The pollution levels, variation characteristics, sources and implications of atmospheric carbonyls in a typical rural area of North China Plain during winter

Atmospheric carbonyls were measured at a typical rural area of the North China Plain (NCP) from November 13 to December 24, 2017 to investigate the pollution characteristics, sources and environmental implications. Fifteen carbonyls were detected, and formaldehyde, acetaldehyde and acetone accounted for about 81% at most. The concentration of the total carbonyls in heavily polluted days was twice more than that in clean days. In contrast to other carbonyls, m-tolualdehyde exhibited relatively high concentrations in the clean days in comparison with the polluted days. The ratios of three principal carbonyls to CO showed similar daily variations at different pollution levels with significant daytime peaks. Multiple linear regression analysis revealed that the contributions of background, primary and secondary sources to three principal carbonyls showed similar variation trends from the clean level to the heavily polluted level. The OH formation rate of formaldehyde showed a similar variation trend to its photodegradation rate, reaching the peak value at noon, which is important to maintain relatively high OH levels to initiate the oxidation of various gas-phase pollutants for secondary pollutant formation at the rural site. OH radical consumption rate and ozone formation potential (OFP) calculations showed that formaldehyde and acetaldehyde were the dominant oxidative species among measured carbonyls. As for OH radical consumption, n-butyraldehyde and m-tolualdehyde were important contributors, while for ozone formation potential, n-butyraldehyde and propionaldehyde made significant contributions. In addition, the contribution of carbonyl compounds to secondary organic aerosol (SOA) formation was also important and needs further investigation.     

Characteristics and ozone formation potential of volatile organic compounds in emissions from a typical Chinese coking plant

Coking industry is an important volatile organic compounds (VOCs) emission source in China, however, detailed information on VOCs emissions is lacking. Therefore, we selected a typical mechanized coking plant and collected air samples according to the Emission Standard of Pollutants for Coking Chemical Industry (GB16171-2012). Using gas chromatography-mass spectrometry method, we analyzed the VOCs in the air samples, and applied maximum increment reactivity (MIR) rule to estimate ozone formation potential (OFP) of the VOCs emitted from the coke production. More than 90 VOCs species were detected from the coking plant, including alkanes, alkenes, alkynes, aromatic hydrocarbons, halogenated hydrocarbons and oxygenated VOCs. The concentrations of VOCs (ρ(VOCs)) generated at different stages of the coking process are significantly different. ρ(VOCs) from coke oven chimney had the highest concentration (87.1 mg/m³), followed by coke pushing (4.0 mg/m³), coal charging (3.3 mg/m³) and coke oven tops (1.1 mg/m³). VOCs species emitted from the coke production processes were dominated by alkanes and alkenes, but the composition proportions were different at the different stages. Alkenes were the most abundant emission species in flue gases of the coke oven chimney accounting for up to 66% of the total VOCs, while the VOCs emissions from coke pushing and coal charging were dominated by alkanes (36% and 42%, respectively), and the alkanes and alkenes emitted from coke oven top were similar (31% and 29%, respectively). Based on above results, reduction of VOCs emissions from coke oven chimney flue gases is suggested to be an effective measure, especially for alkenes.     

Characteristics of atmospheric volatile organic compounds in urban area of Beijing: Variations, photochemical reactivity and source apportionment

