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E F F E C T S O F W A T E R - S O L U B L E P O L Y M E R S A N DE L E C T R O L Y T E S O N P E R M E A B I L I T Y O F H E A V YC L A Y S O I L S

P. P. O l o d o v s k i i , M . G . M u r a s h k o ,A . B. B o g d a n o v a , R . F. D o t s e n k o ,G . A . I v k o v s k a y a , T . L. M a t v e e v a ,a n d T . M . K h o r s e e v a

U D C 6 2 0 . 1 6 8 . 3 4

A s t u d y h a s b e e n m a d e o f t he e f f e c t s o f w a t e r - s o l u b l e p o l y m e r s o n t he f i l tr a t i o n a n d c h e m i c a lr e s p o n s e o f g y p s u m - b e a r i n g s o i l s f r o m t h e H u n g e r S t ep p e an d t a k y r - l i k e s o i ls f r o m t h e K a r s h aS t e p p e .

M e a s u r e m e n t s h a v e b e e n m a d e [ 1- 3] o n t he e f f e c t s o f w a t e r - s o l u b l e p o l y m e r s a n d e l e c t r o l y t e s o n t he p e r -m e a b i l i t i e s o f r o c k - f o r m i n g c l a y m i n e r a l s ( th e n a t u r a l a n d N a f o r m s o f m o n t m o r i l l o n i t e a n d k a ol i n it e ) , u s i n gt he d a t a f i l t r a t i o n , a d s o r p t i o n , a n d e l e c t r o n m i c r o s c o p y , a n d a m e c h a n i s m ( p h y s ic a l m o d e l ) h a s b e e n d ef in e df o r th e i n te r a c t io n b e t w e e n t h e p o l y m e r m a c r o m o l e c u l e s a n d t he a c t iv e c e n t e r s o n t he c l a y m i n e r a l s . A p p r o -p r i a t e c o n c e n t r a t i o n s o f t h e s e p o l y m e r s c a n m a x i m i z e t h e p e r m e a b i l i t y , a n d f u n c ti o n s h a v e b e e n d ef in e d fo rp r e d i c t i n g t h e f i l t r a t i o n c o e f f i c i e n t s a s f u n c t i o n s o f p o l y m e r c o n t e n t a n d s p e c i f i c s u r f a c e .

D e t a i le d m e a s u r e m e n t s a r e o f c o n s i d e r a b l e i n t e r e s t b e c a u s e c u r r e n t p r a c t i c e in s o i l i m p r o v e m e n t p l a c e sp a r t i c u l a r e m p h a s i s o n i m p r o v e d i n f i lt r a ti o n i n h e a v y s o i l s , i . e . , m e a n s o f c o n t r o ll i n g w a t e r t r a n s p o r t .

W e h a v e e x a m i n e d t he e f f e c t s o f w a t e r - s o l u b l e p o l y m e r s o n d e s a l i n a ti o n o f s o i ls a n d i n f i lt r a ti o n i m p r o v e -m e n t , w h i c h h a s d e fi n e d th e s c o p e f o r u s i n g b r a c k i s h w a t e r s f o r i r r i g a t i o n , o n a c c o u n t of t he i m p r o v e d f i l t r a -t i o n o c c u r r i n g i n t h e s o i l s .

