Pesticide fate and transport monitoring and modeling for paddy fields

1. Research activities of Watanabe’s lab Pesticide fate and transport monitoring and modeling for paddy fields Hirozumi Watanabe, Ph.D. Tokyo University of Agriculture and Technology (TUAT) 3-5-8, Saiwaicho, Fuchu, Tokyo 183-8509 Japan Phone/Fax +81-42-367-5889 email pochi@cc.tuat.ac.jp

2. Outline • Pesticide runoff from rice field • Background • Current condition • Research opportunities • Pesticide fate and transport research • Plot scale monitoring and modeling • Watershed scale monitoring and modeling • Model system approach

3. Paddy field in Japan ( as 2001) Pesticide shipment in Japan農薬学事典　2001，ｐ31 72% 49% Current state of rice pesticide used in Japan • Half of the total domestic pesticide is used for paddy field in Japan • More than half of agricultural land is used for paddy fields • Rice pesticide is probably main non-point source pollution of surface water in Japan.

4. Pesticide Registration http://www.greenjapan.co.jp/greenjapan.htmグリーンジャパン研究会 • In Japan, more than 200 pesticide products with more than 15 active ingredients have been registered each year .

5. Increased variety of pesticide products New design for saving labor costs Pesticide fate also depends on its design and type of application. So many kinds of products and their various design make pesticide fate study very complex and difficult. In order to help cooperate with pesticide industry as well as satisfy the public demand for environmental safety and quality, we are responsible to develop fast and efficient methods and tools for the pesticide fate and transport research. Time of application and design of active ingredients • Pesticide fate depends on its design and type of application

6. Pesticide Runoff from Paddy Field • Pesticide directly applied to paddy water • Inappropriate water management • Paddy field runoff may lose more than 35% of applied mass to surface water, while Upland field lose less than 10% of applied Typically used herbicide, mefenacet concentrations in a secondary drainage canal increased as corresponding to the application period during or shortly after the rice transplant and its peak concentration often exceeds environmental water quality standards recommended by the Ministry of the Environment Japan. Mefenacet concentrations in drainage canal WQS

7. 5 7 6 4 3 Pesticide Conc.(ug/l) in Sakura River Basin 350km2 about 20% is paddy field(ByS. Ishihara et al. 2000, NIAES) 3 4 Corresponding to the early season of rice production during late April to late June, commonly used herbicides are detected up to a few ppb level in Japanese rivers. The time and size of peaks are different among the active ingredients depending upon the time and location of the application.

8. New Drinking Water Quality Standards imposed by Ministry of Health, Labor and Welfare, 2003 • Pesticides （1.3-dichloropropane, simazine, thiram, benthiocarb）has removed from the regulation • Pesticides will be monitored and regulated by the integrated concentration of detected pesticides in the river basin. Possible target pesticides are selected from 101 pesticides.

9. Water Holding Requirement in California Rice Production In Sacrament river basin in California, water holding requirement was imposed on rice farmer. Imposing holding water requirement successfully reduced the pesticide concentrations in the streams. California also concerns about seepage runoff from paddy field. In Japan, farmers awareness of the water quality control seems very limited since there is very limited extension or education programs for the pesticide runoff. One popular source of information is the water holding recommendation of 3-4 days after the application in pesticide product label, however more and appropriate extension of pesticide runoff control to the farmer is necessary in order to conserve the water quality Water holding period for molinate is 28 days, thiobencarb is 30 days CDPR report 2002 ( http://www.cdpr.ca.gov)

10. Monitoring and Modeling for Pesticide fate and transport • Pesticide fate in a paddy field • Plot scale monitoring • Plot scale simulation model (PCPF1) • Pesticide transport in paddy field watershed • Watershed scale monitoring and modeling • Model system for analyzing pesticide fate and transport

11. Field MonitoringMefenacet dissipation in paddy field from May 13 to July 4 in 1998 at NIAES For pesticide fate study in a paddy field that we conducted in 1998 and 1999 consist of 1). Plot scale monitoring and 2). Plot scale simulation model (PCPF1). This study was conducted at National Institute of Agro-Environmental Sciences in Tsukuba, Japan. We were responsible for monitoring pesticide fate in paddy field and for developing a simulation model for predicting pesticide concentration in paddy plot. Water balance data Solar and UV-B radiation pH, Eh, Temp. Pesticide concentrations

