37

Bulletin of Glaciological Research ,. (,**1) -1ῌ.1
ῌJapanese Society of Snow and Ice

Long-range transportation of contaminants from the Asian Continent
to The Northern Japan Alps, recorded in snow cover on Mt. Nishi-Hodaka-Dake
Kazuhiro TOYAMA+, Hiroshi SATAKE,, Shigeki TAKASHIMA,, Takahiro MATSUDA,,
Motoki TSURUTA, and Kunio KAWADA+ Life and Environmental Science Course, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan, Department of Environmental Biology and Chemistry, Faculty of Science, University of Toyama, Toyama, Japan- Center for Far Eastern Studies, University of Toyama, Toyama, Japan(Received August +-, ,**0; Revised manuscript accepted November 1, ,**0)

Abstract
Vertical proﬁles of chemical components in snow cover at Mt. Nishi-Hodaka-dake, the Northern
Japan Alps, were obtained over three consecutive winters (,**+/*,, ,**,/*- and ,**-/*.) for theinvestigation of long-range transportation of chemical substances from the Asian continent to highmountainous areas in Japan. The d -.S value of non sea-salt (NSS) SO.,῍ ions in ,**,/*- snow was alsomeasured. Concentrations of anthropogenic components such as NSS-SO.,῍ and NO-῍ in snow range
from almost * to over +** meq l῍+. Soil derived components (NSS-Ca,ῌ and NSS-Mg,ῌ) were also
observed in snow, especially in dirt layers, suggesting the transportation of Asian continental desert
dust. The NSS-SO.,῍/NO-῍ (S/N) ratio in snow typically ranges from *.- to 0.-. A considerable
number of samples had higher S/N ratios than those found in Tokyo, Japan (about ,), while somesamples had a much higher ratio (about .ῌ0), more akin to values found in Beijing, China (about .).
Snowfalls at Mt. Nishi-Hodaka-Dake are considered to include acid contaminants transported fromboth the Asian continent and the industrial areas of Japan, with a variable proportion depending on
weather conditions. High S/N ratios seem to be caused by severe winter pressure patterns. The
NSS-d -.S values range from ῌ-῏ to ῌ1῏. These ratios are evidently higher than that a#orded bypetroleum usage in Japan (῍+῏), and is in accord with that of coal used in both northern China(ῌ1..῏) and the Russian Far East (ῌ-..῏). These d -.S values also suggest the occurrence oflong-range transportation of NSS-SO.,῍ from the Asian continent, independent of chemical composition.

+.

Introduction

The mountainous area known as the Northern
Japan Alps is located in the northern central part ofHonshu Island, Japan. In this area, heavy snowfalls
frequently occur during the winter season, and thisremains as snow cover until the spring. This is possible because the air temperature in this high mountainous area stays well below *῎ throughout the entire
winter season. Therefore, this snow cover can be regarded as a continuous precipitation sample for theperiod between late autumn and early spring.
In high mountainous areas, the lack of a local
pollution source means that the snowfall provides agood sample to study the general trend of the atmospheric environment indicative of the winter period.

It is well known that during winter, chemical substances including acidic components (e.g. SO.,῍), aretransported in the atmosphere from the Asian continent to Japan’s coastal area along the Sea of Japan(e.g. Satake and Yamane, +33,). These pollutants
may also be transported to the mountainous regions
set back from the coastal area, and may inﬂuence thehigh mountain environment. Therefore, the investigations of these possibilities are important subjects.
Nakagawa et al. (+310) performed the ﬁrst studiesof the physical properties of snow cover at Mt. Tateyama,in the Northern Japan Alps. This was followed a few
years later by a second investigation in the same areaon the chemical analysis of snow cover performed by
Kusakabe and Satake (+32-). Since the +33*’s, detailed
chemical observations have been repeatedly performed at Mt. Tateyama (e.g. Osada et al., ,***; Kido