W e u s e d g e n e t i c h o r i z o n s I a n d I II f r o m s o i l s i n t h e H u n g e r S t e p p e ( c o l l e c t iv e f a r m N o . 5 ) a n d g e n e t i ch o r i z o n s I a n d I I f r o m t a k y r - l i k e s o i l s in t h e K a r s h a S t e p pe . W e u se d w a t e r - s o l u b l e p o l y m e r s K - 4 , K - 9 ,S M M A , P E M , S V A N , a n d S V A M , w h i c h w e r e m a d e a t t h e I n s t i tu t e o f C h e m i s t r y , A c a d e m y o f S c i e n c e s o f t h eU z b e k SS R . T h e i n f i l t ra t i o n f l ui d s w e r e s a l in e w a t e r s w h o s e c h e m i c a l c o m p o s i t i o n s w e r e s i m i l a r t o t h a t o ft h e w a t e r i n t h e s o u t h e r n H u n g e r S t e p p e c a n a l a n d in th e R i v e r A m u D a r ' y a , i n a d d i ti o n to 0 . 01 M a q u e o u sp o t a s s i u m n i t r a te . M e a s u r e m e n t s w e r e m a d e t o d e t e r m i n e t h e i n i t ia l s a li n i ty in t he h o r i z o n s , t he g y p s u mc o n t e nt , t h e e x c h a n g e a b l e s o d i u m , a n d t he t o t al a b s o r p t i o n c a p a c i t y ; x - r a y a n a l y s i s d e f in e d th e m i n e r a l c o m -p o s i t i o n , w h i l e a d s o r p t i o n s t u d i e s d e f i n e d t h e s p e c i f i c s u r f a c e . I n a d d i t i o n , i n f i l t r a t io n t e s t s a n d e l e c t r o nm i c r o s c o p y w e r e e m p l o y e d . T h e s o i l s w e r e e x a m i n e d in t h r e e s t a t e s : 1 ) w i th th e i n it ia l s a l t a n d g y p s u m c o n -t e n t s , 2 ) f r e e d f r o m s a l t s , a n d 3) m o d i f i e d by a m i x t u r e o f s u b s o i l w a t e r a n d i r r i g a t i o n w a t e r .

T a b l e 1 g iv e s th e m a i n r e s u l t s f r o m t he c h e m i c a l a n d x - r a y s t u d ie s .T h e e f f e c t s o f s a l in e w a t e r s o n t he p a r a m e t e r s w e r e e x a m i n e d b y t e nf o ld t r e a t m e n t w i th a q u e ou s s o l u -

t i o n s o f s a l t s p r e s e n t i n t h e s u b s o i l w a t e r a n d i r r i g a t i o n w a t e r s w i th s o l i d - l i q u i d p h a s e r a t i o s o f 1 : 8, w h i c hw a s f o l l o w e d b y r e p e a t e d w a s h i n g w i t h d i s t il l e d w a t e r u n t i l a n e g a t i v e r e a c t i o n f o r c h l o r i d e w a s o b t a i n e d .

T h e s a l t c o n c e n t r a t i o n s i n t h e s o l u t io n s w e r e m a d e u p 1 /5 f r o m t h e s u b s o i l w a t e r a n d 4 /5 f r o m t h e i r r i g a -t i o n w a t e r .

T a b l e 2 g iv e s d a t a o n t h e c o m p o s i t i o n s o f t h e s e w a t e r s .M e t h od s . T h e m i n e r a l c o m p o s i t i o n s w e r e d e t e r m i n e d f r o m th e x - r a y p a t t e r n s r e c o r d e d w i th a D R O N I 2

d f f f r a c t o m e t e r w i t h C u K ~ r a d ia t io n .C l a s s i c a l c h e m i c a l a n a l y s i s m e t h o d s w e r e u s e d [ 4- 6] ( a r g e n t o m e t r i c , E D T A , f l a m e p h o t o m e t r y , e t c .) .C e n t r a l W a t e r - R e s o u r c e U t i l i z a ti o n R e s e a r c h I n s t i tu t e , M i n sk . T r a n s l a t e d f r o m I n z h e n e r n o - F i z i c h e s k i i

Z h u r n a l , V o l . 3 4 , N o . 2 , p p. 2 3 6 - 2 4 2 , F e b r u a r y , 1 9 78 . O r i g i n a l a r t i c l e s u b m i t t e d J a n u a r y 1 , 1 9 7 7.

