S c i . R e p . Kanazawa U n i v . Vo l . 2 9 N o . 2 p p . 1ω118 December 1 9 8 4
Migration of Trace Heavy Metals at the Sea WaterjSediment Interface
KikuoTERADA and Chisato TOMIYAMA
*De ρ ' a r t m e n t 0 1 C h e m i s t η 1 , F a c u l t y 0 1 S c i e n c e , Kanaza ω a U s i v e r s i t y ( R e c e i v e d 2 9 O c t o b e r 1 9 8 4 )
A b s t r a c t M i g r a t i o n b e h a v i o r o f some t r a c e h e a v y m e t a l s s u c h a s C o ( I I ) , Cu ( I I ) , Mn( I I ) a n d Zn ( I I ) a t t h e s e a w a t e r / s e d i m e n t i n t e r f a c e was i n v e s t i g a t e d b y t a n k e x p e r i ‑ m e n t s . The s e a w a t e r w h i c h was d o p e d w i t h t h e s e m e t a l i o n s ( p p b t o ppm l e v e l s ) a l l o w e d t o c o n t a c t w i t h t h e r a w ‑ , i g n i t e d ‑a n d a u t o c l a v e d ‑ m a r i n e s e d i m e n t s a n d t h e c h a n g e o f t h e c o n c e n t r a t i o n o f e a c h m e t a l was t r a c e d a t d e f i n i t e t i m e i n t e r v a l s . At t h e e n d o f t h 巴 e x p e r i m e n t s , a c o r e s a m p l e o f t h e s e d i m e n t was t a k e n a n d a n a l y z e d f o r e a c h m e t a l i n e v e r y 1 mm t h i c k s e g m e n t . On t h e o t h e r h a n d , t h e s u r f a c e s e d i m e n t was s u b m i t t e d t o p a r t i a l e x t r a c t i o n w i t h v a r i o u s k i n d s o f r e a g e n t s t o e s t i m a t e t h e c h e m i c a l s p e c i e s o f t h
巴m e t a l sc a p t u r e d i n t h e s e d i m e n t . W h i l e e v e r y m e t a l i o n was q u i c k l y a d s o r b e d o n s u r f a c e o f t h e raw s e d i m e n t , a c o n c e n t r a t i o n g r a d i e n t f r o m s u r f a c e t o b o t t o m o f t h e w a t e r p h a s e o c c u r r e d i n t h e i g n i t e d s e d i m e n t s y s t e m . The m i g r a t i o n o f m a n g a ‑ n e s e t o t h e s e d i m e n t p h a s e was a s s u m e d t o b e c o n c 巴 medw i t h b a c t e r i a l a c t i v i t y i n t h e s e d i m e n t . C o p p e r a n d z i n c s e e m e d t o b e a d s o r b e d v e r y q u i c k l y o n t o some f i n e s e d i m e n t p a r t i c l e s b y t h e f o r m a t i o n o f o r g a n o m e t a l l i c c o m p l e x e s w i t h some o r g a n i c m a t e r i a l s e x i s t i n g i n t h e s e d i m e n t s . C o b a l t m i g r a t e d r e l a t i v e l y f a s t downward w i t h i n t h e s e d i m e n t p h a s
氾a f t e ri t s d e p o s i t i o n .
Introduction
The t r a c e metals c a r r i e d t o the ocean from a number o f sources through streams o r meteoric p r e c i p i t a t i o n are s u b j e c t e d t o chemical and b i o l o g i c a l a c t i o n s , and f i n a l l y s i n k and d e p o s i t i n t h e sediment through various pathways. A number o f s t u d i e s concerned with removal mechanism o f various t r a c e elements from sea water have been performed and i t has been revealed t h a t the removal o f them i s r e l a t e d t o some s u r f a c e phenomena on suspended p a r t i c u l a t e s such as hydrous metal oxides
l),c l a y or d e t r i t a l organic substances
2).The behavior o f t h e s e t r a c e metals i n ocean has been explained by applying s e v e r a l models
3),
4).Craig suggested t h e scavenging model i n which e s p e c i a l l y c l a y minerals play an important r o l e f o r migration o f t h e d i s s o l v e d heavy metals
5).Tsunogai e t a 1 .
6),
7)proposed the s e t t l i n g model as a removal mechanism. I n t h i e r model , t h e v e r t i c a l t r a n s ‑ ' P r e s e n t a d d r e s s ; Water R e s e a r c h I n s t i t u t e , N a g o y a U n i v e r s i t y , C h i k u s a ‑ k u , N a g o y a
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1 0 4 K i k u o T E R A D A a n d C h i s a t o T O M I Y A M A
p o r t o f t h e t r a c e m e t a l s i s p r i n c i p a l l y a c h i e v e d by g i a n t p a r t i c l e s whose d i a m e t e r i s u s u a l l y l a r g e r t h a n a few tensμm. While , Bacon e t a J . 8 ) s u g g e s t e d t h e i m p o r t a n c e o f s c a v e n g i n g p r o c e s s a t s e a w a t e r / s e d i m e n t i n t e r f a c e .
From t h e v i e w o f a d s o r p t i o n a n d r e d i s s o l u t i o n o f t r a c e m e t a l s a c c o r d i n g t o t h e i r l i q u i d
‑ s o l i d e q u i 1 1 i b r i u m , t h e s e a w a t e r / s e d i m e n t i n t e r f a c e seems t o p o s s e s s v e r y a t t r a c t i v e f e a t u r e 9) , 1 0 ) . The p u r p o s e o f t h i s s t u d y i s t o c l a r i f y t h e b e h a v i o r o f t r a c e m e t a l s a t t h e s e a w a t e r / s e d i m e n t i n t e r f a c e . A model o f a n e n v i r o n m e n t n e a r t h e s e a w a t e r / s e d i m e n t i n t e r ‑ f a c e was s e t by means o f a t a n k e x p e r i m e n t i n l a b o r a t o r y a n d t h e c o n c e n t r a t i o n c h a n g e o f some t r a c e m e t a l s i n s e a w a t e r was f o l l o w e d u n d e r s e v e r a l c o n d i t i o n s . F u r t h e r m o r e , i n o r d e r t o o b t a i n t h e i n f o r m a t i o n o n t h e c h e m i c a l f o r m s o f t r a c e m e t a l s t r a n s f e r r e d i n t o s e d i m e n t , a p a r t i a l e x t r a c t i o n p r o c e d u r e 1 1 l was a p p l i e d .
