The migration and transformation of dissolved organic matter during the freezing processes of water

This study investigated the partitioning behavior of dissolved organic matter (DOM) in liquid and ice phases, as well as the changes in the optical properties and chlorine reactivity of DOM during the freezing processes of water. DOM was rejected from the ice phase and accumulated in the remaining liquid phase during water freezing. Moreover, the decrease in freezing temperature, as well as the increase in dissolved organic carbon (DOC) concentration of feed water, caused an increase in DOM captured in the ice phase. The ultraviolet-absorbing compounds, trihalomethane precursors, as well as fulvic acid- and humic acid-like fluorescent materials, were more liable to be to be rejected from the ice phase and were more easily retained in the unfrozen liquid phase during water freezing, as compared with organics (on average) that comprise DOC. In addition, it was also found a higher accumulation of these organics in the unfrozen liquid phase during water freezing at higher temperature. The freeze/thaw processes altered the quantity, optical properties, and chlorine reactivity of DOM. The decrease in ultraviolet light at 254 nm as well as the production of aromatic protein- and soluble microbial byproduct-like fluorescent materials in DOM due to freeze/thaw were consistently observed. On the other hand, the changes in DOC, trihalomethane formation potential, and fulvic acid- and humic acid-like fluorescence caused by freeze/thaw varied significantly between samples.     

长沙大气中VOCs研究

应用大气采样罐采样技术和色谱-质谱联用（GC-MS）技术,对2008年长沙市大气中76种挥发性有机物（VOCs）的组分及其质量浓度水平进行测试,比较了各组分对臭氧产生的影响潜势,同时对其主要来源进行简单分析.结果表明,长沙大气总VOCs在上午和下午的浓度分别是38.4×10-9（体积分数）和22.7×10-9（体积分数）,下午大气中VOCs浓度显著低于上午;季节变化呈现VOCs冬季浓度远高于夏季VOCs浓度,组分中以卤代烃最高,烷烃、芳烃次之,烯烃最低,OH消耗速率最高的物质是间、对二甲苯（10.71×10-9 C,碳单位体积比,下同）;其次为1,2,4-三甲苯（6.04×10-9 C）和1,3,5-三甲苯（2.23×10-9 C）.芳烃对大气O3生成贡献最大（66%）,其次是烯烃（26%）,烷烃最低（8%）.高浓度的异戊烷和丙烷说明了机动车排放和液化石油气是VOCs来源之一,苯/甲苯的特征比值接近0.8,远高于机动车尾气排放特征比值0.5;说明溶剂和涂料挥发是其主要来源之一.     

基于聚类分析的长治市夏季VOCs来源及活性

分析长治市夏季环境VOCs浓度及其反应活性（以OH·消耗速率计）,基于聚类分析与正定矩阵因子分解法 （PMF）解析VOCs来源.结果表明：长治市总VOCs平均浓度为37.40 μg/m³,平均活性水平为5.07s^-1,具有本地新鲜排放和反应后混合的特征.机动车排放、燃煤、液化石油气/天然气（LPG/ NG）使用、工艺过程和溶剂使用源对环境VOCs的贡献分别为29.7%、29.2%、23.5%、11.6%和6.1%;对具有新鲜排放特征VOCs的贡献分别为34.6%、38.4%、10.1%、8.5%和8.5%.长治市VOCs主要受本地机动车与燃煤源排放的影响,而LPG/ NG使用源与工艺过程源可通过区域传输影响本地环境VOCs.可见,有效控制本地机动车与燃煤源排放、加强市区周边LPG/NG使用与工艺过程源的联防联控,是降低长治市环境VOCs浓度与O₃生成的有效途径.     

兰州市低碳数正构烷烃组分特征及大气化学反应活性分析

为明确兰州市大气环境常态下低碳数正构烷烃（C₅~C₁₉）质量浓度变化、组分特征及大气化学反应活性之间的关系,于2017年11月-2018年6月选取兰州市5个采样点,利用TENAX吸附管采集空气样品,应用TD-GC/MS（热脱附-气质联用）法对样品进行分析.对空气样品中低碳数正构烷烃大气化学反应活性的OFP（臭氧生成潜势）、·OH消耗速率、SOA（二次有机气溶胶）生成潜势进行评估计算,通过相关性分析及因子分析法分析低碳数正构烷烃的大气化学反应活性贡献率特征.结果表明:①在10种低碳数正构烷烃中,正己烷（C₆）对OFP的贡献率最大,正辛烷（C₈）对·OH消耗速率的贡献率最大,二者的贡献率分别为37.71%和37.64%.②在10种低碳数正构烷烃中正辛烷（C₈）对SOA生成潜势的贡献率最大,为50.02%.③大气化学反应活性参数相关性分析表明,低碳数正构烷烃总质量浓度与OFP、·OH消耗速率相关性显著（R分别为0.895和0.948）.④因子分析表明,5个未知因子所包含的化学反应活性信息量在94.511%以上,所含信息量也体现了未知因子组成的重要性,可为进一步解析大气化学反应活性提供参考.研究显示,正辛烷、正己烷是低碳数正构烷烃的2个关键活性组分,正辛烷是大气化学反应活性贡献率最大的化合物之一,也是汽车尾气排放源的主要组成部分,正己烷是人为源与自然源的混合产物.      

