Agrochemical Fate and Exposure
Through rigorous research, field investigations, spatial analysis, and modeling, Stone assists agrochemical companies in evaluating the fate of their crop protection products in the environment. Our dedication to good science and client service ensures sound study design and cost-effective results in support of state, national, and international registration of pesticides. Our services include:
- • Agrochemical Field Studies
- • GIS Spatial Analysis
- • Environmental Fate Modeling
- • Quality Assurance and GLP
- • Study Directorship and Project Management
Agrochemical Field Studies
Stone is at the forefront of developments in the pesticide environmental fate arena. Site-specific investigations demand expertise in experiment design, experience with the latest instrumentation, and well-trained and dedicated staff committed to Good Laboratory Practice (GLP) standards. As one of the largest companies performing field studies for pesticide registrants, we have the capacity and staff to mobilize quickly to a field site. We are expert in finding the right sites to meet your study objectives, and in characterizing, instrumenting, and monitoring those sites. We offer our clients superior reporting services that detail study methods and carefully organize and present study data in reports tailored to client specifications.
One of Stone’s greatest strengths is implementing large-scale monitoring studies of surface water and groundwater resources for both public and private drinking water supplies. Over the years, we have developed (and continually update) efficient project management systems, collected environmental data sets, and formed a network of field and research contacts that enable us to effectively coordinate these efforts. Our staff receives ongoing training in project management, including protocols, work plans, communications, organization, new technologies, GLP, and financial tracking. Large-scale studies we have performed include community drinking water monitoring programs involving as many as 200 community water systems, nationwide retrospective studies of potable water wells and monitoring wells, and multi-state field runoff studies.
We are flexible in our approach. Stone assists with any phase of a study, from collecting samples when a client is shorthanded, to conducting all the fieldwork according to a protocol established by the client, to fully designing and implementing the study in consultation with the client. At Stone, the focus is on meeting clients’ needs.
There are unique aspects to every study, but most field studies fall into one of six categories:
- • Edge-of-Field Runoff
- • Simulated Rainfall Runoff
- • Surface Water Monitoring
- • Community Drinking Water Monitoring
- • Prospective Groundwater Studies
- • Retrospective Groundwater Monitoring
Edge-of-Field Runoff Studies
Stone has conducted nine studies quantifying runoff losses of crop protection and lawn care chemicals following rainstorms and irrigation. The objective of these studies was to assess the runoff potential of pesticide products under actual use conditions. In our most recent study, we qualified and instrumented 20 sites throughout the Midwest, trained contractors and growers to collect samples, and managed all sampling activities for the duration of the growing season. We set up more than 100 siphon-type runoff collectors at the sites, and instrumented five sites with Sigma autosamplers and tipping bucket rain gauges.
In selecting sites for a runoff study, we identify regions with high product sales. We meet with farmers in these regions and characterize potential sites by determining catchment area, treatment area, soils, field slope, cropping practices, and other factors that influence runoff generation and chemical transport. We establish sampling points proximal to existing channels and culverts that collect and convey runoff. Our sampling methods range from inexpensive, low-tech approaches involving grab sampling, siphon-type runoff samplers, and nonrecording rain gauges to higher-tech installation of weather stations, flumes, stage recorders, and autosamplers. Stone assists clients in designing experiments to result in a cost-effective and technically sound study.
Simulated Rainfall Runoff Studies
Relying on natural rain can be problematic and expensive for those conducting a runoff study. Everyone in the industry knows of a runoff study in which no runoff was generated, or, conversely, in which a massive event wiped out sampling equipment, ruining the experiment. Getting a natural runoff event of appropriate magnitude within a specific time period following product application is a matter of luck. Use of a rainfall simulator eliminates the risks associated with fickle weather, providing control over the timing, intensity, and duration of rain.
From a logistical standpoint, using simulated rainfall guarantees that the test site is well staffed and that sampling equipment is ready when an event occurs. Because the timing is prescribed, site conditions may be fully characterized at the critical time immediately prior to the runoff event. Specific site conditions may also be achieved by irrigating the site to increase soil moisture or by mowing or using other crop management practices. Perhaps the most compelling reason for using simulated rainfall is that by standardizing rainfall intensity and duration, we vastly improve our ability to compare results among multiple experimental treatments and test sites.
Stone began offering simulated rainfall runoff studies when it acquired the rainfall simulator technology developed by PTRL East. We have since conducted five small-scale runoff trials using simulated rainfall. We’ve examined and compared multiple experimental treatments, and tested different product formulations, product application methods, and runoff mitigation measures. We have the equipment and experienced staff ready to perform a runoff experiment at your direction.
Surface Water Monitoring
Between the edge of a farm field and a downstream water treatment plant is a network of drainage ditches and streams. We monitor the water and biota in these perennial streams to assess the potential impact of pesticides on aquatic animals and plants. We conduct stream sampling at this intermediate scale, where environmental concentrations of a pesticide need to be measured for comparison with ecotoxicological levels of concern.