E x p e r i m e n t a l
Sam ρ l e s . Marine s e d i m e n t was c o l l e c t e d by d r e d g i n g from 2 0 m d e p t h a t Tsukumo Bay , N o t o P e n i n s u l a . The s e d i m e n t was s i e v e d t h r o u g h a s t a i n l e s s s t e e l s i e v e ( 4 2 m e s h ) i n s e a w a t e r i n o r d e r t o a v o i d a i r c o n t a c t , t h e n was s t o r e d i n a r e f r i g e r a t o r a t 4
0C . T h i s s e d i m e n t was g r e e n i s h d a r k g r a y s i l t . The f u n d a m e n t a l d a t a on t h e o r i g i n a l s e d i m e n t a r e shown i n T a b l e l . S u r f a c e s e a w a t e r was a l s o c o l l e c t e d a t Tsukumo Bay and s t o r e d i n a r e f r i g e r a t o r a t 4
0C .
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Reagen お. Manganese ( I I ) and z i n c ( I I ) s t a n d a r d s o l u t i o n s were p r e p a r e d by d i s s o l v i n g t h e i r p u r e met
【a l s i n h y d r o c h l o r i c a c i d t o make a s o l u t i o n o f 1 , 0 0 0 ppm. C o p p e r m e t a l was d i s s o l v e d i n n i t r i c a c i d and e v a p o r a t e d t o d r y n e s s , t h e n t h e r e s i d u e was d i s s o l v e d i n 1 M h y d r o c h l o r i c a c i d t o make 1 , 0 0 0 ppm s o l u t i o n . C o b a l t ( I I ) s t a n d a r d s o l u t i o n was p r e p a r e d by d i s s o l v ‑ i n g c o b a l t c h l o r i d e 6 h y d r a t e o f g u a r a n t e e d r e a g e n t g r a d e i n d e i o n i z e d w a t e r and s t a n d a r d i z e d g r a v i m e t r i c a l l y a s c o b a l t ( I I I ) o x i d e . A l l c h e m i c a l s u s e d were o f g u a r a n t e e d r e a g e n t g r a d e . The r a d i o a c t i v e t r a c e r , C o ‑ 6 0 , was p u r c h a s e d from t h e R a d i o c h e m i c a l C e n ‑ t r e , Amersham , E n g l a n d , whose s p e c i f i c a c t i v i t y was 8 4 mCi mg-
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s e a w a t e r , B: s e d i m e n t ,
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品 f 弘 r r a t i o no f T r a c e 王子仰の , 1 ! 4 c t a l s a t t h e S e a F / a ! e r ! S c d i m e n f I n t e ! ) の ω 1 0 5
A s e t u p f o r t a n k e x p e r i r n . e n t 1 S shown i n F i g . 1 . A c o n t 呂 mer o f 1 5 cm i n d i a m e t e r and 3 0 C l 1 1 i n h e i g h t v v a s made o f a c r y l i c a c i d r e s i n o f 2 r 1 1 1 1 1 i n t h i c k n e s s . Thεtank was t i g h t I y c o v e r e d
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ァl i cr e s i n p l a t e o I 5 m m i n t h i c k n e s s S e v e r a l s m a l l 1 1 0 1
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況s sc a p i l l ヨ r yt u l コ ε ( i n n e r d i a m ε t e に 1 ' w a s r n o u l 1 t e d f o r s a m p l i n g bottom w a t e r a t 1 cm o v e r t h e s u r f a c e o f t h e sedimen t . The bottom w a t e r was sampled a p i p e t c o n n e c t e d w l t h t h ε a r ア t u b e . O t h e r h o l e s were f o r p i p e t t i n g t h e s u r f a c e
羽r a t e rand f o r a i r t o t h e s y s t e m .
Atomic a b s o r p t i o n meaurements were done w i t h a H i t a c h i 1 7 0 ‑ 5 0 typεGamma a c t i v i t y measurements were p e r f o r m e d w i t h a Kobe l { ogyo STL‑200 weH‑type s c i n t i l l a t i o n c o u n t e r , and X‑1 ・ ayd i f f r a c t i o n was measured w i t h D e n l 三 iG e i g e r F l e x o l A MOM D e r i v a t o g r a p h TYP‑D‑I02 , a H i t a c h i ‑ H o r i b a M‑50 pH meter and l w a k i K M s h a k e r V I
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Pretreatment 0 1 sedim 仰 sam 戸 ル s e d i m e n t ‑‑‑The raw s e d i m e n t was a t 5 5 0
0C f o r 2 4 h r s t o remove a l 1 y o r g a n i c s u b s t a n c ε s T h i s was r e d d i s h brown c o l o L d i f f r a c t i o n a n a l y s i s f o r t h e powder s a m p l e s s h o v ¥ T e d some c o r r e s p o n d i n g t o m o n t m o r i l l o n i t ゑ c a l c i t eand d o l o m i t e i n t h e p a t t e r n s o f b o t h raw and s e d i m e n t s . T h e r e f o r e , i t seems t h a t t h e m i n e r a l i s I i t t I e a f f e c t e d
Moreov 日 r , t h e two k i n d s o f s a m p l e s were s u b m i t t e d t o d i f f ε r e n t i a l t h e r m o a n a l y s i s . 1 n t h e d e r i v a t o g r a m o f t h e raw s e d i m ε n t , t h e r e was an e x o t h e r m a l peak a t 2 0 0 ‑ 5 0 0 ' C c o r r e s p o n d
帽i n g t o c o m b u s t i o n o f o r g a n i c s u b s t a n c e s . 日 owεver , t h i s peak d i s a p p e a r e d i n t h e d e r i v a t o
田gram o f t h e i g n i t e d o n e . T h i s means t h a t c o m p l e t e d 町 o r n D o s i t i o no f o n ? : a n i c s u b s t a n c e s i n t h e raw s e d i m e n t was a c h i e v e d by s i m p l e
A u t o c l a v e d s e d i m e n t ‑‑‑ Thεraw s e d i m e n t was p l a c e d i n a b e a k e r which was c o v e r e d w i t h watch g l a s s , and t h e b e a k e r was p u t i n t o a n a u t o c l a v e t o s t e r u i z e d a t 1 . 2 a t m . and 10WC f o r 3 0 m i n o
A l l t h e s ε a water u s 日 dwere f i l t e r e d t h r o u g h 0 . 4 5μm f i l t e r and a p a r t o f t h e f i l t ε r ε d s e a water was i r r a c 1 i a t e d w i t h 1 5 W mercury f 0 1 " a b o u t 1 0 0 h r s t o decompose s u b s t a n c e s i n s e a wate r .