1 5 4 0 0 2 2 - 0 8 4 1 / 7 8 / 3 4 0 2 - 0 1 54 $ 0 7 . 5 0 9 1 97 8 P l e n u m P u b l i s h i n g C o r p o r a t i o n


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T A B L E 1.

M a t e r i a l

M i n e r a l o g ic a l C o m p o s i t io n a n d C h e m i c a l C h a r a c t e r i s t i c s

Hun~er Steppe (col,lecttve ~arm No. 5

T a k y r - l i k e s o i l ,Karsha Steppe

4F o r m o f s o i l

I l l

JI ~ w i t h i n i t i a l s a l tI and gypsum c oa -l tent~ /2,1! w . sh e d -saltsm o d i f i e d b y a m i x -ture of subsoilw a t e r a n d i r r i g a -t ion wate rw i t h i n i t i a l s a l tand gypsum con -tentswashed free fromsaltsm o d i f ~ d b y a m i ~tur e o r SUDSOilw a t e r a n d i r r i g a -t ion wate rw i t h i n i t i a l s a l tand gypsum con -teut~w i t h i n i t i a l s a l tand gypsum con -tentswashed free fromsaltsm o d i f i e d b y am ix tu re o f subso ilwate r and i r r i -g a t i o n w a t e r

14,4I

--9! ,51,7 154,~

0

0

17,3o :817,0 0 716,5 10,75

8,8~ 0,7

16 ,4 1 ,418,3 1,216,0 0,6615,2 2,33

I

I I

M i n e r a lcom pos i t ion

quartz, yps um, al-c it e, ~ m m i c a ,kaolimte~ and mont-m o r i l l o m t e ;

~ oartzt g y p s u m ,lom lt6; "fedspars,h y d r o m i c a , k a b l i n i t e ,and m ontm or i l lon i te

quartz, feldspars, cal-cit e , ~y_psum, and amixe~I-'Iayerp h a s e( t rans i t toua l f rom hy -d m m i o a t o k a o l i n i t e ),hydrom iea , and ch lo r i te

TABLE 2. Salt Contents of Soil Water and Irr igat ion WaterObjec t Water type

Hunger Steppe Subsoil waters( c o l l e c t i v e I a r m I r r i g a ti o n w a t e rNo. 5) Southern Hugg er-S t e p p e c a n a l

Tak yr- l ik e so i l Subsoi l wa tersKarsha S teppe I r r iga t ion wate rA m u - D a f y a

HCO~-

0,430,150,270,07:

Cl-

2,340,135,520,063

Ion con ten ts, g / l i te rSO4 2 Ca+-" big+Z I Na+11,7 0,4 0,22 4,210,56 0,0 81 0,043!.0,054,8 9 0,62 0,73 3,310 , 1 0 7 0 , 0 6 9 1 0 , 0 0 3 I 0 , 0 4 0 ]

du e19,261.03714,450 ,3 &

T h e s p e c i f i c s u r f a c e w a s d e d u c e d b y m e a s u r i n g t h e b o u n d - w a t e r c o n c e n t r a t i o n a n d t h e d e n s i t y c h a n g e ofa d i s p e r s i o n m e d i u m m i x e d w i th th e s o l i d , w h i c h t o o k u p t h e a d s o r b e d w a t e r [ 7] ; t h e r m a l d e s o r p t i o n b y n i t r o -g e n w a s a l s o e m p l o y e d .

T h e f i l t r a t i o n s t u d i e s w e r e m a d e w i t h F - l m i n s t r u m e n t s b y a n a l o g y w i t h t h e m e t h o d o f [8 ], w h i l e t h ee l e c t r o n m i c r o g r a p h s w e r e r e c o r d e d w i t h a n E M - 9 . T a b l e 3 g i v e s t h e p a r t i c l e s i z e s , a s w e l l a s t h e m a i n r e -suits f r o m t h e f i l t r a t i o n s t u d i e s , w h i l e F i g . 1 s h o w s t h e c h l o r i d e c o n t e n t d u r i n g w a s h i n g f o r g e n e t i c h o r i z o n sI a n d II I i n t h e H u n g e r S t e p p e f o r v a r i o u s l e v e l s o f w a t e r c o n t e n t an d w a t e r - s o l u b l e p o l y m e r .

