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Accumulation of Cu, Zn, Cd, and Pb by aquatic macrophytes
Environment International, Vol. 11, pp. 77-87, 1985 Printed in the USA. All rights reserved.
0160-4120/85 $3.00 + .00 Copyright © 1985 Pergamon Press Ltd.
ACCUMULATION OF Cu, Zn, Cd, AND Pb BY AQUATIC MACROPHYTES Sami E. Fayed and Hussein I. Abd-EI-Shafy National Research Centre, Dokki, Cairo, Egypt (Received 11 June 1984; Accepted 12 November 1984) The levels of Cu, Zn, Cd, and Pb were determined in water, sediment, and aquatic plant samples taken from the Nile River and its branches at selected sites characterized by heavy industrialization and dense population. The results revealed that concentration factors in the sediments were, in most cases, much higher than in plants. Metals content in the plants collected from downstream wastewater discharge points was usually higher than that in the plants collected from sites upstream of these points. In laboratory scale models of the piston and completely mixed continuous flow hydraulic systems, Cu, Cd, and Pb removal by a test plant (Eichhornia crassipes) was assessed. The results showed that the root of the test plant acted as a scavenger for the metals up to a certain capacity. The metals were taken up by different rates, the least of them was that of cadmium. In a batch system metals accumulation from waters of different compositions was investigated using the same test plant. The results are summarized in the following: (1) Cu, Zn, Cd, or Pb accumulation was a function of metal:plant root exposure ratio on dry weight basis. (2) The rates of metals accumulation from both the natural medium (Nile water) and the synthetic medium (mM NaI-ICO3 solution) were quite close. (3) Metal accumulation was much lower in the presence of EDTA. (4) The presence of Ca 2÷and Mg2÷in a concentration equivalent to that of EDTA did not eliminate the retarding effect of the latter on metal accumulation. (5) Metal translocation from the root to the shoot occurred at a low rate compared to metal accumulation by the root.
Introduction
M a t e r i a l s and M e t h o d s
S u r f a c e w a t e r p o l l u t i o n b y h e a v y m e t a l s results m a i n l y from wastewater discharge into water bodies and from l a n d r u n o f f ( W i l s o n , 1976; C o o k , 1977; R i c h e r t et al., 1977). T h e p h e n o m e n o n o f p o l l u t a n t c o n c e n t r a t i o n b y a q u a t i c p l a n t s has b e e n n o t i c e d in p o n d s c r e a t e d f o r the d u m p i n g o f w a s t e w a t e r effluents, w h e r e these p l a n t s flourish on behalf of nutrient content of water ( E n g l a n d e , 1980; W o l v e r t o n , 1975; W o l v e r t o n a n d M c D o n a l d , 1975, 1976). T h e r e has b e e n a n e m p h a s i s o n c o n v e r t i n g a q u a t i c weeds i n t o a useful r e s o u r c e , f o r exa m p l e , as a n i m a l feed, as fertilizer, o r f o r energy p r o d u c t i o n ( N A S , 1976; W o l v e r t o n , 1975). I n f o r m a t i o n o n m e t a l a c c u m u l a t i o n b y a q u a t i c p l a n t s m a y be r e q u i r e d for aquatic weed management. A field i n v e s t i g a t i o n was c o n d u c t e d in o r d e r to assess the i m p a c t o f i n d u s t r i a l activities o n the levels o f h e a v y m e t a l s in the a d j a c e n t a q u a t i c e c o s y s t e m . In a d d i t i o n , the a f f i n i t y o f E i c h h o r n i a crassipes, to m e t a l a c c u m u l a tion was e x a m i n e d in l a b o r a t o r y scale m o d e l s o f the p i s t o n a n d c o m p l e t e l y m i x e d c o n t i n u o u s flow systems. In a b a t c h system, m e t a l a c c u m u l a t i o n u n d e r d i f f e r e n t c h e m i c a l c o n d i t i o n s was also i n v e s t i g a t e d .
Field Investigation C o m p o s i t e s a m p l e s were t a k e n r a n d o m l y f r o m each o f six selected sites along the Nile River. The sites started f r o m the H i g h D a m lake, went d o w n s t r e a m to the R a s h i d b r a n c h o f the river, a n d c o n t i n u e d to the end o f a c a n a l e m e r g i n g f r o m the R a s h i d b r a n c h . A b a c k g r o u n d p l a n t s a m p l e was collected f r o m the l a k e (Site N o . 1), far f r o m u p s t r e a m a n y i n d u s t r i a l activities. A b o u t 500 mi d o w n s t r e a m f r o m the d a m , p l a n t , s e d i m e n t , a n d w a t e r s a m p l e s were t a k e n f r o m the river at site N o . 2, w h e r e i r o n a n d steel, a n d c o k e industries are located. Site N o . 3 was selected 150 mi farther d o w n s t r e a m o n the R a s h i d b r a n c h o f t h e river, w h e r e factories p r o d u c i n g pesticides, p h o s p h a t e fertilizers, a n d s o a p a n d s o d a a r e l o c a t e d . S a m p l e s t a k e n . a t sites N o . 2 a n d 3 were t a k e n b o t h u p s t r e a m a n d d o w n s t r e a m f r o m the w a s t e w a t e r d i s c h a r g e p o i n t . T h e h e a v i l y p o p u l a t e d C a i r o District is l o c a t e d b e t w e e n sites N o . 2 a n d 3. P l a n t s a m p l e s were t a k e n f r o m t h e river in the C a i r o District, site N o . 4. S a m p l i n g site N o . 5 was selected a b o u t m i d w a y in a c a n a l e m e r g i n g f r o m the R a s h i d b r a n c h o f the river. This site is 160 mi d o w n s t r e a m f r o m site N o . 3 77
78
Sami E. Fayed & Hussein I. Abd-E1-Shafy
and located in the Alexandria District, which contains various industries. In addition, plant samples were collected at the end of this canal from a location called Site No. 6. The samples were dried at 105 °C, weighed, and then digested by a mixture of HNO3 and H202 under flux for the determination of Cu, Zn, Cd, and Pb concentrations.
Accumulation o f Cu, Cd, and Pb by E. crassipes in a Piston Flow System Eichhornia crassipes (the test plant) was obtained from a manmade pond, where this plant is maintained among some of the aquatic ornamental plants in a botanical garden. A laboratory scale gutter made of plexiglass (5 m long, 25 cm wide, and 30 cm deep) was filled with 250 L filtered Nile water. The chemical characteristics of this water (Table 1) were determined according to Standard Methods (APHA, 1975). Fifty of the test plants were introduced into the gutter. The plants were exposed to illumination (about 4000 lux) for 14 h daily using cool white flourescent tubes and tungsten lamps. A continuous flow of filtered Nile water was secured into the gutter using a peristaltic dosing pump at a rate ranging between 12 to 13 L per day for a period of 15 days. Then, equimolar solutions of each of Cd (as CdCI2), Cu (as CuSO4) and Pb (as Pb(NO3)2) were added to the feed water at a rate of 0.5 #M/L for each metal for 9 days. This concentration was later raised to 1 /zM/L. The gutter was externally marked into four zones. Water samples (50 mL) were withdrawn and plant samples were picked up from the different zones at the times indicated in the corresponding table. The samples were subjected to analysis for determination of metals concentration. Accumulation o f Cu, Cd, and Pb by E. crassipes in a continuous f l o w completely mixed system This experiment was carried out in a plexiglass dish with 40 L capacity and 30 cm depth. The dish was filled with filtered Nile water, and Eichhornia crassipes plants were introduced into it. The plants were exposed to illumination as that used in the previous experiment. The dish was continuously supplied with the water at a
Table 1. Chemical characteristics of Nile water used in this study (average). Electric conductance ~ m h o cm -1) pH Total hardness, as CaCO3 Total alkalinity, as CaCO3 Chlorides, as C1Sulfates, as SO7 Total phosphorus, as P Ortho phosphate, as P Nitrate, as N
320 7.8-8.2 102 mg/L 112 mg/L 18 mg/L 16 mg/L 0.098 mg/L 0.051 mg/L 0.054 mg/L
rate of 6.0-6.2 L per day using a peristaltic dosing pump. A stainless steel stirrer kept the water of the dish continuously mixed. After two weeks, equimolar solutions of Cd, Cu, and Pb were added at a rate of 0.5 #M/ L of each metal in the feed water for 6 days. This concentration was later raised to 1 /zM/L. Water samples (50 mL) were withdrawn from both the feed tank and the experimental dish. After 11 days of metal addition to the feed water, plant samples were picked up at the times indicated in corresponding table. Metals concentration was then determined in the water and plant samples.
Cu, Cd, Zn, and Pb Accumulation by E. crassipes under different chemical conditions in a Batch System Effect o f Metal:Plant exposure ratio on metal accumulation. In this experiment, metal accumulation from filtered Nile water and from mM NaHCO3 solution by E. crassipes was assessed. First, 1.5-L portions of the test water were introduced into each of 2-L capacity plastic jars. Then copper, zinc, or cadmium was added to the test water at concentrations of 0.0, 1.0, 2.5, and l0 mg/L, while lead was added at 0.0, 1.0, 5.0, and 30 mg/L. The test plants were introduced into the jars and exposed to continuous illumination. After 1 day exposure, the plants were removed and dried for determination of metal concentration. Accumulation o f Cu, Zn, Cd, and Pb in combination from NaHC03 solution. First, 1.5-L portions of mM NaHCO3 solution were introduced into 2-L capacity plastic jars. Then aliquots of Cu, Zn, Cd, and Pb solutions were added to each of these jars to obtain equimolar concentrations of these metals. These concentrations were 2, 4, 8, and 16 #M/L. E. crassipes plants were introduced into the jars and exposed to continuous illumination. After 1 day exposure, these plants were removed and dried for determination of metals concentration. Effect o f some chemical characteristics o f water on Cd and Pb accumulations. Aliquots of cadmium and lead solutions were added separately to 1.5 L of each of the following test solutions contained in 2-L plastic jars. The concentration of the test metal was one mg/L. Test No. 1.
m M / L NaHCO3 solution
Test No. 2.
solution of 1 m M / L NaHCO3 + 0.2 m M / L Ca(as CaCI,) + 0.2 m M / L Mg (as MgSO,)
Test No. 3.
solution of 1 m M / L NaHCO3 + 0.4 m M / L EDTA
Test No. 4.
solution of 1 m M / L NaHCO3 + 0.2 m M / L Ca(as CaCI2) + 0.2 m M / L mg (as MgSO4) + 0.4 m M / L EDTA
Metals accumulation by aquatic macrophytes
79
Table 2. Contact times used in EDTA concentration experiment. Na2-EDTA.~Metai Concentration ~ (mg/L) ~
Cd
Contact Time (h)
Pd
1
6
12
24
1
6
12
24
1 2 24
1 2 24
1 2 24
1 2 24
1 2 24
1 2 24
1 2 24
1 2 24
E. crassipes p l a n t s were i n t r o d u c e d into e a c h j a r . A f t e r 1 d a y e x p o s u r e , the p l a n t s were r e m o v e d a n d d r i e d f o r the d e t e r m i n a t i o n o f m e t a l c o n c e n t r a t i o n .
