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	<journal>
		<journal_title>Atmospheric Chemistry and Physics</journal_title>
		<journal_url>www.atmos-chem-phys.net</journal_url>
		<issn>1680-7316</issn>
		<eissn>1680-7324</eissn>
		<volume_number>9</volume_number>
		<issue_number>22</issue_number>
		<publication_year>2009</publication_year>
	</journal>
	<doi>10.5194/acp-9-8813-2009</doi>
	<article_url>http://www.atmos-chem-phys.net/9/8813/2009/</article_url>
	<abstract_html>http://www.atmos-chem-phys.net/9/8813/2009/acp-9-8813-2009.html</abstract_html>
	<fulltext_pdf>http://www.atmos-chem-phys.net/9/8813/2009/acp-9-8813-2009.pdf</fulltext_pdf>
	<start_page>8813</start_page>
	<end_page>8823</end_page>
	<publication_date>2009-11-20</publication_date>
	<article_title content_type="html">Surface ozone trend details and interpretations in Beijing, 2001â€“2006</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>G. Tang</name>
		</author>
		<author numeration="2" affiliations="2">
			<name>X. Li</name>
		</author>
		<author numeration="3" affiliations="1">
			<name>Y. Wang</name>
			<email>wys@dq.cern.ac.cn</email>
		</author>
		<author numeration="4" affiliations="1">
			<name>J. Xin</name>
		</author>
		<author numeration="5" affiliations="1">
			<name>X. Ren</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China</affiliation>
		<affiliation numeration="2" content_type="html">Beijing Municipal Environmental Protection Bureau, Beijing 100044, China</affiliation>
	</affiliations>
	<abstract content_type="html">Beijing is a megacity situated in the rapidly developing
Beijing-Tianjin-Hebei region of northern China. In this study, we analyze
data on ozone and nitrogen oxide levels obtained at six urban sites in
Beijing between the months of July and September. Our goal is to investigate
average trends and interpretations over the 2001â€“2006 period. Average
concentrations of NO&lt;sub&gt;x&lt;/sub&gt; (NO&lt;sub&gt;x&lt;/sub&gt;=NO+NO&lt;sub&gt;2&lt;/sub&gt;), O&lt;sub&gt;3&lt;/sub&gt;, and O&lt;sub&gt;x&lt;/sub&gt;
(O&lt;sub&gt;x&lt;/sub&gt;=O&lt;sub&gt;3&lt;/sub&gt;+NO&lt;sub&gt;2&lt;/sub&gt;) were 49.2&amp;plusmn;5.9 ppbv, 26.6&amp;plusmn;2.8 ppbv, and
60.3&amp;plusmn;1.9 ppbv, respectively. NO&lt;sub&gt;x&lt;/sub&gt; concentrations decreased linearly at a
rate of 3.9&amp;plusmn;0.5 ppbv/yr after 2002, while ozone concentrations
increased at a rate of 1.1&amp;plusmn;0.5 ppbv/yr during 2001â€“2006, and O&lt;sub&gt;x&lt;/sub&gt;
concentrations remained nearly constant. The reduction of NO&lt;sub&gt;x&lt;/sub&gt; emissions and
elevated non-methane hydrocarbon (NMHCs) emissions may have contributed to
the increased O&lt;sub&gt;3&lt;/sub&gt; concentrations in Beijing. When the contributions from
Beijing&apos;s urban and surrounding areas were disaggregated via trajectory
cluster analysis, daily maximum and average O&lt;sub&gt;x&lt;/sub&gt; concentrations attributable
to Beijing&apos;s local emissions increased linearly at rates of 1.3&amp;plusmn;0.6 ppbv/yr
and 0.8&amp;plusmn;0.6 ppbv/yr, while the O&lt;sub&gt;x&lt;/sub&gt; concentrations attributable
to regional areas decreased linearly at rates of 0.6&amp;plusmn;0.3 ppbv/yr and
0.5&amp;plusmn;0.3 ppbv/yr, respectively. The decrease in O&lt;sub&gt;x&lt;/sub&gt; concentrations of the
surrounding areas was found to counteract increasing Beijing urban O&lt;sub&gt;x&lt;/sub&gt;
production, leading to nearly constant O&lt;sub&gt;x&lt;/sub&gt; concentrations in the Beijing
region over the study period. Our results may be helpful for redefining
government strategies to control the photochemical formation of air
pollutants in the Beijing region. Our conclusions have relevance for
developing megacities worldwide.</abstract>
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</article>

