Vijay M. Vulava

Multicomponent transport of major cations predicted from binary adsorption experiments

Accurate modeling of multicomponent sorption and transport of major cations in subsurface porous media is a prerequisite for predicting complex environmental processes, such as the movement of trace metals in soils and aquifers. In this study, various cation exchange models were compared in their ability to predict ternary Ca-Mg-Na transport in an acidic soil from binary Ca, Mg, and Na adsorption data. A flow-through reactor technique was used to measure binary adsorption isotherms of Ca, Mg, and Na over wide concentration ranges of the adsorptive and the respective background cations. High-resolution transport experiments were conducted in water-saturated chromatographic glass columns. Three sorption models based on cation exchange . . equations were compared: a 1-site Gaines-Thomas 1-GT , a 1-site Rothmund-Kornfeld 1-RK , . and a 3-site Gaines-Thomas 3-GT model. Although the fit of adsorption data was clearly improved from the 1-GT to the 1-RK to the 3-GT model, transport predictions were overall not improved compared to the 1-GT model. While predictions by the 1-GT and the 3-GT model were virtually identical, predictions by the 1-RK model were partly improved and partly deteriorated. The most simple 1-GT model, therefore, seems to be adequate for predicting multicomponent transport phenomena involving major cations, however, multi-site models may be useful for predicting transport of trace metals in the presence of several major cations. Regardless of the

Sorption, photodegradation, and chemical transformation of naproxen and ibuprofen in soils and water.

Pharmaceutically active compounds (PhACs) are released into the environment where they undergo soil sorption, photodegradation, and chemical transformation into structurally similar compounds. Here we report on studies of naproxen (NAP) and ibuprofen (IBP), two widely-used nonsteroidal anti-inflammatory drugs (NSAIDS), in soils and water. Organic matter (OM) was observed to play an important role in each of these processes. Sorption was observed to be stronger and nonlinear in higher OM soils while weaker but still significant in lower OM, higher clay soils; the amphiphilic nature of these two PhACs combined with the complex charged and nonpolar surfaces available in the soil was observed to control the sorption behavior. Simulated solar photodegradation rates of NAP and IBP in water were observed to change in the presence of humic acid or fulvic acid. Structural analogs of each compound were observed as the result of chemical transformation in both photoexposed aqueous solutions and non-photoexposed soil. Two of these transformation products were detected as both soil and photo transformation products for both PhACs. OM was observed to influence the chemical transformation of both pharmaceuticals.

Dissolution and transport of coal tar compounds in fractured clay-rich residuum.

We investigated the dissolution and transport of organic contaminants from a crude coal tar mixture in a monolith of fractured clay-rich residuum. An electrolyte solution was eluted through the residuum monolith containing a small emplaced source of coal tar under biologically inhibited and mildly acidic conditions. Concentrations of 10 coal tar compounds, representing mono-, poly-, and heterocyclic aromatic hydrocarbons that constitute crude coal tar were monitored in the effluent over a period of 377 days. Most compounds appeared in the effluent within the first 0.1 pore volume eluted indicating the importance of rapid dissolution and transport through the fracture networks. The concentrations continued to rise but did not reach the corresponding effective solubility limit in most cases. Compounds that were less soluble and those that were more susceptible to sorption or matrix diffusion eluted at a much slower rate. Analysis of contaminant concentrations in microcore residuum samples indicated that all 10 compounds had spread throughout the entire monolith and had diffused into the fine-grained matrix between fractures. These data suggest that the predominantly fine pore structure did not appear to inhibit coal tar dissolution and subsequent transport, even though only a small portion of tar was in direct contact with fractures and macropores that control most flow.

Activation of group IVC phospholipase A2 by polycyclic aromatic hydrocarbons induces apoptosis of human coronary artery endothelial cells

Exposure to environmental pollutants, such as polycyclic aromatic hydrocarbons (PAHs) found in coal tar mixtures and tobacco sources, is considered a significant risk factor for the development of heart disease in humans. The goal of this study was to determine the influence of PAHs present at a Superfund site on human coronary artery endothelial cell (HCAEC) phospholipase A2 (PLA2) activity and apoptosis. Extremely high levels of 12 out of 15 EPA high-priority PAHs were present in both the streambed and floodplain sediments at a site where an urban creek and its adjacent floodplain were extensively contaminated by PAHs and other coal tar compounds. Nine of the 12 compounds and a coal tar mixture (SRM 1597A) activated group IVC PLA2 in HCAECs, and activation of this enzyme was associated with histone fragmentation and poly (ADP) ribose polymerase (PARP) cleavage. Genetic silencing of group IVC PLA2 inhibited both 3H-fatty acid release and histone fragmentation by PAHs and SRM 1597A, indicating that individual PAHs and a coal tar mixture induce apoptosis of HCAECs via a mechanism that involves group IVC PLA2. Western blot analysis of aortas isolated from feral mice (Peromyscus leucopus) inhabiting the Superfund site showed increased PARP and caspase-3 cleavage when compared to reference mice. These data suggest that PAHs induce apoptosis of HCAECs via activation of group IVC PLA2.

Storm‐event flow pathways in lower coastal plain forested watersheds of the southeastern United States

The landscape of the coastal plain of the southeastern United States is rapidly changing due to urbanization and climate-change-related impacts. In addition to the forecasted population increase, this region could experience significant changes in precipitation patterns making watershed management very challenging. In order to establish baseline data, storm-event flow pathways were studied in three lower coastal plain (LCP) forested lowland watersheds of the southeastern United States between 2010 and 2011. Two of the watersheds had clay loam subsoils while the third had sandy soils throughout the profile. Stream flow and water samples from water-table wells, piezometers, lysimeters, and rain gauges were analyzed for ion concentrations; ion trends were assessed using principal components analysis; and chemical hydrograph separation was performed for nine storm events using end-member mixing analysis. End-members consisted of lower concentration rainwater; a near-stream source (riparian or streambed groundwater); and a distant or deep groundwater source. Storm-event stream water on the clayey sites was composed primarily of rainwater (45–67% by volume) and shallow groundwater (21–55%), with small inputs from deep (below the clay-rich soil horizon) groundwater (0.2–21%). At the sandy site, a greater proportion was groundwater (56–61%), with smaller inputs from rainwater (28–33%) and soil water (6–16%). Dry antecedent soil moisture (ASM) conditions and larger storms resulted in greater rainwater contribution at the clayey sites. Shallow groundwater was an important contributor even in dry ASM conditions, perhaps due to the high specific retention of the soils. The results from this study will inform researchers about stormwater routing in forested, shallow water table watersheds and provide land managers with baseline data as they plan stormwater mitigation practices.