Effect of NOx and SO2 on the photooxidation of methylglyoxal: Implications in secondary aerosol formation

Methylglyoxal(CH_3COCHO,MG),which is one of the most abundant α-dicarbonyl compounds in the atmosphere,has been reported as a major source of secondary organic aerosol(SOA).In this work,the reaction of MG with hydroxyl radicals was studied in a 500 L smog chamber at(293±3) K,atmospheric pressure,(18±2)% relative humidity,and under different NOx and SO_2.Particle size distribution was measured by using a scanning mobility particle sizer(SMPS) and the results showed that the addition of SO_2 can promote SOA formation,while different NOx concentrations have different influences on SOA production.High NOx suppressed the SOA formation,whereas the particle mass concentration,particle number concentration and particle geometric mean diameter increased with the increasing NOx concentration at low NOx concentration in the presence of SO_2.In addition,the products of the OH-initiated oxidation of MG and the functional groups of the particle phase in the MG/OH/SO_2 and MG/OH/NOx/SO_2 reaction systems were detected by gas chromatography mass spectrometry(GC-MS) and attenuated total reflection fourier transformed infrared spectroscopy(ATR-FTIR) analysis.Two products,glyoxylic acid and oxalic acid,were detected by GC-MS.The mechanism of the reaction of MG and OH radicals that follows two main pathways,H atom abstraction and hydration,is proposed.Evidence is provided for the formation of organic nitrates and organic sulfate in particle phase from IR spectra.Incorporation of NOx and SO_2 influence suggested that SOA formation from anthropogenic hydrocarbons may be more efficient in polluted environment.     

Potential of secondary aerosol formation from Chinese gasoline engine exhaust

Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds(VOCs). However,little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4–5 hr simulation, which was estimated to represent more than 10 days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol(SOA) production was 426 ± 85 mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China.     

南通市冬季PM2.5中水溶性离子污染特征

根据南通市2016和2017年冬季大气多参数站自动监测PM2.5数据和在线离子色谱分析仪Marga监测的PM2.5中水溶性离子数据,分析了南通市冬季PM2.5中水溶性离子污染特征。结果表明,南通市2016和2017年冬季,ρ(PM2.5)分别为58和54μg/m 3,均高出其年均值(14μg/m^3);ρ(水溶性离子)总占ρ(PM2.5)百分比分别为74.5%和74.3%;二次离子ρ(NO3^-、SO4^2-和NH4^+)占ρ(PM2.5)百分比分别为66.8%和66.6%;各水溶性离子占比大小依次为:NO3^-、SO4^2-、NH4^+、Cl^-、K^+、Na^+、Ca^2+、Mg^2+。对ρ(NO3^-)/ρ(SO 4^2-)分析表明,移动源已经成为南通市冬季的主要污染源,且呈逐年增强趋势。对氯氧化率和硫氧化率的分析表明,南通市冬季存在较明显的二次污染,SO2的转化程度大于NO2。除Na^+和Mg^2+外,其他离子与PM2.5均呈显著相关性,NO3^-、SO4^2-与NH4^+之间的相关系数最高,Cl^-与除Na^+外的所有阳离子均呈显著相关性。     

再论次生石英岩型非金属矿床

次生石英岩型非金属矿床明显受不同级别的火山构造控制,是中—酸性火山岩区一套很有特色的矿床组合;热源、水源、地层产状有机组合生成的环流热液是成矿的前提之一;成矿流体以重碳酸盐型、硫酸盐型为主,属中—低盐度热液;温度、pH值、fo_2等物理化学条件是矿床及矿种类刑的重要控制因素。本文在《次生石英岩容矿型非金属矿床系列的矿种、组合及其成矿作用特征》(1986)一文基础上,进一步总结这类矿床的成矿机理和地质地球化学模式。     

Characteristics and source apportionment of PM2.5 under the dual influence of the Spring Festival and the COVID-19 pandemic in Yuncheng city

