Using isotope techniques to track terrestrial sediments from soil sources to freshwater systems

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1 Using isotope techniques to track terrestrial sediments from soil sources to freshwater systems Christine Alewell Environmental Geosciences, University of Basel, Switzerland JRC, ISPRA

Soil stability Sediment input to freshwaters Off site damage of erosion

2 This talk is on how to assess with isotope techniques Soil erosion On site effects of erosion Soil fertility and productivity biodiversity carbon storage Soil stability Sediment input to freshwaters Off site damage of erosion Freshwater deterioration Eutrophication (P, N) Clogging of river beds Impact to infrastructure

3 Contents Tracking erosion on site with stable isotopes Quantifying erosion on-site with radionuclides Off site sediment tracking with CSSI markers

6 12 CO 2 δ 13 C Humus > δ 13 C Vegetation 12 CO 2 δ 13 C

4 Tracking erosion on site with stable isotopes C3 - plants δ 13 C Vegetation ~ ± 0.9 (range -22 bis 32 ) CO 2 δ 13 C Humus > δ 13 C Vegetation 12 CO 2 δ 13 C Min.Soil > δ 13 C Humus Photos: Marco Walser, WSL

5 Isotope depth profiles in undisturbed soils: -30 δ13c depth (cm) % C 60 %C δ 13 C Veg = ± 0.9 δ13c vegetation signal δ 13 C % carbon in soil

6 Two Swiss Alpine Sites Lake Soyang Watershed, Korea Punch Bowl Watershed

7 Stable Isotopes as indicators of erosion: Lake Soyang watershed Carbon content vs. δ13c for reference sites and erosion transects Meusburger et al., 2013 Biogeosciences 10

8 Stable isotopes as qualitative indicators of soil disturbance Validation of reference sites for quantification with FRN? Quantification of on-site erosion? Assessment of 137 Cs and Pu as soil erosion tracer in alpine grasslands

9 Quantification of Soil Erosion with Fallout radionuclides (FRN) 1950ties and 1960ties One decade of FRN wet deposition

one sampling campaign required both erosion and deposition Limitations: choice of reliable

10 Quantification of Soil Erosion with Fallout radionuclides (FRN) reference site erosion: depletion in 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 sedimentation: increase in FRN Most commonly used FRN: 137 Cs

11 Complicating life in Europe: 137 Cs fallout by Chernobyl Cs-137 deposition by a few single rain events

12 Pitfalls of Cesium in Europe Huge spatial heterogeneity of reference sites Ursern Valley (Uri) Val Piora (Ticino) (Bq. kg -1 ) n=6 n=6 n=9 n=7, without 2 outliers Mean Stdev CV (%) Konz et al. (2010) Polek (2011) (Juretzko, 2011) Input from Chernobyl in April 1986 Overall disturbance of alpine slopes? Check with stable isotopes

13 Suitability of Pu versus 137 Cs Cs-137 Pu Cs-137 Pu Cs-Inventory [Bq m -2 ] Reference sites Ursern Valley Pu-Inventory [Bq m -2 ] Cs-Inventory [Bq m -2 ] Reference site Piora Valley Pu-Inventory [Bq m -2 ] Urseren Piora n Cs (Bq m -2 ) mean CV (%) Pu (Bq m -2 ) Mean CV (%) Alewell et al., 2014, Chemosphere

14 Advantages: Fallout is continuous over time Long term (100 years) Disadvantages: No direct measurement! And then there is 210 Pb ex high uncertainty related to determination 210 Pb ex especially if total 210 Pb is close to supported 210 Pb Quite often below detection limit Mabit et al., 2014

15 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 Pu versus 137 Cs (difference in conversion models, difference in diffusion and migration coefficients) No comparability to 210 Pb ex

16 Multi-Isotope Approaches Determine origin of FRN 240 Pu/ 239 Pu ( 238 Pu/ 239 Pu and 241 Pu/ 239 Pu with limitations): nuclear weapon production vs weapon fallout vs accidental and routine releases from nuclear installations 137 Cs/ Pu or 134 Cs/ 137 Cs: 137 Cs input from Chernobyl Assessment of particle size correction factor preferential transport of 137 Cs compared to Pu (Meusburger et al., 2016 STOTEN)

17 Advantages of Pu 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 137 Cs or 210 Pb ex main isotopes ( 239 Pu and 240 Pu) have long half-lives of and years: advantage in terms of its long term use seems to be a much more reliable soil redistribution tracer compared to 210 Pb ex Medium to short term soil erosion rates might be assessed via resampling techniques (e.g., Porto et al., 2014) New conversion model MODERN available, to convert Pu inventory changes into soil redistribution rates

18 Significance of erosion rates in our alpine catchment? Soil degradation t ha 2 yr -1 mm yr -1 Specifications Konz et al. (2010) 30* Cs measurements; hot spots Alewell et al. (2014) 14* Pu measurements; hot spots Meusburger et al. (2010) 16* 1.2* 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 ky * old surfaces 1-10 ky * younger surfaces 0-1 ky * Very young or strongly eroded sites >> 1 t ha -2 yr -1 Non sustainable soil use: degradation of soils Problem will most likely increase in the future (climate change, land use change) Conversions from t km 2 yr -1 to mm yr -1 with soil bulk densities of 1 t m -3 (surface horizon) Alewell, Egli, Meusburger, 2014; JSS

19 Arable field Forest Pasture Sediment/ Organic matter Source Attribution

20 Concept Catchment source areas d 13 C Soil Catchment erosion d 13 C %? %? %?

$fraction Bulk δ 13 C, δ 15$

21 Dry weight, %C, %N Soil/Sediment Sample Extraction Total lipid extract Separation Acid fraction Bulk δ 13 C, δ 15 N GC-MS GC-FID Fatty acid methyl esters (FAME) GC-IRMS

22 Catchment Enziwigger

23 Methods and Implementation Suspended Sediment sampler sediment basket Sampling fall and winter 2009/2010 and 2010/2011 SchindlerWildhaber et al., HESS 2012

24 ...all to often......not only... Sampling fall and winter 2009/2010 and 2010/2011

25 Sediment source attribution with CSSI Alewell, Birkholz, Meusburger et al., 2016 δ 13 C 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.

