Introduction

CHEM 305 and project-based learning

Environmental Chemistry II (CHEM 305) is a single-semester undergraduate environmental chemistry course offered at the University of Alberta. The course covers a broad range of topics, including sorption and phase partitioning; hydrolysis reactions; diffusion; properties and behavior of particles, including sedimentation, coagulation, and light scattering; and the significance of particulate matter in the atmosphere. The student population is similarly diverse: in Winter 2017, for example, only nine of the 22 students taking the course were enrolled in the focused BSc Honors and BSc Specialization programs offered by the Department of Chemistry; in addition, of the students enrolled in general programs, three were pursing minors in chemistry and one was not pursuing a chemistry degree at all.

CHEM 305 is a laboratory-focused course in which lectures provide students with the theoretical background required to understand the experiments they will perform and build on those experiments by illustrating real-world applications of relevant concepts. CHEM 305 laboratories currently focus on student technical skill development, and are thus highly structured. Given the course’s diverse enrolment, however, we saw value in exposing students—many of whom will not pursue careers in chemistry—to all steps of the scientific research process, from hypothesis development to communication of final results.

In Winter 2017, we integrated a new project-based learning (PBL) component into CHEM 305. PBL is a pedagogical approach in which students actively participate in the investigation of real-world problems and in the process gain experience in asking questions, predicting results, designing and carrying out experiments, analyzing data, and communicating results to others [1]. In the undergraduate chemistry context, PBL often takes the form of student-designed research projects of varying scope and complexity [2,3,4,5,6,7,8,9]. PBL and other active learning approaches can sometimes be met with student resistance [10], and student feedback collected as part of some of the PBL initiativescited above indicated that students were often challenged—and in some cases frustrated—by the process, despite also finding it rewarding [3, 9]. However, student responses also highlighted a wide range of benefits of PBL, including increased confidence in the laboratory and with research in general [2, 4, 5], improved experimental design skills [4], and development of critical thinking skills [5, 9]. In addition, students reported that they enjoyed the freedom to plan their own experiments and take ownership over their own projects [2, 3, 8].

Given that the CHEM 305 curriculum includes a number of topics related to particle behavior, our PBL initiative consisted of student-led air quality monitoring projects conducted with the AirBeam monitor, a portable, low-cost instrument for measurement of fine particulate matter in the atmosphere. In this project, students were asked to engage with the primary literature to discover areas of current interest in urban and indoor air quality, formulate a hypothesis testable using the AirBeam, design and conduct an air sampling campaign, and prepare both an oral presentation and a journal-style article summarizing the main findings of their campaign and discussing its broader implications.

PM2.5: sources, impacts, and monitoring

PM2.5—particulate matter (PM) with a diameter less than 2.5 micrometers—is released directly into the atmosphere by both natural sources, such as forest fires and volcanic eruptions, and anthropogenic sources, such as vehicles and industrial processes [9]. It also forms in the atmosphere via the oxidation of precursor emissions [9, 10]. PM2.5 is not a homogeneous entity but rather is made up of a complex mixture of particles, the chemical composition of which changes with atmospheric residence time [11, 12].

As a result of its small size, PM2.5 can deposit farther into the human respiratory system than larger particles, and consequently has an increased negative impact on human health [13]. In 1993, Dockery et al. reported a strong correlation between PM2.5 levels and mortality rates in six United States cities [14]. This study, commonly referred to as the Six Cities study, played a major role in the subsequent United States Environmental Protection Agency (EPA) decision to establish new regulations specifically for PM2.5 [15].

Measurement of ambient PM2.5 concentrations is typically conducted at fixed air quality monitoring stations, which often also collect meteorological data and concentrations of other regulated pollutants (e.g., NO2 and O3). In the Edmonton area alone, Alberta Environment and Parks runs eight air quality monitoring stations [16]. In Canada, chemically speciated PM2.5 measurements are made as part of the National Air Pollution Surveillance (NAPS) program [17]. In the United States, these measurements are conducted through the PM2.5 Chemical Speciation Monitoring Network (CSN) and the Interagency Monitoring of Protected Visual Environments (IMPROVE) network [18].