Effect o f E D T A concentration on C d and P b accumulations by E. crassipes. I n this e x p e r i m e n t c a d m i u m a n d lead s o l u t i o n s were a d d e d a t 1 m g / L i n t o j a r s c o n t a i n i n g 1 . 5 - L p o r t i o n s o f m M N a H C O 3 s o l u t i o n , to w h i c h Na2E D T A was a d d e d a t 1, 6, 12, a n d 24 m g / L . E. crassipes p l a n t s were t h e n i n t r o d u c e d i n t o e a c h o f these j a r s . R e p l i c a t e s o f e a c h m e t a l a n d E D T A c o n c e n t r a t i o n were m a d e to a l l o w d i f f e r e n t c o n t a c t times, n a m e l y 1, 2, a n d 24 h, as s h o w n in T a b l e 2. A f t e r t h e specified c o n t a c t
t i m e h a d e l a p s e d , the p l a n t was r e m o v e d a n d s u b j e c t e d to analysis f o r d e t e r m i n a t i o n o f t h e test m e t a l c o n c e n tration.
Determination o f Metal concentration A f t e r e x p o s u r e t o test s o l u t i o n s , the p l a n t s were d r i e d at 105 °C. T h e s h o o t was t h e n s e p a r a t e d f r o m the r o o t g r o u n d u p , w e i g h e d , a n d ignited at 550 °C. Nitric a c i d s o l u t i o n (2:1) was a d d e d to the r e s i d u e a n d the clear s o l u t i o n o b t a i n e d was d i l u t e d b y all-glass redistilled w a t e r to 50 m L . M e t a l c o n c e n t r a t i o n was d e t e r m i n e d using a P e r k i n - E l m e r M o d e l 370 a t o m i c a b s o r p t i o n s p e c t r o p h o t o m e t e r e q u i p p e d with a H e a t e d G r a p h i t e A t o m i z e r M o d e l 2100 a n d d e u t e r i u m a r c b a c k g r o u n d corrector. E a c h result p r e s e n t e d here is a n a v e r a g e o f 10 seq u e n c e r e a d i n g s o n the A t o m i c A b s o r p t i o n ( A . A . ) m a c h i n e . These r e a d i n g s were c o r r e l a t e d with a stand a r d s o l u t i o n . T h e s e s t a n d a r d s were p u r c h a s e d f r o m the A . A . m a n u f a c t u r e s , i.e., P e r k i n - E l m e r . A s c o n t r o l , a b l a n k was m a d e for each m e t a l ; this b l a n k was m a d e o f d o u b l e distilled w a t e r , w h i c h was s u b j e c t e d to all t h e c h e m i c a l t r e a t m e n t a n d d i g e s t i o n similar to t h a t o f the test s a m p l e s .
Table 3. Concentration of Cu, Zn, Cd, and Pb 0zg/g dry plant) in plants isolated from sites in the Nile River and its branches. Metal Concentration (~g/g) Sitesa
Zn
Cd
Pb
2.7
13.8
0.0
2.2
whole whole whole
21.7 3.2 15.5
52.5 30.5 47.8
0.3 0.2 0.5
12.2 11.4 11.8
Eichhornia Panicum
whole whole
89.7 3318
34.2 194.8
0.3 0.3
10.2 12.1
Eichhornia Panicum
whole whole
20.3 4.3
64.6 31.3
0.1 0.1
6.5 4.8
Eichhornia Panicum
Root Shoot Root Stem Leaf
44.1 20.3 47.8 3.8 5.7
105.8 74.5 105.4 35.5 39.9
0.3 0.6 0.3 0.5 0.4
5.2 1.7 7.8 6.1 14.8
Eichhornia
whole
22.5
68.4
0.6
13.2
4. Site No. 4
Eichhornia Ceratophyllum Panicum
whole whole whole
18.8 36.4 10.3
82.3 117.0 90.0
0.3 0.3 0.2
10.8 22.2 12.4
5. Site No. 5
Eichhornia Ceratophyllum
whole whole
47.9 44.4
127.7 127.7
0.4 0.5
6.0 6.2
6. Site No. 6
Eichhornia Ceratophyllum Eichhornia
whole whole whole
57.2 65.8 165.1
171.3 324.7 468.5
0.8 0.4 4.6
6.8 9.6 38.5
1. Site No. 1 2. Site No. 2 U.S. industrial complex
D.S. industrial complex 3. Site No. 3 U.S. industrial complex In front of industrial complex
D.S. Industrial complex
aU.S.
~-
Plant
Part
Ceratophyllum
whole
Eichhornia Panicum Ceratophyllum
upstream; D.S. = downstream.
Cu
80
Sami E. Fayed& Hussein I. Abd-EI-Shafy
Table 4. Concentration of Cd, Cu, Pb, and Zn in water and sediment samples taken from Sites No. 2 and 3. Metal Concentration in Water ~g/L)
Accumulation o f Cu, Cd, and Pb by E. crassipes in the Piston Flow System
Sitea
Cd
Cu
Pb
I. Site No. 2 1.1. U.S. industrial complex 1.2. D.S. industrial complex
1.0 1.0
4.2 4.8
6.7 7.7
1.4 1.7
2. Site No. 3 2.1. U.S. industrial complex 2.2. At industrial complex 2.3. D.S. industrial complex
1.1 1.6 1.1
4.5 3.9 5.1
9.5 9.0 9.0
11.5 12.1 6.6
Zn
Metal Concentration in Sediment (/zg/g) Pb
considerable accumulation of these pollutants in the ecosystem in this area.
Cd
Cu
Zn
1. Site No. 2 1.1. U.S. industrial complex 1.2. D.S. Industrial complex
5.8 4.7
72 53
56 73
290 180
2. Site No. 3 2.1 U.S. industrial complex 2.2. At industrial complex 2.3. D.S. industrial complex
9.8 4.0 17.7
80 61 496
147 96 1800
170 140 480
aU.S. = upstream; D.S. = downstream.
Results and Discussion
Field Investigation Cu, Zn, Cd, and Pb concentrations in the plant samples are presented in Table 3. The concentration of these metals in water and sediment samples are included in Table 4. Table 5 shows that concentration factors of the metals in the sediment samples were, in most cases, much higher than those in the plant samples isolated from the same site. The higher values of metal concentration factor in the sediment might be attributed to the larger surface o f the sediment particulates and to a longer contact time with running waters. The results showed also that metal concentration in the sediment and plant samples taken downstream from the wastewater discharge points were higher than those taken upstream o f these points. This proves that aquatic plants can act as scavengers of metals from water while still maintaining a healthy status. These results may thus suggest the use o f local seasonal aquatic macrophytes, such as Eichhornia in assessing recent pollution by metals. The analysis o f the plant samples (Table 3), indicated that the aquatic ecosystem was heavily polluted by Cu at site No. 2 and by Zn at sites No. 3 and 4. Further downstream, it seems that industrialization at Site No. 5 resulted in a heavy pollution o f the aquatic ecosystem along the canal by Zn. However, higher concentrations of Zn, Cu, Pb, and Cd were detected in the plants isolated from the end of this canal (Site No. 6), indicating
The changes in Cu, Cd, and Pb concentration in water and plant samples in the experimental gutter are presented in Tables 6 and 7 respectively. Lead was not detected in the water that passed through zone 4 during the whole period of the experiment. Copper was detected in water samples taken from the same zone after the flow of 327 L of feed water, while cadmium was detected much earlier. This was reflected in the metal content of the root of the test plant isolated from zone 1 of the gutter as shown in Fig. 1, where it appears that copper and lead concentrations were higher than cadmium concentration. Because the molar ratio between metals in the water in zone 4 changed due to differences in metal removal rates in the preceding zones, metals concentration of the roots of plants isolated from this zone was of lower levels and of different order o f magnitude. Figure 2 shows that while metals concentration in the root of plants isolated from zone 1 followed the decreasing order Pb > Cu > Cd, the concentration of metals in the shoot followed the decreasing order Cd > Cu > Pb, indicating that Cd was translocated to the shoot by a higher rate than were Cu and Pb.
Accumulation o f Cu, Cd, and Pb by E. crassipes in the continuous f l o w completely mixed system In this system detention time in the container varied between 6.45 and 6.67 days. Results obtained are presented in Table 8. None o f the test metals was detected in the first 48 L o f the effluent, denoting the efficient removal of the metals by the test plant under the experimental conditions. Later on, cadmium was the first metal detected in the water o f the experimental container, indicating that cadmium had the least affinity to plant root surface. This was reflected in the relative concentrations of the test metals in the roots o f plants isolated from the container by the end o f the experiment. It was found that these concentrations were of the decreasing order Pb > Cu > Cd, the same order detected in the exposed plants in the piston flow system. The results showed also that the test metals were translocated to the plant shoot in minor concentrations. The amount of metal translocated increased with the increase in water flow through the container.
