Volatile organochlorine compounds formed in the bleaching of pulp with ClO2

Pergamon PIh S0045-6535(96)00208-1

Chemosphere, Vol. 33, No. 3, pp. 437-448, 1996 Copyright © 1996 ElsevierScienceLtd Printed in Great Britain. All rights reserved 0045-6535/96 $1500+0.00

V O L A T I L E ORGANOCHLORINE COMPOUNDS F O R M E D IN THE BLEACHING OF PULP W I T H CIO 2

Soile Juuti a*, Terttu Vartiainen b, Pekka Joutsenojac and Juhani Ruuskanen a aDepartment of Environmental Sciences, University of Kuopio, P.O.Box 1627, FIN-70211 Kuopio, Finland bDepartment of Environmental Hygiene, National Public Health Institute, P.O.Box 95 FIN-70701 Kuopio, Finland COy AEM Ltd, P.O.Box 1750, FIN-70211 Kuopio, Finland

(Receivedin Germany 16 April 1996; accepted 14 May 1996)

ABSTRACT

Volatile organochlorine compounds (VOCCs) formed during kraft pulp bleaching were determined from the bleaching effluent at the bleach plants and from waste water at the waste water treatment plants of three pulp mills means by of a purge and trap injector connected to a GC/MS. Among the seventeen VOCCs identified when C10 2 was used in pulp bleaching, chloroform constituted the major fraction and dichloroaeetic acid methyl ester and 2,5-dichlorothiophene were also abundant. The formation of VOCCs was related to the use of C102 in bleaching, with a lower C10z charge yielding less VOCCs and hardly any being formed when non-chlorinated bleaching agents were used. Copyright © 1996 Elsevier Science Ltd

Key words: bleaching effluent, chloroform, kraft pulp, volatile organic compounds, waste water

I INTRODUCTION

A variety of organic chlorinated compounds are formed during the bleaching of kraft pulp with agents containing chlorine. Much attention has been focused on the occurrence of these substances in effluents and their aquatic toxicity (e.g. 1, 2), but much less interest has been showed in the compounds volatilized into the atmosphere. When gaseous C12 is used in bleaching, considerable amounts of organochlorine compounds of high molecular mass are formed. These are lipophilic and presist in the environment. About 30 % of the organically bound chlorine in spent chlorination water and about 5 % in spent alkali water are of low relative molecular mass

437

438 (Mr < 1000) (3). Gaseous CI2 has largely been replaced by CIO2 in bleaching in recent years and this has reduced the formation of lipophilic organochlorine compounds considerably (3-5). Also the formation of volatile low molecular chlorinated compounds has been shown to be decreased (6). Less than 0.15 % of the organically bound chlorine in the effluents was present as low molecular mass material (7). Environmental demands has led to the introduction of several non-chlorinated bleaching methods, which will further reduce the formation of organochlo.rine compounds in pulp bleaching to a great extent. Interestingly, the ecotoxicological effects observed in the recipient water bodies have not been found to decrease after the replacement of CIO2 in bleaching by nonchlorinated bleaching methods (8). Only few data exist on the volatile organochlorine compounds (VOCCs) that form and evaporate during the bleaching of pulp and the subsequent treatment of the waste water, especially when C102 is used in bleaching, Even though the fraction of the material susceptible to volatilization formed during C102 bleaching is low, individual VOC-~s may have notable environmental implications. As VOCCs drift into waste water treatment plants with the bleadhing effluent, most of these compounds obviously evaporate in aerated basins and are transferred from a water facies to an air facies. VOCCs volatilized from bleaching processes are transported into the immediate environment, but they may also contribute to the long-range transport of organic compounds (e.g. 9). The purpose ,Jf this work was to characterize the VOCCs emitted from the bleaching effluents of kraft pulp at three mills where 12102 was used for bleaching (ECF, elemental chlorine-free bleaching), and to study the fate of these compounds at waste water treatment plants. The formation of VOCCs was compared with that occurring when a non-chlorinated bleaching method (TCF, total chlorine-free bleaching) was used in one pulp mill. Qualitative analyses were performed with a purge and trap injector, which minimizes losses of volatile compounds during the procedure.