Air quality monitoring networks are designed to provide insight into pollutant exposure at the population rather than individual level. In recent years, however, advances in sensor technology [19], coupled with measurements of strong spatial gradients in air quality [20, 21], have spurred interest in personal pollutant exposure assessment [22, 23]. In this context, growing numbers of manufacturers are producing compact, inexpensive, and portable PM2.5 monitors suitable for this purpose, including the Dylos, MetOne, Air Quality Egg, and AirBeam monitors [24]. All of these devices are significantly less expensive than conventional PM2.5 monitoring equipment, and are therefore also ideal tools for classroom exploration of air quality issues.

Materials and methods

The AirBeam PM2.5 monitor

The AirBeam (http://www.takingspace.org/aircasting/airbeam/) is a low-cost, portable instrument that uses a light scattering method to determine PM2.5 mass concentrations (μg m–3) in ambient air. Measurements are communicated once per s via Bluetooth to the AirCasting Android mobile app, which allows for real-time visualization of PM2.5 data. Collected data can also be uploaded to the AirCasting crowdsourced air quality map (http://www.aircasting.org/map) for others to view. The AirBeam sampler used in this study has recently been discontinued; a new version released in March 2018, AirBeam2, has additional functionality.

Several studies have shown that AirBeam measurements of ambient and laboratory PM2.5 are reasonably well-correlated (R2 = 0.42–0.94) with those from co-located EPA-approved analytical instruments [24,25,26]. However, the AirBeam has been shown to exhibit a negative bias compared with PM2.5 levels reported by these reference instruments, especially at elevated PM2.5 concentrations, which restricts its use in a regulatory context [25, 26]. Despite this limitation, it remains suitable as a teaching tool, especially since our students’ research projects primarily involve measurement of changes in PM2.5 levels in response to emission events or changes in sampling location.

Project structure and course integration

In order to successfully complete the PBL component of CHEM 305, students were required to conduct literature searches, propose a research project, design and perform experiments, give an oral presentation, and complete a final written report. Although students worked in self-selected partners or groups of three, each student was required to submit an individually written research proposal and final report in the style of a journal article, the latter of which was due on the final day of the term.

As outlined in the class syllabus provided in the electronic supplementary material, although the project itself was conducted outside of the classroom, three class periods were reserved for project-related lectures. The first such lecture, reproduced in the electronic supplementary material, served to introduce students to PM2.5 and its significance, outline current research interests in the field, and motivate and inspire students to develop their own research projects. The second lecture, delivered by a science librarian, focused on strategies for engagement with the primary literature. The third lecture, delivered by a representative from the University of Alberta’s Centre for Writers, focused on the development of science writing skills.

After the second in-class lecture, students were given 3 wk to independently engage with the primary literature, propose a suitable research question/hypothesis, and develop a detailed experimental plan. Throughout this period, students were encouraged to meet with the instructor to discuss their plans and receive feedback on their research proposals; many student groups took advantage of this opportunity. Student projects were conducted over a 1-mo period; during this time, students used an online booking system to sign out AirBeam monitors and accompanying Android tablets for 1-wk blocks.

The culmination of the project was the CHEM 305 Research Symposium, which took place over six class periods in March–April 2017. During the symposium, student groups delivered 15-min presentations that summarized the results of their research projects. The audience was encouraged to ask questions, which strengthened the presenters’ ability to communicate scientific results in a conference setting.

Project grading

Templates and guideline documents were provided to students to aid them in writing their project proposals and final project reports. Student proposals and project reports were graded by the instructor according to the detailed grading schemes presented in these documents. Student presentations were peer graded according to five evaluation criteria: sufficient contextualization of the project; clear presentation of data; discussion of the “take-home” message of the project; oral presentation skills; and visual quality of the presentation slides. Student participation during the presentations and the quality of students’ peer-review comments were also graded, which encouraged students to engage in critical thinking and pose meaningful questions. All guideline and grading documents are provided in the electronic supplementary material.

