Sediment source fingerprinting by Compound Specific Isotope Analysis (CSIA)

P. Hirave; M. Lavrieux; K. Meusburger;

A. Birkholz C. Alewell

 

 

Sediment loads in rivers are increasing worldwide, often being related to anthropogenic activities. These fine sediment loads entering into freshwater systems may cause serious impairments to the aquatic environments, including increased turbidity, eutrophication and ecosystems degradation.

Thus, for the management of freshwater quality, it is crucial not only to know the amount of sediments, but even more their source areas. A promising approach to track sediment source areas is the sediment fingerprinting, which relies upon the identification of sediment sources based on the differences in source material properties and the quantification of the relative contributions from these sources to the sediment. The challenge is to find soil properties/tracers that differ with land use. In this context carbon stable isotopic signatures of specific organic tracers (biomarkers) are promising. Currently, we have two projects dealing with the exploitation of the compound specific isotope analysis (CSIA) for sediment fingerprinting.

The first study catchment includes 2 tributaries of the Upper Sûre Lake, a drinking water reservoir located in Luxembourg. The main land uses are deciduous and coniferous forests, agricultural fields with a wide variety of crops and pastures. Plant material including leaves and litter, humus layer in the forests, surface soils and suspended sediments will be analysed. In the frame of this project, we will study the suitability of different biomarkers including long-chain fatty acids and n-alkanes, which are uniquely of plant origin and are considered as resistant to degradation. In addition to the carbon isotopic ratios, chain length characteristics and concentration of the biomarkers will also be considered. The understanding generated by this study should help to expand the application of CSIA to larger river systems with more complex land use patterns.

In the second study we aim to reconstruct main sediment sources to the Baldeggersee (Canton Luzern, Switzerland) over space (catchment scale) and time (back to the 1950ties) with a combination of CSIA and connectivity modelling. Our project is bedded into the main aims of the European COST action ES1306 which will enable us to build on the emerging network on connectivity knowledge. Sediment source areas in the catchment and sediment quantity to specific river sections will be identified with a modified sediment connectivity index. Additionally, sediment origin and quantity will be assessed with CSIA. Variation of sediment origin will be determined via analysis of suspended sediment samples taken at base and high flow conditions (short-term) and analysis of lake sediment core samples (long-term). The expected outcome of the proposed project is the determination of the dynamic of sediment origin over space and time, as a basis for future management options to reduce sediment loading to the Baldeggersee.

To know more about M. Lavrieux's research on Baldeggersee, follow this link.

Quantification of soil redistribution with fallout radionuclides FRN (239-240Pu, 137Cs and excess 210Pb)

 K. Meusburger; L. Arata; C. Alewell; L. Mabit; P. Porto; M. Ketterer; M. Zehringer

 

To efficiently mitigate and control soil losses by erosion suitable methods for comprehensive data generation on the magnitude and spatial extent of soil erosion are needed.

Artificial radionuclides such as 137Cs and 239-240Pu, which originated from thermonuclear weapon tests in the 1950s-1960s and nuclear power plant accidents (i.e. Chernobyl), can be used for this purpose, because they are rapidly and strongly adsorbed to fine soil particles with limited migration and bioavailability. Documenting the subsequent radionuclides redistribution, which move across the landscape in association with soil/sediment particles primarily through physical processes, represents an effective means of tracing rates and patterns of erosion and deposition. In addition, to these artificial radionuclides we also explore the applicability of the natural geogenic radioisotope excess 210-Lead in our alpine study sites.

The fallout radionuclide (FRN) approach possesses important advantages over more conventional means of documenting soil erosion and soil redistribution (such as plots or field mapping), because a single field visit is sufficient to assess the net soil redistribution since the main FRN fallout. Further, FRNs comprise all erosion process and is thus of particular interest in the context of quantification of snow induced erosion.

However, the time-averaging nature from the main period of bomb fallout to the time of sampling can also be considered as limitation of the approach. To meet the requirement of short-term assessment (e.g. several years instead of decades) and monitoring in light of increasing concern for the impact of changing land use and climate we explore the applicability of resampling and repeated sampling techniques (Figure) in the frame of the Coordinated Research Project (CRP) Nuclear Techniques for a Better Understanding of the Impact of Climate Change on Soil Erosion in Upland Agro-ecosystems funded by the International Atomic Energy Agency (IAEA).

On-site quantification of soil erosion with FRN, in combination with the off-site tracking of sediments using fingerprinting techniques complements our soil erosion modelling based assessments and as such enhances our understanding on the spatial and temporal variability of erosion.

 

For a detailed description of L. Arata's research project on the application of radionuclides in Swiss Montanous areas follow this link

-> modern.umweltgeo.unibas.ch

WaTEM-SEDEM modelling of soil erosion and sediment yield

P. Borrelli; K. Meusburger; C. Alewell

Project is funded by the University of Basel

Duration: started September 2016

Collaboration: European commission Joint Research Centre (Ispra)

 

Soils are the largest terrestrial reservoir of organic carbon and nutrients such as nitrogen and phosphorus. They underpin the functioning of all terrestrial ecosystems and are key to improve food security and soil carbon sequestration. In many areas cultivation lead to increased rates of soil degradation through soil erosion. Soil erosion still constitutes one of the major threats to soils in Europe and its spatial prediction still poses a challenge to the soil science community.