2 METHODS

2.1 Chemicals The chemicals were obtained as follows: Chlorobenzene from Fluka (Switzerland), chloroform from Merck (Germany), 1,2-dichluropropane and 2,5-dichlomthiophene from Aldrich (USA), and dichloroacetonitrile from ICN, K & K Laboratories (USA). Monochloroacctic and dichloroacetic acids (Fluka, Switzerland) were treated with diazomethane to obtain their derivative methyl esters. Diazomethane was prepared from nitrosomethylurea synthetised a s in (10) according to Fieser and Fieser (11). Chloroacetones were synthesized by the reaction of hexacldoroacetone with hydrogen in the presence of a metallic palladium catalyst on an activated carbon carrier [Brit. pat. 1,140,434 (22 Jan. awarded to Wyandotte Chemical Corp.)l The hydrogenation was performed at atmospheric pressure and room temperature, typically for 24 hours. The crude product was distilled under reduced pressure. All other chemicals were research grade commercial materials. 2.2 Sample collection Water samples were taken from three kraft pulp mills during processing of hardwood (birch) and softwood (pine, spruce) ECF bleached pulp, i.e. when CIO2 was being used for bleaching. The bleaching sequences included oxygen treatment before the first chlorine dioxide treatn~nt (Do) followed by treatment with alkali (Ep = alkali

439 with hydrogen peroxide, EOP = alkali with hydrogen peroxide and oxygen, Eo = alkali with oxygen), a second chlorine dioxide stage (D1) and a second alkali (E2) or a third chlorine dioxide (12)2) stage (Table 1). Samples were taken from the acid and alkaline filtratesand in two cases from the combined sewer of the bleach plant.

The waste water t~'eatment plants of mills 1 and 2 were sampled at their intake prior to the addition of any chemicals and at the effluent stage after the secondary clarifiers. At the mill 3 samples were taken at the beginning and at the end (= input to treatment) of an open ditch 200-250 m long and 4 m wide, which can-led all the waste water from the mill to the treatment plant Samples from the effluent were taken after the secondary clarifiers, but also after an ecological basin with a hydraulic retention time of 80 hours. Each mill had an activated sludge waste water treatment plant with aeration basins in operation at the lime of sampling. Mill 3 was also sampled during the production of TCF-bleached hardwood pulp by a complex treatment (Q) followed by three peroxide (P) bleaching stages (Table 1). Samples were taken after the fast two bleaching stages. No samples were taken from the waste water treatment plant, as the bleaching effluent from TCF bleaching was combined with the water from the ECF softwood bleach line.

Table 1. Process parameters related to the samples collected in three kraft pulp mills (HW = hardwood, SW = softwood). Mill I Bleach sequence

Mill 2

Do-Ep-DI-E2-D2

Mill 3

Do-EOP-DI -D2

i

Do-Eo-DI-D2

Mill 3

i i Q-P-P-P

SW

HW

SW

HW

SW

iHW

Production of bleached pulp (tons/day)

1190

925

1250

550

380

760

i

835

002 usage as active CIz (kg/ton pulp)

34.3

50.9

33.4

45.0

59.4

48.4

i

0

Total flow of waste water (m3/day): Im2uent. ~fme primmy claril'~rs Effluent, after secondary cla~qers

47350

39660

83800

80000

62000a

47350

39660

83800

80000

52260a

i

b

Furnish

HW

i

b

b HW and SW bleaching effluents combined TO~/HW and ECF/SWbleaching effluents combined; thereforenot reported

Due to the long hydraulic retention times at the treatment plant (one day at mills 1 and 2; 2.5 days at mill 3), the influent and effluent samples do not represent exactly the same load of waste water. As there were no major changes in the bleaching process during sampling, the samples are assumed to be comparable. Three consecutive samples were taken into 30 ml vials with Teflon-sealed stoppers every three to four hours. Each vial was rinsed with the sample water, and sodiumthiosulphate (0.8 mI/l) was added before the sample was taken. The sample water was poured carefully into the vials, avoiding bubbling and leaving no head-space. The vials were immediately placed into crushed ice and kept there until transported to the laboratory. The samples were stored in the Cold (< +6 °LD and analyzed within the next two days. They were not filtered before analysis in order to avoid evaporation of compounds during fdlration.

