### Wisconsin Department of Agriculture, Trade and Consumer Protection

March 2008 

## Final Report on DATCP Evaluation of Renewed Use of Atrazine in Atrazine Prohibition Areas1 Final Report on DATCP Evaluation of Renewed Use of Atrazine in Atrazine Prohibition Areas

Background

Introduction

The DATCP Evaluation of Renewed Use of Atrazine in Atrazine Prohibition Areas (hereafter referred to as the Atrazine Reuse Study) was conducted between 1998 and 2005. The purpose of the study was to gather information to help the department determine if it should consider repealing atrazine prohibiti on areas. More specifically, the main objective of the study was to dete rmine the impact of atrazine use, in compliance with the Wisconsin atrazine ru le, on shallow groundwater in atrazine prohibition areas (PAs).

Groundwater Standard for Atrazine

The Wisconsin groundwater enforcement standa rd (ES) for atrazine total chlorinated residues (TCR) is 3 ug/l (equivalent to parts pe r billion). This sta ndard includes atrazine and its three chlorinated metabolites deethyl atrazine, deisopropyl atrazine and diamino atrazine. The preventiv e action limit (PAL) for atrazine TCR is 0.3 ug/l.

The Wisconsin Atrazine Rule

The atrazine rule, ch. Ag 30, Wis. Adm. C ode (now Ch. ATCP 30, Wis. Adm. Code), was created in 1991 to address atrazine cont amination in Wisconsin's groundwater. This rule restricted the use of atrazine on a stat ewide basis and establis hed PAs where atrazine contamination in groundwater exceeded the ES of 3 ug/l. Over the years, as additional testing found more drinking water wells contam inated by the use of atrazine, additional PAs were established. Currently there ar e 102 PAs in the state covering over 1.2 million

acres.
Repeal Process for At razine Prohibition Areas

The original atrazine rule did not contain a provision to repeal PAs after they were created. In 1998, a change was made to the atra zine rule that allows the department to consider repealing PAs wher e atrazine levels in groundw ater have improved. The department must evaluate the following three co nditions as it consider s whether to repeal a PA:2 • Tests on at least three consecutive gr oundwater samples, drawn from each well site in the prohibition area at which the atrazine concentration previously exceeded the groundwater enforcement sta ndard, show that the atrazine TCR concentration at that well site has fallen to and remains at not more than 50% of the enforcement standard. The three consecutive samples must be collected at intervals of at least six m onths, with the first sample being collected at least six months after the effective date of the prohibition area.

• Tests conducted at other we ll sites in the proh ibition area reveal no other atrazine TCR concentrations that exceed 50% of the enforcement standard.

• The department determines, based on cred ible scientific evidence, that renewed use of atrazine in the prohibition area is not likely to cause a renewed violation of the enforcement standard.

To evaluate the first condition, the department tests wells in atrazine PAs that have exceeded the ES as part of an annual survey called the Exceedence Survey. For the third condition, the department conducted a seven year study to evaluate the impacts on groundwater of renewed atrazine use in PAs. This study, called the Atrazine Reuse Study, is the focus of this report. The s econd condition will only be evaluated if the department determines that conditions one and three have been met.

Study Design

With the help of the Atrazine Technical A dvisory Committee, the department designed a study to evaluate the third repeal condition. The basic design was to conduct groundwater monitoring at repr esentative agri cultural fields in atrazine PAs where atrazine use was allowed on an experimental basis. Seventeen growers with fields in older (1993 or 1994) PAs throughout the state (s ee figure 1) provided the sites for the study. These growers agreed to grow corn and use atrazine on the fi elds selected for the study. The fields that were selected met so il, topographic and geologic conditions that allowed the study to be comple ted in a relatively short ti meframe and at a reasonable cost. The groundwater beneath the selected fiel ds was tested quarterly for five to seven years utilizing three shallow monitoring we lls located within each of the fields.

The soils of the study fields were grouped into coarse and medium texture categories following the scheme in the atrazine rule fo r determining maximum application rates. Candidate fields had to meet th e following selection criteria:

• slope less than 5%

• water table in unconsolidated materials

• unsaturated zone of equal or greater permeability than the overlying soil3 • depth to groundwater less than 30 feet

• water table not within the root zone of the crop being grown

The growers agreed to use atrazine on the m onitored field at least three times during the study and were encouraged to use the highest legal use rate in Wisconsin. Herbicide products containing cyanazine or simazine were not allowed to be used during the study since they produce two of the same chlorinate d triazine metabolites as atrazine. Other pesticides and fertilizers were applied as needed. The grow ers selected the tillage and application method best su ited for their operation.