P ァ ocedure 1 0 1 ' t , ω 1 1 < Known amounts o f heavy m e t a l I o n s
c o p p e r , c o b a l t and z i n c ) were a d d e d t o 31 o f thεsea w a t e r and pH was t o 7 . 7 士 0 . 1 w i t h 1 M sodium c a r b o n a t e s o l u t i o n . A f t e r t h e s e a water was a l l o w e d t o s t a n d f o r 2
‑ 5 d a y s a t 2 5
0C , i t v v a s f i i t e r e d t h r o u g h 0 . 4 5μm M i l l i p o r e f i l l t e r , t h e n c a r e f u l l y i n t o a c y l i n d r i c a l c o n t a i n ε r which c o n t a i n e d a s e d i m 岳 民 間 mplei n 5 cm t h i c k n e s s
国showni n F i g . 1 . I n o r d e r t o c a u s e no d i s t u r b a n c e i n t h e s e d i m e n t 0 1 1 a d d i n g s e a w a t e r 二 ac i r c u l a r t h i n f i l m o f p l a s t i c s which was made many s m a l l h o l e s and hung w i t h t h i n s t r i n g s , was s l o w l y l i i t e n a c c o r d i n g t o e l e v a t i o n o f s u r f a c e o f thεwate r . The c o n t a i n e r s were i n a t h e r m o s t a t r e g u l a t e d a t 2 5 : : t l O C .
At i n t e r v a l s , t h e boitom w a t e r sample was t a k e n f 伺 , 0 1 1 1a l a y e r o f 1 cm a b o , 氾 t h e
s u r f a c e o f t h e s e d i m e n t t h r o u g h t h e c a p i l l a r y t u b e At t h e same t i m ε 、 t h es u r f a c e
w a t e r sample was p i p e t t e d o u t from a o f 1 cm below t h e water s u r f a c e . By u s i n g
a d e f i n i t e volume o f t h e s a m p l e s , t h e m e t a l c o n c e n t r a t i o n was d e t e r m i n e d y‑ray
1 0 6 K i k u o TERADA a n d C h i s a t o TOMIYAMA
c o u n t i n g f o r c o b a 1 t , o r by a t o m i c a b s o r p t i o n s p e c t r o m e t r y f o r manganese , c o p p e r , c o b a 1 t and z i n c .
F i n a l l y , v e r t i c a 1 d i s t r i b u t i o n o f m e t a 1 i o n s i n t h e w a t e r a n d s e d i m e n t p h a s e s were measured a f t e r t h e p e r i o d o f 2 0 ‑ 3 0 d a y s . A f t e r s i p h o n i n g o f f a l l w a t e r i n t h e c o n t a i n e r , a c o r e s a m p 1 e o f t h e s e d i m e n t was t a k e n w i t h a t h i n p 1 a s t i c t u b e , and was i m m e d i a t e 1 y f r o z e n a s i t w a s . Then , t h e f r o z e n c o r e s a m p 1 e was c u t i n t o some s e g m e n t s i n t h e o r d e r o f d e p t h . I n t h e c a s e o f c o b a l t , γ ‑ c o u n t i n g o f e a c h s e g m e n t was m e a s u r e d . For t h e o t h e r m e t a 1 s , e a c h s e g m e n t was decomposed by h e a t i n g w i t h n i t r i c a c i d ‑ p e r c h 1 o r i c a c i d m i x t u r e ( 1 : 1
v j v ) and a f t e r f i l t r a t i o n t h e f i l t r a t e was s u b m i t t e d t o a t o m i c a b s o r p t i o n s p e c t r o m e t r y . I n o r d e r t o e s t i m a t e t h e a d s o r p t i o n o f t r a c e m e t a 1 s o n t o t h e c o n t a i n e r w a l l d u r i n g t h e e x p e r i m e n t , a s m a l l p 1 a t e ( D ) o f t h e same r e s i n whose s u r f a c e a r e a was a b o u t 6 cm
2, was s u s p e n d e d i n t h e s e a w a t e r c o n t a i n i n g C o ‑ 6 0 . A f t e r 3 0 d a y s , t h e a c t i v i t y
、a d s o r b e do n t o t h e p 1 a t e was c o u n t e d a n d i t was c a l c u 1 a t e d t h a t o n 1 y 2% o f t h e o r i g i n a 1 a c t i v i t y was a d s o r b e d o n t h e c o n t a i n e r wa1 . 1 T h e r e f o r e , 1 0 s s o f m e t a 1 i o n s from s e a w a t e r was e s t i m a t e d t o b e n e g l i g i b 1 e .
B e s i d e s , r e d i s s o 1 u t i o n b e h a v i o r o f m e t a 1 s from t h e s e d i m e n t p h a s e was examined on c o n v e r t i n g t h e s y s t e m from a e r o b i c t o a n a e r o b i c c o n d i t i o n s . About 2 0 d a y s 1 a t e r , when o x i d a t i o n a n d c o n s e q u e n t l y m e t a 1 f i x a t i o n were f o u n d t o b e f a i r l y w e l l a d v a n c e d , t h e s a m p 1 e was t r a n s f e r r e d i n t o a 5 0 ‑ m 1 s y r i n g e shown i n F i g . 2 . The s a m p 1 e was k e p t a i r
‑ t i g h t w i t h r u b b e r s t o p p e r , a n d was a l l o w e d t o s t a n d f o r some d a y s a t room t e m p e r a t u r e i n t h e d a r k , s o t h a t t h e m i l i e u c h a n g e d becoming
a n a e r o b i c . A f t e r a s c e r t a i n i n g t h a t t h e a n a e r o b i c c o n d i t i o n was a c h i e v e d , t h e w a t e r s a m p 1 e was t a k e n from t h e s y r i n g e and a n a 1 y z e d .