38

Bulletin of Glaciological Research

et al., ,**+; Osada et al., ,**.; Watanabe et al. ,**/).
However, chemical investigations of the snow coverin the Northern Japan Alps reveals that except for the
Mt. Tateyama area, the overall results for this mountainous region are still insu$cient to provide a detailed chemical analysis of the snow covers.
We investigated the chemical and isotopic compositions of the snow cover at Mt. Nishi-Hodaka-dake(located /* km inland from Mt. Tateyama) in order toclarify whether anthropogenic substances are transported inland to the high mountainous areas of thisregion, and ultimately, the origin of these pollutants.
Tsushima and Hirata (+333) previously measured thechemical composition of various snow cover samples
at Mt. Nishi-Hodaka-dake. However, these measurements were performed intermittently, and as such,
this investigation may miss the existence of anthropogenic substances. The uninterrupted results collected by Toyama et al. (,**-) are considered a better
representation of the chemical composition of the,**,/*- winter snow samples collected at Mt. NishiHodaka-dake. The authors report however, thatthese results only represent one winter season, andtherefore cannot be regarded as representative of thisarea.
In this study, the chemical components in snow
samples from three consecutive winter seasons (,**+/*,, ,**,/*- and ,**-/*.) were measured in order toinvestigate how the long-range transportation of chemical substances from the Asian continent to Mt.
Nishi-hodaka-dake varies from year to year, depending on the weather conditions. Further, the sulfur
isotope ratio of the ,**,/*- snow cover was also measured to clarify the source areas of the SO.,῍ ions,through independent methods of chemical composition.

,.

were then collected from the surface of the wall using
a snow sampler. These snow samples were collected
continuously from the lower section of the pit to thesnow surface. Samples were then packed into plastic
bags, and sealed and stored below *῏ to keep thesamples in the solid state and to prevent alternation of
the chemical composition by microbial activity.
The samples were melted under laboratory conditions, and their chemical compositions (anions: F῍,
Cl῍, NO-῍ and SO.,῍; cations: Naῌ, NH.ῌ, Kῌ, Mg,ῌ andCa,ῌ) analyzed by ion chromatography (anions: Metrohm Compact IC 10+, cations: TOSO IC-2*+*). The
accuracy of the measured values was around῎/ῌ.
For the measurement of the sulfur isotope ratio(d -.S), another series of samples were collected at thesame sampling point used for chemical analysis, taken
3 days earlier (+*th March ,**-). The snow depth on+3th March ,**- was -00 cm, which was slightly shallower than the snow depth, .,* cm, measurement
taken on +*th March ,**-. This decrease in snow
depth is considered to be due to compaction of thesnow cover, resulting from a slight melting of thesnow layer over the 3-day period.
Snow samples obtained from mountainous regions generally have a very low SO.,῍ concentration
around + mgl῍+ (e.g. Tsushima and Hirata, +333; Osadaet al., ,***), such that a quantity of SO.,῍ of more than+ mg is needed in order to obtain meaningful d -.Smeasurements. Therefore, a large volume of eachsnow sample more than , l in water equivalent isrequired for one d -.S datum. Snow samples for d -.S
analysis were collected from a single homogeneous
snow stratum. Since a homogeneous snow stratum
can be regarded to pile up during a single snowfall
event resulting in a homogeneous d -.S value, +, separate samples were collected continuously from thelower section of the pit to the snow surface. Samples

MethodSnow samples for chemical analyses were collected (,*th March ,**,, +*th March ,**- and ,,nd March,**.) at a sampling point ,/* m east of the NishiHodaka-Guchi station of the Shin-Hodaka Ropeway,
Sengoku Ridge of Mt. Nishi-Hotaka-Dake (,,** m A.M.
S.L.; Fig. +). The topography around the sampling
point was ﬂat, such that the snow depth at the sampling point is considered representative of the snow
depth in this area. Further, sheltering by neighboring trees and buildings, and public contamination arenecessarily avoided around the sampling point, suchthat the obtained results are representative of a contamination-free region. A snow pit was dug, where
the walls of the pit were carefully smoothed to leave
the stratigraphy of the snow layer undisturbed. The
conditions of the snow layer (e.g. snow type and particle size) in the pit were then studied. Snow samples(width of /.2 cm, depth of /.2 cm and height of - cm)

Fig. +. Location map of Mt. Nishi-Hodaka-dake where
snow samples were collected. The sampling point(,,** m A.M.S.L.) is located ,/* m east of the
Nishi-Hodaka-Guchi station of the Shin-Hodaka
Ropeway, at the Sengoku Ridge of Mt. NishiHotaka-Dake.

Toyama et al.

were sealed into plastic bags, and then transported to
the laboratory and stored below *῔. The samples
were then melted under room temperature conditions,ﬁltered, and then concentrated the samples to about 1
times using a rotary evaporator. A BaCl, solution
was added to the concentrated aqueous sample solution to induce the formation of sulfate ions, recovered
as BaSO.. The recovered BaSO. was then mixed with
V,O/ and heated to form SO, gas (Yanagisawa andSakai, +32-).
The d -.S value of the SO, gas was measured using
a mass spectrometer (Micromass PRISM model). The
d -.S value is expressed as the following equation using Canyon Diablo Troilito (CDT) as a standard material:d Sΐ῎ῌ Sῌ S῍sampleῌῌ Sῌ S῍CDTῑ+῏ῒ+*
-.

