Contamination by chlorinated hydrocarbons (DDT, PCBs) in surface sediment and macrobenthos of the river Adige (Italy)

The Science of the Total Environment, 65 (1987) 21-39 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

21

CONTAMINATION BY CHLORINATED HYDROCARBONS (DDT, PCBs) IN SURFACE SEDIMENT AND MACROBENTHOS OF THE RIVER ADIGE (ITALY)

B. PAVONI', B. DUZZIN2 and R. DONAZZOLO1 ~Department of Environmental Sciences, University of Venice, Venice (Italy) eDepartment of Biology, University of Padua, Padua (Italy)

(Received November 10th, 1986; accepted December 26th, 1986)

ABSTRACT

Surface sediments and macrobenthos communities have been employed as contamination indicators for halogenated hydrocarbons (DDT and PCBs) in the river Adige and its tributaries Fibbio and Alpone in the province of Verona. Two sampling campaigns were carried out, before and after the spring-summer floods, to determine the effects of this event on the contamination of the river. The halocarbons in the sediment were found to be associated with the fine fraction (< 53#m) and organic carbon. From the relative concentrations of contaminants determined at various sampling stations, some information has been obtained on the sources.

INTRODUCTION A r e s e a r c h p r o g r a m m e is in p r o g r e s s to e v a l u a t e the q u a l i t y of t h e a q u a t i c e n v i r o n m e n t in t h e R i v e r Adige a n d its p e r p e t u a l flow t r i b u t a r i e s a n d to c h a r a c t e r i z e t h e m a c r o i n v e r t e b r a t e c o m m u n i t i e s living in them. T h e r i v e r flows t h r o u g h t h e T r e n t i n o - A l t o Adige a n d V e n e t o r e g i o n s l o c a t e d in the n o r t h e a s t e r n p a r t of Italy. I n the p r e s e n t w o r k , focused on t h e t r a c t of t h e r i v e r in t h e p r o v i n c e of V e r o n a a n d o n t h e m a i n t r i b u t a r i e s Fibbio a n d Alpone, the s u r f a c e s e d i m e n t s a n d the m a c r o b e n t h o s h a v e b e e n studied as c o n t a m i n a t i o n i n d i c a t o r s for c h l o r i n a t e d h y d r o c a r b o n s (o,p'- + p , p ' - D D T , DDD, D D E a n d p o l y c h l o r i n a t e d biphenyls), a n d t h e c o n c e n t r a t i o n s of t h e s e c o m p o u n d s h a v e b e e n i n t e r p r e t e d in t e r m s of o t h e r c h e m i c a l , physical, g e o g r a p h i c , s e a s o n a l a n d hydrographic parameters. H a l o c a r b o n s , w h o s e o r i g i n is t y p i c a l l y a n t h r o p o g e n i c (both a g r i c u l t u r a l a n d industrial), through biological accumulation and amplification cause severe d a n g e r to living o r g a n i s m s . T h e s e non-polar, l o w - w a t e r - s o l u b l e c o m p o u n d s t e n d to be bound, s o r b e d a n d a c c u m u l a t e d in t h e lipidic f r a c t i o n of h u m i c s u s p e n d e d m a t e r i a l s a n d e v e n t u a l l y a c c u m u l a t e in the s e d i m e n t s ( H a r t u n g , 1975; Choi a n d Chen, 1976; H a q u e et al., 1977). A l t h o u g h s e d i m e n t s do n o t c o n s t i t u t e a d i r e c t m e a s u r e of t h e d e g r e e of a q u a t i c pollution, t h e y offer a n

0048-9697/87/$03.50

© 1987 Elsevier Science Publishers B.V.

