Limestone and Marble Dissolution by Acid Rain: An Onsite

15 Limestone and Marble Dissolution by Acid Rain: An Onsite Weathering Experiment 1

2

3

Michael M . Reddy , Susan I. Sherwood , and B. R. Doe 1

U.S. Geological Survey, Lakewood, CO 80225

2

Preservation Assistance Division, United States Park Service, Washington, D C 20006 U.S. Geological Survey, 12201 Sunrise Valley Drive, Reston, VA 22092

Downloaded by PURDUE UNIV on July 7, 2016 | http://pubs.acs.org Publication Date: September 25, 1986 | doi: 10.1021/bk-1986-0318.ch015

3

In this paper we describe an experimental research program, conducted in conjunction with the National Acidic Precipitation Assessment Program (NAPAP), to quantify acid-rain damage to commercial and cultural carbonate-rock resources. We are conducting a carbonate-rock onsite weathering experiment, using the change in rainfall-runoff composition to quantify the interaction of acid rain with a carbonate-rock surface. Initial results of this experiment show that carbonate -rock dissolution and associated surface recession increase with increasing acid deposition to the rock surface. The interaction of acid rain with carbonate rock has a stoichiometry, consistent with the reaction: +

2+

CaCO (solid) + H = Ca + HCO-3 3

A statistically significant linear relation has been found between carbonate-rock surface-recession rate and hydrogen ion loading to the rock surface. Weathering, and subsequent d e t e r i o r a t i o n o f rock exposed t o t h e environment, a r e slow p r o c e s s e s . Weathering r a t e s a r e i n f l u e n c e d by temperature, t h e p r e s e n c e o f m o i s t u r e , t h e p r e s e n c e o f o r g a n i c a c i d s , and t h e carbon d i o x i d e p a r t i a l p r e s s u r e i n t h e s o l u t i o n i n contact with the rock surface. I n contemporary i n d u s t r i a l s o c i e t i e s , n a t u r a l w e a t h e r i n g p r o c e s s e s a r e a c c e l e r a t e d by elevated pollutant concentrations. Acidic pollutants i n p a r t i c u l a r , i n b o t h a i r and r a i n f a l l , a r e r e c o g n i z e d as s e r i o u s hazards t o carbonate r o c k used i n commerce and c u l t u r a l r e s o u r c e s

ω-

This chapter not subject to U.S. copyright. Published 1986, American Chemical Society

Baboian; Materials Degradation Caused by Acid Rain ACS Symposium Series; American Chemical Society: Washington, DC, 1986.


15.

R E D D Y ET AL.