-.

-,

-.

-,

-

(+)

To obtain the non sea-salt (NSS) d -.S values, theconcentrations of Naῐ, Clῑ and SO.,ῑ ions in the snow
samples were also measured.

Results and discussion-.

Condition of snow layers
An outline of the stratigraphies of snow cover ineach year is shown in Fig. ,. Here, most of the layers
were composed of compacted snow or solid-type depthhoar, where no melted water was detected. Therefore, it can be regarded that the snow layers maintained their original chemical and isotopic composi-.+

39

tions at the time of snowfall. The observations of
granular snow suggests that the occurrence of melted
water were exceptionally detected at the height of +//ῌ,+, cm and -+-ῌ-,1 cm in the ,**,/*- snow cover and,2/ῌ-** cm in the ,**-/*. snow cover.
-., Vertical proﬁle of chemical composition
To evaluate the contributions of anthropogenic orsoil contamination to the snow chemistry, it is important to determine the calculation of NSS-components.
The non sea-salt component can be obtained from thefollowing equation using chemical compositions insnow samples and seawater (Berner and Berner, +321):
῎NSSῑA῏snowΐ῎A῏snowῑ῎AῌNaῐ῏seawaterῒ῎Naῐ῏snow(,)
A: SO.,ῑ, Mg,ῐ, Ca,ῐ and Fῑ
In this study, the non sea-salt components were
calculated for SO.,ῑ, Mg,ῐ, Ca,ῐ and Fῑ ions. All theNO-ῑ components can be regarded as NSS-components, because the concentration of NO-ῑ ions in surface seawater is very low. In all the snow samples,
more than 33ῌ of the Fῑ ions were of NSS-origin, suchthat all of the Fῑ ions in snow can also be regarded as
NSS-components.
In Fig. -, the vertical proﬁles of chemical compositions taken during the ,**+/*,, ,**,/*- and ,**-/*.
snow covers are shown. The maximum, minimum
and mean concentrations of each snow cover are

Fig. ,. The stratigraphies of snow cover at the sampling point observed on ,*th March ,**,, +*th March ,**- and ,,ndMarch ,**.. Arrows on the right side of each stratigraphic plot show dirt layers caused by Asian dust (KOSA).

40

Bulletin of Glaciological Researchshown in Table +. The concentration of individualcomponents changes about +** times depending on
the layer studied. In each of the vertical proﬁlesshown in Fig. -, there are several peaks that representhigh concentration. In the NSS-SO.,῍ and NO-῍ proﬁles, for example, such peaks are found at +0, cm, ,.3
cm and -,1 cm during the ,**+/*, period, +0/ cm and-*3 cm during the ,**,/*- period, and 1,cm and +32cm
during the ,**-/*. period. From Fig. -, it is also
found that several chemical components are repre-

sented simultaneously.
In general, the source of the chemical components
in snow can be classiﬁed into three origins: +) sea-salt
components, ,) soil components and -) anthropogenic
components. The characteristics of each component
are as follows.
Sea-salt components
As shown in the Cl῍ versus Naῌ plot diagram in
Fig. ., most snow samples are closely distributed-.,.+

Fig. -. Vertical proﬁles representing chemical components in the snow cover samples taken from Mt. Nishi-Hodaka-dake,
during the winters of ,**+/*,, ,**,/*- and ,**-/*.. Proﬁles of NSS-SO.,῍, NSS-Mg,ῌ and NSS-Ca,ῌ represent the nonsea-salt (NSS) compositions in each component. Arrows on the right side of NSSῌCa,ῌ proﬁle reveal the dirt layers.