Based on the online and membrane sampling data of Yuncheng from January 1st to February 12th, 2020, the formation mechanism of haze under the dual influence of Spring Festival and COVID-19 (Corona Virus Disease) was analyzed. Atmospheric capacity, chemical composition, secondary transformation, source apportionment, backward trajectory, pollution space and enterprise distribution were studied. Low wind speed, high humidity and small atmospheric capacity inhibited the diffusion of air pollutants. Four severe pollution processes occurred during the period, and the pollution degree was the highest around the Spring Festival. In light, medium and heavy pollution periods, the proportion of SNA (SO₄²⁻, NO₃⁻ and NH₄⁺) was 59.6%, 56.0% and 54.9%, respectively, which was the largest components of PM_2.5; the [NO₃⁻]/[SO₄²⁻] ratio was 2.1, 1.5 and 1.7, respectively, indicating that coal source had a great influence; the changes of NOR (nitrogen oxidation ratio, 0.44, 0.45, 0.61) and SOR (sulphur oxidation ratio, 0.40, 0.49, 0.65) indicated the accumulation of secondary aerosols with increasing pollution. The coal combustion, motor vehicle, secondary inorganic sources and industrial sources contributed 36.8%, 26.59%, 11.84% and 8.02% to PM_2.5 masses, respectively. Backward trajectory showed that the influence from the east was greater during the Spring Festival, and the pollutants from the eastern air mass were higher, which would aggravate the pollution. Meteorological and Spring Festival had a great impact on heavy pollution weather. Although some work could not operate due to the impact of the COVID-19 epidemic, the emission of pollutants did not reduce much.     

电厂锅炉清洗废水治理工艺

电厂锅炉清洗废水中，含有高浓度的柠檬酸和丙酮肟等有机污染物。经试验，采取原水作适当稀释后，进行好氧曝气－活性炭生物膜法二级处理，ＣＯＤｃｒ总去除率可达８８％－９０％；ＢＯＤ５去除率为９０％。经两经处理后的出水，ＣＯＤｃｒ＜１００ｍｇ／ｌ，ＢＯＤ５＜５０ｍｇ／ｌ，可达到较好的处理效果。     

原子吸收火焰法次灵敏线测定污水和电镀污泥中高含量的锌

对采用原子吸收火焰法次灵敏线测定污水和电镀污泥中高含量的锌进行了研究。试验结果表明：在锌浓度50．0～600．0mg/L之间,溶液锌含量与吸光度呈线性关系。线性回归方程为y＝0．000661x-0．0007,相关系数γ＝0．9998。方法检出限为25．0mg/L,相对标准误差（RSD）＜2．96％,加标回收率为92．5％～105％,与标准法的相对误差＜2．76％。     

搅拌-序批式活性污泥反应器(WSBR)中好氧颗粒污泥的特性研究

为研究搅拌-序批式活性污泥反应器(WSBR)中好氧颗粒污泥的特性,利用WSBR反应器与传统SBR反应器对好氧活性污泥颗粒化的过程进行了比较.结果表明,在添加同量的聚炳烯酰胺(PAM)条件下,具有合理二次流场的WSBR反应器在4d就可见好氧颗粒污泥,而SBR反应器则在第10d才出现好氧颗粒污泥,且WSBR反应器中好氧颗粒...     

Secondary arsenic minerals in the environment: A review

Information on arsenic (As) speciation in solid materials is critical for many environmental studies concerned with As stability and/or mobility in natural As-impacted soils and mining or industrial sites contaminated by As. The investigation of these systems has provided evidence for a number of secondary As minerals that have often played a significant role in As mobility in the solid phase–water system. This paper presents a list of environmentally important secondary As minerals in contaminated soil and waste systems, summarizes the information about their origin, occurrence, environmental stability and thermodynamics, and proposes several important avenues for further investigation.     

Evaluation of the temporal variations of air quality in Taipei City, Taiwan, from 1994 to 2003

Data collected from the five air-quality monitoring stations established by the Taiwan Environmental Protection Administration in Taipei City from 1994 to 2003 are analyzed to assess the temporal variations of air quality. Principal component analysis (PCA) is adopted to convert the original measuring pollutants into fewer independent components through linear combinations while still retaining the majority of the variance of the original data set. Two principal components (PCs) are retained together explaining 82.73% of the total variance. PC1, which represents primary pollutants such as CO, NO(x), and SO(2), shows an obvious decrease over the last 10 years. PC2, which represents secondary pollutants such as ozone, displays a yearly increase over the time period when a reduction of primary pollutants is obvious. In order to track down the control measures put forth by the authorities, 47 days of high PM(10) concentrations caused by transboundary transport have been eliminated in analyzing the long-term trend of PM(10) in Taipei City. The temporal variations over the past 10 years show that the moderate peak in O(3) demonstrates a significant upward trend even when the local primary pollutants have been well under control. Monthly variations of PC scores demonstrate that primary pollution is significant from January to April, while ozone increases from April to August. The results of the yearly variations of PC scores show that PM(10) has gradually shifted from a strong correlation with PC1 during the early years to become more related to PC2 in recent years. This implies that after a reduction of primary pollutants, the proportion of secondary aerosols in PM(10) may increase. Thus, reducing the precursor concentrations of secondary aerosols will be an effective way to lower PM(10) concentrations.