Dr. Pamela P Benz

Petroleum products in the environment can produce significant toxicity through photochemically driven processes. Burning surface oil and photochemical degradation were two mechanisms for oil removal after the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico. After burning, residual oil remains in the environment and may undergo further weathering, a poorly understood fate. Although photochemistry was a major degradation pathway of the DWH oil, its effect on burned oil residue in the environment is under studied. Here, we ignited Macondo surrogate crude oil and allowed it to burn to exhaustion. Water-accommodated fractions (WAFs) of the burn residue were created in full sunlight to determine the effects of photochemical weathering on the burned oil residue. Our findings show that increased dissolved organic carbon concentrations (DOC) for the light unburned and light burned after sunlight exposure positively correlated to decreased microbial growth and production inhibition (i.e. more toxic) when compared to the dark controls. Optical and molecular analytical techniques were used to identify the classes of compounds contributing to the toxicity in the dark and light burned and dark and light unburned WAFs. After light exposure, the optical composition between the light unburned and light burned differed significantly (p < 0.05), revealing key fluorescence signatures commonly identified as crude oil degradation products. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis showed more condensed aromatic, reduced oxygenated compounds present in the light burned than in the light unburned. FT-ICR MS also showed an increase in the percent relative abundance of carboxyl-rich alicyclic molecules (CRAM) like compounds in the light burned compared to light unburned. The increase in CRAM suggests that the composition of the light burned is more photorefractory, i.e., reduced, explaining the residual toxicity observed in microbial activity. Overall, these data indicate burning removes some but not all toxic compounds, leaving behind compounds which retain considerable toxicity. This study shows that burn oil residues are photolabile breaking down further into complex reduced compounds.

Undergraduate science, technology, engineering, and mathematics (STEM) experiences have academic, psychological, and social challenges that require additional support to navigate. This article explains the implementation of a STEM peer coaching program designed to provide such support. Through this program, undergraduate STEM students served as STEM peer coaches. Coaches facilitated one-on-one conversations focused on individualized support and skill development. Using carefully constructed planning and reflecting conversations, STEM peer coaches helped students clarify their goals and create plans for success. STEM peer coaches also served as accountability partners. Anecdotal evidence from students who participated in the program shows that STEM peer coaches provided meaningful academic support. The STEM peer coaching program is a model for how peer-led, individualized conversations can be a catalyst for helping students through challenges related to STEM. The article discusses key strategies for developing and implementing a STEM peer coaching program.

Engagement in active learning and learning communities is important for persistence of STEM students early in their academic programs. Colleges and universities have an ongoing call to facilitate active learning techniques, yet large group, lecture-based instruction is still the prominent method of instruction. This qualitative case study examines interviews and classroom observations of undergraduate chemistry students enrolled at a primarily undergraduate institution. Critical educational elements were identified for chemistry students participating in a redesigned, introductory course which included a collaborative peer-lead learning experience. The participants engaged in required, weekly sessions structured around community building and active learning. The data were framed through a community of practice (CoP) framework, and emergent themes were centered on the following components: mutual engagement, joint enterprise, and shared repertoire. Findings show participant engagement created opportunities for collaboration beyond the required, weekly sessions, which included forming study groups and seeking assistance from chemistry tutors. Participants also shared study techniques based on a mutual understanding that effective learning required routine practice. Implications for STEM departments and researchers about implementing research-based curriculum are discussed.

Six new heteroaromatic polycyclic azaborine chromophores were designed, synthesized, and investigated as easily tunable high-luminescent organic materials. The impact of the nitrogen-boron-hydroxy (N-BOH) unit in the azaborines was investigated by comparison with their N-carbonyl analogs. Insertion of the N-B(OH)-C unit into heteroaromatic polycyclic compounds resulted in strong visible absorption and sharp fluorescence with efficient quantum yields. The solid-state fluorescence of the heteroaromatic polycyclic compounds displayed a large Stokes shift compared to being in solution. The large Stokes shifts observed offset the self-quench effect in the solid state.