Today, the mainstreaming of geospatial technologies like Geographic Information Systems (GIS), satellite imagery and robust spatial interpolation methods are creating an enabling environment to make the necessary quantum leap in modelling both soil loss rates and sediment yield. In the frame of this project we work on methodologies including beyond the state-of-the-art techniques to:

i) integrate spatio-temporal variation of vegetation phenology in soil loss prediction models;

ii) model sediment origin and transport dynamics;

iii) narrow the knowledge gap regarding the lack of thorough approaches to upscale high-resolution input parameters to catchment- and regional-scale.

Soil Erosion Risk Modelling in the Alps – ERKBerg as a Prototype of ERK2 for mountain zones III, IV and summering grazing zones

S. Schmidt; K. Meusburger; C. Alewell

Project funded by the Federal Office for the Environment (FOEN/BAFU)

N° N222-0350

Duration: March 2015 – March 2017

Soil Erosion on grassland is generally neglected due to its protective character of dense grass vegetation on soil loss. However, recent studies by Meusburger et al. (2010), Konz et al. (2012) and Alewell et al. (2013) show that large amounts of topsoil are mobilized also on grassland in the alpine areas.

For flat and gently sloped regions of Switzerland, a soil erosion modelling approach was already realized by the Centre for Development and Environment University Bern and Agroscope Reckenholz (ERKII) which is currently to be upgraded. To complement the ERKII-results and to create a nationwide soil erosion risk map, a risk assessment for the formally excluded mountain zones III, IV and summering grazing zones will be realized by geospatial modelling. 

For a detailed description follow this link

Stable carbon isotopes in soils as indicators of environmental change

 C. Alewell; J. Leifeld; J. P. Krüger

 

 

 

 

 

Peatlands are an important component of the global carbon cycle. Even though they cover only about 3% of the global land area, they store approximately 600 Pg carbon (C) in their soils. More than 50% of the European peatlands have been drained during the last centuries due to intensive agricultural or forestry usage. This degradation changes a peatland from a carbon sink into a carbon source, and results in a major loss of related ecosystems functions such as biodiversity, natural habitat, water cycle regulation, recreational values. While landscape managers have sought to restore peatlands in the recent years, they lack feasible monitoring tools to prove successful restoration. Our major purpose is to develop a set of biogeochemical and modelling tools to assess peatland restoration, including a verification of net carbon storage. A combination of bulk isotope depth profiles, biomarker concentrations, soil chemical characteristics (molecular compound information, ash content, bulk density, C/N ratio, 13C NMR and IR spectroscopy) and radiocarbon data will be used to assess the transformation degree and the net carbon gain or loss of selected peatlands. These sites will be in Finland, Southern Germany and Switzerland, where we already gathered experience and data from the antecedent project “Stable Carbon indicators of soil degeneration” (SNF project no. 200021-137569) and we will benefit from established collaborations on the long-term monitoring sites.


For a detailed description of our J. P. Krüger's research project follow this link

Radon-222 as relevant atmospheric tracer

F. Conen; L. Zimmermann

Project inserted in the frame of the ICOS-CH infrastructure (Integrated Carbon Observation System- the Swiss contribution to a European Research Infrastructure)

Cooperation: ANSTO Atmospheric Mixing  (Australian Nuclear Science and Technology Organisation)

Radon-222 is naturally emitted from land surfaces. The only sink of this noble gas in the atmosphere is radioactive decay. Its half-life of 3.8 days provides for large concentration differences between the planetary boundary layer and free tropospheric air, making it a good tracer for recent land contact of air masses sampled at the high altitude observatory Jungfraujoch. Through this project we provide daily updated radon-222 concentrations for Jungfraujoch (3454 m a.s.l.) and for Bern (575 m a.s.l.), located 60 km to the NW of Jungfraujoch. Earlier results of the project include the characterisation (mapping) of radon-222 flux in Europe, the USA and Russia.

For a detailed description follow this link

-> www.radon.unibas.ch

GHG emissions from peatlands under different land use

S. Paul; C. Alewell; J. Leifeld

Project funded by the Federal Office of the Environment (FOEN/BAFU) 13.0057.KP / M344-1280

Duration: November 2013- December 2016

Collaboration: Agroscope

 

Peatlands serve as important carbon sinks. Globally, more than 30% of the soil organic carbon is stored in organic soils, although they cover only 3% of the land surface. The agricultural use of organic soils usually requires drainage thereby transforming these soils from a net carbon sink into a net source. Currently, about 2 to 3 Gt CO2 are emitted world-wide from degrading organic soils which is ca. 5% of the total anthropogenic emissions. Restoration of degraded peatlands can reduce net greenhouse gas emissions. However, the quantification of the greenhouse gas balance after rewetting is challenging.

