Understanding how to interpret and manipulate large data sets is increasingly important today; however, this experience has been slow to trickle down to the typical undergraduate student. Here, we describe the implementation of a project-based learning experience that uses portable air sensors for the real-time measurement of carbon dioxide, ozone, and particulate matter, providing students with data sets that include thousands of measurements. These projects allow students to design their own research question and then independently carry out relevant air sampling. Data visualization was used as a tool to identify trends and relationships among analytes and was emphasized as a way to effectively present these findings to an audience. We have implemented the projects over two academic years with diverse student populations, from high school summer research students to senior undergraduate and graduate students in an environmental analytical chemistry course. The extent of mentoring, and the students' competencies in atmosphere chemistry and spreadsheet and graphing software, were not equivalent between these groups, but all were able to execute successful projects. The projects often focused on the indoor environment as concentrations are not well characterized and tend to vary with human activity, which lend themselves to the development of testable research questions. The paucity of data on indoor concentrations means that, in addition to a valuable experiential learning opportunity, students were engaged in a legitimate citizen science exercise as they set about characterizing a diverse set of indoor environments.

NOM displays different photochemistry in seawater than in freshwater due to its complexation with Mg2+.

Recent studies have shown that photochemical reactions occurring at the air-water interface are a source of volatile organic compounds (VOCs) to the atmosphere. We report here the photosensitized formation of VOCs from illuminated freshwater and seawater mimics containing nonanoic acid (NA) and/or Suwannee River natural organic matter (SRNOM). Under an atmosphere of air, the total blank-corrected steady-state concentration of VOCs formed from illuminated seawater coated with nonanoic acid is somewhat smaller than that formed from freshwater, suggesting some differences in photochemical pathways for the two substrates. The total blank-corrected steady-state concentration of VOCs more than doubles from both freshwater and seawater NA-coated surfaces under nitrogen compared to air. The addition of SRNOM as a photosensitizer induces some photochemistry from the seawater sample under air, but no chemistry is seen with freshwater, or under nitrogen for either substrate. Adding SRNOM to the nonanoic acid-containing solutions roughly doubles the total steady-state concentration of VOCs emitted from both freshwater and seawater surfaces under air. The small differences in product formation for the two substrates implies some difference in the photochemical mechanisms operating in freshwater versus seawater, which may be due to the presence of halides and metals as well as pH differences between the two aqueous systems. importance and interest. 1,2 The presence of an organic coating, even as little as a sub-monolayer, at a water surface may alter the kinetics of heterogeneous reactions there, with the exact effect depending upon the composition of the monolayer. [3][4][5][6] The air-water interface is also exposed to sunlight for large portions of time, suggesting the importance of heterogeneous photochemistry processes that may occur there. 7 Recent studies have focused on understanding how the air-water interface influences the formation of volatile organic compounds (VOCs) in the aqueous phase and their release into the atmosphere. Field studies found evidence to suggest that the air-water interface is a source of VOCs, such as isoprene and formic acid, [8][9][10][11] which suggests that a marine source of VOCs is more important than previously thought for the global VOC budget. [12][13][14] In addition, it has been suggested that the type of aquatic environment (fresh versus saline) may influence the production of VOCs. 15 Recent laboratory studies, 16-24 using simplified aquatic environments, have shown that photochemistry at the air-water interface serves as a major abiotic source of functionalized VOCs, [25][26][27] which has further implications towards the oxidative capacity of the atmosphere and the formation of secondary aerosols.These laboratory studies have also highlighted the importance of a microlayer in the formation of the gas-phase products. The sea surface microlayer (SML) has been shown to play a crucial role as a boundary in the physical and chemical exchange between the ocean and the atmosphere. 28,2...

We investigated the relationship between changes in fluorescence intensity and in fluorescence anisotropy for Suwannee River Natural Organic Matter (SRNOM) due to the formation of NOM-metal complexes with divalent and trivalent metals commonly present in both fresh water and sea water environments. We chose metal ions whose complexes give rise to both fluorescence quenching (Fe3+, Cu2+) and fluorescence enhancement (Al3+ and Mg2+). Stern-Volmer type analyses quantified the changes in the SRNOM fluorescence as a function of metal concentration. All metals display strong complexation with SRNOM, associated with their effect on fluorescence. Experiments with Fe3+ further show strong effects due to NOM aggregation at all but the lowest metal concentrations studied here. There was little to no change in the conformation of SRNOM as inferred from fluorescence anisotropy caused by increasing metal concentration. These results suggest that there is no correlation between photophysical changes and conformational changes in NOM associated with complexation by the metal ions.