Search for projects with tag "isotopes"
Rethinking recovery rates from mercury (Hg) pollution by reconciling evasion of legacy Hg pollution from peatlands with historical records of Hg accumulation and isotope signatures in peat profiles
PI: Chuxian Li
Anthropogenic mercury (Hg) emissions to the atmosphere have increased the concentration of this potent neurotoxin in terrestrial and aquatic ecosystems. Efforts to control this pollution have reduced atmospheric concentrations of gaseous elemental mercury (GEM) over Fennoscandia by 50% in the past 30 years. The first annual Hg mass-balance for a boreal peatland that measured peat-atmosphere exchange revealed so much evasion of the Hg pollution legacy from the peat back to the atmosphere that the mire will have recovered in decades, rather than in centuries as previously assumed. Producing this mass balance was a methodological challenge, but explaining it presents a scientific challenge. We propose that the long history of atmospheric Hg pollution, followed by sharp reductions in atmospheric Hg concentrations, switched the peatland from being a net accumulator of atmospheric Hg for millennia to suddenly becoming a net GEM emitter to the surrounding environment. We propose to test whether a recent reversal in the direction of Hg exchange between peatlands and atmosphere can be modeled by changing GEM concentrations. This model will be constrained by historical peat archives of Hg concentration and isotopic composition, as well as novel measurements of pore atmosphere Hg isotopes. This will provide information on the effectiveness of Hg emission controls for reducing Hg contamination in freshwater fish where peatlands influence aquatic Hg bioaccumulation.
PI: John Marshall
Working with Niles, Natalia, Jose, and Kersti, we have measured sapflux and the stable isotope composition of phloem sap around the tall tower at Svartberget. We will use these data to estimate GPP and compare these estimates to those from eddy flux and from Kersti's model. For precise work, this method requires knowledge of the isotopic composition of CO2 in the tree canopy. We aim to set up this measurement on the tall tower by attaching a Picarro CO2 isotope analyzer to the tower inlets.
PI: Marcus Wallin
To investigate the effects of ditch cleaning on mobilization of aged C we will combine state-of-the-art hydrochemical measurements with novel isotopic tools. Measurements of quantity and age composition of different C species will be made in ground and stream water of the different catchments.
PI: Simon Ponter
The WATERFACE project includes several sub-projects located all over northern Sweden. Data from this request will be used as a reference for meteoric water in an groundwater-tracing study outside Luleå.
PI: Fredrik Lidman
Si is the second most common element in Earth's crust. Since most minerals in forest soils are silicates, the biogeochemistry of Si is crucial for weathering and the release of nutrients to forest ecosystems. This project studies the fractionation of Si isotopes in forests and mires.