Progress 09/01/18 to 08/31/21

Outputs
Target Audience:We are continually reaching a target audience of scientists and researchers in the soil and atmospheric research community. We have received multiple inquiries reagrding when the system will be on the market. Further, because the system is modular, we have intense interest in the individual ovenand ozone reactor modules, particularly when attached to a CAPS NO2. To continue to get the word out about our new capabilities, we have been attending scientific meetings (AGU and EGU annual meetings), as well as a Soil Science Society of America meeting last November. We will continue this thorugh 2022. Changes/Problems:Two complications arose during this project that led to the request (and approval) for a 1-year no-cost extension. First, the COVID pandemic effectively shut down Aerodyne for 3 months, during a period when there would have been rapid development for this project. In addition, 6 months after the shutdown, Aerodyne is less than half operational (as per MA state orders), furtherhindering development. Second, there has been a staffing change at Aerodyne, and a new engineer is leading the oven development. This engineer has a background in physics, making him especially well suited for this application, but it took time to get him up to speed. What opportunities for training and professional development has the project provided?Aerodyne has an engineer dedicated to simulating the thermal design using computational fluid dynamics software. They have trained on this software, and interfaced it with our existing CAD package. This new skill set will be useful for future R&D at Aerodyne. The engineer is already using it to model our Aerodyne Inertial Inlet. This project has also given a new postdoctoral asociate an opportunity to learn more about oven and flast flow dynamics as she is just getting started. How have the results been disseminated to communities of interest?We attended the 2019 AGU Fall Meeting, the 2020 EGU, the 2021 AGU, and 2021 SSSA meetigns. At these events we have discussed many aspects of this USDA Project, including the instrument capabilities, the flux measurement details, and the ability to thermally convert nitrogen species to NO. We have multiple potential customers showing interest (asking when it will be available as a commerical product). What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Measurement capabilities that can directly quantify nitrogen deposition (and its components) without estimation would greatly improve the accuracy of these efforts. The overall goal of this research program is to develop the ability to simultaneously quantify Nr using a total reactive atmospheric nitrogen converter (TRANC), NH3 using an Aerodyne Inertial Inlet, and NOx using a novel oxidation package, with high precision and time response, for use in studying the impacts of nitrogen deposition on ecological health and soil fertility. The system integrates two novel sampling schemes with a precise, fast response laser instrument capable of simultaneously measuring fluxes of ammonia, NOx , and total reactive nitrogen. The possible utility of such a system is profound: quantification of atmospheric nitrogen deposition with attribution of its source based upon its chemical constituents could significantly inform soil management decisions and environmental policy. Task 1. We have successfully developed a field-ready, TRANC oven which we deployed in Task 5. Briefly, the inlet sample passes through an inlet screen and into the tip of the oven. The oven tube coils around the center inlet core, and is maintained at >900 C. The samples then leave the heater region, entering a heat shedding zone, and is then passed into the second stage, where it reacts with CO over an Au catalyst for final conversion of Nr to NO. Because of the importance of understanding the heat and gas flow in this design, we dedicated significant effort to developing the ability to use computational fluid dynamics software (in this case, the CFD package associated with AutoDesk). This capability allowed us to rapidly iterate through design details of the oven to converge on a system that we understand thoroughly. Task 2. During Task 2 we successfully developed a fieldable ozone generator package. The ozone generator produces 10's of ppm O3 using air as its initial source. The generator is based upon the Aerodyne PAM reactor, and consists of an ozone lamp at 254 and 193 nm embedded in an anodized aluminum enclosurethrough which ambient, dried air is passed at 10-1000 sccm. The lamp is controlled by a ballast that is adjustable, allowing its output to be modulated for control of the O3 concentration. The generator output is then monitored using an OEM ozone monitor from 2B Tech. Importantly, the ozone concentrations (4-10 ppm) that need to be generated for the NO oxidation reactor are readily achievable using this system. The output is so stable that in future iterations we will not use an ozone monitor to continuously monitor, but rather calibrate the lamp once and keep it fixed. Overall, this is the Aerodyne Ozone Package performed well, and we anticipate it can be used with more than a TILDAS. While in Phase I we demonstrated the ability to use the oxidation package with a TILDAS, during Phase II we were able to extend this to another NO2 measurement, the Aerodyne CAPS NO2 instrument. While this is the topic of another research program, we note that this approach appears to work extremely well for that instrument. Task 3. This task had multiple subtasks, the first of which is continued modification and refinement