Pesticide fate and transport monitoring and modeling for paddy fields

1
Research activities of Watanabes 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_at_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
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??????
?????

• 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
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
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-1 model 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
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
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
Water management practice in plot 1 ( 2002)

• Continuous irrigation 10

• Intermittent irrigation 90

• However paddy water depth had been kept less
  than 1cm from drainage gate in most of the
  monitoring period.

High potential of pesticide runoff upon
significant rainfall and 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)
• Kd13.0 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
Model system for analyzing pesticide fate and
transport
2. Simulation model
1. Micro-paddy lysimeter
Determination of governing parameter
Simulate pesticide fate in paddy field

• Parameter data base for different scenario and
  location

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.
27
1)Micro-paddy lysimeterSimulation of pesticide
fate in paddy field
Water balance tests
28
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 BMPs and environmental risk
assessments is possible.
29
Happy Time!