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c] New York A vast aquifer system underlies Long Island. It represents the only source of drinking water for more than 3 million people (primarily those in Nassau and Suffolk counties) and has been designated a sole source aquifer by the EPA under the provisions of the Safe Drinking Water ACt (SODA). Groundwater contamination problems in Suffolk County are varied and widespread. Currently, the most signifi- cant problems are contamination by synthetic organic chemicals including pesticides, solvents, and degreasers (such as to ichloroethylene and related chemicals); On July 23 and 24, 1984, Holden visited various individuals in New York who are knowledgeable of the problems caused in Suffolk County, Long Island, New York, by leaching agricultural chemicals, especially the pesti- cide aldicarb (Temik). The Suffolk County experience provides a significant case history because of the extensive sampling carried out to determine the presence of aldicarb and other pesticides in water from public and private water wells and because of the actions taken to address the problem of pesticide usage in sensitive hydrologic environments. The institutions represented by those individuals visited include the Suffolk County Department of Health Services, which has been most directly involved in sampling and testing water from wells in areas suspected of being contaminated with toxic organic chemicals; the Suffolk County Cooperative Extension Office, which works on a daily basis with growers and makes management recommendations; and Cornell University. 31
32 nitrate contamination from sewage disposal and fertilizer use; and saltwater intrusion caused by groundwater overdraft or depletion. The primary aquifer on Long Island is composed of unconsolidated geologic material that ranges in thickness from a few hundred feet to more than 1,000 feet. This geologic formation, known as the Magothy, is moderately permeable, while the glacial outwash deposits that overlie it are moderately to highly permeable. The glacial sediments composing the unsaturated zone above the Magothy have a high vertical permeability, and recharge to the water table occurs virtually all over the island. m e depth to groundwater in most locations in Suffolk County is less than 60 feet, which is relatively shallow. m ese characteristics ~na~cace a Sign poren~za' for waterborne contaminants to percolate to the aquifer. In addition, the soils of Long Island are cold, low in organic matter, and acidic. Also, Long Island ground- water is generally acidic, with pa values between 5 and 6 quite coon . In this environment, aldicarb and similar compounds break down slowly, remaining available for leaching and persisting once they reach the ground- water. The U.S. Geological Survey estimates that the residence time of water in this aquifer system may be extremely long, perhaps many hundreds of years. The western portions of Suffolk County are Heavily developed, but the eastern end of the county, which includes the North and South Forks, is comparatively undeveloped. In the rural areas of eastern Suffolk County, where agricultural production primarily occurs, most homes are served by private residential drink~ng- water wells. Approximately 70,000 domestic wells are currently in use in Suffolk County. Suffolk County, with agr icultural products having market values exceeding 310 o million a year, is the leading Earm county in New York State. The main crop grown on Long Island is potatoes, but the number of acres planted has been steadily declining since 1960. In 1984, potato growers planted just 14,000 acres--a decline of 8,000 acres over the last ~ years. Efforts to control potato pests, especially the Colorado potato beetle and the golden nematode, have been the source of the most Vapor ten t pesticide contaminants of Suffolk County groundwater. The golden nematode, which was apparently introduced into New York State on infested seed potatoes in the late 1940s, has been the subject of quarantine and eradication programs. Fortunately, it has been contained to Long Island and an upstate area. . . . . . , _ ~ ~ ,
33 TABLE 2-1 Pesticides in Suf folk County Groundwater Pesticides Detected and Confirmed Aldicarb (Temik) Carbofuran Chlorothalomil Dacthal Dinoseb Oxamyl (Vydate) D-D (1, 2-Dichloropropane) EDB (1,2-Dibromoethane)a Pesticides Detected but Not Yet Confirmed - Carbaryl (Sevin) Dibrom Methomyl (Lannate) Paraquat Picloram (Tordon) aThe ethylene bromide (EDB) detected--at very low levels in one agricultural well--may have resulted from gasoline contamination. SOURCE: Suffolk County Department of Health Services. Virtually all the crops, including potatoes, grown in Suffolk County are irrigated. Frequency of irrigation depends on the crop and need and ranges from 1 to 6 or 8 times per growing season. Essentially no pesticides are applied through irrigation water. WE STATUS OF EFEORTS TO MONITOR GROUNOWATE:R FOR RESIDUES OF AG=COLTURAL PESTICIDES Past Monitoring Efforts In 1976 the Cooperative Extension Service of Suffolk County had recommended sampling groundwater for carbonate pesticides after it had examined the results of a water pollution study assessing the use and impact of pesti- cides in Suffolk County. Three years passed, however, before any groundwater samples were taken. Contamination of groundwater with pesticides was first detected on Long Island in August 1979, when samples taken from shallow wells located at the Long Island Horticultural Research Laboratory at Riverhead (a branch of Cornell University) indicated that aldicarb was percolating through the unsaturated zone to groundwater. To date, 13 pesticides including aldicarb have been detected in Suffolk County's groundwater. Of these, eight have been confirmed by retesting (see Table 2-1).
