Application of percarbonate and peroxymonocarbonate in decontamination technologies

Sodium percarbonate (SPC) and peroxymonocarbonate (PMC) have been widely used in modified Fenton reactions because of their multiple superior features, such as a wide pH range and environmental friendliness. This broad review is intended to provide the fundamental information, status and progress of SPC and PMC based decontamination technologies according to the peer-reviewed papers in the last two decades. Both SPC and PMC can directly decompose various pollutants. The degradation efficiency will be enhanced and the target contaminants will be expanded after the activation of SPC and PMC. The most commonly used catalysts for SPC activation are iron compounds while cobalt compositions are applied to activate PMC in homogenous and heterogeneous catalytical systems. The generation and participation of hydroxyl, superoxide and/or carbonate radicals are involved in the activated SPC and PMC system. The reductive radicals, such as carbon dioxide and hydroxyethyl radicals, can be generated when formic acid or methanol is added in the Fe(II)/SPC system, which can reduce target contaminants. SPC can also be activated by energy, tetraacetylethylenediamine, ozone and buffered alkaline to generate different reactive radicals for pollutant decomposition. The SPC and activated SPC have been assessed for application in-situ chemical oxidation and sludge dewatering treatment. The challenges and prospects of SPC and PMC based decontamination technologies are also addressed in the last section.     

Pilot study on bromate reduction in ozonation of water with low carbonate alkalinities by carbon dioxide

A pilot study was carried out to explore the application of carbon dioxide for pH depression in a bubble column and its ability to inhibit bromate formation for water with a low alkalinity. Results showed that in the absence of ammonia, CO2 was capable of reducing bromate 38.0%–65.4% with one-unit pH depression. CO2 caused a slightly lower bromate reduction (4.2%) than did H2SO4 when the pH was depressed to 7.4, and a more a pronounced lower reduction (8.8%) when the pH was depressed to 6.9. In the presence of 0.20 mg/L-N ammonia, bromate was largely inhibited with 73.9% reduction. When the pH was depressed to 7.4, CO2 and H2SO4 showed an 11.3% and 23.5% bromate reduction respectively, demonstrating that the joint use of CO2 and ammonia might be a plausible strategy of blocking all three bromate formation pathways. CO2 could be applied through the aeration diffuser together with ozone gas, resulting in a similar bromate reduction compared with the premixing method through Venturi mixer.     

不同流速下零价铁调控污水管道节点硫转化的影响

研究了不同污水流速下,各粒径零价铁(ZVI)对实际污水中硫化物(S^2-)和硫化氢(H₂S)浓度以及pH值的影响,并考察了不同污水流速下各粒径ZVI的损失量和消耗量.结果表明,当污水流速为0.2 m·s^-1和0.6 m·s^-1时,ZVI粒径越小,S^2-和H₂S的去除效果越好,其中R3-ZVI对S^2-和H₂S的控制效果最好,但其损失量和消耗量最高且pH偏高(分别为8.5和8.3),而R2-ZVI对S^2-和H₂S的控制效果与R3-ZVI接近且pH适中(分别为8.1和8.0),当污水流速提高至1.2 m·s^-1时,R2-ZVI对S^2-和H₂S的控制效果最好且pH值适中(7.9),而R3-ZVI的损失量和消耗量因受水流速度影响而显著增加,从而导致其对S^2-和H₂S的控制效...     

中国城市PM2.5空气质量改善分阶段目标研究

中国城市细颗粒物(PM_(2.5))空气质量达标率低,且城市间的污染程度差异较大。为了整体改善PM_(2.5)空气质量,需要针对不同污染程度的城市,制定分阶段改善目标加以考核和管理,研究探讨了城市PM_(2.5)空气质量改善目标体系及不同污染程度城市各阶段目标值。首先运用文献综述法、国内外对比分析法梳理评述了WHO、欧美等发达国家PM_(2.5)的空气质量标准和达标要求,提出中国城市PM_(2.5)空气质量改善的考核目标体系,包括PM_(2.5)浓度目标值或下降率、严重污染天数上限、达标天数下限等指标。通过历史数据分析法研究了2000—2013年美国、日本一些城市和2013—2016年中国74个环保城市PM_(2.5)年均浓度的变化趋势,推论出中国城市PM_(2.5)年均浓度年均下降5%~8%是可能实现的;结合环境保护部及各省市PM_(2.5)污染防治规划,提出PM_(2.5)空气质量改善目标的设定原则和达标天数的回归计算方法;以2014年114个城市PM_(2.5)年均浓度为基数,计算得出不同污染程度城市2020、2025、2030年PM_(2.5)年均浓度年下降率和达标天数的目标值。     

