Environ. Sci. Technol. 1982, 16, 470-473
Fate of Fenitrothion in Aquatic Microcosms and the Role of Aquatic Plantst Pearl Welnberger, Roy Greenhalgh," Richard P. Moody, and Bruce Boulton
Department of Biology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada The fate of formulated fenitrothion (10:1:1:88 v/v fenitrothion, Atlox, Aerotex, water) was monitored in both field and laboratory microcosms maintained in the light and dark. The ratios of the size of the microcosm compartments, i.e., lake water, sediment, and aquatic macrophytes and microphytes, were similar to those found in Eastern Ontario and West Quebec lakes. Initially the pesticide rapidly partitioned into all compartments, the sediment being the major sink, with aquatic biota playing only a minor role. In the light, fenitrothion was rapidly degraded in the water compartment of multicompartment microcosms with the formation of degradation products such as fenitrooxon, demethylfenitrothion, S-methylfenitrothion, carboxyfenitrothion, and a new degradation product, carboxyaminofenitrothion. In the dark, only hydrolysis products were isolated. The aquatic macrophytes Myriophyllum, Elodea, and Sagittaria accumulated both fenitrothion and its metabolites from water in light systems. In all microcosms, the aquatic macrophytes and the algal microphytes Chlamydomonas and Chlorella accumulated fenitrothion to a greater degree in the light than in the dark by factors ranging from 2- to 5-fold. Both the uptake of fenitrothion and its degradation in aquatic bodies appear to be photocatalyzed. Introduction Fenitrothion, 0,O-dimethyl 0-(4-nitro-rn-tolyl) phosphorothioate, has been widely used since 1969 to protect Canadian coniferous forests, particularly Abies balsamea and Picea glauca, from excessive defoliation by the spruce budworm, Choristoneura fumiferana (Clemens). Aerial application of the insecticide often results in its introduction into aquatic bodies either directly from spray drift or indirectly as a result of foliage washoff (1). In natural aquatic systems, fenitrothion has been reported to persist for only relatively short periods of time. The half-life in water varies from 1 to several days depending on environmental factors such as pH, light, temperature, and water quality (2-4). Several laboratory studies have been carried out on the effect of these factors on the hydrolysis of fenitrothion (5-7) and photolysis in water (8-11). However, to date little work has been reported on the role of aquatic biota on the persistence of fenitrothion (3). Plants and algae play a vital role in aquatic ecosystems as primary producers and comprise the base of aquatic food chains. They are potential sinks for insecticides and other organic pollutants. The present studies, which incorporated both laboratory and field aquatic microosms utilizing natural lake water, sediment, and aquatic plant and algal compartments, were undertaken to investigate the contribution these compartments make in the degradation of fenitrothion. Materials and Methods Chemicals. 14C ring labeled fenitrothion (S. A. 5.54 mCi/mmol) and technical fenitrothion were donated by ~~~
'Partially supported by NSERC grant A1737. *To whom correspondence should be addressed at the Chemistry and Biology Research Institute, Agriculture, Canada, Ottawa, Ontario, K1A OC6, Canada, CBRI No. 1244. 470
Environ. Scl. Technol., Vol. 16, No. 8, 1982
Sumitomo Chemical Co. Samples of Aerotex 3470 and Atlox were obtained from Texaco Canada Ltd. and Atlas Chemical Co., respectively. All organic solvents used, except chloroform and cyclohexane (Fisher), were glassdistilled pesticide grade (Caledon). Fenitrooxon [O,O-dimethyl 0-(4-nitro-m-tolyl) phosphate] (FO) (12), S-methylfenitrothion [ 0,s-dimethyl 0-(4-nitro-m-tolyl) phosphorothioate (SMF) (5), aminofenitrothion [O,O-dimethyl O-(4-amino-m-tolyl) phosphorothioate] (AF) (13),formylfenitrothion [O,O-dimethyl 0-(4-nitro-3-formylphenyl) phosphorothioate] (FF), carboxyfenitrothion [O,O-dimethyl 0-(4-nitro-3-carboxyphenyl) phosphorothioate] (CF), carboxymethylfenitrothion [O,O-dimethyl0-(4-nitro-3-(carboxymethyl)phenyl) phosphorothioate] (CMF), and carboxyethylfenitrothion [ O,O-dimethyl0-(4-nitro-3-(carboxyethyl)phenyl) phosphorothioate] (CEF) (10) were prepared according to the methods referenced and characterized by GC/MS and NMR. Microcosms. Lake water (pH 7.3-7.8) and sediment were collected from Lac Bourgeois, Gatineau Park, Quebec. Log phase algal cultures of Chlamydomonas reinhardii (4.0 X lo6 cells/mL), Chlorella pyrenoidosa (5.0 X lo6 cells/ mL), and Euglena gracilis (5.3 X lo5 cells/mL) were obtained