Pressure relief sizing of reactive system using DIERS simplified methods and dynamic simulation method

Incidents involving uncontrolled chemical reactions continue to result in fatality, injury and economic loss. These incidents are often the result of inadequate pressure relief system designs due to a limited knowledge of the chemical reactivity hazard. A safe process design requires knowledge of the chemical reactivity of desired as well as undesired chemical reactions due to upset conditions. Simplified, cost effective methods to relief system sizing are presented by The Design Institute of Emergency Relief Systems (DIERS). They require multiple experiments, and sizing is only valid for the system composition and thermal inertia represented by the small scale experiments. Results are often conservative, especially for gassy systems. Detailed, dynamic computer simulation is highly accurate and can be used for iterative design and multiple scenario evaluation.In this study, an accelerating rate calorimeter (ARC^®) and a low thermal inertia calorimeter (automatic pressure tracking adiabatic calorimeter – APTAC™) were used to collect chemical reactivity data for the dicumyl peroxide and toluene system. Results of the pressure relief system sizing using the dynamic simulation method are presented and compared with DIERS simplified methods.     

上海城郊夏季大气VOCs在臭氧生成中的作用

为研究上海市夏季臭氧高发季节大气VOCs在臭氧生成中作用,选取2018年5～8月大气臭氧较高的时段,在淀山湖科学观测研究站对103种挥发性有机物、臭氧和氮氧化物等环境污染物进行观测.结果表明,上海臭氧高发季节大气平均φ(VOCs)为32.7×10-9,羰基化合物是VOCs的主要组分,所占质量分数达35.0％.羰基化合物...     

济南市城区夏季臭氧污染过程及来源分析

2019年夏季,在济南市城区开展了大气臭氧(O3)及其前体物[挥发性有机物(VOCs)和氮氧化物(NOx)]的综合观测研究,观测发现,日最大8h φ(O3)均值为(103.0±14.5) ×10-9,φ(NOx)平均值为(16.7±11.3) ×10-9,VOCs的体积分数和活性水平分别为(22.4±9.4)×10-9...     

杭州市城区挥发性有机物污染特征及反应活性

使用Summa罐在杭州市城区朝晖站点离线采样,利用GCMS分析122种挥发性有机物（VOCs）.通过2018年5月至2019年4月连续1a的观测,结果发现,观测期间大气VOCs平均体积分数为（59.4±23.6）×10^-9,浓度高值出现在12月而低值出现在2月,含氧有机物（OVOC）,尤其是醛酮类化合物是占比最高的组分,在夏季尤甚.朝晖站点VOCs浓度没有明显的周末效应,但节假日的VOCs浓度有明显下降.其大气VOCs浓度与空气质量指数（AQI）值呈现正相关性,首要污染物为PM_2.5时观测到的VOCs浓度最高.运用·OH消耗速率（L^·OH）和臭氧生成潜势（OFP）做大气反应活性评估,观测期间L^·OH均值为7.5 s^-1,OFP均值为152.1×10^-9,醛酮类化合物、芳烃和烯烃是活性最高的组分,该站点整体大气活性水平与2-甲基戊烷相当.观测期间甲苯/苯（T/B）均值为1.95,说明杭州市城区受到较明显的机动车排放影响.使用正定矩阵因子分析法（PMF）解析出杭州全年VOCs污染的6个因子,分别为二次生成（17.6%）、燃烧源（11.8%）、工艺过程（12.3%）、溶剂使用（18.1%）、天然源（4.5%）和机动车尾气（35.7%）.     

南京北郊秋季VOCs及其光化学特征观测研究

采用GC5000挥发性有机物在线监测系统和EMS系统,于2011年11月在南京北郊开展了为期一个月的连续观测,分别测量了大气中56种VOCs组分和反应性气体(NOx、CO和O3).结果表明,南京北郊的VOCs小时平均体积分数大约在48.17×10-9,日变化呈明显双峰型特征,受机动车影响比较显著,极小值出现在下午16:00,白天与O3浓度曲线呈负相关;VOCs的平均OH消耗速率常数约为3.26×10-12cm3.(molecule.s)-1,最大增量反应活性约为3.26 mol·mol-1;烯烃对OH消耗速率(LOH)和臭氧生成潜势(OFP)贡献率最大,芳香烃次之,而烷烃在大气中含量最为丰富,却并不是LOH和OFP主要贡献者;VOCs关键活性组分是乙烯、丙烯、1-丁烯、间,对-二甲苯及异戊二烯等物质;臭氧生成过程处于VOCs控制区.     

Effects of atamp-charging coke making on strength and high temperature thermal properties of coke

The stamp-charging coke making process has some advantages of improving the operation environment, decreasing fugitive emission, higher gas collection efficiency as well as less environmental pollution. This article describes the different structure strength and high temperature thermal properties of 4 different types of coke manufactured using a conventional coking process and the stamp-charging coke making process. The 4 kinds of cokes were prepared from the mixture of five feed coals blended by the petrography blending method. The results showed that the structure strength indices of coke prepared using the stamp-charging coke method increase sharply. In contrast with conventional coking process, the stamp-charging process improved the coke strength after reaction but had little impact on the coke reactivity index.