Source apportionment of VOCs in a typical medium-sized city in North China Plain and implications on control policy

Characteristics of atmospheric VOCs (volatile organic compounds) have been extensively studied in megacities in China, however, they are scarcely investigated in medium/small-sized cities in North China Plain (NCP). A comprehensive research on possible sources of VOCs was conducted in a medium-sized city of NCP, from May to September 2019. A total of 143 canister samples of 8 sites in Xuchang city were collected, and 57 VOC species were detected. The average VOC concentrations were 42.6 ± 31.6 μg/m³, with 53.7 ± 31.0 μg/m³ and 32.1 ± 27. 8 μg/m³, in the morning and afternoon, respectively. Alkenes and aromatics contributed 80% of the total ozone formation potential (OFP). Aromatics accounted for more than 95% of secondary organic aerosol potential (SOAP). VOCs were dominated by the local emission with significant transport from the southeast direction. PMF analysis extracted 6 sources, which were combustion (33.1%), LPG usage (19.3%), vehicular exhaust & fuel evaporation (15.8%), solvent usage (15.2%), industrial (9.11%) and biogenic (7.51%), respectively and they contributed 33.4%, 17.6%, 12.9%, 18.6%, 9.28% and 8.22% to the OFP, respectively. Combustion and LPG usage were the dominant VOC sources; and combustion, solvent usage and LPG usage were the main sources of OFP in Xuchang city, which were different to megacities in China with a high contribution from vehicular exhaust, solvent usage and industry, suggesting specific control strategies on VOCs need to be implemented in medium-sized city such as Xuchang city.     

Emission of particulate and gaseous pollutants from household laser processing machine

Indoor air quality (IAQ) directly affects the health of occupants. Household manufacturing equipment (HME) used for hobbies or educational purposes is a new and unexplored source of air pollution. In this study, we evaluated the characteristics of particulate and gaseous pollutants produced by a household laser processing equipment (HLPE). Various target materials were tested using a commercial HLPE under various operating conditions of laser power and sheath air flow rate. The mode diameters of the emitted particles gradually decreased as laser power increased, while the particle number concentration (PNC) and particle emission rate (PER) increased. In addition, as the sheath air flow rate quadrupled from 10 to 40 L/min, the mode diameter of the emitted particles decreased by nearly 25%, but the effect on the PNC was insignificant. When the laser induced the target materials at 53 mW, the mode diameters of particles were <150 nm, and PNCs were >2.0 × 10⁴ particles/cm³. Particularly, analyses of sampled aerosols indicated that harmful substances such as sulfur and barium were present in particles emitted from leather. The carcinogenic gaseous pollutants such as acrylonitrile, acetaldehyde, 1,3-butadiene, benzene, and C₈ aromatics (ethylbenzene) were emitted from all target materials. In an actual indoor environment, the PNC of inhalable ultrafine particles (UFPs) was >5 × 10⁴ particles/cm³ during 30 min of HLPE operation. Our results suggest that more meticulous control methods are needed, including the use of less harmful target materials along with filters or adsorbents that prevent emission of pollutants.     

Contaminants of Emerging Concern in Fish from Western U.S. and Alaskan National Parks — Spatial Distribution and Health Thresholds

Remote national parks of the western U.S. and Alaska are not immune to contaminants of emerging concern. Semivolatile organic compounds (SOCs) such as pesticides and PCBs can selectively deposit from the atmosphere at higher rates in cold, high‐elevation and high‐latitude sites, potentially increasing risk to these ecosystems. In the environment, SOCs magnify up food chains and are known to increase health risks such as cancer and reproductive impairment. One hundred twenty‐eight fish in 8 national parks in Alaska and the western U.S. were analyzed for contaminant concentrations, assessed by region, and compared to human and wildlife health thresholds. SOC concentrations from an additional 133 fish from a previous study were also included, for a total of 31 water bodies sampled. PCBs, endosulfan sulfate, and p,p′‐DDE were among the most frequently detected contaminants. Concentrations of historic‐use pesticides dieldrin, p,p′‐DDE, and/or chlordanes in fish exceeded USEPA guidelines for human subsistence fish consumers and wildlife (kingfisher) health thresholds at 13 of 14 parks. Average concentrations in fish ranged from 0.6‐280 ng/g lipid (0.02‐7.3 μg/g ww). Contaminant loading was highest in fish from Alaskan and Sierra Nevada parks. Historic compounds were highest in Alaskan parks, while current‐use pesticides were higher in the Rockies and Sierra Nevada. This study provides a rigorous analysis of CECs in fish from national parks and identifies regions at potential risk.     