axenic from Carolina Biological Supply Co. The flora, Elodea densa and Sagittaria spp., both monocots, and Myriophyllum, a dicot, were obtained from Wards Scientific. (a) Laboratory. Glass systems (4000 mL) housed the various microcosms studied, i.e., water, water/sediment, water/flora, and water/sediment/flora. The compartment ratios and the water volume/sediment surface area were similar to those determined in Lac Bourgeois at l-m depth in July 1977. All microcosms were maintained at 22 "C in controlled growth cabinets under a 16/8 h light/dark photoperiod. A plant load of 614 mg/L (dry weight) within the range found in natural aquatic systems (16) was employed in all experiments. (b) Field. Eight systems (1m3) open at the top were placed in Lac Bourgeois. Algae (in dialysis bags) and Elodea were suspended at ca. 20 cm (upper) and 60 cm (lower) levels. Sediment (3-4 cm) lined the bottom of the systems, some in 600-mL beakers to facilitate sampling. After allowing each system to equilibrate for 5 days, they were sprayed with formulated fenitrothion (fenitrothion, Atlox, Aerotex, water; 10:1:1:88 v/v) in the early morning of a sunny day. During the experiment the water temperature varied from 19 to 23 "C. Water, plant, algae, and sediment samples were collected at various time intervals up to 28 days posttreatment. The water (1L) was sampled at 20- and 60-cm depths, filtered through Celite, and then extracted with chloroform (3 X 100 mL). After passing through anhydrous sodium sulfate, the chloroform extracts were stored at -10 "C,and the extracted water was frozen. Plants were blotted dry and stored at -10 "C. From each field system, seven samples of moist sediment (50 g wet weight) were taken at each sample time, five of which were used to determine the moisture content and two of which were kept frozen until analyzed.
0013-936X/82/0916-0470$01.25/0
0 1982 American Chemical Society
A LIGHT
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Flgure 1. Absorption and desorption of Aerotex formulated fenltrothlon by chlorella (5.0 X loe ceils/mL) in lake waterlalgae laboratory system at 22 OC.
Analytical Procedures. (a) Lake water. The chloroform extracts (300 d) were taken to dryness on a rotary evaporator and the residues dissolved in acetone (5 mL) for analysis by GC (nonpolar fraction). The extracted water samples were lyophilized, and the residues were dissolved in methanol (1 mL) and alkylated with ethereal diazoethane for 15 min at room temperature. After removal of excess diazoethane and ether, the solution was made up with acetone and analyzed by GC (polar fraction). (b) Plant and Algae. Samples were blended with ethyl acetate (30 mL) for 3 min and filtered through Celite. After reextraction of Celite and debris, the combined filtrates were analyzed by GC (3). ( c ) Sediments. The multiple-solvent extraction procedure reported by Takimoto et al. (15) was followed. The recovery of fenitrothion was greater than 91% in water (0.01 ppm), algae and plants (0.05 ppm), and sediment (0.02 ppm). The recoveries of the derivatives of fenitrothion were >84% a t 0.05 ppm, but the AFID responses were not as great as that of the parent compound. Duplicate analyses were conducted, and the compounds were quantitated with authentic external standards. Instrumentation. Routine analyses were carried out with a Pye gas chromatograph Model 104 fitted with an alkali flame ionization detector (RbCl annulus). Separations were effected on a 1.52 m X 4.25 mm i.d. glass column packed with 4% SE-30/6% QF-1coated on 80-100 mesh Gas Chrom Q. With a carrier gas flow of 40 mL/min of nitrogen and a column temperature 218 OC, fenitrothion had a retention time of 5.85 min, and the relative retention times of AF, FO, SMF, and CMF were 0.74,1.1, 1.72, and 2.16, respectively. Degradation products were isolated by high-pressure liquid chromatography (HPLC) with a Waters M-6000 pump, a 52 cm X 0.19 cm i.d. 10 pm RP-18 column and an Altex fixed dual wavelength UV detector Model 152 (280 nm). The eluting solvent (acetonitrile/water, 6040), flowing at 2.0 mL/min, gave a retention time of 28 min for fenitrothion and relative retention times of 0.25 and 0.74, respectively, for SMF and CMF. The derivatives were characterized by proton nuclear magnetic resonance (NMR), measured on a Varian T-60 spectrometer (CDC13,Me4Si internal standard), and mass spectra (GC/MS), determined with a Finnigan 3100 GC/MS (E1 mode) coupled to a D6000 data acquisition system. Results and Discussion
Lac Bourgeois, Quebec, is typical of the small lakes and large ponds found in West Quebec and East Ontario (16).