Figure 1. Location of the Seventeen Study Sites in the Atrazine Reuse Project

Since the study fields were lo cated in atrazine PAs, the si ze of the area where atrazine could be used under a research permit was li mited to 10 to 40 acres. Three monitoring wells were installed in a line wi thin the area to be treated w ith atrazine. Each well had a 10 foot screen with 3-4 feet of open interval below the wate r table. Wells were sampled following established sample collection pro cedures designed to minimize the possibility of cross contamination. Department chain- of-custody requirements were followed to ensure adequate documenta tion of laboratory results.4 Of the 17 sites in the study, one was exclude d from the analysis for not disclosing the presence of a septic drain field in th e study field and for not following other study protocols. Of the remaining 16 sites, seve n did not meet the requirement of applying atrazine at least thr ee times during the course of the study because of changes in the planned crop rotation or other reasons. These seven sites with only one or two applications of atrazine are considered separa tely in the analysis pr esented in Tables 2b and 3b. Results from the three wells at all the sites are shown in gra phs in Appendix A.

Sample Analysis
Syngenta, a manufacturer of atrazine, performed the laboratory analyses for the study. The limit of quantitation (LOQ) for atrazine, deethyl atrazine, deis opropyl atrazine, and diamino atrazine was 0.10 ug/l. DATCP c onfirmed the analyses by collecting split samples annually for analysis at the department’s laboratory.

Study Results

Table 1 summarizes the results for the 16 site s in the atrazine reus e study. Atrazine TCR was detected at all the sites and the 3 ug/l ES was exceeded at 12 out of 16 sites. The median atrazine TCR concentrations for th e 16 sites ranged from 0.3 to 9.36 ug/l. It appears that cyanazine or simazine use at eight sites in the three years prior to the study had a significant impact on the atrazine T CR results during the study at those sites.

Table 1. Summary of results from the atrazine reuse study

Site Name County Soil Texture # of samples # of samples over ES for TCR # of wells over ES for TCR Concentration Range (ug/l) MedianConcentration (ug/l) 09A Chippewa medium 65 7 3 0.69-3.89 2.2 13C Dane medium 83 38 2 0.45-10.4 2.8 13J Dane medium 84 10 2 0-11.36 1.24 23I* Green medium 72 72 3 4.28-18.5 9.36 24H Gr. Lake coarse 72 20 3 0-5.69 1.69 27B* Jackson medium 63 20 1 0.17-8.9 1.2 29L Juneau medium 65 10 2 0-23.6 1.41 39K* Marquette coarse 66 64 3 0.58-12.7 5.52 45F* Outagamie coarse 66 25 3 0.54-6.13 2.9 50M* Portage coarse 71 0 0 0-2.6 1.06 50N* Portage coarse 84 2 1 0.11-4.12 0.98 56R St. Croix medium 68 1 1 0.28-3.16 1.13 65D Walworth coarse 72 0 0 0-0.46 0 69P* Waupaca coarse 72 55 3 1.15-12.6 3.86 70G* Waushara coarse 66 0 0 0-0.83 0.3 70Q Waushara coarse 59 0 0 0-1.25 0.12
* these sites received cyanazine or simazine in one or more of the three years before the

start of the atrazine reuse study5 Results by Site

Tables 2a and 2b summarize the results by st udy site. Two conditions are evaluated in these tables: First, did any of the three we lls at a site exceed the ES for atrazine TCR during the study? Second, for the sites where all three wells started below the ES, at how many sites did one or more wells go above the ES after renewed use of atrazine began?

Table 2a. Results by site for the nine sites w ith at least three applications of atrazine

Condition Number of Sites One or more wells at the site had at least one result over the ES during the study 9 of 9
All wells started below the ES at the site, with one or more wells later above the ES 4 of 4

Tabl e 2b. Results by site for the seven sites w ith one of two applic ations of atrazine

Criteria Number of Sites One or more wells at the site had at least one result over the ES during the study 3 of 7
All wells started below the ES at the site, with one or more wells later above the ES 1 of 5

Wells at some of the sites started out above the atrazine TCR enforcement standard even though atrazine had not been appl ied for at least five years be fore renewed use of atrazine began. This is likely due to th e long half-life of atrazine in soil and water or the use of cyanazine or simazine, which produce two of the same metabolites as atrazine, in the years prior to the study. Eight of the sixteen study sites had documented use of cyanazine or simazine in the three y ears before the study began.

