博 士（環境科 学）

シヱノ ヾシシュクンドゥ

学 位 論 文 題 名Atmosphericchemicalstu
diesonthed
istributionsof
dicarboxylicacids, ketocarboxylic acids andcx‑dicarbonylsinmarine andbiomass b
urningaerosols
and stable isotopic composition ofaerosol nitrogen and carbon（海洋エアロゾルおよびバイオマス燃焼エアロゾル中のジカルボン酸，ケトカルボン酸，ぱージカルボニルの分布とエアロゾル窒素・炭素の安定同位体組成に関する大気化学的研究）

学位 論文内容の要旨

Abstracts
Aerosol samples (n=84) were collected continuously from April 2003 to April 2004 at
Gosan site in Jeju Island, South Korea. They were studied for diacids, ketoacidsand a‑dicarbonyls, as well as organic carbon (OC), element
al carbon(EC),water‑solubleorgan
iccarbon (WSOC), and water‑soluble inorganic ions. While the WSOC fraction accounted for
25% mass concentration of S042‑ in spring and summer,〜 18% were found in autumn andwint
er. A
verag
e WSO
C toOC ratiosrange
d fro
m 0.5t0 0.6, w
ith t
he hi
ghestvalu
e inwinter.
Higher ratios than those reported in East Asia, from which ai
r mas
ses are tr
anspo
rtedtoGosan, suggest the photochemical processing of aerosols during a long‑range transport.
Oxalic (C2) acid followed by malonic (C3) acid was the most abunda
nt inallseaso
ns. T
hemeanconc
entration(784ng m‑3) and rel
ativeabundances (81, 8.4, and15%)of t
otaldiacids
in detected molecular organics, OC and WSOC were found the highest in summer, whereas
those (47 ng m‑3 and 10, 0.5, and 0.8%) ofketo
acidsandthose(23ng m‑
3 and7, 0.3, and0.5%) ofdicar
bonyls sho
wed t
he hi
ghestin w
inter. The
se resultssu
gg
estthatthes
ou
rc
esof
diac
ids a
re different from the sou
rcesof ke
toa
cidsanddicarbonyls.T
herearedif
ferencesintheseaso
nal v
ariat
ionsofdia
ci
dsan
dre
la
tedc
om
pounds,w
hic
hisa
lsoa
nin
dic
at
io
nofth
ei
r
different sources. This study demonstrates an enhanced photochemical production anddegradation in summer than in other seasons. Higher positive correlations between
combustion tracers (K+ and EC) and diacids and related compou
nds in win
ter were observ
edthanthose insummer, pointing tohighe
r emi
ssionof diacids andrelated compou
nds ortheir
precursors from fossilfuel/biom
ass bumingin w
inter. More tight, positi
ve co
rrela
tionsofsecondary tracers(S042‑ and N03') wi
th diacidsandrelat
ed co
mpoun
ds inwint
er th
an those
insummer areexpl
ainedby theirmorespeci
fic s
ource
s inwinter.
The atmosphe
ric aeroso
l samples(n=84) collected atGosansitewerealsoanal
yzedforthe measurements of total nitrogen (TN) and itsisot
opicratio(815N) aswellas nitrog
enspecies (NH4+ and N03'). Measurements were also conducted for remained N and removedN
on HCl fume treatment. A pronounced seasonal variation was found in the 815N of TN,― 1005−remained N (mostly composed of NH4+) and removed N (mostly composed of N03'). The
highest mean 815N values of TN (+16.9+4.59'oo) and remained N (+20.2+5.2Voo) are detectedin summer (June‑August), whereas the lowest mean 815N values (+12.9+3.4%o, +11.3+5.1%o,respectively) are in winter (December‑February). This can partly be explained by anenhanced contribution of 15N‑enriched emissions fromagricultur
al straw burnin
g inChinain
a harvest season (summer and autumn). The mean 815N of removed N showed an opposite
trend: the lowest (+9.2+3.7%o) in warm season (March‑August) and the highest(+14.8+3.8%o) in cold season (September‑February). These results can be explained bychanges in source regions and emission strengths from different sources of nitrogenous
species, and difference in secondary aerosol nitrogen formation between the warm and coldseasons. Higher ratios of Ca2+/Na+ and the lowest ratios of Na+/(Cl‑ + N03') are found toassoci