Stone conducts probabilistic assessments to identify stream reaches where pesticide concentrations are predicted to exceed regulatory levels of concern. We use several models (SWAT, WARP, PRZM/EXAMS) in combination with GIS to target certain reaches for monitoring on the basis of product use, crop, meteorological, soils, and other data. We instrument sampling stations with autosamplers and flow monitoring equipment, or rely on a schedule of grab sampling, with flow data derived from public sources. No standard exists in the pesticide fate field for surface water monitoring studies; therefore, Stone is particularly interested in working creatively with registrants to formulate solid experiment designs.
Community Drinking Water Monitoring
With 13 drinking water monitoring studies successfully implemented and 11 completed, we have led the industry in conducting such studies since 1994. These studies have involved several hundred community water systems (CWSs) across the US. We have worked with the Acetochlor Registration Partnership on the largest such study yet conducted, which involved almost 200 CWSs and spanned a period of seven years. Our smallest study involved just five systems sampled over the course of a year to address a product registration issue in a specific region.
Over the last 10 years, we have developed and refined efficient procedures to select and characterize vulnerable CWSs, train sampling personnel, and manage sampling at participating CWSs. Integral to the system selection process is the use of a Geographic Information System (GIS) to locate the CWSs in each state, to delineate watersheds for the source waters used by these systems, and to characterize land use, product use, runoff potential, and other spatial factors that contribute to vulnerability. Stone has created custom tools for use with ArcGIS that that efficiently query, map, and summarize crop data, soils data, land use, and historical precipitation records. The objective is to winnow, through an orderly and defensible process, the approximately 10,000 community water systems relying on surface water sources in the US to a representative number of potentially vulnerable systems.
Since surface drinking water monitoring studies rely heavily on the cooperation of the employees of the CWSs, we place a great deal of emphasis on engaging CWS personnel and supporting them with supplies and logistical help throughout the study period. We make sure these employees are well trained in the sampling procedures and relevant aspects of GLPs. We provide a toll-free number so they can call Stone for assistance at any time and speak with a project scientist. We prepare field notebooks customized for each CWS containing sampling/chain-of-custody forms, bottle labels, prepaid shipping airbills, and sampling instructions. We use FedEx tracking software customized by us to ensure that samples are taken on time and delivered directly to the lab. If there is a problem anywhere in the system, we identify it quickly and make arrangements to correct it. We recently completed a study in which more than 2,400 samples were collected and shipped to an independent laboratory over a three-year period.
Prospective Groundwater Studies
Stone has implemented 17 prospective groundwater (PGW) studies in 10 states, representing all the major agricultural regions of the country. PGW studies are typically multi-year, intensive field trials; therefore, registrants need a contractor with staying power and experience—two hallmarks of Stone. We also have strengths in hydrogeology and project management, which we apply to these studies. All of our studies submitted to date have been accepted by EPA.
Many of the PGW studies Stone has performed are on sites considered realistic worst-case settings: Selected sites typically have coarse-textured soils and shallow groundwater. However, several of our more recent PGW studies are on sites of intermediate vulnerability. These sites were selected through extensive vulnerability analyses we performed using GIS and PRZM modeling to identify areas that met specific vulnerability criteria. This probabilistic approach allows us to rank the relative vulnerability of field areas across a region, basing the rankings on the properties of the pesticide and field soils. This greatly improves our ability to interpret and extrapolate from study data. We characterize in the field the sites indicated by the vulnerability analysis to confirm the accuracy of the data used in the ranking.
Stone maintains a readiness to initiate PGW studies. We are familiar with the latest instrumentation and constantly refine our sampling procedures for improved efficiency while maintaining the highest sample integrity.
Retrospective Groundwater Monitoring
Stone excels in running successful retrospective groundwater monitoring (RGW) studies, having implemented six studies in 16 states, and sampled approximately 800 wells. We selected existing potable wells in four of these studies and installed monitoring wells in two. We are proficient in every aspect of these studies, from protocol development to reporting and well decommissioning (if necessary). We work closely with client sales representatives, local pesticide applicators, chemical distributors, and crop consultants to implement studies that are technically rigorous while maintaining sensitivity to the local agricultural community.
For our largest study, we identified, characterized, and monitored more than 500 potable wells in five regions. The wells were hydraulically down-gradient of treated fields in areas with vulnerable groundwater conditions. In the spring of 2004, we performed a similar tap water study, selecting 150 potable wells in five regions in the space of a month.
When an investigation demands the use of monitoring wells, we work with federal, state, and local governments to identify existing monitoring wells where possible. If monitoring well installation is warranted, we either contract with local drillers or install them ourselves. In one study, we installed 92 monitoring wells in six states. Stone worked closely with lead state agencies to ensure that the protocol and well locations were acceptable to the specific requirements of each state. We sampled the wells quarterly for three years using dedicated pumps, and finally decommissioned them per state standards.