34 TABLE 2-2 Selected Chemical Characteristics of Aldicarb and Its Metabolites Oral LD50 Water Solubility Ed (distribution coeff icient) Roc (organic carbon coef f iciest) Vapor Pressure Hydrolysis Balf-life Aldicarb and A. sulfoxide Aldicarb sulfone Aldicarb Aldicarb sulfoxide Aldicarb sulfone Aldicarb sulfoxide: clay with 1.48 organic Latter Silt loam with 1.4% organic matter Aldicarb Aldicarb sul£oxide Aldicarb (hydrolysis of total residues: Aldicarb + sulfoxide + sulfone) at pE 7.5 and 15°C at pE! 5.5 and 5°C 0.9 mg/kg 20-25 mg/kg 6,000 ppm 43, 000 ppm 7,800 ppm 3.3 0.34 36 42 1 x 10-4 "-ng at 25°C 5.0 years 12.5 year s Now: Cohen, S.Z., et al., 1984, ·Potential for pesticide contamination of groundwater resulting from agricultural uses,. pp. 297 in Treatment and Disoosal of Pesticide Wastes, African Chemical Society Symposium Series, suggest that chemicals with Abe following characteristics should be considered a potential groundwater contaminant: water solubility greater than approximately 30 ppm; Ed less than 5; Roc less than 300-S00; and hydrolysis balf-life greater than 25 weeks. Aldicarb Aldicarb, which triggered the issue of groundwater contamination by field-supplied pesticides, is a systemic carbamate insecticide that also has nematocidal proper- ties. Aldicarb is the common name for the active ingredient 2-methyl-2-(methylthio) propionaldehy~e O~(methylcarbamoyl) oxime. It is manufactured by Union Carbide Agricultural Products Co., Inc., and sold in granular form under the trade name Temik. Because of its high acute mammalian toxicity, aldicarb is available only in granular formulations (5-1S percent active ingredients) for soil incorporation. Under f ield conditions, the parent material is quickly transformed to aldicarb sulfoxide and aldicarb sulfone. The characteristics of aldicarb and its metabolites indicate that the pesticide is a potential groundwater contaminant (see Table 2-2). m e general character of residues in groundwater is O percent aldicarb, 40-60 percent aldicarb sulfoxide, and 60-40 percent aldicarb sulfone. This ratio remains essentially stable as the aldicarb
35 metabolites degrade to biologically inactive compounds The acute mammalian toxicity of Aldicarb sulfoxide is similar to that of aldicarb, whereas that of aldicarb sulfone is considerably lower. Aldicarb and its metabolites have been relatively well tested and are not known to be carcinogenic or teratogenic. Aldicarb is a highly soluble and relatively nonvola- tile pesticide, the effectiveness of which is a function of its ability to go into solution with available soil moisture. Once in solution, the insecticide enters the plant by way of root action and eventually is retained in the succulent parts of the plant. Sucking and chewing insects, such as aphids or the Colorado potato beetle. are then effectively controlled when they feed. Typical applications of aldicarb on Long Island were 5 lbs active ingredients (ai) per acre (A) at spring planting followed with an additional 1-2 Ibs ai/A as a side dressing at mid-season. Such applications were made on virtually all the approximately 22,000 acres of potato fields in Suffolk County between 1975 and 1979. Rates were initially 3 lbs ai/A at planting (nationally labeled use rate), but the rates in New York were raised at the request of state scientists to ~ lbs for positive golden nematode control, then to ~ lies at planting and 2 lbs side-dressed for seasonal Colorado potato beetle control. The pesticide was applied in the form of Temik 1SG (15 percent active ingredient granules). . Groundwater contamination by aldicarb. Aldicarb has . been the focus of groundwater investigations in Wisconsin and Florida (discussed in Chapters 3 and 4, respectively) as well as in New York. Bowever, nowhere has the ground- water contamination caused by aldicarb been more extensive and better documented than on Long Island. Between August 1979 and mid-March 1980, approximately 270 wells were sampled on eastern Long Island; of those sampled 45 were public, 214 were domestic, and 11 were irrigation wells. Aldicarb concentrations in water samples from 61 wells (29 percent) exceeded the acceptable guideline of 7 ppb established by New York. Thirty-five wells (16 percent) had detectable traces below the guideline. The analyses were carried out by Union Carbide analytic laboratories. Most of these samples were taken in areas with the greatest potential for contamination--that is, locations with shallow water tables, sandy soils, and intensive potato production coupled with heavy use of aidicarb.
