特別講演

特別講演 1

H.R.von Gunten

特別講演 2

J.AlstadCvclic me七al miαra七ion in a qroundwater s七reamtl. R. von Gunten
by .
Labora七orium fOr Radiochemie， universi七g七 Bern， Swi七zerland
andPaul Scherrer 工nstitu七， WOrenlingen， Swi
七zerlandAbs七rac七:
Alpine and peri‑alpine coun七ries recover drinking wa七er to alarge extend from shallow groundwa七er resources in widely dis‑tribu七ed glacio‑fluvial deposits. The groundwater in 七hese qua‑七ernary sedimen
七s is mainly recharged by infil
七ra七ing river wa‑
七er. Due 七o the impor七ance of 七h工s process for the wa七er qua‑li七y i七 is manda七ory 七o unders七and 七he biological， chemical andphysical changes which occur during infiltra七ion and movemen七of wa七er J.n aqu工fers.
工n 七he presen
七 s七udy we concen
七ra
七e on daily， annual and spa‑cial changes of some dissolved inorganic wa七er componen七s ando七her properties in the River Glat七 (Switzerland) and in 七headjacen七 groundwa七er s七ream.
A well equipped s七udy site is available for 七hese investiga‑tions. Here， wa七er from 七he pollu七edRiver Gla七七 infil七ra七escontinuously wi七h a mean linear flow velocity of 2‑4 m d‑1
七hrough 七he saturated and s七ra
七ified ground zone and becomes
七he uppermos
七 工 ayer of 七he local groundwater s七ream.

Diurnal varia七ions of several parame七ers (e.g. pH，O2，Al) wereobserved in 七he river wa七eど . These systematic fluc七ua七ions aremuch larger in summer 七han in winter and are accen七ua七ed during
sunny days. They are 七he resul七 of pho七osyn七hesis and respira‑tion of aquatic bio七a. Upon infil七ration in the ground，七hesevaria七ions are almost completely damped due 七o chemical reac‑
七ions involving CaC03 dissolu
七ionjprecipi七a七ion. However， very

drastic decreases in pH and dissolved oxigen (Fig. 1) are ob‑served during the infil七ra七ion of river water in七0 七he aquifer.
These sudden changes in the infil七ra七ing wa七er influence solu‑

2bili七ies and redox proper
七 ies of several chemical elements. The
chemical changes during infiltra七ion of rive去 wa七er can be des‑cribed fairly well by a few simple elec七ron transfer (involvingorganic ma七七 er degradation， deni七rification， nitrifica七ion) andurn‑weathering reac七ions. Of prime impor七ance during 七he warm s
mer mon七hs is 七he oxida七ion of organic ma七七 er and the deni七ri‑
fica七ion process. Both reactions are s七rongly influenced bytemperature enhanced micro‑biological activities.

崎。

巳盟主主ユ

訓告ー
'00

250

3 2ミ︒
︒
2。
"
100。

512Rlv"

15・. [m]202.
1。

11OlltChangesint
heconcentr
at
io
no
fd
issolvedo.~ygen du
r
in
gi
n
filtr
at
i
o
no
fr
iv
erw
ate
ri
n1
985.
an
d
1986.
‑
T
hec
on
cent
r
at
ion
si
nt
her
iv
e
rar
eshowna
td
ist
ancez
er
o.N
o
t
ic
eag
ener
ali
ncr
e
asei
n
oxygenc
oncentr
at
ion
satg
r
eate
rf
lowdistancesintheaqu
ifer.Theyarepr<?
<!:，ced̲~y ad~;([l~~e_̲ofoxygen‑richgroundw
ater
.ロJu
ly1
985，
AAugust1
985，0Augusf1
986，vNovember1
986.
deeper，

The annual temperature var工a七ions in river and groundwa七er are
responsible for biology‑ and solubili七y‑rela七ed cyclic changes
in many of the wa七er parameters. Mos七 of these changes in thegroundwa七er are highly correla七ed (e.g・pH， Si‑， Mn‑， Cd‑con‑9・alkalini七y， O2， N03‑，centra七ions) or an七icorrela七ed (e・2G +Ca ' ) with 七he wa七er 七emperature.
The enhanced degrada七ion of organic ma七七 er a七 higher tempera‑
tures during summer leads 七o a larger consump七ion of. oxygen
and， hence，七 o a reduc七ion in 七he redox po七ential which becomes
low enough 七o cause the dissolu七ion of manganese oxides andhydroxides. The redox po七en七ial was，however，never low enough七o cause iron oxidesjhydroxides 七o dissolve. The annual changes

in redox potential lead 七o very pronounced Mn2+‑peaks in 七he‑ 3一groundwa七er during summer 七ime (Fig. 2). No such peaks areobserved in 七he river water which is，七herefore no七 七he sourcefor 七he high Mn2+ーconcen七ra七ions in 七he groundwa七er stream.
Recen七 measuremen七s in 七he pore‑wa七er of Gla七七 River sedimen七s
have shown Mn2+‑concen七rations . 500 ppb in summer 1987・ Thus，
七he sedimen
七s in 七he river bed can be considered as a sourcefor 七he dissolved Mn. Addi七ional Mn2+ may resul七 from thedissolution of aquifer material during reducing condi七ions. Themagni七ude of 七he Mn‑peaks varies from year to year and depends
G +'on 七he clima七ic condi七ions. The dissolved Mn2
does no七 migratevery far in 七he groundwater fieldi i七 is soon reprecipi七a七ed asmanganite.
巳 盟 主e 240
1988

