Why are sulfates in the Beijing smog? Researchers reveal the mystery of form-smog, nitrate-IT information
21st German researchers say they cracked the Beijing smog in North China and the most important component of sulfate formation puzzle found in moisture adsorption of fine particles in the atmosphere nitrogen dioxide and sulfur dioxide during the chemical reaction is the current haze of sulfate the main path . This discovery highlights the continued implementation of the measures to reduce emissions while giving priority to efforts to increase nitrogen oxide emissions on the importance of alleviating air pollution. In recent years, Beijing and North China haze frequently. Studies have show that sulfate is the primary driver of heavy fouling.
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In absolute contribution, heavy pollution during sulfate in ambient fine particulate PM2.5 mass of up to 20% per cent, is the highest proportion of a unit; in terms of relative trends, as PM2.5 pollution levels rise, and sulfate relative weight the fastest rising component of PM2.5. Therefore, sources of sulfate is a key scientific issues explain the formation of smog.
Tsinghua University He Kebin academician, and Zhang Qiang Professor, and Zheng Guangjie Dr and Germany mark Republika ? General lang grams Chemical Institute of Cheng Yafang Professor, and Ulrich ? Cooper driescher Professor, and Jervois Professor, people day in new a period United States science progress magazine Shang report said, they using outfield observation, and model simulation and the theory calculation, means found, in Beijing and the North fog haze during, sulfate main is by sulfur dioxide and nitrogen dioxide dissolved Yu air in the of "particles real combined water", Characteristic-neutral environment in North China reacted quickly. Mean PM2.5 particulate matter combined with water in hygroscopic moisture absorption of high relative humidity environment.
The conclusion and sulfate formation mechanism of thought vary greatly. Existing based on Europe, area of classic atmosphere chemical theory think, sulfate main is in cloud water environment in the formed, due to cloud in the of liquid water content far above particles real combined water, usually high out 1000 to 100,000 times times, so and cloud water in the of sulfate generated reaction compared, particles real combined water in the of reaction can ignored ; theory calculation also displayed, in cloud water reaction path in the, nitrogen dioxide oxidation II oxidation sulfur generated sulfate this a path of contribution also can ignored regardless of.
And in Beijing and the North fog haze during, while, due to particles real concentration sharply rose and the static stability meteorological conditions Xia relative humidity high, reasons, particles real combined water content far above classic stories, particles real combined water in the of reaction total greatly upgrade; on the, heavy degrees fog haze during nitrogen dioxide concentration for classic cloud water stories Xia of 50 times times above, this directly change has nitrogen dioxide oxidation path of relative importance. In addition, Beijing and North China there are a lot of ammonia, alkaline substance such as mineral dust particles on the ground combined with the pH value of the water much higher than the United States and other places, showing characteristic-neutral environment, nitrogen dioxide oxidation mechanism of reaction rate will increase with the pH value rises.
Researchers pointed out that in the paper, giving priority to reduce nitrogen oxide emissions may help to significantly reduce the levels of sulfate pollution in smog.
"This study shows that special compound pollution in China," said academician He Kebin told Xinhua, "high sulphur dioxide comes mainly from coal-fired power plants, high nitrogen dioxide mainly from power plants and motor vehicles, and alkaline substances and ammonia, mineral dust from agricultural, industrial pollution, dust, and other sources. These various sources of pollution in China with high intensity discharge, lead sulfate to unique chemical path to rapidly generate, which is particulate matter concentration increased rapidly during the severe smog is one of the main reasons. ”
Acid fog in London is often considered by the coal-fired emissions of soot and sulfur dioxide and other pollutants. Los Angeles smog a photochemical pollution, mainly due to vehicle exhaust gas reacts in the presence of sunlight to form secondary pollutants. China's smog is a mix of primary and secondary pollutants cause.
He Kebin said characteristics of the compound pollution shows the importance of collaborative emission of pollutants, especially at this stage should give priority to efforts to increase nitrogen oxide emissions. "Although we know emissions before, but if you can't figure out critical chemical mechanism of heavy haze pollution, effective model of quantitative analysis cannot, will not be able to accurately assess how best reduce emissions, most scientific. Unscientific emission reductions could lead to serious consequences, may spend a lot of manpower and resources, but to little avail. ”
Original title generation mechanism of sulfate in the studies revealed Beijing smog suggests an increase of nitrogen oxide emissions, IT edit modify, as necessary, of information.