36 As a result of the initial investigation, an extensive well sampling program was begun to investigate the water quality of all wells near potato farming operations. An intensive monitoring program conducted from April to June 1980 included the collection of water samples from nearly 8,000 wells, the majority privately owned. The Suffolk County Department of Bealth Services (SCDHS) provided staff for the sample collection. Union Carbide paid the costs of shipping samples and also conducted the analyses. Of the 7,809 wells sampled during this survey, 5,745 (73.6 percent) had nondetectable concentrations of aldicarb; 1,025 (13.1 percent) had concentrations over the recommended standard of 7 ppb; and 1,032 (13.3 per- cent) contained traces of the pesticide (see Table 2-3). The mean concentration of aldicarb in all samples in which it was detected was 23.5 ppb. On the basis of the rate of groundwater flow (approxi- mately 150-200 feet/year) and the nether of years the pesticide had been used, the SCDES concluded that only wells within 2,500 feet of potato farms were subject to possible contamination. Given this sampling constraint, more than 100 square miles remained to be surveyed and sampled. The area was divided into grids approximately 1,500 feet square resulting in 1,235 coordinate grids. m e SCDES field staff, assigned to specific areas, conducted block-by-block searches to assess the water quality of domestic wells. All accessible wells within 2,500 feet of potato farms were sampled. The percentage of wells with positive aldicarb detections in individual Suffolk County communities within the five townships sampled varied from 0 to 48.2 percent. On a township basis (Table 2-4), the percentages ranged from 9.0 to 32.2 percent. Data collected from this survey confirmed that the highest concentrations of aldicarb were found closest to the potato fields. The relationship between the number of contaminated wells and the distance to the potato fields is represented in Figure 2-1. Treatment of water contaminated by aldicarb. Indi- vidual homeowners were informed of the quality of their drinking water. Those homeowners whose well water con- tained concentrations of aldicarb in excess of the recommended guideline of ~ ppb were cautioned not to use their water supply for cooking or drinking purposes. In response to the sampling program findings, an offer was made by Union Carbide to provide a granular activated
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39 m - loo o Too - 500 L z 0 5 TO ~000 DISTANCE FROM WELL TO POTATO HARM FT. FIGURE 2-1 Nl'~nher of wells with traces of aldicarb as a function of distance from well to potato farm. NOTE: me graph represents a point in time during the 1980 sampling program. Therefore, with passage of time and movement of groundwaters, wells farther from the fields have been contaminated. SOURCE: Baler, Joseph, and Dennis Moran, 1981, p. 24 in Status Report on Aldicarb Contamination of Groundwater as of September, 1981, Suffolk County Department of Health Services, Long Island, New York. carbon (GAC) treatment unit to those homeowners. To date, approximately 2,000 GAC units, each typically containing 29 lies of granulated carbon, have been installed in Suffolk County at a cost to Union Carbide of approximately $450 each. Additionally, Union Carbide recharges the SAC unit with fresh activated carbon every 9 to 15 months, at a cost of approximately S60-S70 per unit. In addition to domestic wells, a few municipal public supply wells exceeded the aldicarb guideline of 7 ppb.
40 These wells required the installation of large GAC treat- ment units. For example, Union Carbide installed a permanent GAC unit at Greenport well 6-1 (Greenport is on the North Fork east of Southhold) that contains 20,000 lbs of activated carbon and is able to treat 450 gallons of water per minute. It treated 168 million gallons of water prior to recharging after 1 year of operation. Recharging of this large unit is required on an annual basis, with Union Carbide paying all associated expenses. Additionally, large mobile GAC units have been used in Suffolk County to treat municipal wells that temporarily exceed the state aldicarb guideline. From the viewpoint of Suffolk County, the GAC units were an immediate response to an emergency situation, but never a long-term solution. Many of these units have been in place for more than 4 years, however, and no obvious alternative exists to their continued use, which is considered to be highly effective. Factors contributing to qroundwater contamination by aldicarb in Suffolk County. me primary factors that contributed to the presence of aldicarb in Suffolk County's groundwater include the pervasive and high rates of use of aldicarb, its high water Volubility, heavy spring rainfalls following application, very permeable soils typical of glacial outwash deposits, cold soil temperature, acid soil conditions, low organic matter content, shallow water table conditions, and the presence of many shallow wells immediately downgradient of treated fields. Once aldicarb reaches the groundwater, it may behave as a ~conservative" substance--one that is absent or nearly absent from natural waters, does not react chemi- cally with the natural water, and is not absorbed by the porous media of an aquifer. Those working on the problem have been frustrated by the longer than expected half- life of aldicarb in Suffolk County's groundwater. Initial estimates that the half-life of aldicarb in the Magothy aquifer would be 3 years have been revised, and currently the SCDES assumes that total aldicarb (that is, aldicarb plus its metabolizes) will remain above the 7 ppb levels in the groundwater for decades. Studies have shown that the half-life of aldicarb sulfoxide in well water at 15°C and pa 6.0 is approxi- mately 22.5 years, whereas at the same temperature but with base conditions (pa 8.0), the half-life value is only 82 days (see Table 2-4). Given the acidic nature
