No abstract

Long-term trends of atmospheric pollutants, particularly ozone (O3) and particulate matter (PM) provide a direct evaluation of the response of the atmosphere to the environmental policies and the variability of anthropogenic and biogenic emissions. Here, we report the assessment of the temporal evolution of the air quality in a tropical urban city (Butuan) in the southern Philippines by evaluating the trends of meteorological conditions (i.e., temperature, R.H., boundary layer height), air pollutants (i.e., PM2.5, NO2, O3) and their precursors (Benzene, Toluene, and Xylene) from 2014 to 2020. During the seven-year measurement, the mean PM2.5 and PM10 mass concentrations were 8.7 ± 3.9 and 24.3 ± 12.0 µg m -3 , with no single day exceeded the daily PM limit. The max concentrations of aerosol occurred during the dry season when the loss of particles through wet deposition was limited. Speciation of PM2.5 indicated that fine aerosol was dominated by sea salt and organic matter (OM). Analysis of the ratio of OM and sulfate indicated that the main source of pollution in the city was wildfire/biomass burning. The average O3 and NO2 mixing ratios during the same period were 22.3 ± 9.5 ppb and 8.1 ± 5.4 ppb while increasing at the rate of 0.409 ppb year -1 and 0.683 ppb year -1 . The highest O3 concentration occurred during the summer months when photochemistry enhanced the formation of tropospheric O3. The increasing O3 trend was attributed to the contribution of anthropogenic VOCs (AVOCs), based on their ozone-forming potentials (OFPs). The seven-year measurement also showcased the variability of the atmospheric pollutants during the COVID-19 pandemic of 2020, when O3 substantially increased due to reduced vehicle transport activities. Overall, our results provide insights to better comprehend the sources of the variability of O3 and PM on a long-term temporal scale, as well as implications on relevant environmental policies in controlling air pollutants in a tropical developing region.

This paper reports on the synthesis and application of Fe3O4/TiO2 nanocomposite. In situ attachment of TiO2 coating to the surface of the magnetic nanoparticles (Fe3O4) was attained by direct condensation of titanium precursors. Characterization result suggests that the average particle size of the synthesized nanocomposite is 10-15 nm. Also, FT-IR result confirms the presence of TiO2 layer in the surface of the magnetic nanoparticles. Furthermore, the prepared Fe3O4/TiO2 nanocomposite was utilized as an active magnetic nanophotocatalyst for the degradation of cyanide. Results show that even at 5.0 mg of Fe3O4/TiO2 photocatalyst, higher cyanide removal efficiency (91%) was obtained when 60 ppm CN- was incubated with the photocatalyst for 30 minutes. Likewise, it has been demonstrated that the synthesized magnetic nanophotocatalyst can be used to degrade cyanide using sunlight as the natural light source. A 94% cyanide removal efficiency was obtained when the sample was incubated with the synthesized magnetic nanophotocatalyst for 120 minutes under sunlight irradiation. Importantly, the prepared magnetic photocatalyst can be re-used several times (up to 5 cycles) without significant changes in the cyanide removal efficiency.