Categorical groundwater sites

This page is about eight categories of pesticide user whose shallow groundwater Cornell personnel sample more than once per year under agreements with each landowner.

Except for the utility/transportation Rights of Way (RoW) category, the confidential (anonymous) volunteer landowners receive the full detail data about test results on samples from their property, annually. The samples for ROWs are from adjacent property, and the owners of the adjacent land are considered the cooperators and receive the data.

NYSDEC and the public receive an anonymized version of most data with locations highly blurred.

1. Objectives and priority

New York State wishes to know what fraction of routinely used pesticides escapes to immediately adjacent groundwater under different environmental and management conditions. Some escape is inevitable when chemicals are used, outdoors and sometimes even indoors. Some sampling is done close to or even within a pesticide use area, where concentrations in percolating water would be highest if it rains shortly after the pesticides are applied. Farther away from the application area, there is dilution by groundwater recharge from non-applied areas and there is time underground when pesticides will decompose chemically or biologically.

Categorical sites are the highest priority of the 2021-2025 project, providing over 80% of the samples taken.

2. Background about categoricals

The eight categories of pesticide users that NYSDEC wished to recruit were:

Table 1: Categories
Category	Typical pesticide uses
Golf courses	Insecticides, herbicides, fungicides
Sod farms	Insecticides, herbicides, fungicides
Other turfgrass	Insecticides, herbicides, fungicides
Greenhouses	Insecticides, fungicides
Outdoor nurseries	Insecticides, fungicides
Fruit and vegetables	Insecticides, herbicides, fungicides
Vineyards	Insecticides, herbicides, fungicides
Utility and rail rights of way	Herbicides

These sites have differing purposes and usage modes of pesticides. For example, railway rights of way need to keep the rails absolutely free of weeds and trees, thus herbicides are a dominant focus. Golf courses treat their greens and fairways to keep their specialty grasses both uniform and without insect or disease damage. Vineyards have very specialized insect, fungus, and disease control needs.

Several cooperators are Integrated Pest Management (IPM) users. They avoid using chemical pesticides when possible, but do use them selectively based on observations and information about the biology of the pests, diseases, or weeds. Clearly the pesticide residues of IPM sites should be less on average than at more conventional pesticide users. IPM has become mainstream after its initiation nationally in the 1980’s.

We intentionally avoided scrupulously organic farm operations because they do not use pesticides, thus only neighboring properties would contribute pesticides to their groundwater. (There is at least one organic farm involved in our Long Term type of site.)

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3. Design, approach, recruiting

We relied on networking, reconnaissance, and mapping to identify candidates who might be willing to participate.

Most candidates should be in more leaching-vulnerable aquifer areas, such as stream alluvium and glacial outwash soils. Lake sand and beach deposits are also considered more vulnerable. NYSDEC provided a guideline of about 15% of sites that would be in presumed less vulnerable locations: glacial till, lake clay and silt, muckland. (Presumed is a key concept that the project is testing by including a wide spectrum of conditions.)

This is presumed leaching vulnerability, not well vulnerability. Leaching vulnerability means that pesticides that are applied, or escape to outdoors, would have a notable chance of washing downwards in soil to the water table. Well vulnerability, emphasized in earlier Cornell SWL work with NYSDEC, is much about the construction and position of the well. An old dug well in a dairy barnyard very likely gets some manure constituents like pathogens and nitrate into it. A well a hundred feet from the barnyard, drilled hundreds of feet into bedrock, cased and properly sealed, would not be influenced by the barnyard.

Figure 1: Upstate NY counties hosting categorical sites

Table 2: Categorical site attributes (counts) as of June 2023
Attribute	Value	Count
Presumed leaching vulnerability
	High	9
	Medium	7
	Low (muck, glacial till)	5
Soil and shallow aquifer composition
	Sand and gravel (glacial outwash or alluvium)	15
	Drained muck	4
	Gravel/silt loam	1
	Mixed glacial till, gravel and clay	1
Ecoregion
	Allegheny Plateau	8
	Great Lakes Lowland	6
	Ridge and Valley	4
	Coastal (Hudson)	2
	Northeast Highlands	1

4. Sampling categorical sites

We draw samples from a mixture of owner wells, owner ponds fed by groundwater, and temporary shallow wells that Cornell installed and will remove at the end of the project or earlier if the owner wishes.