E v e n a c r u d e a n a l y s i s o f t he r e s u l t s i n d i c a t e s t h e f o ll o w i n g :1 . T h e v a r i o u s w a t e r - s o l u b l e p o l y m e r s a c c e l e r a t e t h e d e s a l i n a t i o n f r o m t h e i n i t i a l l e v e l t o t h e m i n i m u m

l e v e l [ 9] b y f a c t o r s o f 2 - 2 . 5 .9 2 . T h e s e p o l y m e r s i n c r e a s e t h e p e r m e a b i l i t y f a c t o r s f o r t he h i g h ly s a l i n e s o i l in t he n a t u r a l p o r o s i t y

r a n g e b y f a c t o r s o f 1 . 4 -1 . 5 , w h e r e a s t h e v a l u e s f o r t he w a s h e d s t a t e a r e v i r t u a l l y u n a l t e r e d .

1 5 5


3/5

T A B L E 3. I n f i l t r a t i o n a n d S t r u c t u r e P a r a m e t e r s o f Softs

Soil state P o l y m e r a d d e d

HungerS t e p p e , I soil h o d z o n

p "e r m e a b i l i t y coefficients[ ~,~ - -K 0 ~ f o r g i v e n p o r o - ~ ~ ~ ' ~ " ~sity coefficients r [~ "-" ~ s

With initial salt contentW a s h e d f r e e f r o m s al ts

M o d i f i e d b y. i r r i ga t i o n w a m la Q d s u b so i l w a t e r m i x t u r e

Without polymer0,05% K-4. K-9w l m o m polym~0,0 '25%K-4, K-9,SMMAWithout polymer

Hunger S t e p p e , HI soft horizonWith initial salt content

Washed free from salts

Without polymer0,05% K-4, K-90,025% K-4, K-9Without polymer0,025% K-9, S ~lbiA,

0,024 0,0550,045 0,0830,045 0,0830,045 0,083

0,095 0,136 0,6110,131 0,181 0,4500,131 0,181 0,4100,131 0,181 0,354

L % I0,029 0,111 0,266 0,3090,12110,212 0,383 0 , 4 2 9 [0,121 0,212 0,383 0,429,0,121 0,212 0,383 0,429,0,121~ 0 , 9 0 S T ~ ~ = 1= 0 , 9 7 , 0 5

i

0 , 1 0 3 2 0 , 1 5 5 6 1 0 , 2 2 3 8

0 , 2 3 0 9 1 0 , 3 3 2 0

0,155610,2238i

0,617

0,370PEMModified by irrigation war.el Without polymerand subsoil water mixture 0--~ 0,49

Karsha Steppe, I I soft h o r i z o n e=l ,l 0With initial salt contentWashed free from salts

Without polymer0,05% K-4, K-9Without polymer0,05% SVAM, S MMA, 0,1532S V A NWithout polymer 0 , 1 0 3 2Modified b X irrigation waterand subsotl wafer mixture

_Note.

10,2711lI _ _0 , 4 0 2 2

0.2711a T i s t h e p o r o s i t y o f t h e s o i l i n t h e n a t u r a l s t a t e .

3. A ccel erated elution of the gypsum from the soil is accompanied by an increase in the water pe rme -ability by a factor 1.4-1.5.

4. Modification of a soil by means of mix tur es of irri gat ion wat er and subsoil water does not alte r thefil tration coefficient appreciably by compa rison with salt-f ree soils , nor is the maximu m swelling, gypsumcontent, or exchangeable sodium appreciably altered.