41 of groundwater in Suffolk County (commonly pE 5.0-6.0), the implication for the persistence of aldicarb and other carbamate pesticides in the groundwater is clear. Experimental use permit. As a result of the sampling and detection of aldicarb in the groundwater, Union Carbide voluntarily removed Temik 15G from sale on Long Island before the 1980 growing season. The abrupt with- drawal of the pesticide from the market created problems for potato farmers who were hard-pressed to find an effective substitute to control the Colorado potato beetle. In response to this situation, an interagency steering committee, working with farm representatives and Union Carbide, agreed to the urgent need for an Experimental Use Permit (EUP) for aldicarb. An EUP, authorized by section 5 of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), permits the field testing of an unregistered use. It was believed that the EUP was needed to determine whether variations in the quantity or taming of applica- tions might diminish or eliminate the possibility of aldicarb or its metabolites leaching to ground~ater. An EUP permit was granted by EPA to Onion Carbide on March 28, 1980, to evaluate this hypothesis. The company then made arrangements to fund the Cornell Cooperative Extension and the SCDES for the planned investigation, which occurred from March 28, 1980, to March 25, 1981. The EUP allowed controlled use of aldicarb on several test areas; approximately 50 acres from three farms were planted with potatoes and treated with aldicarb by several methods of application. In a cover letter accompanying the June 1982 Aldicarb . EUP Report, Dr. Theodore L. Bullar, Director of the Cornell University Agricultural Experiment Station, outlined the prominent overall findings of the EUP investigation: · The withdrawal of the pesticide from the Long Island Market seriously reduced the ability of farmers to control the Colorado potato beetle. It would be virtually impossible to use aldicarb on Long Island in a way that was consistent with the 7 ppb guideline. · Most of the aldicarb appears to disappear from the soil fairly soon after planting. The data are insuf- ficient to determine whether this is primarily due to biological causes or leaching.
42 me EUP investigation concluded that sufficient quantities of aldicarb leached below the root zone in each exper imental treatment to cause the concentration of aldicarb in the groundwater recharge to exceed the New York State guideline of 1 ppb, assuming 50 cm of recharge per year. Little more than 1 percent of the applied aldicarb could be allowed to leach if the guideline were not to be exceeded. It was concluded that achieving such efficiency in pesticide removal was impossible for chemicals with properties similar to those of aldicarb. Additional qroundwater monitor ing for aldicarb . Groundwater monitoring for aldicarb has continued since 1980, with the total number of samples analyzed approaching 18,000. Of those wells sampled, a consistent 10-11 percent exceed the recommended guidelines for aldicarb. A 1982 report published by the SCDES entitled Report on the Occurrence and Movement cuff Agricultural . , Chemicals in Groundwater: North Fork of Suffolk County concluded that · Aldicarb contamination is currently 1 imited to the upper 30-40 feet of the Magothy aquifer except in the central recharge portion of the North Fork, where it has been detected 100 feet below the water table. If aldicarb proves to be conservative in grouna- water, it will eventually contaminate most of the North Fork aquifer, even though it has not been used in 1979; concentrations will probably approach or exceed the 7 ppb drinking-water guideline. · If aldicarb does not break down in groundwater, it will take approximately 100 years for the East End'S (North and South Forks) groundwater system to purge itself of We pesticide. According to testimony provided by Union Carbide to EPA' s FIERA Scientific Advisory Panel on June 13, 1984, trends in the concentration of aldicarb vary by well depth. In some shallow wells in Suffolk County, aldicarb levels have been declining since 1980, whereas concentra- tzons in some intermediate~depth wells have remained about constant and some deep wells have shown increases. Monitor ing for Additional Pesticides Aldicarb is not the only pesticide that has been detected in Suffolk County' s groundwater; rather, it is
43 one of approximately 50 pesticides for which groundwater has been tested (Table 2-~). However, as indicated in Table 2-5, sampling and analysis for most pesticides have been infrequent, with the exception of the carbamate pesticides, 1,2-dibromoethane (EDB), and 1,2-dichloro- propane. Complicating the picture is the lack of historical pesticide use data for Suffolk County or any other county in New York. In some cases, use Data nas been estimated based on the historical use of fields and the recommended pesticide application rates at the time. This approach has many shortcomings and at best can be relied on only to generate ~ballpark" indications of pesticide usage. Carbofuran (Furadan), another acutely toxic carbamate insecticide/nematocide, has been detected in 30 percent of the approximately 5,100 samples analyzed by the SCDuS. A much smaller percentage of the samples, about 5-6 percent, actually equaled or surpassed the New York State guideline of 15 ppb for carbofuran. Manufactured by the F~C Corporation, carbofuran is highly soluble in water (100 ppm) with a distribution coefficient (Kd) value generally reported as less than 2, and a mean organic carbon coefficient (tic) value for five soil types its hydrolytic half-life at pH 6.0 All these characteristics reported as 29 + 9. _ is approximately 1 year. indicate a chemical with the potential to contaminate groundwater. FMC voluntarily removed carbofuran from sale on Long Island in 1980. Later, FMC also agreed to pay for the installation of GAC treatment units for domestic wells with water containing carbofuran in excess of the New York State guideline of 15 ppb. Since only about 250 wells exceeded the water quality guideline For carDo- furan, the financial liability to FMC for installing the GAC units was not as severe as that experienced by Union Carbide. m e Commissioner of Health for Suffolk County has recently been orchestrating a meeting among representa- tives of various agricultural chemical companies such as Union Carbide, FMC, Dow, and Shell to discuss sharing responsibility for groundwater contamination caused by their respective products. Union Carbide has long felt that, where feasible, the costs of installing and recharging GAC units should be shared among all those responsible for the presence of organic contaminants in Suffolk County's groundwater.
