Bull. Environ. Contam. Toxicol. (1991) 47:448-454 9 1991 Springer-Verlag New York Inc.
~Environmental Contamination ~ar~l Toxicology
Toxicity of Nickel and Nickel Electroplating Water to the Freshwater Cladoceran Moina macrocopa C. K. Wong, P. K. Wong, and H. Tao Department of Biology, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong
Production of e l e c t r o p l a t i n g wastewater and its discharge into a q u a t i c e c o s y s t e m s have i n c r e a s e d greatly in recent years. The most important sources of electroplating wastewater pollution are dumping and spillage of r i n s e water and process solution. E l e c t r o p l a t i n g w a s t e w a t e r c o n t a i n s high levels of heavy metals such as copper, chromium, nickel and zinc. The e f f e c t s of h e a v y m e t a l s on a q u a t i c e n v i r o n m e n t s have been e x t e n s i v e l y r e v i e w e d (Mance 1987). Wastewater discharged by e l e c t r o p l a t i n g factories in Hong Kong contains high concentrations of nickel. Toxicity of nickel to aquatic organisms such as bacteria (Giashuddin and Cornfield 1979; Babich and Stotzky 1983), algae (Spencer and Greene 1981; Spencer and N i c h o l s 1983), invertebrates (Biesinger and Christensen 1972; Baudouin and Scoppa 1974; BakoricPopovic and Popovic 1977) and fish (Pickering 1974) is well-known. Among invertebrates, cladocerans are the m o s t s u s c e p t i b l e to n i c k e l t o x i c i t y (Mance 1987). Cladocerans are exceedingly important components of many aquatic ecosystems. They are major consumers of algae, and they t h e m s e l v e s are i m p o r t a n t food of aquatic invertebrates and fishes. Nickel is known to i n h i b i t the g r o w t h of f r e s h w a t e r c l a d o c e r a n s (Biesinger and Christensen 1972; Khangarot and Ray 1987). However, there is no information on the toxicity of nickel electroplating water to freshwater cladocerans. The present study investigates the effects of Ni 2+ and other components of nickel electroplating water on the survival and reproductive capacity of the cladoceran Moina macrocopa, a common inhabitant of small ponds and rice paddies in Hong Kong and Southern China. Send reprint requests to CK Wong at the above address
448
MATERIALS
AND
METHODS
The chemical c o m p o s i t i o n of e l e c t r o p l a t i n g wastewater d e p e n d s on the type of e l e c t r o p l a t i n g process used. In this study, nickel e l e c t r o p l a t i n g water (EW) was p r e p a r e d according to Wong (1984) by d i s s o l v i n g 300 g of n i c k e l sulphate (NiSO4.6H20), 45 g of n i c k e l chloride (NiCI2.6H20), 40 g of boric acid (H3B03) and 7 mL of MIX, a commercial additive containing b r i g h t e n e r and surfactant, in 1 L of d i s t i l l e d water. Stock solutions of Ni 2+ (i0,000 mg/L) were p r e p a r e d by d i s s o l v i n g 4.47 g of NiSO4.6H~O (NS) or 4.05 g of NiCI2.6H20 (NC) in i00 mL o f - d i s t i l l e d water. All chemicals u s e d in t h i s s t u d y w e r e r e a g e n t g r a d e . C o n c e n t r a t i o n s of N 2+ in EW, NS and NC were d e t e r m i n e d by atomic 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 r y w i t h a V a r i a n model AA 1475 atomic absorption spectrophotometer. A stock solution of boron ion (i,000 mg/L) was p r e p a r e d by d i s s o l v i n g 0.57 g of H3BO 3 (BA) in i00 mL of d i s t i l l e d water. A MIX solution (MIX) was p r e p a r e d by adding 7 mL of MIX to 1 L of distilled water. All stock solutions were sterilized by a u t o c l a v i n g and stored in a r e f r i g e r a t o r before use. M. m a c r o c o p a came from a continuous laboratory culture