ate w
ith l
ower815Nvalues ofremov
ed Nasares
ultoflessi
so
top
icenrichment(Sproduct‑reactant) during the reaction betw
een F
fN03and d
ust p
artic
les.Thisstudydemo
nstra
tes t
hat
15N/14N ratio is a good process tr
acerof nitroge
nousspeci
es duringlongrangetransportint
he atmosphere.
Aerosol particles (PM2.5) were collecte
d dur
ing t
he day (n=6)andnighttime(n=9)fr
oma
tropical pasture site in Rondonia, Brazil during an intensive biomass bumingperiod (16‑26September, 2002). Higher normalized (by K+, levoglucosan, or apparent elemental carbon,ECa) mass concentrations of S042‑ and CH3S03 in daytime suggest their photochemicalproduction, while the opposite trend for N03 suggests its transfer to the aerosolphaseat
lower temperatures and higher humidities, as well aspossi
bly p
roduc
tionthrou
gh hy
droly
sisof N205 0n aqueous aerosol particles. About 4.2‑7.5% of OC (5‑13% of water‑solubleorganic carbon (WSOC)) could be characterized at the molecular level using GC‑MS andGC‑FID. Among the detected organic compound classes, the relative abundances ofanhydrosugars and ar
omati
cs we
re hi
gherin ni
ght s
amples, bu
t sug
ars/s
ugaralcoh
ols,diacids,
oxoacids and a‑dicarbonyls were more abundant in daytime samples. Consecutive day andnight samples showed that 813C values of total carbon (TC) were lower in daytime samples,
which can be interpreted as resulting from higher con
tribu
tionof refract
ory TC depletedin
13C due to predominant flaming combustion. The 815N values of total nitrogen (TN) ranged
from +23.5%o to +25.7%o, however, there was no trend in day and night samples. Higher
values of 813C and 815N for biomass burning particles than those of unbumed vegetationreflect positive isotopic enrichment either during the formation of particlesor afterthee
missi
on ofparticlesin t
he atmosphere.
The PM2.5 aerosol samples were also analyzed for homologous series of dicarboxylic
acids (C2‑Cll) and related compounds (ketocarboxylic acids and dicarbonyls) using gas
chromatography and GC/mass spectrometry (GC/MS). Among the species detected, oxalic
acid was found to be the most abundant, followed by succinic, malonic and gly
oxyli
c aci
ds.
Average concent
ratio
ns oftota
l dic
arbox
ylicacids, ketocarb
oxyli
c aci
ds and a‑dicarb
onylsinthe aerosol samp es were 2180, 167and56 ngm‑3,resp
ectiv
ely.Theseare2‑8,3‑11and 2‑16
times higher, respectively, than those reported in urban aerosols, such as in 14 Chinese
megacities. Higher ratios of dicarboxylic acids and related compounds to biomass burning
tracers (levoglucosan and K+) were found in daytime than in nighttime, suggesting animportance of the photochemical production. On the ot
her hand,highe
r rat
ios o
f oxa
lic acid
to other dicarboxylic acids and related compounds normalized to biomass burning tracers(levoglucosan and K+) in daytime provide an evidence for possible degradation ofdicarboxylic acids (>C3) in this smoke‑polluted environment. Assuming that these diacidsand related compounds are photochemically oxidized to oxalic acid in daytime,thisproc
esscould account for, on average, 77%of t
he formati
on ofoxal
ic acid. T
he remaini
ng portionof
oxalic acid may have been directly emitted from biomass burning as suggested by a goodcorrelation with the biomass burning tracers (K+, CO and ECa) and organic carbon (OC).
However, photochemical production from other precursors could not be excluded.
‑ 1006 ‑学 位論文審査の要旨
主査
副査
副査
副査
副査
副査