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47 Golden nematode quarantine program. Another pesticide compound that has been regularly detected in groundwater samples is 1,2-dichloropropane (1,2-D). Pesticides con- taining I,2-D were used in Suffolk County from the early l950s until 1983 on fields that were quarantined by the U.S. Department of Agriculture (USDA) because of golden nematode infestation. The pesticides used that contained 1,2-D included D-D, Vorlex, Vidden D, and Telone II. (Telone II contains less than 2 percent 1,2-D.) The USDA initiated the quarantine in an attempt to eradicate the golden nematode on Long Island. It applied D-D (which contained approximately 30-35 percent 1,2-D) at levels up to 100 gallons per acre in a single applica- tion. If the initial application were thought to be unsuccessful, additional treatments were made a few weeks later. Thus, the total application of DID for a field in a single season may have been as high as 200-300 gallons per acre . Several thousand acres wer e treated with D-D and Telone II, or both, over the years the program was carried out. DID was used from the early 1950s until the late 1970s, when it was replaced by Telone l I . Telone I I was then used through the 1983 growing season. (Aldicarb was used by farmers to control the golden nematode but was never used by the USDA for this purpose.) Following the 1983 season, the USDA decided to stop all chemical treatment for the golden nematode because it concluded that no chemicals on the market could provide control without threatening the groundwater. During the 1984 growing season, the USDA recommended the use of resistant varieties of potatoes if golden nematode cysts were found in fields. Some 1,000 domestic and irrigation wells have been sampled for 1,2-D with concentrations of 30-300 ppb detected in approximately 50 percent of the samples. (ah e water quality guideline established by New York for 1,2-D is 50 ppb.) miS high percentage of detects is most likely caused by biased sampling methodology; the areas sampled were chosen based on estimates of heavy 1~2-D applications. The USDA has been involved in the sampling of wells in Suffolk County for 1,2-D and sends samples, on a regular basis, to its analytic laboratory in Gulfport, MiSSiSSippi, for analysis . Suffolk County well testing program. The SCOWS has established one of the most extensive groundwater
48 sampling programs in the nation in an attempt to charac- terize the water quality of the more than 70,000 domestic and municipal wells serving Suffolk County residents. The water quality testing is free of charge, but, because of the great number of requests received, there is a long waiting list for this service. Under this program approximately 7,000 samples are analyzed each year for organic compounds including industrial solvents, petroleum derivatives, and pesticides. The SCDHS analytic laboratory, with the help of Union Carbide, has developed the capability for performing a carbamate scan that uses a liquid chromatography process. The carbamate scan allows the laboratory to analyze for aldicarb, aldicarb sulfoxide, aldicarb sulfone, oxamyl, methomyl, 3-hydroxycarbofuran, carbofuran, carbary~, and 1-naphthol. The minimum detection level for aldicarb, its metabolites, and the six other compounds is 1 ppb. Using this method, the average recoveries of the nine pesticide and pesticide-related materials, when added to water at concentrations of 8 and 40 ppb, exceeds 95 percent. The process is automated and requires virtually no sample preparation. Groundwater sampling for pesticides in upstate New York. Little groundwater sampling for pesticides has occurred in New York outside of Long Island. A modest program carried out in 1983 at Cornell University's Center for Environmental Research sampled groundwater for the presence of aidicarb at 60 locations in potato growing areas in six upstate counties. Wells were selected that seemed most vulnerable to aldicarb con- tamination based on heavy usage of the pesticide, shallow depth to groundwater, and assumed position downgradient with regard to groundwater flow from the potato fields. (Owing to budget constraints, a precise determination of the groundwater flow direction in the proximity of the sampled wells was not possible in this study and, conse- quently, flow direction was estimated.) The analytic work was performed by a Union Carbide laboratory. Aldicarb concentrations in three wells (5 percent) exceeded the New York State health guideline of 7 ppb. The soils near these wells were sandy, and aldicarb had been applied in the areas either every year or every other year for 8 years preceding the sampling. At 15 locations (25 percent), the groundwater was found to have concentrations between 1 and 7 ppb; the remaining 42 locations (70 percent) had no detectable amounts of
