Bulletin of Glaciological Research ,0 (,**2) 3ῌ+.
ῌJapanese Society of Snow and Ice

9Chemical dynamics of snowpack in the Northern Japan Alps during snowmelt season
Shailendra Kumar SHAH+, Motoki TANAKA,, Takayuki KURAMOTO+ and Keisuke SUZUKI+, ,+ Correspondence to: Department of Environmental Science, Faculty of Science, Shinshu University, Asahi, Matsumoto, -3*-20,+,
Japan, Correspondence to: Institute of Mountain Science, Shinshu University, Asahi, Matsumoto, -3*-20,+, Japan(Received February ,-, ,**2; Revised manuscript accepted May +., ,**2)

Abstract
A snow pit study was conducted on Mt. Norikura in the Northern Japan Alps from January to
April ,**1 to clarify the chemical dynamics in the snowpack during the snowmelt season. Little
snowmelt occurred before February 0, the ﬁrst snowmelt occurred between February 0 and ,+, and thepeak of the snowmelt season occurred after March 1. Snow layers with remarkably high Cl῍, NO-῍,
and SO.,῍ concentrations in the snowpack were traced; furthermore, the snow layers with high SO.,῍
concentrations were found to disappear ﬁrst. It was concluded that the ease with which the ions were
ﬂushed out from the snowpack was SO.,῍῏NO-῍῎Cl῍.

+.

Introduction

In recent years, acid precipitation has been observed all over the world. The e#ects of acidic precipitation on inland water ecosystems across themany lakes of Scandinavia and eastern Canada havebeen reported (Gorham, +30+; Minns, +32+). And thepH of snowmelt water in particular has been reported
to be extremely low. Therefore, it is important tounderstand the behaviors of anions in snowmelt water and the snowpack during the snowmelt season.
Before snowmelt, the concentration of dissolved
ions in the snowpack is the same as that in the snow.
However, these ions ﬂow out with the snowmelt water
during the snowmelt season. The concentration ofthese ions in the snowmelt water is high early in thesnowmelt season, and it lowers as snowmelt progresses (Johannessen and Henriksen, +312; Jones andDeblois, +321). This is explained by the fact that theions in a snow particle are released to the surface ofthe snow particle during the process by which ittransforms into a granular snow particle in the snowpack; this phenomenon is due to the di#erence infreezing point between pure water and water containing dissolved ions. Thus, the snowmelt water thatﬂows over the surface of the snow particle selectively
dissolves the ions, leading to a higher concentration insnowmelt water than in the snowpack (Suzuki, +32,).
Suzuki (+33+) reported that the snow particles that
constitute the snowpack release the ions to their surfaces during melting/refreezing cycles.

Since di#erent ions will separate from snow particles at di#erent rates, there must be a certain orderin which the ions are ﬂushed out of the snowpack;there have been some reports on this phenomenon(Brimblecombe et al., +32/; Iizuka et al., ,***). For example, Suzuki (+33+) measured the daily variation of
the anionic components in snowmelt water; he foundthat when refreeze occurred at the surface of thesnowpack in the early morning, the ratios of SO.,῍
and NO-῍ were high, and by day the ratio of Cl῍ washigh. This results suggested that the order of theease with which ions were ﬂushed was SO.,῍῎NO-῍῏Cl῍. Brimblecombe et al. (+32/) conducted snow pit
work on two consecutive days in Scotland and compared the order in which di#erent ions were ﬂushedfrom the snowpack with the snowmelt. His results
suggested that the order of the ease with which ionswere ﬂushed was SO.,῍῏NO-῍῏NH.ῌ῏Kῌ῏Ca,ῌ῏
Mg,ῌ῏Hῌ῏Naῌ῏Cl῍. Davies et al., (+321) experimentally deﬁned the order of the ﬂush of each ion andreported it as Ca,ῌ῎Mg,ῌ῏SO.,῍῏NO-῍῏Naῌ῏Cl῍.
Thus, each preceding report has indicated di#erent
orders and there is no uniﬁed opinion.
In most of the low-lying areas of Japan, snowmelts are frequent, even in the winter season. In
contrast, in the high mountainous areas of Japan,
snowmelts seldom occur. The chemical substances
in a snowpack burst out intensively during the snowmelt season. In other words, the chemical dynamics inthe snowpack in high mountainous areas during thesnowmelt season are more conspicuous than those in
the low-lying areas. The object of this study is to10

Bulletin of Glaciological Researchclarify the chemical dynamics in the snowpack occurring in a mountainous area and the order in which
di#erent ions are ﬂushed from the snowpack during
the snowmelt season.

,.

