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Uptake and release of 51Cr(VI) and 51cr(III) by Barnacles (Balanus sp)
Marine Environmental Research 11 [1984) 201-211
Uptake and Release of 51 Cr(VI) and 51 Cr(llI) by Barnacles (Balanus sp)
M. van Weerelt, W. C. Pfeiffer & M. Fiszman Institute of Biophysics, Federal University of Rio de Janeiro (UFRJ),
Rio de Janeiro, Brazil (Received: 8 September, 1983)
ABSTRACT Barnacles (Balanus sp) were used to examine the uptake and release of chromium-51 added to sea water in two different valence states, 51Cr(I'l) and 5t Cr(lll). Hexavalent chromium-51 (sodium chromate)forms a true ionic solution in filtered sea water and barnacles were able to accumulate chromium in soft tissues 543 times the levels found in sea water. The experiment showed that incorporated Cr(VI), is released to the water in such way that only 20 % of maximum uptake was lost by the organisms after 26 days. Addition of the hexavalent form to non filtered sea water showed that 2 % of the total radioactivity was attached to the suspended particles. Here again chromium is mainly concentrated in soft tissues, showing a concentration factor of 380 related to total chromium available in aquarium (solution + suspended particles). From the total radioactivity incorporated by the organisms, 20 °/o was released after 56 days in the clearance experiment. Chromium, as trivalent chromic chloride, when added to sea water precipitates and is quickly removedfrom the water by thefilter activity of the barnacles. Unlike the hexavalent form, trivalent chromium is not concentrated in soft tissues of the barnacles and is quickly released to the water through the organisms digestive system. 201 Marine Environ. Res. 0141-1136/84/$03.00 ~ Elsevier Applied Science Publishers Ltd, England, 1984. Printed in Great Britain
"~_0,. "~
M, ran Weerelt, W. C. PJeiffer, M. Fiszman
N ~ ~'a~~l|~
AIRPORTOF
GUANABARA BAY
RIO DEJANI:'IRO
+!!!,~+l, +I,~+~,,+~L+, , + ++ J,,..... '
Fig. 1.
I + ~
1
:
Geographical localization of the studied area. C P = collecting points.
Uptake and release of chromium-51 by barnacles
203
INTRODUCTION Guanabara Bay on the south-east coast of Rio de Janeiro State receives industrial waste effluents from 4000 industries in the municipal area of the city of Rio de Janeiro (Hydroscience, Inc., 1977). Iraj/L River one of the Bay's tributaries receives high concentrations of chromium mainly in its hexavalent form, released through the effluents from an electroplating industry without any treatment. The industrial discharge into the river takes place only 2 km upstream of its outfall into the Bay (Fig. 1). Chromium, transported through the river mainly linked to suspended particles, reaches Guanabara Bay and can be concentrated by biological compartments (Pfeiffer et al., 1980; Pfeiffer et al., 1982). Indeed, inside Guanabara Bay, barnacles (Balanus sp) proved to be an effective biological monitor as they concentrate chromium in soft tissues 103 times the levels of chromium found in suspended particles (van Weerelt, 1982). The present paper produces data of laboratory experiments related to the uptake and release of hexavalent 5tCr and trivalent s ~Cr by barnacles (Balanus sp) collected in Guanabara Bay. Our objectives are to clear up whether this chromium accumulation by barnacles is a mechanical or a biological process and to find out the importance of the chemical form of the metal on the metabolic behaviour of this filter feeder organism.