江苏如东沿海经济开发区夏季O3污染特征及来源分析

为探究如东沿海经济开发区夏季大气中的O₃污染成因,基于2022年6月园区大气超级站的监测数据,较为全面地分析了O₃污染来源、水平及二次生成潜势等。结果表明:2022年6月园区O₃超标天数占比为34.5%,共计10 d,污染严重程度为2018—2022年同期最高水平(151 μg/m³);分析4个污染过程发现,高温低湿、静稳天气易诱发O₃污染事件,结合污染天气象条件发现,当温度＞25℃且相对湿度＜ 75%时极易发生O₃污染;污染天VOCs组分贡献率主要受芳香烃、烯烃及烷烃影响,其中邻二甲苯、甲苯、间-对二甲苯是O₃管控的关键活性物种;后向轨迹聚类分析显示,园区O₃污染主要受到上海、江西和苏南本地气团输送的影响,主导轨迹出现概率分别为30%、27%和24%,其余小部分时段可能受到来自中国北部和东部的下沉气流影响。为科学管控园区夏季O₃污染,应加强监测并协同管控本地关键VOCs物种。     

基于AHP-CRITIC综合权重的改进物元可拓模型在地下水水质评价中的应用

权重的确定在地下水水质评价中具有重要作用。利用CRITIC方法对地下水指标进行权重修正,探究该方法对地下水质量评价的适用性。笔者选取代表性指标后,按照一般化学指标、毒理学指标2个层次构建地下水污染评价综合指标体系,建立基于AHP-CRITIC综合权重的改进物元可拓模型对研究区地下水开展质量评价。将开发的评价方法应用于工业园区地下水质量评价发现,该方法能够反映地下水质量状况。结果表明:该评价方法在地下水质量评价过程中,能够兼顾不同指标重要程度差异和水质等级的模糊性,研究区5#点位和10#点位有毒有害重金属超标,应进一步查明原因,提出地下水污染阻断措施。     

Digital economy and urban low-carbon sustainable development: the role of innovation factor mobility in China

Environmental Science and Pollution Research - To address climate change, one of the toughest contemporary environmental issues, growing importance is attached to the role of the digital economy in...     

连云港市冬季霾污染成因分析及应急管控效果评估

针对2022年1月5—14日连云港发生的细颗粒物（PM_2.5）连续污染事件（PM_2.5超标共计5 d），基于常规空气质量参数、气象要素、颗粒物组分参数等数据资料，系统分析了污染期间PM_2.5时空变化特征及污染成因，结合大气化学与天气预测模式（WRF Chem）和敏感性试验方法，定量评估了应急减排措施对连云港各区县PM_2.5浓度的影响。结果表明，5 d超标日中有3 d为轻度污染，2 d为中度污染，全市PM_2.5浓度呈现先上升后下降的趋势。不利的气象条件（静稳、小风、高湿）、本地排放（机动车尾气、工业工艺源）和二次生成共同导致了PM_2.5污染的发生。实施黄色预警管控后，ρ（PM_2.5）平均值下降了4.6μg/m³，降幅为5.2%，其中东海县和灌云县ρ（PM_2.5）的降幅最大，分别为6.1%和8.3%，同时污染天ρ（PM_2.5）峰值平均下降了9.4μg/m³（6.0%）。通过PM_2.5过程分析方法发现，应急减排导致人为排放、化学过程和背景浓度对近地面ρ（PM_2.5）正贡献的减少量要显著大于垂直混合、区域输送和对流过程负贡献的增加量。