Limestone and Marble Dissolution by Acid Rain

227

In g e n e r a l , a c i d s p r e s e n t i n wet and d r y d e p o s i t i o n , and gaseous s u l f u r d i o x i d e ( i n t h e p r e s e n c e o f s u r f a c e m o i s t u r e ) a r e i m p o r t a n t agents c a u s i n g d e t e r i o r a t i o n o f l i m e s t o n e and marble (1). Damage may be t h e r e s u l t o f d i r e c t a c i d r e a c t i o n w i t h t h e r o c k s u r f a c e , o r i t may p r o c e e d t h r o u g h f o r m a t i o n o f secondary m i n e r a l phases, such as gypsum. Gypsum w i l l form on c a r b o n a t e r o c k s u r f a c e s , f o l l o w i n g d e p o s i t i o n o f gaseous o r d i s s o l v e d s u l f u r species. C a p i l l a r y t r a n s p o r t o f s u r f a c e s u l f a t e i n t o rock pores may cause rock-volume i n c r e a s e s , a c c e l e r a t i n g r o c k breakup. L i t t l e q u a n t i t a t i v e information i s a v a i l a b l e to assess the e f f e c t o f n o n s u l f u r - c o n t a i n i n g p o l l u t a n t s i n c a r b o n a t e - r o c k damage ( 1 ) ; however, t h e p r e s e n c e o f o r g a n i c a c i d s on t h e stone s u r f a c e , f o r example, c o u l d a c c e l e r a t e r o c k damage markedly. Mechanistic d e t a i l s o f carbonate-rock d e t e r i o r a t i o n i n p o l l u t e d environments a r e needed t o p r o t e c t and r e f u r b i s h s t r u c t u r e s and monuments a t r i s k t o a c i d r a i n and a i r p o l l u t i o n . F o r example, i f d i f f u s i o n o f r e a c t i o n p r o d u c t s away from t h e r o c k s u r f a c e i s l i m i t i n g the r a t e o f d i s s o l u t i o n , then modeling rock d e t e r i o r a t i o n , u s i n g s i m p l e c h e m i c a l models, w i l l be d i f f i c u l t . In t h e case o f a d i f f u s i o n - l i m i t e d r e a c t i o n , hydrodynamic f a c t o r s , such as t u r b u l e n t f l o w , may i n f l u e n c e t h e d i s s o l u t i o n p r o c e s s . H u m i d i t y f l u c t u a t i o n s a l s o may a l t e r t h e s o l u t e c o n c e n t r a t i o n s i n the m o i s t u r e f i l m a t t h e r o c k s u r f a c e , and t h e y may r e s u l t i n t h e d i s s o l u t i o n and r e c r y s t a l l i z a t i o n , n o t o n l y o f t h e c a r b o n a t e s , b u t a l s o o f t h e secondary m i n e r a l s , such as c a l c i u m s u l f a t e . Wetting and d r y i n g c y c l e s may l e a d t o measureable changes i n f l u i d c o m p o s i t i o n a t t h e stone s u r f a c e . In t h i s p a p e r , we d e s c r i b e an o n s i t e w e a t h e r i n g experiment designed t o i d e n t i f y a c i d - r a i n i n c r e a s e d d i s s o l u t i o n o f carbonate rock. T h i s experiment i s based on t h e measurement o f t h e change i n r a i n f a l l - r u n o f f c o m p o s i t i o n from t h e i n t e r a c t i o n o f a r o c k s u r f a c e w i t h i n c i d e n t a c i d r a i n ( 2 ) . The experiment i n v o l v e s c o n d u c t i n g l o n g - t e r m exposures o f two c o m m e r c i a l l y and c u l t u r a l l y important calcium carbonate dimension stones ( i . e . , Indiana Limestone (commercial name f o r Salem L i m e s t o n e ) and Vermont Marble (commercial name f o r S h e l b u r n e M a r b l e ) ) ( 3 - 5 ) • T h i s t e c h n i q u e appears t o g i v e a d i r e c t measurement o f t h e c h e m i c a l d i s s o l u t i o n o f c a r b o n a t e r o c k from t h e combined r e a c t i o n s o f wet and d r y deposition. P r e l i m i n a r y r e s u l t s from t h e i n i t i a l months o f o n s i t e operation are presented to i l l u s t r a t e the technique. M a t e r i a l s and Methods The o n s i t e experiments d e s c r i b e d i n t h i s paper a r e b e i n g conducted a t f o u r l o c a t i o n s i n t h e E a s t e r n U n i t e d S t a t e s : Newcomb, New York; C h e s t e r , New J e r s e y ; Washington, D.C.; and R e s e a r c h T r i a n g l e Park, N o r t h C a r o l i n a ( F i g u r e 1) ( 3 - 5 ) . E a c h s i t e has f o u r r o c k - e x p o s u r e r a c k s f a b r i c a t e d o f p o l y p r o p y l e n e . Racks c o n t a i n two stone s l a b s each ( F i g u r e 2 ) . Exposure r a c k s have been d e s i g n e d t o f a c i l i t a t e c o l l e c t i o n o f r u n o f f from t h e r o c k s u r f a c e w i t h a minimum o f c o n t a m i n a t i o n .


228


M A T E R I A L S D E G R A D A T I O N C A U S E D BY A C I D RAIN

F i g u r e 1. States.