Results and discussion

Student research outcomes

Although all students were provided with the same tool, the AirBeam air quality monitor, the research autonomy provided through PBL allowed students to be flexible with their experimental emphasis. As shown in Table 1, students used the AirBeam to answer research questions on topics ranging from the influence of candle burning on indoor air quality to the effectiveness of local smoking bylaws and in locations ranging from light rail transit platforms to construction sites. Since our primary focus here is not to evaluate the specific research outcomes of each individual project but rather to assess the pedagogical utility of the PBL process itself, we present in the following paragraphs several overarching insights collected from selected student projects.

Table 1  Student research projects: activities and main findings
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Some student groups chose to focus on the measurement of PM2.5 concentrations in readily available field environments and the subsequent interpretation of the data collected. For example, one group investigated the effect of paraffin table candles on air quality in a restaurant where one group member worked (Project 1), and a second group measured PM2.5 levels in a busy university food court (Project 2). As shown in Fig. 1, students in the second group could see a measurable increase in PM2.5 concentrations as they passed an open-kitchen food vendor, which simultaneously highlights the spatiotemporal variability of PM2.5 levels and the utility of personal air quality measurements.

Fig. 1
figure 1

Real-time AirBeam measurements of PM2.5 concentrations during a one-way walk through a segment of a university food court

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Although the AirBeam is an excellent pedagogical tool for measuring ambient PM2.5 levels in different environments, some students chose to study changes in PM2.5 levels as a result of experiments performed under (relatively) controlled conditions, and thereby gain experience with the experimental design process. For example, one student group investigated correlations between cooking practices and indoor PM2.5 exposure (Project 7). In particular, these students measured PM2.5 concentrations as a function of cooking oil type, the presence/absence of food, cooking temperature, and the distance between the AirBeam and the cooking surface. As a result of their systematic approach to the project, these students were able to conclude that PM2.5 concentrations were positively correlated with cooking temperature and inversely correlated with the smoke point of the oils and the measurement distance. In another case (Project 10), students built a custom experimental apparatus to evaluate the effectiveness of two types of low-cost, single-use dust filtration masks in reducing PM2.5 exposure. As shown in Fig. 2, these students used one AirBeam to measure PM2.5 concentrations immediately next to a burning candle and another AirBeam to measure PM2.5 concentrations in an enclosure, the inlet of which was equipped with the dust filtration mask of interest. Air flow through the enclosure was controlled using an AirChek personal air sampling pump, which these students took the initiative to learn how to use. Surprisingly, students in this group observed elevated PM2.5 concentrations in the enclosure, which suggests either that the masks employed were not effective in filtering combustion-generated PM2.5 or that the enclosure inlet was not completely sealed.

Fig. 2
figure 2

Student-designed apparatus for investigation of the PM2.5 filtration efficiency of disposable dust filtration masks

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A separate group of students (Project 8) hypothesized that essential oil diffusers would serve as an indoor source of particulate matter (i.e., secondary organic aerosol) via reaction of volatile organic fragrance compounds with atmospheric oxidants [27], and thus that the AirBeam would measure elevated PM2.5 levels when essential oils were used. In this context, these students planned to study the influence of essential oil type on PM2.5 formation. However, through analysis of data obtained during their experiments, students in this group found not only that there was no significant difference in PM2.5 production by the essential oils studied but also that the use of essential oils did not result in a measurable increase in PM2.5 levels. As a result of this experimental “failure”, which is rare in a traditional classroom laboratory setting, these students learned to work with unexpected data in an ethical fashion, and came to realize that not all valid hypotheses are ultimately supported by experimental data.