生物源挥发性有机物(BVOCs)排放模型及排放模拟研究综述

近30年来,为了掌握BVOCs排放的规律和特征,进一步定量分析评价空气质量和气候变化,向决策者制定相应措施提供科学有效的依据,研究者们致力于研究BVOCs排放机理及其影响因素,并据此建立多种BVOCs排放模型,以模拟区域及全球BVOCs排放。从算法、数据、应用以及局限性4个方面入手,系统回顾了BEIS、GIoBEIS、MEGAN等BVOCs排放模型的研发进程,并评述了国内外BVOCs排放模拟的研究历程,最后从加强机研究、遥感数据的应用、与气候模型及动态植被模型耦合等方面对BVOCs排放模型发展方向进行了展望。     

罐采样-GC/MS法测定环境空气中挥发性有机物

采用SUMMA罐采样,空气预浓缩与气相色谱/质谱联用技术,建立了39种常见挥发性有机物的分析方法。选取攀枝花市不同功能区的5个测点,采集了4个季度的环境空气样品220个,定性检出挥发性有机物54种,其中烃类占24%,卤代烃类占52%,含氧化合物占22%,其它化合物占2%。苯系物的检出率最高。定量的挥发性有机物最大浓度和平均浓度最高的项目均为苯,平均浓度4.59μg/m3,最大浓度29.8μg/m3。苯系物时间分布呈现出旱季高,雨季低的特点;日变化特征为早晨最高,整体呈下降趋势。     

长三角背景大气PM2.5中非极性有机化合物组成特征及来源

为了探究长三角区域大气细颗粒物中非极性有机化合物的组成及来源特征,于2019年12月至2020年11月在临安区域大气本底站采集了129个PM_2.5样品,对其有机碳(OC)、元素碳(EC)和非极性有机化合物(NPOCs,包括多环芳烃、正构烷烃和藿烷类)进行了分析,并用分子示踪物、特征比值和正定矩阵因子分析模型等方法探究了有机气溶胶的主要来源.结果表明,临安ρ(PM_2.5)的年平均值约为(32.36±20.44)μg·m^-3,ρ(NPOCs)年平均值约为(59.05±40.39)ng·m^-3,呈现出冬高夏低的季节变化特征.正构烷烃主要源于化石燃料和生物质(草和木材等)燃烧等人为源,其次为高等植物角质层蜡排放;多环芳烃主要源于燃煤燃烧、机动车排放和生物质燃烧等非化石源的混合贡献;藿烷类物质主要源于机动车排放,其中冬季还受到燃煤源的影响.后向轨迹聚类分析和潜在源区分析表明临安主要受到外来气团输送的影响.结合正定矩阵因子分析模型对采样期间观测到的NPOCs进行源解析,得到了燃煤燃烧源、交通排放源和生物质燃烧等...     

全氟和多氟烷基化合物微生物降解与转化研究进展

全氟和多氟烷基化合物(PFASs)因其持久性、长距离迁移性、生物积累性和生物毒性而受到广泛关注.目前世界上对环境中PFASs的监测和管控主要针对全氟烷基酸(PFAAs).而大部分多氟烷基化合物在环境中能够被微生物降解为PFAAs,也被称为前体物.因此,探究前体物在环境中的微生物转化行为有助于综合评价PFASs的环境风险,以及制定相关的管控和修复措施.虽然PFAAs一直被认为是环境中的“永久化合物”,但近年来,PFAAs的厌氧微生物还原脱氟作为一项极具潜力且充满挑战的修复技术,成为研究的一个前沿热点.系统总结了前体物(氟调化合物和全氟辛烷磺胺衍生物)、 PFAAs和新型PFASs在微生物作用下的降解规律和转化路径,并讨论了PFASs微生物降解的影响因素,最后提出未来的研究方向.     