Cu, Cd, Zn, and Pb Accumulation by E. crassipes under different chemical compositions in a Batch System Effect o f metal:plant exposure ratio on metal accumulation. In this experiment, metal accumulation by the test plant from a synthetic medium (mM NaHCO3 solution)
81
Metals accumulation by aquatic macrophytes Table 5. Concentration factors (CF) of Cd, Cu, Zn, and Pb in aquatic plants and sediments in sites No. 2 & 3. Metal Concentration (ppb) Site
Ecophase
Site No. 2. Upstream industrial complex
Cd
Water Plant Eichhornia CF Panicum CF Ceratophyllum CF Sediment CF
Downstream industrial complex
1.0 300 300 200 200 500 500 5800 5800
Water Plant Eichhornia CF Panicum CF Sediment CF
Site No. 3 Upstream industrial complex
300 300 300 300 4700 4700
21000 5000 3200 762 15500 3690 72000 17142
Water Plant Eichhornia CF Sediment CF
600 545 17700 16090
6.7
52500 37500 30500 21785 47800 34142 290000 207142
12200 1820 11400 1701 11800 1761 56000 8358
1.7
7.7
89700 18687 33800 7041 53000 11042
34200 20117 194800 114588 180000 105882
4.5
10200 1324 12100 1571 7300 948
11.5
20300 4511 4300 955 80000 17777
1.1
Pb
1.4
4.8
1.1 100 91 100 91 9800 8909
Zn
4.2
1.0
Water Plant Eichhornia CF Panicum CF Sediment CF
Downstream industrial complex
Cu
9.5
64600 5617 31300 2720 170000 14782
5.1
6.6
22500 4412 494000 96862
68400 10364 480000 72727
6500 684 4800 505 147000 15473 9.0 13200 1466 1800000 200000
Table 6. Temporal and spatial changes in Cd, Cu, and Pb concentrations in water samples taken from the experimental gutter. Concentrations of Metals O~M/L) Flow after Metals Addition (L) 0 40 94 195 243 327 405 465
Zone 1 Cd
Zone 2
Zone 3
Zone 4
Cu
Pb
Cd
Cu
Pb
Cd
Cu
Pb
Cd
Cu
Pb
0.0 0.0 0.2 0.0 0.4 0.0
0.0 0.0 0.0
0.0 0.1
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0 0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.6 0.0 0.0 1.1 0.2 0.0 0.9 0.3 0.5 0.9 0.5 1.4 0.5
0.3 0.2
0.3 0.0 0.0 0.6 0.0 0.0 0.6 0.0 0.0
0.0 0.0 0.0 0.1 0.0 0.0 0.1 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.2 0.1 1.4 0.1
0.0 0.0
82
Sami E. Fayed & Hussein I. Abd-E1-Shafy Table 7. Temporal and spatial changes in Cd, Cu, and Pb concentrations in plants isolated from the experimental gutter. Metal concentration (~M/g plant material)
Flow after Metal Addition
Zone 1
(L)
Cd
La Ra L R L R L R L R
195 243 327 465
0.00 0.02 0.41 2.63 0.40 3.92 0.89 5.14 0.99 5.58
Cu
Zone 4 Pb
0.18 0.02 0.18 0.05 0.34 0.20 5.70 6.71 0.51 0.19 6.96 8.15 0.57 0.28 12.09 14.53 0.84 0.64 16.19 24.67
Cd
Cu
Pb
1.0
~
0.8
0.6
0.03 0.09 0.02 0.25 0.08 0.93 0.19 3.81
0.23 0.56 0.26 0.70 0.31 1.58 0.35 1.92
0.07 0.24 0.07 0.22 0.06 0.48 0.09 0.60
I
0.4
71/'°
....
0.2 0.0
o--at_.C---~o._~=~ I
I 300 400 Flow, Liters of Test Water
200
aL = shoot; R = root.
and from a natural medium (Nile water) was investigated. The results obtained (Figs. 3-5) showed a positive linear relationship between metal-to-plant exposure ratio and the amount of metal accumulated by E. crassipes root, especially at the low exposure ratios. This may lead to suggest that metal accumulation by plant material is a surface phenomenon. Similar findings have been reported by Hutchinson and Czyrska (1975). The results showed also that metal accumulations from the two media, namely, the Nile water (moderately hard) and the NaHCO3 solution (no hardness) were of similar rates at the same metal-to-plant exposure ratio, indicating that moderate hardness did not interfere with metal accumulation. It was found that the plant root was able to accumulate up to 6.126 mg Cu, 5.075 mg Zn, 2.445 mg Cd, or
20-
p
I 500
Fig. 2. Metal content of Eichhornia shoots isolated from the ends of Zone 1 ( t , i , and I ) and Zone 4 ( O , / % and [~) during test water flow.
6.00 mg Pb per one gram of root, on a dry weight basis. Analysis of the exposed plants (Fig. 6) showed that the shoots carried the test metal in relatively low concentrations compared to the roots. Thus, metal translocation to the shoots took place even with cadmium and lead, which are not plant nutrients. The highest rate of translocation was shown with cadmium and the lowest was with copper. In this respect, England (1980) noticed little translocation of cadmium in water hyacinth.
Accumulation o f Cu, Zn, Cd, and Pb in combination from NaHC03 solution. This experiment was performed using solution containing a combination of Cu, Zn, Cd, and Pb at equimolar concentrations. The results obtained are compiled in Table 9 and illustrated in Fig. 7, where a linear relationship is shown between the amount of accumulated metals and the metal-to-plant exposure ratio, especially at the lower ratios. However, the results did not indicate any preferential uptake among the test metals at 24 h contact time.
Cu 0
= x
= In Nile water x In Distilledwater
5-
o
~------.-;~ ==--~.F--=-1~ 200
"1- - - P b - - ~
300 400 Ftow, Liters of Test Water
I 500 2
4
6
8
I
10
Exposure Ratio, mg Cu/g
Fig. 1. Metal content of Eichhornia roots isolated from the ends of Zone 1 ( I , &, and l ) and Zone 4 ( O , / % and C]) during test water flow.
I
12
I
1A
I
16
Root
Fig. 3. Effect of exposure ratio on metal accumulation by Eichhornia crassipes.
Metals accumulation by aquatic macrophytes
83
Table 8. Temporal changes in Cd, Cu, and Pb concentrations in water and in plant in the continuous flow mixed system. Concentration of Metals in plant ~ M / g )
Concentration of Metals in Dish Watera,/~M Time after Metal Addition (days)
Flow after Metal Addition (L)
0
0
Cd
Cu
Pb
0.00
0.00
0.00
3 7 12
19.8 48.2 80.2
0.00 0.00 0.19
0.00 0.00 0.00
0.00 0.00 0.00
18
116.8
0.61
0.52
--
24
153.4
0.85
0.42
0.45
Cd
Cu
Pb
Rb
0.00 0.02
0.16 0.16
0.02 0.05
L R L R L R
0.23 2.36 0.29 4.31 0.99 7.14
0.39 2.35 0.39 5.28 0.63 12.03
0.10 1.99 0.12 6.14 0.27 13.15
Lb
aConcentrations of metals in feed water was raised from 0.5/~M to 1 /zM after the twelfth day o f flow through of contaminated water. bL = shoot; R = root.
Cd
E
Zn
O
e x
U
-- In Nile w a t e r x In Distilled water
1D
•
= x
X
--- In Nile w a t e r ~ In Distilled w a t e r
N
0 0
I 8 Root
2 4 6 Exposure Ratio, mg Zn/g
0
2
4
6
B
Exposure Ratio,rng Cd/g Root
Fig. 4. Effect of exposure ratio on metal accumulation by Eichhornia crassipes.
By comparing the data obtained from this experiment with those obtained from the metal-to-plant exposure ratio (described above), using single metal solutions (Figs. 3-5), it seemed that at the same metal-to-plant exposure ratio Cd and Cu accumulation by the root was enhanced in the presence of the other metals (Table 10). On the other hand, Pb and Zn accumulations were at lower rates in the presence of the other test metals, 15
o ¢r
..~
Pb 12
Y 8
-
x i
4
8
12
16
Exposure Ratio,mg Pb/g
in
N i l e water
K lq DistilL-=dwater
x
20
I 24
i 28
Root
Fig. 5. Effect o f exposure ratio on metal accumulation by Eichhornia
crassipes.
especially at the higher metal-to-plant exposure ratios. Similarly, synergestic effects were previously found by Hutchinson and Czyrska (1975), who reported that cobalt and nickel uptake were increased by the presence of other metals.
Effects of chemical
characteristics o f water on C d and Pb accumulation. The results of tests No. 1 and No. 3 (Table 12), showed that the presence of EDTA in the test water greatly reduced lead accumulation by the root. However, this retarding effect of EDTA was much less displayed on cadmium accumulation, as shown in Table 11. The results of tests No. 3 and No. 4 in Tables 11 and 12 showed t h a t - a t the same level of metal-to-plant r a t i o s - t h e addition of Ca 2÷ and Mg 2÷ did not eliminate the effect of EDTA on Cd and Pb accumulation. By comparing metal accumulation in the s h o o t s - at the same level of exposure ratios-- with and without EDTA, it may be noticed that this organic chelator, at the concentration applied in this experiment, did not interfere with metal translocation to the shoot.
84
Sami E. Fayed & Hussein I. Abd-EI-Shafy Table 9. Accumulation of Cu, Zn, Cd, and Pb by E. crassipes exposed to equimolar concentrations of these metals. Root
Shoot
Exposure Ratio 0tM/g) b
Cu
Zn
Cd
A
3.71 1.89 2.80
2.895 2.895 2.565
4.740 3.196 4.419
B
6.64 6.75 5.26
4.469 4.642 3.698
C
13.14 23.69 8.07
D
27.91 38.02 62.98
Metal Added
Metals Accumulated (#M/g) Pb
Exposure Ratio (#M/g)
Metals Accumulated (#M/g) Cu
Zn
Cd
Pb
2.447 1.521 2.190
2.206 1.197 1.684
2.02 1.38 1.60
0.519 0.441 0.409
1.957 1.177 1.024
0.026 0.169 0.124
0.121 0.048 0.096
5.321 5.642 4.327
4.742 4.662 3.781
3.972 3.803 3.441
2.73 2.60 2.44
0.535 0.739 0.645
1.223 1.040 1.453
0.222 0.196 0.365
0.135 0.135 0.188
7.333 13.737 5.020
7.905 11.483 6.024
8.123 12.865 5.224
6.723 11.680 4.184
5.59 7.92 5.99
0.739 1.603 0.677
1.116 1.483 1.101
0.587 0.792 0.569
0.396 0.560 0.347
12.856 19.544 25.492
12.385 19.032 21.027
16.130 23.318 27.082
14.049 20.743 28.697
10.20 14.77 19.47
0.991 0.960 1.574
1.651 1.376 2.859
1.059 1.014 1.584
0.825 0.719 1.226
aA = 2/~M/L, B = 4 #M/L, C = 8 #M/L, D = 16 #M/L each of Cu, Zn Cd, and Pb. Final pH ranged from 6.5-6.6 bExposure ratio = amount of metal in test water in/~M divided by dry weight of exposed plant material.
