AQUEOUS CHLORINATION PRODUCTS
u
,
y cThe Origin of Organochlorine Compounds
AQUEOUS CHLORINATION PRODUCTS
The Origin of Organochlorine Compounds
in Drinking and Surface Waters
PROEFSCHRIFT
ter verkrijging van de graad van doctor aan de Technische Universiteit Delft,
op gezag van de Rector Magnificus, prof .dr. J . M . Dirken, in het openbaar te verdedigen ten overstaan van een commissie
door het College van Dekanen daartoe aangewezen, op maandag 30 november 1987 te 16.00 uur
door
Everardus Wilhelmus Bartholomeus de Leer
scheikundig ingenieur geboren te Rotterdam
Delfts University Press/1987
TRdiss^
1590
Dit proefschrift is goedgekeurd door de promotor prof.dr. L. de Galan
STELLINGEN
1. In grafische voorstellingen van het "kalk-koolzuur" evenwicht, zoals de figuren van Tillmans, Guigues, of Caldwell en Lawrence, wordt ten onrechte niet, of op een incorrecte wijze, gecorrigeerd voor de ionensterkte van de oplossing.
American Water Works Association, Corrosion Control by Deposition of CaC03 Films, 1978.
L.D. Benefield, J.F. Judkins en B.L. Weand, Process Chemistry for Water and Wastewater Treatment. Prentice Hall, 1982.
Ontwerp NPR 6538, Nederlands Normalisatie Instituut, 1987.
2. Een wettelijke regeling voor de maximale grenswaarden van benzeen en gealkyleerde benzenen in drinkwater is dringend gewenst.
Nederlands Waterleidingsbesluit
EEG richtlijnen voor de drinkwaterkwaliteit
3. De gaschromatografische bepaling van het oliegehalte in grond volgens de voorlopige Nederlandse praktijkrichtlijn geeft slechts een fractie van het totale oliegehalte.
De oorspronkelijke infrarood methode verdient daarom, ondanks enkele bezwaren, de voorkeur.
Voorlopige Nederlandse Praktijkrichtlijn VPR C85-19 (1986).
H. De verklaring van Jackson en Haddad voor de systeempiek bij de "Single
Column Ion Chromatography" is niet correct.
P.E. Jackson en P.R. Haddad, J. Chromatogr. 3^6, 125 (1985).
5. Dougherty en Collazo-Lopez veronderstellen ten onrechte dat bij hun pyrolyse experimenten van polyvinylideenchloride voldoende zuurstof aanwezig is om een volledige verbranding van de pyrolyseprodukten te veroorzaken. De vermeende volledigere verbranding in aanwezigheid van calciumoxide moet verklaard worden door een adsorptie van de oorspronkelijk gevormde onvolledige verbrandingsprodukten, gevolgd door een langzame verbranding.
R.C. Dougherty en H. Collazo-Lopez, Environ. Sci. Technol. 2]_, 602
6. De afhankelijkheid van de maximale hoeveelheid trihalomethanen die gevormd kan worden bij gebruik van chloor of broom, kan eenvoudig verklaard worden door de instabiliteit van gebromeerde trihaloazijnzuren in waterig milieu.
B. Batchelor, D. Fusilier en E.H. Murray, J. Am. Water Works Assoc. 79(1), 50 (1987).
7. Het ontbreken van een relatie tussen het chloroform gehalte en de totale hoeveelheid organische stof in het water van whirlpools is absoluut niet verwonderlijk.
F.M. Benoit en R. Jackson, Wat. Res. _21_, 353 (1987).
8. De noodzaak van een tweetraps proces voor het oxideren van cyanide in afvalwater met chloor, wordt door Teo en Tan onvoldoende aangetoond. Bij hun beschrijving van de kinetiek van het proces wordt ten onrechte geen rekening gehouden met de gedeeltelijke vorming van nitraat.
W.K. Teo en T.C. Tan, Wat. Res. 21_, 677 (1987).
8. De door Savenhed e.a. gegeven verwijderingspercentages voor geosmine en 2-methylisoborneol bij coagulatie of infiltratie, zijn, door het onvoldoende scheidend vermogen van de gebruikte capillaire kolommen, niet betrouwbaar.
R. SSvenhed, H. Boren, A. Grimvall, B.V. Lundgren, P. Balmer, en T. Hedberg, Wat. Res. _21_, 277 (1987).
10. De gebruikelijke systemen die de moeilijkheid van rotsbeklimmingen weergeven, geven een onvoldoende inzicht in de werkelijke moeilij kheidsverschillen.
11. Het maatschappelijke besef van de naamsverandering van Technische Hogeschool Delft in Technische Universiteit Delft kan mogelijk versneld worden door de richtingsborden naar de TH-wijk te vervangen door borden met TU-wijk.
Voor Thea, Eva en Paul Aan mijn ouders
INHOUD
1. CHLORINATION OF DRINKING WATER. BENEFITS AND DOUBTS.
2. AQUEOUS CHLORINE CHEMISTRY. 5 2.1 Inorganic Reactions 5 2.2 The Reaction of Chlorine with Humic Material 8
2.3 Chlorination of Lignins 11 2.1) Chlorination of Amino Acids and Proteins 13
2.5 The Reaction of Chlorine with Carbohydrates 17 2.6 Reactions of Chlorine with Fatty Acids 18
2.7 Literature Cited 20
3. THE IDENTIFICATION OF ARYL-CHLORINATED AROMATIC ACIDS AND 23 INTERMEDIATES LEADING TO CHLOROFORM AND C-H DIACIDS IN THE
CHLORINATION OF TERRESTRIAL HUMIC ACID.
23 211 25 28 17 48
4. CHLOROFORM PRODUCTION FROM MODEL COMPOUNDS OF AQUATIC HUMIC 51 MATERIAL. THE ROLE OF PENTACHLORORESORCINOL AS AN INTERMEDIATE.
4.1 Summary 51 4.2 Introduction 52 4.3 Experimental Section 52
4.4 Results and Discussion 53
4.5 Conclusions 57 4.6 Literature Cited 58
5. THE CHLORINATION OF oj-CYANOALKANOIC ACIDS IN AQUEOUS MEDIUM 59 59 60 60 61 71 72 3.1 3.2 3.3 3.1 3.5 3.6 Summary Introduction Experimental Section Results and Discussion Conclusion Literature Cited 5 5 5 5 5 5 1 2 3 4 5 6 Summary Introduction Experimental Section Results and Discussion Conclusions
6. THE PRODUCTION OF CYANO-COMPOUNDS ON CHLORINATION OF HUMIC ACID. 73 6.1 6.2 6.3 6.il 6.5 6.6 6.7 Summary Introduction
Materials and Methods Results and Discussion Conclusion >■ Literature Cited
Appendix
A COMPARISON BETWEEN TERRESTRIAL AND AQUATIC MATERIAL.
7 3 71 74 76 7 9 79 80
7. THE INFLUENCE OF ORGANIC NITROGEN COMPOUNDS ON THE PRODUCTION 83 OF ORGANOCHLORINE COMPOUNDS IN THE CHLORINATION OF HUMIC
MATERIALS.
7.1 Summary 83 7.2 Introduction 81 7.3 Experimental Section 85
7.1 Results and Discussion 86
7.5 Conclusions 98 7.6 Literature Cited 99 8. THE IDENTIFICATION OF HIGHLY CHLORINATED ETHERS AND DIETHERS IN 101
RIVER SEDIMENT NEAR AN EPICHLOROHYDRIN PLANT
101 102 103 104 112 113 115 8.1 8.2 8.3 8.4 8.5 8.6 Summary Introduction Methods
Results and Discussion Conclusion
Literature Cited
SAMENVATTING
1. CHLORINATION OF DRINKING WATER. BENEFITS AND
DOUBTS
1.1 Introduction
Chlorine is used on a large scale for the treatment of water. Four major areas can be distinguished: drinking water treatment, wastewater treatment, cooling water treatment, and industrial processes. The latter includes a wide diversity of industrial processes, such as food treatment and pulp bleaching.
In drinking water treatment, chlorine can be used to remove ammonia by a breakpoint chlorination, to improve the color, odor, and taste by the chemical oxidation of organic material, to inactivate bacteria, viruses, and cysts by a disinfection, or to safeguard the bacteriological quality of the finished drinking water in the distribution system.
The use of chlorine for the disinfection of drinking water was introduced in 1902 in Middelkerke in Belgium. Other cities followed soon and chlorine became the most widely applied disinfectant in drinking water treatment and has helped to eliminate waterborne diseases such as typhoid and cholera from our Western world. The World Health Organization recommends that when chlorination is practised, the pH should preferably be less than 8.0 and the contact time greater than 30 minutes, resulting in a free chlorine residual of 0.2-0.5 mg/L [ 1 ] .
The present daily consumption of drinking water in The Netherlands is approximately 200 1/person (total production 1.05 billion m V y e a r ) , of which 66 % originates from ground water and 31* % from surface water [2]. Surface
water is used only in the western part of the country, where fresh ground water is scarce. The surface water is taken mostly from the rivers Meuse and Rhine and is used after bank filtration, dune infiltration, or storage in reservoirs. The Dutch law demands that surface water that is to be used for the preparation of drinking water, must be treated by a series of methods which depend on the quality of the raw water [3]. Surface water of the best quality (quality class I) may need only rapid sand filtration and disinfection, while a class III surface water will require an extensive chemical and physical treatment, which may include breakpoint chlorination,
coagulation, flocculation, filtration, adsorption on activated carbon, and disinfection. Surface water which does not meet the quality demands of a class III water is .not allowed to be used for the preparation of drinking water. In The Netherlands, drinking water prepared from ground water, meets in general the bacteriological standards at the consumer without relying on a safety chlorination. Chlorination of ground water is therefore not considered necessary and only exceptionally applied.
