Water-soluble matter in PM2.5 in a coastal city over China: Chemical components, optical properties, and source analysis

Although marine and terrestrial emissions simultaneously affect the formation of atmospheric fine particles in coastal areas, knowledge on the optical properties and sources of water-soluble matter in these areas is still scarce. In this work, taking Qingdao, China as a typical coastal location, the chemical composition of PM_2.5 during winter 2019 was analyzed. Excitation-emission matrix fluorescence spectroscopy was combined with parallel factor analysis model to explain the components of water-soluble atmospheric chromophores of PM_2.5. Our analysis indicated that NO₃⁻, NH₄⁺ and SO₄²⁻ ions accounted for 86.80% of the total ion mass, dominated by NO₃⁻. The ratio of [NO₃⁻]/[SO₄²⁻] was up to 2.42 ± 0.84, suggesting that mobile sources play an important role in local pollutants emission. The result of positive correlation between Abs₃₆₅ with K⁺ suggests that biomass burning is an important source of water-soluble organic compounds (WSOC). Six types of fluorophores (C1-C6), all humic-like substances, were identified in WSOC. Humification index, biological index and fluorescence index in winter were 1.66 ± 0.34, 0.51 ± 0.44 and 1.09 ± 0.78, respectively, indicating that WSOC in Qingdao were mainly terrestrial organic matters. Overall, although the study area is close to the ocean, the contribution of terrestrial sources to PM_2.5, especially vehicle exhaust and coal combustion, is still much higher than that of marine sources. Our study provides a more comprehensive understanding of chemical and optical properties of WSOC based on PM_2.5 in coastal areas, and may provide ground for improving local air quality.     

Chemical characterization and source identification of PM2.5 in Luoyang after the clean air actions

Luoyang is a typical heavy industrial city in China, with a coal-dominated energy structure and serious air pollution. Following the implementation of the clean air actions, the physicochemical characteristics and sources of PM_2.5 have changed. A comprehensive study of PM_2.5 was conducted from October 16, 2019 to January 23, 2020 to evaluate the effectiveness of previous control measures and further to provide theory basis for more effective policies in the future. Results showed that the aerosol pollution in Luoyang in autumn and winter is still serious with the average concentration of 91.1 μg/m³, although a large reduction (46.9%) since 2014. With the contribution of nitrate increased from 12.5% to 25.1% and sulfate decreased from 16.7% to 11.2%, aerosol pollution has changed from sulfate-dominate to nitrate-dominate. High NO₃⁻/SO₄²⁻ ratio and the increasing of NO₃⁻/SO₄²⁻ ratio with the aggravation of pollution indicating vehicle exhaust playing an increasingly important role in PM_2.5 pollution in Luoyang, especially in the haze processes. Secondary inorganic ions contributed significantly to the enhancement of PM_2.5 during the pollution period. The high value of Cl⁻/Na⁺ and EC concentration indicate coal combustion in Luoyang is still serious. The top three contributor sources were secondary inorganic aerosols (33.3%), coal combustion (13.6%), and industrial emissions (13.4%). Close-range transport from the western and northeastern directions were more important factors in air pollution in Luoyang during the sampling period. It is necessary to strengthen the control of coal combustion and reduce vehicle emissions in future policies.     

Assessing microbial and chemical exposure risks of Giardia in indoor swimming pool water disinfected by chlorine

