深圳大学城园区典型OVOCs污染特征与来源解析

采用质子转移反应质谱仪（PTR-MS）对深圳大学城园区2017年不同季节（分干湿两季）的6种典型OVOCs和其他非甲烷烃类（NMHCs）进行连续在线监测,分析其干湿季的浓度特征与日变化规律,并应用光化学龄的参数化方法开展OVOCs的来源解析.结果表明,在观测的6种OVOCs中,甲醇的平均浓度最高,达10×10^-9~12×10^-9,其次是乙酸、丙酮和乙醛,约2~5×10^-9,甲酸和丁酮的含量最低,仅1×10^-9~2×10^-9.通过日变化观察到的OVOCs湿季峰值浓度时间明显早于干季,乙醛表现出与臭氧（O₃）相似的日变化特征,揭示了其可能存在二次来源;甲醇和丁酮的峰值浓度时间均早于O₃,可能存在重要的一次排放源.采用光化学龄模型解析出日间污染物来源比例：在污染较重的干季,甲醇、乙醛、丙酮和丁酮的人为一次源占主导,甲酸和乙酸的二次源是主要贡献者;在较清洁的湿季,天然源成为乙醛、丙酮、丁酮、甲酸和乙酸的主要来源.     

Biogenic volatile organic compound emissions from leaves and fruits of apple and peach trees during fruit development

Biogenic volatile organic compounds (BVOCs) are widely involved in a variety of atmospheric chemical processes due to their high reactivity and species diversity. To date, however, research on BVOCs in agroecosystems, particularly fruit trees, remains scarce despite their large cultivation area and economic interest. BVOC emissions from different organs (leaf or fruit) of apple and peach trees were investigated throughout the stages of fruit development (FS, fruit swelling; FC, fruit coloration; FM, fruit maturity; and FP, fruit postharvest) using a proton-transfer-reaction mass spectrometer. Results indicated that methanol was the most abundant compound emitted by the leaf (apple tree leaf 492.5 ± 47.9 ng/(g·hr), peach tree leaf 938.8 ±  154.5 ng/(g·hr)), followed by acetic acid and green leaf volatiles. Beside the above three compounds, acetaldehyde had an important contribution to the emissions from the fruit. Overall, the total BVOCs (sum of eight compounds studied in this paper) emitted by both leaf and fruit gradually decreased along the fruit development, although the effect was significant only for the leaf. The leaf (2020.8 ±  258.8 ng/(g·hr)) was a stronger BVOC emitter than the fruit (146.0 ± 45.7 ng/(g·hr)) (P = 0.006), and there were no significant differences in total BVOC emission rates between apple and peach trees. These findings contribute to our understanding on BVOC emissions from different plant organs and provide important insights into the variation of BVOC emissions across different fruit developmental stages.     

基于高分辨率在线测量的轻型汽油车含氧挥发性有机物排放模型构建

机动车排放的含氧挥发性有机物(OVOCs)具有较高的大气反应活性,但在线测量识别其高分辨率排放特征的研究仍处于起步阶段,缺乏计算和预测OVOCs排放特征的模型工具.本研究利用质子转移反应飞行时间质谱仪(PTR-TOF-MS)与离子/分子反应质谱仪(IMR-MS),在简易瞬态测试工况下对轻型汽油车排放甲醛、丙酮和乙醇等8种OVOCs组分进行了在线测量.结果表明,OVOCs组分受工况变化影响显著,国Ⅰ～国Ⅴ车辆排放过程中OVOCs排放峰值相对于怠速阶段的增幅分别为183％、105％、56％、92％和244％,同时随着排放标准从国Ⅰ升级到国Ⅴ,含量较高且作为特征组分的甲醛、丙酮和甲醇排放量的降幅分别为90.9％、93.3％和93.7％,但乙醇排放相对稳定.国Ⅰ～国V排放标准下轻型汽油车8种OVOCs总量排放因子分别为12.5、10.2、5.4、4.2和1.6 mg-km-1,总体减排幅度87％.本研究发现OVOCs排放率与比功率(VSP),排放因子与修正碳燃烧效率(MCE)密切相关,将不同排放标准车辆的VSP与排放率和MCE与基于里程的排放因子(EFs)进行拟合,分别建立了一阶线性函数关系.提出了修正碳燃烧损失率(MCL)这一概念,并得到简化的MCL与排放因子的正比例函数关系,从而阐明了OVOCs排放因子的决定性因素.基于VSP和MCL建立的OVOCs排放模型可以计算和预测轻型汽油车在不同热运行状态下的排放率和排放因子,从而为准确评估OVOCs排放贡献和建立排放源清单提供有效工具.     