Effect o f EDT A concentration on metal accumulation. Results obtained at the close metal:plant exposure ratios are illustrated in Figs. 8 and 9, where metal accumulations are compared at different EDTA concentrations. These figures showed that at 1 mg metal/L and with 7 mg/L EDTA or more, metal accumulation was greatly inhibited. This might indicate that organic ligands liable to occur in natural waters will be a competitor with plant surfaces on metallic pollutants. The effect of contact time on metal accumulation in the shoot and root are illustrated in Figs. 10 and 11, respectively. These figures show that at close exposure
ratios the percentage of the accumulated metal in the first 2 h amounted to 56°/0 for Cd and 67°70 for Pb, compared with the amounts accumulated in 24 h.
Conclusions The outcome from this study has been formulated into the following conclusions: 1. Since aquatic weeds can be potential scavengers for hazardous pollutants such as heavy metals, they
Table 10. Comparison between metals accumulation, in combination (1"*) and separate (2***) by E. crassipes. Cu
Zn Accumulation, mg/g
Accumulation, mg/g E.R.*, mg/g
1"*
0.12 0.18 0.24 0.33 0.42 0.43 0.51 0.83 1.51 1.77 2.42 4.00
0.13 0.16 0.18 0.23 0.28 0.29 0.32 0.46 0.87 0.82 1.24 1.62
Cd
2***
E.R.*, mg/g
l**
0.05 0.08 0.10 0.15 0.18 0.18 0.20 0.30 0.50 0.60 0.82 1.40
0.12 0.18 0.24 0.34 0.43 0.44 0.53 0.86 1.55 1.82 2.49 4.12
0.11 0.19 0.21 0.18 0.25 0.27 0.29 0.42 0.65 0.71 1.14 1.27
E.R. = Metal-to-plant exposure ratio *From table 4 transferred from uM metal/g into mg/g **From table 4 transferred from uM metal/g into mg/g ***From figures 1, 2 and 3.
Pb
Accumulation, mg/g
2***
E.R.*, mg/g
l**
0.08 0.12 0.16 0.23 0.29 0.29 0.36 0.58 1.04 1.22 1.67 2.76
0.21 0.31 0.42 0.59 0.75 0.76 0.91 1.48 2.66 3.14 4.27 7.08
0.17 0.24 0.28 0.43 0.53 0.52 0.59 0.91 1.45 1.81 2.62 3.04
Accumulation, mg/g
2***
E.R., mg/g
l**
2***
0.09 0.13 0.18 0.25 0.31 0.31 0.38 0.62 1.11 1.31 1.78 2.95
0.39 0.58 0.77 1.09 1.38 0.40 1.67 2.72 4.91 5.78 7.88 13.05
0.25 0.35 0.46 0.71 0.82 0.79 0.87 1.39 1.42 2.91 4.30 5.95
0.24 0.36 0.48 0.68 0.86 0.88 1.04 1.70 3.07 3.61 4.92 7.20
85
Metals accumulation by aquatic macrophytes Table 11. Accumulation of cadmium by E. crassipes after l-day exposure from media of different chemical characteristics, a Shoot
Root
Cd Removal (%)
Test No.
Exposure Ratio (mg/g)
Cd Accum. (mg/g)
Exposure Ratio (mg/g)
Cd Accum. (mg/g)
By Shoot
Bt Root
By Total Plant
1
0.691 0.737 0.772
0.026 0.047 0.036
1.020 1.121 1.528
0.809 0.792 1.045
3.7 6.4 4.7
70.3 73.1 68.4
83.0 79.5 73.1
2
0.576 0.931 0.756
0.026 0.079 0.029
0.887 2.364 1.336
0.608 1.385 0.642
4.5 8.5 3.8
69.3 58.5 48.0
73.8 67.0 51.8
3
0.620 0.582 1.117
0.013 0.012 0.480
1.158 1.723 2.609
0.380 0.410 0.785
2.1 2.0 4.3
32.8 56.8 30.1
34.9 58.8 34.4
4
0.498 0.777 0.656
0.016 0.030 0.031
1.200 2.239 1.489
0.485 0.867 0.660
3.2 3.9 4.7
58.1 38.7 44.3
61.3 42.6 49.1
aTest water volume = 1.5 L; final pH value ranged from 7.0 to 7.3.
0.6
Pb 0.Z, c" t/) X
•
02
I
0.(2
I
L
r
I
15 O
×
Cu 0.6
E
D
0.4-
t~
Cd
0.23r 0.C 0
I
1
1
4 0 2 6 Metal Accumulation by the Root.mg Metal/g Root
2
~+
Fig. 6. Metal accumulation by the shoot and root of Eichhornia crassipes: •
•
In Nile water; x
6
x In distilled water + NaHCO3.
86
Sami E. Fayed & Hussein I. Abd-EI-Shafy
I~oot
Cu ,~ Zn A Cd x Pb o
322~
Exposure ratio : 0.79-1.03 rng Pb/g Fkx~
O.
x A
~0.
O
24 ~E ~-
8
x
20
o
? 16 ~
Shoo(
1
8 A
~
•
oX 12-
A
13 o
OI
i
0
4
I
8
J
i
12
"6
i
20
I
24
EDTA Concentration, mcj/t
~
8
Fig. 9. Effect of E D T A concentration on lead accumulation by Eichhornia crassipes.
X
0
10
,
,
,
,
,
20
30
z,O
50
60
Exposure Rat/o,).tM/g
Root
Fig. 7 Metal accumulation in Eichhornia root at different exposure ratios.
Root 0.40 Root Exposure ratio 0.88-1.35 mg C d / g Iqoot
0.30
J
12
~
U
E
020
E ._O
.~" 0.20
Exposure ratio : 0.47 - 0.62 mg Cd/g
0110
Root
D
E u:~
0
:
;
t
~
E
t
I
Shoot
Shoot sure ratio : 0.4B - 0.51 rng Cd / g
~ 0.04
o
~ 0.020
0.02[
0.010 Exposure ratio • 0.39 - 0.42 mg Cd/g
OI 0
I
4
I
8
?
12
J
16
I
20
L
24
E DTA Concentration, mg/t Fig. 8. Effect of E D T A concentration on c a d m i u m accumulation by Eichhornia crassipes.
0
0
I
Shoot I
2
24 Contact Time, hours
Fig. 10. Effect of contact time on c a d m i u m accumulation by Eichhornia crassipes.
Metals accumulation by aquatic macrophytes
87
Table 12. Accumulation of lead by E. crassipes after 1-day exposure from media of different chemical compositions, a Shoot
Root
Pb Removal (°7o)
Test No.
Exposure Ratio (mg/g)
Pb Accum. (mg/g)
Exposure Ratio (mg/g)
Ph Accum. (mg/g)
By Shoot
Bt Root
By Total Plant
1
0.972 0.771 0.658
0.041 0.033 0.018
1.525 1.032 0.609
0.728 0.729 0.408
4.2 2.5 2.7
51.7 70.7 67.1
55.9 73.2 69.8
2
1.135 1.619 0.943
0.032 0.031 0.021
1.545 1.313 1.286
1.218 0.844 0.935
2.8 1.9 2.2
78.8 64.8 72.8
81.6 66.2 75.0
3
0.691 0.955 0.683
0.010 0.021 0.012
1.077 0.917 0.835
0.053 0.046 0.053
1.4 2.2 1.8
4.9 5.0 6.4
6.3 7.2 8.2
4
0.457 0.844 0.571
0.008 0.006 0.011
0.648 0.783 1.136
0.055 0.057 0.064
1.8 0.7 1.8
8.8 7.2 5.6
10.6 7.9 7.4
aTest water volume = 1.5 L; final pH value ranged from 7.8 to 7.0.
might be better dealt with through managing programs rather than eradication from the aquatic ecosystem. 2. A q u a t i c m a c r o p h y t e s s h o u l d n o t b e e x p e c t e d t o remove heavy metals successfully from organic wastewater effluents. 3. A q u a t i c p l a n t s c o l l e c t e d f r o m a r e a s p o l l u t e d b y h e a v y m e t a l s s h o u l d n o t b e u s e d as a f o d d e r f o r a n i m a l s o r as a f e r t i l i z e r .
Root 0.3C
0.2C
P Exposure ratio : 0?9 - 0.8"/rng Pblg
0.1(3
i
Root
I
Shoot 0.20
O01(
,.... Exposure ratio : 0.35 - 0.39 rng Pb/g =
Sho~ I
2 Contact Time, hours
Fig. 11. Effect of contact time on lead accumulation by Eichhornia crassipes.
Acknowledgements-This work was supported by a grant provided under the contract No. PR 3-541-3 between the United States Environmental Protection Agency and the Egyptian National Research Centre.
References
American Public Health Association/American Water Works Association (1975) Standard Methods for the Examination of Water and Wastewater, 14th ed., A P H A AWWA, Washington, DC. Cook, J. (1977) Environmental pollution by heavy metals, lnt. J. Environ. Studies. 10, 253-256. Englande, A. J. (1980) Tertiary wastewater treatment by the application of vascular aquatic plants. Municipal Wastewater Reuse News, No. 33, pp. 14-15. AWWA Research Foundation, Denver, CO. Hutchinson, T. C. and Czyrska, H. (1975) Heavy metal toxicity and synergism to floating aquatic weeds, Verh. lnternat. Verein. Limmo. 19, 2102-211. Kinkade, M. L. and Erdman, H. E. (1975) The influence of hardness components (Ca a*and Mg 2÷)in water on the uptake and concentration of cadmium in a simulated freshwater ecosystem, Environ. Res. 10, 308-313. Richert, D. A., Kennedy, V. C., Meckenzie, S. W., and Hines, W. G. (1977) A synoptic survey of trace metals in bottom sediments of the Willamette River, Oregon. Geological Survey Circular 715F. U.S. Dept. of the Interior. U.S. National Academy of Sciences (1976) Making aquatic weeds useful: Some perspectives for developing countries, National Academy of Sciences, Washington, DC. Wilson, A. L. (1976) Concentration of trace metals in river waters. A review, TR., 16. (Personal communication.) Wolverton, B. C. (1975) Water hyacinths for removal of cadmium and nickel from polluted waters. NASA Technical Memorandum TM-X-72721, National Aeronautics and Space Administration, Washington, DC. Wolverton, B. C. and McDonald, R. C. (1975) Water hyacinths and alligator weeds for removal of silver, cobalt and strontium from polluted waters. NASA Technical Memorandum TM-X-72727, National Aeronautics and Space Administration, Washington, DC. Wolverton, B. C. and McDonald, R. C. (1976), Water hyacinths (Eichhornia crassipes) for removing chemical and photographic pollutants from laboratory wastewaters. National Aeronautics and Space Administration, Washington, DC, TM-X-72731.
