<p dir="ltr">The origins and deposition of nitrate in dust traps in Mojave Desert are examined in this thesis. Two main hypotheses are tested: (1) most of the dust in the traps comes from local soil, implying that the nitrate content is primarily derived from the soil; and (2) wet deposition is the primary source of nitrate found in the environments, implying that precipitation processes play an important role in nitrate accumulation. To test these hypotheses, we collected data from 11 dust trap from locations in of the US Geological Survey's long-term investigation of dust composition and influx rates. Dust and soil samples were analyzed for ions to determine their origins and the contributions of local vs distant sources. Our findings show that the fraction of soil-derived nitrate (<i>f</i><sub>soil</sub>NO<sub>3</sub><sup>-</sup>) is consistently low at all traps, hardly reaching 0.03, whereas the atmospheric nitrate percentage (<i>f</i><sub>atm</sub>NO<sub>3</sub><sup>-</sup>) is usually close to or equal to 1. This shows that atmospheric sources play a substantial role in the nitrate levels detected in dust traps. Nitrate contributions are also significantly influenced by sedimentary and geological settings, such as the distinctions between alluvium and playa regions. Playas, which are composed of silt and clay, may have higher nitrate concentrations than alluvial plains, indicating that external dust inputs are significant. The second hypothesis's results show that nitrate deposition in the study area is primarily from dry sources, with dry deposition values ranging from 0.68 to 10.84 NO₃⁻/kg/ha/yr, averaging 4.12 NO₃⁻/kg/ha/yr, and wet deposition values averaging 1.09 NO₃⁻/kg/ha/yr. This observation challenges the hypothesis that wet deposition is the primary source of nitrate. The dominance of dry deposition is further supported by low amounts of precipitation and a weak correlation between precipitation and dust deposition. This study concludes that although local soil has a role in nitrate levels in dust traps in the study site, it is not the primary source, external sources and dry deposition account for the majority of nitrate in the dustpan</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/26366830 |
| Date | 27 July 2024 |
| Creators | Christian Chimezie obijianya (19208044) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/_b_Examining_the_source_of_Nitrate_Deposition_in_Mojave_Desert_b_/26366830 |
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