Characterizing oxygenated volatile organic compounds and their sources in rural atmospheres in China

Oxygenated volatile organic compounds(OVOCs) are important precursors and products of atmospheric secondary pollution. The sources of OVOCs, however, are still quite uncertain,especially in the atmosphere with much pollution in China. To study the sources of OVOCs in rural atmospheres, a proton transfer reaction mass spectrometry(PTR-MS) was deployed at a northern rural site(WD) and a southern rural site(YMK) in China during the summer of 2014 and 2016, respectively. The continuous observation showed that the mean concentration of TVOCs(totally 17 VOCs) measured at WD(52.4 ppbv) was far higher than that at YMK(11.1 ppbv), and the OVOCs were the most abundant at both the two sites. The diurnal variations showed that local sources of OVOCs were still prominent at WD, while regional transport influenced YMK much. The photochemical age-based parameterization method was then used to quantitatively apportion the sources of ambient OVOCs. The anthropogenic primary sources at WD and YMK contributed less(2%–16%) to each OVOC species. At both the sites, the atmospheric background had a dominant contribution(～ 50%) to acetone and formic acid, while the anthropogenic secondary formation was the main source(～ 40%) of methanol and MEK. For acetaldehyde and acetic acid, the biogenic sources were their largest source(～ 40%) at WD, while the background(39%) and anthropogenic secondary formation(42%) were their largest sources at YMK, respectively. This study reveals the complexity of sources of OVOCs in China, which urgently needs explored further.     

Understanding primary and secondary sources of ambient oxygenated volatile organic compounds in Shenzhen utilizing photochemical age-based parameterization method

Oxygenated volatile organic compounds(OVOCs) are key intermediates in the atmospheric photooxidation process. To further study the primary and secondary sources of OVOCs,their ambient levels were monitored using a proton-transfer reaction mass spectrometer(PTR-MS) at an urban site in the Pearl River Delta of China. Continuous monitoring campaigns were conducted in the spring, summer, fall, and winter of 2016. Among the six types of OVOC species, the mean concentrations of methanol were the highest in each season(up to 13–20 ppbv), followed by those of acetone, acetaldehyde and acetic acid(approximately 2–4 ppbv), while those of formic acid and methyl ethyl ketone(MEK) were the lowest(approximately 1–2 ppbv). As observed from a diurnal variation chart, the OVOCs observed in Shenzhen may have been affected by numerous factors such as their primary and secondary sources and photochemical consumption. The photochemical age-based parameterization method was used to apportion the sources of ambient OVOCs. Methanol had significant anthropogenic primary sources but negligible anthropogenic secondary sources during all of the seasons. Acetone, MEK and acetic acid were mostly attributed to anthropogenic primary sources during each season with smaller contributions from anthropogenic secondary sources. Acetaldehyde had similar contributions from both anthropogenic secondary and anthropogenic primary sources throughout the year.Meanwhile, anthropogenic primary sources contributed the most to formic acid.     

四川省人为源挥发性有机物组分清单及其臭氧生成潜势

基于调研文献测试数据,对不含含氧有机物（oxygenated volatile organic compounds,OVOCs）组分的源成分谱进行修订和重构,得到归一化的VOCs源成分谱,根据2015年四川省大气污染源排放清单建立了基于源成分谱的1 km×1 km VOCs组分排放清单,并估算其臭氧生成潜势以评估对臭氧生成的影响.所建立的VOCs源成分谱库包括45个源成分谱和519种组分,由于针对富含OVOCs的生物质燃烧和汽车排放等源类进行了修订和重构,因此所建立的源成分谱库对于VOCs组分清单构建和源解析具有更好地应用性.VOCs组分清单结果表明,四川省人为源VOCs总排放量为773.8 kt,其中烷烃、烯烃、炔烃、芳香烃、OVOCs、卤代烃和其它VOCs分别占VOCs总排放量的21.6%、10.0%、1.7%、28.0%、26.2%、4.2%和8.3%,总臭氧生成潜势（ozone formation potential,OFP）为2584.9 kt,上述各类VOCs分别占总OFP的6.9%、26.1%、0.5%、42.3%、23.2%、0.4%和0.5%.四川省各城市VOCs排放组分均以芳香烃、OVOCs和烷烃为主,但亦存在显著差异：成都、雅安、阿坝、甘孜和凉山机动车排放贡献较大,烷烃排放量占VOCs排放总量的比例较高;攀枝花为工艺过程源贡献较大的重工业城市,烷烃排放量占比较高;德阳、眉山、遂宁和资阳溶剂使用源排放较大,OVOCs排放量占比较高.四川省VOCs排放量和OFP较大的组分主要集中分布于人口和工业较为密集和发达的四川盆地区域以及凉山和攀枝花的部分地区,其中间-二甲苯和甲苯主要贡献源为溶剂使用源,导致其在城市建成区的分布更为集中,生物质燃烧对乙烯和甲醛排放有大量贡献,造成其在农业发达的川东和川南的耕地区域有大量分布.     