Rock e x p o s u r e - s i t e

l o c a t i o n s i n the Eastern

United


AL.

Limestone and

Marble Dissolution by Acid Rain


R E D D Y ET

F i g u r e 2. A. An i s o m e t r i c p r o j e c t i o n o f a s i n g l e r e s e a r c h r o c k exposure r a c k . Racks a r e mounted i n p a i r s w i t h f o u r s e t s p e r location. B. A t y p i c a l completed r e s e a r c h r o c k - e x p o s u r e s i t e w i t h r e s e a r c h stones i n p l a c e .



230

M A T E R I A L S D E G R A D A T I O N C A U S E D BY A C I D RAIN

A p p r o x i m a t e l y one l i t e r o f r a i n f a l l - r u n o f f s o l u t i o n was c o l l e c t e d from each o f t h r e e e x p e r i m e n t a l r a c k s f o l l o w i n g r a i n f a l l events. Limestone and marble r e f e r e n c e r o c k s were i n two o f the r a c k s ; a t h i r d r a c k w i t h o u t a r o c k was used as a c o n t r o l ( h e r e i n a f t e r r e f e r r e d t o as a b l a n k sample). R u n o f f volume, s p e c i f i c c o n d u c t a n c e , and pH measurements were d e t e r m i n e d a t the exposure s i t e as soon as p o s s i b l e a f t e r c o l l e c t i o n , t y p i c a l l y w i t h i n a few hours. Samples t h e n were f i l t e r e d t h r o u g h a 0.45-micrometer p o r e s i z e membrane f i l t e r , p l a c e d i n a c l e a n p o l y e t h l y e n e b o t t l e , and s e n t t o the U.S. G e o l o g i c a l Survey l a b o r a t o r y i n Denver, C o l o r a d o , f o r c h e m i c a l a n a l y s i s . Sample p r e p a r a t i o n , a n a l y t i c a l p r o c e d u r e s , and l a b o r a t o r y q u a l i t y - c o n t r o l p r o t o c o l s a r e d e s c r i b e d by Skougstad e t a l . ( 6 ) . Each exposure s i t e has o t h e r m a t e r i a l s - d a m a g e e x p e r i m e n t s , i n a d d i t i o n t o those d i s c u s s e d i n t h i s r e p o r t £ 3 ) . To supplement a l l damage s t u d i e s , an a r r a y o f m e t e o r o l o g i c a l , c l i m a t o l o g i c a l , a i r - p o l l u t i o n , and r a i n f a l l - c h e m i s t r y d a t a a l s o w i l l be a v a i l a b l e f o r each s i t e . R e s e a r c h - r o c k - p r o c u r e m e n t i n f o r m a t i o n r e c e n t l y has been p u b l i s h e d ( 7 - 8 ) . Results R e s u l t s obtained at Research T r i a n g l e Park, North C a r o l i n a d u r i n g the l a s t h a l f o f 1985 a r e summarized i n T a b l e s I and I I . As a f i r s t a p p r o x i m a t i o n , because d a t a on d a i l y s u l f u r d i o x i d e conc e n t r a t i o n s and t i m e s - o f - w e t n e s s were n o t a v a i l a b l e , a n t e c e d e n t s u l f u r d i o x i d e l o a d i n g t o the stone s u r f a c e was e s t i m a t e d by m u l t i p l y i n g the average a t m o s p h e r i c s u l f u r d i o x i d e c o n c e n t r a t i o n by the number o f days between r a i n s t o r m s . A n a l y t i c a l r e s u l t s f o r s u l f a t e i o n s a r e f o r the n e t change i n r a i n f a l l c o m p o s i t i o n , a f t e r the r a i n f a l l f l o w s o v e r the s u r f a c e o f the exposed stone ( T a b l e s I and I I ) . The n e t c o n c e n t r a t i o n , r e s u l t i n g from the i n t e r a c t i o n o f r a i n w i t h the stone s u r f a c e , i s c a l c u l a t e d by s u b t r a c t i n g the blank-sample c o n c e n t r a t i o n v a l u e from the v a l u e measured f o r the stone r u n o f f . For very small r a i n amounts ( t y p i c a l l y 2 t o 4 m i l l i m e t e r s ) , b l a n k volumes were too s m a l l t o a l l o w complete c h e m i c a l a n a l y s i s . S u l f a t e i o n n e t c o n c e n t r a t i o n , i n e x c e s s o f t h a t p o s s i b l e from s u l f a t e l o a d i n g , was c a l c u l a t e d t o i d e n t i f y the p r e s e n c e o f s o l u b l e s u l f a t e c o n t a i n i n g m i n e r a l s on the r o c k s u r f a c e . Loss o f r o c k mass, measured by the c a l c i u m c o n c e n t r a t i o n i n the r u n o f f , i s e x p r e s s e d as s u r f a c e r e c e s s i o n , i n micrometers o f r o c k s u r f a c e l o s t p e r rainstorm. The n e t c a l c i u m c o n c e n t r a t i o n i n the r u n o f f s o l u t i o n i s c o n v e r t e d t o an e q u i v a l e n t volume o f r o c k removed; t h i s r e s u l t d i v i d e d by the s u r f a c e a r e a o f the exposed r o c k , y i e l d s a measurement o f s u r f a c e r e c e s s i o n ( 2 ) . Discussion R e l a t i o n between e n v i r o n m e n t a l v a r i a b l e s and s u r f a c e r e c e s s i o n . C a r b o n a t e - r o c k s u r f a c e r e c e s s i o n and the e n v i r o n m e n t a l v a r i a b l e s measured i n t h i s program ( i . e . , r a i n amount, r a i n pH, hydrogen i o n l o a d i n g t o the r o c k s u r f a c e , and a n t e c e d e n t s u l f u r d i o x i d e ) e x h i b i t e d a range o f v a l u e s a t the N o r t h C a r o l i n a s i t e d u r i n g the l a s t h a l f o f 1984. To examine q u a l i t a t i v e l y the r e l a t i o n between



