Effect of solution pH on aging dynamics and surface structural evolution of mZVI particles: H<Subscript>2</Subscript> production and spectroscopic/microscopic evidence

A microscale zero-valent iron (mZVI)-based in situ reactive zone is a promising technology for contaminated groundwater remediation. Estimation of mZVI aging behavior after its injection into the subsurface is essential for efficiency and longevity assessments. In this study, batch tests were conducted to investigate the effect of initial pH on mZVI aging dynamics, as well as the formation and evolution of aging products over 112 days. Results indicated that mZVI aging accelerated with decreasing initial pH. Corrosion rates of mZVI particles under pH 6.0 and 7.5 were approximately two orders of magnitude higher than those observed at pH 9.0. The morphological, structural, and compositional evolution of mZVI particles in three systems (pH = 6.0, 7.5, and 9.0) were investigated using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In acidic and neutral solutions, a thick passivation layer with loosely and unevenly distributed aging precipitates was observed, and Fe₃O₄ was the final aging precipitate. Nevertheless, in alkaline solutions, minute aging precipitates were detected on the mZVI surface at 112 day. Characterization results suggested that mZVI was oxidized via the Fe⁰–Fe(OH)₂–Fe₃O₄ route. These findings shed new light on mZVI aging mechanisms, particularly its physicochemical characteristics and the structural evolution of mZVI in field-scale groundwater remediation applications.     

Risk assessment of heavy metals in soil of Tongnan District (Southwest China): evidence from multiple indices with high-spatial-resolution sampling

Assessment of heavy metal (HM) pollution in soil is critical for human health, ecological remediation, and soil conservation. In this study, statistical analyses and geochemical approaches such as enrichment factor (EF), the index of geoaccumulation (Igeo), and potential ecological risk index (RI) were used for characterization and risk assessment of soil HMs through a high-spatial-resolution 385 samples from Tongnan District, an important agricultural practice area in Chongqing Municipality in Southwest China. Igeo and EF indicated that Hg and Cd could be considered as low and moderate polluted, respectively, and others HMs were not a major concern. Comprehensive ecological risk information further demonstrated that the HMs have caused a moderate risk. Principal component analysis (PCA) extracted two principal components (PCs) with eigenvalue >1 explaining about 66.1% of the total variance in the HM data sets, demonstrating major source of anthropogenic activity, phosphate fertilizers, vehicle, and pesticides. These multi-index methods have the capacity of HM assessment in soil, which are useful for soil conservation and ecological remediation.     

Treatment of Sydney N.S. tar pond sludge in a pilot‐scale rotary kiln

Tar pond wastes from Sydney, Nova Scotia, containing 50 ppm or more of polychlorinated biphenyls (PCBs) were treated in a pilot‐scale rotary kiln. In order to use the existing feed system attached to the rotary kiln, the wastes were first oven‐dried. Stack gas sampling was conducted during the test, which included measurement of volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), semi‐volatile organic compounds (SVOCs), HCl, and metals. The purpose of this study was to determine emissions from treatment of the tar pond waste using rotary kiln technology. It was found that the dried sludge could sustain combustion in the kiln without any supporting fuel. The emissions of polychlorinated dibenzodioxins/furans (PCDD/Fs) were higher than the Canadian Council of Ministers of the Environment (CCME) air emissions guidelines, and the reasons for this are discussed. © 2008 Wiley Periodicals, Inc.     

印刷过程VOCs废气收集方式选择与优化

为提高印刷过程中VOCs废气的收集效率和合理控制废气净化系统规模,对废气收集方式进行了选择与优化,采用现场测试和数值模拟相结合的方法,对平版印刷过程中VOCs扩散模式进行分析,采用数值模拟方法对常用的外部接收罩、半密闭罩和密闭罩等3种收集方式的效果进行了估算并与实验数据进行了比较。结果表明：由数值模拟得到的VOCs浓度分布趋势与现场测试结果基本一致;密闭罩和半密闭罩达到90%以上收集效率时的最小控制风量分别为160 m³·h⁻¹和320 m³·h⁻¹;外部接收罩在最大设计风量(1 280 m³·h⁻¹)下,收集效率仅为80%;考虑到印刷过程操作条件的限制,在外部接收罩的基础上,增设垂直挡板和三角形格栅,对其进行结构优化,当控制风量为640 m³·h⁻¹时,外部接收罩收集效率由优化前的70%提高到91%。     

大高差溜槽粉尘颗粒扩散运动规律数值模拟

为解决大型露天矿回填溜槽运输系统产生的粉尘污染问题,运用溜槽物料牵引流、落料诱导气流和剪切气流理论分析了溜槽工艺的粉尘析出机理。研究发现,溜槽运输系统粉尘的析出是诱导空气的尘化作用、剪切压缩尘化作用的结果,粉尘析出的主要影响因素包括物料的基本属性、运行速度及溜槽出口落差。基于气固两相流理论,利用数值模拟方法计算小空间粉尘颗粒的扩散规律和颗粒运动轨迹,结果显示溜槽系统粉尘粒径范围在0~100 μm,物料流速度大于10 m/s时,粉尘大部分被扬起,溜槽出口距离平台距离越大粉尘析出量越大。为制定多尺度、综合的粉尘防治措施提供必要的理论支撑与科学依据。     

水环境中重金属污染研究概述

重金属污染是水环境污染的一个重要方面，而水质模型是重金属污染研究的重点方法之一，作者在对溪落渡水库重金属污染的研究工作过程中，收集和整理了大量有关资料，本文概述了目前常用的重金属迁移转化动力学数学模型及建立该模型时所涉及到的重金属存在形态、污染特征，迁移转化过程等方面的研究成果和存在问题。     

重庆市某小城镇地表水污染控制及可持续发展规划研究

以重庆市渝西地区某小城镇环境规划为例，分析了该镇地表水存在的污染问题，并迎合该镇可持续发展的需要，制定了一系列地表水污染控制规划方案，分析了规划方案的环境效益。     

The valuation of gross ecosystem product in the three provinces in northeast of China

Achieving sustainable development is an issue of global concern. Accounting for the gross ecosystem product (GEP) value can specifically quantify the value of ecosystems for people, which is conducive to the formulation of sustainable management decisions. We have improved the GEP framework accounting method for the first time and evaluated the ecosystem service value of 36 cities in three provinces in the northeast (TPN) of China from 2000 to 2019, which provides decision-making references for the sustainable development of TPN. The main accounting results and policy recommendations are as follows: (1) The ecological value of Northeast China is in an upward stage—GEP has increased from 3.1 trillion yuan in 2000 to 4.5 trillion yuan in 2019, with climate regulation and water conservation functions being the main driving factors for GEP. (2) Based on the dual analysis of GEP and gross domestic product (GDP), there is still high room for improvement in most cities in the TPN region. While ensuring the protection of ecosystem services, cities can convert ecological value into economic value through carbon trading, water rights trading, ecological compensation, and other methods based on ecological characteristics, which is conducive to the sustainable development of GDP and GEP in the TPN region in the future. (3) The cold and hot spot analysis of GEP also provides decision-making basis for the planning of future ecosystem service protection areas in the TPN region.     

河南油田GIS设备漏气故障分析与处理

介绍了河南油田GIS设备漏气故障的处理方法,分析了漏气的原因,提出了相应的防范措施.     

Crystal structure of a new high-performance magnesium slag desulfurizer modified by quenching hydration

Journal of Material Cycles and Waste Management - The original magnesium slag has poor desulfurization activity, so modification treatments are needed to improve its desulfurization activity. In...