西南典型区域夏季大气含氧挥发性有机化合物来源解析

含氧挥发性有机物（OVOCs）是大气光化学过程中的重要中间产物,是臭氧的重要来源之一.利用质子转移反应飞行时间质谱仪（PTR-TOF-MS）在成都平原对OVOCs进行观测,探讨其日变化特征、光化学反应活性、臭氧生成潜势和来源.结果表明,10个VOCs［乙醛、丙酮、异戊二烯、甲基乙基酮（methyl ethyl ketone,MEK）、甲基乙烯基甲酮（methyl vinyl ketone,MVK）、甲基丙烯醛（methacrolein,MACR）、苯、甲苯、苯乙烯、C8芳香烃和C9芳香烃］总浓度（体积分数）为（10.97±4.69）×10^-9,OVOCs为（8.54±3.44）×10^-9,芳香烃为（1.53±0.93）×10^-9,生物源VOCs为（0.90±0.32）×10^-9;光化学活性和臭氧生成潜势均排名前三的物种为：异戊二烯、乙醛和C8芳香烃;3个OVOCs物种（乙醛、丙酮和MEK）主要来源于本地生物源和人为二次源,且丙酮有较强的区域背景值,说明该地区的污染受到较为显著的区域传输的影响.本研究可加深对西南地区臭氧的区域形成机制的认识,为科学管控臭氧污染提供依据.     

珠三角典型工业区挥发性有机物(VOCs)组成特征：含氧挥发性有机物的重要性

挥发性有机物(VOCs)是对流层大气的关键化学组分,其中工业排放是VOCs的重要来源之一.于2021年夏初在中国珠江三角洲的典型工业地区中开展了74种VOCs的在线观测.在整个观测期间,总挥发性有机物(TVOC)的体积分数平均值为(81.9±45.4)×10^-9.其中,含氧挥发性有机物(OVOCs)在TVOC中的占比最大,平均值为51.5%,并且其占比随TVOC体积分数的升高而逐渐增大.芳香烃在TVOC中的占比为19.4%.进一步分析发现,与工业活动相关的排放是工业区环境大气中芳香烃与OVOCs的主要来源.芳香烃和OVOCs对臭氧生成潜势(OFP)的贡献最为显著,在总OFP中的贡献率分别为56.4%和26.7%.此外,与烃类组分相比,OVOCs的大气化学活性同样较高,贡献了大气中总·OH反应活性的40.0%.二甲苯、甲苯、丙烯醛和乙酸乙酯对二次污染形成的贡献较大,在制定大气二次污染管控策略时应优先考虑.研究结果强调了工业地区中OVOCs对TVOC的重要贡献以及OVOCs在大气二次污染形成过程中的重要作用.     

Emission of oxygenated volatile organic compounds (OVOCs) during the aerobic decomposition of orange wastes

Oxygenated volatile organic compounds(OVOCs) emitted from orange wastes during aerobic decomposition were investigated in a laboratory-controlled incubator for a period of two months. Emission of total OVOCs(TOVOCs) from orange wastes reached 1714 mg/dry kg(330 mg/wet kg). Ethanol, methanol, ethyl acetate, methyl acetate, 2-butanone and acetaldehyde were the most abundant OVOC species with shares of 26.9%, 24.8%, 20.3%, 13.9%, 2.8%and 2.5%, respectively, in the TOVOCs released. The emission fluxes of the above top five OVOCs were quite trivial in the beginning but increased sharply to form one "peak emission window" with maximums at days 1–8 until leveling off after 10 days. This type of "peak emission window" was synchronized with the CO2 fluxes and incubation temperature of the orange wastes, indicating that released OVOCs were mainly derived from secondary metabolites of orange substrates through biotic processes rather than abiotic processes or primary volatilization of the inherent pool in oranges. Acetaldehyde instead had emission fluxes decreasing sharply from its initial maximum to nearly zero in about four days,suggesting that it was inherent rather than secondarily formed. For TOVOCs or all OVOC species except 2-butanone and acetone, over 80% of their emissions occurred during the first week, implying that organic wastes might give off a considerable amount of OVOCs during the early disposal period under aerobic conditions.     

食品垃圾好氧降解过程中挥发性有机物(VOCs)排放特征

采用实验室模拟方法,研究了混合食品垃圾(FW)及以橙子、生菜、土豆和西红柿为代表的4种植物性易降解有机垃圾组分好氧降解过程中排放出来的117种挥发性有机物(VOCs)的排放量和组成特征.结果表明,混合食品垃圾好氧降解过程中VOCs总排放量为951.80mg·kg-1,主要为有机硫、含氧化合物和萜烯,分别占VOCs总排放量的43.1%、53.3%和2.1%.橙子、生菜、土豆和西红柿4种植物性易降解有机垃圾好氧降解过程中VOCs的总排放量分别为12736.72、118.67、57.40和228.08mg·kg-1,主要成分均为含氧化合物和萜烯;含氧化合物分别占橙子、生菜、土豆和西红柿4种植物性易降解有机垃圾VOCs总排放量的13.5%、80.9%、85.9%和79.5%,萜烯分别占4种植物性易降解有机垃圾VOCs总排放量的86.5%、16.6%、8.2%和15.6%.