244 th ACS National Meeting | August 19 th to 23 rd

, 2012 | Philadelphia, PA 

### Monitoring and predicting leaching
and transport of a metabolite from a
field to drinking water abstraction
points

R Sur*, T Oertel † , M Himml ‡ , G Görlitz §

*Bayer CropScience LP, Environmental Exposure Assessment, RTP, NC

§ Bayer CropScience AG, Environmental Modelling, Monheim, Germany

† Stadtwerke Duisburg AG, Germany

‡ GEOBIT Ingenieurgesellschaft mbH , Aachen, Germany

EMPM, March 19 th , 2013 | Washington DCSlide 2 

###  N,N

- dimethylsulfamide (D MS ) is a prominent soil metabolite of t he fungicidal a.i . tolylfluanid

 DMS i s nei ther harmful to man nor to the environment (non

- genotoxic,

non

- toxic , non

- ecotoxic , non

- pesticidal )

 Regulatory r ec ommendations ( wholesomeness limits) for drinking water

concentrations of DMS in Germany (Federal Environment Agency):

 1.0 μg/L ( per m anently )

 10 μg/L ( t em porarily for max. 9 years )

 Long

- term application of the fungicide EUPAREN M on an orchard has resulted in significant amounts of DMS in the groundwater catchment of water works Duisburg (Germany, North Rhine

- Westphalia)

 Concerns were raised by the water works whether the threshold value for DMS in drinking water could be exceeded 

# Introduction

R Sur et al | Drinking Water Modelling |Slide 3 

# Objective

 Develop generi c modelling approach for drinking water exposure assessment (case study)

 Predict duration and distribution of future DMS groundwater contamination in

c atchment for water management purposes

 Derive dilution / t ransfer factors between DMS in groundwater and drinking water

2D

- model  HYDRUS 1D

- model

 PEARL

R Sur et al | Drinking Water Modelling | regulatory approval :

PEC gw or measurement

in 1 m depth under

treated field



### aquifer drinking water well monitoring well

dilution raw water
drinking water protection : measured

concentrationSlide 4 Tolylfluanid

DMST

DMST- acid

DMS  Minor Metabolites

 Bound Residues

 CO 2 , H 2 O, mineral salts DT 50 = 0.7 d

DT 50 = 1.8 d

DT 50 = 1.2 d

DT 50 = 127 d 1 st Metabolite:

2 nd Metabolite:

3 rd Metabolite: 25%

86%

 Formation fraction tolylfluanid

 D MS i s 22% (molar)

 K

oc = 0 L/kg

 No degradation in aquifer 

# Soil Degradation of Tolylfluanid

(20 °C, pF 2)

ideal

tracer

R Sur et al | Drinking Water Modelling |Slide 5 

### significant contributions

from non

- contaminated

downstream water

, surrogate wells in the
upstream area of the galleries were considered

for predictive dw modelling ( ) 

# Catchment

Northern drinking water well gallery

Southern drinking water well gallery DMS

Source Observation

Wells

2.2 km 

###  Groundwater from several

wel ls within two galleries
is abstracted, mixed and processed before supply as drinking water

Hydraulic Gradient:

ca. 1 m /600 m GW Flow 

###  Due to the l arge spatial distribution

of dw wells

, varying mixing ratios and

R Sur et al | Drinking Water Modelling |Slide 6 Soil 3 Soil 1 Soil 2 Soil 5 Soil 4 Soil 1 - 18 Cropping History on 18 Plots

 determines application 

# Source

Soil No. 1+3 (36%) Soil No. 2 (25%) Soil No. 4 (25%)

Soil No. 5 (13%) 1 3 kg/ha

1.5 kg/ha

6 kg/ha

5 kg/ha Application Rates (Euparen M WG, 50% a.s.)

14.4 ha

Euparen M

use from 1993

to 2006 R Sur et al | Drinking Water Modelling |Slide 7 

# Cropping History at Source

R Sur et al | Drinking Water Modelling |Slide 8 

# Soil Distribution at Source

Soil Distribution on Orchard

27% 25% 9% 25%

13%

1%

Soil 1 Soil 2 Soil 3 Soil 4 Soil 5 Soil 6/7

-200 -150 -100

-50

0 min max min max min max min max min max 1 1 2 2 3 3 4 4 5 5 Soil Profile No.Soil depth (cm)

Loam Sandy loam Clay loam Sand 

###  5 different mai n soil profiles on orchard

 Loamy top soil layer (0.7 – 1.8 m) followed by sandy / gravel bottom layer down to groundwater table (4.5 – 6.5 m)

 Significant variability in

thickness of loamy top

soil layers

R Sur et al | Drinking Water Modelling |Slide 9  Discretise orc hard in ca. 50 sub