26 Sediment source attribution to the Enziwigger % sediment contribution from 2 Tracers/3 Sources (IsoSource) Site Event Forest Agriculture %Forest % Pasture % Arable A BF A HF A HF B BF * 16.6* 55.2* B HF B HF C BF C HF C HF Contribution of the different sediment source areas to the SS for two or three sources. BF = base-flow event, HF = high-flow event.

27 Conclusions Stable isotopes can be used to qualitatively track soil erosion onsite and validate reference sites for FRN based erosion assessment Quantification of soil erosion assessment with FRN: Pu seems more reliable than 137 Cs in Europe due to Chernobyl input and generally more reliable than 210 Pb ex Measurement of FRN: Analytical advantages of Pu (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

28 Thank you for your attention! Laura Arata Katrin Axel Meusburger Birkholz Markus Zehringer Kantonslabor, Basel Lionel Mabit Now at IAEA, Vienna Ji-Hyung Park Ewha Womans University, South Korea Mike Ketterer University of Denver Yael Schindler Now at FOEN, Switzerland Funding: Swiss National Science Foundation Swiss Federal Office of the Environment IAEA, Vienna

29 Discussion

30 Isotopes as indicators of soil degradation in the Swiss Alps Upland soils with no visible erosion r > Soils prone to erosion r Schaub and Alewell, 2009, Rap Comm Mass Spec 23

31 Validating disturbance of reference sites with stable isotopes Val Piora (Ticino) (Bq. kg -1 ) n=9 without 2 outliers Ursern Valley (Uri) n=6 n=6 Mean Stdev CV (%) (Juretzko, 2011) Polek (2011) Konz et al. (2010) Brun, 2012

32 Conversion: MOdelling Deposition and Erosion rates with RadioNuclides (MODERN) The MODERN code is available at modern.umweltgeo.unibas.ch 32 Arata et al., 2016 a, b; J. Environ. Radioact.

33 Results of MODERN 137 Cs based estimates 137 Cs based estimates 137 Cs =>transition of land use not considered yet Pu MODERN (t ha -1 yr -1 ) IM (t ha -1 yr -1 ) y = 0.92x R² = Pu based estimates y = 2.02x R² = 0.90 uncultivated PDM (t ha -1 yr -1 ) uncultivated MODERN (t ha -1 yr -1 ) MODERN (t ha -1 yr -1 ) IM (t ha -1 yr -1 ) y = 0.81x R² = y = 1.17x R² = 0.65 MBM2 (t ha -1 yr -1 ) Pu based estimates MODERN (t ha -1 yr -1 ) cultivated cultivated PDM: Profile distribution model; MBM2: Mass balance model 2 (Walling et al., 2002, 2014); IM: Inventory model (Lal et al., 2013) 33 Meusburger et al., 2016; STOTEN

34 Sediment source attribution with CSSI Alewell, Birkholz, Meusburger et al., submitted 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

35 Sediment source attribution with CSSI Alewell, Birkholz, Meusburger et al., submitted 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.

36 Quantitative sediment source attribution A system with n tracers is solvable for n+1 sources because you have n+1 equations: f A + f B + f C = 1 δ 15 N f=fraction δ 13 C Pasture Forest Arable Suspended Sediments 1111 NN ssssssssssssssssss = ffff 1111 NN ssssssssssssss + ffff 1111 NN ssssssssssssss + ffff 1111 NN ssssssssssssss 1133 CC ssssssssssssssssss = ffff 1133 CC ssssssssssssss + ffff 1133 CC ssssssssssssss + ffff 1133 CC ssssssssssssss 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)) 36

37 Comparison to other studies Swiss Alpine sites t km 2 yr -1 mm yr -1 Konz et al. (2010) Alewell et al. (2014) 3000* 1400* Cs based; hot spots Pu based; hot spots Meusburger et al. (2010) 1600* 118* sheet erosion modelled hot spots sheet erosion modelled average Meusburger and Alewell (2009) 60* Landslides, measurements Meusburger et al. (2009, 2010) 178* Average sum Literature data Dosseto et al. (2011) # lower range for Alps # higher range for Alps Felix and Johannes (1995) 440* 0.44 calcareous Alps, Bavaria Frankenberg et al. (1995) 3000* 3 # Flysch, Molasse, Allgäuer Alps Ammer et al. (1995) * Flysch, calcareous Alps Descroix et al. (2003) * French Alps Isselin-Nondedeu and Bedecarats (2007) # heavy rain events, French Alps * # gives the original published number which was converted (t km -2 yr -1 versus mm yr -1 ).

38 137 Cs repeated sampling approach Classical 137 Cs method Spatial reference Years = Sites instead Temporal reference: Compare 2007 Cesium measurements with 2012 Re-sampling approach Years Sites =

LI Yong (1,2), FRIELINGHAUS Monika (1), BORK Hans-Rudolf (1), WU Shuxia (2), ZHU Yongyi (2)

LI Yong (1,2), FRIELINGHAUS Monika (1), BORK Hans-Rudolf (1), WU Shuxia (2), ZHU Yongyi (2) Scientific registration n : Symposium n : 31 Presentation : poster Spatial patterns of soil redistribution and sediment delivery in hilly landscapes of the Loess Plateau Motifs spaciaux de zones d'érosion