Results by Well

Another way to summarize the results is by well instead of by site. These results are presented in Tables 3a and 3b. Two conditions are evaluated in these tables: First, how many wells that started below the ES later exceeded the ES? Second, for wells that started over the ES, how many increased by at least three μg/l (the amount of the ES) once renewed use of atrazine began? The resu lts for these conditions are also presented by soil texture.6 Table 3a. Results for 27 wells at the nine site s with at least three ap plications of atrazine

Condition Number of Wells Wells that started below the ES and later exceeded the ES 9 of 16

Wells that started above ES and later increased by at least 3 μg/l 9 of 11

Wells at sites with medium texture soil that started below the ES and later exceeded the ES 6 of 11

Wells at sites with coarse texture soil that started below the ES and later exceeded the ES 3 of 5

Table 3b. Results for 21 wells at the seven site s with one or two app lications of atrazine

Condition Number of Wells Wells that started below the ES and later exceeded the ES 5 of 19

Wells that started above ES and later increased by at least 3 μg/l 1 of 2

Wells in medium texture soil that started below the ES and later exceeded the ES 3 of 5

Wells in coarse texture soil that started below the ES and later exceeded the ES 2 of 14

Conclusions

Based on the results of the study, the department concluded that rene wed atrazine use in PAs would likely lead to exceedences of the enforcement standard. Because of this finding, the department determined that conditio n three of the repeal process had not been met and decided not to consider repealing any PAs at that time.7 Appendix A. Site Graphs for the 16 Sites in the Atrazine Reuse Study

Site 09A - Medium Soil Texture (soil test coarse) In Prohibition Area Since 1995

0 1 2 3 4 5 6

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003
DateTCR ug/l

09A1 09A2 09A3 Atrazine Application Enforcement Standard

Site 13C - Medium Texture Soil In Prohibition Area Since 1995

0 1 2 3 4 5 6 7 8 9 10 11

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003 12/30/2004TCR ug/l

13C1 13C2 13C3 Enforcement Standard Atrazine Application8 Site 13J - Medium Texture Soil In Prohibition Area Since 1995

0 1 2 3 4 5 6 7 8 9 10 11 12

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003 12/30/2004TCR ug/l

13J1 13J2 13J3 Atrazine Application Enforcement Standard

Site 23I - Medium Texture Soil In Prohibition Area Since 1996

0 5 10 15 20

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

23I1 23I2 23I3 Enforcement Standard Atrazine Application9 Site 24H - Coarse Texture Soil In Prohibition Area Since 1993

0 1 2 3 4 5 6

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

24H1 24H2 24H3 Enforcement Standard Atrazine Application

Site 27B - Medium Texture Soil Used Atrazine on Field in 1996

0 1 2 3 4 5 6 7 8 9

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

27B1 27B2 27B3 Enforcement Standard Atrazine Application10 Site 29L - Medium Texture Soil In Prohibition Area Since 1994

0 5 10 15 20 25 30

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

29L1 29L2 29L3 Enforcement Standard Atrazine Application

Site 39K - Coarse Texture Soil In Prohibition Area Since 1993

0 2 4 6 8 10 12 14

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

39K1 39K2 39K3 Enforcement Standard Atrazine Application11 Site 45F - Coarse Texture Soil In Prohibition Area Since 1995

0 1 2 3 4 5 6 7

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

45F1 45F2 45F3 Enforcement Standard Atrazine Application

Site 50M - Coarse Texture Soil In Prohibition Area Since 1994

0 1 2 3

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

50M1 50M2 50M3 Enforcement Standard Atrazine Application12 Site 50N - Coarse Texture Soil In Prohibition Area Since 1994

0 1 2 3 4 5

1/1/1998 1/1/1999 1/1/2000 12/31/200 0 12/31/2001 12/31/ 2002 12/31/2003 12/30/2004TCR ug/l

50N1 50N2 50N3 Enforcement Standard Atrazine Application

Site 56R - Medium Texture Soil In Prohibition Area Since 1994

0 1 2 3 4

1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003 12/30/2004TCR ug/l

56R1 56R2 56R3 Enforcement Standard Atrazine Application13 Site 65D - Coarse Texture Soil In Prohibition Area Since 1993

0 1 2 3

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

65D1 65D2 65D3 Enforcement Standard Atrazine Application

Site 69P - Coarse Texture Soil In Prohibition Area Since 1994

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003 12/30/2004TCR ug/l

69P1 69P2 69P3 Enforcement Standard Atrazine Application14 Site 70G - Coarse Texture Soil In Prohibition Area Since 1993

0 1 2 3

1/1/1998 1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

70G1 70G2 70G3 Enforcement Standard Atrazine Application

Site 70Q - Coarse Texture Soil In Prohibition Area Since 1993

0 1 2 3

1/1/1999 1/1/2000 12/31/2000 12/31/2001 12/31/2002 12/31/2003TCR ug/l

70Q1 70Q2 70Q3 Enforcement Standard Atrazine Application