Publications
Showing 66 results for Author: Alexander Johs
Oct, 2025
Journal
The Efficacy and Ecological Impact of Mercury Sorbents on the Physiology and Reproductive Fitness of Daphnia magna
Environmental mercury (Hg) contamination threatens ecosystems due to its bioaccumulation and toxicity. Effective and sustainable remediation strategies are essential, with carbon-based sorbents like biochar (BC) and activated carbon (AC) gaining attention for their high adsorption capacity and cost-effectiveness. However, their ecological impacts remain poorly understood.…
May, 2025
Journal
Mobilization of Mercury from Contaminated Creekbank Soils
The industrial-scale production and use of mercury (Hg) has resulted in numerous Hg-contaminated watersheds globally. The Oak Ridge Reservation (Tennessee, USA) is an example of a site where industrial use of Hg until the 1960’s led to significant contamination of the East Fork Poplar Creek (EFPC) watershed and the buildup of large Hg inventories in creek banks and floodpl…
Nov, 2024
Journal
S-adenosyl-L-methionine is the unexpected methyl donor for the methylation of mercury by the membrane-associated HgcAB complex
Mercury (Hg) is a heavy metal that exhibits high biological toxicity. Monomethylmercury and dimethylmercury are neurotoxins and a significant environmental concern as they bioaccumulate and biomagnify within the aquatic food web. Microbial Hg methylation involves two proteins, HgcA and HgcB. Here, we show that HgcA and HgcB can be heterologously coexpressed, and the HgcAB…
Aug, 2024
Journal
Sorption kinetics and stability of conventional adsorbents for mercury remediation
In-situ remediation of mercury at numerous contaminated sites worldwide is a challenging and costly endeavor due to the persistency of this contaminant. In this study, we evaluated eight commercially available sorbent media ranging from carbon-, clays- and silica-based materials (PBC– Biochar, eSorb – Sorbster, nsPAC – Powdered Activated Carbon, fsPAC – Powdered Activated…
Jul, 2024
Journal
The Impact of Sorbent Amendments for Mercury Remediation on the Viability of Soil Microorganisms
Mercury (Hg) remediation across contaminated environments in the United States is an ongoing project. As part of the Hg cleanup strategy at East Fork Poplar Creek (EFPC), located in Oak Ridge, TN, the deployment of sorbents is considered. However, the impact of sorbents on soil microorganisms is poorly understood. In this study, we investigated the effect of sorbents on so…
May, 2024
Journal
New Opportunities for Neutrons in Environmental and Biological Sciences
The use of neutron methods in environmental and biological sciences is rapidly emerging and accelerating with the development of new instruments at neutron user facilities. This article, based on a workshop held at Oak Ridge National Laboratory (ORNL), offers insights into the application of neutron techniques in environmental and biological sciences. We highlight recent a…
Jan, 2024
Journal
A hidden demethylation pathway removes mercury from rice plants and mitigates mercury flux to food chains
Dietary exposure to methylmercury (MeHg) causes irreversible damage to human cognition and is mitigated by photolysis and microbial demethylation of MeHg. Rice (Oryza sativa L.) has been identified as a major dietary source of MeHg. However, it remains unknown what drives the process within plants for MeHg to make its way from soils to rice and the subsequent human dietary…
Dec, 2023
ORNL Report
Mercury Remediation Technology Development for Lower East Fork Poplar Creek FY20 Update
Dec, 2023
Journal
Electrochemical properties of the interaction between cytochrome c and a hematite nanowire array electrode
We investigate the interaction of horse heart cytochrome c (cyt c) with hematite nanowire array electrodes by cyclic voltammetry to study the electron transfer between redox active proteins and mineral surfaces. Using this model system, we quantify electron transfer rates between cyt c and hematite under varying electric potential and pH conditions. The results are consist…