| Description |
In an era of growing urbanization, anthropological changes like hydraulic modification and industrial pollutant discharge have caused a variety of ailments to urban rivers, which include organic matter and nutrient enrichment, loss of biodiversity, and chronically low dissolved oxygen concentrations. Utah's Jordan River is no exception, with nitrogen contamination, persistently low oxygen concentration and high organic matter being among the major current issues. The purpose of this research was to look into the nitrogen and oxygen dynamics at selected sites along the Jordan River and wetlands associated with Great Salt Lake (GSL). To demonstrate these dynamics, sediment oxygen demand (SOD) and nutrient flux experiments were conducted twice through the summer, 2015. The SOD ranged from 2.4 to 2.9 g-DO m-2 day-1 in Jordan River sediments, whereas at wetland sites, the SOD was as high as 11.8 g-DO m-2 day-1. Sediments were observed as both a sink and source for ammonia, whereas for nitrate it was mostly a sink, reflecting a combined effect of bio-chemical reactions like ammonification, nitrification, and denitrification. Ammonium flux at ambient conditions at the 1300 South location was observed to be positive. Interestingly, in the presence of additional bioavailable nutrients, a negative flux was observed as a result of higher nitrification rate instigated by the nutrient pulse, which presumably dominated ammonification. The results from potential denitrification experiments using 15N supported the high denitrification activity in the sediments. Variation in nitrification and denitrification rates was also supported by molecular analysis on amoA, nirS, and nirK genes. Comparing the potential rates of denitrification and nitrification with the in-situ nitrogen flux, SOD, and bio-molecular sediment characteristics provided a useful insight of the nutrient dynamics along the Jordan River and GSL wetland, which can serve as essential additions to the continuing efforts of improving the Jordan River Total Maximum Daily Load (TMDL). |