Table 3: History of sampling categorical sites
When	Comments
Spring and summer 2022	Earlier sites sampled as they joined and had wells installed. Around half of sites sampled first time.
Late fall 2022	Later sites joined and were sampled for first time. Second samplings at the ones sampled in first round.
April-July 2023	All sites sampled for second or third time.

We expect to sample in spring and late fall each year. Upstate’s better travel period is usually from April through November. Given upstate’s largely uniform pattern of precipitation over the seasons, groundwater recharge is greatest and water tables highest in early spring after snowmelt, and in late fall when evapotranspiration is suppressed by lower temperatures and shorter daylight.

We group the sites into four zones to attempt to be travel efficient, from a base in Ithaca (Table 4).

Table 4: Categorical sites sampling routes.
Zone	Direction and reach
West	All land from the Pennsylvania border to Lake Ontario, west to Lake Erie, and west of Ithaca. Eight of 21 sites over two days.
Northeast	From Cortland past Albany to Saratoga Springs and nearly the Vermont border. Five sites over two days.
Southeast	Orange and Ulster County area. Four sites over two days.
Central	Four sites that we visit individually from Ithaca, or grouped. (Three sites from the West zone can also be reached from Ithaca without overnight travel.)

5. Results and interpretations

Interpretations are pending; all concentrations were under 1 microgram/liter with no concentrations of concern.

A tentative surprise is that presumed less leaching-vulnerable muckland sites are showing some pesticide residues. If recharge water was flowing uniformly through the highly organic soil matrix, pesticide residues would be expected to be delayed by adsorbing to the organic matter, for long enough for biochemical processes to degrade them into undetectability.

The DEC laboratory tested for 26 pesticide active ingredients and two degradation products (Table 5). With 107 samples provided (from categorical site groundwater and lakes), this afforded over 3,000 opportunities for positive detections (samples × analytes). In contrast, there were only 32 detections among this set, yielding a detection rate of circa 0.1% (and less than that if only groundwater samples are considered). All detections were at concentrations less than 1 μg/L, and all detections were substantially lower than drinking water standards. Table 6 provides details of those detections for the six categorical sites at which detections were found.

The groundwater of all eight categorial site types was sampled (golf courses, non-golf turfgrass, outdoor nurseries, greenhouses, vineyards, fruit & vegetable farms, sod grass farms and rights of way, Table 1). Positive detections were for one of the two sod farms (Sod-3) on muck soil and a vineyard (Vine-1) in the Allegheny ecoregion. The groundwater under the fruit & vegetable farms (VegF) spread throughout upstate New York had the most detections relatively, in most cases S-Metolachlor or metolachlor degradation products, plus Fluopyram in one sample. Finally, one of the three nurseries (Nur-5) had low concentrations of Metolachlor ESA. For this site, groundwater-fed ponds reflect upgradient conditions, and downgradient Well-1 is near a staging area for tree transport to offsite, had near-saturated conditions during two site visits, and is not far downgradient from two of the upgradient ponds.

The DEC laboratory tested for 26 pesticide active ingredients and two degradation products (Table 5). With 107 sampled provided, this afforded over 3,000 opportunities for positive detections (samples × analytes). In contrast, there were only 32 detections among this set, yielding a detection rate of circa 0.1% (and less than that if only groundwater samples are considered). All detections were at concentrations less than 1 μg/L (Table 4), and all detections were substantially lower than drinking water standards. Table 5 provides details of those detections for the three lakes and six categorical sites at which detections were found. For the four lakes were sampled, samples from three lakes were positive for degradation products or pesticides. All samples in Little York Lake showed a low concentration of Metolachlor ESA. Chautauqua Lake had a low concentration of Imidacloprid in one of four samples. The low concentration of Mefentrifluconazole in one Lake Waccabuc sample may originate from a nearby golf course.