P a r t i a l e x t r a c t i o n ρ r o c e d u r e . At t h e e n d o f t h e t a n k e x p e r i m e n t s , t h e s u r f a c e s e d i m e n t o f a b o u t 2 m m t h i c k was s u c k e d i n t o a s y r i n g e t o g e t h e r w i t h s m a l l amount o f s e a w a t e r , t r a n s . f e r r e d i n a p 1 o y e t h y 1 e n e b o t t l e and mixed w e l l . An a d e q u a t e amount o f t h i s s a m p 1 e was t a k e n i n t o a c e n t r i f u g e t u b e and c e n t r i f u g e d a t 3 , 5 0 0 rpm f o r 1 5 min t o remove s e a w a t e r a n d i n t e r ‑ s t i t i a 1 wate r . Washing o f t h e s e d i m e n t w i t h
a b o u t 1 5 m1 o f d e i o n i z e d w a t e r was c a r r i e d o u t F i g . 2 . . ¥ノ A p p a r a t u s f o r a i r ‑ s h i e l d e d e x p e r i . o n e t i m e . Then , m e t h a n o 1 ‑ a c e t o n e m i x t u r e ( 1 : 1 m e n t .
v j v ) was a d d e d t o t h e s e d i m e n t and t h e t u b e was s h a k e n f o r 4 ‑ 5 h r s . The e x t r a c t was
s e p a r a t e d by c e n t r i f u g a t i o n ( 3 , 5 0 0 rpm , 1 5 m i n ) a
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o f T r a c e Hc i . . l v y ] V l e ! t u s a t t h c S e a
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,T h i s d i f f e r e n c e may be a t t r 引 J u t e dt o t h e e x i s t e n c e o f s l 1 b s t a n c e s i n t h e former s e d i m e n t . The q u a n t i t i e s oIτlanganεse a d s o r d e d werεonly o f t h e i n i t i a l c o n t e n t i n b o t h s e d i m e n t s .
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乱c t i v ‑ o f Co‑60 i n a q u e o u s phasεfor t h e r a ' i l 1 and i g n i t e d s e d i r n e n t s y s t e m s
,1nεach s y s t e m , UV ‑ i r r a d i a t e d and u n i r r a d i a t e d s e a w a t e r s were u s e d a s a q u e o u s p h a s e
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remarkable d i f f ε r e n c e i n removal p r o c e s s o f c o b a l t v v a s o b s e r v e d i n b o t h c a s e s . I n t h e f o r m e r s y s t e m , a t f i r s t t h ε i n boUom d e c r e a s e d more r a p i d l y t h a n s u r f a c e b u t a i t e r 9 days t h e i n b o t h s u r f a c e and bottom became On t h e o t : , 色 i nt h e system , t h e i n s u r f a c e water l a y e r changed , a l t h o u g h t h a t i n bottom 1 2 , y e r d e c r e a s e d t o a b o u t o I i n i t i a l r a d i o ‑ Furthermore , two c u r v e s , UV ‑ i n 百 H a t e dand i t i s shown t h a t i n t h e raw s e d i m e n t system f o r f o r m e r casea l i t t l e h i g h e r o f Co‑60 was l o s t t h a n t h e l a t t e r c a s e
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コdu n d e r t h e s a r n e c o n d i t i o n s a : ヨ t h e t a n k e X D c r i r n e n t . F i g . 6 s I 1 0ws t h e c o n c e n t r a t i o n o f manganesc , c o p p e r , c o b a l t 3nd z i n c f o r t h e raw and i g n i t e d s e d i m e n t As was o b s e r v e d i n t h 吃 C o ‑ ‑ 6 0t r a c e r e x p e r i m e n t , an u n i f o r m d i s t r i b u t i o n o f each m e t a l was e s t a b l i s h e d i n t h e raw s e d i m e n t
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' 1 1 m 旬 u sk i n d s o f fadors s u c h a s , t h e p r e s e n c e o f f l 1 a t e r i a l s and some o r g a n i c s u b s t a 日 c e s , t h e b a c t e r i a l and d j f f u s i o n o r c o n v e c t i o n 日 f f e c t s v v e r ε a s s u r n e d t o i n f l u e n c ε o n t h e o f t h e m e t a l s a t 問 d i m e n ti n t e r f a c e
。F i r s t , t h e i n f l u e n c ε o f b a c t e r i a i n t h e s e d i m e n t , Nas t e s t e d an autodaved sedhnen t . The c o n c e n t r a t i o n c h a n g e s o f manganese
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1 S n o t f o r t h e o f t h e s e m e t a l s t h e s e d i m e n t . On t h e o t h e r manganese a g a i n i u t o t h e s e 剖 r n e n t a s i t b e h a γ 吋 i nt h e w i t h o u t sedimen t . 1 n o f 8 w i t h 6 , i t can be e x p ε c t e d t h a t o f manga ロ e s emay b 尽 問 l a t e dt o t h e b a c t e r i a l i n t h e sedimenC
i n u r d e r t o e v a l u a t e t h e e f f e c t o f t h e s l 1 b s t o . n c e s i n s e a w a t ε r on o f t h e met 叫 si n t o t h e s e d i m e n t 号 , t h ee x p e γ i m e n t t h e h u r n i c s e e i .
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咽t i c a ld i s t r i b u t i o n o f Co‑60 c a l c u l a t e d t h i s D v 叫 u ec o i n c i d e s w i t h t h e o b s e 1 ' vea o n e a s s h o も i n 5 . T h e r e f o 1 ' 弘 i tcan be con c I uded t h a t t h e d i f f u s i o n i n l a m i n a r f l o w i n water column i s t h e most i m p o r t a n t p r o c e s s f o r t h e o f m e t a l s i n t h ぞ s e d i m e n ts y s t e m . On t h e o t h e r i n t h e c a s e s o f t h e raw and a u t o c l a v e d s e d i m e n t s y s t e m s , i t seems t h a t thεrah ぅ o fd i f f u s i o n i s s o r a s t and proce~.;s may be t h e r a t e ‑ d e t e r m i n i n g s t e p . Such d i f f u s i o n p r o c e s s s h o u l d b ε 1 ' e g a r d e d a s d i f f u s i o n i n t u r b u I e n t f 1 0w which may b e o c c u r r e d t h e a q u e o u s p h a s e 巧 》 ろ yc e r t a i n m 訂コ配配 . c h a n i た ε 3 m . .