Atmospheric volatile organic compounds (VOCs) were observed by an on-line gas chromatography-flame ionization detector monitoring system from November 2016 to August 2017 in Beijing. The average concentrations were winter (40.27 ± 25.25 μg/m³) > autumn (34.25 ± 19.90 µg/m³) > summer (32.53 ± 17.39 µg/m³) > spring (24.72 ± 17.22 µg/m³). Although benzene (15.70%), propane (11.02%), ethane (9.32%) and n-butane (6.77%) were the most abundant species, ethylene (14.07%) and propene (11.20%) were the key reactive species to ozone formation potential (OFP), and benzene, toluene, ethylbenzene, m-xylene + p-xylene and o-xylene (54.13%) were the most reactive species to secondary organic aerosol formation potential (SOAFP). The diurnal and seasonal variations indicated that diesel vehicle emission during early morning, gasoline vehicle emission at the traffic rush hours and coal burning during the heating period might be important sources. Five major sources were further identified by positive matrix factorization (PMF). The vehicle exhaust (gasoline exhaust and diesel exhaust) was found to be contributed most to atmospheric VOCs, with 43.59%, 41.91%, 50.45% and 43.91%, respectively in spring, summer, autumn and winter; while solvent usage contributed least, with 11.10%, 7.13%, 14.00% and 19.87%, respectively. Biogenic emission sources (13.11%) were only identified in summer. However, both vehicle exhaust and solvent usage were identified to be the key sources considering contributions to the OFP and SOAFP. Besides, the contributions of combustion during heating period and gasoline evaporation source during warm seasons to OFP and SOAFP should not be overlooked.     

我国固定源挥发性有机物污染管控的现状与挑战

挥发性有机物（VOCs）成为PM_2.5和臭氧（O₃）协同控制的核心污染物之一,但目前VOCs污染控制仍处于摸索阶段,其控制措施的有效性有待总结研究.为了进一步推动VOCs管控的有效性和科学性,对VOCs的定义、表征方法、排放标准、全过程控制技术及相应制度体系的现状进行了梳理,分析了存在的问题,并提出了相应的对策建议.结果表明:①国家和地方对VOCs的定义尚未统一,导致管控范围不明确,因此建议基于VOCs的物理性质（沸点和蒸气压）确定其管控范围,并与恶臭物质、有毒有害污染物分类协同控制,研究制定豁免清单和优先控制清单.②通过比较VOCs表征和监测方法的差异发现,非甲烷总烃（NMHC）的检测方法在稳定性、可靠性方面尚存在不足,建议建立总碳氢化合物（THC）与NMHC相结合的监测方法.③基于全过程控制技术体系的概念,分析并发现源头控制、过程控制、末端治理措施实施中存在投入和产出不平衡、稳定达标困难等问题,建议基于治理措施的全生命周期综合效益评价,建立最佳治理技术筛选方法.④针对VOCs排放总量控制制度与排污许可证制度、排放税制度等尚未有效联动的问题,建议统一总量核算办法、增设专门的VOCs排放税.⑤鉴于国家和地方排放标准存在差异,建议制定区域一体化排放标准以避免某些产业在有限区域内简单转移.      

四川省典型行业挥发性有机物源成分谱

本研究选取了四川省汽车制造、木制家具、人造板制造、涂料生产和合成树脂生产等挥发性有机物(VOCs)排放源典型行业,通过GC-MS国标方法分析各环节有组织排放的VOCs组分,采用排放总量归一化法处理,获取了四川省汽车制造等典型行业挥发性有机物的成分谱.结果表明,汽车整车制造、木制家具和油性涂料生产企业的VOCs主要组分为芳香烃和含氧化合物,占总VOCs的70%以上,汽车零部件制造企业排放物种主要为芳香烃,其占比达90%以上.人造板制造业含氧化合物占比达97%,其中甲醛占比为75%,其次为异丙醇、丙酮等物质.合成树脂行业芳香烃、烯烃占比较高,占比之和达80%以上,其中烯烃物种主要为1,3-丁二烯和1-丁烯.不同行业排放物种虽存在一定差异,但主要以芳香烃和含氧化合物为主,因此,应加强对芳香烃和含氧化合物等浓度高、活性高、毒性大的组分进行识别和控制,采取源头、过程和末端全过程控制,达到总量减排的效果.     

