于主养黄颡鱼池塘(p0.01),且两种养殖模式池塘颗粒物质沉降量随着养殖时间推进有显著增加的趋势。主养草鱼的池塘中颗粒物质垂直沉降量在100.39~414.66g/(m2·d)之间变化,平均为224.46g/(m2·d),主养黄颡鱼池塘中沉降颗粒物质垂直沉降量在34.14~272.91g/(m2·d)之间变化,平均为155.18g/(m2·d)。两种养殖模式沉降颗粒的碳氮磷成分在养殖周期内的变化规律不明显但具有相似的变化趋势,主养黄颡鱼池塘沉降颗粒中TN、TC、TOC和TON的含量均比同时期主养草鱼高,且均随着养殖时间的推进,沉降颗粒中碳氮磷的总量呈增加趋势。两种养殖模式池塘沉降颗粒中的C/N比值与沉积物中的C/N比值较为接近,表明沉降颗粒与沉积物营养物质来源具有一定的相似性,同时养殖系统内养殖对象与其所处环境的相互依存和相互影响对颗粒物质的产生以及沉降具有重要作用。     

人地协同论：可持续发展模型构建的基础

人地协同论是在陆地系统科学、非线性系统理论基础上建立起来的关于可持续发展的一个数理模型,它以社会与自然的交互作用、交界面性质及其演化规律为研究对象。本文根据系统生态学理论,提出了关于可持续生存的数学定义。     

复合催化氧化技术对油气田压裂返排液的处理研究

酸化压裂作业废水是石油天然气生产过程中的主要污染源,它的污染成份复杂,有害物质浓度高,特别是含有胍胶和表面活性剂等高分子物质,具有高COD、高稳定度、高粘度的特点.本文通过对压裂液的来源、水质特征、治理现状等常用方法的分析,确定了物理化学脱稳,过滤、O3/H2O2复合催化氧化、深度氧化的达标治理工艺路线.经过处理后的压裂液澄清透明,达到国家二级排放标准(GB8978-96).     

基于多因子指数集成的流域面源污染风险研究

为掌握流域面源污染风险的整体趋势,基于风险评价时,单个因子对系统某种风险的贡献率可能大于1且因子对系统风险贡献呈一定结构性的问题,定义了风险标准值的概念和算法,建立了系统风险多因子集成评价方法,并在地理信息系统支持下对泸沽湖流域进行了案例研究.结果表明,泸沽湖流域面源污染流失风险处于较高的水平;系统风险多因子集成评价法在对多个同类系统间进行比较时,具有较大的优势;该方法可以与其他多种方法相结合对系统属性进行全面综合评价.     

苏州市环境空气质量自动监测信息化平台建设思路研究

随着不断增长的环境空气自动监测数据量与滞后的数据管理方式之间的矛盾日益凸显,现有的环境空气自动监测平台已出现了一定程度的滞后,逐渐不能满足基层监测部门、决策机构和社会各界的要求,亟待更新和完善。对现有环境空气自动监测业务平台建设思路加以更新和完善,有助于建设功能相对完善的新型平台,从而为环境管理和社会公众提供更为高效、便捷的数字化服务,并对政府决策和预报预警提供更为及时的技术支撑和保障。     

基于"3S"和GSM技术的近海溢油监测应用系统研究

介绍了Visual Basic6．0将“3S”和GSM有机集成中的关键技术以及系统实现的溢油面积、溢油量的计算,接收定位,溢油定位连续动态显示,信息查询,联机之间、控制中心与应急单位互相预警等功能。该系统不但为溢油应急提供指导,同时也为溢油事故的仲裁和索赔提供科学依据。