Sulfur and nitrogen compounds in wet atmospheric deposition on the coast of the Gulf of Mexico from 2003 to 2015

Ana Luisa Alarcón Jiménez, Elías Granados Hernandez, María del Carmen Torres Barrera, Mónica Jaimes Palomera, Pablo Sánchez Álvarez, Rodolfo Sosa Echeverría

Autores: Rodolfo Sosa Echeverría, Ana Luisa Alarcón Jimenez, María del Carmen Torres Barrera, Pablo Sánchez Alvarez, Mónica Jaimes Palomera, Elías Granados Hernández,* David Gay

* Departamento de Ciencias Ambientales | Contaminación Ambiental



he Gulf of Mexico region has important sources of acid rain precursors, located in all of the countries; U.S., Mexico and Cuba, and so it is very important to study the chemical composition of the wet atmospheric deposition in all coastal areas. For many years along the U.S. Gulf Coast, acidic precipitation has been measured. Measurements along the Mexican Gulf Coast were begun in 2003. The aim of this study was to evaluate pH, sulfate, nitrate and ammonium concentrations in wet atmospheric deposition, collected daily from 2003 to 2015 at La Mancha (LM), Veracruz and compare the values with the National Atmospheric Deposition Program (NADP) sampling sites located along the U.S. coast of the Gulf of Mexico.

The annual Volume Weighted Mean (VWM) pH in wet deposition at La Mancha site ranged from 4.81 to 5.40, which is similar to the U.S. Gulf sites. Additionally, the annual VWM SO42- concentration was from 15 to 31 μeq/L, which is higher than the U.S. sites. Annual VWM NO3- concentrations were from of 3.5 to 15 μeq/L, which is lower than all the U.S. sites. At the Mexican site, the SO42-/NO3- ratio was 4.90 and higher than all of the U.S. sites, which were between 1.03 and 2.38. For LM, the median NH4+/NO3- ratio was 0.77, similar to the Florida sites (0.53–0.91), and below the values measured for Louisiana and Texas (1.07–1.5). The Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) was applied in order to identify the emission sources for the pollutants seen at LM. Trajectories showed an important transport to LM from the East (open water) during the rainy season. The region located East of La Mancha shows offshore petroleum operations as sources of acid rain precursors and deposition of acidifying and nitrogen containing compounds. It is important to consider the sulfur dioxide emission sources in the Mexico Gulf region, and to extend the atmospheric deposition sampling to other sites along the Mexican Gulf coast and Cuba.