Unique products from the reaction of naphthalene with the hydroxyl radical

Many of the products of the reaction of naphthalene (Naph) with the OH radical in a reaction chamber were identified. Previously unidentified products included 1,2-naphthoquinone (NQ), oxygenated indenes and benzopyrones. Possible pathways for the formation of 1,2-NQ and 1,4-NQ are proposed. In the chamber reactions, more 1,2-NQ than 1,4-NQ partitioned to the particle phase. From this result we infer that, in the atmosphere, the percentage of 1,2-NQ in the particle phase should be greater than that for the 1,4-NQ. Because both of these compounds are considered to be toxic, and since they appear in both the gas and particle phases in the reaction chamber, and by implication in the atmosphere, it is considered important that both the gas and particle phases of these two compounds should be measured to assess their impact on human health.     

Intensified wintertime secondary inorganic aerosol formation during heavy haze pollution episodes (HPEs) in Beijing, China

Air pollution in China is complex, and the formation mechanism of chemical components in particulate matter is still unclear. This study selected three consecutive heavy haze pollution episodes (HPEs) during winter in Beijing for continuous field observation, including an episode with heavy air pollution under red alert. Clean days during the observation period were selected for comparison. The HPE characteristics of Beijing in winter were: under the influence of adverse meteorological conditions such as high relative humidity, temperature inversion and low wind speed; and strengthening of secondary transformation reactions, which further intensified the accumulation of secondary aerosols and other pollutants, promoting the explosive growth of PM_2.5. PM_2.5/CO values, as indicators of the contribution of secondary transformation in PM_2.5, were approximately 2 times higher in the HPEs than the average PM_2.5/CO during the clean period. The secondary inorganic aerosols (sulfate nitrate and ammonium salt) were significantly enhanced during the HPEs, and the conversion coefficients were remarkably improved. In addition, it is interesting to observe that the production of sulfate tended to exceed that of nitrate in the late stage of all three HPEs. The existence of aqueous phase reactions led to the explosive growth sulfur oxidation ratio (SOR) and rapid generation of sulfate under high relative humidity (RH>70%).     

Secondary organic aerosol formation from straw burning using an oxidation flow reactor

Herein, we use an oxidation flow reactor, Gothenburg: Potential Aerosol Mass (Go: PAM) reactor, to investigate the secondary organic aerosol (SOA) formation from wheat straw burning. Biomass burning emissions are exposed to high concentrations of hydroxyl radicals (OH) to simulate processes equivalent to atmospheric oxidation of 0-2.55 days. Primary volatile organic compounds (VOCs) were investigated, and particles were measured before and after the Go: PAM reactor. The influence of water content (i.e. 5% and 11%) in wheat straw was also explored. Two burning stages, the flaming stage, and non-flaming stages, were identified. Primary particle emission factors (EFs) at a water content of 11% (∼3.89 g/kg-fuel) are significantly higher than those at a water content of 5% (∼2.26 g/kg-fuel) during the flaming stage. However, the water content showed no significant influence at the non-flaming stage. EFs of aromatics at a non-flaming stage (321.8±46.2 mg/kg-fuel) are larger than that at a flaming stage (130.9±37.1 mg/kg-fuel). The OA enhancement ratios increased with the increase in OH exposure at first and decreased with the additional increment of OH exposure. The maximum OA enhancement ratio is ∼12 during the non-flaming stages, which is much higher than ∼ 1.7 during the flaming stages. The mass spectrum of the primary wheat burning organic aerosols closely resembles that of resolved biomass burning organic aerosols (BBOA) based on measurements in ambient air. Our results show that large gap (∼60%-90%) still remains to estimate biomass burning SOA if only the oxidation of VOCs were included.     

Significant contribution of secondary particulate matter to recurrent air pollution: Evidence from in situ observation in the most polluted city of Fen-Wei Plain of China

Particulate matter (PM) pollution in high emission regions will affect air quality, human health and climate change on both local and regional scales, and thus attract worldwide attention. In this study, a comprehensive study on PM_2.5 and its chemical composition were performed in Yuncheng (the most polluted city of Fen-Wei Plain of China) from November 28, 2020 to January 24, 2021. The average concentration of PM_2.5 was 87.8 ± 52.0 μg/m³, which were apparently lower than those observed during the same periods of past five years, attributable to the clean air action plan implemented in this region. NO₃⁻ and organic carbon (OC) were the dominant particulate components, which on average contributed 22.6% and 16.5% to PM_2.5, respectively. The fractions of NO₃⁻, NH₄⁺, OC and trace metals increased while those of crustal materials and elemental carbon decreased with the degradation of PM_2.5 pollution. Six types of PM_2.5 sources were identified by the PMF model, including secondary inorganic aerosol (35.3%), coal combustion (28.7%), vehicular emission (20.7%), electroplating industry (8.6%), smelt industry (3.9%) and dust (2.8%). Locations of each identified source were pinpointed based on conditional probability function, potential source contribution function and concentration weighted trajectory, which showed that the geographical distribution of the sources of PM_2.5 roughly agreed with the areas of high emission. Overall, this study provides valuable information on atmospheric pollution and deems beneficial for policymakers to take informed action to sustainably improve air quality in highly polluted region.     