22

irreplaceable aid in identifying the sources and in monitoring the time evolution of the contamination (FSrstner, 1981). The concentrations of halocarbons in the sediments are dependent on the nature and the discontinuity of the inputs, on the river hydrographic regimen, i.e. on the sequence of low and high water periods, on the contribution of materials from the tributaries, on the sediment grain size composition and on the organic material content. Benthic macroinvertebrates are reported to accumulate halocarbons to high concentrations and participate in many food webs in the aquatic environment (Holden, 1972; Thompsom and Edwards, 1974; Ghetti et al., 1978). Macroinvertebrates, when compared with other aquatic organisms such as bacteria, protozoa, algae and fish, offer some special characteristics that make them preferable for study. They are relatively abundant and easy to collect, live firmly stuck to the bottom, thus recording all the stream variations, are present in all levels of the food chain and are the principal component of fish diet (Ghetti and Bonazzi, 1981). Chlorinated hydrocarbons are readily accumulated by aquatic organisms in the fats and oils of their organs and tissues and concentrated through the food chain. This is due to the chemical stability and the high partition coefficient of such compounds between lipids and water (Kenaga, 1972, 1975, 1980). Bottom dwellers, such as macroinvertebrates, are strongly affected by these contaminants. It is clear that bioaccumulation processes of these pollutants take place through passive diffusion from the water into the cell membranes of tegumental tissues, rather than by active transport via food (Falkner and Simonis, 1982). Most of the contaminants sorbed onto suspended particles or accumulated in sediments are not readily available to living organisms (Haque et al., 1977; Wildish et al., 1980; Rubinstein et al., 1983). However, on occasion of changes in the chemical-physical condition of the water, because of the resuspension of deposited particulates, microbial activity, changes in the partitioning equilibria between water and sorbed organic substances, pollutants can become available to biota (Young et al., 1977). In this paper we will try to answer the following questions: - - what is the degree of pollution of the river by halocarbons?; - - what is the effect of the flow regimen on the river contamination?; - - w h a t is the response to pollutants of different macroinvertebrate communities?; - - is there any relationship between the concentration of these pollutants in the sediments and the percentage of organic carbon (as a measure of the organic matter) and fine fraction?; - - which substrate, the sediment or the macroinvertebrates, is a better monitor of halocarbon pollution? Macroinvertebrate samples representing entire communities were used for analyses, both because it was impossible to find the same species along the whole length of the river, and moreover because no evident differences are reported in the bioaccumulation ability between species of aquatic invertebrates even though belonging to distinct trophic levels (Sodergren et al., 1972; Sodergren and Svensson, 1973; Ghetti et al., 1978).

23 DESCRIPTION OF THE STUDY AREA

The Adige, one of the most important rivers in Italy, has a catchment basin of 11954km 2 and a length of 409km. A large part of the river tract is in the province of Verona (Fig. 1). The hydrologic regimen is typically "alpine" with heavy floods in the late spring and summer, abundant flow in autumn and low water in late autumn, winter and early spring. The annual flow measured at Trento (95 km north of Verona) for the period 1951-1972 is shown in Fig. 2. The river water is used extensively for hydroelectric, irrigation, drinking and recreational purposes. In particular, large amounts of water are diverted into canals for hydroelectric power production; this water returns to the river south of Belfiore (Fig. 1). All the river-connected activities have suffered from the effects of the progressive degradation of water quality, since the river ultimately collects uncontrolled wastes of different origin: from industries (food, textile, tanning, paint, paper, chemical, iron, marble and cement); intensive single crop agriculture (grape, fruits, cereals), which require considerable use of fertilizers and pesticides; and rapidly developing zootechnics (Braioni, 1983). Few towns have adequate sewage systems and/or water treatment plants. TRENTO PROVINCE O

Mounts

Lesslnl

BUS

/

Belfiore zevio

Albaredo

Irrigation canals P

Hychoelectric canals Hydroelectric

0

~

.

~9_

power plonts

5 km ROVIGO PRovINCE

Fig. 1. The River Adige, tributaries and the hydroelectric canals in the province of Verona.

24 --A-1880

max

--II-- m l n --0-- mean

A

1\

1600 1520

1020

/\ /

1050-

650-

E 00

/

v

\/

l

0

months Fig. 2. Adige river flow measured at Ponte S. Lorenzo (Trento) by the Uffieio Idrografieo della Provineia Autonoma di Trento in the period 1951-1972.