raised from a single p a r t h e n o g e n e t i c female. Cohorts of n e w b o r n (< 24 h) individuals for t o x i c i t y tests were obtained by isolating egg-bearing females from stock cultures. Twenty newborn animals, i0 in each 150 mL beaker containing i00 mL of aged (> 1 week) tap water (pH 6.5-7.0), formed the two replicates used for e a c h t e s t c o n d i t i o n . Test solutions were p r e p a r e d by adding aliquots of EW, NS, NC, BA and M ~+ X from stock solutions to each beaker. T o x i c i t y of N ion from EW, NS and NC was tested at c o n c e n t r a t i o n s of 0.25, 0.5, 1.0, 3.0, 5.0 and 7.0 mg/L. T o x i c i t y of boron ion from BA was tested at 0.25, 0.5, 1.0, 5.0, 7.0 and i0.0 mg/L. Concentrations of M I X t e s t e d w e r e 0 . 0 0 3 5 , 0.007, 0 . 0 1 4 , 0 . 0 3 5 a n d 0.07 mL/L. Test solutions were c h a n g e d every day. The number of surviving animals were counted during each change. Individuals w i t h o u t heartbeats were considered dead. Young produced during the previous 24 h were counted and discarded. Chlorella pyrenoidosa, at a c o n c e n t r a t i o n of 200,000 cells/mL, was added to the beakers to feed the animals after each water change. Surplus algae were u s u a l l y s t i l l in s u s p e n s i o n when the test solutions were changed. All beakers were kept at 25 • 2~ under a 16L:8D light cycle in a test chamber. Each t o x i c i t y test lasted the entire life span of the cohort. R e s u l t s were was recorded
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Days F i g u r e i. S u r v i v o r s h i p curves of M. marocopa in control and various concentrations of n i c k e l e l e c t r o p l a t i n g w a t e r (EW), nickel s u l f a t e (NS), nickel chloride (NC), b o r o n i o n (BA) a n d MIX. C l o s e d symbols r e p r e s e n t t r e a t m e n t s d i f f e r e n t from c o n t r o l (P < 0.05).
r e c o r d e d as the a v e r a g e n u m b e r of y o u n g per f e m a l e per day. D i f f e r e n c e among t r e a t m e n t s was first c o m p a r e d u s i n g the s i n g l e factor a n a l y s i s of variance. The D u n n e t t ' s test (Zar 1984) was then u s e d to c o m p a r e the control mean to each other treatment mean. Significance l e v e l of 0 . 0 5 w a s a d o p t e d for all s t a t i s t i c a l analyses 9
450
20
RESULTS
AND
DISCUSSION
In a d d i t i o n to nickel sulfate (NS) and nickel c h l o r i d e (NC), nickel e l e c t r o p l a t i n g water (EW) contains boric acid (BA) and MIX (Wong 1984). Effect of N 2+, b o r o n ion and MIX on the survivorship schedule of M_~. macrocopa populations is p r e s e n t e d in Fig. I. T o x i c i t y of N 2 § from EW, NS and NC increased w i t h concentration. M a x i m u m lifespan of M_~. m a c r o c o p a was r e d u c e d by m o r e than 50% at 3.00 m g / ~ or h i g h e r c o n c e n t r a t i o n s of N 2+. In the case of -N2+ from EW, longevity was s i g n i f i c a n t l y reduced at 1.00 m g / L or h i g h e r concentrations. In the case of N 2+ from NS a n d NC, significant reduction in l o n g e v i t y was d e t e c t e d at 0.50 m g / L or higher concentrations. Boron ion from BA appeared to be less toxic than N 2+. S u r v i v o r s h i p at c o n c e n t r a t i o n s of 0.25, 0.50, 1.00 and 5.0 mg/L was not significantly different from survivorship of c o n t r o l (Fig. i). Significant reduction in longevity was observed only at c o n c e n t r a t i o n s of 7.0 and i0.0 mg/L. Survivorship of M_~. m a c r o c o p a was also tested in the p r e s e n c e of d i f f e r e n t c o n c e n t r a t i o n s of MIX, ranging from 0.0035 m L / L to 0.07 mL/L. However, even at the h i g h