Release of volatile organic compounds during bio-drying of municipal solid waste

Three treatments were tested to investigate the release concentrations of volatile organic compounds (VOCs) during the bio-drying of municipal solid waste (MSW) by the aerobic and combined hydrolytic-aerobic processes. Results showed that VOCs were largely released in the first 4 days of bio-drying and the dominant components were: dimethyl disulfide, dimethyl sulfide, benzene, 2-butanone, limonene and methylene chloride. Thus, the combined hydrolytic-aerobic process was suggested for MSW bio-drying due to fewer aeration quantities in this phase when compared with the aerobic process, and the treatment strategies should base on the key properties of these prominent components. Malodorous sulfur compounds and terpenes were mainly released in the early phase of bio-drying, whereas, two peaks of release concentrations appeared for aromatics and ketones during bio-drying. Notably, for the combined hydrolytic-aerobic processes there were also high concentrations of released aromatics in the shift from hydrolytic to aerobic stages. High concentrations of released chlorinateds were observed in the later phase. For the VOCs produced during MSW bio-drying, i.e., malodorous sulfur compounds, terpenes and chlorinateds, their release concentrations were mainly determined by production rates; for the VOCs presented initially in MSW, such as aromatics, their transfer and transport in MSW mainly determined the release concentrations.     

TiO_2光催化氧化室内VOCs的失活再生研究进展

半导体TiO2纳米材料由于其无毒无害,化学性质稳定等优点,目前已经成为环境污染控制领域和材料学领域共同研究的热点。TiO2纳米材料对环境污染物光催化氧化效果显著,但是随着TiO2的反复使用,其催化效率会减低,最终失去光催化的活性;文章主要对TiO2在光催化降解环境污染物后的失活和再生情况进行了综述,讨论了TiO2光催化剂失活的机理以及其再生的途径。     

杭州COVID-19期间大气VOCs体积分数变化特征

2019年12月1日至2020年3月31日新型冠状病毒肺炎(COVID-19)期间,采用Syntech Spectras GC955在线气相色谱仪对杭州市大气环境中挥发性有机物(VOCs)进行了在线连续监测,分析了 VOCs的组成特征、日变化规律和大气化学反应活性.结果表明,不同站点疫情前φ(总VOCs)均最高,一级响...     

大气中痕量挥发性有机物分析方法研究

利用自行研制的累积式大气采样装置、大气痕量有机物二步冷冻浓缩进样系统和气相色谱/质谱(GC/MS)联用技术对大气中的痕量挥发性有机物进行分析(CCS-GC/MS),并对分析方法进行了评估.结果表明,CCS-GC/MS系统将单纯GC/MS分析大气中痕量挥发性有机物检测下限体积分数值从10^-6量级扩展到10^-12,39种目标化合物平均响应因子为2.9×10^-12A^-1,1000cm³进样量最低检出限体积分数值为7×10^-12～40×10^-12;流出峰保留时间定性分析相对平均偏差<2.5s,对目标化合物定性分析准确率达到100%;0～400×10^-9浓度范围内外标定量曲线r²平均值大于0.99;回收率为88%～111%,平均值100.8%±5.6%;精密度误差2%～14%,平均6.6%.     

汽车维修行业挥发性有机物排放特征及大气化学反应活性

汽车维修行业挥发性有机物排放是臭氧前体物VOCs的重要来源,但目前汽车维修行业的VOCs减排政策主要基于VOCs的排放量,而没有考虑其化学反应活性,这将影响VOCs减排对改善空气质量的效果.通过分析汽车维修企业不同工段VOCs的产排污节点,结合各工段油漆用量及其VOCs质量分数,采用物料衡算法获得不同工段VOCs产生量及其组分,系统分析末端尾气VOCs的排放特征,并通过计算其臭氧生成潜势评估VOCs各组分的大气反应活性.结果表明,汽车维修行业油漆中产生的VOCs组分主要为苯系物,其中乙酸丁酯和二甲苯的质量分数最高.清漆由于其本身VOCs质量分数较高且用量较大,为汽车维修行业最大的VOCs排放源（92%）.企业采用油性面漆VOCs产生量（22%）比水性面漆（3%）有较大程度增大,采用水性漆对汽修企业减少VOCs排放有显著效果.排气筒尾气中共检测出49种VOCs组分,前10种VOCs组分排放量占总排放量的97.9%,种类相对集中.主要污染物类别为芳香烃类（10种,30.90%~69.30%）,主要组分有间/对-二甲苯（2.89%~45.00%）;其次为OVOC （12种）和卤代烃（22种）,贡献率分别为8.82%~43.71%和2.40%~25.00%,其他组分相对含量较少.芳香烃是汽车维修企业VOCs排放的最大组分,但是在不同研究中主要VOCs种类差异较大.汽车维修企业排放VOCs的OFP平均值为194.04 mg·m^-3,SR平均值为3.37 g·g^-1.间/对-二甲苯对汽车维修行业OFP贡献率最大（70.24%）,为优先控制污染物.芳香烃对OFP的贡献率达到99.29%,是化学反应活性最强的组分.酯类在汽车维修行业VOCs组分中占比较大,但对OFP的贡献率相对较低,因此汽车维修行业应重点控制芳香烃类物质的排放.     