Water from the rivers Rhine and Meuse requires an extensive chemical and physical treatment. The production schemes for the water works of Rotterdam and Amsterdam _are given in Figure 1 [2,4],
i(
Coagulation Sedimentation Rapid Sand Filtration:
JL Transport Infiltration of Dunes PH Correction AerationI
1
Rapid Sand Filtration Slow Sand Filtration Pretreatment of river water at WRK -Nieuw eg tinTreatment process at dune waterworks of Amsterdam
-Storage Reservoirs
:
JL Transport Reservoir1
Coagulation Sedimentation1
Ozone Contact Chamberi
Dual Media Filter Activated Carbon Filter JL Product Water Reservoir. Treatment process at Rotterdam waterworks ■
Figure 1. Treatment process for t h e p r e p a r a t i o n of d r i n k i n g w a t e r at t h e
Amsterdam dune water works and t h e Rotterdam w a t e r works. Transport c h l o r i n a t i o n i s a p p l i e d only d u r i n g the summer, w h i l e Amsterdam r e c e n t l y stopped with p o s t - c h l o r i n a t i o n .
T r a d i t i o n a l l y , c h l o r i n e was used at d i f f e r e n t s t a g e s in t h e production p r o c e s s . However, i t s use was l i m i t e d r e c e n t l y t o t r a n s p o r t c h l o r i n a t i o n i n warm periods (Amsterdam and Rotterdam), and t o safeguard the b a c t e r i o l o g i c a l q u a l i t y in the d i s t r i b u t i o n system (Rotterdam o n l y ) . For example, i n Rotterdam the use of c h l o r i n e was reduced from 33.6 mg/L in 1972 t o 2.6 mg/L in 1984 [ 5 ] . This l a r g e r e d u c t i o n i n t h e c h l o r i n e dose was achieved by improvements in the q u a l i t y of t h e raw water and the p r o d u c t i o n p r o c e s s . S t o r a g e of r i v e r Meuse water i n r e s e r v o i r s , or dune i n f i l t r a t i o n of r i v e r Rhine water a f t e r c o a g u l a t i o n / f l o c c u l a t i o n produces a l a r g e r e d u c t i o n of t h e ammonia c o n t e n t , which has e l i m i n a t e d the need for a b r e a k p o i n t c h l o r i n a t i o n . D i s i n f e c t i o n i s achieved in s u c c e s s i v e t r e a t m e n t s t e p s which i n c l u d e ozone or slow sand f i l t r a t i o n .
The Amsterdam water works stopped with the s a f e t y c h l o r i n a t i o n in 1983 [ 6 ] . The c h l o r i n e dose was reduced s t e p w i z e from 0 . 1 - 0 . 8 mg/L t o z e r o . This
resulted in a reduction of the trihalomethanes content from 12-18 to 0 yg/L, and a reduction in the adsorbable halogenated organics (AOX) from 50-65 yg/L to 10-12 yg/L. Stopping with the "safety" chlorination did not result in an increase of the hygienic parameters of the finished water. Total coliforms, fecal streptococci, and sulphite reducing clostridia could not be detected in > 99? of the samples, and colony counts of the finished drinking water in the distribution system did not increase.
Despite the large efforts to prepare drinking water of an unquestionable bacteriological quality, outbreaks of bacterial growth in distribution systems are still reported at regular intervals. For example, the water works of The Hague had to start chlorination in the period of May 1981 until March 1985 because of an outbreak of Aeromonas hydrophila. Other microorganisms that are of concern in modern drinking water treatment are Legionella and Mycobacterium species [7].
Also in the USA, where chlorine is used on a much larger scale than in The Netherlands, waterborne infectious desease outbreaks still occur. In 1982, 40 epidemics with a total of 3456 cases of illness [8] were reported. In comparison to the annual 15 million children deaths due to waterborne diseases in developing nations [9], we are however, in a very privileged position.
Chlorination of wastewater and sewage effluents is applied in those cases where bacterial contamination of recreational water may occur or where the receiving water is used for culturing and harvesting of shellfish.
Chlorination of power plant cooling waters is used to prevent biofouling in the installations.
The discovery in 1974 of Rook [10] and Bellar and Lichtenberg [11], that chlorination of drinking water produces the trihalomethanes (CHC13, CHBrCl2, CHBr2Cl, CHBr3) has led to the awareness that chlorination also introduces health and environmental risks. Chlorine was shown to react with naturally occurring organic compounds such as humic and fulvic acids, producing chlorinated organic compounds, several of which were shown to be mutagenic or (suspect) carcinogenic.
The use of chlorine in drinking water treatment increases the mutagenicity of the water as indicated by the Salmonella microsome assay (Ames test) [12, 13]. Although the concentration of the organochlorine compounds produced is in the ng/L to yg/L range, the effects of a lifetime ingestion of these compounds with drinking water is not well understood. Chlorination of drinking water may increase the risk for colon, bladder, or rectum cancer.
However, epidemiological studies indicate that this risk is very low, and the drinking water in the Western world can be regarded in general as "chemically safe" [14].
However, drinking water authorities have developed the policy to reduce the use of chlorine as much as possible. Alternative oxidants such as chlorine dioxide or ozone may be used, or a combination of different unit operations may produce multiple barriers to protect drinking water from bacteriological contamination.
The next chapter gives an introduction to the chemistry of chlorine in aqueous medium and a review of the reactions between chlorine and naturally occurring biogenic organic substances, with an emphasis on the pathways leading to the production of organochlorine compounds.
1.2 Literature Cited.
1. World Health Organization "Guidelines for Drinking-Water Quality: Vol. 1 Recommendations"; Geneva, 1981.
2. Dijk-Looyaard, A.M. van; Kruijf, H.A.M. de In "Organic Micropollutants in Drinking Water and Health"; Kruijf, H.A.M. de; Kool, H.J., Eds.; Elsevier: Amsterdam, 1985, pp 59-82.
3. Wijziging Waterleidingbesluit (Stb. 1960, 345), February 28, 1983. 't. Veen, C. van der J. Am. Water Works Assoc. 1985(6), 77, 32-15. 5. Kuyt, B. HjO, 1985, JjB, 422-421.
6. J.A. Schellart, Wat. Supply 1986, _4, 217-225. 7. Kooy, D. van der H^O, 1987, 20, 6-11.
8. Olivieri, V.P. In "Water Chlorination: Chemistry, Environmental Impact and Health Effects", Jolley, R.L., et al., Eds.; Lewis Publishers, Chelsea, MI; 1985, Vol. 5, pp 5-18.
9. Zoeteman, B.C.J. Sci. Tot. Environ. 1985, 47, 487-503. 10. Rook, J.J. Water Treat. Exam. 1974, 23, 234-243.
11. Bellar, T.A.; Lichtenberg, J.J. J. Am. Water Works Assoc. 1974, £ 6 , 739-744.
12. Kool, H.J.; Hrubec, C.F.; Kreijl, C.F. van; Piet, G.J. In "Organic Micropollutants in Drinking Water and Health"; Kruijf, H.A.M. de; Kool, H.J., Eds.; Elsevier: Amsterdam, 1985, pp 229-256.
13. Gaag, M.A. van der; Kruithof, J.C.; Puijker, L.M. In "Organic Micropollutants in Drinking Water and Health"; Kruijf, H.A.M. de; Kool, H.J., Eds.; Elsevier: Amsterdam, 1985, pp 137-153.
14. Heijden, C A . van der; Kreijl, C.F. van In "Organic Micropollutants in Drinking Water and Health"; Kruijf, H.A.M. de; Kool, H.J., Eds.; Elsevier: Amsterdam, 1985, pp 479-485.
2. AQUEOUS CHLORINE CHEMISTRY
2.1 Inorganic Reactions
When chlorine is introduced into water it hydrolyzes very rapidly according to the following reaction:
Cl2 + H20 --> H0C1 + H+ + Cl" (1)
-4
The hydrolysis constant for this reaction is 4.0 * 10 at 25 °C and at neutral pH the forward reaction is essentially complete in about 0.2 s. The hypochlorous acid is a weak acid:
H0C1 + H20 — > H30+ + 0C1~ K = 3.2 * 1 0 ~8 at 25 °C (2)
The total free chlorine concentration in water is given as the sum of the concentrations of chlorine, hypochlorous acid and the hypochlorite ion. The distribution between these three forms of chlorine in aqueous medium is a function of the pH and the chloride concentration. A JC-pH distribution diagram for a typical total free chlorine concentration of 0.35 mg/L (5 yM/L) and a chloride concentration of 3 mM/L is given in Figure 1.
At the pH value of natural waters (7~8.5), H0C1 and OC1 will predominate and the fraction present as C l2 is negligeable. Because of its greater specific reactivity (H0C1 : OCl" = 10000 : 1) [1], H0C1 will be the most important reacting species in oxidation and chlorination reactions of organic compounds in natural waters. However, other reactive chlorine species such as the chlorinium ion (Cl ) , protonated hypochlorous acid (H20C1 ) , the trichloride ion (ClJ), and chlorine monoxide (C120), which are produced in very low concentrations may play an important role under specific conditions. The H20C1 ion is produced by protonation of H0C1 (eq 3 ) , and is probably responsible for acid catalyzed reactions of H0C1.
Its concentration as a function of the pH is given in the log C <--> pH diagram of Figure 1.
-»- pH - pH
Figure 1. pH-$C distribution and pH-logC distribution diagram for chlorine
species (Cl
2, H0C1, 0C1 , H
20C1 ) in aqueous medium. Total
chlorine concentration = 5 umol/L; chloride = 3 mmol/L.
The possibility of free radical species of chlorine participating in
chlorination reactions has been discussed by Rosenblatt [2], but in the
dilute aqueous solutions used in water chlorination t h i s p o s s i b i l i t y is
considered to be remote [ 1 ] .
Chlorine can be introduced into water in the form of chlorine gas or in
the form of a sodium or calcium hypochlorite solution (see Fig. 1).
Hydrolysis of chlorine gas produces hydrochloric acid and therefore will
tend to lower the pH of the solution. Introduction of sodium or calcium
hypochlorite will increase the pH, although, at the doses applied in
drinking water, an effect will be noticed only in waters with a very low
a l k a l i n i t y .
