Persistence of Pesticides in River Water James W. Eichelberger and James J. Lichtenberg Environmental Protection Agency, Water Quality Office, Analytical Quality Control Laboratory, Cincinnati, Ohio 45202 Experimental
The persistence of 28 common pesticides in raw river water was studied over an eight-week period. Twelve organochlorine, nine organophosphorus, and seven carbamate pesticides were studied a t a concentration of 10 pg/liter. No measurable degradation or chemical change was observed for the following organochlorine compounds : BHC, heptachlor epoxide, dieldrin, DDE,DDT, DDD, and endrin. Azodrin was the only organophosphorus compound that was stable throughout the study. All carbamate compounds were significantly changed after one week, and all but Baygon were completely lost after eight weeks. Where possible, the degradation or chemical conversion products of the pesticides were identified.
P
esticides, because of their widespread distribution and toxic nature, have become a n important class of water pollutants today. Fish kills caused by various pesticides have been reported on a global scale. Pesticides are introduced into water systems from various sources-industrial effluents, agricultural runoff, and chemical spills. Even if these compounds are present only in very low concentrations, they are hazardous because some species of aquatic life are known to concentrate them 1000-fold or more. There is n o predictable safe level for pesticides in waters where food-chain buildup can occur. Little information is available concerning the persistence of pesticides in water. Such information would be extremely valuable for their identification and measurement in streams. Bevenue and Yeo (1969) and Thruston (1965) studied the weathering effect o n chlordane from a prolonged exposure to water and organic solvent environments. Schwartz (1966) studied the microbial degradation of a carbamate pesticide, isopropyl-N-(3-~hlorophenyl) carbamate (CIPC), and a chlorinated herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), in water. Hill and McCarty (1967) studied the degradation of some chlorinated hydrocarbon pesticides under anaerobic conditions. Gannon and Bigger (1958) and Hendrick et al. (1966) studied the conversion of aldrin to dieldrin in soil and water. All of these studies were limited to a few pesticides; extrapolation to other compounds in the same class is impossible due to the variable physical and chemical properties of the pesticides and the kind of change that they undergo. It is very probable that many of these compounds are altered in water either immediately or slowly over a period of weeks or months. This study was designed to investigate the stability of a number of common pesticides in raw river water and, where possible, to identify the chemical or biological degradation product. Various organochlorine, organophosphorus, and carbamate pesticides (28 in all) were studied at intervals over a n eight-week period.
Raw water from the Little Miami River, a relatively small stream receiving domestic and industrial wastes and farm runoff, was used for the study. Some of the chemical characteristics of the water are listed in Table I. The compounds used in this study are listed below. A preliminary study of the compounds marked with a n asterisk was carried out in distilled water over a three-week period. Organochlorine *BHC
*Heptachlor *Aldrin *Heptachlor epoxide Telodrin Endosulfan *Dieldrin *DDE *DDT(tech.)
Organophosphorus Carbamates *Parathion *Methyl parathion *Malathion *Ethion Trithion *Fenthion Dimethoate Merphos Azodrin
Sevin Zectran Baygon Mesurol Matacil Monuron Fenuron
DDD
Chlordane (tech.) *Endrin F o r each compound, 20 liters of water in individual glass jars were used, 15 dosed and five blanks. Dosing was carried out using a freshly prepared 0.1 % solution of the compound in acetone and injecting 10 p1 into the water with a 2 5 - 4 microsyringe, giving 10 pg of compound per liter of water. The standard compounds were obtained from the Pesticides Repository (Pesticides Research Laboratory, Perrine, Fla.). After each liter was dosed, the cap was replaced and the sample shaken vigorously to distribute the pesticide in the water. (The caps were Teflon-lined to prevent contamination of the sample from the cap liner.) Approximately 1 hr after dosing, three dosed samples plus one blank were extracted. This extraction was considered to be time zero. The same procedure was carried out one, two, four, and eight weeks after dosing. During the eight weeks, the unextracted samples were kept in the sealed glass jars o n a laboratory bench under sunlight and artificial fluorescent light. The jars were shaken periodically and just prior to extraction to redistribute any suspended matter which might have settled out. Extraction of the organochlorine compounds was accomplished by using 15 ethyl ether in hexane according t o the “Federal Water Pollution Control Administration Method for Chlorinated Hydrocarbon Pesticides in Water and Wastewater” (1969). The organophosphorus compounds were extracted with 2 0 x benzene in hexane, except dimethoate which was extracted with methylene chloride, and azodrin which was extracted with chloroform, because 20 % benzene in hexane would not extract these two compounds. The carbamate compounds were extracted with chloroform. Each was extracted with three 60-ml aliquots of solvent. The efficiency of extraction of each solvent used for each type of Volume 5 , Number 6, June 1971 541