阳泉市区夏季挥发性有机物污染特征、来源解析及其环境影响

采集阳泉市区夏季3个监测点的环境空气样品,利用气相色谱-质谱/氢火焰离子化检测器(GC-MSD/FID)测定了挥发性有机物(VOCs)的组成,研究了其浓度特征,运用特征比值法和正定矩阵因子分析模型(PMF)解析了VOCs来源,评估了VOCs对O_3和二次有机气溶胶(SOA)生成的影响.结果表明,阳泉市区VOCs平均总浓度为(82.1±22.7)μg·m~(-3),其中烷烃浓度占比最大(51.8%),其次是芳香烃(17.8%)和烯烃(8.0%),炔烃浓度占比最小(3.8%). VOCs呈现双峰的变化特征,分别于08:00～10:00和18:00～20:00出现峰值,在12:00～14:00出现谷值.苯/甲苯和异戊烷/正戊烷的均值分别为2.1±1.3和1.7±0.6,表明环境空气VOCs可能受燃煤排放和机动车排放的双重影响. PMF解析出VOCs来源分别为燃煤源(34.9%)、机动车排放源(18.2%)、汽油挥发源(15.2%)、工业排放源(13.6%)、植物排放源(9.2%)和溶剂使用源(9.0%). VOCs臭氧生成潜势(OFP)均值为156.6μg·m~(-3),烯烃贡献最大,二次有机气溶胶生成潜势(SOA_p)均值为68.7μg·m~(-3),芳香烃的贡献达到93.4%.总之,燃煤排放对VOCs的贡献较高,因此,控制燃煤源排放是阳泉市区VOCs管控重点,需加快矸石山治理和能源结构调整,同时机动车排放源、汽油挥发源和工业排放源的管控也不容忽视.     

北方常见绿化树种BVOCs排放特征及其与光合作用参数的相关性

为了解北方常见绿化树种植物源挥发性有机化合物(biogenic volatile organic compounds,BVOCs)的排放特征及其与光合作用参数(净光合速率P_n、气孔导度g_s、胞间CO_2浓度c_i、蒸腾速率T_r)的相关性,本实验采用动态采样装置收集14种落叶乔木BVOCs排放数据.结果表明,不同科属间异戊二烯和总BVOCs(异戊二烯、单萜和倍半萜烯之和)释放速率差异显著(P0.01).除金银木和榆树,其他绿化树种均释放异戊二烯、单萜和倍半萜烯类物质,其中杨柳科(杂交杨‘546’、速生杨‘107’、小叶杨、垂柳)和豆科植物(国槐、刺槐、龙爪槐)排放异戊二烯较多,释放速率在(30.1±4.3)～(91.8±10.0)μg·(g·h)~(-1)之间;木犀科(白蜡、丁香)、蔷薇科海棠、无患子科栾树和槭树科元宝枫主要排放单萜和倍半萜烯,其中白蜡和元宝枫单萜释放速率最高,分别为(10.6±4.8)μg·(g·h)~(-1)和(11.8±6.4)μg·(g·h)~(-1).罗勒烯和β-蒎烯是绿化树种排放的两种主要单萜物质.P_n和g_s与BVOCs释放速率之间无显著相关性,但杨柳科植物异戊二烯(r=0.681,P0.01)和总BVOCs(r=0.698,P0.01)释放速率与叶片T_r呈显著正相关,而豆科植物的总BVOCs释放速率与c_i呈显著正相关(P=0.04).本研究为城市绿化树种的筛选和配置提供科学参考,也为BVOCs释放机制的研究提供理论依据.     

上甸子区域背景站VOCs污染特征及其对臭氧生成贡献

大气中的挥发性有机物(volatile organic compounds,VOCs)作为对流层臭氧和二次有机气溶胶的前体物,在光化学反应和细颗粒物污染中发挥着重要的作用.本研究于2017年9月1～27日在上甸子区域背景站开展VOCs的连续在线观测,对VOCs的浓度水平,时空变化特征,化学反应活性及其对臭氧生成的贡献进行了研究,并运用特征物种比值法对初始VOCs的来源进行了分析.结果表明, 2017年9月上甸子站总VOCs平均体积分数为12.53×10~(-9),其中,烷烃是体积分数最大的组分,占到了总VOCs的65.3%,其次是烯烃和芳香烃,分别占到了总VOCs的26.7%和6.5%.从大气化学活性来看,上甸子站总的L~(·OH)(·OH损耗率)为5.2 s~(-1),其中C4～C5烯烃占到了61%,其次是C2～C3烯烃,占到了12.8%.VOCs的臭氧生成潜势平均值为36.5×10~(-9),烯烃是贡献最大的组分,占到了71.2%.烯烃中又以C4～C5烯烃的贡献最为突出,而体积分数较大的烷烃对臭氧生成的贡献却不大.对特征物种的比值研究发现,上甸子站VOCs受生物质燃烧和燃煤排放的影响较大,除此之外,交通排放源也有一定的影响,完全不受工业排放源的影响.     

