Photo-reduction of mercury (Hg) is an important mechanism for removal of both Hg 2+ species and monomethylmercury (MMHg) from surface waters. Large mass independent fractionation (MIF) signatures of Hg isotopes preserved in natural samples is thought to reflect MIF produced during aqueous photo-reduction by the magnetic isotope effect (MIE). Recently, Hg MIF signatures in natural samples are being used to quantify photochemical reduction in aquatic systems. However, the fractionation factors used are from laboratory experiments that did not investigate many of the environmental parameters that may affect MIF during photoreduction. In this study, the effects of different regions of the solar spectrum on the expression of MIF caused by the MIE during Hg 2+ and MMHg photo-reduction were investigated to assess how the type of radiation affects the extent and signature of MIF. Photo-reduction in the presence of DOM was carried out through exposure to the full natural solar spectrum unfiltered, with the ultraviolet B (UVB; 290-320 nm) portion removed and with both the UVB and the ultraviolet A (UVA; 320-400 nm) removed. There is a clear relationship between the expression and magnitude of MIF and the energy of incident radiation for both Hg 2+ and MMHg photo-reduction. The experiments indicate that MIF produced during photo-reduction

A method was successfully developed for the CSIA of HCH isomers that showed potential for HCH source differentiation and identification of HCH in situ biodegradation. At the HCH-contaminated site, the observed preferential isotopic enrichment of certain isomers relative to others for a given source allows differentiation between biodegraded and non-biodegraded HCH.

Geophysical length scales determined from complex conductivity (CC) measurements can be used to estimate permeability k when the electrical formation factor F is known. Two geophysical length scales have been proposed: (1) the specific polarizability cp normalized by the imaginary conductivity σ″ and (2) the time constant τ multiplied by a diffusion coefficient D+. The parameters cp and D+ account for the control of fluid chemistry and/or varying minerology on the geophysical length scale. We evaluated the predictive capability of two CC permeability models: (1) an empirical formulation based on σ″ or normalized chargeability mn and (2) a mechanistic formulation based on τ. The performance of the CC models was evaluated against measured k; and further compared against that of well‐established k estimation equations that use geometric length scales. Both CC models predict permeability within one order of magnitude for a database of 58 sandstone samples, with the exception of samples characterized by high pore volume normalized surface area Spor. Variations in cp and D+ likely contribute to the poor model performance for the high Spor samples, which contain significant dolomite. Two observations favor the implementation of the σ″‐based model over the τ‐based model for field‐scale k estimation: (1) a limited range of variation in cp relative to D+ and (2) σ″ field measurements are less time consuming to acquire relative to τ. The need for a reliable field‐estimate of F limits application of either model, in particular the σ″ model due to a high power law exponent associated with F.

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