Chlorine is a very strong oxidant and reacts with many constituents in
water. Compounds like i r o n ( I I ) , manganese(II), n i t r i t e and sulfide are
rapidly oxidized. The chlorine demand of a water, the difference between the
chlorine concentration applied to a water and the residual concentration
after a certain contact time, is partly explained by these reactions.
Any trace of bromide in the water is rapidly oxidized to bromine, which
hydrolyses to hypobromous acid (eq H).
H0C1 + Br — > HOBr + Cl (t)
The hypobromous acid plays an important r o l e in the c h l o r i n a t i o n of n a t u r a l waters because both H0C1 and HOBr r e a c t with n a t u r a l l y o c c u r r i n g o r g a n i c compounds, producing mixed c h l o r i n a t e d and brominated compounds.
I n waters c o n t a i n i n g ammonia or o r g a n i c amines, chloroamines a r e produced. The primary r e a c t i o n product between c h l o r i n e and ammonia i s monochloroamine (NH2C1), which i s very s t a b l e i n aqueous s o l u t i o n at pH 7-8 (eq 5 ) . Addition of more than 1 eq of c h l o r i n e produces dichloroamine (NHC12) which i s s t a b l e only a t pH < 5 (eq 6 ) . At pH 7-8 i t r e a c t s with monochloroamine and decomposes i n t o n i t r o g e n and h y d r o c h l o r i c a c i d , producing t h e well known breakpoint c h l o r i n a t i o n e f f e c t (eq 6,7) [ 3 ] .
NH3 + H0C1 - " > NH2C1 + H20 (5)
NH2C1 + H0C1 - - - > NHC12 + H20 (6)
NH2C1 + NHC12 > N2 + 3 HC1 (7)
O v e r a l l r e a c t i o n : 2 NH3 + 3 H0C1 — > N2 + 3 H20 + 3 HC1 (8)
The p r o d u c t i o n of chloroamines may be viewed as a nucleophylic displacement of OH from H0C1 by ammonia or amines (eq 9 ) :
R-NH2 + C1-0H — > R-NH^-Cl + 0H~ > R-NH-C1 + H20 (9)
This n u c l e o p h y l i c i t y e f f e c t i s r e f l e c t e d in t h e r e a c t i v i t y of d i f f e r e n t amines towards c h l o r i n e . Alkylated amines and amino acids show a high r e a c t i v i t y , w h i l e amides and urea have a very low r e a c t i v i t y ( r e l . r e a c t i v i t y » 1 08 : 1 ) .
C h l o r i n e in t h e form of chloroamines i s c a l l e d combined c h l o r i n e and i s d i s t i n g u i s h e d a n a l y t i c a l l y from free c h l o r i n e because of i t s lower d i s i n f e c t i o n e f f i c a c y . The comparative e f f i c a c y of H0C1, 0C1 , NH2C1, and the a l t e r n a t i v e d i s i n f e c t a n t s C102 and 03, towards d i f f e r e n t microorganisms i s given in T a b l e I .
Table I. Comparative Efficacy of Disinfectants in the Production of 99 % Inactivation of Microorganisms.
E. coli Poliovirus I E. histolytica cysts|
Disinfec tant
pH temp. C*t pH temp. C*t pH temp. C*t
HOCl 0 C 1 -NH2C1 C102 03 6.0 10.0 9.0 6.5 7 . 0 5 5 15 15 12 0.04 0.92 64 0.38 0.002 6.0 10.5 ' 9 . 0 7.0 7.0 5 5 15 25 25 2.0 10.5 900 1.9 0.12 30 20 8 19 1 .5 temp, in °C; C in mg/L; t in min.
The mechanism of disinfection by chlorine is still under discussion. It is accepted that the neutral molecule HOCl penetrates the cell wall and subsequently reacts with one or more of the enzyme systems of the cell. Chlorine may react for example with thiol groups in proteins.
Viruses are in general more resistant to chlorine than bacteria. Their inactivation may be caused by denaturation of the capsid protein [4].
2.2 The Reaction of Chlorine with Humic Materials.
The production of chloroform, bromodichloromethane, dibromochloromethane and bromoform (trihalomethanes = THM's) during the chlorination of drinking water prepared from water from the rivers Rhine and Meuse, was reported by Rook in 1971 [5]. He also reported that there was a direct relation between the color of the water and the THM yield and suggested that humic materials are the precursors for the trihalomethanes. Since then, the reaction between chlorine and humic substances has been the subject of many investigations.
Humic substances in aqueous solution are divided into humic acids and fulvic acids. They are operationally defined as naturally occurring, biogenic, heterogeneous organic substances that can generally be characterized as yellow to black in color, of high molecular weight, and refractory. They can be isolated for example by adsorption onto polystyrene resins (XAD-type). Humic acids are not soluble in water below pH 2, but become soluble at higher pH. Fulvic acids are soluble under all pH conditions. Humic materials can be isolated from water or from soil and the aquatic or terrestrial origin of the material is emphasized in the name. The material however, is always a composite of varying proportions of
m i c r o b i o l o g i c a l l y degraded l i g n i n , c a r b o h y d r a t e s , f a t t y a c i d s , and p r o t e i n s , bound t o g e t h e r by p h y s i c a l f o r c e s or m i c r o b i o l o g i c a l l y induced o x i d a t i v e coupling r e a c t i o n s [ 6 ] . The f i n a l composition of the m a t e r i a l may show l a r g e l o c a l and s e a s o n a l v a r i a t i o n s . Because the humic m a t e r i a l s have no well defined s t r u c t u r e , t h e r e are many s t u d i e s where t h e c h l o r i n a t i o n products are compared w i t h t h o s e from model compounds.
The chloroform y i e l d a f t e r c h l o r i n a t i o n of humic m a t e r i a l s accounts for only a part of the t o t a l c h l o r i n a t e d p r o d u c t s . Oliver [7] s t a t e d t h a t chloroform probably r e p r e s e n t s the " t i p of the i c e b e r g " of c h l o r i n a t e d compounds produced by w a t e r c h l o r i n a t i o n . Depending on t h e pH the chloroform f r a c t i o n v a r i e d between 30 and 90 % of the t o t a l o r g a n i c c h l o r i n e for Spencer Creek f u l v i c a c i d .
The c h l o r i n a t e d p r o d u c t s a r e divided i n t o a v o l a t i l e and a n o n - v o l a t i l e f r a c t i o n . The v o l a t i l e products can be e x t r a c t e d with non polar s o l v e n t s such a s pentane or d i e t h y l e t h e r , and can be analyzed d i r e c t l y by gas chromatography. The v o l a t i l e c h l o r i n a t i o n products of humic m a t e r i a l s a r e summarized in Table I I :
Table I I . V o l a t i l e Chlorination Products of Humic Acid.
_ Product Reference Trihalomethanes: Rook [5] CHC13, CHBrCl2, CHBr2Cl, CHBr3 C h l o r a l : CC13-CH0 Rook [ 8 ] C h l o r i n a t e d a c e t o n e s : C12-C16 Rook [ 8 ] ; Coleman et a l . [ 9 ] C h l o r i n a t e d p r o p e n a l s : C1,-C1S Rook [ 8 ] ; Kringstad e t a l . [ 1 0 ] ; Coleman e t a l . [ 9 ] C h l o r i n a t e d butanones: C12-C15 Coleman et a l . [ 9 ] C h l o r i n a t e d a l k a n o l s : C„-C6, C ^ - C l j Rook [ 8 ] C h l o r i n a t e d i s o p r e n o i d a l c o h o l s : C^-Cl-, Havlicek e t a l . [11]
C h l o r i n a t e d a c e t o n i t r i l e s : Trehy and Bieber [ 1 2 ] ; Coleman
CHC12-CN, CCI3-CN et a l . [ 9 ]
T r i c h l o r o p r o p e n e n i t r i l e : CC12=CC1-CN Coleman et a l . [ 9 ] C h l o r o p i c r i n : CC13-N02 Merlet e t a l . [ 1 3 ]
-The f i r s t r e p o r t e d i d e n t i f i c a t i o n a f t e r c h l o r i n a t i o n of humic a c i d i s given. Most of the i d e n t i f i c a t i o n s have been confirmed by o t h e r a u t h o r s . Most of the n o n - v o l a t i l e products a r e c h l o r i n a t e d a c i d s , which may have very low pK values ( e . g . t r i c h l o r o a c e t i c a c i d , pK=0.5). They can be i s o l a t e d from the c h l o r i n a t i o n m i x t u r e s only a f t e r a c i d i f i c a t i o n t o pH « 0.5 and e x t r a c t i o n with polar s o l v e n t s such as e t h y l a c e t a t e or a d s o r p t i o n t o a c t i v a t e d carbon or m a c r o r e t i c u l a r r e s i n s such as XAD ^. To make them
amenable t o gas chromatographic a n a l y s i s they need t o be d e r i v a t i z e d with for example diazomethane.
Most of the work on the i d e n t i f i c a t i o n of n o n - v o l a t i l e c h l o r i n a t i o n products of humic and f u l v i c a c i d s has been described by the group of Christman in Chapel H i l l [ 1 4 - 1 7 ] .
They i d e n t i f i e d more than 100 d i f f e r e n t r e a c t i o n p r o d u c t s , most of them in low y i e l d . In a l l cases the product mixture was dominated by d i - and t r i c h l o r o a c e t i c a c i d , d i c h l o r o m a l o n i c a c i d , and 2 , 2 - d i c h l o r o s u c c i n i c a c i d , which t o g e t h e r with chloroform accounted for 53 % of t h e TOCl. Apart from c h l o r i n a t e d p r o d u c t s , Christman e t a l . a l s o i d e n t i f i e d a l a r g e number of non c h l o r i n a t e d c a r b o x y l i c a c i d s such as mono and d i b a s i c a l k a n o i c a c i d s , benzene c a r b o x y l i c a c i d s (up t o benzenehexacarboxylic a c i d ) , and carboxyphenylglyoxylic a c i d s . C h l o r i n a t e d s a l i c y l i c a c i d s were d e t e c t e d by Seeger et a l . [ 1 8 ] .