440 2.3 Sample analysis Volatile organic compounds were analyzed with a purge and trap injector (Chrompack) connected to a gas chromatograph-mass spectrometer (Hewlett Packard 5890, 5971). Seven millilitres of the three replicate samples were pooled for analysis, i.e. the total sample volume was 21 mL In addition, some of the samples were analyzed by purging the compounds from two consecutive 21 ml samples into the same cold trap in order to confirm the findings. The mass spectrometer was operated in the electron impact mode (70 eV). The temperature of the cold trap was -120 °C before the purging started. Each sample was purged (flow rate 100 ml/min) with helium gas (99.996 %, AGA) for 10 minutes, after which the temperature of the cold trap was raised to 200 °C for 2 rain allowing the sample compounds to evaporate into an analytical column of DB-VRX (30 m x 0.25 mm I.D., f'dm 1.4 I~m). The oven temperature was initially 40 °C for 8 rain and it was programmed to rise by 10 °C rain"1 to 200 °C, where it remained for 3 rain, and again to 240 °C for 5 rain. Mass fragments of m/z 35-335 were monitored. The compounds were identified by comparing the background-corrected spectrum at the chromatographic peak maximum with spectra in the NBS library database. Nine VOCCs (see Tables 2-4) were verified by means of reference compounds. Milli-Q water was used to demonstrate the purity of the analytical system.

3 RESULTS

Chloroform accounted for by far the largest proportion of the VOCCs in most samples from the bleach plant and waste water treatment plant (Tables 2 - 4) and constituted about 98 % (range 30 - 100 %) of the total VOCCs in the samples. Other typical VOCCs with high abundances were dichloroacetic acid methyl ester and 2,5-dichlorothiophene, as seen in Fig. 1, although dichloroacetonitrile and 1,l-dichlomacetone were also commonly present.

~ c e

......

A

lsoooo

20000 r~-.,

6.3o

I T

L '

B i.~o "

~o[oo';2!o;i~ioo';~:ooA!o~

io[o;i2!o;'

i~io;'

Figure I. Total ion GC/MS chromatogram of the first acid filtrate (Do) sample taken from the hardwood bleach line at mill 3. The numbers refer to the VOCCs listed in the Table 4. The letters represent the unidentified compounds with a chlorine isotope cluster pattern.

441 M///I The abundances of VOCCs at mill 1 were markedly higher during the processing of softwood pulp than of hardwood pulp (Table 2) obviously in response to the higher consumption of active chlorine (Table 1). The most abundant compound in all the samples was chloroform, which was the only compound detected in the alkaline Filtrates, High pH (about 10 in these alkaline fdtrate samples) effectively destroys reactive compounds. When a doubled sample volume was used in the analyses of samples from the acid filtrates of the softwood bleach line, the abundances of all the compounds increased and 1,2,3,4,5,5-hexachloro-l,3-cyclopentadiene was identified at the Do-stage and chioroacetic acid methyl ester at the Dl-stage. The waste water treatment plant and bleach plant exhibited the same VOCCs, but the abundances of the compounds were lower in the waste water treatment plant, as the bleaching effluent is diluted with other waste water. Most of the compounds were removed effectively in the treatment plant.

M///2 The bleaching effluent and waste water from mill 2 contained considerably fewer compounds than that of the other mills (Table 3). This is partly because of high flows normalized to production at the waste water treatment plant (especially during softwood pulp processing), which obviously have diluted the compounds considerably (Table 1). Furthermore, the low amounts of compounds detected during hardwood pulp bleaching may obviously be explained by the low total active chlorine usage. The absence of volatile compounds at the Dl-stage was apparently due to the high pH (> 10), caused by alkaline treatment of the bleach water before it was led to the wash filtrate. Analyses with doubled amounts of the f'wst acid filtrate samples from the hardwood pulp bleach line revealed the presence of 1,2-dichloropropane and dichloroacetonitrile.

