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Environmental Managementand Health7/ 4 [1996] 58

MCB University Press[ISSN 0956-6163]

Persist ent organochlorine compounds in water andsoil environments

Vlast a Drevenkar, Sanja Fingler, Zlat ko Frbe, Zelimira Vasilic Laboratory forOrganic Analytical Chemistry, Institute for Medical Research and OccupationalHealth, Zagreb, Republic of Croatia

Reviews compound physico-chemical properties and

water and soil propertiesinfluencing the transport anddistribution of organochlorine

pesticides, polychlorinatedbiphenyls (PCBs) and

chlorophenols in a water andsoil environment. As highlyhydrophobic compounds of

low water solubility,organochlorine pesticidesand PCBs are rapidly and

strongly sorbed by most soilsand sediments. The sorptionof weakly acidic chlorophe-

nols comprises both molecu-lar and ionic forms and

depends not only on thesoil/sediment organic matter

content but also on the pHand ionic strength of theaqueous phase. Brieflydescribes the analytical

methods for trace analysis oforganochlorine pesticides,PCBs and chlorophenols in

water and soil/sedimentsamples. Presents some

results of those micropollu-tants analysis in surface,ground and drinking waters,

soils, river sediments and wetdepositions in Croatia.

Persistent and toxic organochlorine (OC)

pesticides, polychlorinated biphenyls (PCBs)

and chlorophenols (CPs) belong to the

micropollutants of water and soil environ-

ments distr ibuted worldwide. The use of OC

pesticides has been restri cted or banned in

most developed countr ies but continues indeveloping countries. PCBs are a group of 209

congeners which have been wi dely used as

heat transfer fluids, hydrauli c fluids, flame

retardants and dielectri c fluids. For their

easier handling a systematic numbering has

been introduced and widely accepted as PCB

numbers[1]. In developing countr ies PCBs

have been substituted only partially. CPs,

particularly those with three and more chlo-

rine atoms have been used as fungicides wi th

main applications in the preservation of

wood, leather and texti les as well i n pulp and

paper industries. They are also intermediates

in the production of phenoxy herbicides and

degradation products of hexachlorocyclo-

hexane and chlorobenzenes. CPs can also be

formed by routine disinfection of drinking

water by chlorination as a result of chlorina-

tion of phenols and as by-products of the reac-

tion of hypochlorite with phenolic acids.

OC pesticides, PCBs and CPs enter the envi-

ronment either directly, mostly through the

pesticides appli cation and uncontrolled waste

discharge, or indirectly through atmospheric

transport. Their levels and distri bution in the

environment need to be controlled by means

of an environmental r isk assessment. PCBsare considered to be the main precursors of

highly toxic polychlorinated dibenzo-p-

dioxins (PCDDs) and polychlorinated diben-

zofurans (PCDFs). PCDD and PCDF traces are

contained also in technical tri-, tetra- and

pentachlorophenol formulations.

In this paper some factors influencing the

behaviour of persistent and li pophil ic OC

compounds in water and soil environments

and the analytical methods for analysis of OC

pesticides, PCBs and CPs in aqueous and

soil/ sediment samples are bri efly described.

The environmental levels of those pollutantsare illustrated by selected results of OC pesti-

cides, PCBs and CPs analysis in different

waters, soils, r iver sediments and wet deposi-

tions in Croatia.

Factors af fecting t ransport anddist ribut ion of PCBs, OC pest icidesand CPs in water and soilenvironments

The behaviour of OC compounds in water and

soil environments depends on both the spe-cific compound properties and on the waterand soil properties. Major physico-chemical

properties from the environmental point ofview are compound water solubility,li pophil icity and volatil ity (Table I). Com-

pound lipophil icity i s characterized byoctanol/ water partiti on coefficient Kow,

which correlates well with its water solubi l-ity, soil sorption and bioaccumulation.

As highly hydrophobic compounds of lowwater solubi li ty OC pesticides and PCBs are

rapidly and strongly sorbed by most soils[2,3]and in aquatic systems they are often associ-

ated wi th bottom sediments[4,5]. Due to theirlow degradabili ty these compounds accumu-late in sediments and aquatic organisms

relative to the concentration found in water.The sorption of PCBs is favoured by high soil

total organic carbon, high total aluminiumand iron oxides and high content of fine parti -

cles li ke si lt[2].Sorption of CPs to bottom sediments is

expected to be lesser than that of OC pesti-

cides and PCBs because of their lower Kowvalues (Table I). CPs are weak organic acidswith acidities in the pKa range from 5 to 9. At

typical ambient pH values, CPs, in particularthe highly chlorinated and more acidic tetra-and penta-CPs, are present in the aqueous

environment predominantly as phenolateanions. The sorption of CPs compri ses both

molecular and ionic forms[6,7] and dependson the pKa and Kow of the parti cular CP, on

the pH and ionic strength of the aqueousphase[7,8] and on the soil organic carbon

content[7,9]. In some cases a strong inter-action of chlorophenolates with organic-freemineral sur face was observed[9]. Some

charged species in the sorbent material, suchas Ca2+and Mg2+ ions also influence the CPs

sorption[6].Due to strong sorption in most soils the

transport of OC pesticides and PCBs throughthe soil to the surface and ground waters by

leaching is very slow or negligible. However,

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Vlasta Drevenkar, SanjaFingler, Zlatko Frbe,Zelimira Vasilic