Only in 1984 has a large treatment plant come into operation processing sewage from part of Verona. SAMPLING STATIONS

The five sampling stations are shown in Fig. 3; Stations 1, 2 and 5 are located on the river itself, and Stations 3* and 4* on the tributaries Fibbio and Alpone. These sites were chosen from the 14 previously considered by Duzzin (1981), because they were the most interesting from a chemical and biological viewpoint. Station 1, Ceraino, is located 10 km south of the province border; the river bed, relatively narrow, lies between the slopes of the Pre-alps and consists of large pebbles with coarse gravels and sand. This will be taken as the reference station, since the quality of the water here was found to be better than at the other stations. Station 2, Villa Buri, is located immediately south of Verona. The strongest part of the current flows in a deep channel, a minor part wanders in a wide bed of pebbles and coarse sand. The water is heavily affected by the pollution load from the city. Station 5, Villa Bartolomea, is located 6 km upstream from the

25 TRENTO

\

•

Sampling stations

O Background sampling stations 5 0

I0

BG3 O

V. Ba r tolome;~l~

\ ROVIGO PROVINCE

Fig. 3. Surface sediments and macrobenthos sampling stations.

southern border of the province. Characteristics of the Adige are high embankments and sandy bed. The water quality largely depends on the flow rate and the pollution load discharged upriver. Station 3* is located on the final tract of the tributary Fibbio, which rises from groundwater and flows through an agricultural and industrial area. Water temperature and flow are fairly constant throughout the year except for a high increase in autumn. Sediments are mainly fine grained. In spring and summer the thick vegetation along the banks favors deposits of large quantities of fine materials that are later washed away by the autumn currents. Station 4* is located on the final tract of the tributary Alpone, which is fed by three streams: the torrent Tramigna, which originates from groundwaters; the Alpone, which flows from the Alps; and the Chiampo, which receives some of the highly polluted wastes from Arzignano, in the province of Vicenza, where over 170 tanneries are located. The bed consists of pebbles and gravel in the middle, sand and mud on the banks. The prevailing regimen is alpine. At these stations, in permanently submerged microenvironments, two series of samples were collected during low water periods. The first sampling took place on 5 J u n e 1982 when the stream was at low water for about 1 month; the

26 second on 22 February 1983 when, after the summer-autumn floods, the winter low water conditions had become stable. MATERIALSAND METHODS: SAMPLINGPROCEDURES Surface sediments were collected using an Ekman grab sampler in the case of soft bottoms (Stations 3*, 4* and 5) and by shovel elsewhere. At most stations three subsamples were taken and sieved through a 2 mm stainless steel sieve to remove the coarser materials and then homogenized in wooden basins. Sediment fractions for chemical analyses, ~ 1 kg wet weight, were preserved in air-tight, aluminum-lined glass jars, previously cleaned with concentrated HNO3, rinsed with tap water and then with distilled water, acetone and nhexane. The fractions suitable for grain size analyses, ~ 3 kg, were kept in plastic bags. The macrobenthos was sampled in such a way that the macroinvertebrate communities of the particular environmental typologies were represented as closely as possible and in sufficient quantities (10-15 g of biomass) to allow determination of halocarbon concentrations. A Surber sampling net was used (0.1m 2 surface, 21 mesh). Each sample was sieved in situ to remove finer sediment, then placed in glass jars as described above. Sediments and benthos samples were transported to the laboratory in dry-ice-refrigerated containers and kept in a freezer at - 20°C until analysed. On one occasion (first campaign, Station 3* located on the tributary Fibbio) no macrobenthos organisms were found. The chemical analyses were performed on the whole sediment and not on the fine fraction previously separated; this was to avoid loss of analytes present in trace amounts.

Sediment fine fraction percentage determination A sieve ASTM 270 (53pm) was used. The fraction separated is therefore comparable to the "fine fraction" that Rofes (1980) defines as consisting of particles < 50 #m. About 2 kg of the sandy, or 0.5 kg of the clayey, sediment were dried at 105°C, weighed and then wet sieved with bi-distilled water. The obtained fine fraction was dried at 105°C and then reweighed (Lameri, 1982).

Macrobenthos preparation The macroinvertebrates were thawed, separated from mud and debris and the various communities identified on the basis of dominant taxa (Table 1). Determination of the genus or superior taxon, as in the cases of Mollusca, Oligochaeta, Hirudinea and Diptera, was adequate for our purpose. Classification according to species is in progress by experts from the Natural History Museum, Verona. Organisms were washed several times with distilled water, then homogenized in a Waring-Blendor blender and finally freeze-dried in a Modulio-Edwards apparatus.

