Using isotope techniques to track terrestrial sediments from soil sources

to freshwater systems

Christine AlewellEnvironmental Geosciences, University of Basel, Switzerland

21.3.2017 JRC, ISPRA

This talk is on how to assess……

Soil erosion Sediment input to freshwaters

On site effects of erosionSoil fertility and productivitybiodiversitycarbon storageSoil stability

Off site damage of erosionFreshwater deteriorationEutrophication (P, N)Clogging of river bedsImpact to infrastructure

with isotope techniques

Contents

Tracking erosion on site with stable isotopes

Quantifying erosion on-site with radionuclides

Off site sediment tracking with CSSI markers

C3 - plants

δ13CVegetation ~ - 28.6 ± 0.9 ‰(range -22 bis – 32 ‰)

δ13CHumus > δ13CVegetation

δ13CMin.Soil > δ13CHumus

12CO2

12CO2

- 28.6 ‰

- 23.0 ‰

Photos: Marco Walser, WSL

Tracking erosion on site with stable isotopes

0δ13C

dept

h (c

m)

60

-30 -20

Isotope depth profiles in undisturbed soils:

vegetation signal

δ13CVeg = -28.6 ± 0.9 ‰

δ13C % carbon in soil

%C δ13C %

C

Two Swiss Alpine Sites

Lake Soyang Watershed, Korea

Punch Bowl Watershed

Stable Isotopes as indicators of erosion: Lake Soyang watershed

Carbon content vs. δ13C for reference sites and erosion transectsMeusburger et al., 2013 Biogeosciences 10

? Quantification of on-site erosion?

Assessment of 137Cs and 239+240Pu as soil erosion tracer in alpine grasslands

Stable isotopes as qualitative indicators of soil disturbance

Validation of reference sites for quantification with FRN

One decade of FRN wet deposition1950ties and 1960ties

Quantification of Soil Erosion with Fallout radionuclides (FRN)

erosion:depletion in FRN

sedimentation:increase in

FRN

reference site

Quantification of Soil Erosion with Fallout radionuclides (FRN)

Advantages:• global distribution• retrospective assessment• spatially distributed data• only one sampling campaign

required • both erosion and deposition

Limitations:• choice of reliable reference

sites• specific detection systems

Most commonly used FRN: 137Cs

26.4.1986Cs-137 deposition

by a few single rain events

Complicating life in Europe: 137Cs fallout by Chernobyl

Pitfalls of Cesium in EuropeHuge spatial heterogeneity of “reference” sites

Input from Chernobyl in April 1986Overall disturbance of

alpine slopes?

Check with stable isotopes

Ursern Valley (Uri) Val Piora (Ticino)(Bq.kg-1) n=6 n=6 n=9 n=7, without 2

outliersMean 131 106 420 142Stdev 17 43 475 24CV (%) 10 40 110 20

Konz et al. (2010)

Polek (2011) (Juretzko, 2011)

Suitability of 239+240Pu versus 137Cs

0

20

40

60

80

100

120

140

160

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

1 2 3 4 5 6

Pu-In

vent

ory

[Bq

m-2

]

Cs-In

vent

ory

[Bq

m-2

]

Reference sites Ursern Valley

Cs-137 Pu-239+240

0

20

40

60

80

100

120

0

5000

10000

15000

20000

25000

30000

1 2 3 5 6 7 9

Pu-In

vent

ory

[Bq

m-2

]

Cs-In

vent

ory

[Bq

m-2

]

Reference site Piora Valley

Cs-137 Pu-239+240

Alewell et al., 2014, Chemosphere

Urseren Pioran 6 7

137Cs (Bq m-2) mean 6892 10355CV (%) 32 98

239+240Pu (Bq m-2) Mean 83 77CV (%) 13 17

And then there is 210Pbex

Mabit et al., 2014

Advantages: Fallout is continuous over time Long term (100 years)

Disadvantages: No direct measurement! high uncertainty related to

determination 210Pbex especially if total 210Pb is close to supported 210Pb

Quite often below detection limit

Multi-Radionuclide Approaches Validation of FRN against each other (South Korea, no Chernobyl input and prior to Fukushima, Meusburger et al., 2016 STOTEN):

Same order of magnitude for 239+240Pu versus 137Cs (difference in conversionmodels, difference in diffusion and migration coefficients)

No comparability to 210Pbex

Multi-Isotope Approaches

Determine origin of FRN 240Pu/239Pu (238Pu/239Pu and 241Pu/239Pu with limitations): nuclear weapon production vs weapon fallout vs accidental and routine releases from nuclear installations 137Cs/239+240Pu or 134Cs/ 137Cs: 137Cs input from Chernobyl

Assessment of particle size correction factor preferential transport of 137Cs compared to 239+240Pu

(Meusburger et al., 2016 STOTEN)