M///3 Most of the compounds identified during ECF bleaching at mill 3 were the same as at mill 1 (Table 4) and no distinct differences in the formation of VOCCs existed between the two bleach lines. It should be noted, however, that contrary to the other mills studied, the two pulp species were bleached in different bleach facilities at mill 3, and thus the results do not indicate directly the differences due to pulp species. 2-Chlorothiophene appeared simultaneously with dichloroacetic acid methyl ester in the chromatogram for the acid filtrate samples and the samples from the beginning of the influent ditch. By the end of the ditch, however, dichloroacetic acid methyl ester was no longer present, obviously due to hydrolysis. 2-Chlorothiophene was the only compound with chloroform noted in the alkaline filtrates, whereas 3-chlorothiophene was also present in the acid filtrate samples and at the beginning of the ditch.

Differentiation between these two

substituents was based on the difference on their boiling points (12), since their mass spectra are almost identical. The waste water contained effluents from both hardwood and softwood pulp bleaching, because of the simultaneous productions of the two species. Some of the compounds (dichloroacetonitrile, dichlomacetic acid methyl ester and 3-chlorothiophene) disappeared during the passage through the open ditch (Table 4). Many of the VOCCs were close to their detection limit at the waste water treatment plant, which may explain the slight

442 inconsistencies in the results (see Table 4: e.g, 1,2-dichloropropane and chlorobenzene). Chlomforr& 2chlorothiophene and 2,5-dichlorothiophene were the most distinctly present in the effluent after activated sludge lxeatment. T h e ecological basin effectively destxoyed all the compounds, however, a n d only traces of chloroform were present in the water discharging into the lake. Few peaks appeared in the c h r o m a t o g r a m s for the bleach plant samples taken during T C F bleaching. The only chlorinated c o m p o u n d detected was 2,5-dichlorothiophene, which appeared in trace a m o u n t s at the first peroxide stage. M i n o r occurrences o f organochlorine c o m p o u n d s can be expected in T C F bleach water, however, since wood contains small a m o u n t s o f chlorine naturally. Table 2. A b u n d a n c e s o f the identified volatile organochlorine c o m p o u n d s in the order o f appearance in the c h r o m a t o g r a m s of bleaching effluent and waste water in mill 1 during processing o f hardwood and softwood pulp. 0 D = identification method, Do a n d D1 = acid f'dtrateS, Ep = alkaline fdtrate, I N F = influent to waste water treatment plant, EFF = effluent from waste water lxeatment plant). HARDWOOD*

ID

DO

Ep

D1

Chloroform

Sc

***d

,

Dichloroacetonitrile

S

*

1,I -Dichlomacetone

S

*

MS

**

Dichiotcecetic acid methyl ester

S

***

2,5-Dichlomthiophene

S

e

ID

DO

Ep

D1

Chloroform

S

***

***

*** ~ ***

1,2-Dichloropropane

S

Compound

Trichloronitromethane

i INF b I ]I

*** [ *** **

*

EFF

***

[

i ' i ' l

[ i

SOFTWOOD

*** [!

Compound

: k i INi~ I I i

EFF

***

I

*

[ t

Bromodichlommethane

MS

**

**

Dichloroncetonitrile

S

***

*

1,1-Dichloroa~tone

S

***

*

Chloroacetic acid methyl ester

S

0

Trichloronitmmethane

MS

***

**

Dichloroaceflc acid methyl estex

S

***

***

1,l, 1,-Trichlomacetone

S

*

Chlorobenzene

S

*

3-Chlomthiophene 2,5-Dichlorothiophene 2-Chloroethenylbenzene

MS S MS

0

I I

* *

**

~ ** I ~ ** I ~ *** I ~ 0 I [ I

***

I [ I I

*** t

b Single samples Before the secondmy claxifiets d S = identification cc~mned by standard compoumds, MS = identification based on librat7 mass spectra Peak *tess in chromaWlp-mns:*** > 10x fOe, *** > l x 10e, ** > 0.5 x I06, * > 0.l x lOS, 0 < 0.I x 10e, - ffi not detected '~ A high interfering peak appeared simultaneously