- plots with same soil and crop ( use ) history

 Calculate mass of DMS and water volume at depth of groundwater table for

each sub

- plot

 Select soil hy draulic parameters based on texture class (ROSETTA PTF)

 Atmospheric boundary c ondition : Local weather data

 Lower boundary c ondition : F ree drainage (variable groundwater table )

 Combine results t o calculate area weighted average concentration of DMS for single plots and entire orchard 

# 1- D Modelling Approach (PEARL)

R Sur et al | Drinking Water Modelling |Slide 10 

# DMS in Leachate (mean over entire orchard)

0 5 10 15 20 25Apr-95Apr-97Apr-99Apr-01Apr-03Apr-05Apr-07Apr-09Apr-11Apr-13Apr-15Apr-17DMS in Leachate (μg/L) Simulation Wet Scenario Simulation Dry Scenario

prediction real weather

 Nearly complete dissipation of DMS from soil by 2011 final application C

mean = 12 μg/L

R Sur et al | Drinking Water Modelling |Slide 11 

# Validation of Leachate Simulation

Mean (area weighted) over all plots with measured data on DMS in leachate

Good agreement between observed and simulated DMS in leachate final application

21 leachate monitoring

sites

R Sur et al | Drinking Water Modelling |Slide 12 -25 -20 -15 -10

-5

0 0 250 500 750 1000 1250 Hydraulic conductivity (m/d)Depth below ground surface (m) Keff - Aggregated Mean (optimised)

Keff - Aggregated Mean (data set) 

# Horizontal Hydraulic Conductivities Aquifer

Experimental Results from 10 observation wells across catchment

 Lognormal distribution of hydraulic conductivities

 Conductivity increases with depth, high variability between wells 

# ∑ ∑

=

i ii
h, eff 

### d dK K

R Sur et al | Drinking Water Modelling |Slide 13 

# 2D Modelling Approach (HYDRUS)5 m10 m Ø 40 m/d

Ø 300 m/d

K

s -0.5 Pressure head (m) 14.5 ∆ 5 m

2800 m

15 m DMS Observation Nodes

       

=        

= 1.00 01

K0 0K

A
2 A
1 A K Tensor of Hydraulic Anisotropy

Porosity: 0.2 Dispersivity - long: 10 m Dispersivity

- vert: 0.1 m

Integral: 1.5 × 10 -3 m/s

R Sur et al | Drinking Water Modelling |Slide 14 

# DMS in aquifer below orchard - observed vs. simulated

17 monitoring

wells  DMS (aquifer) / DMS (leachate) = 1:8 DMS in upper third of aquifer

R Sur et al | Drinking Water Modelling |Slide 15 

## DMS at remote monitoring wells - observed vs. simulated

Source 4 Wells 4 Wells 1.6 km

R Sur et al | Drinking Water Modelling |Slide 16 Source 4 Wells 4 Wells 

## DMS at remote monitoring wells - observed vs. simulated

2.2 km

R Sur et al | Drinking Water Modelling |Slide 17 

# Vertical Cross

- Section of Aquifer

snap-shot June 2008

DMS Concentration

 Gradual vertical m ixing of DMS with increasing distance from source

 Reduced wat er flow in upper part of aquifer

 Monitoring wells close to source overpredict DMS concentrations in aquifer monitoring wells (sampling water from upper aquifer) drinking water well orchard

R Sur et al | Drinking Water Modelling |Slide 18 

# Overall Dilution of DMS

treated

field

distance to groundwater

background

concentration aquifer drinking

water

abstraction

monitoring wells 12 μg/L 12 μg/L

1.5 μg/L 0.5 μg/L

 T ransfer factor of 20 between concentr . in leachate and drinking water well PEC gw (EU regulatory concentration)

Leachate

R Sur et al | Drinking Water Modelling |Slide 19 

# Conclusions and Outlook

 The coupled 1D

- 2D model can adequately describe the observed

concentrations of DMS in leachate below the site of application and in
remote drinking water wells

 Significant l eac hing of DMS into aquifer predicted / verified to terminate

in 2011

 Exposure of dr i nking water predicted to remain constant until 2015 and

to terminate about 2025

 DMS will not ex c eed the threshold value in drinking water

 In t otal, a d ilution / transfer factor of ca. 20 between the concentration of

DMS in groundwater recharge and in drinking water was calculated

 The mo delling appr oach presented has been extensively validated and

can be useful to estimate drinking water concentrations also of other
agrochemicals

R Sur et al | Drinking Water Modelling |Slide 20 

## Thank you ! (robin.sur@bayer.com)

R Sur et al | Drinking Water Modelling |