北京雾霾中为何有硫酸盐？科研人员揭示形成之谜 - 雾霾,硝酸盐 - IT资讯
中德两国研究人员21日说，他们破解了北京及华北地区雾霾最主要组分硫酸盐的形成之谜，发现在大气细颗粒物吸附的水分中二氧化氮与二氧化硫的化学反应是当前雾霾期间硫酸盐的主要生成路径。这一发现凸显在继续实施减排措施的同时优先加大氮氧化物减排力度对缓解空气污染问题的重要性。近年来，北京及华北地区雾霾频发。已有研究表明，硫酸盐是重污染形成的主要驱动因素。
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在绝对贡献上，重污染期间硫酸盐在大气细颗粒物PM2.5中的质量占比可达20%，是占比最高的单体；在相对趋势上，随着PM2.5污染程度上升，硫酸盐是PM2.5中相对比重上升最快的成分。因此，硫酸盐的来源研究是解释雾霾形成的关键科学问题。
清华大学贺克斌院士、张强教授、郑光洁博士和德国马克斯·普朗克化学研究所的程雅芳教授、乌尔里希·珀施尔教授、苏杭教授等人当天在新一期美国《科学进展》杂志上报告说，他们运用外场观测、模型模拟及理论计算等手段发现，在北京及华北地区雾霾期间，硫酸盐主要是由二氧化硫和二氧化氮溶于空气中的“颗粒物结合水”，在中国北方地区特有的偏中性环境下迅速反应生成。颗粒物结合水是指PM2.5在相对湿度较高的环境下潮解所吸附的水分。
该结论与通常认为的硫酸盐形成机制有较大不同。现有基于欧美等地区的经典大气化学理论认为，硫酸盐主要是在云水环境中形成，由于云中的液态水含量远高于颗粒物结合水，通常高出1000到10万倍，所以与云水中的硫酸盐生成反应相比，颗粒物结合水中的反应可以忽略；理论计算还显示，在云水反应路径中，二氧化氮氧化二氧化硫生成硫酸盐这一路径的贡献也可忽略不计。
而在北京及华北地区雾霾期间，一方面，由于颗粒物浓度大幅上升及静稳气象条件下相对湿度较高等原因，颗粒物结合水含量远高于经典情景，颗粒物结合水中的反应总量大大提升；另一方面，重度雾霾期间二氧化氮浓度为经典云水情景下的50倍以上，这直接改变了二氧化氮氧化路径的相对重要性。此外，北京及华北地区大量存在的氨、矿物粉尘等碱性物质使得当地颗粒物结合水的pH值远高于美国等地，呈现出特有的偏中性环境，而二氧化氮氧化机制的反应速率会随pH值上升而大幅提高。
研究人员据此在论文中指出，优先降低氮氧化物的排放可能有助大幅降低中国雾霾中的硫酸盐污染水平。
“该研究表明中国复合型污染的特殊性，”贺克斌院士对新华社记者说，“高二氧化硫主要来自燃煤电厂，高二氧化氮主要来自电厂和机动车等，而起到中和作用的碱性物质氨、矿物粉尘等则来自农业、工业污染、扬尘等其他来源。这些不同的污染源在中国同时以高强度排放，导致硫酸盐以特有的化学生成路径迅速生成，这也是重度雾霾期间颗粒物浓度迅速增长的主要原因之一。”
伦敦酸雾通常被认为是由燃煤排放的烟尘以及二氧化硫等一次污染物所致。洛杉矶雾霾则是一种光化学污染，主要原因是机动车尾气在阳光作用下反应生成了二次污染物。而中国雾霾是一次与二次污染物混合造成。
贺克斌说，这种复合型污染的特殊性更加表明了多污染物协同减排的重要性，尤其是现阶段应优先加大氮氧化物减排力度。“之前我们虽然知道需要减排，但是如果无法弄清重霾污染形成的关键化学机制，就无法进行有效的模型定量模拟分析，也就无法准确评估如何减排最有效、最科学。不科学减排可能导致严重后果，可能花了很多人力物力，但收效甚微。”
原标题《研究揭示北京雾霾中硫酸盐生成机制建议加大氮氧化物减排》，IT资讯编辑酌情修改。