1 n f a c t , a c o n v e c t i o n c u r r e n t was o b s e r v e d a movement o f s m a l l r e s i n which was i n w i t h t h e s e a water u s e d a . n d i n t h e a q u e o u s 日 Thep a r t i c l e s sunk down t o t h e b o t t o r n t h e c e n t 日 ro f t h e water and t h e n moved : I o v v a r d t h e w a l l o f t h e c o n t a i n e r . Then , a l o n g t h e w a l l i t a s c ε n d e d t o t h e s u r f a c e and
f a s t t a k i n 只 a b o u t1 7 min i n o n e c o n s t a n t i n a t h e r m o s t a t o v e r t h e
The movement was o I t h e whoie s y s t e m c a u s e d w i t h t h e h e a t g e n e r a t e d by somεreaction
a c o n v e c t i o n c u r r e n t must b e i n t h e s ε d i r 了 l . e n t0 1 ' a t
s e d i m e n t i n t e r I a c ε . t h e same t e s t was examined i n theεd s e d i m e n t system , t h e pa 1 ' t i c l e d i d n o t mov( 三 t h e o b s e r v a t i o n f o 1 ' Z h r 8 . T h e r e f o r e , i t seems t h a t some e x o t h 邑 rma1r e a c t i o n O C C l β : r e d i n t h e raw 0 1 " a u t o c l a v e d sedim 己 n tb u t n o t i n t h e εd o n e . t h e sim 日 a re x p e r i m e n t s were c a r r i e d o u t u n d e r a t 5 ‑ 6 t : . As
' l y a s e x p e c t e d , a v e r t i c a l o f c o n c e n t r a t i o n o c c u r r e d i n t h e w a t e r column o f t h e raw 9 . T h i s i n d i c a t e s t h a t t h e h e a t some s e d i m e n t system a s shown i n
r e a c t i o n i n t h e s e d i m e n t was e x o t h e r m a l m e t a b o l i c a c t i v i t y o f t h ε
consumed t h e c o l d s u r r o u n d i n g s , 0 1 ' t h a t t h e
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(0) l V I n , (ム) C u , (X) Z n ヲ(口) C o
‑0‑ s u r f a c
担,ーゆ b o t t o m
pfL There a r e many k i n d s F i g o 1 0 0 C o n c e n t r a t i o n c h a n g e o f M 九 C u , Z n a n d C o i n a q u e o u s p h a s e a d j u s t
己dt o pH 4 . 2 f o r t h e r a w o f r e a c t i o n s which on i n s e O l l n e n t s y s r e n 1 .
e . g , 固 c h e l a t e a c i d ‑ (0) N l n , (ム) C u , (X) Z n , (口) C o b a s e o x i d a t i o n and ‑ 0 ‑ s u r f a c e , ー ゆ b o t t o m
i o n ‑ e x c h a n g e e t c . ) b u t i t V i l i l l be q u i t e d i f f i c u l t t o a s c e r t a i n which r e a c t i o n
p r i n c i p a l l y o c c u r r e d
,I n f a c t , i n t h e u s i n g k a o l i n i t e o r some c h e l a t i n g r e s i n s s u c h a s Dowex A‑l o r U n i s e r e x UR‑120H a s t h e s o l i d p h a s e i n t h e o f t h e theεneous d i s t r i b u t i o n o f i h e m e t a l s was a c h i e v e d and a 1 s o a c o n v e c t i o n c u r r e n t v v a s o b s e r γ ε d suggεthe r e a c t i o n b e t v v e e n m e t a l s and t h e s e γnaterialswasεxothenna l . V v h i J e c o p p e r was r a p i d l y t r a n s f e r r ε d t o b o t h c h e l a t i n g
m a n g a n e s ε ' 0 Ta 3 a d s o r b e d Dow 日 xA ‑ 1 g r o u p : i m i n o d i a c e t i c b u t n o t UR
‑120B g r O G p : These r e s u l t s a r e c o n s i d e r e d t o be r e a s o n a b i e b e c a u s e manganese b e l o n g s t o t h e hard m e t a l b u t c o p p e 了 i sr a t h e r 3 0 f t
争 c t o f r e d o x c o n d i t i o n t h e s y s t e m o The b e h a γ i o r o f m e t a l s a t s e a
i r o n and m a n g a n e s ε
フi ss a i d t o be t o t h e e f f e c t o f redox
c o n d i t i o n i n t h e s y s t e m
14,
15l.Table 2 s h o v , r s t h e c o n c e n t r a t i o n c h a n g e s o f manganese ,
c o p p 己 主 and c o b a l t i n s e a water 京市 e nt h e s y s t e m was c o n v e r t e d from t h e a e r o b i c t o
a n a e r o b i c c o n d i t i o n s a a s d e s c r i b ε d above
固A f t e r f o r 5 d a y s , t h e
c o n c e n t r a t i o n o f c o p p e r and c o b a l t i n a q u e o u s p h a s e gave no w h i l e t h a t o f
manga ロ e s ei n c r e a s e d a b o u t t e n t i m e s t h e i n i t i a l c o n c 告 n t r a t i o n
,T h i s r e s u l t s u
宮: Q ε s t st h a t
M i g r a t i o
河 口{' l ' m c e H ω , v y M c l a l s a t t h e S e a W a t e r / S c d i m e l l t l n t e l f a c e 1 1 3
manganese ha 弓 b 台 e nf i x e d t o t h e s e d i m e n t T a b l
日2 . 心 コ n c
日n t r
乱t i o nc h a n g ε o f : M n , C u a n d Co i n a s o x i d i z e d form and r ε d i s s o l v e c 1 i l 1 a q e o u s a q u e o u s p h a s e i n 8 n a e r o b i o s i s
p h a s e a c c o r d i n g t o a d r o p o f t h e r 吋 ox
阿 佐 n t i a li n t h e s y s t 吃 m.
V e r t i c a l d i s t r i b u お : o n m e i a l s i n s e d ‑ i m e n t . Where d o e s t a k e p l a c e t h e
o f m e t a l s t h e s e d i m e n t from s e a water , 一一一一一一 一一一一一‑
and a r e t h ε y r e t a i n e d ? ' 1 ' 0 c l a r i f y t h e s e
q u e s t i o n
ヲt h e v e r t i c a l d i s t r i b u t i o n o r t h e m e t a l s i n t h e s e d i m e n t l a y e r was s u r v e y e d . According t o t h e metho c 1 mentioned , c o r e samples o f t h e s e d i m e n t f r e s h l y c o n c e n t r a t e d t h e m e t a l s werεtaken an c 1 3 . 1 1 a l y z e d a l o n g t h e d e p t h . The r e s u 1 t s a r e shown i n F i g . 1L The a b s c i s s a i n d i c a t e s t h e amount o f m e t a l s c o n t a i n e d i n e a c h l‑mm l e n g t h o f t h e c o r e s a m p l e s .
