Atmospheric Chemistry Program Seminar
Open to Public
Rapid Wastewater Analysis Platform Based on Surface-enhanced Raman Scattering
by Ya-Chu Chan,
ANYL 1st year, CU Boulder
"Wastewater discharged from electroplating factories contains cyanide and chromium (VI), which could pose a threat to the environment and humans if in high concentration. The standard methods used by the Environmental Protection Agency to detect both species require tedious sample pre-treatments and sophisticated instruments. Owing to these pitfalls, an alternate method that can achieve rapid and on-site detection is important to timely deal with illegal discharge. Surface-enhanced Raman Scattering (SERS) is a vibrational spectroscopic technique that provides “fingerprints” of different entities. It has the potential to apply to wastewater detection because of its high sensitivity, accuracy, and portability. However, several problems have been hindering it from becoming a quantitative analysis method. In this project, a protocol to achieve quantitative SERS is developed. Then, how the SERS signal reflects cyanide and chromium (VI) concentration is studied, and the effect of other ions in wastewater is discussed. These results build the foundation to apply SERS to real wastewater samples. To make it more relevant to atmospheric studies, this talk will end with some comments on recent applications of SERS to aerosol pH measurement."
An evaluation of the sources of tropospheric ozone in the UK
by Johana Romero,
ANYL Postdoc, Volkamer Group
"Ground-level ozone (O3) is a pollutant of concern for policy-makers because of its detrimental effect on human health, agriculture and ecosystems (Fuhrer, 2009; WHO, 2016)(Fuhrer, 2009; WHO, 2016). Near the surface, O3 has an atmospheric lifetime typically of hours. However, in the free troposphere, its lifetime could range from days up to several weeks (Stevenson et al., 2006) allowing O3 to be transported from its point of production downwind over long distances easily crossing countries and even continents (Monks et al., 2015). This trans-boundary nature of O3 and its precursors complicates compliance of air quality standards within the territories (HTAP, 2007). To develop effective emissions policies, it is, therefore, necessary to understand the extent to which domestic emissions and trans-boundary inflow contribute to the O3 distributions across the UK.
An online O3 tagging method based on the procedures described in (Emmons et al., 2012) and (Butler et al., 2018) was implemented into the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to explore the contributions of foreign anthropogenic NOx emissions to the surface O3 in 12 receptor regions in the UK in summertime 2015. Simulations represent well the observed O3 from 20 EMEP ground sites within the UK and Western Europe. Results confirm the importance of short-range transport of O3 from continental Europe to the UK as well as from no-controllable O3 sources, such as the hemispheric ozone, which account for 71% of the total modelled O3 from May to August. The contribution of O3 from European NOx emissions is principally due to the transport of O3 rather than NOx reservoir.
It is shown that emission controls would be required in different source regions for compliance of ozone standards such as maximum daily 8 hours average MDA8 O3 of 50 and 60 ppbv. As an instance, emissions controls in France are important for the south and southeast of the UK, while domestic emissions controls are more relevant for the Midlands and the north of the UK. By contrast, attainment of lower exposure thresholds, e.g., accumulated ozone over 40 ppb AOT40 metric would primarily require the regulation of the hemispheric ozone levels.
The O3 tagged simulation further show that O3 from Germany, the Benelux, France and ship emissions in the North Sea are responsible for the build-up of O3 in the southeast UK during a summertime 2015 pollution episode. Furthermore, process analysis diagnostics demonstrates that vertical mixing in the morning can bring O3 and precursors from the residual layer to the ground, which contributes to the build- up of ozone during pollution episodes."