Recent Changes in Mercury Cycling within the Conterminous United States

The natural cycling of mercury (Hg) has been augmented by anthropogenic activities, including mining, waste incineration, and the combustion of fossil fuels. The subsequent enrichment of Hg in air, soils, and surface waters has caused concern, due to the adverse health effects of mercury on humans and wildlife. In the United States, policies like the Clean Air Act Amendments of 1990 and the Mercury and Air Toxics Rule have led to decreases in domestic emissions, but global emissions have increased in recent years and now dominate U.S. emissions. As a result, uncertainties remain regarding how quickly and to what extent changes in environmental Hg concentrations will occur. Such evaluations often rely on the availability of long-term monitoring data or a robust reference point for comparisons. In this dissertation, I utilize a series of publicly available long-term monitoring datasets to evaluate changes in Hg concentrations in air, precipitation, and soil. I present a formal analysis of soil Hg stocks in the top 1 m of soil of the conterminous United States (CONUS), which may be used as a future reference point for the evaluation of changes in national soil Hg reservoirs. Finally, I measured Hg in a time-series of archived organic soils from the Hubbard Brook Experimental Forest, NH. In Chapter 2 of this dissertation, I perform trend analyses on monitoring data of Hg in air and precipitation across CONUS. Monitoring data were obtained from the Mercury Deposition Network (MDN; precipitation Hg concentrations, wet deposition, precipitation volume), Atmospheric Mercury Network (AMNet; air Hg concentrations), and the National Emission Inventory (NEI; mercury emissions). Trends in precipitation mercury concentration and wet deposition were primarily found to be decreasing over time, though trends exhibited a distinct spatial pattern; most sites located in the eastern U.S. were decreasing, while sites in the western United States mostly included non-significant or increasing trends. Precipitation quantity increased at several sites, offsetting decreases in Hg concentration. Atmospheric fractions of Hg largely decreased across CONUS, particularly for gaseous oxidized Hg. Broadly, the changes in precipitation and atmospheric Hg matched the spatial patterns of decreased emissions. In Chapter 3, I utilize a large-scale US Geological Survey (USGS) soil survey to examine the distribution of Hg in the top meter of soil across CONUS. Soil Hg concentrations were found to be highest in surface soils, suggesting atmospheric inputs are the dominant Hg source to soils. Landcover exhibited a significant impact on soil Hg concentrations, with the highest concentrations being associated with forested, developed, and cropland landcover types. Conversely, barren and shrubland landcover types were found to be the lowest in Hg concentration. Ecoregion also had a significant effect on Hg concentration, with colder, wetter climates containing higher concentrations of Hg. Soil Hg pools were calculated for 11 layers, cumulatively representing the top 1 m of soil, and totaling 158 ± 2 Gg Hg for the conterminous U.S. Assessment of the provenance of soil Hg using bedrock titanium normalization suggests that 62%–95% of soil Hg is unexplained by parental sources. In Chapter 4 of this dissertation, I utilize archival soil samples from the Hubbard Brook Experimental Forest to examine trends in forest floor Hg spanning nearly 50 years. Hg concentrations were found to be significantly decreasing over time in both the Oie and Oa horizon at a rate of 1.6% and 0.8% per year, respectively. Only the Oe horizon was found to consistently differ in Hg content between paired sampling events, suggesting that this stage of soil organic matter decomposition was particularly important for the fate of Hg in soil. Overall, this work demonstrates that reductions in Hg emissions confer meaningful benefits to the environment in the form of decreasing Hg concentrations in air, precipitation, and soils

Measures of Center of Pressure and Lower Leg Muscle Electromyography during Landing before and after Plantar flexor Stretch