35~ 1984

1987

30
ι
弓adnuw

内︐

ω之CDo.
，ー・苫‑。

15』

105。
Tlme

Annualv
ariabiliryoftemperatureoCロ， ;Mn:勺 "(oneunit=10ppb);Cd:.，o(oneunit=0.
01ppb)
att
hewellin5mdistanc
efromtheRiverGlat.
tNoticedi
fferentscalesforMn:+andCd~+.

Fig. 2 also demonstrates 七ha七 七he concen七ra七ions of cadmium in2+.
七he groundwa
七er are highly correla
七edwi
七h 七hose of Mn
Again，七he Cd‑peaks show no relation 七o river concen七ra七ions.
We assume 七ha七 七 he chemical behaviour of Cd is influenced byco‑dissolu七ionj‑precipita七ion of Mn or CaCo3・ A possible addi‑
tional source for Cd may be degraded organic ma七erial. Cadmium
also disappears，like Mn，after relatively shor七 migra七ion
dis七ances.
Fig. 2 shows a very high correla七ion of Mn and Cd wi七h wa七er
七empera七ure and，七 hus， wi
七h bioac
七ivi七y. Material balances‑ 4‑sugges七 七ha七 七 he observed concen七ra七lorIS(nqt shown here)forCu and Pb resul七 frorn 七he degrada七ion of aqua七ic b工o七a，whereas
Zn‑concen七ra七ions are rnostly 工nflucenced by river water concen‑
tra七ions.
orn‑
The infiltration of dissolved，particula七e and colloidal cpounds frorn 七he river Gla七七工 n七o the groundwa七erwas further
inves七iga七ed，using 七he fallout of 七he reactor accident a七031:)" ，工131T ， 13211"'.....， 134，37 wereChernobyl. The radionuclides 1~VJRu~J~Te~J~， 1~J'CsJ
1es in 七he river and in 七he groundwa七er.
rneasured several 七il、 1‑r ̲̲‑" 1oissolved (> 0.05 日rn) 31工and k0U3
JRu infiltra七ed frorn 七he riverin七o 七he groundwater practically wi七hou七 delay. 132Te was re‑34，137 S was no七 observed
七arded by 七he aquifer r
na七erial and 1~J~ ， ~J' C
in the groundwa七er. This behaviour of Cs was expec七ed，based on
nen七s perforrned in the labora‑
ba七ch and colurnn sorp七工 on experJ.r
七ory using frac
七ions of 七he aquifer r
na七erial. Par七icula七e androrn 七he river in七o thecolloidal infil七ra七ion of radioactivity fgroundwa七er is a slow process of rninor irnportance.

5

NEW DEVELOPMENTS IN THE S工SAK TECHNIQUES FOR STUDY工NGSHORTL工VED NUCL工DES.

J. Als七ad，The Gδteborg‑Mainz‑Oslo S工SAK‑collabora七ion.

Abstract
A review of the recent experimental investigations based on
the S工SAK techniques of studying nuc1ear decay properties isgiven. The main efforts have been devoted to deve10ping fastchemica1 separations of Tc，Ru，Rh and Pd and measuringy‑energy va1ues and transitions ins‑decay of neutron‑richisotopes of these e1ements.
09，110The most neutron‑rich nuc1ides observed so far are 1~~~'~~~Tc ，
109，
111̲.
1
13，115'~~~Ru and ~~-'~~-Pd which have been investigated bymeasuring sing1ey‑ray andyy (t)‑coincidence spectra.
The chemica1 separation procedures are sketched with emphasison the very fast chemistry.
工n the ihvestigated region the level schemes may be explained
to consist of two different types of energy states，
proton‑ho1es connected to a sper工ca1 shape nucleus and proton
partic1es with rotational band‑type structure of a deformed
nuc1eus. The energy va1ue 工n a leve1 of the latter for odd mass
number isotopes varies regu1arely with mass number and passes aminimum midway between the neutron number N=50 and N=82.
yy‑coincidence measurements of short1ived nuc1ides require highf1ow‑rates of 1iquids in the solvent extraction separation
steps over sizable periodes of time. A need for a reduction in
the volumes of the 1iquide wastes has been a primary reason
for a development of new centrifuges with internal volumes 1ess
than 1 m1. The new separation system consists of， which 七raps aerosol c1usters in sma111) a degassing uni七
1iquid vo1umes from the gas‑jet and separates the carrier gas
and the 1iquid in a gas‑liquid centrifuge and2) centrifuges for separating 1iquid mixtures in the 1 m1
vo1ume range. The centrifuges are running at a speed of up to45 000 r.p.m.
The construction and proper七ies of the new centrifuges andtheir app1ications is discussed.

‑ 6