PREFACE h e h y d r o l o g i s t o r d i n a r i l y needs no
r e m i n d e r t h a t fresh w a t e r i n
n a t u r a l e n v i r o n m e n t s is i n constant c i r c u l a t i o n a n d t h a t his b r a n c h of science r e q u i r e s methods
of s t u d y a p p r o p r i a t e to d y n a m i c
systems.
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T h e c h e m i s t w h o is c o n c e r n e d w i t h w a t e r q u a l i t y , h o w e v e r , m a y t e n d to u n d e r e m p h a s i z e the i m p o r t a n c e of the m o t i o n of w a t e r i n u n d e r s t a n d i n g its c h e m i s t r y .
C e r t a i n l y he most often sees o n l y s m a l l segments of the
system, h e l d c a p t i v e a n d i m m o b i l e i n w a t e r s a m p l e bottles.
Although
there is no reason c h e m i c a l e q u i l i b r i u m cannot be established i n d y n a m i c systems as w e l l as i n static ones, a n e q u i l i b r i u m or e v e n a steady-state c o n d i t i o n does r e q u i r e a c e r t a i n l e n g t h of t i m e to b e c o m e established. B e f o r e a n i n t e l l i g e n t d e c i s i o n c a n b e m a d e as to w h e t h e r a c h e m i c a l system is l i k e l y to b e near e q u i l i b r i u m , one needs to k n o w , at least a p p r o x i m a t e l y , b o t h the rates of the c h e m i c a l reactions i n v o l v e d a n d the rate of m o v e m e n t of w a t e r w i t h respect to other materials p a r t i c i p a t i n g i n the r e a c t i o n .
F r o m the latter rate, the l e n g t h of t i m e a v a i l a b l e
for e q u i l i b r a t i o n to o c c u r c a n b e e s t i m a t e d a n d c o m p a r e d w i t h the t i m e r e q u i r e d for a r e a s o n a b l y close a p p r o a c h to e q u i l i b r i u m . A l t h o u g h the n e e d for k n o w i n g s o m e t h i n g about these k i n d s of rates seems o b v i o u s , the amounts of d i r e c t l y a p p l i c a b l e i n f o r m a t i o n o n r e a c t i o n kinetics is m e a g e r a n d v e r y f e w c h e m i c a l studies have t a k e n w a t e r c i r c u l a t i o n rates into c a r e f u l c o n s i d e r a t i o n .
S u r e l y a stronger emphasis
on
s u c h w o r k w i l l be n e e d e d i n o r d e r to u n d e r s t a n d the c h e m i s t r y of r i v e r s , lakes, a n d u n d e r g r o u n d w a t e r . O n e of the objectives of the s y m p o s i u m f r o m w h i c h the papers i n this v o l u m e c o m e was to e m p h a s i z e
these
points. I n g e n e r a l , the papers w h i c h m a k e u p this v o l u m e represent w o r k that is b e i n g d o n e t o w a r d u n d e r s t a n d i n g the c h e m i s t r y of n a t u r a l aqueous systems w i t h o u t t r y i n g to fit t h e m to s i m p l e e q u i l i b r i u m m o d e l s . A b r o a d s p e c t r u m of subject matter is c o v e r e d .
Some papers c o n c e r n field s t u d y
a n d others present results of l a b o r a t o r y i n v e s t i g a t i o n of s y n t h e t i c s o l u tions. A f e w of the papers e m p h a s i z e t h e o r e t i c a l aspects almost e x c l u s i v e l y b u t most are b a s e d o n c u r r e n t research a n d demonstrate t e c h n i q u e s a n d approaches that s h o u l d a i d other p r a c t i t i o n e r s i n the field of w a t e r chemistry. It is c e r t a i n l y trite to p o i n t out the i n t e r d i s c i p l i n a r y n a t u r e of s c i e n tific studies of n a t u r a l w a t e r . O n e p u r p o s e of the s y m p o s i u m w h e r e these ix
Hem; Nonequilibrium Systems in Natural Water Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1971.
papers w e r e presented, h o w e v e r , w a s to b r i n g together some of different specialists a n d exchange
p o i n t s of v i e w o n s h a r e d
these
concerns
w i t h the a q u a t i c e n v i r o n m e n t . T h e reader of this v o l u m e m a y p o s s i b l y d r a w the c o n c l u s i o n that progress to date i n o u r a p p l i c a t i o n of n o n e q u i l i b r i u m approaches
has
b e e n d i s m a l l y s m a l l . T h e r e is c o n s i d e r a b l e justification for s u c h a c o n c l u s i o n , b u t progress is b e i n g m a d e , nonetheless.
A l t h o u g h m u c h can
still b e l e a r n e d b y a p p l i c a t i o n of e q u i l i b r i u m m o d e l s , one m u s t b e w a r y of o v e r s i m p l i f i c a t i o n of the c o m p l e x i t i e s of the r e a l w o r l d .
It w i l l
necessary e v e n t u a l l y to a c c e p t the existence of the c o m p l i c a t i o n s Downloaded by KAOHSIUNG MEDICAL UNIV on June 5, 2018 | https://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0106.pr001
p r e p a r e to d e a l w i t h t h e m .
be and
T h e s e papers s h o u l d h e l p p u t i n t o p r o p e r
levels of i m p o r t a n c e s u c h factors as the s l o w a n d u n k n o w n rates of m a n y i m p o r t a n t c h e m i c a l reactions a n d the influence of w a t e r m o v e m e n t , m i x i n g , a n d c i r c u l a t i o n o n the c o m p o s i t i o n of w a t e r bodies.
Instances
of
progress i n s t u d y of details of the c h e m i s t r y of c e r t a i n specific s i m p l e systems w h i c h are i n c l u d e d i n some of the papers m a y s t i m u l a t e w i d e r use of n o n e q u i l i b r i u m approaches.
I n f u t u r e s y m p o s i a l i k e this one, one m a y
h o p e r e a l progress w i l l be d o c u m e n t e d . T h e assistance of the authors w h o s e papers are i n c l u d e d a n d of others w h o h a v e a i d e d i n t h e i r p r e p a r a t i o n a n d p u b l i c a t i o n is g r a t e f u l l y recognized. JOHN D.
U . S . D e p a r t m e n t of the I n t e r i o r Geological Survey M e n l o P a r k , C a l i f o r n i a 94025 October
1970
χ
Hem; Nonequilibrium Systems in Natural Water Chemistry Advances in Chemistry; American Chemical Society: Washington, DC, 1971.
HEM