443 Table 3. A b u n d a n c e s o f the identified volatile organocldorine c o m p o u n d s in bleaching effluent and waste water in mill 2 during p r o c e s s i n g o f h a r d w o o d and s o f t w o o d pulp. ( E O P = alkaline filtrate, Cs = c o m b i n e d s e w e r o f the

bleach plant Other marks as in Table 2). ID

Do

FOP

DI

! C.s ; INF I

EFF

Chloroform

S

***

***

***

I *** ~ ***

***

l,l-Dichloroacetone

S

**

Dichloroacefic avid methyl ester

S

***

S

***

HARDWOOD Compound

12`5-Dichlorothiopbeue SOFTWOODS

]

t I i

ID

Do

EOP

DI

Chloroform

S

***

*

Dichioroavetonitrile

S

0

]

Dichloroavetic avid methyl este2,

S

*

t

2,5-Dichlorothiophene

S

**

Compound

! INF I

* EFF

I *** ~ ***

*

!

Table 4. A b u n d a n c e s of the identified volatile organochlorine c o m p o u n d s in bleaching effluent and w a s t e water in mill 3 during p r o c e s s i n g of h a r d w o o d ( H W ) and s o f t w o o d ( S W ) pulp. N u m b e r s in front of the c o m p o u n d s refer to the c h r o m a t o g r a r n in Fig. 1. (Eo = alkaline filtrate). ID

Do

~

Cs

Do

Eo i nvF'

HW

HW

HW

SW

SW ]

***

***

***

mP

emv~ E ~

!

Compound 1. Chloroform 2. 1-Chloro-2-methyl- 1-propene 3. 1,2-Dichioropmpane 4. Bromodichloromethane 5. Dichloroavetonitrile 3-Chloro-2-butanone

S ***

***

S

***

*

0

MS

**

0

0

S

**

*

*

MS

6. l,l-Dichlofoavetone

S

***

***

7. Trichloronitromethane

MS

0

0

8. Dichlomavelic avid methyl ester + 2-Clflccothiophene,

S, MS

***

***

2-Chlomlhiophene

MS

Chknvbenzene

S

! 9. 3-Chlomthiopbene

MS

10. 2,5-Dichlomthiophene

t

MS

S

0

i !

***

t I

I ***

$

0

***

0 -

***

0

I

o

***

0

0

*

0

•

0

***

- -

* * *

!

0

**

0

I 0 -

I [ ***

INFl = beginning of influent ditch, INF2 = end of influent ditch, before chemical additions EFF x = effluent *flex the secondary cladfica's, EFF2 = final effluent after the ecological basin • Peaks appemed simultaneously in the chromalograms Other marks as in Tables 2 and 3.

***

***

.

,

444

Non-chlorinated volatile organic compounds Several non-chlorinated volatile.organic compounds were also identified in the chromatograms. A typical feature of the ECF bleaching samples was the presence of 2-ketones in homologous series from pentane to nonane, together with the corresponding aldehydes (2-pentanal - 2-nonanal). Some of these compounds were also noted in the influent samples. Thiophene, dimethylsulphide and dimethyldisulphide were present in most of the bleaching effluent and the waste water influent samples, and smaU amounts of monoterpenes, most commonly ~and ~-pinene, 3-carene, camphene and d-limonene, those from the bleach plant. Monoterpenes and hydrocarbon derivatives of benzene (e.g. l-methyl-4-(1-methylethyl)-bonzene) were clearly the most abundant compounds in the influent~ The non-chlorinated compounds identified during TCF bleaching were similar to those during ECF bleaching: 2-ketones from butane to heptane and the aldehydes hexanal and butanal. Dimethyldisulphide produced the highest peak in the chromatogram for the sample taken at the f'LrStbleaching stage.