MATERIAL AND METHODS The barnacles were collected in the estuary, transported in ice boxes to the laboratory in local sea water, washed, weighed and kept alive until the beginning of the experiments. Four different sets of experiments were performed: uptake and release of sodium chromate-51 in the absence and presence of suspended particles; uptake and release of chromic chloride in the absence and presence of suspended particles. All experiments were carried out in an aerated 3 litre aquarium using local sea water. In the experiments free of suspended particles, sea water was filtered through 0-45/am Millipore membranes prior to use. In the experiments in the presence of suspended particles, after addition of the radioactive tracer, an equilibrium was allowed to be reached between the chromium in the water and the chromium retained by the suspended particles before introducing the barnacles into the aquarium. This
204
M. van Weereh, I4I. C. Pfeiffer, M. Fiszman
equilibrium was achieved in seven days for the hexavalent form and in 24 h for the trivalent form. All radiometric measurements of 5ICr were performed in a Harshaw NaI(T1) 2in x 2in well crystal coupled to a Monochannel Analyzer Spectromatic Tracerlab with a window of 0.06 MeV centred around the 0.32 MeV photopeak of 5ICr. All necessary adjustments were performed to keep measurement parameters uniform, such as self-absorption, geometry, counting efficiency, gain shifts and reproducibility. Hexavalent chromium-51
The addition of sodium chromate-51 to filtered sea water resulted in a true ionic solution in which there were virtually no radioactive particles. Eight barnacles were then immersed in the aquarium. During the uptake experiments, 1 ml of the solution and all the organisms were removed from the aquarium and radiometrically measured, from time to time, over a period of 27 days when an apparent equilibrium was reached. At this time half of the total barnacle population was removed from the aquarium, sorted out into soft tissues and shells, and used for the determination of the concentration factor (CF) defined as: CF - c p m ] g tissue dry weight cpm/ml water The rest of the barnacles were transferred to an aquarium free of the radiotracer in order to perform clearance experiments. The release of chromium was followed up over a period of 25 days using the abovedescribed radiometric method, until a new equilibrium was reached. In the same way the organisms were then removed from the aquarium, separated into soft tissues and shells, and their radioactivity measured. The uptake and release experiments carried out with sea water containing suspended particles followed the same method described above with the difference that the observation period was about 120 days. Trivalent chromium-51
In the two sets of experiments either free or with suspended particulate matter, 90 ~ of the radiotracer was in the particulate form 24 h after addition of the chromic-51 chloride. The same number of barnacles as above were immersed in the aquarium one day after addition of
Uptake and release of chromium-51 by barnacles
205
radioactive chromic chloride. During the uptake and release experiments, samples of water (1-3ml) and the organisms were radiometrically measured over a period of 60 days. The release of chromium was followed up in the same aquarium since the radioactive levels in the water decreased sharply as a result of the filtering activity of the barnacles.
RESULTS AND DISCUSSION Hexavalent chromium-51 The uptake and release curve of hexavalent chromium as chromate in a true solution is shown in Fig. 2. Results of concentration factor and distribution of radioactivity in i06
104
"~0"~--_0_0_ 0 ! iO s
.~ O~ 0 ~
O 0 ~ •"O "---.O.,e_O........~
103
°~ ° O
E E rs.
Z E (J
TRANSFERENCE TO A NON RADIOACTIVEACUARIUM
I0 4
t0 2
• BARNACLES O WATER
i
I
qO
I
I
20
I
i
30
I
t
40
I
!
50
!
60
TIME (doys)
Fig. 2.
Uptake and release of S,Cr(Vi) in the absence of suspended particulate matter.