Table 5: Pesticides and degradation products tested for in 2022 samples
Analyte	Type
Metolachlor ESA	Herbicide degradation product
Metolachlor OA	Herbicide degradation product
Acetamiprid	Insecticide
Boscalid	Fungicide
Cloransulam-Methyl	Herbicide
Clothianadin	Insecticide
Dichobenil*	Herbicide
Difenconazole	Fungicide
Dinotefuran	Insecticide
Endothall	Herbicide including aquatic
Ethofumesate	Herbicide
Florpyrauxifen Benzyl	Herbicide
Fluazinam	Fungicide
Flumioxazin	Herbicide
Fluopyram	Fungicide, nematicide
Fluxapyroxad	Fungicide
Halosulfuron-methyl	Herbicide
Imidacloprid	Insecticide
Indaziflam	Herbicide
Linuron	Herbicide
Mandipropamid	Fungicide
Mefentrifluconazole	Fungicide
Myclobutanil	Fungicide
Oxadiazon	Herbicide
Paclobutrazol	Fungicide
Pyrimethanil	Herbicide
S-Metolachlor	Herbicide
Thiamethoxam	Insecticide

*Only tested for in samples from greenhouse sites.

Table 6: First-year (2022) pesticide concentrations (all values as micrograms per L; “<nnn” = not detected, below stated detection limit of nnn)
Well ID	PointInSite	Date Sampled	Fluo-pyram	S-Metolachlor	Oxadiazon	Metolachlor OA	Metolachlor ESA	Imida-cloprid
Sod-3	Well-1	8/15/2022	<0.025	<0.025	<0.025	0.300	0.265	0.028
Sod-3	Well-2	8/15/2022	<0.025	<0.025	<0.025	0.349	0.256	<0.025
Sod-3	Tilebox	10/27/2022	<0.025	<0.025	<0.025	0.799	0.626	0.035
Vine-1	Spring	5/19/2022	<0.025	<0.025	<0.025	<0.1	<0.15	0.044
Vine-1	Well-1	5/19/2022	<0.025	<0.025	0.559	<0.1	<0.15	0.045
Vine-1	Well-1	11/23/2022	<0.025	<0.025	<0.025	<0.1	<0.15	0.051
VegF-1	Well-2	5/17/2022	<0.025	<0.025	<0.025	<0.1	0.748	<0.025
VegF-1	Well-2	10/25/2022	<0.025	<0.025	<0.025	<0.1	0.755	<0.025
VegF-1	Well-1	10/25/2022	<0.025	<0.025	<0.025	<0.1	0.252	<0.025
VegF-4	Well-2	12/4/2022	<0.025	<0.025	<0.025	0.705	0.553	<0.025
VegF-4	Well-1	12/4/2022	<0.025	<0.025	<0.025	0.646	0.217	<0.025
VegF-4	Well-2	9/12/2022	<0.025	<0.025	<0.025	0.575	0.488	<0.025
VegF-6	Well-1	12/14/2022	0.031	<0.025	<0.025	<0.1	<0.15	<0.025
Nur-5	Pond-1	8/24/2022	<0.025	<0.025	<0.025	<0.1	0.214	<0.025
Nur-5	Pond-2	8/24/2022	<0.025	<0.025	<0.025	<0.1	0.222	<0.025
Nur-5	Well-1	10/28/2022	<0.025	<0.025	<0.025	<0.1	0.218	<0.025

Table 7: Pesticides detected in the 2022 sample set.
Active ingredient / analyte	Role as pesticide
Fluopyram	Fungicide and nematicide
Imidacloprid	Insecticide
Mefentrifluconazole	Fungicide
S-Metolachlor	Herbicide
Metolachlor ESA	Herbicide metabolite
Metolachlor OA	Herbicide metabolite
Oxadiazon	Herbicide

Last updated 2023-09-22, sp17 AT cornell.edu