The q u a n t i t a t i v e d e t e r m i n a t i o n of t r i c h l o r o a c e t i c a c i d (TCA), t h e most important c h l o r i n a t i o n product in d r i n k i n g w a t e r , has r e c e i v e d s p e c i a l a t t e n t i o n . Quimby et a l . [19] e x t r a c t e d TCA at pH 1 with e t h y l e t h e r , and a f t e r methylation with diazomethane, they analyzed with c a p i l l l a r y GC with an atmospheric p r e s s u r e helium microwave emission d e t e c t o r . M i l l e r e t a l .
[ 2 0 , 2 1 ] extended t h i s method by u s i n g a precolumn t r a p enrichment, which gave a d e t e c t i o n l i m i t of 2 yg/L from a 500 mL sample. To ensure complete e x t r a t i o n they lowered t h e pH of the r e a c t i o n m i x t u r e t o 0 . 5 and s a t u r a t e d i t with NaCl.
Lahl et a l . [22] a c i d i f i e d t o pH 0.5 and e x t r a c t e d TCA with d i i s o p r o p y l e t h e r . After m e t h y l a t i o n with BF3/CH30H they analyzed with c a p i l l a r y GC and e l e c t r o n c a p t u r e d e t e c t i o n , which gave a d e t e c t i o n l i m i t of 1 yg/L. In waters with a high bromide c o n c e n t r a t i o n they a l s o d e t e c t e d t r i b r o m o a c e t i c a c i d , but no mixed halogenated a c i d s .
A very e l e g a n t procedure which circumvents the problems with the q u a n t i t a t i v e recovery and e s t e r i f i c a t i o n , was described by Norwood e t a l . [ 1 7 , 2 3 , 2 4 ] , They use a method based on i s o t o p e d i l u t i o n gas chromatography-mass s p e c t r o m e t r y . Before t h e sample i s worked up, a p r e c i s e amount of l 3C ! ~ t r i c h l o r o a c e t i c a c i d i s added which s e r v e s as the i n t e r n a l s t a n d a r d . Q u a n t i t a t i o n was based on t h e a r e a r a t i o of the ions a t m/z 141 and 142 (CC12-C00CH3+ and CClj-13C00CH3 + ) . A l i n e a r s t a n d a r d curve was observed over approximately t h r e e o r d e r s of manitude in TCA c o n c e n t r a t i o n (5-1000 y g / L ) .
In drinking water TCA c o n c e n t r a t i o n s up t o 54 yg/L have been d e t e c t e d , which accounted for 2-10 % of the TOCl. In c h l o r i n a t e d raw w a t e r s much higher c o n c e n t r a t i o n s have been d e t e c t e d (up t o 2120 yg/L) and t o g e t h e r with
chloroform i t accounted for 31 "62 % of the T0C1. In most cases the molar c o n c e n t r a t i o n of TCA i s e q u i v a l e n t t o or higher than t h e chloroform c o n c e n t r a t i o n .
2.3 C h l o r i n a t i o n of L i g n l n s .
A major p o r t i o n of humic and f u l v i c a c i d s i s an aromatic polymeric m a t e r i a l , t h a t o r i g i n a t e s from biodegraded wood [ 6 ] . The l i g n i n of t h e woody m a t e r i a l t h a t c o n t r i b u t e s t o a p a r t i c u l a r humic or f u l v i c a c i d , i s held r e s p o n s i b l e for most c h l o r i n a t i o n p r o d u c t s .
L i g n i n i s e s s e n t i a l l y an a r o m a t i c polymer formed by an enzyme induced p o l y m e r i z a t i o n of a mixture of p-coumaryl a l c o h o l , c o n i f e r y l a l c o h o l , and s i n a p y l a l c o h o l . The p r o p o r t i o n of t h e s e a l c o h o l s v a r i e s with d i f f e r e n t wood s p e c i e s . For example, softwood l i g n i n i s l a r g e l y a p o l y m e r i c1' i o n product of c o n i f e r y l a l c o h o l . A p a r t of the l i g n i n s t r u c t u r e as suggested by Adler [25] i s given in eq 10. HjCOH H C 0 -I HCOH JM) H C 0 -ICH;0H] H t = 0 M j C O ' , HC 0 CH H, C 0 H 0 X I HC ( f S \ I CM
J^
H,C0H — CH I HCOH 0 H0CH1( H C -I H C -H j C O ^ Y -HCO-H H;C0H ' HC I HCOH CH HfO^Y^-OHH, OCH, nVÜ MÉ
HOCH, H j [ 0. HC 0 H j C O ' ^ H^0 H " f " ! Hf< 0 CH HC 0 HCOH t=U HJC 0 ' ^ ^ * N HjCO' HO^C-C-C^O ■OCH) M ] C 'U vC M I I HiCOH HC CH (10) OCH, OH 1 0 - C lThe phenylpropane u n i t s are l i n k e d by d i f f e r e n t bonds, which include e t h e r bonds ' of a l k y l - a r y l , a l k y l - a l k y l , and a r y l - a r y l c o n f i g u r a t i o n s . The c h l o r i n a t i o n products of l i g n i n have been s t u d i e d e x t e n s i v e l y [ 2 6 ] , s i n c e the b l e a c h i n g of p u l p (removal of r e s i d u a l l i g n i n ) with c h l o r i n e i s an e s s e n t i a l s t e p in t h e p r e p a r a t i o n of paper f i b e r s . The bleaching of pulp i s c a r r i e d out in s u c c e s s i v e t r e a t m e n t s with c h l o r i n e (C), a l k a l i ( E , ) , h y p o c h l o r i t e (H), c h l o r i n e dioxide ( D j ) , a l k a l i (E2) and c h l o r i n e dioxide
( D2) . C h l o r i n e consumption i s about 60-70 k g / t o n i n t h e C - s t a g e . The whole b l e a c h i n g process r e s u l t s i n the l o s s of about 70 kg of m a t e r i a l per t o n of p u l p . About 50 kg of t h i s m a t e r i a l o r i g i n a t e s from r e s i d u a l l i g n i n , and most of i t i s d i s s o l v e d in t h e C and E1 s t a g e s .
The s p e n t l i q u o r s from the c h l o r i n a t i o n and a l k a l i e x t r a c t i o n c o n t a i n an extremely complex mixture of o r g a n i c compounds with about 4 k g / t o n of o r g a n i c a l l y bound c h l o r i n e . About 70-90 % of the o r g a n i c a l l y bound c h l o r i n e i s p r e s e n t as high molecular mass m a t e r i a l (M > 1000).
The composition of the high molecular weight m a t e r i a l was s t u d i e d by o x i d a t i v e degradation t e c h n i q u e s [ 2 2 ] . The r e s u l t s i n d i c a t e t h a t the c o n t e n t of aromatic n u c l e i i s s u r p r i s i n g l y low, and t h a t the major p a r t of t h e m a t e r i a l c o n s i s t s of c r o s s - l i n k e d , u n s a t u r a t e d a l i p h a t i c compounds [ 2 6 ] . Also, c o n s i d e r a b l e demethylation as compared with the o r i g i n a l l i g n i n o c c u r s .
The c h l o r i n a t e d low molecular mass m a t e r i a l can be d i v i d e d i n t o n e u t r a l compounds, a c i d s , and phenols. In t h e n e u t r a l f r a c t i o n t h e v a r i o u s c h l o r i n a t e d a c e t o n e s , p r o p e n a l s , chloroform, dichloromethane and 1 , 1 -dichloromethyl s u l f o n e predominate [ 2 8 ] . The t o t a l chloroform p r o d u c t i o n may be as high as 250 g / t o n i f a H-stage i s included i n t h e b l e a c h i n g p r o c e s s . B i o l o g i c a l treatment of the e f f l u e n t of k r a f t m i l l s removes most of the n e u t r a l compounds, however t h e 1 , 1 - d i c h l o r o d i m e t h y l s u l f o n e i s very r e s i s t a n t .
The spent l i q u o r s of the bleaching process show a mutagenic e f f e c t i n t h e Ames t e s t . In t h e s e a r c h for t h e a c t i v e compound or compounds, Holmbom et a l . [ 2 9 , 3 0 ] used a HPLC f r a c t i o n a t i o n scheme, followed by s e p a r a t i o n of the a c t i v e f r a c t i o n s with GC/MS. The a c t i v e compound was c a l l e d mutant X, or "MX", and was f i n a l l y i d e n t i f i e d as 3 c h l o r o 4 ( d i c h l o r o m e t h y l ) 5 h y d r o x y -2(5H)-furanone (eq 1 1 ) . CHCI2 Cl CHCl2 Cl
c = c ^ c = c
0 = C C00H ^ c C H H ^ 0 ^ MX Furanone-Form = 0 (11)MX i s p r e s e n t in t h e open form at pH > 7, w h i l e a t low pH r i n g c l o s u r e t o t h e furanone s t r u c t u r e occurs [ 3 1 ] . The E-isomer i s c a l l e d EMX. Both MX and EMX have a l s o been i d e n t i f i e d as c h l o r i n a t i o n products of humic a c i d . R e c e n t l y , MX has a l s o been i d e n t i f i e d in d r i n k i n g w a t e r s , where i t may account for approximately 50 % of the m u t a g e n i c i t y found i n d r i n k i n g water a f t e r c h l o r i n a t i o n [ 3 2 ] .
C h l o r i n a t e d a c i d s in t h e bleaching l i q u o r s have been d e t e c t e d by Lindström and O s t e r b e r g [ 3 3 ] . Di- and t r i c h l o r o a c e t i c a c i d predominated (approximately 125 g / t o n of pulp) but c h l o r i n a t e d a c r y l i c , m a l e i c , and fumaric a c i d s a r e a l s o found. The production of c h l o r i n a t e d phenols i n the b l e a c h i n g of pulp i s w e l l known [ 3 l ~ 3 6 ] . C h l o r i n a t e d phenols, g u a i a c o l s , v a n i l l i n s , c a t e c h o l s , s y r i n g o l s , and s y r i n g a l d e h y d e s have been d e t e c t e d .