4 DISCUSSION

Bleaching effluent and total mill waste water samples taken during the processing of softwood and hardwood pulp in three kraft pulp mills were analyzed for volatile organochlorine compounds. T,e pools of three consecutive samples give a good indication of the general profile of volatile organic compounds in waste waters. It should be noted however, that even though careful sampling, losses of the most volatile compounds may occur during opening of the sample vials in the laboratory. Seventeen VOCCs were identified in the volatile fraction of the effluent from ECF bleaching, of which chloroform was thc most prevalent. This is consistent with earlier reports, where chloroform has been found in considerably high amounts in effluent (e.g. 13). Many of the chlorinated organic compounds that form after chlorination of humic acid or drinking water are the same as those found in effluent from pulp bleaching (14-17), as humic substances and the lignin in wood are similar in chemical composition. These compounds include chloroform, dichloroacetonitrile, chlorinated acetones, dichloroacetic acid methyl ester and bromodichloromethane, all of which were found in the bleaching effluent analysed here. The first three compounds have also been shown recently to be produced during the chlorination of humic acid by naturally occurring fungal chloroperoxidase (18). Chloroform is presumably produced by methyl ketone cleavage (19), and bromodichloromethane is a byproduct of this reaction formed in the presence of bromide. Other compounds occurring in substantial amounts were dichloroacetic acid methyl ester and 2,5dichlorothiophene. The former typically occurs in water samples as a result of chlorination, and has been detected previously in pulp mill effluent (20, 21). Tri- and teu'achlorothiophenes (19) and dichlorothiophene (22) have previously been identified in pulp mill effluent when gaseous chlorine is used for bleaching, but we found only monochlorinated and dichlorinated thiophcncs, a result which is consistent with previous data (6). The results imply the formation of less chlorine-substituted thiophenes with decreasing use of active chlorine for bleaching. As sodium thiosulphate was added to the samples to destIoy free chlorine and avoid the formation of chio-

445 rinated by-products, a fraction of the dichloroacetonitrile may have degraded with it (23), so that the abundances of dichloroacetonitrile in the samples may be too low. A new compound reported here is trichloronitromethane, tentatively identified in the acid fraction during softwood pulp bleaching at mill 1 and hardwood pulp bleaching at mill 3. Formation of this volatile compound during pulp bleaching seems, however, reasonable according to the available literature (12). There were some qualitative as well as distinct quantitative differences in the formation of VOCCs between the three pulp mills, the pattern of which was related to the amount of active chlorine used in bleaching. Less VOCCs were found following a lower 0 0 2 charge and hardly any when non-chlorinated agents were used. Furthermore, dilution of the compounds at the bleach plants and waste water treatment plants may partly explain the differences. No differences in the formation of VOCCs during bleaching could be noted here between the two pulp species, however, due to changing process paran~ters. The fate of organic micropollutants in activated sludge plants may be affected by adsorption onto solids, biological degradation and transformation, chemical degradation or volatilization (24). Volatilization may be the dominant removal process for non-biodegradable compounds with Henry's law constant, K R > 10"3 ah'lam 3 tool"1 and an octanol-water partition coefficient, log Ko,, < 5 (25). Chlorinated compounds are typically poorly biodegraded in activated sludge plants. The constants KH and Kow for chloroform, bromodichloromethane and chlorobenzene indicate that the main losses occur via volatilization, but these constants have not been determined for all the compounds identified here. Since chloroform (Kit 2.88 x 10"3, log Ku,, 1.97) constitutes by far the major fraction of the VOCCs, it can be used as a representative of the remaining ones. Chloroform has been shown to be removed effectively in aerated lagoons, for example (26). It is not only the aeration basins at waste water treatment plants that may be sources of VOCCs released from pulp mills, however, as they may also enter the atmosphere in the vent gas from bleach plants. Estimation of the relative importance of these two sources would need more extensive measurements, however. Traces of C2-chlorocarbons have been detected previously in the volatile fraction of bleaching effluent and waste water effluent (6, 13)+ These chlorocarbons are reactive in the atmosphere and eventually produce several degradation products, e.g. trichloroacetyl chloride, which can be hydrolized to tricMoroacetic acid (27, 28). Conifer needles in the forests surrounding kraft pulp mills have been shown to exhibit enhanced trichloroacetic acid levels (29). The high temperatures of the bleaching effluent 0 2 - 68 °CO may have already caused the highly volatile short-chain chlorocarbons to evaporate before sampling. Furthermore, the sensitivity of the method used here was probably not high enough to f'md these chlorocarbons in our samples. VOCCs formed in bleaching of pulp may also enter workroom air (30). Chloroform, dichloroacetonitrile and bromodicMoromethane are potential carcinogens, whereas tricMoronitromethane and 1,2-dicMoropropane exhibit irritating effects in humans. Several of the non-chlorinated volatile organic compounds detected in the samples originate as natural constituents of wood material. Monoterpenes, which appeared in the infiuents in large amounts are highly volatile constituents of wood and have also been detected in the plumes from kraft pulp mills (31).