Toyama et al.

along the line showing a Cl῍/Naῌ ratio in seawater.
Therefore, the Naῌ and Cl῍ ions can be regarded to beof seawater origin. The concentrations of Naῌ andCl῍ ions in snow were *ῌ2* meq l῍+ and *ῌ+21 meq l῍+,
respectively. These values are extremely low in comparison with the mean concentration of winter precipitation taken from ,3 cities along the Sea of Japan(Naῌ : ,2, meq l῍+, Cl῍ : --+.- meq l῍+; Fukuzaki et al.,+330). It is known that the Cl῍ ion concentration inprecipitations exponentially decreases with increas
ing distance from the seashore (Tsunogai, +31/; Suzuki,+321). Therefore, the greater part of these two components in cloud probably fell in coastal areas, withvery little arriving in the high mountainous areas.
As described above, most snow samples are distributed along the seawater line in the Cl῍ versus Naῌdiagram (Fig. .). However, the snow samples withCl῍ ion concentrations greater than ,* meq l῍+ are plotted slightly above the seawater line. This suggeststhat such snow samples also contain small amounts ofCl῍ ions of non sea-salt origin. It is reported thatanthropogenic or volcanic Cl῍ ions occur in the atmosphere (Okita et al., +31.). Anthropogenic Cl῍ ionsare exhausted from inclination facilities for household
and industrial wastes in the form of HCl (Tsuruta,+323).
Soil components
The concentration of NSS-Ca,ῌ ions is represented by peaks corresponding to the dirt layers (seeFig. -). These dirt layers in the snow cover are thought to be caused by Asian dust (KOSA) blown overfrom the deserts of northwestern China (Kido et al.,+331). This suggests that high NSS-Ca,ῌ ion concentrations in the dirt layers were caused by the dissolu-

41

tion of calcium carbonate (CaCO-), which is a major
component of Asian dust. Moreover, NSS-Ca,ῌ ionsare constantly detected in samples extracted from thedirt layers. Kumai (+3/+) and Ishizaka (+31-) pointed
out that in the case of winter precipitation in the
coastal area along the Sea of Japan, most of the ice
nuclei are soil particles transported from the Asian
continent. Further, Iwasaka et al. (+322) reported
that a background amount of Asian dust always exists in the troposphere over Japan. Therefore, thelower concentration of NSS-Ca,ῌ ions observed in-.,.,Fig. .. Cl῍ versus Naῌ plot of snow samples takenover three winters (,**+/*,, ,**,/*- and ,**-/*.).
The dashed line represents the ratio of concentrations in seawater. Most of the snow samples areclosely distributed near the seawater line.

Table. +. Maximum, minimum, and average concentrations, and total deposition of chemical components in the ,**+/*,,,**,/*- and ,**-/*. snow cover samples taken at Mt. Nishi-Hodaka-dake.

42

Bulletin of Glaciological Research

Fig. /. Naῌ versus Mg,ῌ (bulk) plot of snow samples
taken over three winters (,**+/*,, ,**,/*- and,**-/*.). The dashed line represents the ratio ofconcentrations in seawater. Most of the snow samples are plotted above the seawater line.

Fig. 0. NSS-Ca,ῌ versus NSS-Mg,ῌ plot of snow samples taken over three winters (,**+/*,, ,**,/*- and,**-/*.). A high positive correlation was foundbetween the two parameters.

