It has been demonstrated that the toxicity of heavy metals depends on their chemical speciation and can be related to their free ion activities, rather than the total metal concentrations (Steemann- Nielsen and Wium-Andersen, 1970; Sunda and Guillard, 1976; Andrew, Biesinger, and Glass, 1977; Anderson, Morel and Guillard, 1978). The objective of this study was to determine the effect of combined free ions of zinc and copper on the toxicity to the green alga Selenastrum capricornutum. This alga was grown in a defined medium, under controlled laboratory conditions, with a varying range of zinc and copper concentrations. The growth rate of the alga was inhibited at pZn = 5.93 or at pCu = 7.24. The results suggest that when the chemical speciation of combined zinc and copper is taken into account, there is little or no toxic interaction between the two metal ions.

Of the many toxic chemicals released into the Hanford vadose zone over the decades of nuclear weapons production, uranium has emerged as a contaminant of significant interest. The ammonia gas injection remediation method has been identified as a promising approach towards mitigating the risks to the ecosystem by limiting the mobility of the radionuclide in the vadose zone. The remediation method was replicated using synthetic porewater solutions with a range of constituent concentrations equal to that of the Hanford 200 Area vadose zone. The uranium-bearing products of the remediation method were characterized using kinetic phosphorescence analysis for aqueous uranium, scanning electron microscopy with energy dispersive spectroscopy and electron microprobe for imaging and elemental analysis, and a sequential extraction procedure modified for the sample precipitates. Evaluation revealed that the resultant uranium-bearing solids likely took the form of uranium-silicates and uranium carbonates, with the latter being precipitated primarily in mid-to-high bicarbonate samples.

Ochratoxin A (OTA) is a potent mycotoxin found in a wide range of agricultural products that has been linked to mitochondrial damage and renal disease. The standard methods for OTA analysis currently rely on the use of high-performance liquid chromatography (HPLC) coupled to fluorescence detection or mass spectrometry. Toward a highthroughput analysis of OTA, a single-stranded DNA aptamer, modified with a fluorophore, coupled to a complementary sequence, modified with a FRET-based quencher that dissociates in the presence of the target toxin, is proposed. In order to integrate “target trapping,” aptamer immobilization methods were explored to mediate interference issues. Assays were evaluated using wine and blood serum matrices. A solution-based assay in a 96-well plate format provided a limit-of-detection of 2.7 ng/mL which would be suitable for many of the proposed applications. Immobilized aptamer formats, however, were not reliable, and a range of limitations to applications of the assay were identified.

Surface enhanced Raman spectroscopy (SERS) has been widely applied for rapid and sensitive detection of various chemical and biological targets. Here, we incorporated a syringe filter system into the SERS method to detect pesticides, protein toxins and bacteria in water. For the detection of chemical and protein targets, silver nanoparticles (Ag NPs) were aggregated by sodium chloride (NaCl) to form nanoclusters that could be trapped in the pores of the filter membrane to from the SERS-active membrane. Then a coating of capture (e.g. aptamer) was integrated on the nanoparticle substrate if needed. Then samples were filtered through the membrane. After capturing the target, the membrane was taken out and air dried before measuring by a Raman instrument. The developed filter SERS method was able to detect fungicide ferbam as low as 2.5 ppb level and had a good quantitative capability, which could also be carried out on site using a portable Raman instrument. The aptamer integrated filter SERS was able to detect ricin b chain in water at 100 ppb level. The filter membrane was then applied to detect bacteria E.Coli with the integration of 4-mpba as a capture and indicator. With SERS mapping, we can detect E.Coli down to 101 CFU/ml and the viability of bacteria on the membrane could be confirmed by incubating the membrane on TS agar down to 102 CFU/ml. This study shows the filter based SERS methods improve the detection capability in water samples, with a great versatility for various types of assays.

Biochar has been shown to act as an effective sorbent for many organic and inorganic contaminants (including phosphate) and can help to improve the quality of our fresh water resources by preventing eutrophication. Most of the high efficiency biochar phosphate-adsorbent feedstocks are modified with chemical pretreatment, phytoremediation or anaerobic digestion to accumulate desired elements. The main objectives of this project were to first engineer magnesium (Mg) and calcium (Ca) altered biochar by chemical pretreatment followed by pyrolysis at either 350 or 550°C and evaluate their phosphate adsorption rate and potential as compared to their unaltered counterparts. Determination of surface physiochemical characteristics of the unaltered (U350 and U550), Mg-altered (Mg350 and Mg550), and Ca-altered (Ca350 and Ca550) hardwood biochars was also completed. The unaltered biochars did not adsorb any phosphate which was likely due to a lack of Mg or Ca and crystalline structures as confirmed by ICP-AES and XRD. Adsorption kinetics revealed that both the Ca-altered and Mg-altered biochars took about 10 days to reach equilibrium. The Langmuir isotherm model was the best fitting model for all altered biochars and Mg550 adsorbed the most phosphate with a Langmuir maximum capacity (Q) of 135.8 mg/g at pH 9. XRD spectra confirmed crystallinity for both the Ca-altered and Mg-altered biochars for calcite (CaCO3) on the Ca-altered biochar and both periclase (MgO) and brucite (Mg(OH)2)on the Mg-altered biochars. SEM images of Mg550 followed by EDS confirmed the presence of nano-sized flakes on the biochar surface and identified them as the primary phosphate adsorption sites. SEM images of Ca550 identified globular, rather than flakey structures on the biochar surface and EDS offered further confirmation that these were calcite minerals. Although Ca350 and Ca550 adsorbed phosphate from solution, Mg350 and Mg550 exhibited a much greater phosphate sorption potential with Q at 18.91, 16.34, 39.59 and 135.8 mg/g (pH 9), respectively. This may be attributed to the morphological differences between the highly crystalline flake-like structures of the Mg altered biochars and the globular structures on the surface of the Ca altered biochars. The mechanisms revealed for phosphate sorption include electrostatic interactions, precipitation, and ligand exchange.