0160-4120/85 $3.00 + .00 Copyright © 1985 Pergamon Press Ltd.
ACCUMULATION OF Cu, Zn, Cd, AND Pb BY AQUATIC MACROPHYTES Sami E. Fayed and Hussein I. Abd-EI-Shafy National Research Centre, Dokki, Cairo, Egypt (Received 11 June 1984; Accepted 12 November 1984) The levels of Cu, Zn, Cd, and Pb were determined in water, sediment, and aquatic plant samples taken from the Nile River and its branches at selected sites characterized by heavy industrialization and dense population. The results revealed that concentration factors in the sediments were, in most cases, much higher than in plants. Metals content in the plants collected from downstream wastewater discharge points was usually higher than that in the plants collected from sites upstream of these points. In laboratory scale models of the piston and completely mixed continuous flow hydraulic systems, Cu, Cd, and Pb removal by a test plant (Eichhornia crassipes) was assessed. The results showed that the root of the test plant acted as a scavenger for the metals up to a certain capacity. The metals were taken up by different rates, the least of them was that of cadmium. In a batch system metals accumulation from waters of different compositions was investigated using the same test plant. The results are summarized in the following: (1) Cu, Zn, Cd, or Pb accumulation was a function of metal:plant root exposure ratio on dry weight basis. (2) The rates of metals accumulation from both the natural medium (Nile water) and the synthetic medium (mM NaI-ICO3 solution) were quite close. (3) Metal accumulation was much lower in the presence of EDTA. (4) The presence of Ca 2÷and Mg2÷in a concentration equivalent to that of EDTA did not eliminate the retarding effect of the latter on metal accumulation. (5) Metal translocation from the root to the shoot occurred at a low rate compared to metal accumulation by the root.
Introduction
M a t e r i a l s and M e t h o d s
S u r f a c e w a t e r p o l l u t i o n b y h e a v y m e t a l s results m a i n l y from wastewater discharge into water bodies and from l a n d r u n o f f ( W i l s o n , 1976; C o o k , 1977; R i c h e r t et al., 1977). T h e p h e n o m e n o n o f p o l l u t a n t c o n c e n t r a t i o n b y a q u a t i c p l a n t s has b e e n n o t i c e d in p o n d s c r e a t e d f o r the d u m p i n g o f w a s t e w a t e r effluents, w h e r e these p l a n t s flourish on behalf of nutrient content of water ( E n g l a n d e , 1980; W o l v e r t o n , 1975; W o l v e r t o n a n d M c D o n a l d , 1975, 1976). T h e r e has b e e n a n e m p h a s i s o n c o n v e r t i n g a q u a t i c weeds i n t o a useful r e s o u r c e , f o r exa m p l e , as a n i m a l feed, as fertilizer, o r f o r energy p r o d u c t i o n ( N A S , 1976; W o l v e r t o n , 1975). I n f o r m a t i o n o n m e t a l a c c u m u l a t i o n b y a q u a t i c p l a n t s m a y be r e q u i r e d for aquatic weed management. A field i n v e s t i g a t i o n was c o n d u c t e d in o r d e r to assess the i m p a c t o f i n d u s t r i a l activities o n the levels o f h e a v y m e t a l s in the a d j a c e n t a q u a t i c e c o s y s t e m . In a d d i t i o n , the a f f i n i t y o f E i c h h o r n i a crassipes, to m e t a l a c c u m u l a tion was e x a m i n e d in l a b o r a t o r y scale m o d e l s o f the p i s t o n a n d c o m p l e t e l y m i x e d c o n t i n u o u s flow systems. In a b a t c h system, m e t a l a c c u m u l a t i o n u n d e r d i f f e r e n t c h e m i c a l c o n d i t i o n s was also i n v e s t i g a t e d .
Field Investigation C o m p o s i t e s a m p l e s were t a k e n r a n d o m l y f r o m each o f six selected sites along the Nile River. The sites started f r o m the H i g h D a m lake, went d o w n s t r e a m to the R a s h i d b r a n c h o f the river, a n d c o n t i n u e d to the end o f a c a n a l e m e r g i n g f r o m the R a s h i d b r a n c h . A b a c k g r o u n d p l a n t s a m p l e was collected f r o m the l a k e (Site N o . 1), far f r o m u p s t r e a m a n y i n d u s t r i a l activities. A b o u t 500 mi d o w n s t r e a m f r o m the d a m , p l a n t , s e d i m e n t , a n d w a t e r s a m p l e s were t a k e n f r o m the river at site N o . 2, w h e r e i r o n a n d steel, a n d c o k e industries are located. Site N o . 3 was selected 150 mi farther d o w n s t r e a m o n the R a s h i d b r a n c h o f t h e river, w h e r e factories p r o d u c i n g pesticides, p h o s p h a t e fertilizers, a n d s o a p a n d s o d a a r e l o c a t e d . S a m p l e s t a k e n . a t sites N o . 2 a n d 3 were t a k e n b o t h u p s t r e a m a n d d o w n s t r e a m f r o m the w a s t e w a t e r d i s c h a r g e p o i n t . T h e h e a v i l y p o p u l a t e d C a i r o District is l o c a t e d b e t w e e n sites N o . 2 a n d 3. P l a n t s a m p l e s were t a k e n f r o m t h e river in the C a i r o District, site N o . 4. S a m p l i n g site N o . 5 was selected a b o u t m i d w a y in a c a n a l e m e r g i n g f r o m the R a s h i d b r a n c h o f the river. This site is 160 mi d o w n s t r e a m f r o m site N o . 3 77
78
Sami E. Fayed & Hussein I. Abd-E1-Shafy
and located in the Alexandria District, which contains various industries. In addition, plant samples were collected at the end of this canal from a location called Site No. 6. The samples were dried at 105 °C, weighed, and then digested by a mixture of HNO3 and H202 under flux for the determination of Cu, Zn, Cd, and Pb concentrations.
Accumulation o f Cu, Cd, and Pb by E. crassipes in a Piston Flow System Eichhornia crassipes (the test plant) was obtained from a manmade pond, where this plant is maintained among some of the aquatic ornamental plants in a botanical garden. A laboratory scale gutter made of plexiglass (5 m long, 25 cm wide, and 30 cm deep) was filled with 250 L filtered Nile water. The chemical characteristics of this water (Table 1) were determined according to Standard Methods (APHA, 1975). Fifty of the test plants were introduced into the gutter. The plants were exposed to illumination (about 4000 lux) for 14 h daily using cool white flourescent tubes and tungsten lamps. A continuous flow of filtered Nile water was secured into the gutter using a peristaltic dosing pump at a rate ranging between 12 to 13 L per day for a period of 15 days. Then, equimolar solutions of each of Cd (as CdCI2), Cu (as CuSO4) and Pb (as Pb(NO3)2) were added to the feed water at a rate of 0.5 #M/L for each metal for 9 days. This concentration was later raised to 1 /zM/L. The gutter was externally marked into four zones. Water samples (50 mL) were withdrawn and plant samples were picked up from the different zones at the times indicated in the corresponding table. The samples were subjected to analysis for determination of metals concentration. Accumulation o f Cu, Cd, and Pb by E. crassipes in a continuous f l o w completely mixed system This experiment was carried out in a plexiglass dish with 40 L capacity and 30 cm depth. The dish was filled with filtered Nile water, and Eichhornia crassipes plants were introduced into it. The plants were exposed to illumination as that used in the previous experiment. The dish was continuously supplied with the water at a
Table 1. Chemical characteristics of Nile water used in this study (average). Electric conductance ~ m h o cm -1) pH Total hardness, as CaCO3 Total alkalinity, as CaCO3 Chlorides, as C1Sulfates, as SO7 Total phosphorus, as P Ortho phosphate, as P Nitrate, as N
320 7.8-8.2 102 mg/L 112 mg/L 18 mg/L 16 mg/L 0.098 mg/L 0.051 mg/L 0.054 mg/L
rate of 6.0-6.2 L per day using a peristaltic dosing pump. A stainless steel stirrer kept the water of the dish continuously mixed. After two weeks, equimolar solutions of Cd, Cu, and Pb were added at a rate of 0.5 #M/ L of each metal in the feed water for 6 days. This concentration was later raised to 1 /zM/L. Water samples (50 mL) were withdrawn from both the feed tank and the experimental dish. After 11 days of metal addition to the feed water, plant samples were picked up at the times indicated in corresponding table. Metals concentration was then determined in the water and plant samples.
Cu, Cd, Zn, and Pb Accumulation by E. crassipes under different chemical conditions in a Batch System Effect o f Metal:Plant exposure ratio on metal accumulation. In this experiment, metal accumulation from filtered Nile water and from mM NaHCO3 solution by E. crassipes was assessed. First, 1.5-L portions of the test water were introduced into each of 2-L capacity plastic jars. Then copper, zinc, or cadmium was added to the test water at concentrations of 0.0, 1.0, 2.5, and l0 mg/L, while lead was added at 0.0, 1.0, 5.0, and 30 mg/L. The test plants were introduced into the jars and exposed to continuous illumination. After 1 day exposure, the plants were removed and dried for determination of metal concentration. Accumulation o f Cu, Zn, Cd, and Pb in combination from NaHC03 solution. First, 1.5-L portions of mM NaHCO3 solution were introduced into 2-L capacity plastic jars. Then aliquots of Cu, Zn, Cd, and Pb solutions were added to each of these jars to obtain equimolar concentrations of these metals. These concentrations were 2, 4, 8, and 16 #M/L. E. crassipes plants were introduced into the jars and exposed to continuous illumination. After 1 day exposure, these plants were removed and dried for determination of metals concentration. Effect o f some chemical characteristics o f water on Cd and Pb accumulations. Aliquots of cadmium and lead solutions were added separately to 1.5 L of each of the following test solutions contained in 2-L plastic jars. The concentration of the test metal was one mg/L. Test No. 1.
m M / L NaHCO3 solution
Test No. 2.
solution of 1 m M / L NaHCO3 + 0.2 m M / L Ca(as CaCI,) + 0.2 m M / L Mg (as MgSO,)
Test No. 3.
solution of 1 m M / L NaHCO3 + 0.4 m M / L EDTA
Test No. 4.
solution of 1 m M / L NaHCO3 + 0.2 m M / L Ca(as CaCI2) + 0.2 m M / L mg (as MgSO4) + 0.4 m M / L EDTA
Metals accumulation by aquatic macrophytes
79
Table 2. Contact times used in EDTA concentration experiment. Na2-EDTA.~Metai Concentration ~ (mg/L) ~
Cd
Contact Time (h)
Pd
1
6
12
24
1
6
12
24
1 2 24
1 2 24
1 2 24
1 2 24
1 2 24
1 2 24
1 2 24
1 2 24
E. crassipes p l a n t s were i n t r o d u c e d into e a c h j a r . A f t e r 1 d a y e x p o s u r e , the p l a n t s were r e m o v e d a n d d r i e d f o r the d e t e r m i n a t i o n o f m e t a l c o n c e n t r a t i o n .