non-dirt layers can also be regarded as derived from
Asian dust.
Most of the snow samples are plotted above theseawater line in a plot of Mg,ῌ versus Naῌ (Fig. /).
Further, in snow samples, a positive correlation (R῎*.0) was found between the NSS-Ca,ῌ and NSS-Mg,ῌ
ions (Fig. 0). This suggests that the Mg,ῌ ions insnow are mostly composed of soil-derived and sea-salt
components; although in coastal areas most Mg,ῌ ionsin precipitation are of sea-salt origin. The soil transported from the Asian continent can be regarded as adominant source of NSS-Mg,ῌ and NSS-Ca,ῌ ions inthe snow cover found at Mt. Nishi-Hodaka-dake.
-.,.- Anthropogenic components
NSS-SO.,῍ values of * to ++, meq l῍+ and NO-῍values of * to ++, meq l῍+ are observed in the snowfall
at Mt. Nishi-Hodaka-dake. The maximum concentrations of NSS-SO.,῍ and NO-῍ ions in Mt. Nishi-Hodakadake snowfalls are comparable to those found in precipitations in urban areas (e.g., Fukuzaki et al., +330).
Osada et al. (,***) also observed similar concentrations of acid components in snow samples taken at
Murodo-daira (,./* m), an area in Mt. Tateyama ofsimilar altitude and located much closer to the Sea ofJapan. The NSS-SO.,῍ and NO-῍ ions are typical anthropogenic components derived from exhaust gas orindustrial activity. These ions are major acidifying
materials found in precipitation. As Mt. NishiHodaka-dake is surrounded by forest, there are no
local sources of acid contaminants. Therefore, it issuggested that these acid components were transported from distant sources. It is well known thatacid contaminants originating from the Asian continent are transported to the coastal area along the Sea
of Japan by winter seasonal winds (e.g. Satake andYamane, +33,). In this respect, we must examine thepossibility that these long-range transported acidcomponents may arrive at inland mountainous areas,such as Mt. Nishi-Hodaka-dake.
The high concentration peaks of the NSS-SO.,῍
and NO-῍ ions are often accompanied by peaks associated with NSS-Ca,ῌ ions (e.g. ,.3 cm and -,1 cm takenfrom snowfalls in ,**+/*,, +0/ cm, respectively, and-*3 cm from snowfalls in ,**,/*-; see Fig. -). Thisobservation does not contradict the possibility thatacid components exhausted in China are transported
simultaneously with Asian dust, although anotherpossibility that SO.,῍ ions discharged from the coastal
area along the Sea of Japan were transported with
Asian dust cannot be excluded. Moreover, F῍ ionswere also detected in snow samples. The concentration of F῍ ions is *ῌ2 meq l῍+ with an average of about+ meq l῍+, which is much lower than the NSS-SO.,῍ andNO-῍ ion concentrations. However, as shown in Fig.
-, the vertical proﬁles of F῍ ions were partially similar
to those of the NSS-SO.,῍ ions. Sakamoto (+33.a)pointed out that F῍ ions are discharged as HF as aresult of coal combustion in China. So, it may be
regarded that the detected F῍ ions were probably
includes anthropogenic F῍ ions that transported fromthe Asian continent.
NSS-SO.,῍/NO-῍ ratio in snow
To investigate the source of anthropogenic
NSS-SO.,῍ and NO-῍ ions in snow cover, the relation
between NSS-SO.,῍ and NO-῍ ions will be consideredin this section. NSS-SO.,῍ versus NO-῍ plot of samples is shown in Fig. 1, and the corresponding histo-.-Toyama et al.

gram of NSS-SO.,ῌ/NO-ῌ ratio in eq lῌ+ units (S/Nratio) is shown in Fig. 2. The S/N ratios in Beijing,
China (in +32/ῌ20; Sakamoto, +33.b) and Tokyo, Japan(in +32.ῌ22; Mori et al., +33+) are also shown in Figs. 1
and 2, respectively. Most of the snow samples obtained during ,**+/*, and ,**,/*-, and half of thesnow samples taken in ,**-/*., are distributed between the lines showing S/N ratios in Beijing andTokyo (Fig. 1 and Fig. 2).
In China, the principal energy source coal accounts for 0/ῌ of the total energy, while petroleum
accounts for ,.ῌ in ,**+ (National Bureau of Statisticsof China, ,**.). On the other hand, in Japan, /*ῌ ofthe total energy is supplied by petroleum, while coalaccounts for just ,*ῌ in ,**+ (Statistics Bureau, Ministry of Internal A#airs and Communications, Japan,,**0). In comparison with petroleum, coal has a somewhat higher content of sulfur. So, in China, the total
discharges of sulfur dioxide and nitrogen oxide are,*.* and 1.. million tons in +321 (Kato et al. +33,),
discharge of sulfur dioxide is relatively higher thanthat of nitrogen oxide. In Japan, as described above,the major energy source is petroleum. Furthermore,desulfurization equipment is installed in power plants
and large-scale factories in Japan. As a result, theamounts of sulfur dioxide and nitrogen oxide exhausted are *.3 and ,.* million tons, respectively in,**, (OECD, ,**/). So, the S/N ratio, in equivalent, in
China (about .) is much higher than that in Japan(about ,).
Consequently, the results in Fig. 1 and Fig. 2 suggested that acid contaminants in the snow cover at
Mt. Nishi-Hodaka-Dake comprised a mixture of contaminants from both China and Japan with variableratio. Thus, it is clear that the acid components transported from the Asian continent reached Japan’s

43

Fig. 2. The histograms of NSS-SO.,ῌ/NO-ῌ (S/N) ratios
in the ,**+/*,, ,**,/*- and ,**-/*. snow coversamples taken at Mt. Nishi-Hodaka-dake. The S/Nratios in precipitations taken at Beijing, China in+32/ῌ20 (Sakamoto, +33.b) and Tokyo, Japan in+32.ῌ22 (Mori et al., +33+) are also shown in the
diagram.