2 . 1 C h l o r i n a t i o n of Amino Acids and P r o t e i n s .
Surface and ground waters normally c o n t a i n up t o 2 mg/L of Kjeldahl n i t r o g e n [37] a l t h o u g h , under s p e c i a l circumstances such a s bloom of b l u e -green a l g a e , t h i s l e v e l may i n c r e a s e t o over 20 mg/L [ 3 8 ] . Most of t h i s d i s s o l v e d n i t r o g e n i s p r o t e i n a c e o u s m a t e r i a l and i s a s s o c i a t e d with the humic and f u l v i c a c i d s . The c o n c e n t r a t i o n of f r e e amino a c i d s i s on average 100 - 300 yg/L [ 3 7 , 3 9 , 1 0 ] .
The c h l o r i n a t i o n of amino a c i d s , p e p t i d e s and p r o t e i n s has been s t u d i e d s i n c e 1909 [ 1 1 ] , when Langheld r e p o r t e d t h a t t h e predominant r e a c t i o n of an a-amino acid with aqueous c h l o r i n e i s a c h l o r i n a t i o n of the amino group followed by a decarboxylat ion t o give t h e corresponding aldehyde with e l i m i n a t i o n of carbon d i o x i d e and ammonia (eq 1 2 ) .
R-CH-COOH - - ~ i _ > R-CH-C00H --*—> R-CHO + NH3 + C02 (12)
I I
NH2 NHC1
S u b s e q u e n t l y , Dakin [ 1 2 , 1 3 ] demonstrated t h a t one e q u i v a l e n t of chloramine T (sodium s a l t of N-chloro-p-toluenesulphonamide) converted a-amino a c i d s t o t h e i r c o r r e s p o n d i n g a l d e h y d e s , w h i l e i f two e q u i v a l e n t s of r e a g e n t were used the c o r r e s p o n d i n g n i t r i l e s r e s u l t e d (eq 1 3 ) .
R-CH-C00H - - - - ~ i - > R-CN + C02 (13)
I
NH2
The f o r m a t i o n of n i t r i l e s predominates under a c i d c o n d i t i o n s , while t h e production of aldehydes occurs p r i m a r i l y under n e u t r a l or a l k a l i n e c o n d i t i o n s [ 1 1 - 1 6 ] .
The mechanism for the formation of aldehydes or nitriles is still under debate, but it is generally accepted that mono- and dichloroamines play a crucial role as intermediates. An electronic rearrangement of the N-chloroamine leads to the formation of HC1, CO,, and the corresponding imine. The unstable imine may hydrolyze directly to the aldehyde, but Le Cloirec and Martin [40] propose first an addition of H0C1 to the C=N double bond, followed by a rearrangement to produce the aldehyde and chloroamlne (eq 14).
HOCl ' ^ R-CH-COOH — R — CHf rn — * - R - C H = NH+C07 + HCl I ^ N H ^C' 2 NH-
'2
0 H I , 0 HOCl ' * R-CH=NH — R - C - N H C l R - C ♦ NH,Cl (14) I SH 2 HThe production of n i t r i l e s i s assumed t o proceed through a N,N-dichloroamine i n t e r m e d i a t e which produces a N-chloroimine a c c o r d i n g t o a mechanism s i m i l a r t o t h e production of t h e imine from t h e chloroamlne (eq 1 5 ) . E l i m i n a t i o n of HC1 from t h e N-chloroimine gives t h e n i t r i l e .
A l t e r n a t i v e l y [ 4 0 ] , t h e n i t r i l e may be produced from a n u c l e o p h y l i c a d d i t i o n of chloroamine t o the aldehyde (eq 1 6 ) .
2H0CI -CO? R-CH-COOH —R-CH-COOH 7 7 7 * - R-CH = N-Cl I i NH2 NCl2 -HCl R-C = N+HCl (15) 0 OH * 0 i ® 1 R-Cs +NH2Cl ^ . R - C - N H7C l — R-C-NHCI H l i l i H H - H20 — ^ - R - C H = N - C l R - C E N (16)
C h l o r i n a t i o n r e a c t i o n s i n the s i d e chain of the amino a c i d s were r e p o r t e d by P e r e i r a e t a l . [ 1 7 ] who d e s c r i b e d t h e chemical a c t i o n of aqueous H0C1 on among o t h e r s t y r o s i n e and c y s t e i n e . Tyrosine y i e l d e d s e v e r a l r i n g c h l o r i n a t e d ( M - h y d r o x y - p h e n y l ) - a c e t o n i t r i l e s such as the 3 '-c h l o r o - and 3 ' , 5 ' - d i c h l o r o - d e r i v a t i v e s , while c y s t e i n e and c y s t i n e were o x i d i z e d t o c y s t e i c a c i d (eq 1 7 , 1 8 ) . H0-C$H„-CH2-CH-CO0H -——-> H0-C6H3C1-CH2-CN + H0-C6H2C12-CH2-CN (17)
I
NH2 HS-CH2-CH-C00H - ~ 2 i _ > H03S-CH2-CH-C00H ( 1 8 )I I
NH2 NH2The r e a c t i o n of c h l o r i n e with t y r o s i n e was l a t e r r e i n v e s t i g a t e d in d e t a i l by Burleson et a l . [ 1 8 ] and Trehy e t a l . [ 3 9 ] , who confirmed t h e proposed s t r u c t u r e s by GC/MS u s i n g tandem mass s p e c t r o m e t r y in t h e daughter ion mode.
Of s p e c i a l i n t e r e s t i s t h e c h l o r i n a t i o n of a s p a r t i c a c i d , s i n c e Trehy and Bieber [ 1 9 , 5 0 ] d e s c r i b e d the production of d i c h l o r o a c e t o n i t r i l e in t h e c h l o r i n a t i o n of many s u r f a c e w a t e r s . A s p a r t i c a c i d r e a c t s very r a p i d with aqueous c h l o r i n e t o produce d i c h l o r o a c e t o n i t r i l e , probably through
c y a n o a c e t i c a c i d and d i c h l o r o c y a n o a c e t i c a c i d a s h y p o t h e t i c a l i n t e r m e d i a t e s , which however have never been d e t e c t e d i n aqueous c h l o r i n a t i o n s (eq 19) H00C-CH2-CH-COOH —> H00C-CH2-CN --> H00C-CC12-CN —> CHC12-CN (19)
I
NH2
Most aliphatic amino acids show no chlorination in the side chain and produce the corresponding nitriles or aldehydes. However, a systematic study of the side chain chlorination products of all amino acids has not yet appeared, and much remains to be done for reactive amino acids such as tryptophane, histidine, methionine and arginine.
Recently [39,51] it has become evident that the chlorination of amino acids also may result in the production of chloroform, especially at high pH. Tryptophane produces a 100? molar yield of chloroform at pH 11, while under the same conditions proline produces a 30$ molar yield. These reactions probably proceed through chloral as an intermediate which hydrolyzes to chloroform at high pH.
Another important reason for a further study of the chlorination products of amino acids is the detection of mutagenicity after chlorination of several amino acids [52], including methionine and tyrosine. In the case of
t y r o s i n e t h e p r o d u c t i o n of t h e very potent mutagen MX may be r e s p o n s i b l e for t h i s e f f e c t [ 5 3 ] .
In c o n t r a s t t o t h e study of t h e a c t i o n of HOCl on a-amino a c i d s , t h e r e a c t i o n s between HOCl and p e p t i d e s or p r o t e i n s has r e c e i v e d comparatively l i t t l e a t t e n t i o n . Although t h e mechanism i s not w e l l understood t h e r e a c t i o n between c h l o r i n e and p e p t i d e s or p r o t e i n s i s used for t h e i r d e t e c t i o n on t h i n l a y e r chromatograms [ 5 4 ] . After exposure t o c h l o r i n e gas t h e p l a t e s a r e sprayed with a s t a r c h - K I s o l u t i o n which produces blue s p o t s for p e p t i d e s , p r o t e i n s , d i k e t o p i p e r a z i n e s and a c y l a t e d amino a c i d s . L a t e r [ 5 5 ] , t h i s method was improved by using t - b u t y l h y p o c h l o r i t e , which i s assumed t o c h l o r i n a t e the amide n i t r o g e n of p e p t i d e s and p r o t e i n s .
P e r e i r a et a l . [1)7] s t u d i e d t h e c h l o r i n a t i o n of s e v e r a l d i p e p t i d e s and concluded t h a t N - c h l o r i n a t i o n on t h e t e r m i n a l free amino group was the predominant r e a c t i o n . The amide n i t r o g e n of t h e p e p t i d e bond was found t o be r e s i s t a n t t o aqueous HOCl at room t e m p e r a t u r e . The same c o n c l u s i o n s were r e a c h e d by Stelmaszynska and Z g l i c z y n s k i [56] in t h e i r s t u d y of the c h l o r i n a t i o n of d i p e p t i d e s using t h e m y e l o p e r o x i d a s e / H202/ C l system. The t e r m i n a l N - c h l o r o p e p t i d e s or N , N - d i c h l o r o p e p t i d e s decomposed t o produce
N-(2-oxoacyl)amino a c i d s or n i t r i l e s and f r e e C - t e r m i n a l amino a c i d s (eq 2 0 ) .
0
H f l
0 0R . - C H - C - N H - C H - C O O H - ^ R T - C - C - N H - C H - C O O H + N H A + C r
NHCl R
2R
20
II H-jOR
1-CH-C-NH-CH-C00H-i»-R
1-C=N*C0
9+H
7N-CH-C00H (20)
1I I '
lI
NCl
2R
2 R2
Heltz et al. [57] demonstrated that chlorination of natural waters gave a general loss of proteinaceous material, as well as a more pronounced loss of specific amino acids that possess reactive side groups (lysine, histidine, arginine, methionine, and tyrosine). They also proposed that degradation of the side chains might lead to chain fission, resulting in smaller peptide fragments. No chlorinated products were detected, but Mallevialle et al. [37] demonstrated the incorporation of chlorine in protein material by pyrolysis-GC-MS. Chloroform was observed as the only chlorinated fragment, which suggested that no fixation of chlorine onto aromatic rings occurred. Scully et al. [58] demonstrated that chlorination of proteins in natural
waters may lead to the production of trihalomethanes. The molar yield (M CHC13/M C) varied between 0.2 and 0.5 %, which is lower than figures found
for humic and fulvic acids (0.7 - 2 % ) . However, the contibution of proteins
to the trihalomethane production of natural waters could not be neglected, especially during summer months of high algae growth.