Static stretching of the plantar flexor muscles is reported to modify neuromuscular responses to external stimuli. However, it is not known how these muscles respond to external loading in an applied task, such as single-leg drops. Further, if mechanical laxity in the plantar flexor muscles is present after stretching of it is unclear how this laxity will influence the muscle activation and movement patterns of the lower extremities. PURPOSE: This study is intended to further explore the response of the lower extremities to plantar flexor muscle stretch in an effort to understand its impact on potential injury. METHODS: Five participants (20.6 ± 1.1 yrs: 1.78 ± 0.1 m:, 80.6 ± 9.9 kg) performed drop landings from a 30 cm box onto a force platform before and immediately after 10 min of passive plantar flexor stretch. Surface electromyography (EMG) was collected from tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG), peroneus longus (PL), and soleus (SOL) muscles. Maximal isometric plantar and dorsi flexion efforts were performed before and after 10 minutes on passive plantar flexor stretch. EMG were normalized (NEMG) to maximum values during the maximal isometric efforts. Variables of interest were NEMG at landing and center of pressure (COP) measures. NEMG were assessed 300 ms prior to and after landing onto the force platform. An inertia measurement unit (IMU) was fixed to the tibia to record landing. Comparisons were performed at landing for NEMG and COP/COP velocity up to 5 sec after landing to measure COP/COP velocity variability. Alpha was set at 0.05. RESULTS: NEMG signals differed over time for all muscle from -300 to 300 ms (all p \u3c 0.01). Significant differences in NEMG amplitude were present in MG (0.44 ± 0.5 vs 0.36 ± 0.4), LG (0.28 ± 0.3 vs 0.24 ± 0.3), and SOL (0.40 ± 0.5 vs 0.32 ± 0.3) muscles (all p \u3c 0.05) before and after stretch. COPx (pre: -Δ29.8% post: -Δ56.4%) and COPy (pre: -Δ58.8%, post: -Δ 53.5%) variability measures were significant reduced over time (p \u3c 001). A significant time x condition interaction was present for COPx velocity variability (F6,308 = 2.135, p \u3c 0.049). CONCLUSION: Passive prolonged stretching of the plantarflexor muscles can modify a functional dynamic activity, such as single-leg drop landings. Although COP was not different between the landing before and after static stretch, the control of the balance at landing was different

Precipitation is a Strong Predictor of Airborne Ammonia Levels.

USU senior Connor has lived in the Uintah Basin all his life and studies kinesiology. Senior Casey, a Cache Valley native, studies climate science and works at the Utah Climate Center. Junior Bridger, also of Cache Valley, studies nutrition science. They led and funded this project through a student grant. Casey was alarmed by the ammonia data he was collecting at the Climate Center. “I immediately began to wonder how this issue would evolve over the coming decades.” The three teamed up to take a look at how Logan’s record-breaking amount of ammonia in our air is impacting those who breathe it. They looked at weather, ammonia level, and respiratory-related hospitalizations and found that more people were in the hospital with breathing problems during our worst air quality days. They also found that rain led to better air quality. This can help people with asthma to consider weather and air conditions as they plan outdoor activities. Connor is no stranger to public service, as his grandfather Gordon Snow was a majority whip for many years. He hopes to serve his community by going to med school, with a focus on rural medicine. Bridger also plans on med school. “Serving the people of Cache Valley and protecting their health is very important to me.

Climate Change Impacts on Atmospheric Ammonia and Implications for Human Health

According to national data Cache Valley has the highest concentrations of atmospheric ammonia in the nation. This study aims to answer the questions of whether climate variables and events such as precipitation, averaged winds, geopotential height, and teleconnections can be used to predict the behavior of pollutants and how human biology is potentially affected. Data from the Utah Climate Center shows that the 3rd yearly quartile has the highest levels of airborne ammonia due to the high levels of fertilizer use and livestock emissions in the farming industry in Cache Valley. After data analysis, there seems to be a connection between climate variables and atmospheric ammonia, specifically, precipitation appears to have the strongest (negative) correlation due to atmospheric scattering of particulates during precipitation events. In addition, according to data from Utah\u27s Public Health Data Resource there also seems to be a connection between peak ammonia season and occurrence of asthma incidences requiring a hospital visit. There is still much research to be done on the impacts of airborne ammonia on human health, but due to the limited resources available to our team we were only able to obtain data pertaining to asthma attacks, as more information becomes available we hope to incorporate it in our presentation.This research is especially significant to Cache Valley and the State of Utah at large due to its implications of climate and air quality prediction, and public health.https://digitalcommons.usu.edu/fsrs2021/1060/thumbnail.jp