49 aldicarb. Some of the areas tested had muck soils with higher organic matter content and microbial populations chan the sandy soils of Suffolk County. AIdicarb concen- trations in groundwater in these muck-soil areas never exceeded 2 ppb. Cornell University scientists postulated that the elevated presence of organic matter resulted in the ald~carb being strongly sorbed by the muck soils, which facilitated the pesticide Is accelerated breakdown by high bacterial populations. Of the 19 samples analyzed for nitrates, 16 contained measurable levels between 0.05 and 18.0 ppm. No well showed positive detections for both nitrate and aldicarb, so no compari- son could be made between nitrate and aldicarb concen- trations. Also in 1983 the New York State Department of Health sampled 10 wells in upstate New York for aldicarb. This effort found one well with an aldicarb concentration of 30 ppb. This well was only 25 feet deep and located adjacent to a potato field. Other wells had no detect- able amounts of aldicarb in the groundwater. Porter and Pacenka (1983) in a Cornell University report entitled Results of 1983 Upstate New York Sampling of Groundwater for Aldicarb, recommended that the state initiate a Carefully specified sampling program for rural drinking water wells in upstate New York.. They suggested that the state identify the chemicals that are likely to be introduced and persist in groundwater, determine ground- water flow direction from the point of use of these chemicals, and calculate the travel time required for the chemicals to move from the point of application to a well. However, no systematic survey of this type has been initiated to determine possible threats to drinking- water quality in rural areas of New York. Current Monitoring Efforts Virtually all current monitoring of groundwater for pesticides in New York is being conducted in Suffolk County, where 35-45 percent of approximately 20, 000 samples collected annually are analyzed for organic constituents including pesticides. The carbonate pesti- cide scan mentioned earlier is used to analyze approxi- mately 5,000 samples per year. The well testing and subsequent analyses are done on a request basis. Fre- quently, months elapse between the time a request is made and the time the sampling and analyses actually occur.
50 Cooperative sampling by Union Carbide and the SCDES of wells where aldicarb was detected is continuing to provide environmental fate data on aldicarb in the Magothy aquifer. Also, the USDA is carrying out limited sampling for 1,2-D to assess the extent of groundwater contamination caused by pesticides containing 1,2-D used in the golden nematode quarantine program. CRITICAL PROBLEMS AND NEEDS Nematocides Nematocides such as aldicarb, D-D, and carbofuran have caused extensive groundwater contamination in Suffolk County. None of the nematocides just mentioned is used any longer in Suffolk County. AS in California, nemato- cides reaching groundwater present a difficult management problem with no obvious resolution. m e golden nematode (Heterodera rostochiensis) and root lesion nematode ~- (Pratylenchus penetrane) are signif~cant pests in potato production. But because of the highly vulnerable hydrologic environment in Suffolk County and the high water Volubility of most nematocides, few nematocides can be used there without threatening groundwater. In recognition of this problem, the USDA decided in 1984 against chemical treatment for the golden nematode and recommended the use of resistant varieties of potatoes in areas where golden nematode cysts are discovered. The root lesion nematode (RLN) was ~ denti- fied In 1984 as an important pest in potato fields, especially on the South Fork, where a rotation of potatoes with rye is common. Rye is an excellent host for RLN. Factors such as soil moisture, temperature, organic matter, and pE also may be more favorable for the RLN on the South Fork. Potato varieties resistant to nematodes are being advocated as an alternative to the use of nematocides. However, existing resistant varie- ties may not possess the quality or other necessary traits that would lead to their widespread adoption by potato growers. Short-term options to control nematodes are thus considered very limited.
