Transport and attenuation of S-metolachlor at the catchment scale Lefrancq M.1, Guyot B.1, Imfeld G.1, Elsayed O.1, Millet M.2, and Payraudeau S.1

[email protected] 1 Laboratory of Hydrology and Geochemistry of Strasbourg (LHyGeS - UMR 7517), University of Strasbourg/ENGEES/CNRS, France

2 Atmospheric Physical Chemistry Department (LMSPC - UMR 7515), University of Strasbourg/CNRS, France

Pesticide Behaviour in Soils, Water and Air (York) September 3rd 2013 Tracking pesticides from sources to sinks

• 70% of herbicides are applied in pre-emergence • Interpretation of transport and degradation at the catchment scale is limited • Need for new tools to assess in situ biodegradation

? ?

Source: AERM, 2012 Specific transformation processes Suspended solids 2 Oliver et al, 2012; Fenner, 2013 How tracking pesticides from sources to sinks?

At the catchment scale Enantiomeric analysis Compound-specific isotope analysis (CSIA)

Enantiomers = different spatial Measures the stable isotope ratio Method orientation of their atoms of a compound

푅 −푆 푅푠푎푚푝푙푒 − 푅푠푡푑 퐸푛푎푛푡푖표푚푒푟푖푐 푒푥푐푒푠푠 = . 100 훿 ‰ = 푆+푅 푅푠푡푑 - Enantioselective degradation Molecules with light isotopes Interpretation - Enantioselective toxicology tend to be degraded faster

- Environmental sciences - 30% of pesticides are chiral Main use (sourcing and degradation of - Ecotoxicological studies pollutants) - Tracking physicochemical processes - Biogeochemistry (carbon and

nutrient cycling) …. 3 Fenner, 2013; Milosevic, 2013; Celis, 2013 S-metolachlor • The principal herbicide used on corn and sugar beet in pre-emergence (Europe)

• S-metolachlor is frequently detected in surface water as well as its degradation products

S-Metolachlor: S: 80 - 100% R: 0 - 20%

*

Chemical structure

Aquatic crustaceans -1 1.4 Acute 96 h LC50 [mg L ] Solubility in water (20°C) [mg L-1] 480

Log Kow (pH 7, 20°C) 3.05 Koc [L kg-1 ] 62 - 372

DT50 (soil) [d] 21 Hydrolysis, photolysis stable

o Henry's law constant (20 C) [] 4.13 10-7 4 Freitas et al., 2008; Alletto, 2013; Eurostat,2007; PPDB, 2006

Methods for tracking biotransformation processes

Enantiomeric signature Carbon CSIA

Novel method to analyse CSIA for S-metolachlor

R S 퐶13 푅 = 퐶12

Potential biotransformation signature

? ? %R Preferential for enantiomer S ? ? ? 훿13퐶 Preferential for 12C substrate

5 Buser, 2000; Thullner, 2012 Objectives

• Evaluate the transport of S-metolachlor at the catchment scale

• Investigate the partitioning between the dissolved and sorbed phases

• Test both approaches to track in situ biotransformation at the catchment scale

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6

6 Source: AERM, 2012 Study site

UK N ALTECKENDORF

Catchment outlet FRANCE

SPAIN

Alteckendorf catchment (Alsace, France) 350 m 48 ha Slope: 5 % Corn: 68% Rainfallyearly: 646 mm Sugar beet: 4%

Wheat, oatg: 18% Orchard, grass strip: 8% Roads, tracks: 2%

Vegetal barrier 7 Study site

UK N ALTECKENDORF

Catchment outlet FRANCE

Plot outlet

SPAIN

Alteckendorf catchment (Alsace, France) 350 m 48 ha Slope: 5% • Sugar beet growing season

Rainfallyearly: 646 mm • S-metolachlor Pre-emergence herbicide A representative plot 77 m² • 2 measurements points: Slope: 5% Outlet of the catchment and the plot

March 27 2012 20 weeks August 14 20128 8 Sampling strategy

N

Catchment outlet

Plot outlet Catchment’s outlet Flow proportional sampling (115 mL every 10 m3)

350 m

Plot’s outlet Total suspended solids quantification Flow proportional sampling by filtration (0.7 µm) (350 mL every 7 L) 9

S-metolachlor analysis

Runoff water samples

Suspended solids Dissolved phase (> 0.7 µm) (< 0.7 µm) Extraction with acetonitrile Solid phase extracted and pure water Recovery rate: 96% Recovery rate: 69%