27 TABLE 1 C o m p o s i t i o n of m a c r o i n v e r t e b r a t e Station a

1

2

1Cp

2Cp

x

+

Mollusca Oligoghaeta

c o m m u n i t i e s a t t h e five s a m p l i n g s t a t i o n s

Hirudinea

3*

1Cp

2Cp

1Cp

4*

2Cp +

x

+

+

+

x

1Cp

5

2Cp

x

+

+

-

1 Cp

÷

2Cp

+ +

Isopoda Asellus

Anphipoda Echinogammarus

x

+

+

-

Ephemeroptera Baetis

-

+

-

×

+

+

-

×

+

-

Caenis Cloeon Ecdyonurus Ephemerella Rhithrogena

Plecoptera Perlidae Protonemura

-

-

Trichoptera Hydropsyche

-

Rhyacophila

+

Diptera

+

-

~( × ) D o m i n a n t ; ( + ) c o m m u n e ; ( - )

+ +

+

-

x

-

rare.

Chemical analyses Organic carbon in the sediments was determined with a Total Organic Carbon Analyzer Beckman 915B and an Elemental Analyzer Perkin Elmer 240B. The reported data are the sum of soluble and insoluble organic carbon (Fr61ich, 1980). Halocarbon (o,p', p,p'-DDT,-DDD,-DDE; PCBs) concentrations were determined by gas chromatography after extraction with n-hexane, cleanup with H2SO4 and Florisil, and separation of PCBs from DDTs on silica gel. If compared with the method described in Donazzolo et al. (1983), the procedure used in the present work is different in the instrumental analysis step: Chromatograms were run with two capillary columns; one 25 m long, 0.3mm i.d. and coated with SE 54 stationary phase, the second 12 m long, 0.2 mm i.d. and coated with SE 30. Confirmation was by gas chromatography-mass spectrometry. The GC instrument was a Hewlett-Packard 5840 A equipped with a SE 54 capillary column (length 25m; i.d. 0.3mm). The MS instrument was Hewlett-Packard 5985 B coupled to an HP 1000 computer. Instrument settings were: source

28

o

v

o

o

~

V

.<

o

~

~

~

. . . . . . . .

V

~

~

~

0

o

~

o

V

~

V

v

~

'

~ ~

~

~

v v ~

~

0 V

~

V

~

V v

0

V

V

~

V

V

V ~

V

VV

~

0 o V 0

0 0

o

o

V

V

29

temperature, 200°C; analyzer, 140°C; electron multiplier voltage, 70 ev. Standard chromatograms and mass spectra were acquired using the "total ion mode"; quantitative analyses were performed using the "selected ion monitoring mode". RESULTS AND DISCUSSION

The concentrations of halocarbons in the sediment and macrobenthos samples of the two sampling campaigns are reported in Table 2 and Figs 4 and 5; they can be interpreted better if we first review the natural processes that occurred in the river catchment area during the period before the samplings. The first campaign was carried out in June 1982 and the second in February 1983; the period in between was therefore characterized by the summer floods and the autumn-winter medium-low water conditions. The entire basin was washed out and large amounts of suspended materials were transported to the river. In the same period the tributaries underwent different processes: in the Fibbio, a groundwater stream, in autumn the increased flow removed the upper fine sediments deposited during the summer and held by thick vegetation, so uncovering coarser sediments; in the Alpone, which is supported by quite a large catchment basin, the sediments were substituted by others from the ppb

T. DDT Sediments

160-

120I \ I

80-

\

40-

ppb 1200-

I

I

I

I

I

1

2

3e

4°

5

~DDT Macrobenthos I.... I

2Cp

/

soo 400

...........j "'~

/i'

/

1Cp

J

I

I

I

t

I

1

2

3e

4e

5

STAT ION S

Fig. 4. Surface sediments and macrobenthos of the River Adige (Stations 1, 2 and 5) and tributaries (Stations 3* and 4*). ZDDT concentrations (ppb dry weight).

