Using Stable Isotopes to Quantify Nitrogen Fates in Container Plants

Currently, in the agriculture field, it is not yet known the accurate amount of Nitrogen in fertilizer that plants take up. This statistic, known as the Nitrogen Use Efficiency is currently known to be within the 30-50% range (Lea-Cox and Ross, 2001). This is very important figure to know and it is a figure that can be improved, and therefore much time, energy, and resources can be saved. This research project will use concepts involving stable isotopes to examine red maple plant material and the soilless media that the plants were grown in. Three different isotope-labelled fertilizer treatments will be used to determine the amount of Nitrogen taken up in the plant, in the runoff water, and released to the atmosphere. Plant and media samples will be analyzed using a mass spectrometer and an accurate account of Nitrogen can then be made. The data show that the Nitrogen taken up by the plant mostly contributes to the growth of new plant material, although there are significant amounts of 15N in the old stem and old leaf samples. The conclusions that can be drawn are that Nitrogen that is processed into fertilizer is ultimately being wasted. Nitrogen is being leached into the ground water, immobilized by bacteria into organic Nitrogen, bound to the soil and media, and converted into NOx and N2; more research can be done, especially into the volatilization of the Nitrogen from fertilizers

Water Temperature and Harmful Algal Bloom Rate

Harmful algal blooms, made up of cyanobacteria, is an increasing problem in Midwestern lakes. Nitrogen and phosphorus fertilizers used in crops such as corn and soybeans run off into streams and eventually lakes. Nitrogen and phosphorus in the form of nitrate and phosphate respectively is then used by cyanobacteria as a food source, allowing them to bloom at an alarming rate. Massive bloom events can be hazardous to both human health and the natural environment because of the release of neurotoxins, hepatotoxins and others into the air and drinking water. We set out to find if different water temperature can affect the rate at which cyanobacteria can use nitrate. Six different species of cyanobacteria were analyzed. For each species, two solutions with known amounts of nitrate and excess phosphate were mixed, with one solution kept at 31 degrees Celsius and the other kept at room temperature. Overtime, the concentration of nitrate was measured. We found that, on average, the species kept at a higher temperature were able to use nitrate faster than their colder counterpart

Purdue AirSense: An Affordable Way to Measure and Study Air Pollution

Air pollution is a major health hazard worldwide, accounting for one-eighth of all deaths in 2012 (World Health Organization). Globally, there is a severe lack of ground-based spatiotemporal monitoring of gaseous and particulate air pollutants, particularly in Africa, South and Central America, and the Middle East. This is in great part due to the high costs of air quality instrumentation that meet accuracy and reliability criteria set by monitoring agencies. The air quality data that is available is often not presented to the public in a user-friendly manner. Taking advantage of recent developments in low-cost sensing technologies, an integrated sensor network based on the Raspberry Pi platform was modeled for \u3c1.5K/unit. Each module includes sensors for coarse and fine particulate matter (PM10, PM2.5, PM1), ozone, nitrogen oxides, and carbon monoxide. The sensors can stream data to a user-friendly website where students and the general public can analyze large air quality data sets. Calibration protocols are being developed to ensure reliability of sensors’ outputs. The observed benefits of an integrated set of low-cost sensors, compared to traditional air quality monitoring sites, are increased spatial coverage and a factor of 100 difference in cost. These innovations will make people’s lives better as we work towards reducing the adverse effects of air pollution through increased awareness and availability of open-source data among the central Indiana community

Purdue AirSense: An Open-source Air Quality Monitoring System

Ambient air pollutants have received increasing attention in recent years since studies have demonstrated their adverse health effects. To address the sparsity of concentration data for major ambient air pollutants, researchers have introduced several new low-cost measurement methods. Despite these efforts, only a few gas concentration data and aerosol size distribution data are publicly accessible through online platforms. In this study, we used Alphasense sensors to build an innovative low-cost portable sensor system that measures the concentration of ozone, CO, NOx, and coarse and fine particulate matter (PM). Alongside the portable sensor system, we assembled lab-grade analytical instruments in a central monitoring station to measure the background concentrations of ozone, CO, NOx, and PM (coarse, fine, and ultrafine) in the West Lafayette region and to validate the sensor system measurements. Data from the low-cost sensor module were retrieved and published on a web platform that was built to present major ambient pollutant data in a user-friendly manner for classroom use. Particularly, the Alphasense OPC-N2 sensor captured temporal variations of coarse- and fine-particle concentrations. Thus, the low-cost module, if massively distributed, could be used to assess local exposures; the central monitoring station could capture regional concentration trends in the longer term. Furthermore, the web platform could educate the public on air quality monitoring and promote citizen science