中国主要背景区域冬季大气PM2.5中非极性有机化合物组成及来源解析

本研究于2019年12月至2020年1月在5个区域大气本底站：临安、金沙、龙凤山、上甸子和瓦里关,同步采集了PM_2.5样品,分析了其中的非极性有机物：多环芳烃、正构烷烃和藿烷类化合物。结果表明,上甸子和龙凤山的多环芳烃平均浓度显著高于其他站点,分别为35.2±25.6 ng/m³和27.5±16.8 ng/m³;藿烷类物质的浓度在上甸子和临安出现高值,分别为2.72±1.78 ng/m³和2.47±0.990 ng/m³;正构烷烃浓度以临安最高,为86.7±40.6 ng/m³。对各站点多环芳烃和藿烷类化合物采用比值法,正构烷烃采用主峰碳数（C_max）、碳优势指数（carbon preference index,CPI）和植物蜡贡献率（% Wax C_n）,结合主成分分析-多元线性回归模型（PCA/MLR）综合进行源解析。结果显示采样期间除瓦里关外,其余站点燃烧源均以化石燃料源为主,贡献率分别为临安（94.9%） > 金沙（75.3%） > 龙凤山（74.7%） > 上甸子（62.5%） > 瓦里关（35.6%）。后向轨迹聚类分析（HYSPLIT）和潜在源贡献因子分析法（PSCF）表明各站点主要受到外来传输气团的影响,并查明了各站点的潜在污染源区。对背景站点的研究表明,东北地区和京津冀地区PM_2.5中非极性有机物来源相似,京津冀地区的生物质燃烧源贡献率高于东北地区;长江中下游地区化石燃料贡献率显著高于生物质燃烧;华中地区燃煤和交通排放源排放贡献率均低于长江三角洲地区;青藏高原地区生物质燃烧贡献率远高于其他地区。     

内蒙古河套灌区春小麦挥发性有机物排放特征

于2021年5月下旬至6月中旬,采用动态箱采样法对内蒙古河套灌区17种春小麦排放生物源挥发性有机物(BVOC)进行了研究,同时记录了温度、湿度和光合有效辐射(PAR)等参数.结果表明:内蒙古河套灌区春小麦主要排放异戊二烯、α-蒎烯和甲苯,生长期其排放率分别为(0.85~39.31),(2.60~14.32)和(6.41~35.39)ng/(g·h),成熟期其排放率分别为(1.75~7.99),(1.11~5.81)和(1.91~25.61)ng/(g·h);生长期异戊二烯、单萜烯类和BTEX标准状态(T=303K,PAR=1000µmol/(m²·s))下排放率分别为(12.92±5.14),(11.98±7.13)和(23.13±7.32)ng/(g·h),成熟期分别为(2.47±0.64),(5.73±1.19)和(14.23±5.27)ng/(g·h),生长期的排放率明显大于成熟期;一定环境温度和PAR范围内,河套灌区春小麦BVOC排放率与环境温度和PAR均呈指数相关,具有明显的日变化特征,但环境温度超过45℃时会抑制其BVOC排放率.     

Characteristics of ambient volatile organic compounds during spring O3 pollution episode in Chengdu, China

Surface ozone (O₃) has become a critical pollutant impeding air quality improvement in many Chinese megacities. Chengdu is a megacity located in Sichuan Basin in southwest China, where O₃ pollution occurs frequently in both spring and summer. In order to understand the elevated O₃ during spring in Chengdu, we conducted sampling campaign at three sites during O₃ pollution episodes in April. Volatile organic compounds (VOCs) compositions at each site were similar, and oxygenated VOCs (OVOCs) concentrations accounted for the highest proportion (35%-45%), followed by alkanes, alkens (including acetylene), halohydrocarbons, and aromatics. The sensitivity of O₃ to its precursors was analyzed using an observation based box model. The relative incremental reactivity of OVOCs was larger than other precursors, suggesting that they also played the dominant role in O₃ formation. Furthermore, the positive matrix factorization model was used to identify the dominant emission sources and to evaluate their contribution to VOCs in the city. The main sources of VOCs in spring were from combustion (27.75%), industrial manufacturing (24.17%), vehicle exhaust (20.35%), and solvent utilization (18.35%). Discussions on VOCs and NO_x reduction schemes suggested that Chengdu was typical in the VOC-limited regime, and VOC emission reduction would help to prevent and control O₃. The analysis of emission reduction scenarios based on VOCs sources showed that the emission reduction ratio of VOCs to NO₂ needs to reach more than 3 in order to achieve O₃ prevention. Emission reduction from vehicular exhaust source and solvent utilization source may be more effective.