Persistent organochlorinecompounds in water and soilenvironments


as the water solubili ty of CPs increases and

their sorption intensity decreases with

increase in pH value[7,8], they tend to be

transported by leaching especially i n neutral,basic and mineral soils wi th a low organic

matter content.The occurrence of OC pesticides, PCBs and

CPs in regions where they were not usedcould be explained only by their efficientatmospheric transport and subsequent wetand dry deposition. Their presence in therain and snow water[10-12] stems from disso-lution of gas-phase organics through gas-rainparti tioning and from scavenging of particlesand their associated compounds. Chlorophe-nols have much higher vapour pressures thanOC pesticides and PCBs (Table I) and exist in

the air almost entirely in the gaseousphase[10]. For these compounds gas scaveng-ing is much more important than particlescavenging. For semi-volatile lipophi li c com-pounds of low water solubi li ty such as PCBs,particle scavenging was shown to be theirdominant source in rain water samples[11].

Analysis of PCBs, OC pesticidesand CPs in water and soil / sediment

Concern about the sources, fate and environ-mental i mpact of OC compounds in theaquatic environment has stimulated thedevelopment of a variety of sensitive andcomplex analytical methods for their deter-mination at trace levels both in water and insoil / sediment samples. These methods gener-ally include a preconcentration step which is

accompli shed either by direct solvent extrac-tion[5,15-17] or by adsorption and subsequentelution from an appropriate adsorbent[17-20].

Hi gh-resolution capillary gas chromatogra-phy (HRGC) wi th electron capture and massspectrometric detection enables reli able iden-tification and trace levels quantification oftarget compounds. Before gas chromato-graphic analysis, chlorophenols are usuallyconverted into less polar derivatives althoughgas chromatographic[20] and high perfor-mance li quid chromatographic[7] proceduresfor analysis of non-derivatized chlorophenolsare also described.

In quali tative and quantitative analyses ofPCBs specific problems are encountered dueto the complex compositi on of PCB mixtures

both in environmental samples and in com-mercial formulations, which are often used asstandards[21]. PCBs are often quanti tated astotal PCBs: either as the sum of PCB con-geners expressed as a mixture or a combina-tion of technical PCB mixtures, or as a sum ofPCB congeners expressed as the sum of singlecongeners present in the sample. HRGC tech-niques enable effi cient separation and quan-titation of individual PCB congeners, e.g.congeners selected as typical and representa-tive of the most widely used PCBs: PCB 28, 52,101, 138, 153 and 180. For an environmentalrisk assessment the determination of themost toxic co-planar congeners and their

moderately toxic mono-ortho analogues is ofparamount importance. To minimize theinterferences, the determination of non-planar and co-planar PCB congeners shouldbe preceded by a pre-separati on step[22]. Foran accurate determination of both ortho- andnon-ortho-substituted PCBs a high perfor-mance li quid chromatographic pre-separa-tion step was proposed[16].The choice of analytical methods for stud-

ies of OC compounds in water and soil / sedi-ment samples in our laboratory isdetermined by the equipment at disposal forcontinuous use and by the necessity to

achieve a high detection sensitivity enablingtrace analysis. Due to the higher sensitivityof an electron capture detection than of detec-tion by mass spectrometry unambiguousidentification of organochlorine compoundsin di luted samples has been substituted byconcurrent sample analysis on two basicallydifferent gas chromatographic columns. Gaschromatographic-mass spectrometric analy-sis wi th an ion trap detector is used for moreconcentrated or pooled samples only.

OC pesticides and PCBs are accumulatedfrom aqueous samples by multiple extractionwith n-hexane[15] and from soil/ sedimentsamples by sonication of sample with 1:1acetone:n-hexane mixture[16]. The waterextracts are purified by washing wi th concen-trated sulphuric acid and the soil/ sedimentextracts are treated with copper powder,mercury and finally wi th sulphuric acid. The

Table I

Solubility in water (S), octanol/ water partition coefficient (Kow) and vapourpressure (vp) of selected OC pesticides, PCBs and CPs

Compound S, mol dm3 log Kow vp, Pa (C)

HCH isomersa 2105 7107 3.9 5105 2102 (20)

(-, -, -)4 ,4 -DDTa 6109 6.0 3105 (25)

4,4 -DDDa 2108 6.0 1104 (30)

4,4 -DDEa 3108 5.7 9104 (30)

PCBsa 81010 1106 5.57.2 8105 3102 (25)

Di-, tri-CPb 4103 3102 3.24.4 2.311.9 (25)

PCPc 5105 (20C, pH 5) 5.2 2103 (20)