COVID-19疫情期间雄安地区VOCs的变化特征、臭氧生成潜势及来源解析

利用挥发性有机物(VOCs)在线监测数据对新冠肺炎疫情(COVID-19)期间(2019年12月25日～2020年2月24日)雄安地区环境空气中VOCs进行监测,探讨了疫情防控前、后VOCs的变化特征、臭氧生成潜势及来源解析.结果表明,疫情防控后φ(TVOCs)平均值为45.1×10-9,约为疫情防控前φ(TVOCs)...     

Simultaneous determination of three classes of antibiotics in the suspended solids of swine wastewater by ultrasonic extraction, solid-phase extraction and liquid chromatography-mass spectrometry

This work describes a systematic approach to the development of a method for simultaneous determination of three classes of veterinary antibiotics in the suspended solids (SS) of swine wastewater, including five sulfonamides, three tetracyclines and one macrolide (tiamulin). The entire procedures for sample pretreatment, ultrasonic extraction (USE), solid-phase extraction (SPE), and liquid chromatography-mass spectrometry (LC-MS) quantification were examined and optimized. The recovery efficiencies were found to be 76%-104% for sulfonamides, 81%-112% for tetracyclines, and 51%-64% for tiamulin at three spiking levels. The intra-day and inter-day precisions, as expressed by the relative standard deviation (RSD), were below 17%. The method detection limits (MDLs) were between 0.14 and 7.14 μg/kg, depending on a specific antibiotic studied. The developed method was applied to field samples collected from three concentrated swine feeding plants located in Beijing, Shanghai and Shandong province of China. All the investigated antibiotics were detected in both SS and liquid phase of swine wastewater, with partition coefficients (logK_d) ranging from 0.49 to 2.30. This study demonstrates that the SS can not be ignored when determining the concentrations of antibiotics in swine wastewater.     

南京工业区秋季大气挥发性有机物污染特征及来源解析

2018年秋季在南京利用大气挥发性有机物(volatile organic compounds, VOCs)吸附浓缩在线监测系统(AC-GCMS 1000)对大气VOCs进行连续观测,以了解其化学特征、臭氧生成潜势和污染来源.结果表明,南京秋季大气VOCs体积分数为(64.3±45.6)×10~(-9),以烷烃(33.1%)、含氧挥发性有机物(OVOCs)(22.3%)及卤代烃(21.8%)为主.VOCs的昼夜变化呈"双峰型"变化特征,高值主要出现在清晨的06:00～07:00及夜间的18:00～20:00,主要受机动车排放及气象要素的共同影响.秋季南京VOCs的臭氧生成潜势(ozone formation potential, OFP)为267.1μg·m~(-3),主要贡献物种是芳香烃类化合物(55.2%)和烯烃类化合物(20.8%).PMF受体模型源解析确定5个VOCs来源,分别是交通排放(34%)、工业排放(19%)、LPG排放(17%)、涂料及有机溶剂挥发(16%)以及生物质燃烧和燃煤排放(14%),因此控制南京工业区秋季大气污染应主要着力于交通及工业排放的治理.     

上海市排水系统雨天出流及地表径流沉降特性初探

实际SS沉降特性是雨水池、沉淀池设计及优化运行的重要参数.采用累积曲线法测定了上海市典型排水系统雨天出流和地表径流的SS沉降特性.结果表明:地表径流中SS的2 h沉降去除率为58%～88%,且SS沉降去除率随SS初始质量浓度增加呈递增趋势;各类排水系统雨天出流中SS沉降速率和沉降去除率在合流制中相对较大,分流制相对较小,混接的分流制介于前两者之间,SS沉降去除率均在50%以上;合流制中COD的2 h沉降去除率为50%～80%.     

Ambient Air Quality at the Site of a Former Manufactured Gas Plant

Prior to the 1950's, manufactured gas was commerciallyproduced from the pyrolysis of coal, coke, and oil atfacilities that are termed manufactured gas plants (MGPs). The constituents of residual coal tar present on many MGPsites are an environmental health concern because of theirtoxicity and the possibility for their off-site migration viawater and air. Atmospheric concentrations of five volatileorganic compounds (VOCs, e.g., benzene), sixteen polycyclicaromatic hydrocarbons (PAHs, e.g., naphthalene), and particulate matter less than 10 microns in aerodynamicdiameter (PM₁₀) were measured at the site of a former MGP. Air samples were obtained before, during, and after excavationof subterranean coal tar at the site. The results of thisinvestigation indicate that subterranean coal tar was not aprimary source of VOCs and PAHs in the local atmosphere beforeor after remediation of the site. However, excavation,treatment, blending, and transfer of the coal tar duringremediation generated concentrations of selected aromatic andsemi-volatile organic compounds that were substantiallygreater than typical ambient levels. In addition, these datasuggest that blending and mixing of coal tars could lead toexceedance of the U.S. National Ambient Air Quality Standardfor PM₁₀, although additional research is required to fullyevaluate this possibility. Nuisance odors associated with thesite remediation were likely the result of naphthalene andpossibly isomers of xylene. Air pollutant concentrationsmeasured adjacent to the excavation area and at the siteperimeter during remediation activities were less than therelevant occupational and environmental exposure limits.