30 PCBs

Sediments

ppb 160 /

1208040-

I

',X,

I

I

I

1

2

3°

PCBs M a c r o b e n t

I

]

4•

5

hos

ppb I 6ool

~ ~cp /

400 1

1

I

I

1

2

,...-. ........ |

3¢

I

I

4"

5

STATIONS

Fig. 5. Surface sediments and macrobenthos of the river Adige (Stations 1, 2 and 5) and tributaries (Stations 3* and 4*). PCBs concentration (ppb dry weight).

basin. The effects of these phenomena are evident in the data of the percentages of fine fraction and organic carbon in the sediments of the two campaigns: both parameters increase in the stations on the river and decrease in the Fibbio, whereas in the Alpone an increment in the fine fraction percentage is associated with a reduction in the percentage of organic carbon (Table 3). The composition of the macrobenthos communities collected in the two campaigns is shown in Table 1. The protracted low water period (~ 1 month) t h a t preceded the first sampling strongly affected the tributaries and the tract of the river south of Verona. The Fibbio sediments were depopulated, whereas the communities at Stations 2 and 5 were much simplified and consisted of numerous organisms belonging to taxa that cope better with very selective environmental conditions. At Station 5, where the sandy substrate is an important limiting factor for many species, a numerically abundant community of Amphiphoda, Diptera and Hirudinea was found. A very different community distribution was found in the second sampling at all stations. At Stations 2 and 4* in particular, some species that do not usually populate these environments and whose presence was probably due to drift, were sampled. For no apparent reason very few organisms were collected at Stations 1 and 5.

31

r...)

~ r...3 V~

5. r~ L,~

,,....i

&v

r..,)

~.

o

r~

15,

r~

~e

~~

,4

r.) I= 0

r~

m~v

32

Sediment analyses As far as the sediments are c o n c e r n e d , the highest c o n c e n t r a t i o n s of the two classes of c o n t a m i n a n t s (DDTs and PCBs) were d e t e c t e d in the samples from the stations l o c a t e d on the two t r i b u t a r i e s and in the last s t a t i o n on the r i v e r (5). S t a t i o n 3* had the highest absolute values, w h e r e a s the o t h e r stations had c o n s i d e r a b l e c o n c e n t r a t i o n s in o n l y one sampling. S t a t i o n s 1 and 2 are the least c o n t a m i n a t e d , with c o n c e n t r a t i o n s < 10ng g-1 (ppb). If we c o m p a r e the v a l u e s d e t e r m i n e d in the second sampling with those o b t a i n e d in the first, a n o t i c e a b l e d e c r e a s e is observed at S t a t i o n s 1, 2 and 4*, and an i n c r e a s e at S t a t i o n s 3* and 5. At S t a t i o n 4* the sediment s u b s t i t u t i o n c a u s e d by the floods led to l o w e r c o n c e n t r a t i o n s of c o n t a m i n a n t s . The downs t r e a m drift of the c o n t a m i n a t i o n from the r i v e r and the t r i b u t a r i e s is r e c o r d e d at S t a t i o n 5: at the second sampling the c o n c e n t r a t i o n s i n c r e a s e d a b o u t 6 times for DDT and a b o u t 20 times for PCBs. T h e c o n c e n t r a t i o n i n c r e a s e observed at S t a t i o n 3* on the Fibbio is r e l a t e d to the floods, w h i c h r e m o v e d the fine surficial slime, exposing d e e p e r sediments c o n t a m i n a t e d d u r i n g a previous period, w h e n these substances, p a r t i c u l a r l y DDT, were more widely used. An a t t e m p t was made to r e l a t e the c o n c e n t r a t i o n s of these s u b s t a n c e s to the p e r c e n t a g e s of fine f r a c t i o n and o r g a n i c c a r b o n in the sediments. The correl a t i o n coefficients o b t a i n e d from l i n e a r r e g r e s s i o n a n a l y s e s considering the fine f r a c t i o n and the o r g a n i c c a r b o n c o n t e n t s as the i n d e p e n d e n t variables are r e p o r t e d in Table 4. T h e y are s t a t i s t i c a l l y significant, even t h o u g h t h e i r import a n c e is limited by the r e l a t i v e l y few d a t a a v a i l a b l e and the lack of interm e d i a t e v a l u e s of the i n d e p e n d e n t variables; however, t h e y indicate t h a t a large p a r t of the v a r i a b i l i t y a s s o c i a t e d with o r g a n o c h l o r i n e c o n c e n t r a t i o n s in the samples studied c a n be e x p l a i n e d by the r e l a t i o n s h i p s with the fine f r a c t i o n and o r g a n i c c a r b o n p e r c e n t a g e s and with the a b s o r p t i o n ability of the sediTABLE 4 Linear correlation coefficients obtained from regression analyses considering the percentages of fine fraction and organic carbon as independent and the pollutant concentrations as dependent variables ZDDT, PCBs vs. % < 53pm fraction

