The importance of assessing Mercury in ambient air in Mexico City
Rodolfo Sosa Echeverría1,*, Gilberto Fuentes García1, Pablo Sánchez Alvarez1, Alejandro de David Palacios Ibarra1, David Gay2, and David Grande3
The impact of mercury on the environment has long been widely known: air, water and soil, as well as its concentrating effect in food chains. Likewise, the complexity of its measurement must be recognized, especially due to technical difficulties and of course the cost involved in the measurement. In the case of the determination of mercury in ambient air, the National Atmospheric Deposition Program (NADP) carries out its measurement through the Atmospheric Mercury Network (AMNet).
The National Autonomous University of Mexico (UNAM) collaborates with NADP in the lines of research on the assessment of wet atmospheric deposition in some regions of North America, the evaluation of reactive nitrogen in ambient air and in wet atmospheric deposition and, starting in 2023, in the measurement of mercury in ambient air, having installed a Tekran analyzer at the air quality monitoring station located at the Institute of Atmospheric Sciences and Climate Change (ICAyCC) of the UNAM.
The monitoring of mercury in ambient air began on June 6, 2023, and through March 8, 2024, made 74,576 measurements of elemental mercury concentration every 5 minutes. The data analysis corresponded to different levels of validation according to US-EPA protocols. The maximum concentrations of mercury were 10 to 20 ng/m3 for some days, with the minimum concentration of 1.33 ng/m3. The average and median of the study period were 3.33 and 3.10 ng/m3, respectively. A daily average concentration of 3.31 ng/m3 and a median of 3.14 ng/m3 over the 276 days of monitoring. The minimum and maximum daily concentrations were between 1.97 and 6.52 ng/m3. The hourly behavior (0 to 23 hours) of mercury concentrations indicated that the maximum value was measured between 5 and 6 am at 3.66 ng/m3 and a minimum of 2.90 ng/m3 at 3 pm. The hourly average was 3.33 ng/m3 with a median of 3.34 ng/m3. Finally, the maximum mercury concentration of 20.36 ng/m3 was recorded on Wednesday, followed by Thursday with 15.85 ng/m3 and Monday with 15.69 ng/m3. The rest of the days indicated a maximum concentration level between 11.20 and 14.49 ng/m3.
It is worth mentioning that the monitoring site at UNAM corresponds to a school activity in an urban area. It is also recommended to increase the number of sites for measuring mercury in ambient air in industrial areas and in regions of international interest such as the Gulf of Mexico.
1 Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México, Mexico City, Mexico
2 National Atmospheric Deposition Program, Wisconsin State Laboratory of Hygiene, University of Wisconsin-Madison, WI
3 EEMS Inc., Beaver Dam, WI
* Corresponding Author: rodsosa@unam.mx