18 Fate of Chemical Insecticides in Aquatic Environments
Chemical and Biological Controls in Forestry Downloaded from pubs.acs.org by MACQUARIE UNIV on 02/16/19. For personal use only.
Forest Spraying in Canada K. M. S. SUNDARAM, P. D. KINGSBURY, and S. B. HOLMES Forest Pest Management Institute, Canadian Forestry Service, Environment Canada, 1219 Queen Street East, Sault Ste. Marie, Ontario, P6A 5M7, Canada
The environmental behavior of some forestry insecticides in aquatic systems was studied under controlled conditions in laboratory model ecosystems and in forest streams following experimental stream injections or operational forest spraying. Insecticides studied were representative of organophosphorus and carbamate groups. In aquatic model systems consisting of sediment and natural water, the mobility of the chemicals was usually from water to sediment even though the insecticides studied were very different in chemical structure. Results indicated that adsorbed insecticides were lost primarily due to microbial action. Studies in stream ecosystems showed that the distribution and fate of insecticide residues varied with physicochemical properties of the material, additives present in tank mixes, mode of application, stream discharge and other site conditions. Disappearance of residues from stream waters was rapid due to downstream transport and dilution, movement into other substrates and chemical processes. Stream sediments, aquatic plants, fish and aquatic invertebrates accumulated residues to varying extents and showed a wide range of retention times with different insecticides under different exposure conditions. Chemicals have been an important means of c o n t r o l l i n g f o r e s t i n s e c t pests i n Canada f o r the past four decades. They have been used to l i m i t the impact of some of the most d e s t r u c t i v e f o r e s t pests, such as spruce budworms (Choristoneura spp.), on f o r e s t r e sources e s s e n t i a l to the production of f i b r e and other f o r e s t r y products. With growing demand f o r these products, pest c o n t r o l
0097-6156/ 84/0238-0253507.00/ 0 © 1984 American Chemical Society
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chemicals, because of t h e i r e f f i c a c y and economy, w i l l continue to be our primary weapon of defense against i n s e c t pests and t h e i r usage w i l l c o n s t i t u t e an i n t e g r a l part of the current c o n t r o l strategies. In order to evaluate the p o t e n t i a l hazards chemical i n s e c t i c i d e s pose to f o r e s t environments, i t i s e s s e n t i a l that adequate and r e l i a b l e research data be generated on t h e i r environmental chemistry ( d i s t r i b u t i o n , p e r s i s t e n c e , movement, metabolic degrada t i o n , t o x i c i t y , fate, e t c . ) . This paper gives a b r i e f account of some laboratory and f i e l d research a c t i v i t i e s c a r r i e d out at the Forest Pest Management I n s t i t u t e , Canadian F o r e s t r y Service to meet t h i s requirement. Using two chemical i n s e c t i c i d e s which are e x t e n s i v e l y used now i n f o r e s t insect c o n t r o l programs i n Canada viz aminocarb [Trade name, M a t a c i l ; 4-dimethylamino-m-tolyl Nmethylcarbamate] and fenitrothion [0,0-dimethyl 0-(3-methyl-4n i t r o p h e n y l ) phosphorothioate], studies conducted at the I n s t i t u t e to e l u c i d a t e the environmental behavior and fate of f o r e s t r y i n s e c t i c i d e s i n general w i l l be discussed. M a t e r i a l s and Methods Two research programs were conducted to examine the fate of amino carb and f e n i t r o t h i o n i n s e c t i c i d e s i n aquatic environments. In laboratory experiments, the d i s s i p a t i o n of these chemicals i n simple model ecosystems were s t u d i e d . In the second experiment, the fate and p e r s i s t e n c e of these two chemicals were studied i n f o r e s t streams f o l l o w i n g a semi-operational spray program i n New Brunswick i n 1982. Laboratory Studies on I n s e c t i c i d e Degradation. Degradation i n n a t u r a l waters: Stream water (pH 