Advantages of 239+240Pu as soil erosion tracer not influenced by nuclear accident fallout (with the exception of regions

with close proximity to accident sites): relatively low heterogeneity of reference sites

analytical advantage of lower cost and higher sample throughput either with ICP-MS or alpha spectrometry compared to both 137Cs or 210Pbex

main isotopes (239Pu and 240Pu) have long half-lives of 24’110 and 6’561 years: advantage in terms of its long term use

seems to be a much more reliable soil redistribution tracer compared to 210Pbex

Medium to short term soil erosion rates might be assessed via re-sampling techniques (e.g., Porto et al., 2014)

New conversion model MODERN available, to convert Pu inventory changes into soil redistribution rates

t ha2 yr-1 mm yr-1 Specifications Soil degradation

Konz et al. (2010) Alewell et al. (2014)

30* 14*

3 1.4

137Cs measurements; hot spots 239+240Pu measurements; hot spots

Meusburger et al. (2010) 16* 1.2*

1.6 0.12

sheet erosion modelled hot spots sheet erosion modelled average

Meusburger and Alewell (2009) 0.60* 0.06 Landslides, measurements

Meusburger et al. (2009, 2010) 1.8* 0.18 Average sum erosion +land slides Geomorphological rate of Alpine soil formation depending on age

10 - 18 ky 0.3-0.6* 0.03-0.06 old surfaces

1 - 10 ky 0.6-3.5* 0.06-0.35 younger surfaces

0 - 1 ky 3.5-20* 0.35-2.0 Very young or strongly eroded sites

Significance of erosion rates in our alpine catchment?

Conversions from t km2 yr-1 to mm yr-1 with soil bulk densities of 1 t m-3 (surface horizon)Alewell, Egli, Meusburger, 2014; JSS

>> 1 t ha-2yr-1 Non sustainable soil use: degradation of soils Problem will most likely increase in the future (climate change, land use change)

Sediment/ Organic matter Source Attribution

Forest

Pasture

Arable field

d13C

d13C %?

%?

%?Catchmenterosion

Soil

Catchment source areas

Concept

Soil/SedimentSample

Dry weight, %C, %N

Bulk δ13C, δ15N

Extraction Total lipid extract Separation Acid fraction

Fatty acid methyl esters

(FAME)

GC-MS

GC-FID

GC-IRMS

Catchment Enziwigger

Methods and Implementation

sediment basket

Suspended Sediment sampler

Sampling fall and winter 2009/2010 and 2010/2011

SchindlerWildhaber et al., HESS 2012

...all to often..... ...not only.....

Sampling fall and winter 2009/2010 and 2010/2011

Sediment source attribution with CSSI

Ale

wel

l, B

irkho

lz, M

eusb

urge

r et a

l., 2

016

δ13C of FAs C26:0 versus C28:0 of sediment sources and suspended sediments (SS) at the three sites (A, B and C) in the Enziwigger catchment.

Sediment source attribution to the Enziwigger

Contribution of the different sediment source areas to the SS for two or three sources. BF = base-flow event, HF = high-flow event.

% sediment contribution from 2 Tracers/3 Sources (IsoSource)Site Event Forest Agriculture %Forest % Pasture % Arable A BF 70 30A HF 2010 85 15A HF 2009 60 40B BF 37 63 28.2* 16.6* 55.2*B HF 2010 94 7 92.1 2.4 5.5B HF 2009 78 22 69.5 9.4 21.1C BF 34 66 31.8 23.6 44.6C HF 2010 72 29 64.7 12.3 23.0C HF 2009 55 45 49.2 17.7 33.1

Conclusions

Stable isotopes can be used to qualitatively track soil erosion on-site and validate reference sites for FRN based erosion assessment

Quantification of soil erosion assessment with FRN:239+240Pu seems more reliable than 137Cs in Europe due to Chernobyl input and generally more reliable than 210Pbex

Measurement of FRN: Analytical advantages of 239+240Pu (ICP-MS)

Off site tracking with CSSI: high effort in analytical devices, investment and lab staff, but strong tool to track down sources of sediments: plenty more to explore

Thank you for your attention!

KatrinMeusburger

Lionel MabitNow at IAEA, Vienna Mike Ketterer

University of Denver

Ji-Hyung ParkEwha Womans University,

South Korea

Axel Birkholz

Yael Schindler Now at FOEN, Switzerland

Laura Arata

Markus ZehringerKantonslabor, Basel

Funding:Swiss National Science FoundationSwiss Federal Office of the EnvironmentIAEA, Vienna

Discussion

Isotopes as indicators of soil degradation in the Swiss Alps

Upland soils with no visible erosion

r > |-0.85 |

Soils prone to erosion r ≤ |-0.80|

Schaub and Alewell, 2009, Rap Comm Mass Spec 23

Val Piora (Ticino) Ursern Valley (Uri)(Bq.kg-1) n=9 without 2

outliersn=6 n=6

Mean 420 142 106 131Stdev 475 24 43 17CV (%) 110 20 40 10

(Juretzko, 2011) Polek (2011) Konz et al. (2010)

Validating disturbance of reference sites with stable isotopes

Brun, 2012

Conversion: MOdelling Deposition and Erosion rates with RadioNuclides (MODERN)

32

The MODERN code is available atmodern.umweltgeo.unibas.ch

Arata et al., 2016 a, b; J. Environ. Radioact.