Flgure 2. Degradation of ["C]fenitrothion (10ppm) in waterlplant (Nodea) laboratory microcosms at 22 'C: (A) light (5000 lux, 16/8 h, photoperlod); (B) dark.
Table I. Residue Levels of Fenitrothion and Its Mdtabolites in Aquatic Plants Exposed to Fenitrothion (10ppm) time, days speciesb
5 10
14
Sag Myr Elo Sag Myr Elo Sag Myr Elo
residues, pg/g dry weighta F FO SMF MNP 234.77 216.80 285.37 187.22 212.05 344.23 225.88 132.50 188.77
0.72 13.93 2.04 4.61 53.23 2.01 4.69 42.70 3.40
2.40 7.25 0.81 3.69 12.47 3.46 3.99 16.00 2.88
12.88 34.44 4.56 19.15 28.56 6.54 31.40 21.50 16.37
a F, fenitrothion; FO, fenitrooxon; SMF, S-methylfenitrothion; MNP, 3-methyl-4-nitrophenol. Sag, Sagittaria; Myr, Myriophyllum; Elo, Elodea.
The size of the various compartments (i-e.,water, sediment, and macro- and microphytes) in the lake were taken as representative of natural aquatic systems and were used for establishing the size of the compartments in the multicomponent microcosms. In laboratory studies, Aerotex/Atlox formulated [14C]fenitrothion (10 ppm) mixed rapidly throughout the water compartment. Intercompartmental equilibrium was also rapid as shown in Figure 1for a water/algae system, where the uptake of [14C]fenitrothionby Chlorella was virtually complete in 4 h. On transfer of the algae to fresh lake water, the 14Cmaterial was rapidly desorbed. The bioconcentration factor (BCF) was estimated as 417 X for this system. In a water/plant microcosm, Elodea densa absorbed the major amount of [14C]fenitrothionby day 2 in both light and dark systems (Figure 2). However, the amount taken up in the light system was greater than that in the dark by a factor of 4. The bioconcentration factors for the plants were 76X and 24X, respectively, for the light and dark systems after 1day. The 14Cactivity in the water compartment was divided into nonpolar (e.g., fenitrothion) and polar (e.g., derivatives) fractions by extraction into chloroform. The nonpolar fraction disappeared rapidly in light systems ( t l 1 2= 6.5 days) but more slowly in the dark ( t i l 2 = 25 days). In a water/plant microcosm, with Myriophyllum, Sagittaria, and Elodea in a 1:l:l ratio for a plant load of 614 mg/L, fenitrothion (10 ppm) was rapidly taken up from the water (Figure 3). The plants were analyzed for fenitrothion and its derivatives (Table I). By day 14, the fenitrothion content in the plants was lower than a t day 5 but higher than in the water compartment. The levels Environ. Sci. Technol., Vol. 16,No. 8, 1982 471
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Figure 5. Fenitrothion concentration vs. time in the autotrophic algae, Chlorella and Chlamydomonas , and the heterotrophic alga, Euglena , in field microcosms: (A) natural light condition; (B) dark.
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Figure 3. Fenitrothion concentration vs. time in Sagiftaria, Myriophyllum, and Elodea in lake waterlalgae laboratory microcosms exposed to daylight at 22 OC. A
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Flgure 6. Fenitrothion concoentrations vs. time In Elodea canadensis held in the upper (10-36 cm) and lower (36-60 cm) zones of the water column of field microcosms: (A) natural light; (B) dark.
