利用次溴酸盐氧化结合盐酸羟胺还原法测定大气气溶胶样品铵态氮同位素
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摘要
硝酸铵、硫酸铵和硫酸氢铵等铵盐作为PM_(2.5)中主要的二次无机气溶胶污染物,在灰霾形成过程中发挥了重要作用.关于其来源及转化过程的研究备受关注.本文在前人研究基础上,基于稳定同位素分析技术改进了样品进样量,增加了调节浸提液pH的步骤,给出了一种能够快速、准确测量大气样品中铵态氮同位素的化学转化方法.即向含有0.25μg·mL~(-1)铵态氮的4 mL大气气溶胶滤膜样品浸提液中加入碱性次溴酸盐溶液,使铵盐(NH_4~+)氧化为亚硝酸盐(NO_2~-);然后通过调节pH值,在pH<0.3的条件下,使用盐酸羟胺将亚硝酸盐(NO_2~-)还原为氧化亚氮气体(N_2O),最终通过Precon-GasBench-IRMS系统的连用实现大气气溶胶样品中的铵态氮同位素的测定.该方法所需进样含量低,避免了剧毒易制爆试剂的使用,重复测试精确度可达到0.2‰(n=10).通过调节大气气溶胶滤膜样品浸提液的pH可提高还原效率(约100%).测量精确度和准确度满足了大气气溶胶中颗粒态铵的测定,有助于进一步开展大气铵盐的来源、化学转化过程、传输沉降等研究.
Ammonium salts, including ammonium nitrate, ammonium sulfate and ammonium hydrogen sulfate, are the main components of secondary inorganic aerosols and play an important role in the formation of haze events. The sources and transformation processes of atmospheric ammonium have received more and more attention. In this study, we modified the previous stable isotope analysis technique by improving the injection volume and adding a pH adjustment step, which gave a rapid and accurate measurement of ammonium nitrogen isotope ratio in atmospheric aerosol samples. Firstly, we added alkaline hypobromite to the extracted solution of the atmospheric aerosol filter samples(0.25 μg·mL~(-1) ammonium nitrogen in 4 mL) to oxidize ammonium(NH_4~+) to nitrite(NO_2~-). Then, after adjusting the pH, nitrite(NO_2~-) was reduced to nitrous oxide(N_2O) by hydroxylamine hydrochloride under pH <0.3. Finally, nitrous oxide(N_2O) was analyzed by Precon-GasBench-IRMS system to measure ammonium nitrogen isotope ratio. Our approach required low amount of NH_4~+ and avoided the use of highly toxic and explosive reagents. Meanwhile, the precision of our method could reach as high as 0.2‰(n=10). This method could increase the NH_4~+ reduction efficiency to 100% at a condition of pH <0.3 and satisfy the demands of precision and accuracy for determination of ammonium nitrogen isotope in atmospheric aerosol samples. This method would help us better understand the sources, evolutions, chemical and deposition processes of atmospheric ammonium.
Ammonium salts, including ammonium nitrate, ammonium sulfate and ammonium hydrogen sulfate, are the main components of secondary inorganic aerosols and play an important role in the formation of haze events. The sources and transformation processes of atmospheric ammonium have received more and more attention. In this study, we modified the previous stable isotope analysis technique by improving the injection volume and adding a pH adjustment step, which gave a rapid and accurate measurement of ammonium nitrogen isotope ratio in atmospheric aerosol samples. Firstly, we added alkaline hypobromite to the extracted solution of the atmospheric aerosol filter samples(0.25 μg·mL~(-1) ammonium nitrogen in 4 mL) to oxidize ammonium(NH_4~+) to nitrite(NO_2~-). Then, after adjusting the pH, nitrite(NO_2~-) was reduced to nitrous oxide(N_2O) by hydroxylamine hydrochloride under pH <0.3. Finally, nitrous oxide(N_2O) was analyzed by Precon-GasBench-IRMS system to measure ammonium nitrogen isotope ratio. Our approach required low amount of NH_4~+ and avoided the use of highly toxic and explosive reagents. Meanwhile, the precision of our method could reach as high as 0.2‰(n=10). This method could increase the NH_4~+ reduction efficiency to 100% at a condition of pH <0.3 and satisfy the demands of precision and accuracy for determination of ammonium nitrogen isotope in atmospheric aerosol samples. This method would help us better understand the sources, evolutions, chemical and deposition processes of atmospheric ammonium.