The production of non-volatile organochlorine compounds from the chlorination of proteinaceous material remains to be studied.
2.5 The Reaction of Chlorine with Carbohydrates
The halogens are widely used as oxidants in the field of carbohydrate chemistry [59]. Bromine and iodine are particularly useful in the preparation of aldonic acids from aldoses and of aldaric acids from glycuronic acids (eq 2 1 ) .
CHO C00H CH0 C00H
I ! I I
(CH
90H) — (CHoOH) (CHoOH) — (CH
70H) (21)
^ n ^ n * n * n
I I I I
CH
20H CH
20H C00H C00H
Aldose Aldonic Glycuronic Aldaric
acid 'acid acid
Iodine in alkaline medium is even used as a reagent for the quantitative determination of aldehyde groups in sugars, because ketoses are essentially inert under these conditions. Under more severe conditions (temperature, time, concentration oxidant, pH) chlorine and bromine will also oxidize C-C bonds, resulting in chain shortening for both aldoses and ketoses, for example (eq 2 2 ) :CHO CHOH CHO C00H C0
2I II I I
CHOH — — COH — — C=0 — C = 0 — - CHO - ^ C00H (22)
I n the case of p o l y s a c c h a r i d e s the i n i t i a l a c t i o n of o x i d i z i n g a g e n t s such a s c h l o r i n e w i l l probably involve the o x i d a t i o n of secondary hydroxyl g r o u p s . This o x i d a t i o n w i l l be followed by c r o s s l i n k i n g through i n t e r r e s i d u e and i n t e r c h a i n hemiacetal or hemiketal f o r m a t i o n , as w e l l as some d e g r a d a t i o n s r e s u l t i n g i n g l y c o s i d e bond cleavage [ 6 0 ] .
The production of organohalogen compounds a f t e r r e a c t i o n of halogens with c a r b o h y d r a t e s i s only e x c e p t i o n a l l y r e p o r t e d in t h e l i t e r a t u r e . Oxidation of f r u c t o s e and i n u l i n (the p o l y s a c c h a r i d e of f r u c t o s e ) with bromine [61] y i e l d e d bromoform, o x a l i c a c i d , and g l y c o l i c a c i d . The production of bromoform was a l s o r e p o r t e d in t h e a c t i o n of bromine in a c i d medium on g l y c e r o l [ 6 2 ] . A p o s s i b l e pathway (eq 23) for t h e bromoform p r o d u c t i o n was given by Crane et a l . [ 6 3 ] :
+
R-CH0H-CH20H ----> R-C0-CH20H ~—> R-C0-CH20H2 + - - - - > R-C0-CH2Br
_Haloform_> +
r e a c t i o n 3
Crane et a l . a l s o d e t e c t e d t h e production of chloroform i n the c h l o r i n a t i o n of marine a l g a l b y p r o d u c t s , which i n c l u d e d D-mannitol. C h l o r i n a t i o n of mannitol a t pH 7 and a d d i t i o n of hydroxide a f t e r r e a c t i o n times of 4-24 h produced chloroform and an u n i d e n t i f i e d c h l o r i n a t e d p r o d u c t . No y i e l d s were given. A p o s s i b l e pathway for the chloroform production was proposed (eq 2 4 ) , which included t h e formation of a k e t o l a c t o n e , which i s converted in a a - c h l o r i n a t e d keto a c i d by a n u c l e o p h y l i c s u b s t i t u t i o n with c h l o r i d e :
H0CH2(CH0H)„CH20H - - « - - - > HOOC(CHOH) 2COCH0HCOOH --—*•-> H00C(CH0H),C0CH20H -~^i?-> CO(CHOH) 2C0CH2~r -£i-_>
I
0 1
H00C(CH0H)2C0CH2C1 - - - ~ £ ? ~ - > HOOC(CHOH) 2C00H + HCC13 (24)
i 63.CC-1 Oil
The production of organochlorine compounds in the chlorination of carbohydrates probably needs further investigation, especially since other highly oxygenated compounds such as citric acid produce chloroform in high yield [64].
2.6 Reactions of Chlorine with Fatty Acids
Fatty acids, mainly originating from natural sources, have been shown to be present in free form in many raw and drinking waters over a wide range of
c o n c e n t r a t i o n s [ 6 5 , 6 6 ] . F a t t y a c i d s can a l s o be present in n a t u r a l waters bound t o humic s u b s t a n c e s , probably in the form of an e s t e r [ 6 7 ] .
S a t u r a t e d f a t t y a c i d s a r e s t a b l e under aqueous c h l o r i n a t i o n c o n d i t i o n s [ 6 8 ] . However, c h l o r i n e r e a c t e d r a p i d l y with u n s a t u r a t e d f a t t y a c i d s or f a t t y a c i d e s t e r s [ 6 9 ] . The r e a c t i o n r a t e i n c r e a s e s with an i n c r e a s i n g number of double bonds and the r e a c t i o n r a t e order in a pH 6 phosphate
buffer was: o l e i c a c i d < l i n o l e i c a c i d < l i n o l e n i c acid < a r a c h i d o n i c a c i d . E s t e r i f i c a t i o n causes a s h a r p drop i n r e a c t i v i t y , although the r e l a t i o n s h i p between u n s a t u r a t i o n and r e a c t i v i t y was m a i n t a i n e d .
The i n c o r p o r a t i o n of c h l o r i n e in t h e r e a c t i o n products was s t u d i e d using H036C1 [ 7 0 ] , When a l l the c h l o r i n e had r e a c t e d , only 10,1? of the c h l o r i n e as 36C1 was i n c o r p o r a t e d i n t o o l e i c a c i d , w h i l e 29,1$ was i n c o r p o r a t e d i n t o a r a c h i d o n i c a c i d . T h e r e f o r e , most of the c h l o r i n e was used for o x i d a t i o n . The t o t a l c h l o r i n e i n c o r p o r a t i o n was d i r e c t l y p r o p o r t i o n a l with t h e number of double bonds in t h e m o l e c u l e . C h l o r i n e i n c o r p o r a t i o n per double bond a l s o i n c r e a s e d slowly w i t h number of double bonds in t h e molecule, i n d i c a t i n g a s y n e r g i s t i c e f f e c t for t h e double bonds in t h e f a t t y a c i d s .
The c h l o r i n a t i o n p r o d u c t s of o l e i c a c i d were i n v e s t i g a t e d with GC/MS [ 7 0 ] . The major product was i d e n t i f i e d a s 9 - c h l o r o , 10-hydroxyoctadecanoic a c i d
( i n t h e form of t h e methyl e s t e r a f t e r d e r i v a t i z a t i o n ) , i n d i c a t i n g an e l e c t r o p h y l i c a d d i t i o n mechanism of H0C1 (eq 2 5 ) .
HOC 1
CH3-(CH2)7-CH=CH-(CH2)7-C00H ™ i > CH3-(CH2) 7-CH0H-CHCl-(CH2)7-C00H (25)
9,11 or 8 , 1 0 - d i h y d r o x y m e t h y l o l e a t e , 9 - or 10-keto methyl s t e a r a t e , hydroxyl methyl o l e a t e and dihydroxyl methyl s t e a r a t e were i d e n t i f i e d as minor s i d e p r o d u c t s .
The c h l o r i n a t i o n p r o d u c t s of h e x a d e c - 9 - e n o i c a c i d and o c t a d e c - 9 , 1 2 - d i e n o i c a c i d were s t u d i e d by Gibson e t a l . [ 6 8 ] u s i n g p o s i t i v e and n e g a t i v e ion FAB-MS with a c c u r a t e mass measurements on the e x t r a c t e d r e a c t i o n p r o d u c t s . D e r i v a t i z a t i o n with diazomethane or o t h e r methylating r e a g e n t s was omitted t o minimize the formation of a r t e f a c t s . They were able t o d e t e c t the production of the c h l o r o h y d r i n d e r i v a t i v e of hexadec-9-enoic a c i d and t h e d i c h l o r o h y d r i n d e r i v a t i v e of o c t a d e c - 9 , 1 2 - d i e n o i c a c i d . The l a s t d e r i v a t i v e could not be analysed by GC but was r e a d i l y d e t e c t a b l e by FAB-MS.
2.7 Literature Cited.
1 . Morris, J.C. In "Water Chlorination: Environmental Impact and Health Effects"; Jolley, R.L., Ed.; Ann Arbor Science: Ann Arbor, MI, 1978; Vol. 1, pp 27-35.
2. Rosenblatt, D.H. In "Disinfection Water and Wastewater"; Johnson, J.D., Ed.; Ann Arbor Science: Ann Arbor, MI, 1975, pp 249-276.
3. Jolley, R.L.; Carpenter, J.H. In "Water Chlorination: Environmental Impact and Health Effects"; Jolley, R.L., et al., Eds.; Ann Arbor Science: Ann Arbor, MI, 1983; Vol. 4, pp 3-47.
4. Faust, S.D.; Aly, O.A. "Chemistry of Water Treatment"; Butterworth: Woburn, MA, 1983, p 690.
5. Rook, J.J. Water Treat. Exam. 1974, 23, 234-243.
6. Stevenson, F.J. In "Humic Substances in Soil, Sediment, and Water"; Aiken, G.R., et al., Eds.; John Wiley & Sons, NY, 1985; pp 13"52.