教授

河村公隆

教授

吉川久幸

教授

乗木新一郎

准教授

関准教授

角皆助教

宮崎雄三

宰
潤（大学院理学研究院）

学 位 論 文 題 名Atmosphericchemi
calstudiesonthedistri
butionsof
dicarboxylic acids, ketocarboxylic acids andcv‑dicarbonyls inmarineandbiomassburnin
gaerosolsand stable isotopic compositionof
aerosol nitrogen and carbon（海洋エアロゾルおよびバイオマス燃焼エアロゾル中のジカルボン酸，ケトカ ルボン酸，d−ジカルボニルの分布とエアロゾル窒素・炭素の安定同位体組成に関する大気化学的研究）

The ubiquitous presence and significant contribution of dicarboxylic acids and relatedcompounds (ketocarboxylic acids and a‑dicarbonyls) to aerosol mass is well recognized in theatmosphere. Although we do have limited knowledge about their che
micalform
ationand.
degradation, and sources, these compounds are widely believed to be produced by atmosphericphotochemical processes. Therefore, they can provide information on the chemical evolution ofwater‑soluble organic aerosols, which is poorly understood. Dicar
boxyl
ic ac
ids c
an co
ntrib
ute tothe CCN activity, which affects cloud microphysical properties and hence precipitation pattems
and cloud albedo. To better understand the source and formation mechanisms of dicarboxylic
acids and related compounds in the atmosphere, marine aerosol samples (n = 84) (total suspendedparticles: TSP) were collected at Gosan site in Jej
u Island,SouthKore
a from April 20
03 toApril
2004 whereas biomass buming aerosol samples (daytime: 6 and nighttime: 9) in the particle size
<2.5 ym were collected from a Amazonian pasture site in Rondonia, Brazil, during an intensive
biomass buming period of 16‑26 September 2002. The usefulness of 813C of total carbon (TC)and 815N of aerosol nitrogen such as total nitrogen (TN), remained nitrogen (remained N,mostlyNH4+) and removed nitrogen (removed N, mostly N03'), which has rarely been addressed in theliterature, was examined to explain their sources and chemical process
ing in theatmo
sphere, andbiomass buming mechanism. Furthermore, organic carbon (OC), elemental carbon (EC), water‑‑ 1007−