e s t c o n c e n t r a t i o n tested in this study, MIX did not affect the longevity of M_~. m a c r o c o p a . These results r e v e a l e d that N 2+ and boron ion were the major toxic components in nickel e l e c t r o p l a t i n g water. Reproductive patterns of M. m a c r o c o p a exposed to d i f f e r e n t c o n c e n t r a t i o n s of N 2e, boron ion and MIX are p r e s e n t e d in Fig. 2. Three separate bursts of reproduction, representing three successive broods, were observed in t h e r e p r o d u c t i v e p a t t e r n of t h e control population. In g e n e r a l , f i r s t r e p r o d u c t i o n occurred after 3 to 4 days. Animals exposed to N 2+, boron ion and MIX did not reproduce later than control animals. In t h e c a s e of N 2+ f r o m EW, fecundity at c o n c e n t r a t i o n s of 0.25 and 0.50 m g / L was not s i g n i f i c a n t l y different from that of the control. S i g n i f i c a n t effect on fecundity was first d e t e c t e d at a c o n c e n t r a t i o n of 1.00 mg/L. No r e p r o d u c t i o n was r e c o r d e d at c o n c e n t r a t i o n s h i g h e r t h a n 1.00 m g / L . Results on the effect of N 2+ from NS on the fecundity of M_~. m a c r o c o p a were somewhat spurious. Fecundity was s i g n i f i c a n t l y r e d u c e d at 0.25 and 3.00 mg/L, but not at 0.50 and 1.00 mg/L. In contrast, N 2+ from NC caused no s i g n i f i c a n t changes in f e c u n d i t y at concentrations of 0.25, 0.50 and 1.00 mg/L. Animals e x p o s e d to 3.00 m g / L of N 2+ from either NS or NC lived just long enough to produce one small brood. A n i m a l s exposed to 5.00 and 7.00 mg/L of N 2+ from EW,
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Figure 2. Fecundity curves showing the average number of young per female per day for M. m a r o c o p a in control and various concentrations of n i c k e l e l e c t r o p l a t i n g water (EW), nickel sulfate (NS), nickel chloride (NC), boron ion (BA) and MIX. Closed symbols represent treatments different from control (P < 0.05). NS and NC did reproduction..
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At c o n c e n t r a t i o n s up to 5.00 mg/L, boron ion from BA had no significant effect on the fecundity of M__~. macrocopa. Reproduction appeared to stop rather abruptly at 7.00 and i0.00 mg/L. Since more than 60%
452
of the animals survived well beyond the day of first reproduction (3 to 4 days), the absence of reproduction at 7.00 m g / L was somewhat surprising. similarly, while the m a x i m u m longevity at i0 m g / L was 7 days, no r e p r o d u c t i o n was observed. These results suggested that boron ion from BA was toxic to M_~. macrocopa. MIX, which had no lethal effect on M_~. macrocopa, also appeared to have no significant effect on fecundity. T o x i c i t y of nickel to freshwater cladocerans has been studied previously. Working with the freshwater c l a d o c e r a n Daphnia ma__a~. Biesinger and C h r i s t e n s e n (1972) found that t h ~ + c o n c e n t r a t i o n which caused 50% m o r t a l i t y of the p o p u l a t i o n w i t h i n 48 h (48-h LCs~ ) was between 0.5 and i.i mg/L. Reproduction was impaired at even lower concentrations. In contrast, K h a n q a r o t and Ray (1987) reported that the 48-h LC50 of N 2+ for D__~.maqna was 7.6 mg/L. Comparison b e t w e e n results is d i f f i c u l t because there was insufficient i n f o r m a t i o n to assess the effects of e n v i r o n m e n t a l v a r i a b l e s such as water temperature, pH and water hardness. Information on o t h e r Daphnia species suggests that there may be interspecific d i f f e r e n c e s in t o l e r a n c