Figure 4. Residue levels of fenltrothion In the sediment compartment of field microcosms: (A) natural light; (B) dark. Sediment washed with water and then blended wjth methanol.
of the derivatives fenitrooxon, S-methylfenitrothion, and 3-methyl-4-nitrophenolwere highest in Myriophyllum. In Sagittaria and Elodea the major derivative found was the cresol, while in Myriophyllum fenitrooxon predominated after 14 days. It is assumed that the plants may also accumulate the derivatives from the water compartment as well as forming them in situ. The bioaccumulation ratios for fenitrothion after 5 days ranged from 370 to 488X for the three plant species. Laboratory microcosms were scaled up to 1 m3 field models, retaining the same surface areas/volume ratio for the field studies. The formulated fenitrothion (equivalent to 10 ppm total volume) was applied to these multicompartment field systems by hand sprayer. In the lake, mixing in the water column occurs by the combined effects of thermal and wind-induced currents, and in these experiments 24 h elapsed before the water comphrtrpent reached equilibrium as measured by the fepitrothion concentration at 20- and 60-cm depths. This suggests that neuston (surface living organisms) may be exposed ini'tidy to relatively toxic concentrations of the pesticide formulation following spraying (17). The t l I zfor fenitrotbion in the water compartment of field models was about 1 day in the light. The main sink in the multicompartment field system (plants/algae/sediments/lakewater) was the sediment. Fenitrothion rapidly equilibrated throughout the com472
Environ. Scl. Technol., Vol. 16, No. 8, 1982
partments, the amount in the sediment being less in the light system than the dark, presumably due to its greater rate of degradation in the water compartment (Figure 4). The amount of fenitrothion absorbed by the three species of algae in the field models is shown in Figure 5. The heterotrophic alga, Euglena, took up negligible amounts of fenitrothion as compared to the two autotrophic algae Chlamydomonas and Chlorella, which showed twice the accumulation in the light than in the dark. Elodea absorbed fenitrothion from water more slowly; again the amounts in the light systems were approximately 3 times those in the dark systems (Figure 6). A material balance of the field model, 2 days postspray gave 8246% accountability of fenitrothion as compared to 98% for the laboratory microcosm. In general, the results of laboratory and field studies suggest a light-energized active-uptake mechanism by plants and algae for the accumulation of fenitrothion from water. This does not rule out the possibility of passive uptake, since light-induced changes in algal lipid composition occur rapidly (18) and could affect the partition equilibrium of fenitrothion. The partitioning into cell lipids is consistent with the high levels of fenitrothion found in algae, since fenitrothion is lipophilic (Kow = 3800 (19)),and lipids comprise 39% of the cell dry weight of Chlorella (18). In the microcosms maintained in the light, the derivatives 3-methyl-4-nitropheno1, 5'-methylfenitrothion, fenitrooxon, carboxyfenitrothion, and dimethylphosphorothioic acid were found in the water compartment. In addition a new derivative was isolated, namely carboxy-
Environ. Sci. Technol. 1982, 16, 473-479
(6) Zitko, V.; Cunningham, T. D. “Fenitrothion, Derivatives and Isomers: Hydrolysis, Absorption and Biodegradation”; Fish Res. Board Can. Tech. Rept. 458, Environment Canada, St. Andrews, N. B., 1974. (7) Greenhalgh,R.; Dhawan, L.; Weinberger,P. J. Agric. Food Chem. 1980,28, 102. (8) Brewer, D. G.; Wood, G.; Unger, I. Chemosphere 1974,3, 91. (9) Okhawa, H.; Mikami, N.; Miyamoto, J. J. Agric. Biol. Chem. 1974, 38, 2247. LO) Greenhalgh, R.; Marshall, W. D. J. Agric. Food Chem. 1976, 24, 708. 11) Miyamoto, J. “Fenitrothion: the long-term effects of its use in forest ecosystem”; Roberts, J. R., Greenhalgh, R., Marshall, K., Eds.; NRCC No. 16073,1977, Envirqnmentd Secretariat, National Research Council Ottawa, Canada. 12) Marshall, W. D.; Greenhalgh, R.; Batora, V. Pestic. Sci. 1974, 5, 781. (13) Forbes, M. A.; Wilson, B. P.; Greenhalgh,R.; Cochrane, W. Bull. Environ. Contam. Toxicol. 1975, 13, 141. (14) Wetzel, R. G. “Limnology”;Saunders: Philadelphia, PA, 1975. (15) Takimoto, Y.; Hirota, M.; Inui, H.; Miyamoto, J. J . Pestic. Sci. 1976, 1 , 831. (16) Dickman, M.; Johnson, M. Can. Field Naturalist, 1975,89, 361. (17) Moody, R. P.; Weinberger, P.; Greenhalgh, R.; Massalski, A. Can. J . Bot. 1981,59, 1003. (18) Nichols, B. W. Biochirn. Biophys. Acta 1965, 106, 274. (19) Greenhalgh, R. “A screen for the relative persistence of lipophilic organic chemicals is aquatic ecosystems”;Roberta, J. R., M. F. Mitchell, M. F., Bollington, M. J., Ridgeway, J. M., Eds.; NRCC No. 18570, 1981, Environmental Secretariat, National Research Council, Ottawa, Canada.
