Assessing the presence, concentration, and impacts of trace element contamination in a Chesapeake Bay tributary adjacent to a coal ash landfill (Possum Point, VA).

Coal ash (CA) is an industrial waste product that has been shown to contain several neurotoxic constituents such as cadmium, selenium, mercury, lead, and arsenic. Contaminant-laced leachates enter the environment via seepage, runoff, permitted discharge, or accidental spills from CA storage ponds or landfills which may pose a risk to wildlife residing in receiving waterways. In this study, we assessed 1) the presence and concentration of thirteen trace elements (Al, Ca, Mg, Cr, Cd, As, Se, Pb, Cu, Zn, Mn, Fe, B) in surface water and sediment grab samples using ICP-OES, 2) the temporal variability of trace elements using Pb-210 dated sediment core samples, 3) differences in species diversity using environmental DNA (eDNA) analyses, and 4) the presence and concentration of trace metals in banded killifish (Fundulus diaphanus) epaxial muscle tissue collected from waterways surrounding the Possum Point Power Station (Stafford, VA). Results showed the highest concentrations of As, Cd, Cr, Cu, Fe, Mg, Se, Zn, and B in Quantico Creek (QC) adjacent to the coal ash ponds and elevated average cadmium and zinc concentrations compared to both upstream and downstream locations along the Potomac River. Sediment core profiles and Pb-210 analyses showed historical enrichment of several trace elements in QC beginning after the commissioning of the power plant in 1948. When compared to upstream and downstream sites, species diversity was drastically reduced in Quantico Creek based on eDNA identification. Muscle tissues of banded killifish collected in Quantico Creek displayed increased Al, Cd, and Zn concentrations compared to upstream and downstream sites. Collectively, our results demonstrate the potential impacts of coal ash landfills on aquatic ecosystems and suggest that further research is needed to fully inform risk assessment and remediation efforts.

Investigating the potential impacts of coal ash runoff on the freshwater Seminole ramshorn snail (Planorbella duryi) under laboratory conditions.

Coal fly ash is an industrial waste product generated by coal fired powerplants which has been shown to contain elevated concentrations of several toxic trace metals. When stored in landfills or other repositories, these trace metals can enter nearby surface waters via a number of routes including leaching or runoff. Our study examined 1) the presence and concentration of eleven trace elements in a range of lab-created coal ash leachate solutions at neutral pH using ICP-OES, 2) the physiological effects of these leachate solutions on a freshwater gastropod (Planorbella duryi), and 3) the ability of these trace metals to bioaccumulate in the tissues of exposed individuals. As, Cd, Cu, Mg, Mn, and Pb were detected in solutions at increasing concentrations concurrent with ash concentration. Exposure to leachates caused significant delays in embryonic development, reduced juvenile shell growth, decreases in egg and clutch production, and the display of avoidance behaviors. Tissues of exposed snails contained elevated concentrations of As, Cd, Cu, and Cr, with bioconcentration factors 177,550 times higher in cadmium and 85,468 times higher in arsenic in the highest treatment compared to control organisms. Our results highlight the potential harmful effects of coal ash leachates on a novel freshwater invertebrate species using several unique methodologies, providing key information regarding their potential impacts on surrounding aquatic ecosystems.

The impact of urban expansion and agricultural legacies on trace metal accumulation in fluvial and lacustrine sediments of the lower Chesapeake Bay basin, USA.

The progressively declining ecological condition of the Chesapeake Bay is attributed to the influx of contaminants associated with sediment loads supplied by its largest tributaries. The continued urban expansion in the suburbs of Virginia cities, modern agricultural activities in the Shenandoah Valley, the anthropogenic and climate driven changes in fluvial system hydrodynamics and their potential associated impacts on trace metals enrichment in the bay's tributaries necessitate constant environmental monitoring of these important water bodies. Eight (210)Pb and (137)Cs dated sediment cores and seventy two sediment grab samples were used to analyze the spatial and temporal distributions of Al, Ca, Mg, Cr, Cd, As, Se, Pb, Cu, Zn, Mn, and Fe in the waterways of the Virginia portion of the Chesapeake Bay basin. The sediment cores for trace metal historical fluctuation analysis were obtained in lower fluvial-estuarine environments and reservoirs in the upper reaches of the basin. The trace metal profiles revealed high basal enrichment factors (EF) of between 0.05 and 40.24, which are interpreted to represent early nineteenth century agricultural activity and primary resource extraction. Surficial enrichment factors on both cores and surface grab samples ranged from 0.01 (Cu) to 1421 (Cd), with Pb, Cu, Zn, and Cd enrichments a plausible consequence of modern urban expansion and industrial development along major transportation corridors. Contemporary surficial enrichments of As, Se, and Cr also ranged between 0 and 137, with the higher values likely influenced by lithological and atmospheric sources. Pearson correlation analyses suggest mining and agricultural legacies, coupled with aerosol deposition, are responsible for high metal concentrations in western lakes and headwater reaches of fluvial systems, while metal accumulation in estuarine reaches of the major rivers can be attributed to urban effluence and the remobilization of legacy sediments.

Raising flags: applications of chemical marker groups to study self-assembly, chirality, and orientation of interfacial films by scanning tunneling microscopy.

When used in conjunction with "chemical marker groups" (functionalities such as -Br and -COOH), scanning tunneling microscopy is a powerful tool for studying the properties of liquid-solid interfaces. Chemical markers serve as "flags" for the identification of interfacial structures, allowing, for example, the absolute chirality of optically active molecules self-assembling on a graphite surface to be determined. Subtle changes in the orientation of these chemical functionalities that affect the long-range order of interfacial films have also been observed and explored. Finally, alterations in self-assembly resulting from variations in adsorbate or substrate structure can be deduced by taking advantage of these STM "flags".

Scanning tunneling and atomic force microscopy probes of self-assembled, physisorbed monolayers: peeking at the peaks.

The imaging and control of self-assembled, physisorbed monolayers have been the subject of numerous scanning tunneling microscopy and atomic force microscopy investigations. The successful interpretation of the structures observed in scanning probe images of molecules self-assembled at liquid-solid and gas-solid interfaces has benefited greatly from recent experimental and theoretical work. These studies are converging on a general tunneling mechanism that accounts for the images of weakly bound, insulating adsorbates. Experiments in which the dynamical behavior of these monolayers has been monitored as a function of time both statically and after the introduction of an external perturbation are described, and novel studies of the selective control of monolayer structure that make use of internal and external electric fields, photons, and solvent coadsorption are reviewed.