Table I. Chemical Analysis of Little Miami River Water PH
Conductivity Turbidity Color Chloride Alkalinity Hardness Sulfate Phosphorus
+
NH3 organic nitrogen Total organic carbon
Nitrate
7 . 3 at time zero, varied up to 8.0 during the eight-week period 365 pmohs/cm 210 n u 25 units 17 mg/liter 98 mg/liter 150 mg/liter 50 mg/liter 0 . 7 3 mglliter (total) 0 . 1 7 mg/liter (dissolved) 4 . 3 mg/liter 1 0 , 7 mg/liter (total) 5 . 0 mg/liter (dissolved) 1 , 2 7 mgfliter
compound was thoroughly checked before use in this study. The recovery was consistently between 90 and 100% at the 1 to 10 pgjliter concentrations for all compounds listed above. The whole water sample was extracted including any suspended matter present. The inside of the jar was rinsed with each aliquot of extracting solvent before extraction to remove any compounds which may have been adsorbed to the container wall. Quantitation of the organochlorine compounds was done with a Micro Tek DSS Model 179 gas chromatograph equipped with a nickel-63 electron-capture detector. The column was 6-ft long by 0.25-in. 0.d. coiled aluminum packed with 60180 mesh Gas-Chrom Q coated with 5 % ov-17. The instrument temperatures were: injection block, 240°C; column, 200OC; and detector, 230°C. J The organophosphorus compounds were quantitated with use of a Micro Tek DSS Model 179 gas chromatograph equipped with a flame-photometric detector. The filter which passes only the 526 mp emission, characteristic of phosphorus, was used to detect the parent compounds plus any phosphorus-containing decomposition products. The filter which passes only the 394 mp emission, characteristic of sulfur, was used to detect any decomposition products containing sulfur and n o phosphorus. The column was a 3-ft long by 0.25-in. 0.d. glass tube packed with Gas-Chrom Q coated with 2z Reoplex 400. Temperatures were: injection block, 21 5OC; column, 180°C; and detector, 160OC. A Perkin-Elmer infrared spectrophotometer and microequipment were used to identify reaction products whenever possible. Thin-layer chromatography (TLC) was used to detect and quantitate the carbamate compounds. The method of Longbottom and Lichtenberg (1969) which detects the carbamates by hydrolyzing them to their respective phenols or aromatic amines was very useful for this study. This method uses silica gel layers and a double development in chloroform. The layer, after development, is sprayed with Gibbs' reagent (2,6-dibromoquinone chlorimide, a 1 solution in chloroform) and heated in a n oven at 110°C for 15 min. Qualitative identification is made by comparing the distance each compound migrates up the layer and the color obtained after spraying. Quantification is accomplished by comparing the color in542 Environmental Science & Technology
tensity and the area of the spot with those of the known standards. The minimum detectable concentration for the organochlorine and organophosphorus compounds was approximately 50 ng/liter. The minimum detectable concentration for the carbamate compounds using the TLC is 100 ngjliter. If the carbamates are hydrolyzed in the water, this method is capable of measuring the parent compound along with its hydrolysis product and the rate of hydrolysis can be observed. Results and Discussion
The environmental conditions in a naturally flowing stream are different from the conditions for this study and the rates of such degradation will undoubtedly vary, although similar reactions would be expected t o occur. The results are therefore valid only for the conditions studied-Le., dosed raw river water in closed glass containers, standing at room temperature, exposed to natural and artificial light. As seen below, the similarity of results obtained with the organochlorine compounds in distilled water, under the same conditions, only over a three-week period instead of eight weeks, suggests that the persistence may be the same in a variety of water. The compounds were studied a t the 10 pg/liter concentration. Although this concentration is somewhat high for a n average surface water sample, in some cases it permitted the identification of the decomposition products. Organochlorine Compounds. Five of the 12 compounds studied underwent chemical change during the eight-week period: heptachlor, telodrin, endosulfan, aldrin, and chlordane. The remaining compounds were unchanged (Table 11). Heptachlor was altered to 1-hydroxy chlordene by the replacement of one chlorine atom with an hydroxyl group as shown below, This was observed by the reduction of the peak produced by heptachlor in the gas chromatogram and the appearance of a new peak with the same retention time and characteristic peak geometry as 1-hydroxy chlordene. J ( ' c
HOH
CI cI
H'
El
1- H Y D R O X Y
HEPTCC H L O R
CHLORDEhE