aminofenitrothion [O,O-dimethylO-(4-amino-3-carboxyphenyl) phosphorothioate] from the polar fraction of the water compartment in the field study. It was characterized by the mass spectrum of its methyl ester, with base peak m/z 125 and other prominent ions at 134,150,79,93,109, 106,182,and 291 (parent) and had a relative retention time of 1.63 to fenitrothion on GC. In the dark systems, only 3-methyl-4-nitrophenoland dimethylphosphorothioic acid were isolated. These results indicate that degradation of fenitrothion in water is photocatalyzed and is oxidative in nature. Summarizing, in both field and laboratory systems, the uptake of fenitrothion from water by micro- and macrophytes was rapid. Although polar derivatives were found in plants, they could have resulted from phytodegradation or have been sequestered from the ambient water, thus uptake may be active or passive. In d cases, light had the effect of increasing the uptake of fenitrothion from water by both macro- and microphytes. Given the plant loads found at a 1-m depth in a representative lake, aquatic biota represent only a small proportion of the total environmental sink. However, the ability of aquatic biota to absorb xenobiotics, particularly those with high KOw, could constitute a potential environmental hazard. Literature Cited (1) Symons, P. E. K. C SIR Res. Rev. 1977,68, 1. (2) Kodama, T.; Kuwatsuka, S. J . Pestic. Sci. 1980, 5, 351. (3) Moody, R. P.; Greenhalgh, R.; Lockhart, L.; Weinberger, P. Bull. Environ. Contam. Toxicol. 1978, 19, 8. (4) Eidt, D. C.; Sundaram, K. M. S. Can. Entomol. 1975,107, 735. ( 5 ) Kovacicova, J.; Batora, V.; Truchlik, S. Pestic. Sci. 1973, 4, 759.
Received for review April 29,1981. Revised manuscript received January 27, 1982. Accepted April 19, 1982.
Influence of Bromide and Ammonia upon the Formation of Trihalomethanes under Water-Treatment Conditions Tieu V. Luong, Chrlstophgr J. Peters, and Roger Perry’ Public Health and Resource Engineering Section, Imperial College of Science & Technology, London SW7 2BU, United Kingdom
A detailed quantitative study of the effects of bromide and ammonia upon the trihalomethane balance obtained when water is chlorinated under varying conditions is described. Experiments at a chlorine dose of 2 and 8 mg L-’ utilizing waters having total organic carbon (TOC) contents of 2.5 and 12.7 mg L-’ demonstrated the significance of these parameters and bromide (0-2000 pg L-l) on the overall reaction process. Trihalomethane distribution is principally dependent on the bromide concentration. An outline kinetic interpretation of the data is presented, and factors influencing the consumption of bromide and free chlorine are evaluated. The effect of ammonia (0.5 mg L-l, NH,-N) upon trihalqmethane formation under breakpoint Chlorination conditions was investigated. Introduction
Previous work in this laboratory (1,2)established, with the development of specific analytical procedures, the presence of organochlorine intermediates of the haloform reaction. These were found to be relatively stable a t ambient temperature although they rapidly broke down to produce dissolved chloroform upon increasing pH, thus 0013-936X/82/0916-0473$01.25/0
indicating the presence of an active trichloroacetyl group (CC1,CO). Subsequent hydrolytic attack on such a group made up the final stage of the haloform reaction. The implications in water-treatment practice are important in terms of both the unknown health effects of such intermediates, which at low pH make a substantial contribution to total chloroform, and the potential even in the absence of chlorine for additional chloroform production during water distribution. Emphasis has recently centered on establishing the source of bromine present in the trihalomethanes, where contrary to initial expectation, there is little evidence to support the view that bromine impurity in the chlorine used for disinfection is a prime source involved. Indeed, indications are that organic bromine originates principally from the inorganic bromide in the raw water that, following rapid oxidation by chlorine, is made available for bromination reactions (3). Few data are presently available regarding bromide levels in source waters, although a recent limited survey (4) revealed that all sources relating to London’s water supply contained bromide ranging in concentration between 50 and 120 pg L-l, with ground waters generally containing lower levels than surface waters.
0 1982 American Chemical Society
Environ. Sci. Technol., Vol. 16, No. 8, 1962 473