1991年孟加拉湾特大台风灾害

１９９１年４月２９日孟加拉国发生一次特大台风灾害，死亡１３８０００人，损失３０亿美元。事后，孟加拉国政府组织了详细的调配分析。指出平坦低下地形、漏头状海岸线、落后的社会制度、人民极端贫穷是特大灾害的基本原因。另外，人民因过去几次错误预报而不相信台风警报；海堤很差，许多人住在海堤以外，住房很坏，通讯条件落后等等，更加剧了这次灾难。本文介绍这镒台风灾害的形成背景和灾害程度，供我国防台工作的参考。     

十四世纪以来我国地震次生水灾的研究

地震对于水利设施除直接造成堤防、堰坝等水工建筑物的破坏外,还可能形成堰塞湖,以及引发其他自然变异并形成水灾。在某些情况下,地震次生水灾所造成的损失比地震本身的损失还要大。本文在分析地震史料和重点现场查勘的基础上,将地震次生水灾从成因上和破坏机制上划分为六大类;提出了地震次生水灾的重点防范区;总结了地震次生水灾的特点;以及针对这些特点所应采取的减灾对策。     

再生铝生产过程中二噁英成因及全过程污染控制技术

介绍了再生铝生产工艺、二噁英生成机理,原物料铝渣中含有未完全破坏的PCDD/Fs和"熔炉"中形成的以及"从头合成(DeNovo)"二噁英形成的3种途径。有针对性地采用源头减污、过程控制及末端治理等全过程污染控制技术进行二噁英减排,从再生铝生产及治污工艺设备入手,提出再生铝二噁英污染控制最佳可行技术,为业内人士及环境管理部门二噁英控制与管理提供技术依据。     

Comparative investigation of coal- and oil-fired boilers based on emission factors, ozone and secondary organic aerosol formation potentials of VOCs

Volatile organic compounds(VOCs) are the important precursors of the tropospheric ozone(O_3) and secondary organic aerosols(SOA),both of which are known to harm human health and disrupt the earth's climate system.In this study,VOC emission factors,O_3 and SOA formation potentials were estimated for two types of industrial boilers:coal-fired boilers(n=3) and oil-fired boilers(n=3).Results showed that EVOCs concentrations were more than nine times higher for oil-fire d boilers compared to those for coal-fired boilers.Emission factors of ΣVOCs were found to be higher for oil-fired boilers(9.26-32.83 mg-VOC/kg) than for coal-fired boilers(1.57-4.13 mg-VOC/kg).Alkanes and aromatics were obtained as the most abundant groups in coal-fired boilers,while oxygenated organics and aromatics were the most contributing groups in oil-fired boilers.Benzene,n-hexane and o-ethyl toluene were the abundant VOC species in coal-fired boiler emissions,whereas toluene was the most abundant VOC species emitted from oil-fired boilers.O_3 and SOA formation potentials were found 12 and 18 times,respectively,higher for oil-fired than for coal-fired boilers.Total OFP ranged from 3.99 to 11.39 mg-O_3/kg for coal-fired boilers.For oil-fired boilers,total OFP ranged from 36.16 to 131.93 mg-O_3/kg.Moreover,total secondary organic aerosol potential(SOAP) ranged from 65.4 to 122.5 mg-SOA/kg and 779.9 to 2252.5 mg-SOA/kg for the coal-fired and oil-fired boilers,respectively.     

Chemical characteristics and source apportionment of PM2.5 between heavily polluted days and other days in Zhengzhou, China

PM_(2.5) samples were collected in Zhengzhou during 3 years of observation, and chemical characteristics and source contribution were analyzed. Approximately 96% of the daily PM_(2.5) concentrations and annual average values exceeded the Chinese National Ambient Air Quality Daily and Annual Standards, indicating serious PM_(2.5) pollution. The average concentration of water-soluble inorganic ions was 2.4 times higher in heavily polluted days(daily PM32.5 concentrations 250 μg/mand visibility 3 km) than that in other days, with sulfate, nitrate, and ammonium as major ions. According to the ratio of NO-3/SO2-4,stationary sources are still the dominant source of PM_(2.5) and vehicle emission could not be ignored. The ratio of secondary organic carbon to organic carbon indicated that photochemical reactivity in heavily polluted days was more intense than in other days.Crustal elements were the most abundant elements, accounting for more than 60% of 23 elements. Chemical Mass Balance results indicated that the contributions of major sources(i.e., nitrate, sulfate, biomass, carbon and refractory material, coal combustion, soil dust,vehicle, and industry) of PM_(2.5) were 13%, 16%, 12%, 2%, 14%, 8%, 7%, and 8% in heavily polluted days and 20%, 18%, 9%, 2%, 27%, 14%, 15%, and 9% in other days, respectively.Extensive combustion activities were the main sources of polycyclic aromatic hydrocarbons during the episode(Jan 1-9, 2015) and the total benzo[a]pyrene equivalency concentrations in heavily polluted days present significant health threat. Because of the effect of regional transport, the pollution level of PM_(2.5) in the study area was aggravated.     

Development of an on-line measurement system for water-soluble organic matter in PM2.5 and its application in China

Water-soluble organic matter(WSOM) represents a critical fraction of fine particles(PM_(2.5))in the air, but its changing behaviors and formation mechanisms are not well understood yet, partly due to the lack of fast techniques for the ambient measurements. In this study,a novel system for the on-line measurement of water-soluble components in PM_(2.5), the particle-into-liquid sampler(PILS)–Nebulizer–aerosol chemical speciation monitor(ACSM), was developed by combining a PILS, a nebulizer, and an ACSM. High time resolution concentrations of WSOM, sulfate, nitrate, ammonium, and chloride, as well as mass spectra, can be obtained with satisfied quality control results. The system was firstly applied in China for field measurement of WSOM. The mass spectrum of WSOM was found to resemble that of oxygenated organic aerosol, and WSOM agreed well with secondary inorganic ions. All evidence collected in the field campaign demonstrated that WSOM could be a good surrogate of secondary organic aerosol(SOA). The PILS–Nebulizer–ACSM system can thus be a useful tool for intensive study of WSOM and SOA in PM_(2.5).