The restoration of cultivated peatlands is the major carbon sequestration potential for agricultural soils in Switzerland. Little attention was drawn to the restoration of these former fens – equally degraded bogs – in the context of climate protection. Moreover, measured emission data from peatlands are rare for Switzerland.

The goals of this project are:

i) to improve the emissions factors of organic soils under different land use for climate reporting under UNFCCC;

ii) to evaluate the potential of Wetland Drainage and Rewetting in Switzerland;

iii) to develop climate smart management option for agriculture use of organic soils. Therefore, we measure the carbon balance of a degraded and of a drained fen. In 2017 this fen will be rewetted and we want to track the emission of greenhouse gases induced by the change in land use.

For a detailed description follow this link

Linkage between deposition and air-surface exchange of mercury in forest ecosystems: a comparative study between Switzerland and China

(adapted from: Lubick, N., Malakoff, D., 2013. With Pact’s Completion, the Real Work Begins. Science 341, 1443–1445. doi:10.1126/science.341.6153.1443)

J. H. Huang; S. Osterwalder; C. Alewell; X. Feng

Project funded by SNF N° IZLCZ2_170176 /1, Sino-Swiss Science and Technology Cooperation (SSSTC) 2016.

 

Forest ecosystems in China and Switzerland exhibit distinct Hg deposition trends. While there is continuously increased Hg deposition in China, the deposition rate of Hg has been decreased since 1960s in Switzerland. In this study, we propose a collaborative project to investigate Hg biogeochemical behaviour in the remote forested ecosystems in Switzerland and China to understand how different chronologies of Hg deposition impact Hg biogeochemistry in remote forest ecosystems with a specific focus on atmosphere-land exchange of Hg.

We will characterise the profile distribution of Hg at both sites to reveal at which horizons the recently and historically deposited Hg tends to accumulate. Using isotope dilution technique, we will quantify the pool of exchangeable Hg in soils. We will perform the first ever research to quantify gaseous elemental mercury (Hg(0), GEM) fluxes above and below the forest canopy utilising REA and dynamic flux chamber at both sites, in addition to mass balance analysis of Hg. This approach will complete our understanding on Hg biogeochemical cycles in the terrestrial environments at Chinese and Swiss sites.

Mesocosm systems with litterfall, O layers and subsoils will be carried out to measure Hg reemission and leaching from soils at the Chinese and Swiss sites under manipulated precipitation, temperatures, biological activities and irradiance to examine how environmental factors affect Hg reemission and leaching from litterfall, O layers and subsoils at both sites.

We will also measure Hg isotope compositions of Hg in atmospheric Hg, wet precipitation, litterfall, soils and bedrock at both sites to assess Hg sources along the soil profile to gain more insights into historical changes in deposition sources at both Chinese and Swiss sites. In mesocosm systems, the magnitude and direction of Hg isotope change during incubation will be utilised to identify possible Hg reduction pathways in soils and furthermore to elucidate how the pathway of Hg reduction in litterfall, O layers and subsoils.

The proposed research will deliver quantitative information on the air-land exchange of Hg in forest ecosystems with distinct Hg deposition fluxes at the two study sites. This information is crucial for better understanding of global cycling of Hg in the environment, and has the potential in understanding how effective the implementation of the Minimata Convention will curb the process of recovery from Hg accumulation not only in China but also in Europe and North America.

 

For more details on S. Osterwalder's research on Hg evasion from boreal mires, please follow this link

 

 

 

Influence of human activities on the aquatic environment of Sancha Lake in Sichuan province, China (Chengdu Science and Technology Bureau, China)

J. H. Huang; C. Alewell; L. Tian; B. Jia; Y. Tang

Project funded by Chengdu Science and Technology Bureau and Sichuan Provincial Bureau of Environmental Protection


Duration: July 2009-August 2016

Collaboration:
Prof. Binyang Jia, Chengdu Academy of Environmental Sciences, Chengdu 610072, People’s Republic China
Prof. Ya Tang, College of Architecture and Environment, Sichuan University, Chengdu 610065, People’s Republic China

Sancha Lake in Sichuan Province, Southwest China, is impacted by a serious problem of eutrophication. The major human activity prior to fish farming was terrestrial agriculture onshore and the aquatic environment in the reservoir was oligotrophic until 1985. The aquatic environment of Sancha Lake turned eutrophic dramatically with the introduction of fish farming in 1985 and other industrial activities from 2000 onwards. Although there were several measures by the local government to reduce anthropogenic input drastically for the remediation of Sancha Lake since 2005, the aquatic environment is still eutrophic today.

The large variations of fish farming activities in the history in Sancha Lake allow us quantify the influence of fish farming on the vertical and spatial distribution, speciation and mobility of C, N, P and metals in the lake water and sediments. Global aquaculture production has grown at an average rate of 8.8 % annually since 1980 and is expected to further increase in the future. Therefore, our findings will provide scientific knowledge to improve and restore the reservoir’s ecological environment affected by fish farming.