Multicomponent Simulations of Contrasting Redox Environments at an LNAPL Site

Abstract

A two-dimensional multicomponent reactive transport modeling approach was used to simulate contaminant transport and the evolution of redox processes at a large-scale kerosene-contaminated site near Berlin, Germany. In contrast to previous site-scale modeling studies that focused either on one or two contaminants or on steadystate redox conditions, multiple contaminants and electron acceptors, including mineral phase Iron (III), were considered with an evolving redox zonation. Inhibition terms were used to switch between the different electron acceptor processes in the reaction scheme. The transient evolution of redox zones and contaminant plumes was simulated for two separate transects of the site, which have different geology and ground water recharge distributions and where quite different downstream contaminant and terminal electron-accepting process (TEAP) distributions are observed. The same reaction system, calibrated to measured concentrations along one of the transects, was used in both cases, achieving a reasonable match with observed concentrations. The differences between the two transects could thus to some extent be attributed to the different hydrological and hydrogeological conditions, in particular ground water recharge distributions. Long-term simulations showed that the distribution of TEAPs evolves as Fe(III) becomes depleted, with conditions becoming increasingly methanogenic, leading to changes in contaminant plume lengths. The models were applied to assess the potential effects of planned changes in land use at the site that may affect the ground water recharge distribution. The simulated redox zonation responded strongly to changes in recharge, which in turn led to changes in the contaminant plume lengths.

Stabilisation of groundwater samples for the quantification of organic trace pollutants

“…Instability of TPH aer sampling was suspected because the site is known for high microbial activity and distinct redox zonation. 18,19 However, the samples stored for seven days at +5 C did not show any TPH deterioration (ESI Fig. S4 †).…”

Medical Ethics at Guantanamo Bay and Abu Ghraib: The Problem of Dual Loyalty

“…10 Other instruments such as the U. N. Body of Principles for the Protection of All Persons Under Any Form of Detention or Imprisonment, 11 U.N. Standard Minimum Rules for the Treatment of Prisoners, 12 the Convention Against Torture and Other Cruel, Inhumane, or Degrading Treatment or Punishment, 13 and U. S. military internment and interrogation policies, 14 collectively contain mandatory and voluntary standards barring U. S. armed forces from practicing torture or degrading treatments of all persons. 15 Even though the United States is a signatory government to these international conventions, the Bush Administration claims they have found various "loopholes" that have allowed for a broad interpretation of the laws. These loopholes have also contributed to the "dual loyalty" conflict among the military medical personnel.…”

“…"Pentagon officials offer many reasons for these abuses including poor training, understaffing, overcrowding of detainees and military personnel, anti-Islamic prejudice, racism, pressure to procure intelligence, a few criminally-inclined guards, the stress of war and uncertain lengths of deployment." 37 These abuses should be abhorrent to anyone.…”

Reactive Transport Modeling for Exploring the Potential of Water Quality Sensors to Estimate Hydrocarbon Levels in Groundwater

“…RTMs have shown that hydrocarbons in groundwater can trigger geochemical and biological reactions. Previous RTM studies have simulated the migration of PHC plumes in groundwater by combining the effects of advection, mechanical dispersion, and molecular diffusion (Cavelan et al., 2022; Picone, 2012), equilibrium and kinetic dissolution of PHC compounds (Lekmine et al., 2014; Molson & Eng, 2011), aerobic and anaerobic PHC biodegradation (Colombani et al., 2009; Miles et al., 2008; Ng et al., 2015; Prommer et al., 2002; Schreiber et al., 2004; Vencelides et al., 2007), dissolution and precipitation of carbonate minerals (Maurer & Rittmann, 2004; Spence et al., 2005), sorption of dissolved PHC to organic matter in sediments (Gharedaghloo & Price, 2021; Valsala & Govindarajan, 2018), and (de)sorption of mobilized ions (Cozzarelli et al., 2016; Miles et al., 2008; Ziegler et al., 2017).…”