Effect o f E D T A concentration on C d and P b accumulations by E. crassipes. I n this e x p e r i m e n t c a d m i u m a n d lead s o l u t i o n s were a d d e d a t 1 m g / L i n t o j a r s c o n t a i n i n g 1 . 5 - L p o r t i o n s o f m M N a H C O 3 s o l u t i o n , to w h i c h Na2E D T A was a d d e d a t 1, 6, 12, a n d 24 m g / L . E. crassipes p l a n t s were t h e n i n t r o d u c e d i n t o e a c h o f these j a r s . R e p l i c a t e s o f e a c h m e t a l a n d E D T A c o n c e n t r a t i o n were m a d e to a l l o w d i f f e r e n t c o n t a c t times, n a m e l y 1, 2, a n d 24 h, as s h o w n in T a b l e 2. A f t e r t h e specified c o n t a c t
t i m e h a d e l a p s e d , the p l a n t was r e m o v e d a n d s u b j e c t e d to analysis f o r d e t e r m i n a t i o n o f t h e test m e t a l c o n c e n tration.
Determination o f Metal concentration A f t e r e x p o s u r e t o test s o l u t i o n s , the p l a n t s were d r i e d at 105 °C. T h e s h o o t was t h e n s e p a r a t e d f r o m the r o o t g r o u n d u p , w e i g h e d , a n d ignited at 550 °C. Nitric a c i d s o l u t i o n (2:1) was a d d e d to the r e s i d u e a n d the clear s o l u t i o n o b t a i n e d was d i l u t e d b y all-glass redistilled w a t e r to 50 m L . M e t a l c o n c e n t r a t i o n was d e t e r m i n e d using a P e r k i n - E l m e r M o d e l 370 a t o m i c a b s o r p t i o n s p e c t r o p h o t o m e t e r e q u i p p e d with a H e a t e d G r a p h i t e A t o m i z e r M o d e l 2100 a n d d e u t e r i u m a r c b a c k g r o u n d corrector. E a c h result p r e s e n t e d here is a n a v e r a g e o f 10 seq u e n c e r e a d i n g s o n the A t o m i c A b s o r p t i o n ( A . A . ) m a c h i n e . These r e a d i n g s were c o r r e l a t e d with a stand a r d s o l u t i o n . T h e s e s t a n d a r d s were p u r c h a s e d f r o m the A . A . m a n u f a c t u r e s , i.e., P e r k i n - E l m e r . A s c o n t r o l , a b l a n k was m a d e for each m e t a l ; this b l a n k was m a d e o f d o u b l e distilled w a t e r , w h i c h was s u b j e c t e d to all t h e c h e m i c a l t r e a t m e n t a n d d i g e s t i o n similar to t h a t o f the test s a m p l e s .
Table 3. Concentration of Cu, Zn, Cd, and Pb 0zg/g dry plant) in plants isolated from sites in the Nile River and its branches. Metal Concentration (~g/g) Sitesa
Zn
Cd
Pb
2.7
13.8
0.0
2.2
whole whole whole
21.7 3.2 15.5
52.5 30.5 47.8
0.3 0.2 0.5
12.2 11.4 11.8
Eichhornia Panicum
whole whole
89.7 3318
34.2 194.8
0.3 0.3
10.2 12.1
Eichhornia Panicum
whole whole
20.3 4.3
64.6 31.3
0.1 0.1
6.5 4.8
Eichhornia Panicum
Root Shoot Root Stem Leaf
44.1 20.3 47.8 3.8 5.7
105.8 74.5 105.4 35.5 39.9
0.3 0.6 0.3 0.5 0.4
5.2 1.7 7.8 6.1 14.8
Eichhornia
whole
22.5
68.4
0.6
13.2
4. Site No. 4
Eichhornia Ceratophyllum Panicum
whole whole whole
18.8 36.4 10.3
82.3 117.0 90.0
0.3 0.3 0.2
10.8 22.2 12.4
5. Site No. 5
Eichhornia Ceratophyllum
whole whole
47.9 44.4
127.7 127.7
0.4 0.5
6.0 6.2
6. Site No. 6
Eichhornia Ceratophyllum Eichhornia
whole whole whole
57.2 65.8 165.1
171.3 324.7 468.5
0.8 0.4 4.6
6.8 9.6 38.5
1. Site No. 1 2. Site No. 2 U.S. industrial complex
D.S. industrial complex 3. Site No. 3 U.S. industrial complex In front of industrial complex
D.S. Industrial complex
aU.S.
~-
Plant
Part
Ceratophyllum
whole
Eichhornia Panicum Ceratophyllum
upstream; D.S. = downstream.
Cu
80
Sami E. Fayed& Hussein I. Abd-EI-Shafy
Table 4. Concentration of Cd, Cu, Pb, and Zn in water and sediment samples taken from Sites No. 2 and 3. Metal Concentration in Water ~g/L)
Accumulation o f Cu, Cd, and Pb by E. crassipes in the Piston Flow System
Sitea
Cd
Cu
Pb
I. Site No. 2 1.1. U.S. industrial complex 1.2. D.S. industrial complex
1.0 1.0
4.2 4.8
6.7 7.7
1.4 1.7
2. Site No. 3 2.1. U.S. industrial complex 2.2. At industrial complex 2.3. D.S. industrial complex
1.1 1.6 1.1
4.5 3.9 5.1
9.5 9.0 9.0
11.5 12.1 6.6
Zn
Metal Concentration in Sediment (/zg/g) Pb
considerable accumulation of these pollutants in the ecosystem in this area.
Cd
Cu
Zn
1. Site No. 2 1.1. U.S. industrial complex 1.2. D.S. Industrial complex
5.8 4.7
72 53
56 73
290 180
2. Site No. 3 2.1 U.S. industrial complex 2.2. At industrial complex 2.3. D.S. industrial complex
9.8 4.0 17.7
80 61 496
147 96 1800
170 140 480
aU.S. = upstream; D.S. = downstream.
Results and Discussion
Field Investigation Cu, Zn, Cd, and Pb concentrations in the plant samples are presented in Table 3. The concentration of these metals in water and sediment samples are included in Table 4. Table 5 shows that concentration factors of the metals in the sediment samples were, in most cases, much higher than those in the plant samples isolated from the same site. The higher values of metal concentration factor in the sediment might be attributed to the larger surface o f the sediment particulates and to a longer contact time with running waters. The results showed also that metal concentration in the sediment and plant samples taken downstream from the wastewater discharge points were higher than those taken upstream o f these points. This proves that aquatic plants can act as scavengers of metals from water while still maintaining a healthy status. These results may thus suggest the use o f local seasonal aquatic macrophytes, such as Eichhornia in assessing recent pollution by metals. The analysis o f the plant samples (Table 3), indicated that the aquatic ecosystem was heavily polluted by Cu at site No. 2 and by Zn at sites No. 3 and 4. Further downstream, it seems that industrialization at Site No. 5 resulted in a heavy pollution o f the aquatic ecosystem along the canal by Zn. However, higher concentrations of Zn, Cu, Pb, and Cd were detected in the plants isolated from the end of this canal (Site No. 6), indicating
The changes in Cu, Cd, and Pb concentration in water and plant samples in the experimental gutter are presented in Tables 6 and 7 respectively. Lead was not detected in the water that passed through zone 4 during the whole period of the experiment. Copper was detected in water samples taken from the same zone after the flow of 327 L of feed water, while cadmium was detected much earlier. This was reflected in the metal content of the root of the test plant isolated from zone 1 of the gutter as shown in Fig. 1, where it appears that copper and lead concentrations were higher than cadmium concentration. Because the molar ratio between metals in the water in zone 4 changed due to differences in metal removal rates in the preceding zones, metals concentration of the roots of plants isolated from this zone was of lower levels and of different order o f magnitude. Figure 2 shows that while metals concentration in the root of plants isolated from zone 1 followed the decreasing order Pb > Cu > Cd, the concentration of metals in the shoot followed the decreasing order Cd > Cu > Pb, indicating that Cd was translocated to the shoot by a higher rate than were Cu and Pb.
Accumulation o f Cu, Cd, and Pb by E. crassipes in the continuous f l o w completely mixed system In this system detention time in the container varied between 6.45 and 6.67 days. Results obtained are presented in Table 8. None o f the test metals was detected in the first 48 L o f the effluent, denoting the efficient removal of the metals by the test plant under the experimental conditions. Later on, cadmium was the first metal detected in the water o f the experimental container, indicating that cadmium had the least affinity to plant root surface. This was reflected in the relative concentrations of the test metals in the roots o f plants isolated from the container by the end o f the experiment. It was found that these concentrations were of the decreasing order Pb > Cu > Cd, the same order detected in the exposed plants in the piston flow system. The results showed also that the test metals were translocated to the plant shoot in minor concentrations. The amount of metal translocated increased with the increase in water flow through the container.