Methods

The study site in this research is located at analtitude of +/3* m on the eastern side of Mt. Norikura(-*,0 m), which is in the southern part of the Northern
Japan Alps in central Japan (Fig. +). The timberlineof Mt. Norikura is located at an altitude of approximately ,./* m. A major portion of Mt. Norikura below the timberline is covered with deciduous andconiferous forest. The mean air temperature recordedby the weather observation system that was set up at
the study site was ῍+.1῎ and the total precipitation
at the study site was /+3 mm during JanuaryῌApril,**1 (the snowy season).
Snow pit sampling was conducted during JanuaryῌApril ,**1. The sampling was conducted a totalof nine times at a frequency of two or three times permonth from early in the formation of the snowpack
until its disappearance.
The sampling was conducted in ﬂat and open
spaces selected by observation at the site: The snow
pits were dug through the entire snowpack, the physical stratigraphy was observed, and the snow temperature was measured at --cm intervals of increasing
depth; further, the density (+** cm-) was recorded andsnow samples were collected at each --cm interval.
These measurements were conducted through the entire snowpack. A new snow pit was dug each snow
pit work. The snow samples were placed in vinyl
bags (NASCO: WHIRL-PAK) and melted in a cleanroom. The pH (DKK-TOA: GST-/.,*C) and electric
conductivity (DKK-TOA: CT-2.+*+B) were measured
after ﬁltration through a PTFE membrane ﬁlter with

Fig. +.

Study site.

a pore size of *../ mm; the concentrations of the dissolved substances (Naῌ, NH.ῌ, Kῌ, Mg,ῌ, Ca,ῌ, Cl῍,
NO-῍, SO.,῍) were measured by the suppression method using an ion chromatograph (DIONEX: DX-/**).
A weather observation station was set up near thesnow pit sampling points for automatic measurements (KONA System: KADEC-Me-N). Air temperature was measured by a ventilated-type temperature
sensor; snow depth, by a snow-depth gauge; and precipitation, by a tipping-bucket rain/snow gauge.

-.

Results and Discussion-.+

Source of chemical substances in snowpack
Figure , shows the relationship between the pH
and the electrical conductivity (EC) in the snow layers. There is a clear relationship between falling pH
and rising EC. The percentage of acid snow (lessthan /.0,) in all the samples was 30.0ῌ, and the weighted mean pH was /.*. Kurita and Ueda (,**0) reported that the pH in the precipitation urban areas in
Nagano Prefecture during +31,ῌ,**- was approximately /.*; the pH in the winter precipitation in theplateau areas in Nagano Prefecture was in the vicinityof /.0 during +33-ῌ+331. In other words, at the plateau area, there was little occurrence of acid precipitation. However, in this study, it is conceivable thatacid precipitation was frequent in the mountainous
area during JanuaryῌApril ,**1, and the pH in the
precipitation di#ered little from that in the urban
areas of Nagano Prefecture.
Figure - shows the relationship between the Naῌconcentration and the concentrations of the other ions(Cl῍, SO.,῍, and Ca,ῌ) in all the snow samples collectedin this study. In the ﬁgure, the relationship betweenNaῌ and Cl῍ is nearly equal to that in sea salt, suggest-

Fig. ,. Relationship between pH and electrical conductivity (EC) in snow layers.

Shah et al.

11

Fig. .. Variations in daily mean air temperature andsnow depth from December +, ,**0, to April -*,,**1. The arrows represent the days when thesnow pit studies were conducted.

ing that the contributions of sources other than sea
salt can be considered to be negligible. Thus, it was
concluded that sea water was the predominant sourceof Naῌ and Cl῍ in the snow. In contrast, no such
relationship was observed between Naῌ and SO.,῍ orCa,ῌ, suggesting that SO.,῍ and Ca,ῌ were of both sea
salt and non-sea salt origin. Non-sea salt SO.,῍ andCa,ῌ originate mainly from anthropogenic, dust, andorganic sources (Suzuki, +331). Most of the non-sea
salt SO.,῍ in winter precipitation originates from the
combustion of fossil fuels, and non-sea salt SO.,῍ contributes to the acidic anion load (Suzuki, +331).
-.,

Fig. -. Relationship between the concentrations ofCl῍, SO. ,῍, Ca,ῌ, and Naῌ in all of the snow samples collected in this study. The broken lines
represent the ratio for sea water (Hanya et al.,+333).

Variation in ionic concentration in snow layers
Figure . shows the variation in the daily mean air
temperature and the snow depth from December +,,**0, to April -*, ,**1. The day that the snowpackbegan to be formed was December +1. The maximum
snow depth was +/- cm, on March +/. After March ,-,the snow depth decreased monotonically, and the snowpack had disappeared by April ,/. The daily mean
air temperature from December +1, the date that thesnowpack was formed, to February 0, ,**1, was below*῎ on the majority of days. The percentage of dayson which the daily mean air temperature exceeded *῎increased after February 1, and the daily mean air
temperature was above *῎ on most days after March,-. It is conceivable that the rise in the air temperature after March ,- was the major cause of the monotonic decrease in the snow depth.
Figure / shows the vertical proﬁle of the EC in thesnow layers. Since the snow pit study site is approximately -** m away from the weather observation station, the variation of the snow depth that was measured by the snow pit study does not always accord
with that of the snow depth monitored by a snowdepth gauge. The ECs of all the snow layers decreased throughout the season, but in such a manner

12Bulletin of Glaciological Research

Fig. /.