M. ran Weerelt, W. C. Pfeiffer, M. Fiszman
206
TABLE 1
Concentration Factor and Distribution of Hexavalent 5~Cr by Barnacles(Balanussp) in the Absence of Suspended Particulate Matter (N= 3) Concentration factor Soft tissues after reaching equilibrium (26 days)
Percentage of release Whole organisms (26 days)
Biological half-life Whole organisms (days)
~X+_~)
(X +~)
fx)
543 + 168
21 + 1
70
Distribution of 5~Cr(VI)
Soft tissues, cpm/g (.~'_+ a) Shells, cpm/g (,~'_ a)
Uptake (26 days)
Release (25 days)
233 293 _+ 72 311
134 048 _+96 134
40 680 _+ 2 129
37 876 _+ 14 625
barnacles are shown in Table 1. In the first days there was a fast entry of 51Cr reaching an apparent equilibrium after 26 days. The organism showed a selective accumulation of s 1Cr in soft tissues six and three times higher than in the shells. The radioactive levels of soft tissues after 26 days were 543 times higher than the levels found in sea water. It can be observed in Fig. 2 that the release rate of chromium by barnacles into sea water follows an exponential process and after 26 days only 2 0 ~ from the total 5~Cr incorporated was removed from the organisms. The biological half-life for 51Cr in Balanus sp. under the experimental conditions was 70 days. In the experiment with hexavalent chromium-51 in sea water in the presence of 0.05 mg/ml of suspended particles the retention of 5~Cr by the suspended matter was only 2 ~o from the total added to the aquarium. The retention capacity of this sediment for 5~Cr was tested in a parallel experiment showing a maximum release of 30 ~o from the particles after 43 days (van Weerelt, 1982). In this experiment the organisms were only immersed in the aquarium 7 days after the addition of the radiotracer as reported before. The uptake and release curve of hexavalent chromium51 is shown in Fig. 3. The uptake is quite fast like in the previous experiment and one can observe a maximum intake in about 15 days
Uptake and release of chromium-51 by barnacles 106
104
iOs
10 3
207
A
o
E
E
t-i
EX U
-IPTRANSFERENCE TO A NON RADIOACTIVE AQUARIUM
104
i0 z
• BARNACLES O WArER PLUS SUSPENDED PARTICULATE MATTER
1
0
Fig. 3.
I
20
I
I
40
I
I
I
I
60 80 TIME(days)
I
I
tOO
I
120
Uptake and release of s tCr(Vi) in the presence of suspended particulate matter.
followed by a decrease in the radioactive levels of the organisms. This accumulation maximum is coincident with the complete removal of the radioactive particles from the aquarium as a result of filtration by the barnacles. An equilibrium was not observed in this experiment probably due to the lack of data between day 22 and day 61 of experiment; at this point half of the barnacles were removed for radioactivity measurements. From Table 2 one can see an effective accumulation of 5iCr in the soft tissues rather than in shells with a concentration factor of 380 compared to sea water. The levels of hexavalent 5ICr in soft tissues were 8 and 3 times higher than the levels found in shells. Although an equilibrium was not achieved in the experiment, the curve in the releasing part presents the same shape as that obtained for dissolved 51Cr. As before (Table 1) the losses of radioactivity observed from the barnacles (Table 2) after 60 days were 21 ~ of the maximum uptake of S~Cr by the organisms with a biological half-life of 180 days.
M. van Weerelt, W. C. Pfeiffer, M. Fiszman
208
TABLE 2 Concentration Factor and Distribution of Hexavalent 5iCr by Barnacles (Balanus sp) in the Presence of Suspended Particulate Matter (N = 3)
Concentration factor Soft tissues after reaching equilibrium (61 days) ~A + a) 383-t-221
Percentageof release Whole organisms (56 days)
Biologicalhalf-life Whole organisms (days)
('X + a)
CX)
21 __ 11
180
Distribution of 5~Cr(VI)
Soft tissues, cpm/g (~'-I- a) Shells, cpm/g (~" + a)
Uptake (61 days)
Release (56 days)
252 277 __+51 510
199 299 ___146 337
32 853 + 5 874
32 236 + 3 128
i n conclusion it appears that hexavalent chromium is biologically available to barnacles and is mainly accumulated by their soft tissues. This uptake of chromium can occur straight from the sea water or from particulate matter available in the water. As the barnacles were able to accumulate hexavalent chromium in soft tissues about 400 times the levels added to sea water presenting a mean biological half-life of 120 days this organism seems to be a good biological monitor for hexavalent chromium discharged into the environment. Similar results were found for Balanus amphitrite (Barbaro et al., 1978) and for marine fishes (Sherwood & Wright, 1976). Trivalent chromium-51
The results of uptake and release experiments of trivalent 51Cr arc presented in Fig. 4. It can be seen that barnacles present a maximum uptake after 15-20 days but do not reach an equilibrium. This maximum uptake is coincident with the complete removal of the radioactive particles from the aquarium as a result of the filtering activity of the barnacles. The curve shows a minimum and a consecutive new maximum of 5iCr
Uptake and release of chromium-51 by barnacles
209
IO 3
'°6 F o/o
/'\ O
E
IO 2
I°5
O.