GC-MS/MS Uncertainty: 17% S-metolachlor Enantiomeric Carbon isotopic -1 LOQ: 0.01 µg kg concentration signatures ratio GC-MS/MS GC-MS/MS chiral GC-C-IRMS Uncertainty: 8% Uncertainty: 1% Uncertainty: 0.5‰ LOQ: 0.04 µg L-1 Impact of rainfall pattern

88 rainfall events: 316 mm Rainfall

0

30 [mm]

3 9 runoff events > 10 m 60 25 700

600

April 10 20

]

500 [t]

3

m Total mass exported: 581 t

3 15 2

(i.e. 1006 t km , 0.7 mm) 400 loads

[10 SS SS

300 10 Water volume SS load 200 Cumulated SS load

Water volume Water 5 100

Applications • One single event 0explains 53% of the total outflow, 92% of the total SS exported0 11 May 22 S-metolachlor off-site and partitioning

• Concentrations reached 62 µg L-1(<0.7 µm) and 34 mg kg-1 (>0.7 µm) • Total export of 368 g, i.e 3.4% exported

1000 46% 100 54% (>0.7 µm) (<0.7 µm) Particulate phase (>0.7 µm)

[g] 10

Dissolved phase (<0.7 µm) loads 1

0.1 Exported

0.01

0.001 • Nearly 50% of the total loads were in the particulate phase • 96% of the total loads corresponded to the event of May 22 12 Enantiomers enrichment: result of stereoselective biotransformation

• EE [%] ranged between -54% and -77% 푅 −푆 퐸푛푎푛푡푖표푚푒푟푖푐 푒푥푐푒푠푠 = . 100

• Similar export coefficient for R- and S-metolachlor 푆+푅 Application [kg]

-50 0

] -55 5 catchment plot Application

-60 10

excess [% excess

-65 15

-70 20 Enantiomeric -75 25

-80 30

13 Carbon isotope fractionation

푅푠푎푚푝푙푒 − 푅푠푡푑 훿13퐶 ‰ =

푅푠푡푑 Application [kg] -28.5 0

-29.0 plot 5 -29.5 Catchment -30.0 13

10 % C

ratio [‰] ratio

application -30.5

-31.0 15 isotopic -31.5 20

-32.0

Carbon -32.5 25 -33.0

-33.5 30

14 Carbon isotopic Vs enantiomeric signatures

Log concentration [log µg L-1] -1 -0.5 0 0.5 1 1.5 2 -69 -28.5

-70 -29.0

-71

-29.5

-72 ‰] -30.0

-73 ratio [ ratio

-30.5 excess [%] excess -74

Enantiomeric excess [%] -31.0 isotopic

-75 Carbon isotopic ratio [‰] -31.5

-76 Carbon Enantiomeric -32.0 -77

-78 -32.5 • Fast flood events • Different-79 commercial products (Dual gold, Camix, Mercantor gold) -33.0 • Evidence of degradation at low concentrations 15 Milosevic, 2013 Summary

• One single event represents the majority of the pesticides and suspended solids export

• The partitioning between dissolved and sorbed phase was nearly 50%/50%

• For the first time, a combination of in situ analysis of chirality and CSIA was tested in runoff water at the catchment scale to highlight in situ biodegradation.

• First step toward the application of chirality and CSIA to evaluate the transport and attenuation of S-metolachlor at the catchment scale.

Perspectives:

- To which extent biotransformation occurred ? - Is enantioselective degradation reflected in soil and suspended solids ?

16 http://lhyges.u-strasbg.fr/

Research group: « Wetland biogeochemistry [email protected] and contaminant transfer» (CNRS-UMR7517) Scientists Gwenaël Imfeld Thank you for Sylvain Payraudeau

Engineers – technicians Benoît Guyot your attention Eric Pernin Cyrielle Regazzoni LHYGES PhD students Marie-Claire Pierret Izabella Babcsányi Omniea Elsayed Atmospheric Physical Marie Lefrancq Chemistry Department Elodie Maillard (LMSPC - UMR 7515), Students Strasbourg. Maxime Combes Maurice Millet Thomas Dreidemy Tristan Meyer IHF (Freiburg) Angela Mutschler Jens Lange Matthieu Schwob Brian Sweeney Diogo Reis

EC2CO Écosphère Continentale et Côtière 17 CYTRIX

Hydrological conditions

18 Hydrochemical conditions

19 Focus on the event of May 22 2012

• T ≈ 40 year return period • 20% rainfall, 53% total outflow 8:54 pm • 92% of suspended solids exported 3 2