Fig. 1. NSS-SO.,ῌ versus NO-ῌ plot of snow samples taken over three winters (,**+/*,, ,**,/*- and ,**-/*.). The dashedlines showing the SO.,ῌ/NO-ῌ ratios in precipitations taken at Beijing, China in +32/ῌ20 (Sakamoto, +33.b) and Tokyo,
Japan in +32.ῌ22 (Mori et al., +33+) are also shown in the ﬁgures.

44

Bulletin of Glaciological Researchinland high mountainous areas, such as Mt. NishiHodaka-Dake, located 1* km inland from the coastlineof the Sea of Japan.
However, from a comparison of snowfall datataken over a period of three years, the situation of
long-range transportation seems to be di#erent fromyear to year. The total depositions of NSS-SO.,ῑ andNO-ῑ ions in snowfalls in ,**+/*, are +.03 g mῑ, and*.3* g mῑ,, respectively. The depositions observed in,**+/*, are systematically larger than those in snowfall samples in ,**,/*- (NSS-SO.,ῑ: +.+, g mῑ, andNO-ῑ: *./2 g mῑ,) and in ,**-/*. (NSS-SO.,ῑ: +.*3 g mῑ,and NO-ῑ: *.1. g mῑ,). From Fig. 1, it is observed thatin the snow sample of ,**+/*,, the S/N ratio is widelydistributed from + to 0, although a weak peak is observed at +.2. On the contrary, in the snowfall samples of ,**,/*- and ,**-/*., there are conspicuous
peaks around - and ,, respectively. This ﬂuctuation
among three winter seasons may be caused bychanges in the transportation situation of acid components, which may depend on the weather condition
observed during each winter season. Figure 3 shows
the vertical proﬁles of S/N ratios, which consider aﬁve point moving average value, in snow cover. The
temporal variation in the S/N ratio, and the generalweather conditions experienced in each of the years(Japan Meteorological Agency, ,**0), may control the
long-range transportation of NSS-SO.,ῑ ions, as follows.
,**+/*, winter season
A series of typical winter pressure patterns, characterized by high-pressure in the west and lowpressure in the east, were frequently observed during
December ,**+. The transportation of substancesfrom the Asian continent can be considered active
during this period. As such, the lower section ofsnow cover (*ῌ/* cm), which was observed to havehigher S/N ratios (..*ῌ0.*), may correspond to thisperiod. During the period between January ,**, andMarch ,**,, the weather condition changed repeatedly from severe winter pressure patterns to southerncoast low-pressure patterns, which are characterized
by low-pressure areas moving along the southerncoast of the Japan Islands. The S/N ratio in the /*ῌ
--* cm range of the snow cover samples ﬂuctuatedfrom *.1 to 0.+. This ﬂuctuation in the S/N ratio
seems to be induced by the repeated weather condition changes during January-March ,**,. The total
deposition of NSS-SO.,ῑ ions (see Table +) in the ,**+/*, snow season is among the highest of the three
winter seasons. Therefore, it is considered that thetransportation of contaminants from the Asian continent during the ,**+/*, winter period was the mostactive among the three winter seasons.
-.-.+

-.-.,

,**,/*- winter season

From December ,**, to February ,**-, the winterpressure pattern and southern coast low-pressure pattern appeared alternately. The S/N ratio in *ῌ-** cmof contaminants changes periodically from *.- to 0.-,which may be a reﬂection of the weather situation.
In March ,**-, the winter pressure pattern intensiﬁed.
The S/N ratio in the upper part of the snow cover (-,*
ῌ.** cm) is relatively high (-ῌ.). This high S/N ratio
may reﬂect the severe winter which occurred in
March ,**-. The concentration of chemical components in the snow cover that fell during the ,**,/*period is low relative to the snowfall periods in ,**+/*, and ,**-/*.. This may be the result of dilution by
the large accumulation of snow (.,* cm), which is thehighest among the three periods of snowfall (,**+/*,:--* cm and ,**-/*.: -*3 cm).
,**-/*. winter season
The winter pressure pattern from December ,**to February ,**. was found to be weak. The observed low S/N ratio (around ,) in *ῌ,** cm may be areﬂection of this weak winter pressure pattern, which
was observed to intensify in the early part of March,**.. A high S/N ratio (over .) observed in ,**ῌ,,*cm and ,/*ῌ,0* cm may be induced by the intensiﬁed
winter pressure pattern. The total deposition of
NSS-SO.,ῑ (+.*3 g mῑ,) ions was the lowest among
three winter seasons (,**+/*,: +.03 g mῑ, and ,**,/*-:+.+, g mῑ,). This suggests that the transportation ofcontaminants from the Asian continent was not active during the ,**-/*. winter.
Through the observation of three snow seasons, it
is revealed that the long-range transportation of chemical substances from the Asian continent is closely
related to the winter weather conditions. The combination of detailed dating of the snow layers (e.g.
Toyama et al., ,**/) with the corresponding chemical
analyses of snow may remarkably improve the investigation of the long-range transportation of anthropogenic contaminants from the Asian continent.
-.-.-