12. Conceptual pesticide fate and transport processes in paddy water and surface soil. Evapo-transpiration Precipitation Volatilization Irrigation Drainage Photolysis Biochemical degradation Paddy Water Desorption Dissolution Adsorption Pesticide Source Layer（１cm） Biochemical degradation Percolation Desorption We conceder a conceptual pesticide fate and transport processes in paddy water and surface soil. Upon pesticide application of granule pesticide, pesticide is subject to dissolution in paddy water and then, adsorption in paddy surface soil and partition between paddy soil and water proceed towards the equilibrium condition. However, as irrigation, precipitation and drainage dilute the pesticide concentration and concentration gradient between surface soil and paddy water proceed, pesticide desorbs from paddy soil in order to decrease the chemical potentials between two compartments. Pesticide also desorbs below the surface soil layer as paddy water percolates. Pesticides in paddy water as well as paddy soil are subject to photodegradation, volatilization (paddy water only) and biochemical, and these process also affect pesticide concentration in both compartment.

13. Simulation model for pesticide concentration in paddy field（PCPF1） PCPF-1model input data sheet PCPF1 model is a conceptual lumped model simulating the pesticide concentration in paddy water and 1cm deep surface paddy soil. The model is programmed by visual basic application and operated as a macro in Microsoft Excel. The PCPF1 was validated with several commonly used herbicide in Japan. Simulated and observed mefenaset concentrations in paddy water (above) and paddy surface soil (below)

14. Continuous Irrigation and Drainage Higher Drainage Gate Best Management for controlling pesticide runoff from paddy plots Cumulative Herbicide Losses by Overflow Drainage Intermittent irrigation Significant rain events Figure shows PCPF1 simulations for evaluating the scenarios for different management practice. Continuous irrigation and drainage scheme loses significant amount of pesticide especially in earlier period as compared to intermittent irrigation scheme. Further more, model calculation implies that higher drainage gate may prevent pesticide runoff when significant rain events by storing rainwater and preventing surface discharge.

15. Best Management for controlling pesticide runoff from paddy plots --- Experimental Automatic irrigation vs. Continuous drainage In Tokyo University of Agriculture and Technology, we conducted the monitoring experiment for the evaluation of Best Management Practice for controlling pesticide runoff from a paddy plot from 2001. The objective of this study is to monitor and evaluate pesticide runoff from paddy field managed by automatic irrigation scheme and continuous irrigation-drainage scheme. The monitored variable consist of water balance such as irrigation, drainage, paddy water depth, rainfall, evapotranspiration as well as pesticide concentrations in paddy water and paddy soil during the monitoring period of 35 days.

16. Automatic irrigation Continuous irrigation and drainage 48% Degradation 13% 38% 0.01% Paddy water 0% 0.01% Drainage Drainage Soil surface 4.7% 4.7% 47% Percolation 44% Mefenacet mass balance in paddy field during monitoring period Mefenacet mass balance indicate that continuous irrigation-drainage scheme lost 38% of applied pesticide whereas automatic irrigation scheme lost no pesticide since it control the paddy water depth and did not have any surface drainage during the monitoring period. In general, pesticide fate in paddy field managed by water holding scheme such as automatic irrigation scheme in this experiment indicate that more pesticide is kept and degraded within the field as compared to water releasing scheme. Such as continuous irrigation-drainage. It is recommended that water holding scheme by Intermittent irrigation using an automatic irrigation system is the best management practice for controlling the pesticide runoff from paddy field

17. Monitoring and modeling of pesticide transport in paddy field watershed ( 10ha paddy block) ( 97ha paddy watershed) Watershed monitoring and modeling study for the pesticide transport in paddy field watershed from 2002. The objectives of this study are 1). Monitor and investigate pesticide fate and transport characteristics in paddy field watershed; 2). Recommend the Best Management Practices (BMPs) for controlling pesticide runoff into aquatic environment in Japanese rice paddy production 3). Develop a simulation model for the pesticide transport in paddy field watershed.

18. Pesticide concentrations in different scales Plot 0.01 ha Paddy plot Drainage 5ha-paddy block Stream 97ha-watershed In the paddy field watershed, 15 rice herbicides were detected. Peak concentration raged depending on the pesticide and significant concentrations occurred from may until early June. Pesticide concentrations ranged in different scale. Plot scale raged up to about 800 ppb, 5ha scale, up to about 30 ppb, 97ha watershed scale, up to 7ppb, and for Sakura river scale it ranges up to a few ppb.