8:52 pm

] 1 0

200.000 8:48 pm [mm

2 8:43pm 3 4

150.000

Rainfall 6

[cm]

8 2 100.000

10 height

12 rainfall 50.000 14 1 Water Plot outflow Drain 16 US 0.000

What is the contribution of this large event for pesticides export ? 20 Integrative approach at the catchment outlet

• Principal Component Analysis: 15 variables, 31 objects NO3 Smeto TSS EE

Temp

OM O2 Redox PO4

Conduct DOC pH NH4 NO2 DIC

• Hydrochemical conditions differed during May 22 • Samples before and after May 22 clustered together 21 Extraction and analysis procedure

• SOLID PHASE EXTRACTION (SPE)

10ml Extracted and concentrated sample

Add 2ml of DCM into GC Water samples from vial the columns 1. RINSING (MeoH, EA, DCM) 2. CONDITIONING (MeoH) 3. LOADING 4. WASHING & DRYING 5. ELUTION (DCM & EA) 6. CONCENTRATION

Program: Initial temperature 50°C (held for 2min), 30°C min-1 to • GAS CROMATOGRAPHY (GC-MS/MS) 150°C, 5°C min-1 to 250°C and finally 30°C min-1 to 300°C held for 5min. Inlet temperature is 280°C.

190 µl of sample

+ RESULTS GC vial

with insert 10 µl of internal standards Metolachlor D6 and Alachlor D13 2222 Chloroacetamides extraction

conditionning Sample loading washing & drying elution

solvent Sorbent & Flow rate & Flow rate solvent

Washing: 5 mL EA + 5 mL DCM Conditionning: 10 mL Drying under meOH + 10 mL pure water ≃1 L at 10 mL/min Elution: nitrogen flux 3 mL EA 2 mL DCM Evaporation under nitrogen flux and dissolution in 1 or 2 mL DCM

2323 Enantiomeric analysis

S S R R

2424 GC-C-IRMS compound specific isotope analysis

Elsner, 2012

Carbon isotopic composition reported as difference in CO2 isotope ratio relative to an international standard (VPDB) in 13C [‰] unit.

25 GC-C-IRMS: Method validation

δ13C [‰] values vs Vienna Pee Dee Belemnite (VPDB)

EA- IRMS GC-C-IRMS GC-C-IRMS Compound (standards) (standards) (extracted)

acetochlor -29.8 ± 0.21 -29.5 ± 0.34 -30.1 ± 0.16

alachlor -33.8 ± 0.05 -33.9 ± 0.19 -33.9 ± 0.33

metolachlor -30.2 ± 0.06 -31.0 ± 0.22 -30.7 ± 0.26

 No significant difference between EA-IRMS and GC-C-IRMS  Solid phase extraction method causes no significant fractionation  Signal is linear within the measurement range

EA-IRMS: Elemental Analysis - Isotope Ratio Mass Spectrometry GC-C-IRMS: Gas chromatography combustion isotope ratio mass spectrometry 26 Enantiomers enrichment: result of stereoselective biotransformation

• Enantiomeric Excess (EE) ranged between -0.02 and 0.77 푆 − 푅 퐸퐸 = • Export coefficient similar 푆 + 푅

• Enantiomeric shift before large application and in November • Short sampling period 27

Hydrology and erosion

0 Rainfall

30 [mm]

Mean runoff coefficient: 6% (0.03 – 57) 60 25000 700000

4.36 g L-1 (0.02 – 24.72) 600000

20000

] 500000

3

Total mass exported: 581 t [kg]

Water volume 15000

400000 SS load loads

Cumulated SS load SS SS 300000 10000

Water volume [m volume Water 200000

5000 100000

0 0 2828 Herbicides

In water (< 0.7 µm): Number of samples S-metolachlor Acetochlor (n) [%] (µg L-1) [%] (µg L-1) Detection frequency Plot 10 100% (64.1) 40% ( 1.8) (Maximal concentration) Catchment 33 60% (62.1) 45% (59.3)

0 Rainfall

30

[mm]

7010 60

9 60

8

50 ]

] 7

1

1

- -

6 S metolachlor (catchment) 40 S metolachlor (catchment) 5 acetochloracetochlor (catchment)(catchment) 30 SS metolachlormetolachlor (plot)(plot) 4

acetochloracetochlor (plot)(plot)

Concentration [µg L Concentration [µg L 203 Application 2 10 • Decreasing concentrations at the plot scale 1 • Export: 198 g (S-metolachlor) and 347 g (acetochlor) 0 0 • >90% explained by 22, May. • 29 Export rate ? 29