This conversion was confirmed by collecting the newly formed compound from a flame-ionization gas chromatograph and obtaining its infrared spectrum which was identical to that of 1-hydroxy chlordene. The conversion was complete in two weeks. The same reaction at the same rate was observed in distilled water. However, at the end of the second week, another peak was noted in the chromatogram which was similar to the response from heptachlor epoxide. It was observed that a n equilibrium existed at the end of four weeks between 1-hydroxy chlordene and heptachlor epoxide so that approximately 60 of the converted heptachlor remained as 1-hydroxy chlordene and 4 0 z was further converted to the epoxide. Telodrin was altered 75 after one week and 90 after two weeks, so that a t the end of four weeks, n o measurable peak was observed in the gas chromatogram. Judging from the number of chlorine atoms in the telodrin molecule, which indicates a high degree of electronegativity, plus the fact that at lower column temperatures no response was observed from the conversion or decomposition products with the electroncapture detector, it was assumed that the compound was
z
z
z
decomposed rather than converted to a chemically similar compound. Endosulfan contains two active isomers: endosulfan I, the lower boiling isomer; and endosulfan I1 (Cassil and Drummond, 1965), the higher boiling isomer which has a retention time 1.6 that of isomer I. Both isomers are chemically changed during the first week so that the peaks of the parent compound are reduced considerably in size and a new peak appears. Both isomers disappear completely in four weeks. The new peak has a relative retention time 0.6 that of endosulfan I. It was found by analyzing the extract with the flame-photometric detector in the sulfur mode that the endosulfan decomposition compound contained no sulfur. This indicates that endosulfan alcohol may be the decomposition product (O'Brien, 1967). This possibility was supported by the infrared spectrum of the extract, which showed a very strong group of absorption bands at 1050 to 1100 cm-' plus a strong bonded OH band at 3300 cm-'. In any event, the gas chromatographic identification and quantitation of endosulfan was extremely difficult after one week. Aldrin, as reported earlier, underwent epoxidation to form dieldrin, as shown below. This was confirmed by the diminishing of the aldrin peak and the appearance of a dieldrin peak in the gas chromatogram of the sample extract. The conversion proceeded very slowly and was only 80% complete after eight weeks. However, it has been observed in this laboratory that total conversion will take place if sufficient
ALDRIN
DIELDRIN
time is allowed. This means that some occurrences of dieldrin may be in part or in total attributed to the original presence of aldrin. Of the major components of technical chlordane, only aand y-chlordane were completely stable over the eight-week period. These findings agree with those of Bevenue and Yeo (1969). It appears that the peaks produced by these two compounds in the gas chromatogram are the only reliable indication of the presence of technical chlordane in a water sample extract unless the chlordane has been present a very short time. All but two of the components are at least partially changed, and cannot be used for quantitation; but, since the a- and y-isomers are not changed, they can be used to quantitate the technical mixture at its original concentration. In studying the organochlorine compounds, similar reactions and reaction rates were observed in distilled water and raw water. Since distilled water contains very little bacteria and virtually no algae, indications are that chemical conversions rather than biological degradations are taking place. Organophosphorus Compounds. All eight thiophosphate compounds underwent some degree of chemical change during eight weeks. The organophosphorus compounds which were studied in both types of water (see above list) did not undergo a change in the distilled water during three weeks but did change in the raw water during that period. This indicates that probably a biological reaction is taking place in the raw water. However, this was not proved conclusively. Table I1 shows the percent of each compound that remained unchanged during the eight-week period and gives an indication of the rate of change of each compound.
Table 11. Persistence of Compounds in River Water Compound
Original compound found., 0-time 1 wk 2wk 4 wk 8 wk
Organochlorine compounds BHC 100 100 Heptachlor 100 25 Aldrin 100 100 Heptachlor epoxide 100 100 Telodrin 100 25 Endosulfan 100 30 Dieldrin 100 100 DDE 100 100 DDT 100 100 DDD 100 100 Chlordane (tech.) 100 90 Endrin 100 100 Organophosphorus compounds Parathion 100 50 Methyl parathion 80 25 Malathion 100 25 100 90 Ethion Trithion 90 25 Fenthion 100 50 Dimethoate 100 100 Merphos 0 0 Merphos recov. as Def 100 50 Azodrin 100 100 Carbamate compounds Sevin 90 5 Zectran 100 15 Matacil 100 60 Mesurol 90 0 100 50 Baygon Monuron 80 40 Fenuron 80 60
100 0 80
100 0 40
100
100 10 5 100 100 100 100 85 100
100 0 0 100 100 100 100 85 100
100 0 0 100 100 100 100 85 100
30 10 10 75 10 10 85 0
