Colloid‐facilitated transport of metolachlor through intact soil columns

Abstract

This study evaluated the role of water dispersible colloids with diverse physicochemical and mineralogical characteristics in facilitating the transport of metolachlor through macropores of intact soil columns. The soil columns represented upper solum horizons of an Alfisol in the Bluegrass region of Kentucky. Three different colloid suspensions tagged with metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐l‐methylethyl)acetamide] were introduced at a constant flux into undisturbed soil columns. The eluents were collected and analyzed periodically for colloid and metolachlor concentrations. Colloid recovery in the eluents ranged from 54 to 90 %. The presence of colloids enhanced the transport of metolachlor by 22 to 70 % depending on the colloid type and mobility. Colloids with higher pH, organic carbon, cation exchange capacity (CEC), total exchangeable bases (TEB), surface area (SA), and electrophoretic mobility (EM), showed better mobility, greater affinity for interaction with the herbicide and, thus, greater potential to co‐transport metolachlor. In contrast, increased level of kaolinite, Fe, and Al inhibited metolachlor adsorption and transport. In spite of the increased transportability of metolachlor by the presence of soil colloids, the colloid bound herbicide portion accounted for a very small part of the observed increase. This suggests that surface site exclusion mechanisms and preferential sorption induced by the presence of colloids are more important than ion exchange phenomena in promoting herbicide mobility in subsurface environments.     

我国新环境保护法的突破与展望

论述了我国新环境保护法,国家环境保护规划应当坚持保护优先、预防为主、综合治理、突出重点、全面推进的原则等;新修订的《环保法》要求建立资源环境承载能力监测预警机制;推动多元共治的现代环境治理体系是加大经济处罚的力度。设计了罚款的按日连续计罚规则;要求政府主管部门应当公开环境信息,应当制定和完善公众参与的程序,为公众参与环境监督提供便利等。最后进行了展望。     

改性沸石对2,4-二氯苯酚的去除作用

采用溴化十六烷基三甲铵(HDTMAB)制备改性沸石,在与天然沸石对比的基础上,研究了改性沸石在动态条件下去除2,4-DCP的效果。并对影响去除率的主要因素,包括沸石粒径、进水浓度,进水流速,沸石用量,进水pH值等进行研究。结果表明,细粒改性沸石在pH2.5左右时处理低浓度2,4-DCP溶液时,能取得较好的去除效果,流速较低时去除率最高可达80%以上。     

Evaluation of zeolite-sand mixtures as reactive materials protecting groundwater at waste disposal sites

To recognize properties of a mixture of Vistula sand (medium sand acc. to USCS) with Slovak zeolite as reactive materials suitable for permeable reactive barriers proposed for protection of groundwater environment in vicinity of old landfills comprehensive laboratory investigations were performed. The present study investigates the removal of contaminants specific for landfill leachates onto zeolite-sand mixtures containing 20%, 50% and 80% of zeolite (ZS20, ZS50 and ZS80). Taking into account the results of batch tests it was concluded that the Langmuir isotherm best fitted the data. It was observed that the presence of ammonium, calcium and magnesium decreases the removal efficiency of copper by 32%. Column tests of contaminant migration through the attenuation zone of the reactive materials were interpreted using the software package CXTFIT, which solves a one-dimensional advection-dispersion equation. Column test results also indicate the strong influence of the presence of interfering substances on copper immobilisation; dynamic sorption capacities decrees twofold. Throughout the landfill leachate flow through ZS80 sample, a constant reduction of NH+4 (at 100%), K+ (at 93%) and Fe total (at an average of 86%) were observed. There was no reduction in chemical oxygen demand and biochemical oxygen demand.     

