English
 
Help Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT
  The sensitivity of the photostationary state of NOx and its implication for the oxidation capacity in a semi-rural and boreal forest region/ Javed, Muhammad Umar. Mainz, Univ., Diss., 2015

Javed, U. (2015). The sensitivity of the photostationary state of NOx and its implication for the oxidation capacity in a semi-rural and boreal forest region/ Javed, Muhammad Umar. Mainz, Univ., Diss., 2015. Thesis, Univ., Mainz.

Item is

Files

show Files

Locators

show
hide
Description:
-

Creators

show
hide
 Creators:
Javed, U.1, Author              
Affiliations:
1Atmospheric Chemistry, Max Planck Institute for Chemistry, Max Planck Society, ou_1826285              

Content

show
hide
Free keywords: -
 Abstract: The roles of nitric oxide (NO) and nitrogen dioxide (NO2) are strongly coupled with the cleansing capacity of the atmosphere by controlling the photochemical production of ozone (O3) and affecting the abundance of the hydroxyl (OH) radical and nitrate radical (NO3). During daytime, when conditions of sufficient radiation and O3 prevail, NO and NO2 are in a fast photochemical equilibrium, often labelled as being in a ‘photostationary state’. Therefore the sum of NO and NO2 is referred to as NOx. The photostationary state of NOx has been previously studied at various locations ranging from cities (highly polluted) to remote regions (less polluted). The photochemical cycling between NO and NO2 is understood reasonably well under high NOx conditions (typically in urban areas). In contrast, significant gaps in understanding the cycling between NO and NO2 have been revealed in semi-rural to remote regions under low NOx conditions. These gaps could be related to potential interferences in NO2 measurements, especially in case of indirect methods that might suffer from artefacts. If NO2 interferences can be excluded, it is often concluded that these gaps are related to the presence of an ‘unknown oxidant’ converting NO to NO2, especially at very low NOx concentrations. In this study, the photostationary state of NOx is analysed to evaluate whether unknown processes are present. A newly developed gas analyser (GANDALF) based on laser induced fluorescence (LIF) for measuring NO2 directly was deployed for the first time during the 2011 PARADE field study. PARADE took place in a semi-rural area of central Germany in summer 2011. Comprehensive measurements of NO2 using different techniques (DOAS, CRD, and CLD) facilitated a detailed and successful comparison of GANDALF with other NO2 measurement techniques. In order to analyse the photostationary state of NOx based on the NO2 measurements by GANDALF in this environment, measurements of different relevant trace gas species and meteorological parameters have been carried out. Moderate NOx levels 10^2 to 10^4 parts per trillion were observed during PARADE at the location, while biogenic volatile organic compounds (BVOCs) from surrounding forest, mainly coniferous trees, were of the order of 10^2 parts per trillion. The characteristics of the NOx photostationary state have been studied under low NOx conditions (10^1 to 10^3 parts per trillion) for a different location in a boreal forest region during HUMPPA-COPEC-2010. The field study HUMPPA-COPEC was conducted at the ‘SMEAR II’ field station in Hyytiälä in southern Finland in summer 2010. The characteristics of the photostationary state of NOx are compared in this study for the two environments. Furthermore, the comprehensive data set including measurements of trace gases relevant for the radical chemistry [OH and hydroperoxy (HO2) radicals], as well as measurements of the total OH reactivity, provide the opportunity to test and improve our current understanding of NOx-related photochemistry using a box model constrained to observations. Although NOx levels in HUMPPA-COPEC are lower compared to PARADE, while the BVOCs levels, are higher, the cycling process from NO to NO2 is understood reasonably well in both cases. The analysis of photostationary state reveals that potential unknown processes are not present at either of the largely different locations. The current representation of NOx chemistry mechanisms is simulated for HUMPPA-COPEC by using the MIM3* mechanism and found to be consistent with results obtained from the photostationary state of NOx.

Details

show
hide
Language(s): eng - English
 Dates: 2015-05-122015
 Publication Status: Published in print
 Pages: -
 Publishing info: Mainz : Univ.
 Table of Contents: -
 Rev. Type: -
 Identifiers: -
 Degree: -

Event

show

Legal Case

show

Project information

show

Source

show