ZDDT, PCBs vs. % Org. Carb.

r

r

ZDDT

0.74 (95.0%)

PCBs

0.94 (99.9%)

r* 0.88 (99.0%)

0.Sl (99.0%)

r* 0.95 (99.9%)

0.99 (99.9%)

r: linear correlation coefficient using data from all stations (n = 10); r*: linear correlation coefficients obtained using data from all stations except station 4* (n = 8). In brackets are reported the significance levels.

33 ment. It is in fact well known that the fine fraction percentage is strictly related to the surface area available for sediment-organochlorine interactions. The organic carbon percentage, on the other hand, is a measure of the organic material content, whose lipidic fraction binds such compounds. A considerable improvement in the correlation coefficients, and therefore in the significance implied, is observed if the ZDDT concentrations of Station 4* are excluded. We arbitrarily decided to remove those data from the regression, since they abnormally exceeded the intervals indicated by the whole data set. If we emphasize the dependence of organochlorine concentrations on fine fraction and organic carbon percentages and consider the ratio "concentration of EDDT or concentration of PCBs"r'percentage of fine fraction or percentage of organic carbon" (i.e. the contaminant concentration per unit percent of fine fraction and organic carbon, Table 3), it becomes apparent that the high concentrations determined at Station 3* were mainly due to large amounts of fine material and organic matter, whereas at Stations 4* and 5 high contaminant concentrations were present associateci with lower values of the considered parameters, i.e. in sediments of poor absorption capacity. In conclusion, from a study of the sediments the worst pollution is detected for DDT and PCBs, at a comparable degree, at the stations located on the tributaries (mainly 4*) and in the southernmost tract of the river.

Macrobenthos analyses Organochlorine concentrations determined in the macrobenthos are more significant contamination indicators than those determined in the sediments. At all stations both EDDT and PCBs are in much higher concentration in the macrobenthos than in the sediments, with bioaccumulation factors (referred to the sediment) from 3.4 to 119.7 for EDDT and from 1.5 to 261 for PCBs (Table 5, Fig. 6). For DDT the highest value is recorded at Station 5 and the lowest at Station 3*; for PCBs the highest values are recorded at Stations 1, 2 and 5 and the lowest again at Station 3*. If we compare the data from the second sampling campaign with those from the first, in all cases except one, the concentrations increase substantially. These results yield different information from that derived from the sediments, but the situation will be much clearer if we consider the mechanisms by which the organisms accumulate lipophilic contaminants. Most of these substances are taken up passively from the water through the skin, and such transfer is regulated by complex equilibria between the dissolved fraction, that inside the cells and the fraction adsorbed onto the suspended and deposited sediment. There is competition between the sediment and those factors that favor uptake by organisms (Wildish et al., 1980; Rubinstein et al., 1983). Therefore, at stations where the sediment is finely grained and rich in organic matter, the bioaccumulation factors are considerably lower, as is evident in the samples from Station 3*, where the lowest values are observed,

34

0

o c~ ~

~1

~

L~-

0 c~

V v

d

0

c~

0

0 o~

r~

~

~

~

o

35

>~DDTmb Z~DDT sd 125100755025

lCp ~/' "'""""'.

/

2Cp

\/

PCBsmb PCBssd 20015010050

\\\\\\

~..