51 Interdisciplinary Research The need for interdisciplinary research to address the impacts of agriculture on groundwater was generally recognized among those visited in New York. For example, researchers at Cornell University, Pennsylvania State University, the University of Maryland, and the Univer- sity of Delaware have submitted to the Northeast Regional Cooperative States Research Service of the USDA a proposal for research to evaluate pesticide and nutrient losses by leaching and runoff in tilled and untilled soils. The research program would also establish a data base for the development and testing of water quality models. The research would draw on the talents of agronomists, soil physicists, hydrologists, chemists, entomologists, and agricultural engineers at the univer- sities mentioned. Justifying the need for this research, the researchers assert that most environmental fate research is retrospective, after the chemical is released to the system. But with properly constructed and vali- dated models it may ultimately be possible to consider pesticide usage on a prospective basis, thus managing chemical applications to prevent unacceptable groundwater contamination. Additionally, studies are needed to determine what, if any, additional risk no-till agricul- ture poses to groundwater given the increased use of herbicides required by that management strategy. A scientist associated with the Chemicals-Pesticide Program at Cornell University said that the occurrence in Suffolk County of groundwater contamination from pesticides was just the whip of the iceberg. in terms of the overall problem and that the issue was not going to disappear and deserved the immediate attention of an interdisciplinary research team. His main concern was that additional detections of pesticides in groundwater could lead to public pressures to ban pesticides known to be contaminants. He voiced a commonly heard observation that the ability to detect trace amounts of pesticides in water was much more advanced than the understanding of the toxicology associated with such discoveries. Evaluation of Leaching Potential of Pesticides .. . . The aldicarb experience on Long Island illustrates the insufficiency of environmental fate data that the EPA
~2 historically required from agricultural chemical companies for a pesticide's registration. Based on the environmental fate studies reported at the time of registration, aldicarb was expected to break down to nontoxic by-products long before it could leach to the groundwater in a toxic form. Unfortunately, events and increased analytic capabilities proved this was not the case. EPA is increasing its environmental fate data requirements (see Chapter 5), but the methodology for easily evaluating the potential movement of pesticides beyond the root zone and predicting more accurately the environmental fate of pesticides remains elusive. This problem is discussed more fully in the section MODELS TO PREDICT TlIE TRANSPORT AND ENVIRONMENTAL FATE OF PESTICIDES . Groundwater Quality Data Base The groundwater quality data base dating back to 1919 for a handful of pesticides in Suffolk County is exten- sive and useful; however, the data base for New York as a whole is practically nonexistent. More than 18,000 samples from Suffolk County have been analyzed for aldicarb versus less than 100 from remainder of the state. The New York State Department of Environmental Conservation has not initiated significant programs to characterize the groundwater quality in agricultural areas. Reasons for the relative scarcity of samplings outside of Suffolk County include less susceptible environmental conditions; less concentrated agriculture; and a lack of historical pesticide use data. Residue Analysis The carbamate pesticide scan permits analytic values to be generated from a single groundwater sample for aldicarb and its meta~olites, as well as for carbofuran, carbaryl, oxtail, and methomyl. The cost savings asso- czated with such a multiresidue technique are signifi- cant, and the data base can be expanded more rapidly for a given sampling program budget. A multiresidue analytic screening technique that could handle an even wider range of pesticides would obviously yield even greater benefits for each dollar spent on a sampling program.
53 Pesticide Applicators Unlike California, where aerial applicators often work from a single landing strip, aerial application of pesti- cides on Long Island is primarily accomplished by helz- copters that fill their spray tanks in the area they are spraying and do not continually return to the same location for refueling and refilling. This method of applying pesticides allegedly reduces the potential for concentrated po~nt-source pollution of groundwater caused by spills during the filling of spray tanks. Apparently, on Long Island the threat to groundwater quality from point sources of pesticides is minimal when contrasted with nonpoint sources. PubliC Sentiment Against Pesticide Usage A researcher at Cornell University mentioned his concern that the public on Long Island had become prejudiced against the use of pesticides because of the problems associated with aidicarb, carbofuran, 1,2-D, and others. He was especially concerned about the availa- b~lity of pesticides for minor or specialty crops because the range of alternative pesticides for these crops is narrow. Consequently, the loss of an effective chemical for minor crops can more severely impact that agricul- tural sector than the loss of a pesticide for more prominent crops such as corn, soybeans, or cotton. This concern is especially relevant to Suffolk County, where minor and specialty crops are increasing in acreage as potato production declines. AGRICOLTNRAL MANAGEMENT STRATEGIES AVAILABLE TO MITIGATE PESTICIDE/GROUNDWATER QUALITY PROBLEMS Irrigation Eff iciency Improved irrigation efficiency in New York has limited potential for reducing the movement of pesticides to groundwater. In Suffolk County's sensitive hydrologic environment--that is, highly permeable soils combined with low soil organic matter content, a shallow water table, and substantial precipitation--improved irrigation efficiency would only modestly reduce pesticide leaching.
54 Potato Integrated Pest Management Program Potato production has been a major agricultural activity on Long Island for about 100 years. Unfortu- nately, the monoculture nature of potato farming has led to problems with pest control. Pest populations have increased over the years, and heavy applications of pesticides are required to manage their numbers. Continued use of the same pesticides has reduced their effectiveness because of the development of pest resistance. Aldicarb was quickly accepted by growers when it was first introduced in 1975 for potato produd- tion because it proved highly effective against nematodes as well as the Colorado potato beetle. Since aldicarb was banned in 1979, Long Island growers have relied primarily on the pesticides fenvalerate, endosulfan, and oxamyl. They have increased both the number of pesticide applications and the total amounts applied, resulting in higher costs but not necessarily comparable crop protection. Recognizing the double constraint of the need to control pests and to protect groundwater quality, Cornell University and its Long Island Horticultural Research Laboratory (LIH~L) have instituted a research program to study new methods of pest control for Long Island potato growers. The Cornell University Pest Management Steering Committee began a pilot potato integrated pest management (IPM) program in June 1981. The primary emphasis of this program was to obtain information on monitoring and management of the Colorado potato beetle, which is the major limiting factor in potato production in Suffolk County. The staff at the LIERL has been collecting data to determine levels of infestation by the Colorado potato beetle and the amount of subsequent damage that can be economically tolerated. Knowing the threshold of economic damage, pest management personnel can time spraying more efficiently. Initial work with growers by LIERL staff has been encouraging and suggests that a reduction in the use of pesticides is possible in some circ~,m~tances. In 1982 a crop rotation study included the IPH program to assess its control of Colorado potato beetle popula- tions. Based on the observed data and a knowledge of Colorado potato beetle population dynamics, the LIBRL staff estimated that approximately two to four insecti- cide sprays could be eliminated using a crop rotation that included planting a crop other than potatoes in 1 year.