7. Oliver, B.C. Can. Res. J. 1978, V1_> 21-22.
8. Rook, J.J. Environ. Sci. Technol. 1977, 1_U 478-482.
9. Coleman, W.E.; Munch,' J.W.; Kaylor, W.H.; Streicher, R.P.; Ringhand, H.P.; Meier, J.P. Environ. Sci. Technol. 1984, JJ3, 674-681.
10. Kringstad, K.P. ;' Ljungquist, P.O.; De Sousa, F. ; Strömberg; L.M. Environ. Sci. Technol. 1983, VT, 553-555.
11. Havlicek, S.C.; Reuter, J.H. ; Ingols, R.S.; Lupton, J.D. ; Ghosal, M.; Rails, J.W.; El-Barbary, I.; Strattan, L.W.; Cotruvo, J.H.; Trichilo, C. Prepr. Pap. Natl. Meet. -Am. Chem. Soc. Div. Environ. Chem. 1979, 19. 12. Trehy, M.L.; Bieber, T.I. In "Advances in the Identification and
Analysis of Organic Pollutants in Water"; Keith, L.H., Ed.; Ann Arbor Science: Ann Arbor, MI, 1981; Vol. 2, pp 941-975.
13. Merlet, N.; Thibaud, H.; Dore, M. Sci. Tot. Environ. 1985, 47, 223-228. 14. Christman, R.F.; Johnson, J.D.; Pfaender, F.K.; Norwood, D.L. ; Webb,
M.R.; Hass, J.R.; Bobenrieth, M.J. In "Water Chlorination: Environmental Impact and Health Effects"; Jolley, R.L., et al., Eds.; Ann Arbor Science, Ann Arbor, MI, 1980; Vol. 3, PP 75-83.
15. Johnson, J.D.; Christman, R.F.; Norwood, D.L.; Millington, D.S. Environ. Health Perspect. 1982, 46, 63~71 .
16. Norwood, D.L.; Johnson, J.D. ; Christman, R.F.; Millington, D.S. In "Water Chlorination: Environmental Impact and Health Effects"; Jolley, R.L., et al., Eds.; Ann Arbor Science, Ann Arbor, MI, 1983; Vol. 4, pp 191-200.
17. Christman, R.F.; Norwood, D.L.; Millington, D.S.; Johnson, J.D. Environ. Sci. Technol. 1983, J_7, 625-628.
18. Seeger, D.R.; Moore, L.A.; Stevens, A.A. In "Water Chlorination: Chemistry, Environmental Impact and Health Effects"; Jolley, R.L., et al., Eds.; Lewis Publishers, Chelsea, MI, 1985, Vol. 5, pp 859-873. 19. Quimby, B.D.; Delaney, M.F.; Uden, P.C.; Barnes, R.M. Anal. Chem. 1980,
52, 259-263.
20. Miller, J.W.; Uden, P.C.; Barnes, R.M. Anal. Chem. 1982, 54, 485-488. 21. Uden, P.C.; Miller, J.W. J. Am. Water Works Assoc. 1983, 75_, 524-527. 22. Lahl, U.; Stachel, B.; Schröer, W.; Zeschmar, B.; Z. Wasser-
Abwasser-Forsch. 1984, V7> ^5-49.
23. Norwood, D.L.; Thompson, G.P.; Johnson, J.D.; Christman, R.F. In "Water Chlorination: Chemistry, Environmental Impact and Health Effects"; Jolley, R.L., et al., Eds.; Lewis Publishers, Chelsea, MI, 1985, Vol. 5, pp 1115-1122.
24. Norwood, D.L.; Christman, R.F.; Johnson, J.D.; Hass, J.R. J. Am. Water Works Assoc. 1986, 78, 175-180.
25. Adler, E. Wood Sci. Technol. 1977, V U 169-218.
26. Kringstad, K.P.; Lindström, K. Environ. Sci. Technol. 1984, _ljj, 236A-247A.
28. 29. 30. 31. 32. 33. 31. 35. 36. 37. 38. 39. 10. KI. 12. 13. 11. 15. 16. 17. 18. 19. 50. 51. 52. 53. 51. 55. 56. 57. 58. 59. Voss, R.H Holmbom, 172-171. Holmbom, Technol.
Environ. Sci. Technol. 1983, J_7, 530-537.
B.R.; Voss, R.H.; Mortimer, R.D.; Wong, A. Tappl, 1981, 61, Voss, R.H.; Mortimer, R.D.; Wong, A. Environ. Sci. B.R.; Voss, R.H
1981, 18, 333-337.
Holmbom, B.R., 1987, Oak Ridge Kronberg, L., presented 1987, Oak Ridge.Lindström, K.; Osterberg, F. Environ. Sci
Lindström, K.; Nordin, J. J. Chromatogr. 1976,128, 13-26
presented at the 6th Water Chlorination Conference, May at the 6th Water Chlorination Conference, May
Technol. 1986, 20, 133-138. 26.
Chromatogr. 1978, 161-169. Eklund, G.; Josefsson, B
Voss, R.; Wearing, J.T
Analysis of Organic Pollutants in Water"; Keith, L.H Björseth, A. J_.
Wong, A. In "Advances in the Identification and Ed.; Ann Arbor Science: Ann Arbor, MI, 1981, Vol. 2, pp 1059-1095.
Mallevialle, J.; Bruchet A.; Schmitt E. Proc. AWWA Water Quality Technol. Conf. 1983, _n_, 83-96. Environment Int'1. Ram, N.M.; Morris J.C Trehy, M.L.; Yost, 1117-1122. Cloirec, C. Le; Environmental Impact 1980, jl, 397-105. R.A.; Miles, C.J. Environ. Sci. Technol, Martin, G. and Health In Water Chlorination. 1986, 20, Chemistry, Effects;
Lewis Publishers: Chelsea, MI, 1985; Vol. 5 Langheid, K. Chem. Ber. 1909, _12, 2360-2371
1916, 10, Jolley, R. pp 821-831. L. et al. Eds. ; 319-323. 79-95. 521-532. 1661-1667. Abdel-Fattah, S.H. Chem. Zvesti 1971,
Y; Biochem. . Biochem. J . Biochem. J
<L_ 1917, 11,
1926, 1936, 20, 30, 25. Bacon, V.A 222-230. ,; Duffield, A.M. Environ. Sci. Technol. 1980, Dakin, H.D. Biochem. JDakin, H.D. Wright, N.C Wright, N.C Kantouch, A
Pereira, W.E.; Hoyanu, Y; Summons, R.E Biochim. Biophys. Acta 1973, 211< 170-180. Burleson, J.L.; Peyton, G.R.; Glaze, W.H 1Ü> 1351-1359.
Trehy, M.L.; Bieber, T.I. In Advances in the Identification and Analysis of Organic Pollutants in Water; Keith, L.H., Ed.; Ann Arbor Science: Ann Arbor, MI, 1981; Vol. 2, pp I33-I52.
Bieber, T.I.; Trehy, M.L. In Water Chlorination. Environmental Impact and Health Effects; Jolley, R.L. et al., Eds.; Ann Arbor Science: Ann Arbor, MI, 1983; Vol. 1, pp 85-96.
Carrell Morris, J.; Baum, B. In Water Chlorination. Environmental Impact and Health Effects; Jolley, R.L. et al., Eds.; Ann Arbor Science: Ann Arbor, MI, 1978; Vol. 2, pp 29-18.
Fielding, M.; Horth, H. Wat. Supply 1986, _1, 103-126.
Horth, H. Presented at the 6th Water Chlorination Conference, Oak Ridge, May 1987.
Rydon, H.N.; Smith, P.W.G. Nature 1952, 169, Matsushima, A.; Yamazaki, S.; Shibata, K. Acta 1972, 271, 213-251.
Stelmaszynska, T.; Zgliczynski, J.M. Eur. J. Biochem. Heltz, G.R.; Dotson, D.A.; Sigleo, A.C. In
Environmental Impact and Health Effects; Jolley, R.L. et al., Eds.; Ann Arbor Science: Ann Arbor, MI, 1983; Vol. 1, pp 181-189.
Scully, F.E.; Kravitz, R.; Howell, G.D.; Speed, M.A.; Arber, R.P. In Water Chlorination. Chemistry, Environmental Impact and Health Effects; Jolley, R.L. et al., Eds.; Lewis Publishers: Chelsea, MI, 1985; Vol. 5, pp 807-820.
Green, J.W. In "The Carbohydrates: Chemistry and Biochemistry"; Pigman, W.; Horton, D., Eds.; Academic Press: N.Y., 1980, pp 1101-1166.
922-923.
Inada, Y. Biochim. Biophys. _ 1978, 92, 301-308
60. Guilbot, A.; Mercler, C. In "The Polysaccharides", Aspinall, G.O., Ed.; Academic Press: N.Ï., 1985; Vol. 3, pp 210-282.
61. Kiliani, H. Justus Liebigs Ann. 1880, 205, 115-190. 62. Barth, L. Justus Liebigs Ann. 1862, _12J, 341.
63. Crane, A.M.; Kovacic, P.; Kovacic, E.D. Environ. Sci. Technol. 1980, J_4> 1371-1374.
64. Larson, R.A. ; Rockwell, A.L. Environ. Sci. Technol. 1979, V3, 325-329.
65. Lin, D.C.K.; Millon, R.G.; Kopfler, F.G.; Lucas, S.V. In "Advances in the Identification and Analysis of Organic Pollutants in Water"; Keith, L.H., Ed.; Ann Arbor Science: Ann Arbor, 1981; Vol. 2, pp 861-906. 66. Noordsij, A.; Puyker, L.M.; Gaag, M.A. van der Sci. Tot. Environ. 1985,
47, 273-292.
67. Ishiwatari, R. In "Humic Substances in Soil, Sediment, and Water"; Aiken, G.R. et al., Eds.; John Wiley & Sons, New York, 1985; pp 147-180. 68. Gibson, T.M.; Haley, J. ; Righton, M.; Watts, C D . Environ. Technol.
Lett. 1986, 7, 365-372.