E
•
¢J
°
I
. BAR.ACLES
i
o WATERPLO OSE,OO PARTICULATE MATTER
t
o,
\ 0"---0--~ % 0~----0
104 I
Fig. 4.
! I0
I 20
I I I 30 40 50 TIME (days)
I 60
I 70
80
Uptake and release of 5tCr(III).
in the barnacles probably due to a release and a new uptake of the radioactive particles. After sixty days the major radioactivity is concentrated in barnacle detritus which remained on the bottom of the aquarium. This kind of curve suggests that the trivalent 51Cr chloride which precipitated as fine particles after addition to the sea water remains in suspension and passes through the barnacles digestive system without absorption into the soft tissues. Similar results were found by Sherwood for marine fishes, Chipman for the bivalve Tapes decussatus and Barbaro for Balanus amphitrite (Sherwood & Wright, 1976; Chipman, 1966; Barbaro et al., 1978). This hypothesis is confirmed by the fact that when these barnacles are transferred to aquarium without radioactivity, 82 ~ of the 51Cr incorporated in the first maximum uptake is released by the organism after 50 days (Van Weerelt, 1982). Since trivalent chromium-51 in sea water precipitates and remains as
210
M. t,an Weerelt, W. C. Pfeiffer, M. Fis-.man
suspended particles, no differences were observed between the experiments in the absence and presence of natural suspended matter. Therefore for trivalent chromium, Balanus sp only can be considered as an instantaneous indicator of large chromium releases into the environment.
CONCLUSIONS Based on the experimental results one can conclude that barnacles (Balanus sp) incorporate hexavalent chromium-51 in soft tissues with a concentration factor up to 10 3 and release the metal with an average biological half-life of 120 days. Therefore they can be considered as biological monitors for hexavalent chromium. Trivalent chromium-51 which precipitates in sea water and remains in suspension is quickly removed from the solution by the barnacles due to their filter feeding habit. The radionuclide is not accumulated in the soft tissues of the barnacles and passes through the digestive system of the organisms.
ACKNOWLEDGEMENTS The authors wish to thank Wanderley R. Bastos for his invaluable work, performing all atomic absorption analyses, F E E M A (State Environmental Pollution Control Agency) for technical assistance and Zelia de Freitas for typing. The work was sponsored by the Brazilian Atomic Energy Commission, F I N E P Contract B 76/79/074/0000/00, C N P q and the Federal University of Rio de Janeiro.
REFERENCES Barbaro, A., Francescon, A., Polo, B. & Bilio, M. (1978). Balanus amphitrite (Cirripedia: Toraxica)---A potential indicator of fluoride, copper, lead, chromium and mercury in North Adriatic Lagoons. Marine Biology, 46, 247-57. Chipman, W. A. (1966). Uptake and accumulation of chromium-51 by the clam Tapes decussatus, in relation to physical and chemical form. Disposal of radioactive waste into seas, oceans and surface waters. Proceedings of a Symposium, 16-20 May. IAEA, Vienna.