Cu, Cd, Zn, and Pb Accumulation by E. crassipes under different chemical compositions in a Batch System Effect o f metal:plant exposure ratio on metal accumulation. In this experiment, metal accumulation by the test plant from a synthetic medium (mM NaHCO3 solution)
81
Metals accumulation by aquatic macrophytes Table 5. Concentration factors (CF) of Cd, Cu, Zn, and Pb in aquatic plants and sediments in sites No. 2 & 3. Metal Concentration (ppb) Site
Ecophase
Site No. 2. Upstream industrial complex
Cd
Water Plant Eichhornia CF Panicum CF Ceratophyllum CF Sediment CF
Downstream industrial complex
1.0 300 300 200 200 500 500 5800 5800
Water Plant Eichhornia CF Panicum CF Sediment CF
Site No. 3 Upstream industrial complex
300 300 300 300 4700 4700
21000 5000 3200 762 15500 3690 72000 17142
Water Plant Eichhornia CF Sediment CF
600 545 17700 16090
6.7
52500 37500 30500 21785 47800 34142 290000 207142
12200 1820 11400 1701 11800 1761 56000 8358
1.7
7.7
89700 18687 33800 7041 53000 11042
34200 20117 194800 114588 180000 105882
4.5
10200 1324 12100 1571 7300 948
11.5
20300 4511 4300 955 80000 17777
1.1
Pb
1.4
4.8
1.1 100 91 100 91 9800 8909
Zn
4.2
1.0
Water Plant Eichhornia CF Panicum CF Sediment CF
Downstream industrial complex
Cu
9.5
64600 5617 31300 2720 170000 14782
5.1
6.6
22500 4412 494000 96862
68400 10364 480000 72727
6500 684 4800 505 147000 15473 9.0 13200 1466 1800000 200000
Table 6. Temporal and spatial changes in Cd, Cu, and Pb concentrations in water samples taken from the experimental gutter. Concentrations of Metals O~M/L) Flow after Metals Addition (L) 0 40 94 195 243 327 405 465
Zone 1 Cd
Zone 2
Zone 3
Zone 4
Cu
Pb
Cd
Cu
Pb
Cd
Cu
Pb
Cd
Cu
Pb
0.0 0.0 0.2 0.0 0.4 0.0
0.0 0.0 0.0
0.0 0.1
0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0 0.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0
0.6 0.0 0.0 1.1 0.2 0.0 0.9 0.3 0.5 0.9 0.5 1.4 0.5
0.3 0.2
0.3 0.0 0.0 0.6 0.0 0.0 0.6 0.0 0.0
0.0 0.0 0.0 0.1 0.0 0.0 0.1 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.2 0.1 1.4 0.1
0.0 0.0
82
Sami E. Fayed & Hussein I. Abd-E1-Shafy Table 7. Temporal and spatial changes in Cd, Cu, and Pb concentrations in plants isolated from the experimental gutter. Metal concentration (~M/g plant material)
Flow after Metal Addition
Zone 1
(L)
Cd
La Ra L R L R L R L R
195 243 327 465
0.00 0.02 0.41 2.63 0.40 3.92 0.89 5.14 0.99 5.58
Cu
Zone 4 Pb
0.18 0.02 0.18 0.05 0.34 0.20 5.70 6.71 0.51 0.19 6.96 8.15 0.57 0.28 12.09 14.53 0.84 0.64 16.19 24.67
Cd
Cu
Pb
1.0
~
0.8
0.6
0.03 0.09 0.02 0.25 0.08 0.93 0.19 3.81
0.23 0.56 0.26 0.70 0.31 1.58 0.35 1.92
0.07 0.24 0.07 0.22 0.06 0.48 0.09 0.60
I
0.4
71/'°
....
0.2 0.0
o--at_.C---~o._~=~ I
I 300 400 Flow, Liters of Test Water
200
aL = shoot; R = root.
and from a natural medium (Nile water) was investigated. The results obtained (Figs. 3-5) showed a positive linear relationship between metal-to-plant exposure ratio and the amount of metal accumulated by E. crassipes root, especially at the low exposure ratios. This may lead to suggest that metal accumulation by plant material is a surface phenomenon. Similar findings have been reported by Hutchinson and Czyrska (1975). The results showed also that metal accumulations from the two media, namely, the Nile water (moderately hard) and the NaHCO3 solution (no hardness) were of similar rates at the same metal-to-plant exposure ratio, indicating that moderate hardness did not interfere with metal accumulation. It was found that the plant root was able to accumulate up to 6.126 mg Cu, 5.075 mg Zn, 2.445 mg Cd, or
20-
p
I 500
Fig. 2. Metal content of Eichhornia shoots isolated from the ends of Zone 1 ( t , i , and I ) and Zone 4 ( O , / % and [~) during test water flow.
6.00 mg Pb per one gram of root, on a dry weight basis. Analysis of the exposed plants (Fig. 6) showed that the shoots carried the test metal in relatively low concentrations compared to the roots. Thus, metal translocation to the shoots took place even with cadmium and lead, which are not plant nutrients. The highest rate of translocation was shown with cadmium and the lowest was with copper. In this respect, England (1980) noticed little translocation of cadmium in water hyacinth.
Accumulation o f Cu, Zn, Cd, and Pb in combination from NaHC03 solution. This experiment was performed using solution containing a combination of Cu, Zn, Cd, and Pb at equimolar concentrations. The results obtained are compiled in Table 9 and illustrated in Fig. 7, where a linear relationship is shown between the amount of accumulated metals and the metal-to-plant exposure ratio, especially at the lower ratios. However, the results did not indicate any preferential uptake among the test metals at 24 h contact time.
Cu 0
= x
= In Nile water x In Distilledwater
5-
o
~------.-;~ ==--~.F--=-1~ 200
"1- - - P b - - ~
300 400 Ftow, Liters of Test Water
I 500 2
4
6
8
I
10
Exposure Ratio, mg Cu/g
Fig. 1. Metal content of Eichhornia roots isolated from the ends of Zone 1 ( I , &, and l ) and Zone 4 ( O , / % and C]) during test water flow.
I
12
I
1A
I
16
Root
Fig. 3. Effect of exposure ratio on metal accumulation by Eichhornia crassipes.
Metals accumulation by aquatic macrophytes
83
Table 8. Temporal changes in Cd, Cu, and Pb concentrations in water and in plant in the continuous flow mixed system. Concentration of Metals in plant ~ M / g )
Concentration of Metals in Dish Watera,/~M Time after Metal Addition (days)
Flow after Metal Addition (L)
0
0
Cd
Cu
Pb
0.00
0.00
0.00
3 7 12
19.8 48.2 80.2
0.00 0.00 0.19
0.00 0.00 0.00
0.00 0.00 0.00
18
116.8
0.61
0.52
--
24
153.4
0.85
0.42
0.45
Cd
Cu
Pb
Rb
0.00 0.02
0.16 0.16
0.02 0.05
L R L R L R
0.23 2.36 0.29 4.31 0.99 7.14
0.39 2.35 0.39 5.28 0.63 12.03
0.10 1.99 0.12 6.14 0.27 13.15
Lb
aConcentrations of metals in feed water was raised from 0.5/~M to 1 /zM after the twelfth day o f flow through of contaminated water. bL = shoot; R = root.
Cd
E
Zn
O
e x
U
-- In Nile w a t e r x In Distilled water
1D
•
= x
X
--- In Nile w a t e r ~ In Distilled w a t e r
N
0 0
I 8 Root
2 4 6 Exposure Ratio, mg Zn/g
0
2
4
6
B
Exposure Ratio,rng Cd/g Root
Fig. 4. Effect of exposure ratio on metal accumulation by Eichhornia crassipes.
By comparing the data obtained from this experiment with those obtained from the metal-to-plant exposure ratio (described above), using single metal solutions (Figs. 3-5), it seemed that at the same metal-to-plant exposure ratio Cd and Cu accumulation by the root was enhanced in the presence of the other metals (Table 10). On the other hand, Pb and Zn accumulations were at lower rates in the presence of the other test metals, 15
o ¢r
..~
Pb 12
Y 8
-
x i
4
8
12
16
Exposure Ratio,mg Pb/g
in
N i l e water
K lq DistilL-=dwater
x
20
I 24
i 28
Root
Fig. 5. Effect o f exposure ratio on metal accumulation by Eichhornia
crassipes.
especially at the higher metal-to-plant exposure ratios. Similarly, synergestic effects were previously found by Hutchinson and Czyrska (1975), who reported that cobalt and nickel uptake were increased by the presence of other metals.
Effects of chemical
characteristics o f water on C d and Pb accumulation. The results of tests No. 1 and No. 3 (Table 12), showed that the presence of EDTA in the test water greatly reduced lead accumulation by the root. However, this retarding effect of EDTA was much less displayed on cadmium accumulation, as shown in Table 11. The results of tests No. 3 and No. 4 in Tables 11 and 12 showed t h a t - a t the same level of metal-to-plant r a t i o s - t h e addition of Ca 2÷ and Mg 2÷ did not eliminate the effect of EDTA on Cd and Pb accumulation. By comparing metal accumulation in the s h o o t s - at the same level of exposure ratios-- with and without EDTA, it may be noticed that this organic chelator, at the concentration applied in this experiment, did not interfere with metal translocation to the shoot.
84
Sami E. Fayed & Hussein I. Abd-EI-Shafy Table 9. Accumulation of Cu, Zn, Cd, and Pb by E. crassipes exposed to equimolar concentrations of these metals. Root
Shoot
Exposure Ratio 0tM/g) b
Cu
Zn
Cd
A
3.71 1.89 2.80
2.895 2.895 2.565
4.740 3.196 4.419
B
6.64 6.75 5.26
4.469 4.642 3.698
C
13.14 23.69 8.07
D
27.91 38.02 62.98
Metal Added
Metals Accumulated (#M/g) Pb
Exposure Ratio (#M/g)
Metals Accumulated (#M/g) Cu
Zn
Cd
Pb
2.447 1.521 2.190
2.206 1.197 1.684
2.02 1.38 1.60
0.519 0.441 0.409
1.957 1.177 1.024
0.026 0.169 0.124
0.121 0.048 0.096
5.321 5.642 4.327
4.742 4.662 3.781
3.972 3.803 3.441
2.73 2.60 2.44
0.535 0.739 0.645
1.223 1.040 1.453
0.222 0.196 0.365
0.135 0.135 0.188
7.333 13.737 5.020
7.905 11.483 6.024
8.123 12.865 5.224
6.723 11.680 4.184
5.59 7.92 5.99
0.739 1.603 0.677
1.116 1.483 1.101
0.587 0.792 0.569
0.396 0.560 0.347
12.856 19.544 25.492
12.385 19.032 21.027
16.130 23.318 27.082
14.049 20.743 28.697
10.20 14.77 19.47
0.991 0.960 1.574
1.651 1.376 2.859
1.059 1.014 1.584
0.825 0.719 1.226
aA = 2/~M/L, B = 4 #M/L, C = 8 #M/L, D = 16 #M/L each of Cu, Zn Cd, and Pb. Final pH ranged from 6.5-6.6 bExposure ratio = amount of metal in test water in/~M divided by dry weight of exposed plant material.
