Strategic Environmental Research and Development Program (SERDP, DoD) - ER-2221
Oligomers Derived from Emerging Nitroaromatic Pollutants in Anaerobic Environments: Mechanisms, Fate and Toxicity
Nitroaromatic compounds are used as explosives, pesticides, and pharmaceutical synthons. They enter into aquatic environments after use in agriculture and firing ranges or from industrial and household discharges. In anaerobic environments, the nitroaromatic compounds will undergo reductive (bio)transformation to aromatic amines via nitroso- and hydroxylamine-intermediates. The aromatic amines are reactive with O2, phenol oxidases, or metal oxides, forming oligomeric products that resemble humic like substances. The current paradigm is that the oligomerization of aromatic amines into humic residues only occurs under aerobic conditions. However, preliminary evidence is provided demonstrating that coupling reactions can occur under anaerobic conditions and the resulting dimers and oligomers formed during early stages of polymerization may have important toxicity consequences. Through laboratory experimentation we aim to provide a mechanistic understanding for the anaerobic coupling reactions between reactive intermediates derived from the microbial reduction of nitroaromatic pollutants. We will test three hypothesized mechanisms of coupling. Preliminary data indicate that dimers have an increased toxicity compared to the original nitroaromatic compounds justifying a detailed evaluation of their microbial and aquatic toxicity.
Kadoya, W.M., et al. 2018. Evidence of anaerobic coupling reactions between reduced intermediates of 4-nitroanisole. Chemosphere 195:372-380.
Contaminants of emerging concern in arid and semi-arid environments: Occurrence, source and fate of pharmaceuticals and hormones in the Mexicali Valley region.
(Consortium for Arizona – Mexico arid environments)
In order to maintain growth, dynamics, and environmental sustainability of the arid Mexicali environment and its surrounding valley (with almost negligible precipitation, high evaporation rate, and limited water resources), treatment and reuse of wastewater seems to be the reasonable option. The questionable quality of this water resource is worrisome given the high salinity concentrations and the presence of fecal coliform bacteria, which are evidence of water contamination. Furthermore, reports of contaminants of emerging concern (CEC) entering through the Colorado River, escalating within the region, and partially departing via the Nuevo and Hardy Rivers, raise questions of occurrence, source, and fate of these chemicals in the valley. The situation becomes complex when confronted with the need to increase the amount of water resources for domestic, agricultural, industrial, and ecological purposes through wastewater treatment, reuse, and/or release to the environment. Additionally, surface water leaves the hydrological basin towards the Sea of Cortez, an ecological niche for endemic and endangered species, and toward the Salton Sea, an already polluted lake with notable biodiversity. Herein we have begun to survey the occurrence of selected pharmaceuticals and endocrin disrupting compounds (EDCs) in surface water along the city of Mexicali and its surrounding valley, to identify potential CEC sources, and to determine their fate within the stressed aquatic environment. Selected analytes are being examined in rivers and irrigation features. Additionally, water from certain wastewater treatment plants is being monitored to evaluate the contribution of their effluents to the presence of CEC in the valley’s surface water.
Advancing Informal Environmental STEM Literacy & Learning: Co-Created Citizen Science Rainwater Harvesting in Underserved Communities, a.k.a. UA Project Harvest
National Science Foundation - DRL-1612554
Researchers from the University of Arizona and Sonora Environmental Research Institute will work alongside community environmental health workers, who will then train families residing in environmentally compromised areas (urban and rural) on how to monitor their soil, plant, and harvested water quality.
Prof. Monica Ramirez-Andreotta
Prof. Jean McLain
Flor Morales SERI (Sonoran Environmental Research Institute)