All of the results are explained by the measur eme nts.Soluble salts in any dispe rsed syste m tend to compre ss the diffuse layers around the particle s and in-

crea se the water permea bili ty; result s of this kind have been given for monothermite [10].I t has been shown [1] that the ma crom ole cule s of a water -solub le polyme r can regulate or adjust the be-

havior of a finely divided system, not only on account of particle coagulation but also because the exchangeablecations are partiall y bound; i .e. , some of the exchangeable cations become loca lize d within the pores rathe rthan at the soli d-li qui d interfaces. The resul t is a mate rial less resista nt to external factors. This effectfrom a polyelectro lyte determine s the increa sed tra nspo rt of inorganic salts and acce lera tes the desalinationduring washing. Similar result s have been obtained elsewhere.

For i nstanc e, it has been shown [11] that an initially taky r-l ike soil arti ficia lly treat ed with sodiumchloride will yiel d up 52% of the sa lts during the fi rst stage of washing after tre atm ent , whe rea s only 26% of theNaC1 is lost under the same conditions with an untre ated soil, while the rate of elution is incr eas ed by a fact orof 4.

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cL

4 f 2

, ~ , 0 8 - - -

O , 0 4

T

o 2o 4,3 6o 8sFig. 1. Variations in chloride content during washing for Hun-ger Steppe so ils in relati on to wate r content (P %) and contentof wate r-solu ble poly mers (C %). Fir st genetic horizon: 1) P =30, C =0; 6) P =34, C =0; 7) P =30, conc entr ation of K-9 =0. 05;8) P =33, K-4 conc entra tion 0.05. Third genetic horiz on: 5)P = 17,8, C = 0; 2) P =22.3 , C =0; 3) P =22. 5, K-9 c on ce nt ra -tion 0.05; 4) P = 18.7, K-4 concentration 0.05.

It has also been found [12] that the water per meabili ty and salt loss are incre ased for a sa lt- mar ch me a-dow soil in the presenc e of K-4; the ac cele rate d salt l o s s and water tra nspo rt go with a certain in crea se in therate of gypsum loss in the prese nce of wate r-sol uble polym ers.

The gypsum cryst als in a soil form clumps with the clay mine rals , and these produce conditions for additional hydration, which ultimately reduc es the water perme abili ty. I t has also been found [13] that gypsum ad-ver sely affects the physical pa ram ete rs of soils . In parti cula r, the shape of the gypsum clumps can affect thewate r permeab ili ty of an irr iga ted soil. An increas e in the water content tends to enlarge the gypsum cr ys -tals , which itself redu ces the perme abili t y and blocks the pores. Accumulative salt -ma rsh soils show con-siderable difficulty in desalination due to the poor permeabil i ty, s ince some of the toxic salts are trapped inthe gypsum crystals .

In our experi ments , the permeabili ty in crea sed by a factor 1.4-1.5 on reducing the gypsum content from15 to 7%.

Previou s me asu rem ent s [3] have provided a basis for generalizing the fil tration and adsorption data todefine the relative changes in the fil tration coefficients for clay soils modified With poly mers , where there isa specific effect on the particle surface for K-9, PAA, and K-4 wate r-solu ble p olymer s.

These curves have been constructe d for the modified soil at optimal polym er levels , and values were cal-culated for the mean porosity using the fil tration coefficients for the unmodified soil with the appropriate poro-sity coefficients . The curve s were monotonic functions, and the ratios of the fil tration coefficients for themodified soil and unmodified soil for specific s urf ace s of 200-240 m2/g wer e c lose to 1. Howev er, the specificsurfac es of medium- grai ned loams and clays in the Hunger Steppe and the takyr-li ke clays in the Karsha steppelie in this ra nge.