Uptake and release of chromium-51 by barnacles
211
Hydroscience, Inc., New Jersey, USA (1977). Environmental control programme in the State of Rio de Janeiro, Brazil--Water quality model of Guanabara Bay. Technical Report prepared for the World Health Organization, BRA73/003. Pfeiffer, W. C., Fiszman, M. & Carbonell, N. (1980). Fate of chromium in a tributary of the Iraj~ River, Rio de Janeiro. Environ. Pollut. (Series B), 1, 117-26. Pfeiffer, W. C., Fiszman, M., Drude de Lacerda, L., van Weerelt, M. & Carbonell, N. (1982). Chromium in water, suspended particles, sediments and biota in the Iraj~i River Estuary. Environ. Pollut. (Series B) (accepted for publication). Sherwood, M. J. & Wright, J. L. (1976). Uptake and effects of chromium on marine fish. Annual Report, Coastal Water Research Project. Southern California Coastal Water Research Project, El Segundo, California, pp. 123-8. van Weerelt, M. (1982). Niveis de cr6mo no estu~rio do Rio Irajfi (Baia da Guanabara) e incorporaq,~o ~xperimental de s 1Cr em cracas (Balanus sp). MSC Thesis, Institute of Biophysics, Federal University of Rio de Janeiro (UFRJ).
Uptake and Release of 51 Cr(VI) and 51 Cr(llI) by Barnacles (Balanus sp)
M. van Weerelt, W. C. Pfeiffer & M. Fiszman Institute of Biophysics, Federal University of Rio de Janeiro (UFRJ),
Rio de Janeiro, Brazil (Received: 8 September, 1983)
ABSTRACT Barnacles (Balanus sp) were used to examine the uptake and release of chromium-51 added to sea water in two different valence states, 51Cr(I'l) and 5t Cr(lll). Hexavalent chromium-51 (sodium chromate)forms a true ionic solution in filtered sea water and barnacles were able to accumulate chromium in soft tissues 543 times the levels found in sea water. The experiment showed that incorporated Cr(VI), is released to the water in such way that only 20 % of maximum uptake was lost by the organisms after 26 days. Addition of the hexavalent form to non filtered sea water showed that 2 % of the total radioactivity was attached to the suspended particles. Here again chromium is mainly concentrated in soft tissues, showing a concentration factor of 380 related to total chromium available in aquarium (solution + suspended particles). From the total radioactivity incorporated by the organisms, 20 °/o was released after 56 days in the clearance experiment. Chromium, as trivalent chromic chloride, when added to sea water precipitates and is quickly removedfrom the water by thefilter activity of the barnacles. Unlike the hexavalent form, trivalent chromium is not concentrated in soft tissues of the barnacles and is quickly released to the water through the organisms digestive system. 201 Marine Environ. Res. 0141-1136/84/$03.00 ~ Elsevier Applied Science Publishers Ltd, England, 1984. Printed in Great Britain
"~_0,. "~
M, ran Weerelt, W. C. PJeiffer, M. Fiszman
N ~ ~'a~~l|~
AIRPORTOF
GUANABARA BAY
RIO DEJANI:'IRO
+!!!,~+l, +I,~+~,,+~L+, , + ++ J,,..... '
Fig. 1.
I + ~
1
:
Geographical localization of the studied area. C P = collecting points.
Uptake and release of chromium-51 by barnacles
203
INTRODUCTION Guanabara Bay on the south-east coast of Rio de Janeiro State receives industrial waste effluents from 4000 industries in the municipal area of the city of Rio de Janeiro (Hydroscience, Inc., 1977). Iraj/L River one of the Bay's tributaries receives high concentrations of chromium mainly in its hexavalent form, released through the effluents from an electroplating industry without any treatment. The industrial discharge into the river takes place only 2 km upstream of its outfall into the Bay (Fig. 1). Chromium, transported through the river mainly linked to suspended particles, reaches Guanabara Bay and can be concentrated by biological compartments (Pfeiffer et al., 1980; Pfeiffer et al., 1982). Indeed, inside Guanabara Bay, barnacles (Balanus sp) proved to be an effective biological monitor as they concentrate chromium in soft tissues 103 times the levels of chromium found in suspended particles (van Weerelt, 1982). The present paper produces data of laboratory experiments related to the uptake and release of hexavalent 5tCr and trivalent s ~Cr by barnacles (Balanus sp) collected in Guanabara Bay. Our objectives are to clear up whether this chromium accumulation by barnacles is a mechanical or a biological process and to find out the importance of the chemical form of the metal on the metabolic behaviour of this filter feeder organism.
