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.

In a contaminant study of surface sediments performed in Escambia Bay, Florida, in 2009, DDT was present in 13 of 30 tested sites that were located in the wetlands adjacent to the bay. Concentrations were well above the Florida Department of Environmental Protection's Probable Effect Level (PEL), and ratios of DDT and its metabolites indicated a recent introduction to the system, despite the use of DDT having been banned in 1973. A follow-up study performed in 2016 found no DDT, but did show DDE (a DDT degradation product) at several sites. Spring 2017 sampling showed no DDT, DDE at five of six sampling sites and DDD (another DDT degradation product) at two of the six sites. The appearance of degradation products suggests that DDT degraded or sediment movement brought the degradation products to the sites. In spring of 2018, sediment cores were collected to assess subsurface contaminant concentrations at five sites that consistently had detectable concentration of DDT or its degradation products in previous years. The cores, ranging from approximately 0.2-0.8 meters in depth, were sampled based upon physical characteristics of the sediment. Two methods were used to extract and analyze for DDT and its byproducts from the sediments, a soxhlet extraction (EPA methods 3540c and 3620c) and a microwave extraction (EPA methods 3051a and 3546). Extracts were analyzed using gas chromatography (GC-ECD). Results show the presence of DDE at all five sites tested, DDD at three sites, and DDT at two sites, all at various depths. Of the five tested sites, three sites clearly exhibited decreasing DDE concentration with increased depth and one site exhibited the same decreasing trend but had high levels of DDE at the bottom of the core (>0.5 m depth). DDD showed a similar pattern, decreasing with depth at two of the three sites that is was detected at. There are no evident relationships between particle size and these trends. All samples with detections exceeded the TEL for DDE (17 samples) and DDD (7 samples) but not for DDT; two samples exceeded the PEL for DDD. The trend of generally decreasing concentration with depth of DDE and DDD suggest that the reworking of sediment is not the source of the contaminants. One site had high levels of DDE at depth but is downstream from the other sites and thus cannot be a source of the contaminants, DDT, DDE, or DDD.

Dichlorodiphenyltrichloroethane (DDT) was a commonly used pesticide from World War II through the 1960's. DDT is generally used to control mosquito populations and as an agricultural insecticide. The pesticide and its degradation products (DDD and DDE) can bioaccumulate within ecosystems having negative implications for animal and human health. Consequently, DDT usage was banned in the United States in 1973. In a contaminant study performed in Escambia Bay, Florida, in 2009, DDT was present in 25% of study sites, most of which were located in the upper bay wetlands. Concentrations were well above the Florida Department of Environmental Protection's (FDEP) Probable Effect Level (PEL) and ratios of DDT and its metabolites indicated a recent introduction to the system. A follow-up study performed in 2016 found no DDT, but did show DDE at several sites. The current study repeated sampling in May 2017 at sites from the 2009 and 2016 studies. Sediment samples were collected in triplicate using a ponar sampler and DDT, DDD and DDE were extracted using EPA methods 3540c and 3620c. Extracts were analyzed using a gas chromatograph with electron capture detection (GC-ECD) as per EPA method 8081c. Sediment was also analyzed for organic carbon and particle size using an elemental NC analyzer and a laser diffraction particle sizer. Results show the presence of breakdown products DDE and DDD at multiple sites, but no detectable levels of DDT at any site. Sampling sites with high levels of DDT contamination in 2009 show only breakdown products in both 2016 and 2017. Particle size has little influence on DDD or DDE concentrations but OC is a controlling factor as indicated for contaminated sites by Pearson correlations between OC and DDE and DDD of 0.82 and 0.92, respectively. The presence of only DDD and/or DDE in the 2016 and 2017 studies indicates that the parent, DDT, has not been re-introduced into the watershed since 2009 but is degrading in the environment.

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.