1 0 n l n i t i a l c o n c n C o n c n . a f t e r 5 d a v s ppm ppm
Mn
(m0 . : 3 7 3 . 8 9 Cu ( l l ) 0 . 1 8 0 . 1 8 Co ( I l ) 1 . 2 1 1 . 0 0
As i t i s c I e a r from among t h e m e t a l s s u r v e y e d
フmanganesee x h i b i t 日 d p a r t i c u l a r d i s t r i b u t i o n , c o n c e n t r a t i n g i n t h e f i r s t 1 m m s u r f a c e an c 1 steεdecreasing i n t h e n e x t 1 m m l a y e r . On t h e o t h e r z i n c , c o p p e r and c o b a l t d e c r e a s e d more g r a d u a l l y from t h e t o p t o 3 ‑7 m m d e p t h o f : t h e c o r e . From t h e s e r e s u l t s , t h e r e a c t i o n between t h e s e m e t a l s and t h e s e c 1 i m e n t seεms : 1 0 takεat a v e r y t h i n s u r f a c e o f t h e s e d i m e n t and 出 e nt h e m e t a l s e x c e p t f o r manganese may d i f f u s e downward t h r o u g h t h e i n t e r s t i t i a l wate r . Up t o d a t e , a m l l u e r o u s s t u d i e s on m i g r a t i o n o f manganese i n i n t e r ‑ s t i t i a l v v a t e r have b e e n r e p o r t e d
16,
17), For t h e thεsam 日 S ε d i m e n twas s u r ‑
sQ mm‑
1N
百mrn
叶O 2 0 4 0 6 0 。 1 0 2 0 3 0 ( A )
2 0 1 ‑ 十
3 0 1 ‑ !
).J
g m m → } J g mm‑
I5 1 0 。 │ 2 : 3 4 5 I
l uh τーー2 0
F i g . 1 1 . V e r t i c a l
とl i s t r i b u t i o no f ( A ) Mn ( I I ) , ( B ) Z n ( l I ) , ( C ) C u
( I I ) a n d ( D ) C o ( I I ) i n t h
邑r a ws e d i m
巴n tt a k e n u p t h e m e t a l s
。
十
ι 寸‑
﹄
P I
l l i ‑
‑ o i ﹁ a i l l
‑ ‑ ﹁
l 1 0 5 0 2 2 3
F i g . 1 2 . V
巴r t i c a ld i s t r i b l
日t i o n o f Mn I n t h e o r i g i n a l s e d i m e n t a f t ε r 2 0
‑ d a y s o f c o n t a c t w i t h
s e a w a t e r
1 1 4 K i k u o T E R A D A a n d C h i s a t o T O M ! Y AMA
f o r v e r t i c a l d i s t r i b u t i o n o f manganese a f t e r c o n t s
,c t wi : i h t h e o r i g i n a l s e a 可 . v a t e r w i t h any m e t a l s f o r 2 0 The r e s u l t i s shσwn i n F i g
,1 2 . The v e r t i c a l d i s t r i b u t l o n o f manganese i s l o o k e d a s r a t h e r u n i f o r r n t h e whole T h e r e ‑ f o r e , h i g h e r
盲c o n c e n t r a t i o no f t h e e l e m e n t i n t h e 1 mrn t o p o f t h e s e d l n 1 e n t i n d i c a t e s t h a t d e p o s i t e d manganese can b e r e t a i n e d i n v e r y t h i n s u r f a c e o f t h e s e d i m e n t f o r c e r に a i nt i m e l n t e r γ a . 1
t h e m e t a l 当 的 t h es e d i m e n i o P a r t i a l e x t r a c t i o n w
色r eo e r ‑ fromed t o s u r v e y t h e m e t a l t r a n s f e r r e d i n t h e s e d i m e n t . no m e t a l was c
1 e t e c t e d i n t h e m e t h a n o l ‑ a c e t o n e e x t r a c t . ‑ I I e n c ε . t h e s e m e t a l s seem n o t t o b
色a s s o c i a t ε d w i t h s u c h t h e s o l v 色白 tm i x t u r e . The n e x t e x t r a c t i o n w i t h magnesium c h l o r i d e s o l u t i o n was p 町 formedt o l e a d ! t h e i o n ‑ e x c h a n g e a b l e m e t a J T h i s i m p l i e s t h e m e t a l s e l e c t r o s t a t i c a l l y bounαto a ! i n e r a l s s u c h a s T a o n t .
。 r 1 [ 0 s u b s t a n c e s . Sodium s o l u t i o n V v O l S t o d i s s o l v e thεm 巴 t a la s s o c i a t e d w i t h h u r n i c and i u l v i c a c i d s . And t h e m e t a i s l e a c h 色 dw i t h a s e r i 泊 。 f adds o f d i f f e r e n t c o n c e n t r a t 1 o n s a r e i n t h e form o f o x i d e ,
t h e m e t a l s a s s o c i a t ε d w i t h o r g a n i c s u b s t . a n c e s . N e x t f r a c t i o n
w i t h
and add may c o n t a i n n o t o n l y t h e m e t a l s combined w i t h p a r t b u t a i i 呂 ot h e o x i d a t i γ e s u c h a s r n a n g a ‑ n e s e d i o x i d e o Ano t h e l a s t f r a c t i o n c o n t a i n ε d t h e r e s i d u a l m e t a l s e x c e p t f o r t h a t o f s i l i
0c a r e
The r e s u l t s a r e s h
仁i n i ロ whicht h ε r e s u l t f o r t h e
s e d i m e n t i s p r e s e n t ε d i n ( A ) and i n ( B ) t h a t f o r t h e s e d i m e n t aHowed t o c o n t a c t w i t h thεsea ' N a t e r added a c e n : a i n amount o f t h e r n e t a l i o n s f o r 2 0 Data on e a c h f r a c t i o n a r e i n o f : 1 o t a l a El o u n t o f t h e ex : 1 r a c t e d r n e t a l
About 4 0 % o o f mar 沼 2 L n e s e '~!:/as e:K~racted
c h l o r i d e from t h e m e f a l s e d h n e n t , whilεfrom t h e
s e d i m ε n t no manganese v l 1 a s e x t r a c t e d a t a 1 1 v v 1 t 1 1 t h i s T h i s t h a t l a r g e p a r t manganesεexists a s manga l G e s e i n t h e s e d i m e n t a f t e r t o meth‑
a n o I ‑ a c e t o n e 日 x t r a c t i o n . T h i s r e s u l t seems t o con : f l i c t w i t h t b e r e s u l t shown i n T a b l e 2 ,
:
;
ι
主f 巳二十一
i:=5‑F
二 二i i
刊 口 i
: ; 「 J ) 「
‑ 4 Aじこ二二二二二二コ
F i g . 1 3 . P a r t i a l
巴x t r a c t i o no I t h e m e t a l s f r o m s e d i m e n L R ‑ l : O o 5 t v ' 1 MgC I "
R ‑ 2 : O o 5 M NaOH , R ‑ 3 ・ O . 0 1 MH C l , R
→4 : O . l M H C 1 , R ‑ 5 : 1M HC , I R ‑ 6
目1M HC l+ 3 0 % H
2ü
2 •R ‑ 7 :
HN03~HCJu.