Sulfur isotope ratio (d -.S)The d -.S values of the ,**,/*- snow samples were
measured for the independent evidence for determining the origin of NSS-SO.,ῑ ions. As described previously, snow contains SO.,ῑ with sea-salt origin, although most of the SO.,ῑ (about 3*ῌ) ions are of non
sea-salt origin. To determine the d -.S value of
NSS-SO.,ῑ in snow, we must calculate the NSS-d -.Svalues using the following equation:-..

NSSῑd-.Sΐῌd-.Ssampleῒ῎SO.,ῑsample῏
ῑd-.Sseaῒ῎SO.,ῑsea῏῍ῌ῎SO.,ῑNSS῏ (-)
d -.S value of SO.,ῑ in seawater (d -.Ssea) is reported tobe ῐ,*.*῔ (Rees et al., +312).
Vertical proﬁles of the NSS-d -.S value and the S/Nratio are shown in Fig.+*. The proﬁle of the S/N ratioToyama et al.

for snow collected in +3th March ,**- was obtained by
reducing the height of the S/N ratio proﬁle of the,**,/*- snow collected on the +*th March ,**-. Since
the snow cover collected on the +3th March ,**- can be
regarded as a homogeneously-compressed version of
the snow collected on +*th March ,**-.
The NSS-d -.S values range from ῌ-.+ to ῌ0.2ῐ
with an average of ῌ..3ῐ. The highest NSS-d -.Svalue in the *ῌ-** cm section of snow cover ﬂuctuatedperiodically from ῌ../ to ῌ/./ῐ, although the highest
value, ῌ0.2ῐ, is found in the section ++*ῌ+0* cm. In
the upper part, -**cm to the surface, the NSS-d -.Svalue gradually decreased from ῌ..*ῐ to ῌ-.*ῐ withincreasing height.
In winter, the northwest wind blows from the
Asian continent to the Japan Islands. So it is expected that a considerable amount of NSS-SO.,῍ ions
was transported from the northern part of China andthe far eastern part of Russia. Maruyama et al. (,***)
measured the d -.S values of coals used in East Asia.
They obtained d -.S values of ῌ1.2῎++.*ῐ in northern
China and ῌ../῎..2ῐ in the Russian Far East. Furthermore, Maruyama et al. (,***) pointed out that thed -.S value of petroleum used in Japan is about ῍+ῐ.
The NSS-d -.S value of snow at Mt. Nishi-Hodaka-dakeis around ῌ/ῐ, and was obviously higher than that ofdomestic petroleum (῍+ῐ), and much closer to thevalue of coals mined in northern China. Thus, the
NSS-SO.,῍ ion contribution from the Asian continent
to Mt. Nishi-Hodaka-dake is also observed, based on
the sulfur isotope ratio.

45

In the major part of the snow, the S/N ratio and
NSS-d -.S value seem to ﬂuctuate in parallel. These
two parameters show weak positive correlation (R῏*.,). This suggests that in the periods of higher S/Nratios (e.g. samples No. ., /, 0, +* and +, in Fig. 3), thetransportation of contaminants from the Asian continent is active; NSS-SO.,῍ with high NSS-d -.S weretransported from northern China. There is a possibility that sample No.+* with the highest NSS-d -.Svalue, contains NSS-SO.,῍ ions derived from around
Beijing; an area known to have the highest d -.S value(av.: ῌ3.0῎+*.2ῐ; Motoyama et al., ,**,) in China.
On the contrary, in the periods with lower S/N ratios,
the transportation of contaminants from the Asian
continent is not active, and the observation of domestic NSS-SO.,῍ ions with low NSS-d -.S values is dominant in the snow samples. Samples No. ,, - and ++are representative of this period.
However, sample No.+ has a high S/N ratio (,.2)
and the lowest NSS-d -.S value (ῌ-.+ῐ). Maruyama
et al. (,***) described that the average d -.S value ofcoal in southern China is ῍1ῐ, and the sulphur concentration of coals in southern China is higher thanthat of coals in northern China. There is a possibility
that NSS-SO.,῍ ions in sample No.+ with a high S/Nratio (,.2) and low d -.S value (ῌ-.+ῐ) may include
NSS-SO.,῍ ions derived from southern China. On thecontrary, samples No.1 and 2 have low S/N ratios (,.and ,./), although its NSS-d -.S value is high (ῌ/.0ῐ).
The major energy sources in the Russian Far East
(Russian Academy of Sciences Far East Branch, ,**+)

Fig. 3. Vertical proﬁles of the S/N ratio (ﬁve points moving average) in the ,**+/*,, ,**,/*- and ,**-/*. snow coversamples taken at Mt. Nishi-Hodaka-dake.