Vertical proﬁle of the EC of the snow layers.

Fig. 0. Vertical proﬁles of the anionic concentrations in the snow layers. The snow layers with remarkably high Clῌ,
NO- ῌ and SO. ,ῌ concentrations are labeled CaῌCc, NaῌNc, and SaῌSc, respectively. These labeled snow layers aremonitored until their disappearance.

that the relative order of the ECs remained constant,that is, the layer with the highest EC at the start of theseason continued to be the layer with the highest
value throughout the remainder of the season until
the disappearance of the layer. The ECs of the snow
layers measured on January /, January 3, January ,0,and February 0 were *.,.ῌ/./1 mS mῌ+, *.,*ῌ..3- mSmῌ+, *.,2ῌ..-. mS mῌ+, and *.,2ῌ..32 mS mῌ+, respectively, and the vertical proﬁle of the EC in the snow
layers exhibited spikes. The ECs of the snow layers
measured on February ,+ and March 1 had little difference (*.,*ῌ-.,* mS mῌ+ and *.-*ῌ-.2, mS mῌ+, respec-tively). These ranges are lower than those observedon February 0, and the shape of the vertical proﬁle of
the ECs in the upper snowpack was smooth. On andafter March +0, the range of the EC values continued
to decrease as the season progressed, and the shape ofthe vertical proﬁle of the EC in the snow layers became smoother. The remarkable decrease in the EC
between March 1 and March +0 suggests that ionswere signiﬁcantly ﬂushed out from the snowpack.
On March +0, most of the snow layers were granularsnow. Moreover, on and after March +0, the snow
temperature of the entire snowpack was approx-

Shah et al.

imately *῍. These facts indicate that signiﬁcant snowmelt occurred between March 1 and March +0.
In other words, it is conceivable that little snowmelt occurred before February 0, the ﬁrst snowmelt
occurred between February 0 and ,+, and the signiﬁcant snowmelt season set in between March 1 and+0. Though the air temperature was comparatively
low during 1ῌ+0 March, it was at *..ῌ0.-῍ from 3 : **ῌ+2 : ** on March +*. It is presumed that the major
reason for the signiﬁcant snowmelt was the rise in the
air temperature during this period.
The vertical proﬁles of the anionic concentrationsin the snow layers are shown in Fig. 0. The snow
layers with remarkably high Clῌ, NO-ῌ, and SO.,ῌ
concentrations were labeled Ca through Cc, Na
through Nc, and Sa through Sc, respectively. These labeled snow layers were monitored up until the timethey disappeared. Sa, Na and Ca were observed on
January /, and Sb, Sc, Nb, Cb, and Cc were formed by
the snowfall associated with the passing low-pressure
system and the snow clouds formed during the Asian
winter monsoon; Nc was observed on February 0.
All of the labeled snow layers could be observed on
February 0. However, it was di$cult to identify thesnow layer that corresponded to Sc on February ,+.
The disappearance of Sc corresponded to the smoothing of the vertical proﬁle of the EC in the upper
snowpack (Fig. /). Sa and Sb disappeared on March+0. However, NaῌNc and CaῌCc could be traced until
April 0. The date of disappearance of the SO.,ῌ layer
di#ered from those of the NO-ῌ and Clῌ layers. Thisimplies that the selective ﬂushing of SO.,ῌ from thesnowpack occurred early in the snowmelt season.
-.- Variation in anion load in snowpack
Figure 1 shows the variations in the snow waterequivalent (SWE) and anion load. Although the snow
had already melted on February ,+, the SWE tended
to increase until March 1 and ever afterward. Although SO.,ῌ, NO-ῌ, and Clῌ loads decreased slightly
on February ,+, the variations in them were similar to
those in the SWE. It is conceivable that snowmelt
did not occur actively from January 0 to March 1; thedeposited snowfall was more than the volume of melt
runo# until March 1. It is conceivable that the snowmelt observed on February ,+ was a temporary snowmelt event due to a temporary air temperature rise
(Fig. .), and that regular snowmelt only began after
March 1.
The SWE values on March 1 and +0 were .,* mmand -+. mm, respectively; thus, the SWE of +*0 mm waslost from the snowpack, presumably during the same
period. During this period, reductions in the SO.,ῌ,NO-ῌ, and Clῌ loads from the snowpack were observed
to be -0, mg mῌ,, ++/ mg mῌ,, and ++/ mg mῌ,, respectively. The ratio of the loss of each anionic load tothe loss of SWE during each period (March 1 to +0,

13

Fig. 1. Variations in the snow water equivalent (SWE)
and anion loads from January / to April +1, ,**1.