446 In summary, several volatile organochlorine compounds were formed during the bleaching of pulp with CIO2, of which chloroform constituted a major fraction. Other abundant compounds were dichloroacetic acid methyl ester and 2,5-dichlorothiophene. Distinct differences in the formation of VOCCs were noted between the three pulp mills, those being related to the use of C102, as a lower CIO2 charge yields less VOCCs. Dilution of the compounds at the wash filters of bleach plants and with other process water at waste water treatment plants may also partly explain the differences. In order to achieve a comprehensive view of the VOCCs volatilized from pulp mills, atmospheric emissions of these compounds in plume stacks and over aeration basins should be determined.

Acknowledgements The authors thank the representatives of the pulp mills for their co-operation, Jukka Maittalii for technical assistance during the sampling and Christina Rosenberg for the generous gift of two reference compounds. The constructive comments of the manuscript provided by Piiivi Kurttio and Aria Hirvonen, and the linqulstical revisionby Malcolm Hicks are gratefullyacknowledged. The research was supported financiallyby the Environmental Science Council of the Academy of Finland.

REFERENCES 1. Lindsu'tm-Seppli, P., and A. Oikari. 1989. Biotransformation and other physiological responses in whitefish gaged in a lake receiving pulp and paper mill effluents. Ecotoxicol. Environ. Saf. 18:191-203. 2. Lindstrt~m-SeppA, P , and A. Oikari. 1990. Biotransformation and other toxicological and physiological responses in rainbow trout (Saimo gairdneri Richardson) caged in a lake receiving effluents of pulp and paper industry. Aquat. Toxicol. 16:187-204. 3. Kringstad, K. P., and K. Lindstr~m. 1984. Spent liquors from pulp bleaching. Environ. Sci. Technol. 18:236248. 4. Deardorff, T. L., R. R. Willhelm, A. J. Nonni, J. J. Renard, and R. B. Phillips. 1994. Formation of polychlorinated phenolic compounds during high chlorine dioxide substitution bleaching. Tappi J. 77:163-168. 5. Rantio, T. 1995. Chlorinated cymenes in effluents of two Finnish pulp mills in 1990-1993. Chemospher¢ 31:3413-3423. 6. Rosenberg, C., T. Aalto, J. Tomaeus, and A. Hesso. 1991. Identification by capillary gas chromatography-mass spectrometry of volatile organohalogen compounds formed during bleaching of kraft pulp. J. Chrom. 552:265-272. 7. Watts, G. B., and B. R. Locke. 1993. Nonpurgeable total organic halide analysis and the characterization of river water quality adjacent to the discharge from a kraft mill. Environ. Sci. Technol. 27:2311-2317. 8. Peck, V., and R. Daley. 1994. Toward a "greener" pulp and paper industry. The search for mill effluent contaminants and pollution prevention technology. Environ. Sci. Technol. 28:524-527. 9. Calamari, D., P. Tremolada, A. D. Guardo, and M. Vighi. 1994. Chlorinated hydrocarbons in pine needles in Europe: Fingerprint for the past and recent use. Environ. Sci. Technol. 28:429-434.

