TY  - JOUR
AB  - Redox-driven internal phosphorus (P) loading from lake sediments is a key process for propagating and sustaining cyanobacterial blooms in freshwater lakes. Missisquoi Bay in Lake Champlain, VT regularly experiences cyanobacterial blooms driven by internal P loading as well as from seasonal transitions, but the response of dissolved organic matter (DOM) to these changing conditions has previously not been investigated in this system and seldom in other redox-dynamic freshwaters. In this study, Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) has been employed to explore the seasonal transformation and distribution of DOM, including organic P (DOP), from spring 2017 to winter 2018 along with high-frequency geochemical monitoring. DOM was largely composed of allochthonous compounds with unique molecules from seasonal autochthonous sources and greater proportions of N,S-containing formulae after the early summer bloom season and during the winter. DOM compositions from spring to late summer was more aliphatic during the early bloom season, while DOM between late summer to winter was more aromatic with greater similarities between the two seasons. In contrast, DOP compositions from all seasons were highly dissimilar and suggested a compartmentalized water column, where riverine DOP compounds that were degraded during transport and in surface waters were largely absent in the benthic DOP. Additional sediment core incubation experiments were implemented to study the effects of short-term oxygen limitation on DOM and DOP composition to better constrain potential redox-based drivers of their mobility between sediment and the water column. Short-term incubations suggested an increase in aliphatic DOM and new DOP compounds, with little change in aromatic DOM, suggesting selective mobilization driven by microbial iron(III) and manganese(IV) reduction. Together, these detailed FT-ICRMS data show, for the first time, how DOM and DOP from various sources respond to changing physical and geochemical conditions in redox-dynamic freshwaters, demonstrating how these compounds cycle in freshwater settings and likely impact nutrient bioavailability.
AU  - Kurek, M.R.*
AU  - Harir, M.
AU  - Shukle, J.T.*
AU  - Schroth, A.W.*
AU  - Schmitt-Kopplin, P.
AU  - Druschel, G.K.*
C1  - 61870
C2  - 50490
CY  - Radarweg 29, 1043 Nx Amsterdam, Netherlands
TI  - Seasonal transformations of dissolved organic matter and organic phosphorus in a polymictic basin: Implications for redox-driven eutrophication.
JO  - Chem. Geol.
VL  - 573
PB  - Elsevier
PY  - 2021
SN  - 0009-2541
ER  - 

TY  - JOUR
AB  - Denitrification is an important natural attenuation process that has been observed in many fissured and porous aquifers. However, an important factor limiting denitrification in aquatic systems is the microbial availability of electron donors. Pyrite as the most abundant sulfide mineral in nature represents one of the potential electron sources for denitrifiers to reduce nitrate, but the reaction mechanisms coupling denitrification processes to pyrite oxidation are still questionable. We utilized hydrochemical data and stable isotopes of nitrate and sulfate in groundwater, isotope ratios of sulfur compounds in aquifer sediments and tritium based groundwater dating for assessing denitrification processes in a pyrite-bearing porous groundwater system. The oxic part of the aquifer with mean water transit times of approximately 60 years was characterized by nitrate concentrations of around 15 mg/l and ?15N values were similar to those typical for nitrification. In contrast, in the anoxic part with mean water transit times of up to 100 years, low nitrate concentrations accompanied by elevated ?15N values were observed. Furthermore, isotope data of groundwater sulfate and sulfur compounds in the aquifer sediment suggest that pyrite oxidation is the dominant source of sulfate in the aquifer. The trend of increasing ?15N values and decreasing nitrate concentrations in concert with depleted ?34S values of groundwater sulfate similar to ?34S values of pyrite, FeS2, suggests that denitrification is coupled to pyrite oxidation, particularly when water mean transit time is elevated.
AU  - Schwientek, M.
AU  - Einsiedl, F.
AU  - Stichler, W.
AU  - Stögbauer, A.*
AU  - Strauss, H.*
AU  - Maloszewski, P.
C1  - 1890
C2  - 25545
SP  - 60-67
TI  - Evidence for denitrification regulated by pyrite oxidation in a heterogeneous porous groundwater system.
JO  - Chem. Geol.
VL  - 255
IS  - 1-2
PB  - Elsevier
PY  - 2008
SN  - 0009-2541
ER  - 

