Subscriber access provided by UNIV OF DURHAM
Letter
The Contribution of Biomass Burning to Ambient Particulate Polycyclic Aromatic Hydrocarbons at a Regional Background Site in East China Shuduan Mao, Jun Li, Zhineng Cheng, Guangcai Zhong, Kechang Li, Xiang Liu, and Gan Zhang Environ. Sci. Technol. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.estlett.8b00001 • Publication Date (Web): 30 Jan 2018 Downloaded from http://pubs.acs.org on January 30, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Environmental Science & Technology Letters is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 15
Environmental Science & Technology Letters
For Table of Contents Use Only
Title: The Contribution of Biomass Burning to Ambient Particulate Polycyclic Aromatic Hydrocarbons at a Regional Background Site in East China
Authors: Shuduan Mao, Jun Li, Zhineng Cheng, Guangcai Zhong, Kechang Li, Xiang Liu and Gan Zhang
1
ACS Paragon Plus Environment
Environmental Science & Technology Letters
1
The Contribution of Biomass Burning to Ambient Particulate Polycyclic Aromatic
2
Hydrocarbons at a Regional Background Site in East China
3 4
Shuduan Mao†,‡, Jun Li †, Zhineng Cheng †, Guangcai Zhong †, Kechang Li †, Xiang Liu † and Gan
5
Zhang *,†
6
†
7
Academy of Sciences, Guangzhou 510640, China
8
‡
9
Supporting Information
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese
University of Chinese Academy of Sciences, Beijing 100049, China
10 11
ABSTRACT: Biomass burning has a significant impact on regional air quality, public health, and
12
climate change. It is an important source of particulate polycyclic aromatic hydrocarbons (PAHs),
13
which are a major class of toxic air pollutants. To estimate the contribution of biomass burning to
14
ambient particulate PAH concentrations, fifteen PAHs and three anhydrosugars (levoglucosan,
15
galactosan, and mannosan) were analyzed in particulate samples collected at a background site in east
16
China from August 2012 to August 2015. Higher concentrations of all species were observed in fall
17
and winter. Indoor biofuel combustion in north China was considered to be the major contributor to
18
the high concentrations of anhydrosugars in fall and winter, because there were few fires detected on a
19
fire count map for this period. A tracer-based approach, using the ratio of PAHs to levoglucosan
20
(PAHs/Lev) in fresh biomass burning aerosols, was proposed and used to estimate the contribution of
21
biomass burning to PAHs. The results showed that biomass burning contributed nearly 11% of the
22
total particulate PAHs. The estimation of the contribution from biomass burning using PAHs/Lev
2
ACS Paragon Plus Environment
Page 2 of 15
Page 3 of 15
Environmental Science & Technology Letters
23
agreed well with the results obtained from an independent positive matrix factorization (PMF)
24
analysis.
25
INTRODUCTION
26
Biomass burning in both open field fires and domestic biofuel combustion can emit large
27
amounts of greenhouse gases, trace gases and particulate matter, which can affect air quality, public
28
health, and climate change.1, 2 Studies of ambient volatile organic compounds (VOCs) at a receptor site
29
in Pearl River Delta during October-November 2008 have revealed that biomass burning accounts for
30
9–37% of the mixing ratios of selected VOC species, with the figure being > 30% for aromatics,
31
formaldehyde, and acetaldehyde.3 Model- and observation-based estimations have indicated that open
32
biomass burning accounts for 37% of PM2.5 in the Yangtze River Delta during the harvest period in
33
summer 2011.4 Radiocarbon (14C)-based source apportionment studies at south of Hainan Island from
34
May 2005 to August 2006 and at Gosan, Korea from April 2013 to April 2014 have shown that
35
biomass burning could account for > 30% of the organic carbon (OC) concentrations in China.5, 6
36
Among the trace substances emitted from biomass burning, there are also polycyclic aromatic
37
hydrocarbons (PAHs), an important class of persistent organic pollutants (POPs).7,
38
generated by the incomplete combustion of biomass and fossil fuels.9 They are ubiquitous in the
39
atmosphere and are considered to be a major class of toxic air pollutant.10, 11 They can cause serious
40
health effects due to their carcinogenicity and mutagenicity. In recent decades, PAHs have attracted
41
considerable public and scientific attention, especially in China where high PAH concentrations are
42
frequently reported.11, 12 Efforts have been made to estimate PAH emissions. An emission inventory in
43
2004 indicated that China was one of the largest PAH emitters in the world, and that biomass
44
combustion and coke ovens were the most important sources.13 Latterly, an updated global PAHs 3
ACS Paragon Plus Environment
8
PAHs are
Environmental Science & Technology Letters
45
emission inventory for a period from 1960 to 2008 suggested that biomass fuels were the globally
46
major PAH sources.12 Due to economic considerations and the promotion of coal consumption
47
reduction policies, biomass fuel has become a popular alternative energy source to fossil fuels in
48
households, and manufacturing and service industries in rural regions.14, 15 Therefore, assessment of
49
the contribution of biomass fuels to ambient PAH levels is of great significance. Molecular markers,
50
especially levoglucosan (lev), can be used to quantify the contribution of biomass burning to
51
atmospheric pollutants, such as particulate matter and OC aerosol.16, 17 A lev-based approach may
52
therefore also have the potential to quantify the contribution of biomass burning to PAH
53
concentrations.