69. Ghanbari, H.A.; Wheeler, W.B.; Kirk, J.R. In "Water Chlorlnation: Environmental Impact and Health Effects"; Jolley, R.L., et al., Eds.; Ann Arbor Science: Ann Arbor, MI, 1983; Vol. 4, pp 167-177.
70. Ghanbari, H.A.; Wheeler, W.B. ; Kirk, J.R. J. Food Science 1981, 47., 482-485.
3. THE IDENTIFICATION OF ARYL-CHLORINATED
AROMATIC ACIDS AND INTERMEDIATES LEADING TO
CHLOROFORM AND C-4 DIACIDS IN THE
CHLORINATION OF TERRESTRIAL HUMIC ACID
3.1 SummaryThe c h l o r i n a t i o n of t e r r e s t r i a l humic a c i d was s t u d i e d a t pH 7.2 with d i f f e r e n t c h l o r i n e t o carbon r a t i o s . The p r i n c i p a l p r o d u c t s a r e chloroform, d i - and t r i c h l o r o a c e t i c a c i d , and c h l o r i n a t e d C-M d i a c i d s .
With a high c h l o r i n e dose many new c h l o r i n a t i o n products were d e t e c t e d , among them c h l o r i n a t e d a r o m a t i c a c i d s . With a low c h l o r i n e dose a c l a s s of c h l o r i n a t i o n products was found, which c o n t a i n e d a t r i c h l o r o m e t h y l group. These compounds may be converted t o chloroform and in most cases C_1t d i a c i d s by o x i d a t i o n and h y d r o l y s i s r e a c t i o n s . Because t h e s e compounds are found mainly a t low c h l o r i n e dosage, t h e y may be r e g a r d e d a s i n t e r m e d i a t e s in the r e a c t i o n s t h a t give chloroform. A r e a c t i o n scheme i s proposed t h a t explains the formation of the i n t e r m e d i a t e s .
The i n t e r m e d i a t e s s u p p o r t the h y p o t h e s i s of Rook t h a t 1,3-dihydroxybenzene m o i e t i e s in humic a c i d a r e r e s p o n s i b l e for t h e formation of chloroform. However, attemps t o demonstrate t h e presence of t h e s e s t r u c t u r e s in humic acid by means of Curie p o i n t p y r o l y s i s / g a s chromatography/mass spectrometry and n u c l e a r magnetic resonance before and a f t e r the c h l o r i n a t i o n r e a c t i o n , f a i l e d .
The m a t e r i a l of t h i s c h a p t e r was published a s :
I d e n t i f i c a t i o n of i n t e r m e d i a t e s l e a d i n g t o chloroform and C-H d i a c i d s in t h e c h l o r i n a t i o n of humic a c i d .
E.W.B, de Leer, J . S . Sinninghe Damsté, C. E r k e l e n s , and L. de Galan, Environ. S c i . Technol. j_9, 512 - 522 (1985)
and
Formation of a r y l - c h l o r i n a t e d aromatic a c i d s and p r e c u r s o r s for chloroform in c h l o r i n a t i o n of humic a c i d .
E.W.B. de Leer, J . S . Sinninghe Damsté, and L. de Galan,
in "Water C h l o r i n a t i o n , Chemistry, Environmental Impact and Health E f f e c t s " , R.L. J o l l e y , R . J . B u l l , W.P. Davis, S. Katz, M.H. R o b e r t s , and V.A. Jacobs, Eds.; Lewis P u b l i s h e r s , I n c . : Chelsea, MI, 1985; Vol. 5, pp 843 - 857.
3.2 Introduction
In 1971 Rook [1] described that superchlorination of water from the rivers Rhine and Meuse produced trihalomethanes as undesirable side products. Beacause a good correlation was found between the chloroform formation and the color intensity of the water, he suggested that humic substances are the precursors for the. trihalomethanes. This hypothesis was supported by the observation that an aqueous extract of peat gave the four trihalomethanes CHC13, CHBrCl2, CHBr2Cl, and CHBr3 upon chlorination in the presence of bromide ions. Since then, the presence of trihalomethanes has been demonstrated in many drinking waters [2,3], and generally, the reaction between chlorine and humic material is regarded as the main source for these products [1].
Detailed investigations of these reactions between chlorine and humic material have clearly established that chloroform is the major volatile chlorination product but that a large number of other halogenated and nonhalogenated products are also formed. The formation of volatile chlorination products like chloral and chlorinated acetones [5], 2-chloropropenal [6], and chlorinated isoprenoid alcohols [7] was demonstrated by gas chromatography/mass spectrometry (GC/MS). However, total organic halogen formed in the chlorination of water or solutions of humic materials is much greater than can be accounted for by the amount of volatile products [8,9]. Many nonvolatile products can be converted into volatile products by methylation with diazomethane, which makes them amenable to analysis by GC/MS or other special techniques.
Quimby et al. [10] found by gas chromatography with microwave emission detection that trichloroacetic acid was a major product and identified several chlorinated acids and phenols on the basis of their retention times. Later, Uden and Miller [11,12] and Christman et al. [13] showed that trichloroacetic acid is formed in a molar yield comparable to that of chloroform. More systematic studies, aimed at the identification of a large number of nonvolatile products, were conducted by Christman and co-workers [13-15]. Over 100 products were identified and many structures were assigned by GC/MS. Di- and trichloroacetic acid and 2,2-dichlorobutanedioic acid were the main products, which, together with chloroform, accounted for 53$ of the total organic halogen. Other chlorinated products included 2,2-dichloropropanoic acid, 2-chlorobutanedioic acid, 2-chlorobutenedioic acid, 2,3-dichlorobutenediolc acid, dichloropropanedioic acid, and various other less abundant compounds.
No c h l o r i n a t e d a r o m a t i c s were found. Most of t h e n o n c h l o r i n a t e d products are a l i p h a t i c and a r o m a t i c c a r b o x y l i c a c i d s , demonstrating t h a t c h l o r i n e acted not only through s u b s t i t u t i o n and a d d i t i o n but a l s o through o x i d a t i o n r e a c t i o n s .
To e s t a b l i s h a r e a c t i o n pathway for t h e production of chloroform and the c h l o r i n a t e d a c i d s , knowledge of the s t r u c t u r e of humic m a t e r i a l i s n e c e s s a r y . Humic m a t e r i a l s a r e geopolymers formed from l i g n i n , c a r b o h y d r a t e s , p r o t e i n s and f a t t y a c i d s by m i c r o b i o l o g i c a l d e g r a d a t i o n s and enzymatic or a u t o o x i d a t i v e coupling r e a c t i o n s [ 1 6 ] . Although humic m a t e r i a l s obviously a r e not w e l l - d e f i n e d o r g a n i c compounds, s e v e r a l s t r u c t u r e s [17-20] have been proposed, which c o n t a i n fragments t h a t may be converted i n t o chloroform by c h l o r i n e i n aqueous medium at pH 7 - 8 . 1, 3"Dihydroxybenzenes [ 1 , 5 , 2 1 ] , 1 , 3 - d i k e t o compounds [ 2 2 ] , n a t u r a l a c i d s l i k e c i t r i c a c i d [ 2 3 ] , and compounds with a c t i v a t e d C-H bonds l i k e i n d o l e s [24] were shown t o give chloroform i n high y i e l d on c h l o r i n a t i o n in aqueous medium. Of t h e s e , 1,3dihydroxybenzenes seem t o be t h e more l i k e l y c a n d i d a t e s because 3 , 5 -dihydroxybenzoic a c i d i s formed i n the d e g r a d a t i o n of humic m a t e r i a l with CuS0.,-Na0H a t 175-180 °C [ 2 0 ] . From t h e work of Cheshire et a l . [ 2 5 ] i t a p p e a r s , however, t h a t the products of KOH fusion may be of no d i a g n o s t i c value f o r the s t r u c t u r e of humic s u b s t a n c e s , and in r e c e n t KMnO,, degradation s t u d i e s of humic and f u l v i c a c i d s [ 2 6 , 2 7 ] no 1,3_dihydroxybenzene s t r u c t u r e s were d e t e c t e d , p o s s i b l y a s a r e s u l t of complete o x i d a t i o n of these s t r u c t u r e s [ 2 8 ] .
Although t h e p o s s i b i l i t y of 1,3-dihydroxybenzene s t r u c t u r e s as the p r e c u r s o r fragment for chloroform formation from humic m a t e r i a l remains to be proven, Rook [ 5 , 2 1 ] proposed a mechanism based on t h e chemistry of the r e a c t i o n between c h l o r i n e and r e s o r c i n o l . For a b e t t e r u n d e r s t a n d i n g of t h i s mechanism and for the i d e n t i f i c a t i o n of the s t r u c t u r a l fragments in humic m a t e r i a l t h a t a r e c o n v e r t e d i n t o chloroform and c h l o r i n a t e d a c i d s , the i d e n t i f i c a t i o n of i n t e r m e d i a t e s i s necessary [ 2 9 ] .
3.3 Experimental S e c t i o n
S e p a r a t i o n of Humic Acid. Humic a c i d (HA) was i s o l a t e d from peat ( L i e s s e l s e P e e l , 0 - B r a b a n t ) following the procedure d e s c r i b e d by Stevenson [ 3 0 ] . This i n v o l v e s t r e a t m e n t with 0.1 M HC1, e x t r a c t i o n with 0.5 M NaOH, removal of r e s i d u a l s o l i d s , a c i d i f i c a t i o n t o pH 1 with p r e c i p i t a t i o n of humic a c i d , p u r i f i c a t i o n by r e d i s s o l u t i o n / p r e c i p i t a t i o n , washing with deionized w a t e r , and f r e e z e - d r y i n g . To minimize chemical changes caused by o x i d a t i o n , a l l s t e p s ( i f p o s s i b l e ) were c a r r i e d out in an atmosphere of n i t r o g e n .
The elementary composition of the f i n a l humic a c i d was t h e following: C 5 0 . 7 Ï ; H,5.1%; N . 1 . 5 Ï ; 0 , 3 9 . 1 $ ; a s h , 1 . 5 $ .