6.0) and sediment (organic con tent 36%) were taken from a small shallow stream (depth oa 20 cm, width oa 1.5 m) i n the Goulais River watershed, a mixed c o n i f e r deciduous f o r e s t area, oa 50 km northeast of Sault Ste. Marie, Ont., Canada. Two degradation studies i n d u p l i c a t e (one f o r amin ocarb and another f o r f e n i t r o t h i o n ) were set up according to Sundaram and Szeto (1). Aminocarb and f e n i t r o t h i o n (100 ug/L i n acetone) were added s e p a r a t e l y to 1000 mL a l i q u o t s of s t e r i l i z e d (Ameco S t e r i l i z e r 1 h) and u n s t e r i l i z e d stream water i n e i t h e r open or c l o s e d 1500 mL Erlenmeyer f l a s k s . The l a t t e r were sealed with polyethylene snap caps which were removed once a day for about 1 min. to allow a i r exchange. The f l a s k s were incubated at 15 ± 0.2°C i n an environmental chamber. U n f o r t i f i e d water samples, t r e a t e d s i m i l a r l y , served as c o n t r o l s . A r t i f i c i a l light (400 W multivapor discharge lamps) with a photoperiod of 16 h l i g h t and 8 h dark was used during i n c u b a t i o n to simulate sun l i g h t . At designated i n t e r v a l s of time, a l i q u o t s of the c o n t r o l , s t e r i l i z e d (open and c l o s e d f l a s k s ) and u n s t e r i l i z e d (open and closed f l a s k s ) water samples were c o l l e c t e d , the pH was adjusted to oa 7 by Na2C03 (aq.), solvent extracted (3 χ 50 mL p e s t i c i d e
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grade C H 2 C I 2 ) , passed through a Na2S(>4 column, flash-evaporated gently to dryness, d i s s o l v e d i n C5H5 and analyzed only f o r the a c t i v e i n g r e d i e n t s ( A l ) using g a s - l i q u i d chromatography (GLC). P a r t i a l and f u l l y demethylated aminocarb as w e l l as aminocarb phenol, as metabolites i n aminocarb f l a s k s , and demethylated (par t i a l and complete) f e n i t r o t h i o n , a m i n o - f e n i t r o t h i o n , and n i t r o c r e s o l i n f e n i t r o t h i o n f l a s k s were i d e n t i f i e d as breakdown prod u c t s . None of the metabolites were q u a n t i f i e d . No GLC responses corresponding to the a c t i v e m a t e r i a l s were found i n the c o n t r o l flasks. D i s s i p a t i o n i n stream water with sediment: In a concurrent study, a s e r i e s of 120, 100 g a l i q u o t s of coarsely s i f t e d stream sediment were placed i n 500 mL Erlenmeyer f l a s k s c o n t a i n i n g 200 mL of stream water each. One h a l f of the samples, i . e . , 60 f l a s k s , were autoclaved as before i n an Ameco s t e r i l i z e r f o r 1 h. After they were cooled to room temperature, a l l samples i n c l u d i n g the 60 non-autoclaved samples were separated i n t o two sets (20 autoclaved + 20 non-autoclaved f o r each s e t ) and one set was f o r t i f i e d with aminocarb and the other with f e n i t r o t h i o n i n acetone to a l e v e l of 100 ppb (30 yg/ 300 g) and incubated i n an environmental chamber as described above. The remaining 40 f l a s k s served as c o n t r o l s for both experiments. Samples of both the autoclaved and the nonautoclaved water and sediment i n open and closed f l a s k s as w e l l as c o n t r o l samples were analyzed f o r the a c t i v e i n g r e d i e n t s 1.0 h a f t e r f o r t i f i c a t i o n (zero time) and t h e r e a f t e r at i n t e r v a l s of time up t o 75 h.. E x t r a c t i o n , clean-up and a n a l y s i s of water and sediment: At the end of incubation, the e n t i r e water sample i n each f l a s k was f i l t e r e d under a s p i r a t i o n through Whatman No. 1 f i l t e r paper i n a Buchner funnel. The f i l t e r paper was l a t e r extracted along with the corresponding sediment. Each f i l t r a t e was q u a n t i t a t i v e l y t r a n s f e r r e d i n t o a 500 mL separatory funnel and repeatedly ex t r a c t e d with CH2CI2 a f t e r a d j u s t i n g to pH 7 as before and analyzed by GLC (2^ _3). A l i q u o t s (40 g) of sediment samples from each f l a s k were extracted i n a S o r v a l l homogenizer using e t h y l