I H ! : g r a u o n ( ) f T r a c c l l e a ( v l v f e i a l s a t t h c S
r::: a 1 ; J
1au
フr j S e d i
刀l e r ; . lI n t c J f a ω 1 1 5
which i n d i c a t e d t h a t r e d i s : 3 0 1 u t i o n o f manganese i n thεsedin 1 . e n t s t a r t 日 d when t h e s y s t e m was
which i n i t i a ! l v had b e e n
t o an a ! l a ε r o b i c c o n d i t i o D . T h e r e f o r e , ; J mangan 色 s e t o t h e s ε a water a s b i v a I e n t i o n
令n l u n : a t e s つ s e d i m e n t
呂 so x i d i z e d i t can b e a s s l 1 med t の b ei t s o x i c 1 e s . uch aE~ 1 ' v 1 n O ( ) f I o r f ¥ / I n C ! 1 I n o r d e r t o e x t r a c t t h e o x i d i z e d manganese w i t h
t h e s e t r i ‑ o r t 巴 t r a v a l e n tmanganese s h o u l d be 己 c tt o some r E 、 d u c t i O I 1 . The
r e d u c t a n t i n t h i s c a s e i : 3 methanoI which v , r a s u s e d t o t h e c h l u r i d e e x t r a c t i o l 1 . 1 1 1 f a c t , when t h e same s e d i m e n t was t r e a t e d a . t f i r s t v v i t h
i t gave 1 1 0 manganese i n t h e e x t r a c t . . MnOOH i s c o n s i d e r 氏 1a s D o s s i b l e mechanism
'8)4MnOOH 十 4H → → ト 2 f v l n
2,1 n t h i s from m 日 hano l .
t h e 。 l
w i l l be d e s i r ♂ d : 1 0 t h e c h ε m i c a l form o f manganese which h a s b e e n s e a water i s d i f f e r e n t from t h a t o f t h e man g ; a n e s e f o r m e r can b e r e g a r d e d a s u n s t a b l e fonn which w i l l
i n t h e s e d i r n ε n t from t h e
e:~isted i n t h e s e d i r n e n t . The b e s u b i e c t 1 0 r e d l 1 c t i o n o r With r e s p e c t t o c o p p e r , t h e d a t a shown i n 1 3 ( B ) i n d i c a t
出t h a tmost o f C ¥ l p p e r a p p ε a r e d i n t I 1 e : 3 odium and 0 . 0 1 M add f r a c t i o n s ~ t h e s t a b i l i t y c o n s t a n t s o f o r g
札口o ‑ ‑ c o p p e r a r e v e r y l 1 i g h .
t h a t above o f c o p p e r may e x i s t a s
o r g a n I c o f c o p p e r i s t o OCCupY o f t h e t o t a l c o p p e r i n marine sediment S t o f f e r s e t aF
O)f o u n c 1 t h a t o f c o p p e r was p r e s e n t a s t h e f o n T I . a s s υ c i a t e d
" ¥ ' 1 i t h humic a c i d a n d / o r f u l v i c a c i d i n t h e s e d i m e n t c o l l e c t e d from B e d f o l d B a y . t h e
日 8 u l to b t a i n e d t h e p r e s e n t
アseemst o be r e a s o n a b l e .
For a o f c o b a l t was 1 ε a c h e d i l 1 b o t h r n a g c h l o r i d e and sodium f r a c t i o n s and most o f c o b a l t was d i s s o l v e d i n ( l O l M e
l': i d from t h e s e d i m ε n t r e t a i n e d t h i s e l e m . e n t from s e a ¥ v a t e r . 1 n c o n t r a s t t o t h i s f o r t h e o r i g i n a l s e d i m e n t no c o b a l t W e : 3 extraded wHh t h e s e r e a g e n . 旬 。 T h i smeans t h a t t h 日
c h e m i c a l form o f c o b a l t f r e s h l y i n t h e s e d i m e n t i l 1 d i f f 巴 r e n tfrom t h R t o f g i n t I 1 e s e d i m 色 n t a s shown i n 1 1 c o b a ! t seems t o 1 1 1 0 γ e w i t h i n t h e s e d i m e n t f a s t t o t h e o t h e r e l e m e n t o F r
・o n . J . t h e s e r
色s u l t s , i t i 8 assumed t h a t a f t e r i n t o t h e s 吋 c o b a l tmay
dowmvard and i 8 s u b j 告 c tt o someεnetic t h
色臼ni t D γ A
乍1 汲 a 町 写 yb e c o n v ε r 1
勾ι
切 !s
坑 t a 討 : コ J l ef お o r m s . The 日 F ε お a reγεryat 抗 t r
百a a c t i れ τ 1 、 花 an ピ dm o r e d ε e t ヨ a 幻 l i l e di 加 τ n γ ε 回 S
1.沿窓a 批 t i o n
予'0/一" 1 山 l 日 1b e
仁 d e s i r e d .