MATERIAL AND METHODS The barnacles were collected in the estuary, transported in ice boxes to the laboratory in local sea water, washed, weighed and kept alive until the beginning of the experiments. Four different sets of experiments were performed: uptake and release of sodium chromate-51 in the absence and presence of suspended particles; uptake and release of chromic chloride in the absence and presence of suspended particles. All experiments were carried out in an aerated 3 litre aquarium using local sea water. In the experiments free of suspended particles, sea water was filtered through 0-45/am Millipore membranes prior to use. In the experiments in the presence of suspended particles, after addition of the radioactive tracer, an equilibrium was allowed to be reached between the chromium in the water and the chromium retained by the suspended particles before introducing the barnacles into the aquarium. This
204
M. van Weereh, I4I. C. Pfeiffer, M. Fiszman
equilibrium was achieved in seven days for the hexavalent form and in 24 h for the trivalent form. All radiometric measurements of 5ICr were performed in a Harshaw NaI(T1) 2in x 2in well crystal coupled to a Monochannel Analyzer Spectromatic Tracerlab with a window of 0.06 MeV centred around the 0.32 MeV photopeak of 5ICr. All necessary adjustments were performed to keep measurement parameters uniform, such as self-absorption, geometry, counting efficiency, gain shifts and reproducibility. Hexavalent chromium-51
The addition of sodium chromate-51 to filtered sea water resulted in a true ionic solution in which there were virtually no radioactive particles. Eight barnacles were then immersed in the aquarium. During the uptake experiments, 1 ml of the solution and all the organisms were removed from the aquarium and radiometrically measured, from time to time, over a period of 27 days when an apparent equilibrium was reached. At this time half of the total barnacle population was removed from the aquarium, sorted out into soft tissues and shells, and used for the determination of the concentration factor (CF) defined as: CF - c p m ] g tissue dry weight cpm/ml water The rest of the barnacles were transferred to an aquarium free of the radiotracer in order to perform clearance experiments. The release of chromium was followed up over a period of 25 days using the abovedescribed radiometric method, until a new equilibrium was reached. In the same way the organisms were then removed from the aquarium, separated into soft tissues and shells, and their radioactivity measured. The uptake and release experiments carried out with sea water containing suspended particles followed the same method described above with the difference that the observation period was about 120 days. Trivalent chromium-51
In the two sets of experiments either free or with suspended particulate matter, 90 ~ of the radiotracer was in the particulate form 24 h after addition of the chromic-51 chloride. The same number of barnacles as above were immersed in the aquarium one day after addition of
Uptake and release of chromium-51 by barnacles
205
radioactive chromic chloride. During the uptake and release experiments, samples of water (1-3ml) and the organisms were radiometrically measured over a period of 60 days. The release of chromium was followed up in the same aquarium since the radioactive levels in the water decreased sharply as a result of the filtering activity of the barnacles.
RESULTS AND DISCUSSION Hexavalent chromium-51 The uptake and release curve of hexavalent chromium as chromate in a true solution is shown in Fig. 2. Results of concentration factor and distribution of radioactivity in i06
104
"~0"~--_0_0_ 0 ! iO s
.~ O~ 0 ~
O 0 ~ •"O "---.O.,e_O........~
103
°~ ° O
E E rs.
Z E (J
TRANSFERENCE TO A NON RADIOACTIVEACUARIUM
I0 4
t0 2
• BARNACLES O WATER
i
I
qO
I
I
20
I
i
30
I
t
40
I
!