TY  - JOUR
AB  - Chemical and isotope analyses on groundwater sulfate, atmospheric deposition sulfate and fulvic acids (FAs) associated sulfur were used to determine the S cycling in a karstic catchment area of the Franconian Alb, Southern Germany. Sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy provided information on the oxidation state and the mechanism of the incorporation of sulfur in FAs. During base flow ?34S values of groundwater sulfate were slightly depleted to those of recent atmospheric sulfate deposition with mean amount-weighted ?34S values of around + 3‰. The ?18O values of groundwater sulfate shifted to lower values compared to those of atmospheric deposition and indicated steadiness from base flow to peak flow. The reduced sulfur species (S- 1/thiol; S0/thiophene, disulfide, S+ 2/sulfoxide) of soil FAs averaged around 49% of the total sulfur and ?34S value in FAs was found to be 0.5‰. The formation of polysulfides and thiols in FAs in concert with a decreasing isotope value of ?34S in FAs with respect to those of atmospheric deposition sulfate suggests oxidation of H2S, enriched in the 32S isotope, with organic material. The depletion of ?18O–SO42- by several per mil in groundwater sulfate with respect to those of atmospheric deposition is, therefore, consistent with the hypothesis that SO42- has been cycled through the organic S pool as well as that groundwater sulfate is formed by oxidation of H2S with organic matter in the mineral soil of the catchment area.
AU  - Einsiedl, F.
AU  - Schäfer, T.*
AU  - Northrup, P.*
C1  - 3441
C2  - 24371
SP  - 268-276
TI  - Combined sulfur K-edge XANES spectroscopy and stable isotope analyses of fulvic acids and groundwater sulfate identify sulfur cycling in a karstic catchment area.
JO  - Chem. Geol.
VL  - 238
IS  - 3-4
PB  - Elsevier
PY  - 2007
SN  - 0009-2541
ER  - 

TY  - JOUR
AU  - Meyers, P.A.
AU  - Zsolnay, A.
AU  - Eadie, B.J.
C1  - 19964
C2  - 13132
SP  - 33-37
TI  - Pyrolysis-Mass Spectrometry of Organic Matter in Sediment Trap Material from Lake Michigan.
JO  - Chem. Geol.
VL  - 7
IS  - 1
PY  - 1995
SN  - 0009-2541
ER  - 

TY  - JOUR
AU  - Nordstrom, D.K.
AU  - McNutt, R.H.
AU  - Puigdomènech, I.
AU  - Smellie, J.A.T.
AU  - Wolf, M.
C1  - 19075
C2  - 12130
TI  - Ground Water Geochemistry and Modeling of Water-Rock Interactions at the Osamu Utsumi Mine and the Morro do Ferro Analogue Study Sites, Pocos de Caldas, Brazil.
JO  - Chem. Geol.
PY  - 1991
SN  - 0009-2541
ER  - 

TY  - JOUR
AB  - The sources, fluxes and sinks of dissolved organic carbon (DOC) in a groundwater recharge environment and along a well defined flowpath were investigated in a shallow unconfined aquifer system in Central Ontario, Canada. The initial recharge flux of DOC in the upper vadose zone is estimated to be 49 kg ha-1 yr-1, however, biochemical recycling and retention processes deeper in the vadose zone result in a net DOC flux of about 9.8 kg ha-1 yr-1 to the groundwater. Within the aquifer sequential redox processes observed along the flowpath (OZ consumption, SO4 2- reduction, fermentation) further consume or produce DOC. Characterization of the DOC suggest a predominance of high molecular weight (HMW) aquatic fulvic acids and intermediate molecular weight compounds. Radiocarbon analyses of HMW and low molecular weight DOC fractions in the groundwater indicate: (1) DOC fractions recharging the groundwater system are derived from organic carbon sources in the upper soil zone; (2) 14C reductions in DOC observed along the groundwater flowpath are a combined result of redox processes (DOC oxidation, production) and the gradual input of bomb 14C; and (3) DOC oxidation in the groundwater does not significantly impact the inorganic geochemistry or carbon isotopic composition of the dissolved inorganic carbon pool.
AU  - Wassenaara, L.I.*
AU  - Aravena, R.A.*
AU  - Fritz, P.J.
AU  - Barker, J.F.*
C1  - 40779
C2  - 38873
SP  - 39-57
TI  - Controls on the transport and carbon isotopic composition of dissolved organic carbon in a shallow groundwater system, Central Ontario, Canada.
JO  - Chem. Geol.
VL  - 87
IS  - 1
PY  - 1991
SN  - 0009-2541
ER  - 

