Abstract
This investigation is about the study of mid-continental (1500km from the coastal areas) reactive
nitrogen chemistry i.e the presence of nitryl chloride (ClNO ) compound and how it recycles both
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the chlorine and nitrogen oxide gases in the troposphere.
The concentration of NO and N O was measured by pulsed Cavity Ringdown Spectroscopy while
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the ClNO and N O were detected using Chemical Ionization Mass Spectrometer at a monitor time
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of 24 hours for the period of 11 February – 25 February. Observations were this time made in-situ
at the National Oceanic and Atmospheric Admisntris’s Kohler Mesa facility, just west and 150 m
above Boulder, Colorado.
What they found was that although the area is far removed from sea spray, ClNO production was
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still routinely observed. They also found that the ClNO output for contiguous US lies in the range
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3.2-8.2 Rgyr-1, a level similar to previous global estimates for coastal and marine regions. And from
an estimated a photolytic Cl• source production of 1.4-3.6 Tg Cl• yr, they imply that a significant
fraction of the troposphere Cl• source is anthropogenic (caused by human source) and that nitry,
Summary Exercise
This investigation is about the study of mid-continental (1500km from the coastal areas) reactive
nitrogen chemistry i.e the presence of nitryl chloride (ClNO ) compound and how it recycles both
2
the chlorine and nitrogen oxide gases in the troposphere.
N O can react with airborne particles such to produce HNO3 (reaction (1a)), (ClNO2)) and nitrate
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(NO3-).
Therefore the yield ClNO is limited by both the water and chloride concentrations within particles
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and also the amount of soluble chloride or NOx availability and reactivity in the environment.
Also , ClNO a NOx recycler through photolysis after sunrise since it accounts for 30-50% for most
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of the total NOx removal. This is show in reaction 1b)
This chemistry is important because chlorine atoms can decrease the lifetimes of gaseous elemental
mercury and hydrocarbons such as, greenhouse gas such as methane. And chlorine atoms also
affect ozone a greenhouse gas potentially toxic and animals to plants production in the troposphere
This is done by affecting NOx concentration in the atmosphere, which in turns influences climate by
directly and indirectly regulating oxidant budgets that determine the methane lifetime and affect
aerosol formation.
Since previous studies have been restricted to coastal or marine region, observations were this time
made in-situ at the National Oceanic and Atmospheric Admisntris’s Kohler Mesa facility, just west
and 150 m above Boulder, Colorado. This site was also chosen because it is minimally affected by
direct, local night-time emissions and hence allows overnight observation of the chemical evolution
of air masses characteristic of this region.
The concentration of NO and N O was measured by pulsed Cavity Ringdown Spectroscopy while
3
2
5
the ClNO and N O were detected using Chemical Ionization Mass Spectrometer at a monitor time
2
2
5
of 24 hours for the period of 11 February – 25 February.
The ClNO , N O and pCl- concentration was then being plotted in terms of mixing rations and
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analyzed. What they found was that although the area is far removed from sea spray, ClNO
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production was routinely observed. This is a phenomenon unknown before although the
ingredients for this source such as NOx and particulate chloride were known to exist and possibly
due to transportation by inland salt beds and by anthropogenic (caused by human) sources. And
also it was proven that ClNO production was consistent with the mechanism (2) by being observed
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only at night or in the early morning.
They also modeled the evolution of ClNO and pCl- over the 12 h period from sunset on 15 February
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and found that the ClNO output for contiguous US lies in the range 3.2-8.2 Rgyr-1, a level similar to
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previous global estimates for coastal and marine regions. This is in turn estimates a photolytic
Cl• source production of 1.4-3.6 Tg Cl• yr, which is the same order as that inferred from methane
isotopes in remote (anthropogenic) regions
All these results imply that a significant fraction of the troposphere Cl• source is anthropogenic,
distributed over a relatively small area of the Earth’s surface – polluted continental and coastal
regions- and concentrated in a fraction of each day. Also, the widespread ClNO production renders
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NOx chemistry a potential source of oxidants and ozone in polluted regions, and may have an even
larger effect on their oxidizing power of the lower troposphere than current models estimate.
In conclusion, I learnt that although it takes time to do one specific research, it is nevertheless
worthwhile since many conclusions can be inferred from it. Like how the investigation not only
leads us to find out that there is a considerable amount of ClNO in mid-continental areas but how
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the levels of US itself is comparable to previous global estimates.