引文
[1] Wu D (吴兑),Wu X-J (吴晓京),Li F (李菲),et al.Temporal and spatial variation of haze during 1951-2005 in Chinese mainland.Acta Meteorologica Sinica (气象学报),2010,68(5):680-688 (in Chinese)
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[3] Intergovernmental Panel on Climate Change (IPCC).Climate Change 2007:The Physical Science Basis.Cambridge:Cambridge University Press,2007
[4] Guo X-B (郭新彪),Wei H-Y (魏红英).Progress on the health effects of ambient PM2.5 pollution.Chinese Science Bulletin (科学通报),2013,58(13):1171-1177 (in Chinese)
[5] Griffith SM,Huang XHH,Louie PKK,et al.Characteri-zing the thermodynamic and chemical composition factors controlling PM2.5,nitrate:Insights gained from two years of online measurements in Hong Kong.Atmospheric Environment,2015,122:864-875
[6] Wei L-F (韦莲芳),Yang F-M (杨复沫),Tan J-H (谭吉华),et al.Research progress on aerosol extinction properties.Environmental Chemistry (环境化学),2014,33(5):705-715 (in Chinese)
[7] Felix JD,Elliott EM,Gish TJ,et al.Characterizing the isotopic composition of atmospheric ammonia emission sources using passive samplers and a combined oxidation-bacterial denitrifier approach.Rapid Communications in Mass Spectrometry,2013,27:2239-2246
[8] Wen T (温腾),Cao Y-C (曹亚澄),Zhang P-Y (张珮仪),et al.On progress in use of micro-diffusion method in δ15N-NH4+ and δ15N-NO3- measurements.Soils (土壤),2016,48(4):634-640 (in Chinese)
[9] Liu D-W (刘冬伟),Tu Y (图影),Fang Y-T (方运霆).Isotope analysis of ammonium and nitrate:A review on measured methods and their application.Chinese Journal of Applied Ecology (应用生态学报),2017,28(7):2353-2360 (in Chinese)
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[12] Xiao H,Liu C.A fast method to prepare water samples for 15N analysis.Science in China,2001,44:105-107
[13] Xiao H-Y (肖化云),Liu C-Q (刘丛强).Discussion on a method for preparation nitrate in water samples for δ15N analysis.Rock and Mineral Analysis (岩矿测试),2002,21(2):105-108 (in Chinese)
[14] Zeng M (曾明),Yu L-F (余龙飞),Zhang Y (张逸),et al.Determination of δ15N of ammonium and nitrate in nature waters.Environmental Chemistry (环境化学),2013,32(8):1486-1490 (in Chinese)
[15] Hu J (胡婧),Liu W-G (刘卫国).Determination of nitrogen isotope of water samples with low ammonium nitrogen by ion exchange method.Rock and Mineral Analysis (岩矿测试),2013,32(3):495-501 (in Chinese)
[16] Zhang L,Altabet MA,Wu T,et al.Sensitive measurement of NH4+ 15N/14N (δ15NH4+) at natural abundance levels in fresh and salt waters.Analytical Chemistry,2007,79:5297-5303
[17] Liu D,Fang Y,Tu Y,et al.Chemical method for nitrogen isotopic analysis of ammonium at natural abundance.Analytical Chemistry,2014,86:3787-3792
[18] Li Q-K (李亲凯),Yang Z (杨周),Huang J (黄俊),et al.A review of stable isotopic compositions of atmospheric particulate matter.Chinese Journal of Ecology (生态学杂志),2016,35(4):1063-1071 (in Chinese)
[19] Bothner-By A,Friedman L.The reaction of nitrous acid with hydroxylamine.Journal of Chemical Physics,1952,20:459-462
[20] Wang X (王曦),Cao Y-C (曹亚澄),Han Y (韩勇),et al.Determination of nitrogen and oxygen isotope ratio of nitrate in water with a chemical conversion method.Acta Pedologica Sinica (土壤学报),2015,52(3):558-566 (in Chinese)
[21] Pan Y,Tian S,Liu D,et al.Fossil fuel combustion-related emissions dominate atmospheric ammonia sources during severe haze episodes:Evidence from 15N-stable isotope in size-resolved aerosol ammonium.Environmental Science and Technology,2016,50:8049,doi:10.1021/acs.est.6b00634
[22] Pan Y,Tian S,Liu D,et al.Isotopic evidence for enhanced fossil fuel sources of aerosol ammonium in the urban atmosphere.Environmental Pollution,2018,238:942-947
[23] Park YM,Park KS,Kim H,et al.Characterizing isotopic compositions of TC-C,NO3--N,and NH4+-N in PM2.5 in South Korea:Impact of China’s winter heating.Environmental Pollution,2018,233:735-744
[2] Zhang XY,Wang YQ,Niu T,et al.Atmospheric aerosol compositions in China:Spatial/temporal variability,chemical signature,regional haze distribution and comparisons with global aerosols.Atmospheric Chemistry and Physics,2012,12:779-799