447 10. Blatt A. H. 1943. Organic syntheses. Collective Volume 2. John Wiley & Sons, Inc. New York. 654 p. 11. Fieser, L. F., and M. Fieser. 1967. Reagents for organic synthesis. John Wiley and Sons, Inc. New York. 1457 p. 12. Boit, H.-G. 1974. Beilsteins Handbuch der Organischen Chemic. Springer-Verlag, Berlin, Heiderberg, New York. 13. Leuenberger, C., W. Giger, R. Coney, J. W. Graydon, and E. Moinar-Kubica. 1985. Presistent chemicals in pulp mill effluents, Occurence and behaviour in an activated sludge treatment planL Water Res. 19:885-894. 14. Christman, R, F., D. L. Norwood, and J. D. Johnson. 1985. New directions in oxidant by-product research: Identification and significance. Sci. Tot. Environ. 47:195-210. 15. De Leer. E. W. B., J. S. S. Damste, C. Erkelens, and L. de Galan. 1985. Identification of intermediates leading to chloroform and C-4 diacids in the chlorination of humic acid. Environ. Sci. Technol. 19:512-522. 16. Lindstr6m, IC, and F. ~)sterberg. 1986. Chlorinated carboxylic acids in softwood kraft pulp spent bleach liquors. Environ. Sei. Technol. 20:133-138. 17. Italia, M. P., and P. C. Udcn. 1988. Comparison of volatile halogenated compounds formed in the chloramination and chlorination of humic acid by gas chromatography-electron-capture detection. J. Chrom. 449:326-330. 18, Hoekstra, E. J., and E. W. B. De Leer. 1995. Organohalogens: the natural alternatives. Chemistry in Britain 31:127-131. 19. Rook, J. L 1974. Formation of haloforms during chlorination of natural waters. Wat. Treat Exam. 23:234-243. 20. Kringstad, K. P., P. O. Ljungqvist, F. de Sousa, and L M. StriSmbetg. 1981. Identification and mutagenic properties of some chlorinated aliphatic compounds in the spent liquor from kraft pulp chlorination. Environ. Sei. Technol. 15:562-566. 21. Suntio, L. R., W. Y. Shiu, and D. Mackay. 1988. A review of the nature and properties of chemicals present in pulp mill effluents. Chemosphere 17:1249-1290. 22. Voss, R. H. 1983. Chlorinated neutral organics in biologically treated bleached kraft mill effluents. Environ. Sci. Technol. 17:530-537. 23. Keith, L. H. 1990. Environmental sampling: A summary. Environ. Sei. Technol. 24:610-617. 24. Meakins, N. C., J. M. Blubb, and J. N. Lester. 1994. The fate and behaviour of organic micropollutants during wastewater treatment processes: A review. Int. J. Environ. Pollut. 4:27-58. 25. Matter-Mifller, C., W. Gujer, W. Giger, and W. Stumm. 1980. Nonbiological elimination mechanisms in a biological sewage treatment plant. Prog. Wat. TechnoL 12:299-314. 26. Lindstr~m, K., and M. Mohamed. 1988. Selective removal of chlorinated organics from kraft mill total effluents in aerated lagoons. Nordic Pulp and Paper Research Journal 1:26-33. 27. Tuazon, E. C., R. Atldnson, S. M. Aschmann, M. A. Goodman, and A. M. Winer. 1988. Atmospheric reactions of chloroethenes with the OH radical. Int. J. Chem. Kinet. 20:241-265. 28. Itoh, N., S. Kutsuna, and T. Ibusuki. 1994. A product study of the OH radical initiated oxidation of perchioroethylene and trichloroethylene. Chemosphere 11:2029-2040.

448 29. Juuti, S., Y. Norokorpi, and J. Ruuskanen. 1995. Trichloroacetic acid (TCA) in pine needles caused by atmospheric emissions of kraft pulp mills. Chemosphere 30:439-448. 30. Rosenberg, C., L. Nylund, T. Aalto, H. Kontsas, H. Norppa, P. JAppinen, and H. Vainio. 1991. Volatile organohalogen compounds from the bleaching of pulp - Occurrence and genotoxic potential in the work environment. Chemosphere 23:1617-1628. 31. Su'6mvall, A.-M., and G. Petersson. 1992. Photooxidant-forming monoterpenes in air plumes from kraft pulp induslries. Environ. Pollut. 79:219-223.