To better understand the sources of nitrogenous aerosols, particularly
water-soluble organic nitrogen (WSON) and water-insoluble organic nitrogen
(WION), in northeastern Asia, we measured total nitrogen (TN) and
water-soluble total nitrogen (WSTN) as well as nitrogen isotope ratios
(
In eastern Asia, high loading of aerosol nitrogen (
Aerosol ON is comprised of a wide range of nitrogenous compounds from
semivolatile amines to proteins and macromolecules (Cape et al., 2011; Laskin
et al., 2009; Wang et al., 2010). In addition to biomass burning, primary
sources, including biological particles emitted from soil, vegetation,
pollen, bacteria and the ocean surface, are important (Cape et al., 2011;
Jickells et al., 2013; Miyazaki et al., 2014; Neff et al., 2002). ON can also
be produced in the atmosphere via the reactions of
However, the relative importance of anthropogenic and biogenic emissions
including biomass burning is largely unknown, and the secondary formation of
ON has been poorly characterized (Cape et al., 2011; Jickells et al., 2013;
Kanakidou et al., 2012) and thus the land–atmosphere interactions of aerosol
Here, we present total
Total suspended particulate (TSP) samples were collected from Sapporo in the western
part of Hokkaido Island, northern Japan (43.07
It should be noted that aerosol samples collected on quartz fiber filters
might have positive (adsorption of gaseous
TN and WSTN contents and their isotope ratios (
We also measured WSTN using a total organic carbon (TOC)/total nitrogen (TN)
analyzer (Shimadzu TOC-Vcsh), as reported by Miyazaki et al. (2011). Briefly,
an aliquot of filter (1.4
Concentrations of WSTN measured by the EA are lower by
Details of the measurements of inorganic ionic species such as
Amounts of inorganic
Organic tracers such as hopanes, isoprene- and monoterpene-oxidation products
were determined using a capillary gas chromatograph (Hewlett-Packard 6890)
coupled to a mass spectrometer (Hewlett-Packard 5973) (GC/MS) as described
elsewhere (Fu et al., 2010). Briefly, organic tracer compounds were extracted
from the filter samples with dichloromethane / methanol (
All the data reported here are corrected for the field blank collected in each season.
Plots of 10-day backward air mass trajectories arriving over Sapporo at 500 m a.g.l.
Seasonal variations in
Ten-day backward air mass trajectories arriving in Sapporo at 500
In fact, the radiocarbon analyses showed that the percentage of modern carbon
(pMC) of total carbon and water-soluble organic carbon in our aerosols
started to increase from mid- to late winter onwards (Pavuluri et al., 2013),
although the growing season starts in May in Hokkaido when daily average
temperatures are
Linear relations of IN (sum of
Seasonal variations in
Seasonal and annual averages with standard deviation of the
concentrations of nitrogenous components and
Concentrations of TN and WSTN ranged from 348 to 1750
As seen from Fig. 3, WSTN contains mostly IN (i.e.,
Concentrations of WSON and WION in Sapporo aerosols ranged from the BDL to
288
Linear relations of WSON with
Concentrations of water-soluble organic nitrogen (WSON) and the mass fractions of WSON in water-soluble total nitrogen (WSTN) in Sapporo aerosols together with those in atmospheric aerosols from different sites around the world.
As seen from Table 2, the average concentration of WSON in Sapporo aerosols
is lower than that reported in urban aerosols from Davis, California, and
Kofu, Japan, as well as from coastal sites: Erdemli in Turkey, Crete in
Greece, and Qingdao in China. It is also lower than that reported in the
forest aerosols collected from Rondônia, Brazil during an intensive
biomass burning period (dry season) (Mace et al., 2003a) and from Sapporo,
Japan, and lower than in the marine aerosols over the Asian outflow regions:
the Yellow Sea, South China Sea and the western North Pacific (Table 2). In
contrast, the average concentration of WSON in Sapporo aerosols is comparable
to that of forest aerosols from Fujiyoshida, Japan, but higher than that from
Rondônia, Brazil, during the wet season. It is also higher than that of
the marine aerosols from pristine oceanic regions: Cape Grim, Australia (Mace
et al., 2003b), and Oahu, Hawaii (Cornell et al., 2001), and over the western
North Pacific (Miyazaki et al., 2011) (Table 2). In addition, the higher end
(maximum 288
Higher concentrations of WSON reported for urban aerosols from Davis,
California, during late fall and winter are attributed to increased amounts
of atmospheric liquid water, which promote a partition of gaseous WSON to
particles (Zhang et al., 2002). In Kofu and Fujiyoshida (forest site), Japan,
emissions from combustion sources including biomass burning and plant-derived
particles as well as secondary formation through the reaction of
On the other hand, the average concentration of WION (
Therefore, we consider that WSON in Sapporo aerosols may be mainly derived from anthropogenic emissions including biomass burning, although emissions from biological sources and secondary formation from gaseous hydrocarbon precursors cannot be excluded. Meanwhile, WION may originate from emissions of biological particles and secondary formation from biogenic hydrocarbons. We further examine the possible contributions from such sources in the following section based on comparisons between them and the source tracers.
The temporal trend in WSON is found to be somewhat similar to that of hopanes
(C
The temporal trend in WSON from late spring to early summer (Fig. 4a) is
similar to that of sucrose (Fig. 4e), which is a tracer of pollens emitted
from terrestrial higher plants (Fu et al., 2012). The seasonal trend in WSON
(Fig. 4a) is also similar to those of biogenic secondary organic aerosols
(SOA), i.e.,
Spearman's rank correlation of WSON and WION with source
tracers in Sapporo aerosols during the study period (
The above comparisons of WSON with source tracers imply that anthropogenic
emissions including biomass burning are major sources of WSON in Sapporo
aerosols. Their contributions to Sapporo aerosols may have been enhanced in
autumn and winter when the air masses enriched with forest fire and fossil
fuel combustion products are often delivered from Siberia, passing over
northeastern China (Fig. 1a, b). In fact, fossil fuel consumption is
significantly higher in winter than in any other season in eastern Asia
(Zhang et al., 2009). Furthermore, emissions of biological particles and
secondary production by the reaction of biogenic hydrocarbons with
The results of Spearman's rank correlation analysis between WION and source
tracers are presented in Table 3. WION shows a significant inverse
correlation with hopanes and levoglucosan during the campaign (Table 3). By
contrast, the temporal trend in WION is similar to those of sucrose (Fig. 4e)
during late spring to early summer and of biogenic SOA tracers (isoprene- and
Based on the above comparisons of WION with source tracers, we suggest that
the WION in Sapporo aerosols is mainly derived from emissions of biological
particles such as pollens and from secondary production by the reactions of
biogenic hydrocarbons (containing carbonyls) with
Based on observations under controlled environmental conditions, Husted and
Schjoerring (1996) reported that
Scatterplots between
We also found that
Range or mean
As seen from Fig. 6,
Figure 7 compares the range (or mean) of
However,
On the other hand, lower values of
Water-soluble organic nitrogen (WSON) and water-insoluble organic nitrogen
(WION) and
This study was in part supported by Japan Society for the Promotion of Science (Grant-in-Aid nos. 1920405 and 24221001) and the Environment Research and Technology Development Fund (B903) of the Ministry of the Environment, Japan. Edited by: A. B. Guenther