电袋复合除尘器大型化的关键技术探讨

通过对电袋复合除尘器大型化几个关键问题的分析,寻找应对的技术措施,并通过试验研究和工程实践的完善,使这些技术在大型化方面取得重大突破,并成功应用于大型燃煤电站的烟气治理。     

制约地质找矿实现重大突破的主要问题分析

地质找矿改革发展大讨论是地质工作准确定位,统一部署,解决体制机制障碍,实现地质找矿重大突破的一项重要工作.笔者从国家地质工作的性质与定位,中国地质调查局和大区中心的定位与职责问题和统筹规划地质工作三方面探讨了制约地质找矿实现突破的主要问题.从找矿思路、找矿方向、找矿工作的部署及资金的投入,地质工作的部署和组织实施以及矿业权的设置和配置等方面,分析了制约地质找矿重大突破的关键因素.并从加强基础地质工作,拓展地质服务领域,做好统一部署整合勘查工作和矿业权配置政策研究方面,提出了初步的建议与思考.     

毒气泄漏事故应急用个体呼吸防护用品防护效果研究

本文对毒气泄漏事故应急过程中公众常用的个体呼吸防护用品的防护效果进行了研究.针对硫化氢气体,利用无机气体防护时间检测系统,测试研究了滤毒盒、简易防护口罩、毛巾等个体防护用品在不同工况下的防护性能,试验结果表明,有毒气体浓度及温湿度两种工况条件均对个体防护用品的防护时间有较大影响,滤毒盒的防护效果远好于简易防护口罩,毛巾的防护效果较差,在此基础上进一步分析了毒气泄漏事故应急过程中个体呼吸防护用品的选择策略.本研究可为建立个体防护对策的选择方法提供基础数据和参考.     

卫生填埋场防渗层工作性能的数值模型研究

粘土衬垫的防渗性能和吸附阻滞性能对卫生填埋场防渗系统工作性能有着重要影响。通过建立一维对流-弥散模型,分析了渗透系数、扩散系数、入渗强度、吸附能力对渗漏量及衬垫击穿时间的影响。考虑实际工程的复杂性,建立能反映土体分层、土体非均质性、地下水运动及宏观弥散等复杂因素影响的污染物运移二维分析模型,并对各参数的敏感性进行分析。计算结果表明,保持填埋场在低渗滤液水位下运行,对提高衬垫的防渗效果及耐久性有重要意义;受材料本身性质、施工质量等因素的影响,粘土衬垫的渗透系数变异性往往较大,渗透系数提高一个数量级时,衬垫击穿时间显著缩短;渗透系数恒定时,衬垫击穿时间与材料阻滞因子成线性变化关系;地下水分布及运动情况对污染物运移及分布有重要影响,地下水位越低,竖向入渗越明显,入渗区下部土体的吸附性能发挥越充分,到达地下水及下部土体的污染物浓度越低。     

钢渣固定床对水中Pb(Ⅱ)和Cd(Ⅱ)的吸附研究

采用钢渣吸附剂分别对Pr(Ⅱ)和Cd(Ⅱ)进行固定床吸附实验,考察了不同运行参数如进水流速、进水初始浓度和吸附柱高度对动态吸附过程的影响,并应用Thomas模型对在不同条件下得到的穿透曲线进行拟合。实验结果表明进水流速、进水初始浓度和吸附柱高度对动态吸附过程存在影响,穿透时间随床层高度的增加而增加,但是随进水流速和进水初始浓度的增加而减少。Thomas方程穿透曲线拟合效果较好,相关系数R2值均在0.9以上,运用该方程可准确预测吸附柱的操作参数。     

活性炭纤维吸附苯系物影响因素的研究

研究了吸附法去除室内苯系物。实验用活性炭纤维(ACF)作为苯系物的吸附剂,苯、甲苯作为苯系物的代表物。研究苯系物的浓度、气流量及填充密度等条件对活性炭纤维吸附性能的影响。实验结果表明:初始浓度大的苯系物穿透时间短;当两组分气体(苯、甲苯)混合吸附时,吸附能力强的甲苯有置换吸附能力弱的苯的现象发生;气流量加大会较快到达穿透点和吸附饱和点,使穿透曲线发生左移,曲线斜率不变;填充密度对穿透时间与饱和时间都有影响,密度大有利于吸附。