acetate (2 χ 150 mL) as the s o l v e n t . The pooled e x t r a c t s were concen t r a t e d to 40 mL (1 mL = 1 g) using a B u c h i i Rotovapor. The ex t r a c t s (1 g equivalents) a f t e r passing through Na2S04 were cleaned (2^, 3) using n e u t r a l charcoal (Nuchar S N ) - c e l l u l o s e (Whatman C F l l ) (4:10, w/w, 3 cm length) mini columns ( F i s h e r 13-678-8) topped with Na2S04« The columns were eluted with 35 mL of e t h y l acetate: toluene (1:3) ( f e n i t r o t h i o n ) or 35 mL of CH30H:EtOAc (1:4) (amino carb). The eluates were concentrated under reduced pressure and f i n a l l y brought to a known volume under a stream of dry N2 and stored at 4°C u n t i l a n a l y s i s by GLC. A Hewlett-Packard 5710A GC/NPD was used f o r both aminocarb and f e n i t r o t h i o n residue a n a l ysis. The GC conditions were:
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Detector temp: I n j e c t o r temp: Oven temp: R.T. (Min.): Column:
250°C H2 flow r a t e : 4 mL/min. 200°C A i r flow r a t e : 70 mL/min. 180°C He flow rate: 35 mL/min. aminocarb 3.5; f e n i t r o t h i o n 5.0 1.2 m χ 4 mm glass column packed with 1.5% 0V-17 + 1.95% OV-210 on Chromosorb W, H.P., 80/100 mesh
Natural water (pH 6.0) and sediment (organic content 36%) used i n t h i s study were f o r t i f i e d with both the i n s e c t i c i d e s and subsequently analyzed by the described methods. No response that i n t e r f e r e d with the d e t e c t i o n of a c t i v e i n g r e d i e n t s was found i n any of the untreated c o n t r o l s during i n c u b a t i o n . The r e c o v e r i e s for water were 93 ± 4% at 400 ppb and 97 ± 7% at 20 ppb; f o r sed iment they were 86 ± 6% and 91 ± 9%, r e s p e c t i v e l y , at the same f o r t i f i c a t i o n levels. The minimum d e t e c t i o n l i m i t (MDL) f o r both i n s e c t i c i d e s was 0.1 ppb i n water and 10 ppb i n sediment (as sampled). Except demethylated f e n i t r o t h i o n , a l l other metabolites found i n water i n the e a r l i e r study, were also i d e n t i f i e d i n sediments for both the i n s e c t i c i d e s . Amino-fenitrothion, n i t r o c r e s o l and monodemethylated aminocarb (MA) were most frequent compared to other metabolites. F i e l d Studies i n Forest Streams. I n s e c t i c i d e treatments: The f a t e and p e r s i s t e n c e of f e n i t r o t h i o n and aminocarb were studied i n 1982 i n small headwater trout streams w i t h i n the N i p i s i g u i t R i v e r watershed near Popple Depot, New Brunswick. Three study streams were treated with d i f f e r e n t i n s e c t i c i d e tank mixes, r e c e i v i n g two a p p l i c a t i o n s at a 6 to 8 day i n t e r v a l sprayed by Agcat or Agtruck a i r c r a f t equipped with M i c r o n a i r spray emission systems. Each stream l a t e r received a point source i n j e c t i o n by hand-held sprayer of the same i n s e c t i c i d e tank mix which had been p r e v i o u s l y a p p l i e d to i t from the a i r . Two f e n i t r o t h i o n and one aminocarb tank mixes were s t u d i e d , all containing Triton X-100 (p-tert-octylphenoxynonaethoxyethanol), a nonionic s u r f a c t a n t , and water. One f e n i t r o t h i o n tank mix also contained c y c l o s o l , a petroleum d i s t i l l a t e . The percent ( v o l . ) composition of d i f f e r e n t i n g r e d i e n t s present i n the tank mixes, the streams sprayed with them and t h e i r discharge, and dates and rates of a p p l i c a t i o n are summarized i n Table I. A e r i a l a p p l i c a t i o n s were conducted by Forest P r o t e c t i o n L t d . (FPL), the crown c o r p o r a t i o n r e s p o n s i b l e for budworm spraying i n New Brunswick. Spotter planes were used to ensure that spray l i n e s were followed and the streams and sampling s i t e s r e c e i v e d good coverage. Stream i n j e c t i o n s from the ground were a p p l i e d oa 100 m upstream from the s e l e c t e d sampling s i t e s using a Micron ULVA Sprayer". According to the manufacturer's specifications, t h i s u l t r a - l o w volume a p p l i c a t o r i s capable of producing a narrow l!