Combining multiple isotopes and metagenomic to delineate the role of tree canopy nitrification in European forests along nitrogen deposition and climate gradients

Forest canopies influence our climate through carbon, water and energy exchanges with the atmosphere. However, less investigated is whether and how tree canopies change the chemical composition of precipitation, with important implications on forest nutrient cycling. Recently, we provided for the first time isotopic evidence that biological nitrification in tree canopies was responsible for significant changes in the amount of nitrate from rainfall to throughfall across two UK forests at high nitrogen (N) deposition [1]. This finding strongly suggested that bacteria and/or Archaea species of the phyllosphere are responsible for transforming atmospheric N before it reaches the soil. Despite microbial epiphytes representing an important component of tree canopies, attention has been mostly directed to their role as pathogens, while we still do not know whether and how they affect nutrient cycling. Our study aims to 1) characterize microbial communities harboured in tree canopies for two of the most dominant species in Europe (Fagus sylvatica L. and Pinus sylvestris L.) using metagenomic techniques, 2) quantify the functional genes related to nitrification but also to denitrification and N fixation, and 3) estimate the contribution of NO3 derived from biological canopy nitrification vs. atmospheric NO3 input by using \u3b415N, \u3b418O and \u3b417O of NO3in forest water. We considered i) twelve sites included in the EU ICP long term intensive forest monitoring network, chosen along a climate and nitrogen deposition gradient, spanning from Fennoscandia to the Mediterranean and ii) a manipulation experiment where N mist treatments were carried out either to the soil or over tree canopies. We will present preliminary results regarding microbial diversity in the phyllosphere, water (rainfall and throughfall) and soil samples over the gradient. Furthermore, we will report differences between the two investigated tree species for the phyllosphere core microbiome in terms of relative abundance of bacterial and Archaea classes and those species related to N cycling. Finally we will assess whether there are differences among tree species and sites in the number of functional genes related to N cycling and how they are related to the N deposition and/or climate. [1] Guerrieri et al. 2015 Global Change and Biology 21 (12): 4613-4626

Significant contributions of combustion-related sources to ammonia emissions

Atmospheric ammonia (NH3) and ammonium (NH4+) can substantially influence air quality, ecosystems, and climate. NH3 volatilization from fertilizers and wastes (v-NH3) has long been assumed to be the primary NH3 source, but the contribution of combustion-related NH3 (c-NH3, mainly fossil fuels and biomass burning) remains unconstrained. Here, we collated nitrogen isotopes of atmospheric NH3 and NH4+ and established a robust method to differentiate v-NH3 and c-NH3. We found that the relative contribution of the c-NH3 in the total NH3 emissions reached up to 40 ± 21% (6.6 ± 3.4 Tg N yr−1), 49 ± 16% (2.8 ± 0.9 Tg N yr−1), and 44 ± 19% (2.8 ± 1.3 Tg N yr−1) in East Asia, North America, and Europe, respectively, though its fractions and amounts in these regions generally decreased over the past decades. Given its importance, c-NH3 emission should be considered in making emission inventories, dispersion modeling, mitigation strategies, budgeting deposition fluxes, and evaluating the ecological effects of atmospheric NH3 loading

Global patterns of nitrate isotope composition in rivers and adjacent aquifers reveal reactive nitrogen cascading

Remediation of nitrate pollution of Earth’s rivers and aquifers is hampered by cumulative biogeochemical processes and nitrogen sources. Isotopes (δ15N, δ18O) help unravel spatiotemporal nitrogen(N)-cycling of aquatic nitrate (NO3−). We synthesized nitrate isotope data (n = ~5200) for global rivers and shallow aquifers for common patterns and processes. Rivers had lower median NO3− (0.3 ± 0.2 mg L−1, n = 2902) compared to aquifers (5.5 ± 5.1 mg L−1, n = 2291) and slightly lower δ15N values (+7.1 ± 3.8‰, n = 2902 vs +7.7 ± 4.5‰, n = 2291), but were indistinguishable in δ18O (+2.3 ± 6.2‰, n = 2790 vs +2.3 ± 5.4‰, n = 2235). The isotope composition of NO3− was correlated with water temperature revealing enhanced N-cascading in warmer climates. Seasonal analyses revealed higher δ15N and δ18O values in wintertime, suggesting waste-related N-source signals are better preserved in the cold seasons. Isotopic assays of nitrate biogeochemical transformations are key to understanding nitrate pollution and to inform beneficial agricultural and land management strategies