Swimming pools adopt chlorination to ensure microbial safety. Giardia has attracted attention in swimming pool water because of its occurrence, pathogenicity, and chlorine resistance. To control Giardia concentrations in pool water and reduce the microbial risk, higher chlorine doses are required during disinfection. Unfortunately, this process produces carcinogenic disinfection byproducts that increase the risk of chemical exposure. Therefore, quantitatively evaluating the comparative microbial vs. chemical exposure risks that stem from chlorination inactivation of Giardia in swimming pool water is an issue that demands attention. We simulated an indoor swimming pool disinfection scenario that followed common real-world disinfection practices. A quantitative microbial risk assessment coupled with a chemical exposure risk assessment was employed to compare the Giardia microbial exposure risk (MER) and the trihalomethane chemical exposure risk (CER) to humans. The results demonstrated a 22% decrease in MER- and CER-induced health exposure risk, from 8.45E-5 at 8:00 to 6.60E-5 at 19:00. Both the MER and CER decreased gradually, dropping to 3.26E-5 and 3.35E-5 at 19:00, respectively. However, the CER exceeded the MER after 18:30 and became the dominant factor affecting the total exposure risk. Past the 18 hr mark, the contribution of trihalomethane CER far exceeded the risk aversion from microbial inactivation, leading to a net increase in total exposure risk despite the declining MER. Swimmers may consider swimming after 19:00, when the total exposure risk is the lowest. Lowering water temperature and/or pH were identified as the most sensitive factors to minimize the overall health exposure risk.     

Ozone episodes during and after the 2018 Chinese National Day holidays in Guangzhou: Implications for the control of precursor VOCs

The impact of reducing industrial emissions of volatile organic compounds (VOCs) on ozone (O₃) pollution is of wide concern particularly in highly industrialized megacities. In this study, O₃, nitrogen oxides (NOx) and VOCs were measured at an urban site in the Pearl River Delta region during the 2018 Chinese National Day Holidays and two after-holiday periods (one with ozone pollution and another without). O₃ pollution occurred throughout the 7-day holidays even industrial emissions of VOCs were passively reduced due to temporary factory shutdowns, and the toluene to benzene ratios dropped from ∼10 during non-holidays to ∼5 during the holidays. Box model (AtChem2-MCM) simulations with the input of observation data revealed that O₃ formation was all VOC-limited, and alkenes had the highest relative incremental reactivity (RIR) during the holiday and non-holiday O₃ episodes while aromatics had the highest RIR during the non-pollution period. Box model also demonstrated that even aromatics decreased proportionally to levels with near-zero contributions of industrial aromatic solvents, O₃ concentrations would only decrease by less than 20% during the holiday and non-holiday O₃ episodes and ozone pollution in the periods could not be eliminated. The results imply that controlling emissions of industrial aromatic solvents might be not enough to eliminate O₃ pollution in the region, and more attention should be paid to anthropogenic reactive alkenes. Isoprene and formaldehyde were among the top 3 species by RIRs in all the three pollution and non-pollution periods, suggesting substantial contribution to O₃ formation from biogenic VOCs.     

低铬油套管钢材在不同工况下的腐蚀规律研究

目的 研究低铬油套管钢材在不同腐蚀环境中的腐蚀特征。方法 采用高温高压动态反应釜对1Cr、3Cr这2种常用低铬油套管钢材进行纯CO2、CO2和低浓度H2S共存条件下的腐蚀试验。结果 温度在40~80 ℃条件下,各种钢材的腐蚀速率随着温度的升高而变大。加入低浓度H2S后,可以抑制CO2腐蚀,且随着温度升高,抑制性逐渐减弱。分析认为,在单独CO2环境以及CO2和低浓度H2S共存的环境中,1Cr、3Cr钢表面出现铬富集现象,形成的Cr(OH)3膜保护基底。同时,在CO2和低浓度H2S共存的环境中,1Cr、3Cr钢表面形成致密的FeS产物膜有助于保护基底,抵抗Cl^－侵蚀。结论 低Cr钢表面因铬的富集形成钝化膜,能有效抑制油套管的腐蚀速率,以上研究成果对CO2和低浓度H2S环境中的腐蚀理论以及油田油套管材料合理选择均有一定指导意义。     

Toxicity of the nerve agent tabun to Daphnia magna, a new experimental species in military toxicology