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spectrum of droplet s i z e s with a VMD (volume-median diameter) of 70 μπι. Treatment rates were adjusted by d i l u t i n g the tank mixes with water so that the residue l e v e l s obtained i n stream water were higher than i n normal a e r i a l a p p l i c a t i o n s and v a r i a t i o n s between streams with d i f f e r e n t discharges were reduced. Details of the i n s e c t i c i d e formulations and a p p l i c a t i o n s are summarized i n Table I. Residue sampling, p r e p a r a t i o n and a n a l y s i s : Water, aquatic moss, stream insect and f i s h samples were c o l l e c t e d from some or a l l study streams f o r residue a n a l y s i s a f t e r each i n s e c t i c i d e treatment. In l i g h t of the dynamic nature of the systems studied and the r e l a t i v e l y small treatment areas, sampling was concen t r a t e d i n t o the i n i t i a l 24 hours a f t e r i n s e c t i c i d e a p p l i c a t i o n s . Water samples (oa 1 L) were c o l l e c t e d by immersing clean mason jars to a depth of 1 cm i n midstream. Water samples were extracted immediately with dichloromethane as described e a r l i e r . Moss samples (oa 300 g) were c o l l e c t e d from rocks on the stream bed and packed i n polyethylene bags a f t e r gently squeezing out ad sorbed water. Samples were l a t e r cut i n t o small pieces, thor oughly mixed i n a Hobart bowl chopper and stored i n sealed p l a s t i c bags at -20°C u n t i l analyzed. Samples ( k2: 3
k
Adsorbate + Adsorbent ^ ( P e s t i c i d e ) (Sediment)
l Adsorbate:Adsorbent k2 Microbes (Aquatic Environment) M e t a b o l i t e ( s ) + Adsorbent
The magnitude of k i depends upon the nature of the chemical under investigation. In the present study, i t i s evident that f e n i t r o t h i o n has a higher degree of adsorption (k^ >> k2) compared to aminocarb although i t i s claimed that aminocarb i s s t r o n g l y adsorbed to s o i l p a r t i c l e s 09). In a c i d i c waters (pH 6.0), aminocarb e x i s t s as a protonated c a t i o n
H CH
3
and under such c o n d i t i o n s , the moiety w i l l be less l i p o p h i l i c , consequently the adsorptive processes w i l l be less s i g n i f i c a n t . The present study demonstrates t h i s d i f f e r e n c e . In conclusion, water/sediment model studies suggest that the d i s s i p a t i o n pathways for aminocarb and f e n i t r o t h i o n would be prima r i l y v i a v o l a t i l i z a t i o n and m i c r o b i a l a c t i o n as s c h e m a t i c a l l y represented i n Figure 5. F i e l d Studies. pre-spray water
F e n i t r o t h i o n was samples, although
detected i n ppb l e v e l s i n a l l i t i s impossible to t r a c e the
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Volatilization-*co-distillation photolysis
MA + AM + AP
Sediment/microbes
Sediment:
MA + AM + AP -
metabolites
Ring h y d r o x y l a t i o n + oxidation + jD-aminophenol (?)
Hydroxy compds.
I n o r g a n i c compds. ( C 0 + NH 4 + H 0) +
2
2
C r e s o l + AF + demethylated AF and f e n i t r o t h i o n ( ? ) + d e r i v a t i v e s o f H3PO4 (?)
Volatilization-*co-distillation photolysis v
FENITROTHION Sediment/microbes
AF + C r e s o l -
•Sediment:
metabolites
Microbial
Inorganic
degradation
compds. +
3
(C0 , NH4, H 0 + PO4") 2
2
F i g u r e 5. D i s s i p a t i o n pathways o f aminocarb and f e n i t r o t h i o n i n water/sediment model systems.