To determine effects of photochemical weathering of petroleum, surrogate and Macondo (MC252) crude oils were exposed to solar radiation during the formation of Water Accommodated Fractions (WAFs) in sterile seawater. Samples were incubated in either unfiltered sunlight, with ultraviolet radiation blocked (Photosynthetically Active Radiation [PAR] only), or in darkness. WAFs were collected at two time points over the course of a week. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) analyses of water soluble species formed during exposure to sunlight were compared for the different treatments. Photochemical alterations resulted in differences in compound class distributions. In general, surrogate oil was photo-oxidized across a wider carbon number range compared to MC252. While photochemical differences were observed between MC252 and surrogate oils, microbial production in seawater responded similarly to both WAFs from both types of oils with the majority of the inhibition resulting from oil exposure to visible light.
•Petroleum complexity for MC252 and Surrogate oil influences photochemical degradation.•Heteroatom distributions for incubated WAFs were different for Surrogate and MC252.•Surrogate oil is oxidized across a wider carbon number range compared to MC 252.•For both oils, WAFs created in light have increasing oxygenation over time.

Heavy metals found in local water are an environmental concern. These metals are potentially harmful since they can bio-accumulate in organisms and have been classified as toxic and/or carcinogenic. In this study, water was collected from a shipyard located on a bayou. Various materials (chitosan, mixed bed and amphoteric resins) were tested to determine their efficiency for metal remediation. Inductively coupled plasma mass spectrometry (ICP/MS) was used to quantify the efficiency of the materials examined. Overall, amphoteric resin was found to be the most efficient for a greater number of metals examined (Al, Co, Cu, Fe, Mn), followed by mixed bed which most efficiently removed As and Fe. Chitosan showed the poorest efficiency for metal removal.

An experiment exploring the photochemical properties of quinones was developed. Their unique photochemistry and highly reactive nature make them an ideal class of compounds for examining structure−activity relationships. For several substituted quinones, photochemical reactivity was related to structure and ultimately to the Gibbs energy for electron transfer from water to the quinone. Following irradiation with monochromatic light from a laser pointer and quantification by high-performance liquid chromatography with fluorescence detection, a linear relationship was observed for product formation versus calculated Gibbs energy values.

Quinones are known producers of reactive oxygen species (ROS) that may be toxic in natural aquatic environments. In this study, the effects of parent quinones and their photodegradation products on bacterial growth were determined, and photochemical ROS formation rates were measured. Using 3H-leucine incorporation to measure growth of the bacterium Pseudomonas aeruginosa and natural seawater bacterioplankton, growth inhibition was observed when samples were exposed to dichlone, chloranil and sodium anthraquinone-2-sulfonate (AQ2S). For seawater, compared with other quinones tested, dichlone showed the greatest toxicity in the dark, and AQ2S toxicity was greatest during simultaneous exposure to sunlight. Photodegraded chloranil and dichlone showed decreased toxicity compared with nonirradiated samples. For P. aeruginosa, AQ2S and its photodegradation products showed the greatest toxicity during simultaneous exposure to sunlight. Chloranil photodegradation products showed reduced toxicity compared with the parent compound during simultaneous exposure to sunlight. Dichlone was the only compound to show any toxicity to P. aeruginosa in the dark, and its photodegradation products were more toxic than the parent compound. Based on the results of dark and light controlled experiments measuring bacterial growth and estimated ROS production rates, ROS alone does not account for relative differences in toxicity between these quinones.

Whereas [H-3] thymidine ([H-3]TdR) and [H-3] leucine ([H-3] leu) are commonly used to measure bacterial production, their stability during ultraviolet radiation (UVR) exposure has been questioned. Because these molecules prove invaluable in studies examining UVR effects on bacterial production, molecule integrity during and after exposure to UVR is critical. The stability of both radiolabeled and non-radiolabeled leucine and thymidine stability was examined after UVR exposure. Solutions of [H-3] TdR and [H-3] leu were prepared in deionized water, 0.2 mu m-filtered estuarine and marine waters followed by sunlight exposure for 4 h centered around solar noon. Incorporation of each irradiated substrate by bacterioplankton was then determined in Pensacola Bay and Gulf of Mexico waters and compared with incorporation using nonirradiated replicate [H-3] TdR and [H-3] leu solutions. Differences in [H-3] TdR incorporation rates for irradiated versus nonirradiated compounds were of marginal statistical difference when irradiated in seawater but not in distilled water whereas no statistical differences were observed for [H-3] leu. However, nonradiolabeled samples analyzed after solar exposure using high performance liquid chromatography (HPLC) showed no significant difference for irradiated samples versus dark controls. Therefore, UVR exposure has no effect on compound integrity. Furthermore, there is no reason to discontinue use or question results obtained by employing [H-3] TdR or [H-3] leu during simultaneous exposure and incubation experiments measuring bacterial production. This type of incubation can lead to a more realistic view of the cumulative effect of UVR on bacterial production over the day rather than short incubations performed in the dark following exposure to sunlight.