55 Other methods for reducing the Colorado potato beetle populations being studied by the LIBEL include biological controls and certain cultural practices. Biological controls will probably not become available in the near future. An example of a cultural practice being evalu- ated is an earlier application of herbicides used to kill potato vines prior to harvest. This practice could beneficially reduce the food available to the beetles and diminish the numbers that survive to the next growing season. At the same time, some agricultural management tech- niques to control pests create other problems. To control potato scab, most growers maintain their soils at an acidic pa. This form of control severely limits the rotation options available, however, because many crops of economic interest cannot flourish in highly acidic soils. Thus, agricultural practices developed to control the potato scab on Long Island have fostered the monocultural practices that contribute to the problems caused by the Colorado potato beetle and the golden and root lesion nematodes. Scab-resistant potato varieties exist, but again they are not considered to be as com- mercially attractive as the nonresistant varieties now grown. Best Management Practices for Pesticide Use Using BMPs to prevent groundwater contamination from pesticide usage is especially critical in a highly sensi- tive hydrologic environment like Long Island. The range of practices and management options previously discussed in Chapter 1 for California are equally relevant and important for groundwater protection in Suffolk County. However, it must be recognized that in some environments a combination of soil and hydrologic characteristics will make it practically impossible to prevent the movement of highly soluble organic chemicals through the vadose zone to groundwater. In those environments, nonchemical alternatives for pest control and the use of resistant crop varieties are critically important if groundwater quality and crops are to be protected.
~6 MODELS TO PREDICT THE TRANSPORT AND ENVIROWENTAL FATE OF PESTICIDES Considerable work is being done at Cornell University on models to predict the transport and environmental fate of pesticides, but few data exist to validate solute transport models under field conditions. Several models have been developed, however, to predict the downward movement of pesticides through the unsaturated zone. Examples of models currently available to predict pesti- cide persistence and movement in the soil/water environ- ment include the Pesticide Analytical Solution (PESTANS ) I, PESTANS II, and the Pesticide Root Zone Model (PROM), developed by EPA; and Transport of Pesticides in Soil (TOPS), developed at Cornell University. These models generally compute the rates of leaching and degradation as a function of tome. The PESTANS I model is a one-dimensional steacy-state model that is limited to projecting vertical movement through the unsaturated zone. It is computationally simple to run and is used to evaluate the relative groundwater contamination potential of various pesticides. PESTANS II is a two-dimensional transient numerical model that will predict both horizontal and vertical movement of water and solutes. This model allows the user to vary degradation rates and soil absorption with depth. Additional input data on water flux and soil characteristics throughout the system allow separate predictions of the rate of leaching through the root zone and the vadose zone, as well as calculated concentrations in the saturated zone. PESTANS II requires much more hydrogeolog~c input data, is more complex to run, and requires considerably more computational time than PESTANS I. The PROM is a one dimensional, transient hydraulic model for evaluating the movement of pesticides within the root zone and the lower unsaturated zones. PRIM is linked with precipitation and soil data bases to estimate leaching of pesticides. The TOPS model was developed to simulate the vertical transport of aldicarb to groundwaves on Long Island. It generally requires the same input as the PESTANS models, and the output is in a similar format. In some models--for example, PESTANS I--the transport processes are greatly simplified so that the model can be run with minimal data. This simplification can result
57 in misleading projections, however. In other models-- for instance, PESTANS II--the attempt to take all para- meters into account requires such large amounts of specific information that data may not be available nor practical to obtain. Thus, more comprehensive modules may also lead to unsatisfactory results. Soil heterogeneity, concentration of macropores, and the level of microbial activity are problems that have proved difficult to incorporate into models. Pesticide uptake by plants has been largely ignored in most models because it was considered insignificant relative to other pathways. Some scientists, however, believe that estimates of plant uptake should be included in models to better simulate the environmental fate of pesticides. Because of these shortcomings, many professionals are skeptical of the usefulness of current models in field situations. Continued model development and field veri- fication are required before simulation models will be fit to replace soil and groundwater monitoring as the primary tool for assessing the environmental fate of a pesticide. Nevertheless, researchers believe simulation models will become important regulatory and management tools in the future. Because of the extreme complexity of agroecosystems, it seems inevitable that simulation models will be required to integrate the various processes that determine a pesticide's ultimate environ- mental fate.