19. Height of drainage gate Rainfall Wind Over Drainage 1cm Drainage gate Paddy field Canal Water management practice in plot 1 ( 2002) • Continuous irrigation : 10% • Intermittent irrigation : 90% • However paddy water depth had been keptless than 1cm from drainage gate in most of the monitoring period. High potential of pesticide runoffuponsignificant rainfalland strong wind. Low drainage gate

20. Watershed discharge（above）and Integrated detected pesticide loss（below） Increased discharge in significant rain events Increased pesticide loss in significant rain events Watershed discharged in creased during the significant rain events in upper figure. During the period when pesticide concentrations were high, great pesticide loss occurred with watershed discharge (lower figure). Controlling runoff from paddy field during significant rain events is important for preventing pesticide losses from the watershed.

21. Development of simulation model for pesticide transport in paddy field watershed • Pesticide concentration paddy plot : PCPF-1 model • Paddy block: Pesticide Treatment Group ( PTG) Model output

22. Tokyo University of Agriculture and Technology Graduate School of Agriculture (Japan) National Institute for Agro-Environmental Sciences (Japan) Research Institute for Agricultural and Environmental Engineering, (Antony , France) NEW COUPLED MODEL OF PESTICIDE FATE AND TRANSPORT IN PADDY FIELD TOURNEBIZE Julien, WATANABE Hirozumi, TAKAGI Kazuhiro, NISHIMURA Taku • This project was supported by SAKURA PROJECT 03-04: • Scientific Exchange between French and Japanese researchers and financial support provided and managed by Egide (French Association for foreign research) and JSPS (Japanese society for Promotion of Science) • General Objectives: • Fate and behavior of pesticide in paddy field • Assessment of pesticide residues in soil during one full crop year • Specific Objectives • Coupling PCPF-1 and HYDRUS 2D (SWMS_2D): percolation and concentration • Test and calibrate the new Model for hydraulic functioning and tracer experiment then validate for the pesticide fate and transport of pretilachlor

23. Coupling PCPF-1 and SWMS • Hydraulic Calculation in Water Balance • Ponded Water Depth from PCPF 1 Boundary Condition h(t) in SWMS • Water Flux from SWMS  Percolation rate in PCPF 1 • Solute Calculation • PCPF module: solute concentration in surface water and Pesticide Source Layer Boundary Condition C(t) in SWMS • Solute Transfer in soil  Mass Balance 16 6 27 20

24. Pretilachlor Reductive soil layer Puddled layer (1-17 cm) Kd=13.0 l/kg Degradation rate (2 simple FOK halflife) • 6 days (0-21 DAHA) • 23 days (22-63 DAHA) Oxydative soil layer Hard pan and non-puddled layer Degradation rate 220 days (Fajardo et al, 2000)

25. Research needs and Opportunities Background Research needs • Monitoring pesticide fate and transport • Scale issue • Surface water and Ground water • Development of analytical tools • Simulation models • Lysimeter • Database • Rapid chemical analysis • ELISA • Public concern for water quality • Regulations • Water quality program • PRTR program • Increased variety of pesticides • Limited Extension Program in Japan

26. ET Irrigation Drainage Kdiss, Kcom Cpw Percolation Model system for analyzing pesticide fate and transport 1.Micro-paddy lysimeter 2.Simulation model Simulate pesticide fate in paddy field Determination of governing parameter A model system for rapid analysis of pesticide fate and transport is being developed. The system consist of a micro-paddy lysimeter (MPL), a simulation model to determine pesticide fate parameters, and parameter database for different scenarios. This system has great advantage in analyzing pesticide fate parameters within a two to three weeks with only one set of experiment over the conventional method usually take more time and experiments as well as expenses. • Parameter data base for different scenario and location

27. １）Micro-paddy lysimeterSimulation of pesticide fate in paddy field Water balance tests

28. Drainage canal Paddy plots River Risk Assessment • Chemical parameter data base • Pesticide use data • Metrological data • Hydrological data Watershed scale model is also included in the model system so that reliable pesticide fate and transport prediction make realistic evaluation and development of BMP’s and environmental risk assessmentsis possible.

29. Happy Time!