Despite the range of research questions explored as part of this project, common results and themes emerged, and students thus had the opportunity to see how their individual research projects intersected with those of their peers. For example, two student groups explored the influence of candle combustion on indoor air quality—one group (Project 1) investigated the effect of paraffin oil candles on restaurant air quality, whereas another (Project 9) compared PM2.5 emission by organic and synthetic candles. In their reports, some students in these groups compared their results to previous work on PM2.5 emissions by candles [28], and others took the initiative to compare the maximum PM2.5 levels observed in their experiments to the Canadian Ambient Air Quality Standard for this pollutant class (Fig. 3). In both cases, students found that candles released a large amount of PM2.5 upon being extinguished. These results were subsequently applied by students in Group 10, who used extinguished candles as a source of PM2.5 with which to show that disposable dust filtration masks did not effectively reduce PM2.5 exposure. Results from this project, in turn, intersected with work by students in Project 3, who measured elevated PM2.5 levels in a construction zone on the same floor of the building where CHEM 305 classes were held. Together, these projects prompted discussion regarding the efficacy of typical personal protective equipment and highlighted the interdisciplinary nature of scientific research.

Fig. 3
figure 3

Real-time AirBeam measurements of PM2.5 concentrations after extinguishing six candles in a restaurant setting. The horizontal red line represents the Canadian Ambient Air Quality Standards (CAAQS) red management level for PM2.5 (24 h average; 28 μg m–3)

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Summary of pedagogical outcomes

Throughout the AirBeam project, CHEM 305 students were encouraged to chart their own paths, and thus discover both the challenges of independent research and the excitement that comes with obtaining results that are truly new. In the process, students gained experience with the entirety of the scientific research process, including literature engagement and hypothesis development, experimental design, selection and performance of appropriate control experiments, extraction of information (i.e., meaning) from complex data sets, and presentation of an overarching scientific narrative in both oral and written form. Perhaps most importantly, the breadth of topics explored during the AirBeam project highlights the project’s success in encouraging students not only to find creative solutions to experimental challenges but also to ask creative questions.

Broader applicability

Given our demonstrated success in incorporating a PBL component into CHEM 305, we were interested in learning whether the AirBeam project could translate to other educational contexts. MacEwan University, also located in Edmonton, offers a second-year field-based physical sciences course (PHSC 200), which focuses on field skills development in environmental chemistry, earth science, and physics. The field component of this course is carried out in Edmonton and on the Big Island of Hawaii, and has traditionally included analysis of soil, water, and atmospheric gases. In Summer 2017, the course was modified to include the use of AirBeams to collect PM2.5 measurements at field sites in Edmonton (n = 3) and Hawaii (n = 10). All field exercise materials are presented in the electronic supplementary material.

Due to the more introductory nature and the shorter timeline (6 wk) of PHSC 200 compared with CHEM 305, a more traditional laboratory approach was taken, in which students were responsible for collecting data and answering instructor-developed questions that focused on comparing PM2.5 concentrations between sites and providing rationalizations for observed differences. For example, since the Hawaiian campaign included measurements at both sea-level and mountaintop sites, students were asked to explore the influence of elevation on PM2.5 concentrations. As expected, students observed low PM2.5 levels at most mountaintop sites (e.g., the Mauna Loa Observatory), which is consistent with the location of these sites in the free troposphere [9, 29].

Although most of the research questions generated by CHEM 305 students focused on anthropogenic influences on PM2.5 concentrations, PHSC 200 students made measurements in more remote areas, which enabled them to investigate natural sources of PM2.5. For example, students found elevated PM2.5 concentrations on Waipi’o Beach compared with the other remote sites studied, which highlights the importance of marine aerosol generation [30]. PHSC 200 students were also tasked with measuring CO, O2, SO2, and H2S concentrations at each of the sampling sites using a commercial gas analyzer (Altair 5X, MSA), and in some cases, students were able to use these measurements to provide additional insights into observed PM2.5 concentrations. For example, students found that concentrations of SO2 and PM2.5 were both elevated at Sulphur Banks (Ha’akulamanu), Hawaii Volcanoes National Park, which may have reflected the formation of sulfate aerosol from precursor gases [9]. In summary, the use of AirBeams in PHSC 200 demonstrates both the utility of these monitors in a non-PBL setting and the broader applicability of AirBeams as a tool to investigate and teach natural phenomena in a field setting.