Results of MODERN

33

y = 2.02x - 0.78R² = 0.90

-40

-30

-20

-10

0

10

20

30

-20 -10 0 10 20

IM (t

ha-

1yr

-1)

MODERN (t ha-1 yr-1)

239+240Pu based estimates

y = 0.92x - 0.16R² = 0.99

-8-6-4-202468

10

-10 -5 0 5 10 15

MO

DER

N (t

ha-

1 yr

-1)

PDM (t ha-1 yr-1)

137Cs based estimates

y = 0.81x - 3.97R² = 0.63

-60

-40

-20

0

20

40

-60 -40 -20 0 20 40

MO

DER

N (t

ha-

1 yr

-1)

MBM2 (t ha-1 yr-1)

137Cs based estimates

y = 1.17x - 0.25R² = 0.65

-50

-40

-30

-20

-10

0

10

20

-40 -20 0 20IM

(t h

a-1

yr-1

)MODERN (t ha-1 yr-1)

239+240Pu based estimates

Meusburger et al., 2016; STOTEN

137Cs

239+240Pu

PDM: Profile distribution model; MBM2: Mass balance model 2 (Walling et al., 2002, 2014); IM: Inventory model (Lal et al., 2013)

=>transition of land use not considered yet

uncultivated cultivated

uncultivated cultivated

Sediment source attribution with CSSI

Alew

ell,

Birk

holz

, Meu

sbur

ger e

t al.,

sub

mitt

ed

δ13C of the FAs C26:0 and C28:0 at site A: Considering measurement un-precision, δ13C were corrected to the mixing line with linear regression

Sediment source attribution with CSSI

Ale

wel

l, B

irkho

lz, M

eusb

urge

r et a

l., su

bmitt

ed

δ13C isotopic signatures of FAs C26:0 versus C14:0 of sediment sources and suspended sediments (SS) at the three sites in the Enziwigger catchment.

Quantitative sediment source attribution

A system with n tracers is solvable for n+1 sources because you have n+1 equations:

fA + fB + fC = 1 f=fraction

𝝏𝝏𝟏𝟏𝟏𝟏𝑵𝑵𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔 = 𝒇𝒇𝒇𝒇 𝝏𝝏𝟏𝟏𝟏𝟏𝑵𝑵𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒇𝒇 + 𝒇𝒇𝒇𝒇 𝝏𝝏𝟏𝟏𝟏𝟏𝑵𝑵𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒇𝒇 + 𝒇𝒇𝒇𝒇 𝝏𝝏𝟏𝟏𝟏𝟏𝑵𝑵𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒇𝒇

𝝏𝝏𝟏𝟏𝟑𝟑𝒇𝒇𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔 = 𝒇𝒇𝒇𝒇 𝝏𝝏𝟏𝟏𝟑𝟑𝒇𝒇𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒇𝒇 + 𝒇𝒇𝒇𝒇 𝝏𝝏𝟏𝟏𝟑𝟑𝒇𝒇𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒇𝒇 + 𝒇𝒇𝒇𝒇 𝝏𝝏𝟏𝟏𝟑𝟑𝒇𝒇𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒔𝒇𝒇

If sources > n+1: mixing model approaches, calculation of all possible solutions within a range of specified uncertainty(e.g. model ISOSOURCE by Phillips and Gregg (2001))

-3-2.5

-2-1.5

-1-0.5

00.5

11.5

2

-36 -31 -26 -21 -16

δ15 N

δ13C

PastureForestArableSuspended Sediments

36

Swiss Alpine sites t km2 yr-1 mm yr-1

Konz et al. (2010)Alewell et al. (2014)

3000*1400*

31.4

137Cs based; hot spots239+240Pu based; hot spots

Meusburger et al. (2010) 1600*118*

1.60.118

sheet erosion modelled hot spotssheet erosion modelled average

Meusburger and Alewell (2009) 60* 0.060 Landslides, measurements Meusburger et al. (2009, 2010) 178* 0.178 Average sum

Literature dataDosseto et al. (2011) 400 0.400# lower range for Alps

20000 20# higher range for AlpsFelix and Johannes (1995) 440* 0.44 calcareous Alps, BavariaFrankenberg et al. (1995) 3000* 3# Flysch, Molasse, Allgäuer AlpsAmmer et al. (1995) 200 - 900* 0.2 - 0.9 Flysch, calcareous AlpsDescroix et al. (2003) 1400 -3300* 1.4 - 3.3 French AlpsIsselin-Nondedeu and Bedecarats (2007)

6000 - 18000 6 - 18# heavy rain events, French Alps

Comparison to other studies

*# gives the original published number which was converted (t km-2 yr-1 versus mm yr-1).

137Cs repeated sampling approach

Spatial reference

instead

Temporal reference:

Compare 2007 Cesium measurements with 2012

Re-sampling approach

Years ≠Sites =

Years =Sites ≠

Classical137Cs method