mechanism As d e s c r i b e d above , t 1 1 e d a t a
t r a c e r n e f a l , a t sea 角 c e . I ¥ ; I a n g a n ヨ s e :
t o t h e o f manganese s u g g e s t t h a t t h ε b a c t e r i a l may b e c o n c e r n e d w i t h t h e b e h a v i o r o f t h i s e l e m e n t a t s e a
f a c e o E h r l i c h
21)r e p o r t e d t h a t h e had i s o l a t e d b o t h
1 1 6 K i k u o T E R A D A a n d C h i s a t o T O M I Y A M A
b a c t e r i a from s ε a andwhen n u t r i e n t s were m a i n t a i n 吋 i no p t i m a l t h e s e c u 1 t u r e s i n c r e a s e d ε x p e r i m e n t a l d e p o s i t i o n o f 1 0 n o n t o p u l v e r i z e d n o d u l e . C r e r a r e t a . 1
22)a l s o t h a t b a c t e r i a c a n a c c e l e r a t e manganese
w i t h i n marine e
孔v i r o n m e n t
。o x i d a t i o n o f manganese by d i s s o l v e d oxygen i n an a q u e o u s s o l u t i o n i s v e r y s l o w a t o r below pH 8 . 5 . Stumm
23)h a s s u g g e s t e d thεprocess f o r t h e o x i d a t i o n o f manganese ,
Mn や s l o w ( l )
Mn
(II)十 f主主~>1 ¥ 1 1 日
OI }
1 s l o w Mn ( I I ) TVln0 2 (s) 十~ー←一一→
hεexpressed t h e o x i d a t i o n k i n e t i c s a s f o l l o w s : d ) 1
一一寸了一」二 [Mn ( I O J 十 k [Mn ( I I ) ] k=l ど [OH‑]
t h e d a t a i n t h e p r e s e n t w i l l b ε a s [Mn(Hl] v s
。t i m e f o r t h e raw and s e d i m e n t s :,;性印 I Sa s s h o v i T n . i n F i g . 1 L 1 . From t h e s e i t 1 s e v i d e n t t h a t t h e r 白 l c t i o nt a k e n p l a c e a t t h e t i m e o f manganese i s n o t s i m p l e f i r s t o r d e r b u t o f s e c o n d o r d e r o r r e a c t i o r L t o t h e Stumm's model , t h e p r o c e s s c a n be e s t i m a t e d f o r t h e raw s e d i m e n t s y s t e r n . F i r s t , i o n i s o x i d i z e d t o d i s s o l v e d oxygen i n a q u e o u s t h e n t h e f o r r n a t i o n o f Mn0
2a c c e l e r a t e s t h e removal o f ) f r o r r ; s e a w a t e r s i r : . c e h a s an
a s shown i n ε 1 n t h i s p r o c e s s , b a c t e r i a may t h e f i r s t r e a c t l o n . T h i s i s t h e r e a s o n t h a t manganese was t r a n s I e r r e d t o t h e a u t o c l a v e d s e d i m e n t where any b e c t e r i a was a b s e n t .
On t h e o t h e r i n s p i t e o f t h e a b s e n c e o f manganese was t o t h e s e d i m e n t . T h i s can be a t t r i b u t 吋 t ot h e e f f e c t o f f e r r i c o x i d e on t h e o x l d a t i o n r a t e o f manganese
24).T h i s m e c h a n i s H l was r e v e a l e d Van d e r 九 ¥ T e i j d e n
25)t o t h e s t u d i ε S . i t was a 1 s o r e p o r t e d t h a t t h e
o x i d a t i o n o f manganese f e r r i c o x i d ε 1 S n o t s o e f f e c t i v e i n c o n t r a s t w i t h t h e e I f e c t o f manganese o x i d e .
and z i n c : The b e h a v i o r o f z i n c a t t h e s e a i n t e r f a c e can b e r e g a r d e d a s s i m i l a r t o t h a t o f c o p p e r . B e s i d e s t h e e x p e r i r n . e n t mentioned t h e f
臼 0 1 日 l o w i 加 nge 叉 p e 白 r
冨i r 口 m r
官e r 叫 1 叫 t
明v v a scomp 同 lem 浪 1 e 叩 n t a l 日 l yc a
釦r r i e do u t . Unde
臼r
勾t h esame c o n d i t i o n s a s i n t h e r 右引 B
S
銑 凶 t 討 i r r i n gf o r 1 m 叫 I I 加 n . Th ε s e a
予wa
羽討 t e 町 rwas t a k e n w i t h t h e s u s p e n d e d s e d i m e n t
p a r t i c l e s a t a d e f i n i t e i n t e r v a l o f t h e t i m e and f i l t e r e d t h r o u g h 0 . 4 5μmεfilter
M i g r a t i o n 0 1 T r a c e Hea り M e t a l sa t t h e S e a W a t e r j S e d i m e n f I n t e l 合 c e 1 1 7
The c o n c e n t r a t i o n c h a n g e s o f t h e m e t a l s
were d e t e r m i n e d by a t o m i c a b s o r p t i o n s p e ‑ 0 . 5
c t r o m e t r y .
As a r e s u l t , 100% o f c o p p e r , 97% o f z i n c , 70% o f c o b a l t , a n d 30% o f manganese were removed from t h e s e a w a t e r b y a d s o r b i n g o n t h e p a r t i c u l a t e s . I t seems t h a t a d s o r p t i o n r a t e o f c o p p e r a n d z i n c o n t o t h e p a r t i c u ‑ l a t e s i s v e r y f a s t . I n t h e t a n k e x p e r i m e n t s u s p e n d i n g o f a sma l 1 amount o f f i n e p a r t i c l e s o f t h e s e d i m e n t was u n a v o i d a b l e i n a q u e o u s p h a s e a l t h o u g h s e a w a t e r was v e r y c a r e f u l 1 y
i n t r o d u c e d o n t h e s e d i m e n t . T h e r e f o r e , a f a s t r e m o v a l o f t h e s e m e t a l s i n e a r l i e r s t a g e o f t h e e x p e r i m e n t m i g h t b e p r i n c i p a l l y d u e t o a d s o r p t i o n a n d s e d i m e n t a t i o n w i t h s u c h f i n ε p a r t i c l e s .
F i g . 1 4 ( c ) and ( d ) show t h e l o g [MJ v s . t i m e p l o t where t h e d a t a were o b t a i n e d from t h e t a n k e x p e r i m e n t s . I t i s o b v i o u s t h a t t h e r a t e o f i n i t i a l c h a n g e was s l i g h t l y f a s t e r t h a n t h a t o f s u b s e q u e n t s t e p . I n o r d e r t o a s c e r t a i n t h e mechanism o f t h i s p r o c e s s , t h e d a t a o b t a i n e d from t h e c h e l a t e r e s i n s y s t e m a r e p l o t t e d i n t h e same manner ( F i g . 1 4 ( e ) ) .
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