1 2 4 5 6 7 8 10 11 12 13 14 16 21 26 28 30 31

U.S. Geological Survey Sample no. pH

4.53 3.98 4.43 4.19 4.38 4.04 4.46 4.27 5.55 4.06 4.91 4.71 4.49 4.30 4.67 4.51 4.35 3.83

Rainfall (millimeters)

17 16 41 17 5 3 32 29 46 7 4 6 55 21 2 10 51 2

0 12 16 12 16 12 12 4 4 4 16 8 16 40 20 4 4 4

Antecedent sulfur dioxide (parts per billion times d a y s )

1.00 .74 .67 .90 2.63 7.60 .00 1.00 -.15 2.35 5.50 1.60 1.10 .30 14.00 2.30 -.80 11.00

Net s u l f a t e ion i n runoff (milligrams per l i t e r )

0.50 1.63 1.51 1.07 .21 .23 1.10 1.57 .13 .58 .05 .11 1.77 1.07 .03 .31 2.27 .23

Hydrogen i o n loading (milliequivalents p e r meter squared)

0.13 .12 .21 .13 .04 .02 .19 .17 .17 .03 .02 .05 .35 .18 .02 .07 .30 .02

Surface recession (micrometers)

T a b l e I . R a i n f a l l q u a n t i t y and pH, a n t e c e d e n t s u l f u r d i o x i d e , n e t s u l f a t e , hydrogen i o n l o a d i n g , and s u r f a c e r e c e s s i o n f o r a marble r e f e r e n c e r o c k a t R e s e a r c h T r i a n g l e P a r k , N o r t h C a r o l i n a , June t o O c t o b e r 1984


MATERIALS DEGRADATION C A U S E D BY A C I D RAIN

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Limestone and Marble Dissolution by Acid Rain: An Onsite

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