46

Bulletin of Glaciological Research

are coal (ca. ./ῌ), petroleum (ca. -.ῌ) and natural gas(ca. +*ῌ). Therefore, the S/N ratio of the Russian Far
East can be considered to be intermediate between
China and Japan. Further, the NSS-d -.S value in the
Russian Far East (av.: ῌ../῎..2῏) is lower than thatin northern China, but much higher than that inJapan. Considering these facts, NSS-SO.,῍ ions insamples No.1 and 2 with low S/N ratios and highNSS-d -.S values may include NSS-SO.,῍ ions derived
from the Russian Far East.
The relationship between S/N ratio and NSS-d -.Svalue in each sample is shown in Fig.++. From thisﬁgure, NSS-SO.,῍ ion in snow seems to be transported
from four areas, that is, northern China, southern
China, Russian Far East and Japan. Then NSS-SO.,῍

Fig. +*. Vertical proﬁles of the NSS-d -.S and S/N ratios in the snow cover samples taken at Mt. NishiHodaka-dake, collected in +3th March ,**-.

from thesse four areas was mixed with variable proportion depending on weather condition, and was transported to Mt. Nishi-Hodaka-Dake. Dense NSS-d -.Smeasurement by short sampling interval may makethe origin of acid contaminants clear.

..

Conclusions(+) The chemical components in snow cover at Mt.
Nishi-Hodaka-dake in the Northern Japan Alps were
measured over a period of three consecutive (,**+/*,,,**,/*-/ and ,**-/*.) winter seasons. The concentrations of NSS-SO.,῍ and NO-῍ ions in this snow
cover ranged from almost * meq l῍+ to over +** meq l῍+.
The maximum concentrations over +** meq l῍+ arecomparable to concentrations in precipitations monitored in urban areas.
(,) A considerable number of snow samples takenfrom this region had higher S/N ratios than that ofTokyo, Japan (about ,). Some samples had muchhigher S/N ratios (about . to 0), which is the same as
the S/N ratio of Beijing, China. This suggests thatthe snow cover at Mt. Nishi-Hodaka-Dake includes
acid contaminants transported from the Asian continent, as well as those of domestic origin with variable
proportion depending on weather conditions. Throughthe observation of three snow seasons, it is revealed
that the long-range transportation of chemical substances from the Asian continent is closely related to
the winter weather conditions.
(-) The NSS-d -.S values range from ῌ-῏ to ῌ1῏(average: ῌ..3῏). These ratios are evidently higher
than those associated with the amount of petroleum
used in Japan (῍+῏). The NSS-d -.S values in snow
samples are in accord with the d -.S values of coal usedin northern China (ῌ1.2῏), which are located on thewindward side of the winter seasonal winds. Thissulfur isotopic result also shows the long-range trans-

Fig. ++. S/N ratio versus NSS-d -.S plot of snow cover sample collected from
Mt. Nishi-Hodaka-dake, on +3th March ,**-.

Toyama et al.

portation of NSS-SO.,῍ ions from the Asian continent,
independently of the S/N ratio.
(.) The NSS-d -.S value in snow cover shows positive
correlation with the S/N ratio, suggesting a contribution of NSS-SO.,῍ ions from northern China. However, there were some exceptional cases, which seemto suggest the transportation of NSS-SO.,῍ ions fromsouthern China and the Russian Far East.

Acknowledgments
The authors wish to thank to Prof. Morioka (University of Toyama) for his kind explanation of Russian
documents. We are also grateful to Dr. Suzuki(Yamagata University), editor of Bulletin of Glaciological Research, and an anonymous reviewer for
their valuable advices and comments. We would liketo thank the members of Laboratory of Environmental Geochemistry and Laboratory of Glaciology, University of Toyama, for their assistance with the snow
observations and collections under severe weather
conditions at Mt. Nishi-Hodaka-Dake.

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