[3] Intergovernmental Panel on Climate Change (IPCC).Climate Change 2007:The Physical Science Basis.Cambridge:Cambridge University Press,2007
[4] Guo X-B (郭新彪),Wei H-Y (魏红英).Progress on the health effects of ambient PM2.5 pollution.Chinese Science Bulletin (科学通报),2013,58(13):1171-1177 (in Chinese)
[5] Griffith SM,Huang XHH,Louie PKK,et al.Characteri-zing the thermodynamic and chemical composition factors controlling PM2.5,nitrate:Insights gained from two years of online measurements in Hong Kong.Atmospheric Environment,2015,122:864-875
[6] Wei L-F (韦莲芳),Yang F-M (杨复沫),Tan J-H (谭吉华),et al.Research progress on aerosol extinction properties.Environmental Chemistry (环境化学),2014,33(5):705-715 (in Chinese)
[7] Felix JD,Elliott EM,Gish TJ,et al.Characterizing the isotopic composition of atmospheric ammonia emission sources using passive samplers and a combined oxidation-bacterial denitrifier approach.Rapid Communications in Mass Spectrometry,2013,27:2239-2246
[8] Wen T (温腾),Cao Y-C (曹亚澄),Zhang P-Y (张珮仪),et al.On progress in use of micro-diffusion method in δ15N-NH4+ and δ15N-NO3- measurements.Soils (土壤),2016,48(4):634-640 (in Chinese)
[9] Liu D-W (刘冬伟),Tu Y (图影),Fang Y-T (方运霆).Isotope analysis of ammonium and nitrate:A review on measured methods and their application.Chinese Journal of Applied Ecology (应用生态学报),2017,28(7):2353-2360 (in Chinese)
[10] Velinsky DJ,Pennock JR,Sharp JH,et al.Determination of the isotopic composition of ammonium-nitrogen at the natural abundance level from estuarine waters.Marine Chemistry,1989,26:351-361
[11] Holmes RM,McClelland JW,Sigman DM,et al.Mea-suring 15N-NH4+ in marine,estuarine and fresh waters:An adaption of the ammonia diffusion method for samples with low ammonium concentrations.Marine Chemistry,1998,60:235-243
[12] Xiao H,Liu C.A fast method to prepare water samples for 15N analysis.Science in China,2001,44:105-107
[13] Xiao H-Y (肖化云),Liu C-Q (刘丛强).Discussion on a method for preparation nitrate in water samples for δ15N analysis.Rock and Mineral Analysis (岩矿测试),2002,21(2):105-108 (in Chinese)
[14] Zeng M (曾明),Yu L-F (余龙飞),Zhang Y (张逸),et al.Determination of δ15N of ammonium and nitrate in nature waters.Environmental Chemistry (环境化学),2013,32(8):1486-1490 (in Chinese)
[15] Hu J (胡婧),Liu W-G (刘卫国).Determination of nitrogen isotope of water samples with low ammonium nitrogen by ion exchange method.Rock and Mineral Analysis (岩矿测试),2013,32(3):495-501 (in Chinese)
[16] Zhang L,Altabet MA,Wu T,et al.Sensitive measurement of NH4+ 15N/14N (δ15NH4+) at natural abundance levels in fresh and salt waters.Analytical Chemistry,2007,79:5297-5303
[17] Liu D,Fang Y,Tu Y,et al.Chemical method for nitrogen isotopic analysis of ammonium at natural abundance.Analytical Chemistry,2014,86:3787-3792
[18] Li Q-K (李亲凯),Yang Z (杨周),Huang J (黄俊),et al.A review of stable isotopic compositions of atmospheric particulate matter.Chinese Journal of Ecology (生态学杂志),2016,35(4):1063-1071 (in Chinese)
[19] Bothner-By A,Friedman L.The reaction of nitrous acid with hydroxylamine.Journal of Chemical Physics,1952,20:459-462
[20] Wang X (王曦),Cao Y-C (曹亚澄),Han Y (韩勇),et al.Determination of nitrogen and oxygen isotope ratio of nitrate in water with a chemical conversion method.Acta Pedologica Sinica (土壤学报),2015,52(3):558-566 (in Chinese)
[21] Pan Y,Tian S,Liu D,et al.Fossil fuel combustion-related emissions dominate atmospheric ammonia sources during severe haze episodes:Evidence from 15N-stable isotope in size-resolved aerosol ammonium.Environmental Science and Technology,2016,50:8049,doi:10.1021/acs.est.6b00634
[22] Pan Y,Tian S,Liu D,et al.Isotopic evidence for enhanced fossil fuel sources of aerosol ammonium in the urban atmosphere.Environmental Pollution,2018,238:942-947
[23] Park YM,Park KS,Kim H,et al.Characterizing isotopic compositions of TC-C,NO3--N,and NH4+-N in PM2.5 in South Korea:Impact of China’s winter heating.Environmental Pollution,2018,233:735-744
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