54
A biomass burning plume not only has a local impact, but also has effects at the regional scale
55
through long range transport.18 As one of the most economically developed regions in China, east
56
China experiences serious air pollution. Although it is not a high emission intensity area for PAHs
57
from biomass burning, the outflow flux of PAHs from north China has resulted in elevated
58
concentrations of atmospheric PAHs in this region.19 Additionally, it is reported that most PAHs were
59
transported out of China through the eastern boundary.19 Therefore, Ningbo Atmospheric Environment
60
Observatory (NAEO, 29°40.8′N, 121°37′E, 550 m ASL) in east China, which is a key site on the
61
outlet transport route for aerosols from the Chinese continent to the Pacific Ocean, was selected as a
62
regional background site to monitor PAHs in this study (Figure S1). The sampling site has been
63
described in previous report.20 The aim of this study was to apportion the sources of PAHs and
64
estimate the contribution of biomass burning to particulate PAHs in east China.
65
MATERIALS AND METHODS
4
ACS Paragon Plus Environment
Page 4 of 15
Page 5 of 15
Environmental Science & Technology Letters
66
Sampling. Since the year 2012, successive 24 h total suspended particle samples were collected
67
once a week at NAEO by high volume air samplers fitted with quartz microfiber filters (QFFs) (Grade
68
GF/A, 20.3 × 12.7 cm; Ahlstrom Munktell, Falun, Sweden) operating at 300 L/min. The QFFs were
69
baked at 450°C for 6 h before sampling and then sealed and stored at -20°C after collection. A total of
70
73 QFF samples, i.e., 1 from each fortnight from August 2012 to August 2015, were used in this study.
71
Sample Pretreatment and Analysis. Details of the sample treatment and analytical method can
72
be found in Text S1 in the Supporting Information. Briefly, a section of each filter sample was spiked
73
with perdeuterated PAHs as surrogates and extracted in a Soxhlet apparatus for 24 h with
74
dichloromethane (DCM). The extracts were further purified on a multilayer neutral silica gel column.
75
15 PAHs were then quantified by gas chromatography–mass spectrometry (GC-MS), with a DB-5MS
76
capillary column (30 m × 0.25 mm × 0.25 µm, model 7890/5975; Agilent, Santa Clara, CA, USA):
77
acenaphthene(Ace), acenaphtylenc(Acy), fluorene (Flu), phenanthrene (Phe), anthracene (Ant),
78
fluoranthene (Fla), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene
79
(BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), dibenzo[a,h]anthracene (DahA),
80
benzo[g,h,i]perylene (BghiP) and indeno[1,2,3-c,d]pyrene (IcdP).