50
!
60
TIME (doys)
Fig. 2.
Uptake and release of S,Cr(Vi) in the absence of suspended particulate matter.
M. ran Weerelt, W. C. Pfeiffer, M. Fiszman
206
TABLE 1
Concentration Factor and Distribution of Hexavalent 5~Cr by Barnacles(Balanussp) in the Absence of Suspended Particulate Matter (N= 3) Concentration factor Soft tissues after reaching equilibrium (26 days)
Percentage of release Whole organisms (26 days)
Biological half-life Whole organisms (days)
~X+_~)
(X +~)
fx)
543 + 168
21 + 1
70
Distribution of 5~Cr(VI)
Soft tissues, cpm/g (.~'_+ a) Shells, cpm/g (,~'_ a)
Uptake (26 days)
Release (25 days)
233 293 _+ 72 311
134 048 _+96 134
40 680 _+ 2 129
37 876 _+ 14 625
barnacles are shown in Table 1. In the first days there was a fast entry of 51Cr reaching an apparent equilibrium after 26 days. The organism showed a selective accumulation of s 1Cr in soft tissues six and three times higher than in the shells. The radioactive levels of soft tissues after 26 days were 543 times higher than the levels found in sea water. It can be observed in Fig. 2 that the release rate of chromium by barnacles into sea water follows an exponential process and after 26 days only 2 0 ~ from the total 5~Cr incorporated was removed from the organisms. The biological half-life for 51Cr in Balanus sp. under the experimental conditions was 70 days. In the experiment with hexavalent chromium-51 in sea water in the presence of 0.05 mg/ml of suspended particles the retention of 5~Cr by the suspended matter was only 2 ~o from the total added to the aquarium. The retention capacity of this sediment for 5~Cr was tested in a parallel experiment showing a maximum release of 30 ~o from the particles after 43 days (van Weerelt, 1982). In this experiment the organisms were only immersed in the aquarium 7 days after the addition of the radiotracer as reported before. The uptake and release curve of hexavalent chromium51 is shown in Fig. 3. The uptake is quite fast like in the previous experiment and one can observe a maximum intake in about 15 days
Uptake and release of chromium-51 by barnacles 106
104
iOs
10 3
207
A
o
E
E
t-i
EX U
-IPTRANSFERENCE TO A NON RADIOACTIVE AQUARIUM
104
i0 z
• BARNACLES O WArER PLUS SUSPENDED PARTICULATE MATTER
1
0
Fig. 3.
I
20
I
I
40
I
I
I
I
60 80 TIME(days)
I
I
tOO
I
120
Uptake and release of s tCr(Vi) in the presence of suspended particulate matter.
followed by a decrease in the radioactive levels of the organisms. This accumulation maximum is coincident with the complete removal of the radioactive particles from the aquarium as a result of filtration by the barnacles. An equilibrium was not observed in this experiment probably due to the lack of data between day 22 and day 61 of experiment; at this point half of the barnacles were removed for radioactivity measurements. From Table 2 one can see an effective accumulation of 5iCr in the soft tissues rather than in shells with a concentration factor of 380 compared to sea water. The levels of hexavalent 5ICr in soft tissues were 8 and 3 times higher than the levels found in shells. Although an equilibrium was not achieved in the experiment, the curve in the releasing part presents the same shape as that obtained for dissolved 51Cr. As before (Table 1) the losses of radioactivity observed from the barnacles (Table 2) after 60 days were 21 ~ of the maximum uptake of S~Cr by the organisms with a biological half-life of 180 days.