We have found [1-3] that K-9, PAA, and K-4 are adsor bed at free hydro xyl groups via their carbox ylgroups, which tends to bind the particl es into clumps and thus increase the permeabili ty. The increase isdetermi ned by the number of adsorption centers (active groups) per unit length of the macromo lecul e as wellas by the number of free hydro xyl groups, in addition to any effect from the exchingeable cations per unit sur -face area. There are thus strong interactions between the polyme r and the solid, partic ularly for montmori l-lonite. Any exce ss content of carb oxyl groups resu lts in an additional content of charg ed par ticl es when thepore space is at the natural level (in contrast to a suspension), which causes repulsion between the particles,and thus dispersal of the aggregat es, which may reduce the permeabili t y, as occur s in kaolinite clays.

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Th e clay fraction in these soils in the mai n consists of hy dr om ica with a little aolinite and mont mori llo-nite.

Th e concentrations of active centers in such sys te ms are intermediate b etwe en those for mont mori llo-nite and kaolinite, whi ch me an s that the conditions are intermediate bet ween those discussed above, wh er econflicting endencies fr om the po ly me rs m ak e the msel ves felt.

Modification with a m ixt ure of irrigation at er and subsoil wa te r involves the introduction of additionalso di um ions~ these are ads orb ed b y the active centers, whi ch tends to disperse the particles and thus to re-duc e the permeability.

H o w e v e r , o u r m e a s u r e m e n t s s h o w e d t h a t t h e p e r m e a bi l i t y f a ct o rs w e r e u n c h a n g e d , a s w e r e t h e l e ve l sof exchan geable so di um in the wa sh ed and mod ified H un ge r Steppe soils, whi ch is ascribed to the effects ofg y p s u m i n t he a d s o r b e d c o m p l e x .

Th e calc ium in the gyp su m is displaced by the sodi um, whi ch reduc es the alkalinity f the soil and i m-pr ove s the physical properties, w hile causi ng irreversible coagulation of the colloids.

A so me wh at different situation occur s wit h takyr-like soils.T h e r e i s a n i n c r e a s e ( Ta b le 3 ) i n t he p e r m e a b i l i ty of t h e w a s h e d s p e c i m e n s , n a m e l y , b y 4 0 % b y c o m p a r i -

son wi th the initial alue, wh ic h is due to the elimination of gy p su m and the partial dissolution of the calciteand dolomite.

H o w e v e r , t h e s e c o n d a r y p r o c e s s i n g w i t h a m i x t u r e o f s a lt s d u r i n g th e m o di f ic a ti o n a n d s u b s e q u e n t w a s h -ing to negative chloride reaction results in the accumul ation of exchan geable so diu m (increased fr om 0.66 to2.33 mg -e q/ 10 O g, Tab le 1), with a reduction in the permeability coefficient y a factor of 1.4.

Modification of a takyr-like soil by subsoil wa te r or any other c ombi nati on of dissolved salts at highconcentrations ca n increase the salt contamination of the soil and ma rk ed ly reduc e the wat er permeability.

Theref ore, the salinity f water , obtained by mi xin g irrigation ate r and subsoil wate r in a ratio of 5:1,is such a s to hav e n o a dver se effects due to the accumul ation of exchangeable sod iu m in such a soil, and thereis no ap preciable deterioration in the wat er permeability, and therefore such a m ixtu re can be u sed at periodswh en irrigation at er is scarce.

L I T E R A T U R E C I T E D

1. P . P . Olodovskii and M. G. Murashko, In zh. -F iz . Zh., 30, No. 2 (1976).2. M. G. Murashko, P. P. Olodovskii, G. A. Ivkovskaya, T. M. Kolots ei, and L. L. Kolosov, in: Wat er-

Resource Utilization [in Russian], No. 3 (1975).3. P . P . Olodovskii, M. G. Murashko, A. B. Bogdanova, T. M. Malashko, R. F. Dots enko, and V. F.Kononyuk, Inz h. -F iz . Zh., 32, No. 4 (1977).4. E. V . Arinus hkina, Handbook on Chemical Analysis of Soils [in Russian ], MGU (!970).5. E. G . II'ko vskaya , Agronomi c Methods of Soil Examinat ion [in Russia n], AN SSSR (1954).

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