81
A section of each sample was spiked with
13
C labeled lev as a recovery standard and Soxhlet
82
extracted for 24 h with DCM/methanol (40:3 by volume) to analyze anhydrosugars. The extracts were
83
anhydrated with an anhydrous sodium sulfate column, spiked with methyl-β-L-xylanopyranoside
84
(m-XP) as an internal standard and then dried completely by a gentle nitrogen stream. Finally, a
85
derivatization reagent (a mixture of N,O-Bis(trimethylsilyl) trifluoroacetamide (1% trimethylsilyl
86
chloride) and pyridine) was added for the sequent reaction (70°C, 1 h). The resulting solution was then
87
immediately analyzed by GC-MS.
5
ACS Paragon Plus Environment
Environmental Science & Technology Letters
88
A punch of each filter was analyzed to determine the organic carbon (OC) and elemental carbon
89
(EC) concentrations by a DRI Model 2015 Thermal/Optical Carbon Analyzer (Atmoslytic Inc.,
90
Calabasas, CA). Details of analytical method can be found in Text S1.
91
Quality Control. Laboratory and field blank filters were analyzed. The method detection limit
92
(MDL) was defined as the average of all blanks plus three times the standard deviation. The MDLs of
93
each target compound are listed in Table S1. The average recoveries were 75 ± 15%, 91 ± 12%, 101 ±
94
14%, 100 ± 19%, and 95 ± 14% for acenapthene-d10, phenanthrene-d10, chrysene-d12, perylene-d12,
95
and 13C labeled lev, respectively. All reported values were corrected for recovery in this study.
96
Air Mass Back Trajectories. Five-day back trajectories were calculated at 6 h intervals for the
97
campaign period using the HYSPLIT model (http://ready.arl.noaa.gov/HYSPLIT.php). All individual
98
trajectories were clustered for each season, as shown in Figure S1. The air mass mostly originated
99
from the west Pacific and the South China Sea in summer, and passed over the continental regions in
100
Mongolia and north China during other seasons.
101
RESULTS AND DISCUSSION
102
Temporal Variations and Correlations between Lev and Particulate PAHs. The
103
concentrations of 15 particulate PAHs, 3 anhydrosugars, OC and EC are listed in Table S2. The
104
composition of PAHs in this study was dominated by high molecular weight PAHs, with low vapor
105
pressures. Anhydrosugars were composed primarily of levo (91 ± 4.4%), followed by mannosan (6.1 ±
106
3.3%), and galactosan (3.3 ± 1.7%). A time-series of particulate PAHs, three anhydrosugars, OC and
107
EC from August 2012 to August 2015 is shown in Figure S2. The average concentrations of each
108
species in different seasons are listed in Table S3. Seasonal characteristics were observed for each
6
ACS Paragon Plus Environment
Page 6 of 15
Page 7 of 15
Environmental Science & Technology Letters
109
species, with the highest average concentrations being in winter (December to February) and fall
110
(September to November), and the lowest in summer (June to August).
111
Five-day backward trajectories showed that air masses passed over north China in winter, where
112
biofuel and fossil fuel are typically used for household heating. During summer, the air masses
113
originated from the west Pacific or the South China Sea. The low abundance of components at this
114
time was mostly attributed to clean-air-masses originating from marine areas. According to fire count
115
maps for each season (Figure S3), produced by the satellite based Moderate Resolution Imaging
116
Spectroradiometer (MODIS), few wild fires occurred in China during winter and fall when the highest
117
concentration of lev was observed. Moreover, air masses passed over north China during winter and
118
fall. These results suggested that high concentrations of 3 anhydrosugars were mostly attributed to
119
indoor biofuel combustion in north China (such as domestic heating by biomass and combustions of
120
agricultural crops and wood in domestic stoves), which could not be detected by satellites.
121
Correlations between lev (a well-known biomass burning tracer) and individual selected
122
particulate PAH compounds were estimated and the Person correlation coefficients (r) are displayed in
123
Table 1. The correlation coefficients (r) were above 0.75 for 71 samples with each particulate
124
compound. The strong correlations between lev and particulate PAH congeners, as showed in Table 1,
125
would suggest a strong association of the PAHs to particulate, from source/origin to atmospheric
126
processes.
127
Table 1. Correlations between lev and individual particulate PAH compounds during the whole sampling
128
campaign Lev vs. particulate PAHs
N
r
P
Lev vs.Phe
71
0.75