M. van Weerelt, W. C. Pfeiffer, M. Fiszman
208
TABLE 2 Concentration Factor and Distribution of Hexavalent 5iCr by Barnacles (Balanus sp) in the Presence of Suspended Particulate Matter (N = 3)
Concentration factor Soft tissues after reaching equilibrium (61 days) ~A + a) 383-t-221
Percentageof release Whole organisms (56 days)
Biologicalhalf-life Whole organisms (days)
('X + a)
CX)
21 __ 11
180
Distribution of 5~Cr(VI)
Soft tissues, cpm/g (~'-I- a) Shells, cpm/g (~" + a)
Uptake (61 days)
Release (56 days)
252 277 __+51 510
199 299 ___146 337
32 853 + 5 874
32 236 + 3 128
i n conclusion it appears that hexavalent chromium is biologically available to barnacles and is mainly accumulated by their soft tissues. This uptake of chromium can occur straight from the sea water or from particulate matter available in the water. As the barnacles were able to accumulate hexavalent chromium in soft tissues about 400 times the levels added to sea water presenting a mean biological half-life of 120 days this organism seems to be a good biological monitor for hexavalent chromium discharged into the environment. Similar results were found for Balanus amphitrite (Barbaro et al., 1978) and for marine fishes (Sherwood & Wright, 1976). Trivalent chromium-51
The results of uptake and release experiments of trivalent 51Cr arc presented in Fig. 4. It can be seen that barnacles present a maximum uptake after 15-20 days but do not reach an equilibrium. This maximum uptake is coincident with the complete removal of the radioactive particles from the aquarium as a result of the filtering activity of the barnacles. The curve shows a minimum and a consecutive new maximum of 5iCr
Uptake and release of chromium-51 by barnacles
209
IO 3
'°6 F o/o
/'\ O
E
IO 2
I°5
O.
E
•
¢J
°
I
. BAR.ACLES
i
o WATERPLO OSE,OO PARTICULATE MATTER
t
o,
\ 0"---0--~ % 0~----0
104 I
Fig. 4.
! I0
I 20
I I I 30 40 50 TIME (days)
I 60
I 70
80
Uptake and release of 5tCr(III).
in the barnacles probably due to a release and a new uptake of the radioactive particles. After sixty days the major radioactivity is concentrated in barnacle detritus which remained on the bottom of the aquarium. This kind of curve suggests that the trivalent 51Cr chloride which precipitated as fine particles after addition to the sea water remains in suspension and passes through the barnacles digestive system without absorption into the soft tissues. Similar results were found by Sherwood for marine fishes, Chipman for the bivalve Tapes decussatus and Barbaro for Balanus amphitrite (Sherwood & Wright, 1976; Chipman, 1966; Barbaro et al., 1978). This hypothesis is confirmed by the fact that when these barnacles are transferred to aquarium without radioactivity, 82 ~ of the 51Cr incorporated in the first maximum uptake is released by the organism after 50 days (Van Weerelt, 1982). Since trivalent chromium-51 in sea water precipitates and remains as
210
M. t,an Weerelt, W. C. Pfeiffer, M. Fis-.man
suspended particles, no differences were observed between the experiments in the absence and presence of natural suspended matter. Therefore for trivalent chromium, Balanus sp only can be considered as an instantaneous indicator of large chromium releases into the environment.
CONCLUSIONS Based on the experimental results one can conclude that barnacles (Balanus sp) incorporate hexavalent chromium-51 in soft tissues with a concentration factor up to 10 3 and release the metal with an average biological half-life of 120 days. Therefore they can be considered as biological monitors for hexavalent chromium. Trivalent chromium-51 which precipitates in sea water and remains in suspension is quickly removed from the solution by the barnacles due to their filter feeding habit. The radionuclide is not accumulated in the soft tissues of the barnacles and passes through the digestive system of the organisms.
ACKNOWLEDGEMENTS The authors wish to thank Wanderley R. Bastos for his invaluable work, performing all atomic absorption analyses, F E E M A (State Environmental Pollution Control Agency) for technical assistance and Zelia de Freitas for typing. The work was sponsored by the Brazilian Atomic Energy Commission, F I N E P Contract B 76/79/074/0000/00, C N P q and the Federal University of Rio de Janeiro.
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