soluble organic carbon (WSOC), and water‑soluble inorganic ions were studied here.
Among the molecular organics detected,oxalic acid (C2) was found tobe t
he most ab
undant,followed by malonic acid (C3) in marine aerosols and by succuuc acid (C4) in biomass buming
aerosols. The mean concentrations of total dicarboxylic acids, ketocarboxylic acids and a‑
dicarbonyls are 784, 41, and 15 ng m‑3 in the marine aerosols from Gos
an si
te whereasthos
e are2180, 167, and 56 ng m‑3 in biomass buming aerosols from Amazon. The 2‑16 times higher
concentrations of diacids and related compounds in biomass buming aerosols thanthos
e reported
in urb
an ae
rosol
s ind
icatethatbiom
ass burnin
g isa veryi
mpo
rtantsou
rc
efo
rd
ic
arbox
yl
ica
cids .
and relatedcompoundsat t
he re
giona
l andglob
al sc
ales.
Theannua
l mea
n con
tribu
tionsof d
icarb
oxyli
c aci
ds, k
etoca
rboxy
licac
id
sa
ndd
ic
arb
onyl
sto
WSOC are 12, 1, and 0.4% in manne aerosols, respectively. They are several times higher thanthose reported in East Asian countriesfromwhichairmasses aretran
sport
ed toGosan,indicati
ng
an importance of photochemical processing of aerosols during a long‑range transport. Higher
ratios of dicarboxylic acids and related compounds to biomass buming tracers (levogl
ucosa
n andK+) inbiom
ass burnin
g aer
osols
, aswellas hi
gherrati
oso
fo
xa
li
caci
dtoo
therdi
car
bo
xy
li
ca
ci
dsand related compounds normalized to biomass buming tracers were found in daytime than innighttime, suggesting an importance of photochemical production and degradation in the smokelayers. Higher mass concentrations of S042‑, NH4+ and CH3S03 normalized by K+, levoglucosan,or elemental carbon (EC) in daytime also suggest their photochemical production in biomass
bumingplumes.
Marine aerosols showed the highest mean 815N values of TN (+16.9+4.5Voo) and remained N(+20.2+5.20ho) in summer (June‑August) and the lowest mean 815N values (+12.9+3.40ho,+11.3+5.1%o, respectively) in winter (December‑February). This can partly be explained by anenhanced contribution of 15N‑enriched emissions from agricultural straw buming in a harvest
season (summer and autumn) in China. The mean 815N of removed N showed an opposite trend:
the lowest (+9.2+3.7%o) in warm season (March‑August) and the highest (+14.8+3.8%o) in coldseason (September‑February). These results can be explained by changes in source regions andemission strengths f
rom differ
ent s
ource
s ofnitro
genou
s spe
cies,anddiffe
rencein s
econd
ary .
aerosol nitrogenform
ationbetw
een t
he warm and cold seasons.
In biomass bu
rningaerosols,the815Nvalue
s oftotalnitr
ogen(TN)range
d fro
m +23.5%oto+25.7%o, however, there was no diumal trend. Consecutive day and night samples showed that
813C values of total carbon (TC) were lower in daytime samples,1which can be interpreted as
resulting from higher contributions of refractory TC depleted in 13C mainly due to flaming
combustion. Higher values of 813C and 815N for biomass buming particles than those of unbumedv
egeta
tionrefle
ct positiv
e isotopice
nr
ic
hm
ente
it
herd
urin
gt
hef
or
mat
io
nofpa
rt
ic
leso
raf
tert
hee
missi
on ofparticlesin t
he atmosphere.
This study demonstrates that there are differences in the molecular distributions ofdicarboxylic acids and related compounds between biomass burning and marine aerosols. The
chemical evolution of water‑soluble organics and water‑soluble inorganic ions was observed inboth the marine and biomass burning atmospheres during a long‑range transport.It isclar
ifiedthat biomass buming is a very important source for dicarboxylic acids and relat
ed compoun
ds at
the regional and global scales. The 815
N oftotalnitr
ogen(TN),remainednitrogen (mostly NH4+)
and removed nitrogen (mostly N03') wasfoundto be aneffec
tivetoolto ba
cktra
ck th
e sou
rcesofnitrogenousspec
ies and th
eir a
tmosp
hericproc
essin
g atGosan. Itis demonst
ratedthatthe813
Coftotal carbon (TC) can successfully explain the source of organic carbon formed during biomass
buming processes. It is also proved that the 813C of TC and 815N of TN can together provide
information on their sources and isotopic fractionation that occur during biomass buming.
The commit
tee member
s agr
eed t
hat t
his disser
tatio
n pro
videsnewdatasetsthatare u
seful‑ 1008 ‑for the community of atmospheric chemistry and relevant enwronmental sciences. In particular,
this study demonstrated an importance of photochemical process incont
rolli
ng th
e wat
er‑so
luble
organic aerosols. Thenew observ
ation
s atmarine andtrop
icalforest sit
es together wit
h iso
topic
measurements of carbon and nitrogen have contributed for better understanding the chemical
evolution of organic aerosols in the atmosphere. The thesis has been well written. All thecommittee members agreed to grant the degree to Mr. Shuvashish Kundu.

‑ 1009ー