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exact source. I t may have r e s u l t e d from a e r i a l d r i f t from operat i o n a l sprays i n adjacent areas, or have r e s u l t e d from long-term p e r s i s t e n c e at low l e v e l s i n the f o r e s t ecosystem due to extensive use over the past two decades. Previous studies (10-13) have r e ported such a phenomenon. The disappearances of f e n i t r o t h i o n and aminocarb from stream waters are documented i n Table I I . Following a e r i a l spraying, peak l e v e l s ranging from 0.10 to 2.26 ppb were found i n 1 h samples. Residues decreased r a p i d l y with time, probably p r i m a r i l y due to studies with more than 85% of the amount found at 0.5 h post-spray l o s t w i t h i n 5 h. The h a l f - l i v e s (t±) were below 1 h. There i s no known explanation f o r the increases i n concent r a t i o n s of f e n i t r o t h i o n during the l a s t sampling period (24 h) a f t e r some a e r i a l treatments. The very rapid loss of aminocarb from Portage Brook f o l l o w i n g a e r i a l a p p l i c a t i o n s r e f l e c t s i t s r e l a t i v e l y high stream discharge compared to the other streams. It i s d i f f i c u l t to deduce whether the a d d i t i v e s present i n the formulations studied had s i g n i f i c a n t l y influenced the p e r s i s t ence of the i n s e c t i c i d e s i n stream water, because the system was so dynamic such subtle points were d i f f i c u l t to evaluate. U s u a l l y aminocarb and f e n i t r o t h i o n are hydrophobic i n nature, while T r i t o n X-100 i s h y d r o p h i l i c because of i t s hydroxyl and ethoxy groups. It i s soluble i n water on a g i t a t i o n . The presence of petroleum d i s t i l l a t e i n M a t a c i l 180F very l i k e l y made i t more hydrophobic compared to f e n i t r o t h i o n . The observed persistence of f e n i t r o t h i o n i n water beyond the 24 h period at concentrations ranging from 0.03 to 0.33 ppb may be a t t r i b u t a b l e to the h y d r o p h i l i c nature of the e m u l s i f i e r . T r i t o n X-100, being water soluble and a polar cosolvent, may have caused p a r t i a l mixing of f e n i t r o t h i o n i n the water column which i n conjunction with the low stream d i s charge i n f e n i t r o t h i o n t r e a t e d streams r e s u l t e d i n longer p e r s i s t ence of f e n i t r o t h i o n i n stream water than f o r aminocarb. No meta b o l i t e s (aminocarb: MA, AM and AP; f e n i t r o t h i o n : AF and FP) were found i n any of the water samples analyzed. Moss samples from the three brooks varied g r e a t l y i n t h e i r uptake and degradation or release of the insecticides (Table I I I ) . Peak concentrations of aminocarb (98 and 152 ppb) along with detectable l e v e l s of AM and MA were found i n moss 3 h a f t e r the 1st and 2nd aminocarb a p p l i c a t i o n s and p e r s i s t e d at measurable amounts (16 and 19 ppb) beyond the 24 h sampling p e r i o d . The bioaccumulation r a t i o s [aminocarb concen. i n moss (as sampled)/aminocarb concen. i n water] f o r moss i n Portage Brook a f t e r the 1st and 2nd a p p l i c a t i o n s were 33 and 211, r e s p e c t i v e l y at peak water concentrations. Small amounts (oa 20 ppb) of aminocarb p e r s i s t e d i n moss over the 8-day period from the 1st a p p l i c a t i o n to the pre-spray sample i n 2nd a p p l i c a t i o n . P e r s i s t e n c e of aminocarb i n aquatic vegetation has not been reported p r e v i o u s l y and future i n v e s t i g a t i o n s should be made to determine the p o s s i b l e ecological ramifications.
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Table I I . Insecticide concentrations aerial applications of aminocarb and Portage Brook (aminocarb) Time after application (h)
1st a p p l i c a t i o n
Moss*
Pre-spray
ND
1
75 (290)**
3
98 (349)
6
2nd a p p l i c a t i o n Brook trout*
Moss*
Brook trout*
ND
20 (72)
ND
25.1
112 (399)
84.6