Daphnia magna, a freshwater microcrustacean, is currently tested as an alternative experimental species in research dealing with nerve agents poisonings treatment. Because of this, the toxicity of the nerve agent tabun (a cyanide-group containing organophosphate) to Daphnia had to be examined by estimating the EC₅₀ values. The immobilization of daphnids was chosen as the end-point. It was found that D. magna is sensitive to small amounts of tabun, even after 15 min exposure, and tabun toxicity increases with time. The estimated EC₅₀ values for 15, 30, 45, and 60 min exposure were as follows: 67.39, 38.10, 26.95, and 21.9 μg l^-1. In addition, the toxicity of media to which tabun was added 24 h before the start of experiments was examined. The results obtained indicate that daphnids can be used in experiments with nerve-agent intoxication treatment.     

超声波/零价铁协同体系作用机理探讨

在超声波/零价铁协同体系中,探讨了OH.的产生途径及其影响因素,并分析了Fe0表面形态变化。结果表明:在超声波/零价铁体系中,羟基自由基的产生途径主要有四种:声空化导致水分子热解、Fenton反应、超声波与类Fenton反应的复合效应、铁粉颗粒效应;pH值过低或过高都不利于羟基自由基产生;当铁粉投加量为2.0g/L时最有利于羟基自由基产生;超声波通过冲刷、碎裂、清洗、气蚀和熔合等多种效应,活化和增强铁粉的表面性能。     

宁东基地大气PAHs污染特征及呼吸暴露风险

利用主动观测技术对宁东能源化工基地大气PM_2.5、PM_1.0和气相中的PAHs浓度水平、族谱特征、时空分布及来源进行研究,并基于该观测数据对居民呼吸暴露健康风险进行评估.结果表明,宁东基地大气PM_2.5、PM_1.0及气相中∑₁₆PAHs浓度范围分别为：17.95~325.12ng/m³、12.66~311.96ng/m³和26.33~97.88ng/m³,年均浓度分别为（99.42±117.48）ng/m³、（78.88±100.58）ng/m³和（57.89±47.39）ng/m³.宝丰基地冬夏季大气PM_2.5、PM_1.0和气相中∑₁₆PAHs浓度水平均明显高于英力特;宝丰和英力特基地冬季大气PM_2.5、PM_1.0中∑₁₆PAHs浓度水平均明显高于夏季浓度.宁东基地大气中∑₁₆PAHs的浓度水平要高于国内外其他城市,大气PAHs污染较为严重.源解析表明夏季宁东基地PAHs的主要排放源是工业煤燃烧和机动车尾气,冬季则主要来自工业煤燃烧和木材、薪柴等生物质燃烧排放.宁东基地人群暴露于大气PAHs可能会造成平均冬季每百万人中约有33~2628人罹患癌症,夏季每百万人中约有11~834人罹患癌症的风险.     

Effect of manganese oxide-modified biochar addition on methane production and heavy metal speciation during the anaerobic digestion of sewage sludge

Low organic matter content and high heavy metal levels severely inhibit the anaerobic digestion (AD) of sewage sludge. In this study, the effect of added manganese oxide-modified biochar composite (MBC) on methane production and heavy metal fractionation during sewage sludge AD was examined. The MBC could increase the buffering capacity, enhance the methane production and degradation of intermediate acids, buffer the pH of the culture, and stabilize the sewage sludge AD process. The application of MBC positively impacted methane production and the cumulative methane yield increased up to 121.97%, as compared with the control. The MBC addition can improve metal stabilization in the digestate. An optimum MBC dose of 2.36?g was recommended, which would produce up to 121.1?L/kg volatile solids of methane. After the AD process, even though most of the metals accumulated in the residual solids, they could be transformation from the bio-available fractions to a more stable fraction. The total organic- and sulfide-bound and residual fraction content at a 3?g dose of MBC that is 0.12?g/g dry matter were 51.06% and 35.11% higher than the control, respectively. The results indicated that the application of MBC could improve the performance of AD and promote stabilization of heavy metals in sewage sludge post the AD process.