/1Cp

. . . . \.

ii

STATIONS Fig. 6. Bioconcentration factor of the macrobenthos compared with the sediments at the five stations.

and to a lesser extent in those from Station 4*. At stations with very coarse grained sediments, e.g. Station 5, high accumulation factors are recorded. If we examine all the halocarbon data obtained from both the sediments and the macrobenthos of the two sampling campaigns carried out before and after the summer-autumn floods, it appears that the increased flow and the basin washing caused a renewal of river sediments and a recovery of some river areas, but large amounts of contaminants were mobilized and made available to benthic organisms, which showed a general increase of halocarbon concentrations. However, one more important factor contributed to the increase in the bioaccumulation ability of the macrobenthos sampled in the second campaign: the greater diversification of the communities. Communities consisting of several species compensate better for differences in life cycles and therefore in uptake abilities (Ghetti et al., 1978). As pointed out when discussing sediment data, macrobenthos data confirm that the station on the tributary Alpone (4*) and that on the last tract of the Adige (5) are the most polluted. From a comparison between the ZDDT and PCBs concentrations in both matrices (Tables 2 and 5, Fig. 7), it is apparent that in the area studied the highest values are those determined for ZDDT, but it is impossible to state that pollution is mainly due to one pollutant rather

36

~DDT PCBs

Sediments / !

\ \

t / " ' ~ - ~ 1 Cp

.,

i~//

~ ~ / "

DDT PCBs

\\ \ 2 Cp

Macrobenthos

98765432

1

•"": ,,'// \ 2Cp _~__.. /~ / ~lCp

STATIONS Fig. 7. ZDDT/PCBs ratios at the five sampling stations.

than to the other, except at Station 4*, where contamination by DDT and therefore by agricultural activities appear predominant. With regard to the individual components of ZDDT, the percentages of p,p'-DDD and p,p'-DDE are the highest in most samples (Tables 2 and 6), with TABLE 6 (o,p ~+ p,p') DDT, DDD, DDE percentages in the macrobenthos and surface sediments of the river Adige (Stat 1, 2 and 5) and tributaries (Stat 3*, 4*)

Station 1

2

3*

1Cp

2Cp

1Cp

2Cp

Macrobenthos ZDDT% ZDDD % ZDDE%

32 11 57

16 18 66

36 39 25

40 10 50

Sediments ZDDT% ZDDD% ZDDE%

13 54 33

32 15 53

19 49 32

55 36 9

1Cp

10 33 57

4*

5

2Cp

1Cp

2Cp

1Cp

2Cp

0 28 72

3 46 51

16 37 47

21 35 54

17 50 33

3 39 58

34 62 4

17 66 17

2 60 38

3 12 85

37 average ratios for (DDE + DDD)/ZDDT of 0.7 in the benthos and 0.8 in the sediment. These ratios, which are high and similar and whose meaning is "the amount of DDT degraded versus the total amount", lead one to believe that the pesticides determined at present were, to a large extent, dispersed years ago. However, we may conclude that the aquatic environment from which our samples were taken will require many years for its health to be restored due to the rather high concentration of non-degraded DDT and the consideration that the degradation compounds are as toxic as the original DDT itself (Bailey et al., 1979; Longcore et al., 1973). The situation may be even more serious for PCBs, since these chemicals, unlike DDT which was banned by Italian regulations (D.M. 11/10/1978), are still in use even though limited to non-dispersive systems. If we take into consideration that the high concentrations of both contaminants can be magnified several times through the food chain, particularly in fish, it is easy to infer that a potential danger exists for people who include in their diet fish caught in those streams. CONCLUSIONS The importance of analyzing both sediments and the macrobenthos to monitor the extent of pollution of an aquatic environment by halogenated hydrocarbons is apparent from the results of the present study. Sediments, even though characterized by changes related to the hydrology of the river, are good indicators since they adsorb halocarbons. Macrobenthos, on the other hand, readily bioconcentrate halocarbons, showing concentrations much higher than sediments. On this basis, in preparing future control programmes, sediment and macrobenthos analyses should always be scheduled. Macrobenthos sampling is more laborious, yet it is essential in studying halogenated hydrocarbons contamination. The macrobenthos collected in the second sampling displayed better bioaccumulation capacity, both because the communities were more differentiated than in the first campaign, and because more contaminants were mobilized by the preceding floods. The most suitable sampling period seems to be when the winter low water regimen has become stable. Data obtained from the sediments of both campaigns are important for an understanding of contamination dynamics. Variations of flow have been shown to have a strong effect on concentration fluctuations, with different effects on the main river and the tributaries. More samplings carried out on occasion of exceptional floods, or low water periods, or particularly heavy precipitation could be very useful. An interesting result of the halocarbon data interpretation was the existence of a relationship between the amount of fine fraction and organic carbon in the sediment and the halocarbon concentrations. Additional parameters, e.g. the phosphorus and nitrogen concentration in the sediment and the lipidic