TY  - JOUR
AB  - Pyrolysis-mass spectrometry was used to analyze the distribution of the organic material in the upper 40 cm of Venezuela Basin sediments. Box cores from three different provinces were obtained: pelagic (carbonate), turbidite and hemipelagic. With the aid of a relatively straightforward multivariate technique, the spectrographic data were investigated and the geological layers differentiated. These layers were in general agreement with those determined through the visual, X-ray and geochemical analyses of the same cores. The organic material in the pelagic core was poorly mixed, and a gradual alteration of this material with depth had taken place. The spectral pattern characteristic of the uppermost (youngest) layers was similar to those obtained from carbohydrate and/or fatty acid standards, whereas those from the deepest (oldest) layers resembled non-proteinaceous nitrogen containing material. The turbidite and pelagic layers in the turbidite core could be well differentiated according to their origin. A so-called iron-enriched layer in the core could readily be identified as consisting of pelagic rather than turbidite material. Analysis of the organic material from the hemipelagic core showed a strong change in the material at a depth of 12 cm.
AU  - Zsolnay, A.
C1  - 40711
C2  - 40206
SP  - 355-362
TI  - Pyrolysis-mass spectrometry and multivariate data analysis of Venezuela Basin sediments.
JO  - Chem. Geol.
VL  - 92
IS  - 4
PY  - 1991
SN  - 0009-2541
ER  - 

TY  - JOUR
AB  - In continuation of the efforts of Y. Feige and coworkers and J.N. Andrews and coworkers to study the in situ production of environmental isotopes, new experimental results obtained by irradiation of natural rock samples with moderated neutrons are reported. Changes of the Ar and Cl isotope ratios offer an experimentally based correction for in situ 39Ar, 37Ar, 3H and 36Cl isotope production. By comparing the 39Ar, 37Ar and 36Cl isotope production rates and depending on the neutron energy distribution achieved, the mean reaction cross-section for the production of 37Ar from 40Ca is estimated to range from 10 to 19 mbarn.
AU  - Forster, M.
AU  - Moser, H.
AU  - Ramm, K.
AU  - Hietel, B.
C1  - 33337
C2  - 36576
SP  - 325-332
TI  - Investigating the neutron-induced subsurface production of environmental isotopes 37Ar, 39Ar, 3H and 36Cl with neutron irradiation of aquifer material.
JO  - Chem. Geol.
VL  - 79
IS  - 4
PY  - 1989
SN  - 0009-2541
ER  - 

TY  - JOUR
AB  - The bacterial reduction of sulphate is accompanied by oxygen isotope exchange reactions. The mechanisms were not investigated in detail but it is suggested that the formation of sulphate-enzyme complexes as intermediary reaction products are facilitating the exchange of 18O between water and sulphate. Under the experimental conditions the observed fractionation factor is close to 25‰ at 30°C and approaches 27‰ at 17°C. Extrapolated values from a field study indicate a difference of ∼ 29‰ at ∼ 5°C.
AU  - Fritz, P.J.
AU  - Basharmal, G.M.*
AU  - Drimmie, R.J.*
AU  - Ibsen, J.*
AU  - Qureshi, R.M.*
C1  - 33336
C2  - 36577
SP  - 99-105
TI  - Oxygen isotope exchange between sulphate and water during bacterial reduction of sulphate.
JO  - Chem. Geol.
VL  - 79
IS  - 2
PY  - 1989
SN  - 0009-2541
ER  - 

TY  - JOUR
AU  - Wolf, M.
AU  - Breitkopf, O.
AU  - Puk, R.
C1  - 18109
C2  - 10959
TI  - Solubility of Calcite in Different Electrolytes at Temperatures Between 10 and 60COD,1,248C and at CO2 Partial Pressures of about 103 Pascals.
JO  - Chem. Geol.
PY  - 1989
SN  - 0009-2541
ER  -