Stone has the resources to conduct an RGW of any scope in any region of the United States or Canada.
GIS Spatial Analysis
The use of geographic and temporal information to understand environmental conditions is integral to many of our studies. Working with Geographic Information System (GIS) technology, we compile, store, and display enormous amounts of data and perform spatial analyses to guide study design, support product use, and inform all stakeholders. The inclusion of spatial and temporal variables in assessments ultimately saves time and money. When higher-tiered assessments of environmental vulnerability are required, we couple spatial analysis with widely accepted modeling methods to attain a clear, scientifically defensible understanding of the complex landscape.
Our Applied Information Management (AIM) group consists of a core group of scientists who specialize in spatial analysis, data management, and programming to evaluate agrochemical fate and transport. In addition to agrochemical fate and exposure work, the AIM group supports two other water quality groups at Stone. This diverse experience base strengthens the group’s analytical abilities and promotes a more comprehensive approach to achieving optimal results for our clients.
We create our own data sets in addition to those we collect and organize from government and academic institutions, building customized interfaces to ease extraction and manipulation of information imperative to environmental assessments. For clients who demand customized analyses for specific applications, we develop GIS tools that automate repetitive processes—such as summarizing crop, land use, soils, and climate characteristics of watersheds or counties—to increase efficiency and save money.
We have extensive experience working with a full spectrum of environmental databases:
- • Land cover (NLCD)
- • Cropping (NASS and Ag Census)
- • Soils (SSURGO, STATSGO)
- • Topography (NED)
- • Hydrography (NHD)
- • Climate (NCDC, PRISM)
These databases provide the foundation for many of our spatial assessments. Recognizing the need to provide environmental data to large numbers of users, we build Web-based databases and GIS applications, empowering a virtually unlimited number of users with environmental information customized for their application.
Environmental Fate Modeling
Since 1992, Stone has been assisting agrochemical clients with the registration of new chemicals, and the maintenance and mitigation of existing registrations. As a critical part of every registration project, our modeling team is one of the most experienced in the industry in predicting the environmental concentrations of an agrochemical in surface water and groundwater. Our modelers specialize in PRZM, GLEAMS, LEACHP, EXAMS, SWAT, PELMO, PEARL, TOXSWA, and WARP to perform:
- • Drinking water exposure estimates for toxicology risk assessments using surface water and groundwater models
- • Aquatic agrochemical exposure estimates for ecotoxicology risk assessments using surface water models
- • Calibration and investigative modeling for point and nonpoint source environmental fate phenomena
- • Probabilistic risk assessments combining spatial analysis with modeling to look at chemical behavior with spatial and temporal variability
- • Watershed-scale water-quality modeling
- • Statistical methodology for study design, and interpretations of data and environmental fate summaries
Our team has completed hundreds of modeling studies to meet the regulatory requirements of the United States (federal and state governments), Canada, and the European Union.
Quality Assurance and GLP
We are one of the few firms conducting pesticide registration studies with an in-house Quality Assurance Unit (QAU). Our clients don’t have to overtax their own QA staff or hire another vendor to obtain the QA services they need—we do it all under one roof. Not only does this save time, but it also showcases our commitment to data quality and GLP—a commitment that permeates all of our agrochemical registration projects, as well as projects managed by Stone’s other groups.
Our quality assurance manager ensures that GLP standards are met. We have corporate systems in place, managed by our QAU, for maintaining current standard operating procedures, staff training records, job descriptions, office and shop floor plans, and the study master schedule; for checking all data presentations for accuracy (QC); and for archiving study data. We have been audited by both EPA and our clients numerous times. The most recent EPA audit of our facility resulted in a letter of “no findings,” which is the most favorable opinion EPA can render. Our QAU is part of the team at Stone, helping to resolve day-to-day quality assurance issues, assisting project managers with regulatory compliance questions, assisting with study protocol interpretation and maintenance, and ensuring that Stone’s work products are the best they can be.
For more information about Stone’s QA program, please see our brochure (157 KB).
Study Directorship and Project Management
Our project managers serve as principal investigators on field and analytical studies. They receive ongoing training in project management, data compilation and storage, financial accountability, and resource scheduling. Our proven corporate-wide project management and financial tracking systems are integral to all projects, regardless of size or timing. Over the past 12 years, we have established a network of subcontractors that meet our high standards for quality and economy. Where warranted, we incorporate their services into projects and take full responsibility for their contributions, saving the client from duplication of efforts and from distraction by internal tasks.
We also work with our clients as study directors, providing higher-level experience in statistical analysis, experiment design, protocol development, and study conduct. Our study directors advise clients and liaise with EPA and other regulatory groups, and collaborate with our team of chemists, statisticians, and field scientists. We are committed to scientifically defensible projects that use innovative approaches to guarantee successful submissions in accordance with 40 CFR Part 160.
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