The genetic basis for adaptation of model-designed syntrophic co-cultures.

Understanding the fundamental characteristics of microbial communities could have far reaching implications for human health and applied biotechnology. Despite this, much is still unknown regarding the genetic basis and evolutionary strategies underlying the formation of viable synthetic communities. By pairing auxotrophic mutants in co-culture, it has been demonstrated that viable nascent E. coli communities can be established where the mutant strains are metabolically coupled. A novel algorithm, OptAux, was constructed to design 61 unique multi-knockout E. coli auxotrophic strains that require significant metabolite uptake to grow. These predicted knockouts included a diverse set of novel non-specific auxotrophs that result from inhibition of major biosynthetic subsystems. Three OptAux predicted non-specific auxotrophic strains-with diverse metabolic deficiencies-were co-cultured with an L-histidine auxotroph and optimized via adaptive laboratory evolution (ALE). Time-course sequencing revealed the genetic changes employed by each strain to achieve higher community growth rates and provided insight into mechanisms for adapting to the syntrophic niche. A community model of metabolism and gene expression was utilized to predict the relative community composition and fundamental characteristics of the evolved communities. This work presents new insight into the genetic strategies underlying viable nascent community formation and a cutting-edge computational method to elucidate metabolic changes that empower the creation of cooperative communities

Accumulation of muscle ankyrin repeat protein transcript reveals local activation of primary myotube endcompartments during muscle morphogenesis

The characteristic shapes and positions of each individual body muscle are established during the process of muscle morphogenesis in response to patterning information from the surrounding mesenchyme. Throughout muscle morphogenesis, primary myotubes are arranged in small parallel bundles, each myotube spanning the forming muscles from end to end. This unique arrangement potentially assigns a crucial role to primary myotube end regions for muscle morphogenesis. We have cloned muscle ankyrin repeat protein (MARP) as a gene induced in adult rat skeletal muscle by denervation. MARP is the rodent homologue of human C-193 (Chu, W., D.K. Burns, R.A. Swerick, and D.H. Presky. 1995. J. Biol. Chem. 270:10236-10245) and is identical to rat cardiac ankyrin repeat protein. (Zou, Y., S. Evans, J. Chen, H.-C. Kuo, R.P. Harvey, and K.R. Chien. 1997. Development. 124:793-804). In denervated muscle fibers, MARP transcript accumulated in a unique perisynaptic pattern. MARP was also expressed in large blood vessels and in cardiac muscle, where it was further induced by cardiac hypertrophy. During embryonic development, MARP was expressed in forming skeletal muscle. In situ hybridization analysis in mouse embryos revealed that MARP transcript exclusively accumulates at the end regions of primary myotubes during muscle morphogenesis. This closely coincided with the expression of thrombospondin-4 in adjacent prospective tendon mesenchyme, suggesting that these two compartments may constitute a functional unit involved in muscle morphogenesis. Transfection experiments established that MARP protein accumulates in the nucleus and that the levels of both MARP mRNA and protein are controlled by rapid degradation mechanisms characteristic of regulatory early response genes. The results establish the existence of novel regulatory muscle fiber subcompartments associated with muscle morphogenesis and denervation and suggest that MARP may be a crucial nuclear cofactor in local signaling pathways from prospective tendon mesenchyme to forming muscle and from activated muscle interstitial cells to denervated muscle fibers