Indiana University-Purdue University Indianapolis (IUPUI) / Paper spray mass spectrometry (PS-MS) is an ambient ionization technique that has been proven useful in many types of investigative analyses. However, the use of this technique with regards to environmental samples has been largely unexplored since the technique’s development. In this work, paper spray mass spectrometry was utilized to detect and quantify compounds for environmental, forensic and chemical defense applications. Due to the sensitive nature of some projects, the work was split into two volumes. Volume 1 focuses on the detection of pharmaceuticals in soil using paper spray (Chapter 2) and the detection of chemical warfare agent (CWA) simulants and CWA hydrolysis products (Chapter 3). Volume 2 focuses on the detection and quantitation of fentanyl analogs in environmental matrices. Chapter 5 focuses on the rapid analysis of fentanyl analogs in soil matrices. The following chapter evaluates the ability of PS-MS to detect low concentrations of fentanyl analogs in water (Chapter 6). Throughout this work, paper spray has proven to be an effective, rapid alternative to chromatography for the analysis of environmental samples.

No description available.

Surface and groundwaters in contact with mining-exposed pyritic materials have the capacity to generate acid mine drainage (AMD), an acidic, sulfate-rich, metals-laden effluent. The Davis Mine located in northwestern Massachusetts offers a model site to study the processes of natural attenuation of acid mine drainage. These include physico-chemical processes such as dilution and sorption, geochemical processes such as aluminosilicate weathering and biological processes such as transformation and cycling of sulfate, iron and acidity by bacterial metabolism. A focus of recent research undertaken at the site has been characterizing the presence and activity of these bacteria with an aim to stimulate their capacity to attenuate the severity of acidic conditions. To further this investigation, a pilot-scale treatment system was installed, composed of a modified permeable reactive barrier containing organic carbon and limestone. Down-gradient groundwater was sampled over a sixteen-month period for concentrations of dissolved metals, major cations and sulfate, along with pH and redox measurements. The results showed a decrease in dissolved metals, a possible increase in calcium and decrease in sulfate, and measurable increase in pH and corresponding decrease in oxidation-reduction potential. Major decreases in dissolved iron and aluminum were observed, a change which is not entirely consistent with metals removal by combination with biogenic sulfide alone. The additional influence of hydrolysis was proposed and the anticipated action of this alternate process found to bear resemblance to the observed changes. Groundwater composition from the experimental period was compared to previous measurements and significant changes described in pH, iron, aluminum, copper and zinc and to a lesser extent in calcium and sulfate. Comparisons were also made with concurrent surface water compositions and findings of analogous studies. Conclusions that can be drawn include: the pH and redox environment into which a treatment system is placed can greatly influence the reactions which take place, side-reactions which occur in reducing and alkalinity-generating amendments may also have an attenuating effect, and variable processes influence groundwater composition in these biogeochemically complex environments.

Manufactured oxide nanoparticles (NPs) have large production and widespread applications, which will inevitably enter the environment. NPs can interact with proteins in living beings due to the fact that NPs can transport into blood or across cell membranes into cells. Conformational change of protein molecules after sorption on oxide NPs has been reported. Therefore, it is important to understand the adsorption mechanism of protein onto oxide NPs surfaces. Although few works have reported protein adsorption behaviors, a general systematic comparison of the effects of particle size and surface groups on protein adsorption by widely studied NPs still needs to be made. Moreover, the relationship between adsorption maxima, which are related to protein conformational change and particle toxicity, and protein conformational change has not yet been studied. Therefore, in this work, the adsorption behavior of bovine serum albumin (BSA) protein on three types of nano oxide particles (viz., TiO2, SiO2, and Al2O3) was investigated in order to explore their interaction mechanisms, compared with that on regular bulk particles (BPs). The BSA adsorption maxima on oxide particles were regulated by the surface area of oxide particles. BSA adsorption was primarily induced by electrostatic attraction and ligand exchange between BSA and oxide surfaces. Surface hydrophilicity, surface charge and aggregation of oxide particles also affected their adsorption of BSA. Calculations suggested that a multilayer of BSA covered α-Al2O3, and single layer covered the other oxide particle surfaces. Primary structures of BSA molecules were adsorbed and changed on surfaces of oxide particles.

No description available.