38

fraction in the organisms, could also contribute to an explanation for the variability of halocarbon concentrations. ACKNOWLEDGEMENTS

This research was supported by a grant from the "Amministrazione provinciale di Verona" and by institutional funds from the Italian Ministry of Education. Some of the data reported are taken from the thesis of Dr M. Romeo. The authors are grateful to Prof. A.A. Orio and Prof. M.G. Braioni for valuable suggestions in planning and conducting the work. The assistance of Dr L. Diretto from the "Natural History Museum of Verona" in the sediment grain size analyses is acknowledged. REFERENCES Bailey, S., P.J. Bunyan, B.D. Rennisin and A. Taylor, 1969. The metabolism of 1,1-di(pchlorophenyl)-2-chloroethylene in the pigeon. Toxicol. Appl. Pharmacol., 14: 23-32. Braioni, A., 1983. Influenze antropiche sul tratto veronese dell'Adige. Atti Mem. Accad. Agric., Sci. Lett. Verona, 34: 3-35. Choi, W.W. and K.Y. Chen, 1976. Association of chlorinated hydrocarbons with fine particles and humic substances in nearshore surficial sediments. Environ. Sci. Technol., 10: 782-786. Donazzolo, R., L. Menegazzo-Vitturi, A.A. Orio and B. Pavoni, 1983. DDT and PCBs in sediments of the Venice Gulf. Environ. Technol. Lett., 4: 451-462. Duzzin, B., 1981. Indagine preliminare sulle caratteristiche fisiche e chimiche del tratto Veronese dell'Adige e dei suoi affluenti a regime perenne. Riv. Ital. Idrobiol., 20: 709-730. Falkner, R. and W. Simonis, 1982. Polychlorierte Biphenyle (PCB) im Lebensraum Wasser (Aufname und Anreicherung durch Organismen-Probleme der Weitergabe in der Nahrungspyramide). Arch. Hydrobiol. Beih. Engebn. Limnol., 17:1 74. FSrstner, U., 1981. Metal pollution assessment from sediment analysis. In: Metal Pollution in the Aquatic Environment. Springer-Verlag, Berlin, Heidelberg, pp. 71-109. FrSlich, P.N., 1980. Analysis of organic carbon in marine sediments. Limnol. Oceanogr., 25: 564-572. Ghetti, P.F. and G. Bonazzi, 1981. ! macroinvertebrati nella sorveglianza ecologica dei corsi d'acqua. C.N.R., Roma, AQ/1/127, 175 pp. Ghetti, P.F., G. Campanini and J. Gorbi, 1978. Changes in the amount of organochlorine pesticides in macroinvertebrate communities of the Val Parma Running Waters. Verh. Int. Ver. Limnol., 20: 1976-1987. Haque, R., P.C. Kearney and V.H. Freed, 1977. Dynamics of pesticides in the aquatic environment. In: M. Khan (Ed.), Pesticides in Aquatic Environments. Plenum Press, New York, pp. 3~52. Hartung, R., 1975. Accumulation of chemicals in the hydrosphere. In: R. Haque and V.H. Freed (Eds), Environmental Dynamics of Pesticides. Plenum Press, New York and London, pp. 185198. Holden, A.V., 1972. The effects of pesticides on life in fresh water. Proc. R. Soc. London, 180: 383-394. Kenaga, E.E., 1972. Factors related to bioconcentration of pesticides. In: F. Matsumura, G.M. Bousch and T. Misto (Eds), Environmental Toxicology of Pesticides. Academic Press, New York and London, pp. 193-228. Kenaga, E.E., 1975. Partitioning and uptake of pesticides in biological systems. In: R. Haque and V.H. Freed (Eds), Environmental Dynamics of Pesticides. Plenum Press, New York and London, pp. 217-274.

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