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Processes neutralizing atmospheric acidification in a sandy aquifer in Northern Germany
Published in Poul L. Bjerg, Peter Engesgaard, Thomas D. Krom, Groundwater 2000, 2020
G. Franken, W.H.M. Duijnisveld, J. Böttcher, J.W. Molson, K.U. Mayer, E.O. Frind
We determined the yearly acid load from the soil zone to the groundwater from concentrations in the uppermost groundwater zone and the calculated recharge in the period from 1995 to 1997. To quantify the buffering capacity of sulfate reduction, we determined the sulfate input into the groundwater and the sulfate concentration profiles in the groundwater. Sulfur isotopes of sulfate were measured to identify and verify sulfate reduction. The sampling depths were related to groundwater age by simulating groundwater flow, using the reactive transport model MINTRAN (Walter et al. 1994). To quantify the buffering capacity of ion exchange, we took sediment samples from depths down to 20 m and determined cation exchange capacity (with 0.2 N BaCl2) as well as exchangeable cations. The contribution of feldspar weathering to the buffering capacity was derived from the increase of Na in groundwater.
Isotope shifts and band progressions in SO2 rovibrational energy levels: using quantum theory to extract rotational constants
Published in Molecular Physics, 2019
In this work we focus on SO containing only16O, but all four stable sulfur isotopes,32S,33S,34S, and36S, are considered explicitly. The masses used for all atomic species are indicated in Table 1. For each isotopologue, and each v and J value up to J=20, all computed rovibrational energy levels from Paper I and Paper II (including unphysical states) are fit to the symmetric JS functional form of Equation (4). The energetically ordered set of levels is presumed to correspond to and , as per the standard for a prolate symmetric rotor. We call this fitting procedure, which ignores K-doublet splitting, the ‘basic procedure.’
Biogeochemical status of the Paleo-Pacific Ocean: clues from the early Cambrian of South Australia
Published in Australian Journal of Earth Sciences, 2021
P. A. Hall, D. M. McKirdy, G. P. Halverson, J. B. Jago, A. S. Collins
Sulfur isotopes are commonly measured from minerals containing sulfates (δ34Ssulf), which are presumed to represent seawater sulfate compositions, or from sulfides (δ34Spy), which represent fractionation owing to bacterial sulfate reduction (BSR) plus the effects of oxidative recycling (Canfield & Teske, 1996; Halverson et al.,2009). Biogeochemical processes impose significant and predictable isotopic fractionations on sulfur species and, consequently, the isotopic composition of sedimentary sulfides and sulfates are sensitive indicators of environmental change (Hurtgen et al., 2002). The difference between δ34Ssulf and δ34Spy, Δ34S, is interpreted as being broadly connected to the oxidation state of the ocean (Canfield & Teske, 1996). Therefore, an observed increase in average Δ34S values in the late Neoproterozoic is cited as indirect evidence of an end-Proterozoic oxygenation event (e.g. Fike et al.,2006; Halverson & Hurtgen, 2007; Hurtgen et al.,2002). However, other factors may also have contributed to the secular increase in Δ34S during the Ediacaran, such as irrigation of marine sediments by bioturbating animals and more complicated controls on the isotopic fractionation attributable to bacterial sulfate reducers (Canfield & Farquhar, 2009; Canfield et al.,2006; Johnston et al.,2007; Wu et al.,2010). δ34Ssulf peaked at +40‰ across the Proterozoic–Cambrian boundary, whereas δ34Spy values show significant variability throughout the Cambrian period: −30‰ to +53‰ (e.g. Fike & Grotzinger, 2008; Gorjan et al.,2003; Hurtgen et al.,2002; Shields et al.,1999, 2004; Strauss, 2002).