基于实测的建筑类涂料挥发性有机物(VOCs)含量水平及组分特征

选取内墙涂料、外墙涂料、防水涂料、地坪涂料、防腐涂料5类建筑涂料为研究对象,通过对企业生产与市场销售的涂料抽检获取涂料样品,利用国内建筑涂料挥发性有机化合物标准检测方法,对其VOCs含量水平及组分特征进行检测.结果表明,内墙涂料与外墙涂料VOCs含量水平分别处于0~145 g·L~(-1)与0~171 g·L~(-1)之间,内墙面漆、内墙底漆、外墙面漆与外墙底漆符合HJ 2537-2014中VOCs含量限值的样品数分别占抽检样品总数的90%、80%、96%与94%,VOCs含量水平较低.90%以上聚合物水泥防水涂料与丙烯酸酯聚合物乳液防水涂料VOCs含量水平都小于10 g·L~(-1),聚氨酯防水涂料VOCs含量水平处于1~324 g·L~(-1)之间.溶剂型涂料VOCs含量水平总体很高,溶剂型防腐涂料与溶剂型地坪涂料VOCs含量水平分别处于291~681 g·L~(-1)与16~580 g·L~(-1),不同成分与不同品牌溶剂型涂料VOCs含量水平有很大差异.水性建筑涂料中VOCs物种占比最高的是1,2-丙二醇与乙二醇,其次是甲醇与2-氨基-2-甲基-1-丙醇,不同品牌涂料使用的醇类物质种类与比例不同.溶剂型建筑涂料中VOCs物种主要包括甲苯、乙苯、间/邻/对二甲苯等芳香烃类,乙酸乙酯、乙酸丁酯与乙酸异丁酯等酯类.     

广东省秸秆燃烧大气污染物及VOCs物种排放清单

基于广东省粮食产量的统计年鉴,建立了广东省2008~2016年秸秆燃烧污染物排放清单和2016年广东省秸秆燃烧VOCs物种清单,并对VOCs臭氧生成潜势进行评估.结果表明,2013~2016年广东省秸秆燃烧各大气污染物排放量较2008~2012年有所降低.这主要是由于禁止秸秆露天燃烧政策的出台及农村生活水平的提高降低了秸秆燃烧比例.2016年各类大气污染物SO_2、NO_x、NH_3、CH_4、EC、OC、NMVOC、CO和PM_(2.5)的排放量依次为2 443.7、16 187.9、6 943.8、29 174.4、3 625.5、14 830.7、65 612.6、591 613.9和49 463.0 t.稻谷秸秆燃烧是最主要的秸秆燃烧污染物来源,占据了污染物总排放量的约68.55%.污染物贡献最大的5个市分别为湛江、茂名、梅州、肇庆和韶关,约占总排放量的58.63%.2016年广东省秸秆燃烧VOCs物种排放清单中,排放量贡献前10的物种分别为:乙烯、乙醛、甲醛、苯、乙炔、丙烯、乙烷、甲苯、正丙烷和丙醛,占总VOCs量的67.91%.在VOCs物种清单的基础上估算了其臭氧生成潜势(OFP),OFP贡献前10 VOCs物种分别为:乙烯、甲醛、乙醛、丙烯、1-丁烯、丙醛、甲苯、丙烯醛、异戊二烯和丁烯醛,占总OFP量的80.83%.