Table +. Ratio of loss of each anion to loss of SWE during each period (March 1 to +0, March +0 to April 0,
and April 0 to +1).
Ratio of lost chemical load to lost SWE
Period,**1/*-/*1ῌ*-/+0,**1/*-/+0ῌ*./*0,**1/*./*0ῌ*./+1

Clῌ/SWE

NO-ῌ/SWE

SO.,ῌ/SWE+4+**4+*4./

+4*3
*4-1
*4-+

-4..
*41*4/2

Fig. 2. Ratio of decrease in the anion loads in the snowpack from March 1 to April +1, ,**1.

March +0 to April 0, and April 0 to +1) is shown in
Table +. As compared to other periods, the ratio of
the reduction in concentration of each anion to theloss of SWE from March 1 to +0 is signiﬁcantly higher.
This indicates that the melt runo# during the earlysnowmelt season had a high ionic concentration.
Figure 2 shows the ratio of decrease in the anion

14

Bulletin of Glaciological Researchload in the snowpack from March 1 to April +1. The
ratio of the decrease of SO.,῎ load is quite di#erent
from that of NO-῎ or Cl῎. The orders of the ratios ofdecrease during March 1 to +0 were SO.,῎ῐNO-῎῏Cl῎. During March +0 to April 0 and April 0 to +1, theorders of the ratios of decrease were similar for allanions. In other words, the di#erence of ﬂush degreeof anion appears conspicuously in early snowmelt
season, and the order of the ease with which the ionswere ﬂushed out from the snowpack was SO.,῎ῐNO-῎
῏Cl῎. As mentioned above, Brimblecombe et al.
(+32/), Davies et al., (+321) and Suzuki (+33+) reported
that the ease with which each ion was ﬂushed wasSO.,῎ ῐ NO-῎ ῐ NH.῍ ῐ K῍ ῐ Ca,῍ ῐ Mg,῍ ῐ H῍ ῐ Na῍ ῐCl῎, Ca,῍῏Mg,῍ῐSO.,῎ῐNO-῎ῐNa῍ῐCl῎ and SO.,῎῏NO-῎ῐCl῎, respectively. SO.,῎ was easy to ﬂush
out from the snowpack than Cl῎. This fact is consistent with that of Brimblecombe et al. (+32/), Davies etal., (+321) and Suzuki (+33+). However, the ﬂush degree of NO-῎ is di#erent every report.
Though it has been conceivable that the major
reason for the order of the ﬂush of each ion is that thedegree of deposition of the chemical substance di#ers
during the process in which it transforms into a granular snow particle (Suzuki, ,***), this mechanism has
not appeared yet. Due to conﬁrm this mechanism, amicroscopic study at the snow particle level is necessary. However, a microscopic study at the snow particle level has not been performed so far, and this is asubject that has to be looked into.

..

Conclusion

The snow pit study was conducted on Mt. Norikura
in the Northern Japan Alps from January to
April, ,**1 to clarify the chemical dynamics in thesnowpack during the snowmelt season. The variation of the EC in snowpack indicates that little snowmelt occurred before February 0, the ﬁrst snowmelt
occurred between February 0 and ,+, and the peak ofsnowmelt season occurred after March 1. Snow layers with remarkably high Cl.῎, NO-῎, and SO.,῎ concentrations were traced; furthermore, the snow layerswith high SO.,῎ concentrations were found to disappear ﬁrst. The percentage decrease in the anionloads in the snowpack during the snowmelt season
di#ered. The orders of the ratio of decrease as thesnowmelt proceeded were SO.,῎ῐNO-῎῏Cl῎. SO.,῎
was easy to ﬂush out from the snowpack than Cl῎.
This fact is consistent with that of previous studies(Brimblecombe et al., +32/; Davies et al., +321; Suzuki+33+). However, the ﬂush degree of NO-῎ is di#erent
every study. It is conceivable that the order of the
ﬂush of each ion is inﬂuenced by the degree of deposi-tion of the chemical substance during the process inwhich it transforms into a granular snow particle(Suzuki, ,***). However, this mechanism is as yet
obscure. More data and a microscopic study at thesnow particle level are required to conﬁrm the orderin which the ions are ﬂushed out from the snowpack.

Acknowledgements
This research was supported by a Grant-in-Aid
for Scientiﬁc Research (No. +1-+***1) from the Japan
Society for the Promotion of Science, and it was also
supported by the Global Environment Research Fund
(C-0 and C-*/,) of the Japanese Ministry of the Environment.

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