Notes:a S, Kow and vp data taken from [13]; PCB data refer to PCB congeners:

28 (2,4,4-trichlorobiphenyl),52 (2,2,5,5-tetrachlorobiphenyl),101 (2,2,4,5,5-pentachlorobiphenyl),

138 (2,2,3,4,4,5-hexachlorobiphenyl),153 (2,2,4,4,5,5-hexachlorobiphenyl) and

180 (2,2,3,4,4,5,5-heptachlorobiphenyl)b S and vp taken from [10], and Kow from [7]c S and vp taken from [14], and Kow from [7]

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accumulated pesticides and PCBs areanalysed, without previous separation, on apacked and a capillary gas chromatographic

column. PCBs are quantitated against a stan-dard mixture consisting of Aroclor 1242 andAroclor 1260 in a 2.5:1 ratio either by the indi-vidual peak or individual congenermethod[12].

CPs are accumulated from water samplesby C18reversed phase adsorpti on followed byelution wi th acetone and conversion to acetyland pentafluorobenzoil derivatives[17]. Theanalysis of both types of derivatives on twodifferent gas chromatographic columns isrecommended for a more reliable identifica-tion and quantitation of the compoundsanalysed.

OC pesticides, PCBs and CPs inwater and soil/ sediment samples inCroatia

The use of OC pesticides in Croatia has beenrestricted for some 30 years. The use of DDTwas restricted in 1972 and hexachlorobenzene(HCB) has been prohibited since 1978. -Hexa-chlorocyclohexane (-HCH, L indane) is stil lproduced and used in Croatia. Despite restric-tion some electri city facil ities stil l containPCBs.

Data on the presence of OC compounds inthe water environment in Croatia mostly

refer to the analysis of widely distri buted OCpesticides. Recent measurements indicatethat their levels are generally within ecotoxi-cologically acceptable limits characteristic ofglobal environmental pollution. To providean insight into the background levels andrisks imposed by the environmental presenceof OC pesticides, PCBs and CPs, we investi-gated the origins and levels of those com-pounds in surface, ground and drinking

waters, wet depositions, soil and riversediments from different areas inCroatia[12,15,23]. As an example the maxi-

mum concentrations of-HCH, total PCBs,and most frequently detected CPs: 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pen-tachlorophenol (PCP), measured over alonger period in di fferent waters and wetdepositions in the Zagreb city area, are listedin Table II . As a consequence of the regularuse of insecticide formulations containinglindane, -HCH was the only pesticidedetected in all aqueous samples and in thehighest concentrations. A ll surface, rain andsnow waters contained traces of PCBs andmost of the particle samples isolated from

rain and snow waters contained traces of theDDT-type compounds. PCP was the mostabundant chlorophenol in surface, groundand dri nking waters. Different CPs appearedregularly in rain and snow water samples andtheir concentrations in snow water weresignificantly hi gher than those in rainwater[12].

Data on levels and distr ibution of OC pesti-cides, PCBs and CPs in aquifer sediments andsoils in Croatia are generally lacking,although they are of crucial importance forevaluation of environmental pollution bythose hydrophobic pollutants. The maximumconcentrations of PCBs and selected OC pesti-

cides measured recently in surface soils andriver sediments from different areas both incontinental and in coastal parts of Croatia areshown i n Table II I. I n most of the surface soilsand river sediments the background concen-trations of total PCBs were lower than 10gkg-1. The highest PCB concentrations, listedin Table II I, were measured in a surface soilin the vicini ty of a transformer station and ina river sediment in the Karst region, pointingto a local source of pollution. The OC pesti-cides most frequently detected in soil / sedi-ment samples were DDT and its degradationproducts and -HCH. Owi ng to the high envi-ronmental persistence and the highestlipophil icity in the seri es of pesticidesanalysed, DDT and its degradation products

Table I IMaximum concentrations of selected OC compounds in waters and wetdepositions in the Zagreb city area in period 1992-1995 for -HCH and PCBs

and 1984-1995 for CPsMaximum c oncentrations, ng dm3

Water -HCH PCBs 2,4 ,6-TCP 2,3,4 ,6-TeCP PCP

Sava river 5 25 62 69 163

Small streams 6 13 17 93 238

Lakes 2 14 27 2 5

Ground wat er 4 1 24 46 151

Drinking water 1 2 9 10 123

Rain w at er 38 205 69 63 19 pa r t ic lesa 512 4,155 ndb ndb ndb

Snow

w at er 6 50 210 527 131 pa r t ic lesa 242 4,082 ndb ndb ndb

Notes:a Concentration expressed in ng g1b Not determined

Table III

Maximum concentrations of PCBs and selectedOC pesticides in surface soils and river sedi-ments in Croatia in the period 1993-94

Maximum concentration, g k g1

Compound Sur face soil River sediment

PCBs 165.5 507.1HCB 0.3

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have a high capabil ity of sorption andaccumulation in soils and sediments.Consequently, in both soil and river sediment

samples the maximum concentrations ofDDT-type compounds were higher than thoseof other OC pesticides.

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