Effect o f EDT A concentration on metal accumulation. Results obtained at the close metal:plant exposure ratios are illustrated in Figs. 8 and 9, where metal accumulations are compared at different EDTA concentrations. These figures showed that at 1 mg metal/L and with 7 mg/L EDTA or more, metal accumulation was greatly inhibited. This might indicate that organic ligands liable to occur in natural waters will be a competitor with plant surfaces on metallic pollutants. The effect of contact time on metal accumulation in the shoot and root are illustrated in Figs. 10 and 11, respectively. These figures show that at close exposure
ratios the percentage of the accumulated metal in the first 2 h amounted to 56°/0 for Cd and 67°70 for Pb, compared with the amounts accumulated in 24 h.
Conclusions The outcome from this study has been formulated into the following conclusions: 1. Since aquatic weeds can be potential scavengers for hazardous pollutants such as heavy metals, they
Table 10. Comparison between metals accumulation, in combination (1"*) and separate (2***) by E. crassipes. Cu
Zn Accumulation, mg/g
Accumulation, mg/g E.R.*, mg/g
1"*
0.12 0.18 0.24 0.33 0.42 0.43 0.51 0.83 1.51 1.77 2.42 4.00
0.13 0.16 0.18 0.23 0.28 0.29 0.32 0.46 0.87 0.82 1.24 1.62
Cd
2***
E.R.*, mg/g
l**
0.05 0.08 0.10 0.15 0.18 0.18 0.20 0.30 0.50 0.60 0.82 1.40
0.12 0.18 0.24 0.34 0.43 0.44 0.53 0.86 1.55 1.82 2.49 4.12
0.11 0.19 0.21 0.18 0.25 0.27 0.29 0.42 0.65 0.71 1.14 1.27
E.R. = Metal-to-plant exposure ratio *From table 4 transferred from uM metal/g into mg/g **From table 4 transferred from uM metal/g into mg/g ***From figures 1, 2 and 3.
Pb
Accumulation, mg/g
2***
E.R.*, mg/g
l**
0.08 0.12 0.16 0.23 0.29 0.29 0.36 0.58 1.04 1.22 1.67 2.76
0.21 0.31 0.42 0.59 0.75 0.76 0.91 1.48 2.66 3.14 4.27 7.08
0.17 0.24 0.28 0.43 0.53 0.52 0.59 0.91 1.45 1.81 2.62 3.04
Accumulation, mg/g
2***
E.R., mg/g
l**
2***
0.09 0.13 0.18 0.25 0.31 0.31 0.38 0.62 1.11 1.31 1.78 2.95
0.39 0.58 0.77 1.09 1.38 0.40 1.67 2.72 4.91 5.78 7.88 13.05
0.25 0.35 0.46 0.71 0.82 0.79 0.87 1.39 1.42 2.91 4.30 5.95
0.24 0.36 0.48 0.68 0.86 0.88 1.04 1.70 3.07 3.61 4.92 7.20
85
Metals accumulation by aquatic macrophytes Table 11. Accumulation of cadmium by E. crassipes after l-day exposure from media of different chemical characteristics, a Shoot
Root
Cd Removal (%)
Test No.
Exposure Ratio (mg/g)
Cd Accum. (mg/g)
Exposure Ratio (mg/g)
Cd Accum. (mg/g)
By Shoot
Bt Root
By Total Plant
1
0.691 0.737 0.772
0.026 0.047 0.036
1.020 1.121 1.528
0.809 0.792 1.045
3.7 6.4 4.7
70.3 73.1 68.4
83.0 79.5 73.1
2
0.576 0.931 0.756
0.026 0.079 0.029
0.887 2.364 1.336
0.608 1.385 0.642
4.5 8.5 3.8
69.3 58.5 48.0
73.8 67.0 51.8
3
0.620 0.582 1.117
0.013 0.012 0.480
1.158 1.723 2.609
0.380 0.410 0.785
2.1 2.0 4.3
32.8 56.8 30.1
34.9 58.8 34.4
4
0.498 0.777 0.656
0.016 0.030 0.031
1.200 2.239 1.489
0.485 0.867 0.660
3.2 3.9 4.7
58.1 38.7 44.3
61.3 42.6 49.1
aTest water volume = 1.5 L; final pH value ranged from 7.0 to 7.3.
0.6
Pb 0.Z, c" t/) X
•
02
I
0.(2
I
L
r
I
15 O
×
Cu 0.6
E
D
0.4-
t~
Cd
0.23r 0.C 0
I
1
1
4 0 2 6 Metal Accumulation by the Root.mg Metal/g Root
2
~+
Fig. 6. Metal accumulation by the shoot and root of Eichhornia crassipes: •
•
In Nile water; x
6
x In distilled water + NaHCO3.
86
Sami E. Fayed & Hussein I. Abd-EI-Shafy
I~oot
Cu ,~ Zn A Cd x Pb o
322~
Exposure ratio : 0.79-1.03 rng Pb/g Fkx~
O.
x A
~0.
O
24 ~E ~-
8
x
20
o
? 16 ~
Shoo(
1
8 A
~
•
oX 12-
A
13 o
OI
i
0
4
I
8
J
i
12
"6
i
20
I
24
EDTA Concentration, mcj/t
~
8
Fig. 9. Effect of E D T A concentration on lead accumulation by Eichhornia crassipes.
X
0
10
,
,
,
,
,
20
30
z,O
50
60
Exposure Rat/o,).tM/g
Root
Fig. 7 Metal accumulation in Eichhornia root at different exposure ratios.
Root 0.40 Root Exposure ratio 0.88-1.35 mg C d / g Iqoot
0.30
J
12
~
U
E
020
E ._O
.~" 0.20
Exposure ratio : 0.47 - 0.62 mg Cd/g
0110
Root
D
E u:~
0
:
;
t
~
E
t
I
Shoot
Shoot sure ratio : 0.4B - 0.51 rng Cd / g
~ 0.04
o
~ 0.020
0.02[
0.010 Exposure ratio • 0.39 - 0.42 mg Cd/g
OI 0
I
4
I
8
?
12
J
16
I
20
L
24
E DTA Concentration, mg/t Fig. 8. Effect of E D T A concentration on c a d m i u m accumulation by Eichhornia crassipes.
0
0
I
Shoot I
2
24 Contact Time, hours
Fig. 10. Effect of contact time on c a d m i u m accumulation by Eichhornia crassipes.
Metals accumulation by aquatic macrophytes
87
Table 12. Accumulation of lead by E. crassipes after 1-day exposure from media of different chemical compositions, a Shoot
Root
Pb Removal (°7o)
Test No.
Exposure Ratio (mg/g)
Pb Accum. (mg/g)
Exposure Ratio (mg/g)
Ph Accum. (mg/g)
By Shoot
Bt Root
By Total Plant
1
0.972 0.771 0.658
0.041 0.033 0.018
1.525 1.032 0.609
0.728 0.729 0.408
4.2 2.5 2.7
51.7 70.7 67.1
55.9 73.2 69.8
2
1.135 1.619 0.943
0.032 0.031 0.021
1.545 1.313 1.286
1.218 0.844 0.935
2.8 1.9 2.2
78.8 64.8 72.8
81.6 66.2 75.0
3
0.691 0.955 0.683
0.010 0.021 0.012
1.077 0.917 0.835
0.053 0.046 0.053
1.4 2.2 1.8
4.9 5.0 6.4
6.3 7.2 8.2
4
0.457 0.844 0.571
0.008 0.006 0.011
0.648 0.783 1.136
0.055 0.057 0.064
1.8 0.7 1.8
8.8 7.2 5.6
10.6 7.9 7.4
aTest water volume = 1.5 L; final pH value ranged from 7.8 to 7.0.
might be better dealt with through managing programs rather than eradication from the aquatic ecosystem. 2. A q u a t i c m a c r o p h y t e s s h o u l d n o t b e e x p e c t e d t o remove heavy metals successfully from organic wastewater effluents. 3. A q u a t i c p l a n t s c o l l e c t e d f r o m a r e a s p o l l u t e d b y h e a v y m e t a l s s h o u l d n o t b e u s e d as a f o d d e r f o r a n i m a l s o r as a f e r t i l i z e r .
Root 0.3C
0.2C
P Exposure ratio : 0?9 - 0.8"/rng Pblg
0.1(3
i
Root
I
Shoot 0.20
O01(
,.... Exposure ratio : 0.35 - 0.39 rng Pb/g =
Sho~ I
2 Contact Time, hours
Fig. 11. Effect of contact time on lead accumulation by Eichhornia crassipes.
Acknowledgements-This work was supported by a grant provided under the contract No. PR 3-541-3 between the United States Environmental Protection Agency and the Egyptian National Research Centre.
References
American Public Health Association/American Water Works Association (1975) Standard Methods for the Examination of Water and Wastewater, 14th ed., A P H A AWWA, Washington, DC. Cook, J. (1977) Environmental pollution by heavy metals, lnt. J. Environ. Studies. 10, 253-256. Englande, A. J. (1980) Tertiary wastewater treatment by the application of vascular aquatic plants. Municipal Wastewater Reuse News, No. 33, pp. 14-15. AWWA Research Foundation, Denver, CO. Hutchinson, T. C. and Czyrska, H. (1975) Heavy metal toxicity and synergism to floating aquatic weeds, Verh. lnternat. Verein. Limmo. 19, 2102-211. Kinkade, M. L. and Erdman, H. E. (1975) The influence of hardness components (Ca a*and Mg 2÷)in water on the uptake and concentration of cadmium in a simulated freshwater ecosystem, Environ. Res. 10, 308-313. Richert, D. A., Kennedy, V. C., Meckenzie, S. W., and Hines, W. G. (1977) A synoptic survey of trace metals in bottom sediments of the Willamette River, Oregon. Geological Survey Circular 715F. U.S. Dept. of the Interior. U.S. National Academy of Sciences (1976) Making aquatic weeds useful: Some perspectives for developing countries, National Academy of Sciences, Washington, DC. Wilson, A. L. (1976) Concentration of trace metals in river waters. A review, TR., 16. (Personal communication.) Wolverton, B. C. (1975) Water hyacinths for removal of cadmium and nickel from polluted waters. NASA Technical Memorandum TM-X-72721, National Aeronautics and Space Administration, Washington, DC. Wolverton, B. C. and McDonald, R. C. (1975) Water hyacinths and alligator weeds for removal of silver, cobalt and strontium from polluted waters. NASA Technical Memorandum TM-X-72727, National Aeronautics and Space Administration, Washington, DC. Wolverton, B. C. and McDonald, R. C. (1976), Water hyacinths (Eichhornia crassipes) for removing chemical and photographic pollutants from laboratory wastewaters. National Aeronautics and Space Administration, Washington, DC, TM-X-72731.