e to N 2+ toxicity. Baudouin and Scoppa (1974) found a 48-h LC50 of 1.9 mg/L for D. hyalina. R e s u l t s of this study show that the 48-h LCs0 of N z+ for M__~.m a c r o c o p a was around 7.0 mg/L. C o m p a r i s o n with information on other freshwater organisms (Mance 1987) confirms that cladocerans are very sensitive to nickel pollution. Results of t h i s study also indicate that other components in EW, such as boron ion, are toxic to freshwater cladocerans. A l t h o u g h N 2~ is more toxic t h a n b o r o n ion a n d m a y a c c o u n t for m u c h of t h e t o x i c i t y of e l e c t r o p l a t i n g water, boron ion is toxic at high c o n c e n t r a t i o n s and may enhance the t o x i c i t y of N 2+ MIX, which is a common ingradient of e l e c t r o p l a t i n g water, was found to have no significant effect on the longevity and fecundity of M__ macrocopa. However, it must be noted that results of a previous study (Wong a n d W o n g 1991) suggest that MIX may enhance the toxicity of N 2+ to t h e g r e e n a l g a Chlorella pyrenoidosa. The composition of electroplating water depends on the type of electroplating process used. Electroplating wastewater collected from Hong Kong factories g e n e r a l l y contains heavy metals and other pollutants such as cyanide and hexavalent chromium. The combined effects of these p o l l u t a n t s on aquatic organisms and the m e c h a n i s m s of pollutant interaction are important aspects for future research.
453
Acknowledgments. The authors thank C. Wong and S.L. Lok for their help in performing some experiments. This work was supported in part by grants from the Croucher Foundation and the Shaw College Student Campus Work Scheme of the Chinese University of Hong Kong. REFERENCES Babich H, Stotzky G (1983) Toxicity of nickel to microbes : environmental aspects. A d v Appl Microbiol 8 : 9 9 - 1 4 5 Baudouin MF, Scoppa P (1974) Acute toxicity of various metals to freshwater zooplankton. Bull Environ Contam Toxicol 1 2 : 7 4 5 - 7 5 1 Biesinger KE, Christensen GM (1972) Effects of various m e t a l s on survival, growth, reproduction, and metabolism of Daphnia maqna. J Fish Res Bd Can 29: 1691-1700 Bakoric-Popovic I, Popovic M (1977) Effects of heavy metals on survival and respiration rate of t u b i f i c i d worms. Pt. i. E f f e c t s on survival. Environ Pollut 1 3 : 6 5 - 7 2 Giashuddin M, Cornfield AH (1979) Incubation study on effects of adding varying levels of nickel (as sulphate) on nitrogen and carbon mineralization in soil. Environ Pollut 1 5 : 2 3 1 - 2 3 4 Khangarot BS, Ray PK (1987) Correlation between heavy metal acute toxicity values in Daphnia magna and fish. Bull Environ Contam Toxicol 3 8 : 7 2 2 - 7 2 6 Mance G (1987) Pollution threats of heavy metals in aquatic environments. Elsevier Applied Science, New York Pickering QH (1974) Chronic toxicity of nickel to the fathead minnow. J Water Pollut Control Fed 46: 760765 Spencer DF, Greene RW (1981) Effects of nickel on seven species of freshwater algae. Environ Pollut (ser A) 2 5 : 2 4 1 - 2 4 7 Spencer DF, Nichols LH (1983) Free nickel ion inhibits growth of two species of green algae. Environ Pollut (ser A) 3 1 : 9 7 - 1 0 4 W o n g TL (1984) P r a c t i c a l E l e c t r o p l a t i n g . Tsui's Foundation Publisher, Taiwan Wong PK, Wong CK (1991) Toxicity of nickel and nickel e l e c t r o p l a t i n g w a t e r to C h l o r e l l a p y r e n o i d o s a . Bull Environ Contamin Toxicol, In press. Zar JH (1984) Biostatistical Analysis. Prentice-Hall, Inc., Englewood Cliffs, New Jersey Received March 21, 1991; accepted March 28, 1991.
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