of the compact dual (CD) TILDAS. The full dual-laser instrument that was originally designed was working quite well during the whole project. Rather than simply build out a CD TILDAS with the correct lasers, we therefore decided to focus efforts on improving the optical design for future commercialization, while continuing to use the full-size dual TILDAS for lab and field testing. Optics On the optics side, there was major progress, with improvements listed below: Updated XY stage design for smoother adjustment motion and improved assembly. Worked out no-more-tears (NMT) optical alignment design with minimal changes between 36 m and 76 m cells. One optic change Two optical position changes Minor adjustments elsewhere Left room for refence path matching cell. This will be added later. CD cell design was used to consolidate cell variety. Minimized dead volumes so that only change for low volume is mirror and insert changes. This also reduced the volume of the 36 m ULV cell even more. Now 120 ml port to port. Developed low volume insert design for 76 m cell. Needs to be prototyped Computing In Phase II we extensively tested the Intel NUC computing package for both TILDAS control, as well as analysis. It has been deployed aboard a N2O flux instrument in a high-temperature environment (40 C) without issue. We also tested a low-power, fanless version in the lab and in the field. It appeared to work quite well, and will be deployed in future. Eddy Covariance Software In addition, we have developed an eddy flux software that will be integral to the TILDAS instrument, allowing a customer to quickly, convert the observed mixing ratios of Nr, NOx, and NH3 to fluxes on-the-fly. This developed code is run in Igor (WaveMetrics), allowing for it to interface cleanly with other Igor-based TILDAS routines that Aerodyne has developed recently. This code performs all standard eddy covariance calculations, including water corrections, anemometer tilt corrections, and time lag determination. Task 4. Laboratory experiments were performed to test the safety of the TRANC oven. This included measurements of time to reach 950C setpoint and time to cool when heater is turned off; temperature measurements of the external TRANC shell during normal operation with an oven temperature of 950C; and quantifying any temperature rise at the shell during simulated power failure. These experiments were to ensure that during normal operation or during a power failure in the field, there were no safety concerns. It was critical before deploying the system in the field, that we were confident that the oven operated safely and would not be a possible fire hazard. If the external shell, for example, got very hot, it would not only be dangerous to someone if they touched it, but if leaves, grass, etc. landed on the surface it could possibly ignite. These scenarios had to be avoided. Thus, we ran tests where the oven was heated to 950C internally, and we measured the external temperature was measured using an FLIR camera. With internal T of 950C, the outside body of the oven reached a maximum temperature of 29C. There are several nuts on the shell that are necessary as they are part of the internal structure of the oven, and thus have thermal connection to the oven. These reached a maximum temperature of only 39C. Task 5. The TRANC system including TILDAS were deployed to an agricultural field site in central Massachusetts from August 19 - November 1, 2021. We deployed an eddy covariance tower with the TRANC and TILDAS at the University of Massachusetts Crop and Animal Research and Education Center in South Deerfield.We were given access to sufficient power (2 20A circuits) to fully power the TILDAS in a weatherproof, temperature-controlled enclosure, the vacuum pump, the TRANC oven, and all additional electronics. Two 250 foot long extension cords were run from the power source (circuit breakers located by road, close to the greenhouse) to our measurement site. An internet hub was set up to allow us to have remote access to the instrument. Overall, this first field deployment of the TRANC system was extremely successful. Once we worked through some initial issues with the oven and a lamp failure in the ozone generator, we were able to collect 10 Hz eddy flux data for approximately a month. The system ran reliably without need for on-site visits. The TRANC oven and the NOx converter displayed excellent stability. There were a couple of power glitches or brief power outages at the field site, but we were able to restart the TILDAS system remotely. The TRANC system including oven and ozone generator restarted automatically upon power restoration.

Publications

Progress 09/01/19 to 08/31/20

Outputs
Target Audience:We are continually reaching a target audience of scientists and researchers in the soil and atmospheric research community. In fact, we have already received multiple inquiries reagrding when the system will be on the market. To continue to get the word out about our new capabilities, we are attending scientific meetings (AGU and EGU annual meetings), as well as a Soil Science Society of America meeting in November. Changes/Problems:Two complications have arisen that have led to the request (and approval) for a 1-year no-cost extension. First, the COVID pandemic effectively shut down Aerodyne for 3 months, during a period when there would have been rapid development for this project. In addition, 6 months after the shutdown, Aerodyne is less than half operational (as per MA state orders), further hindering development. Second, there has been a staffing change at Aerodyne, and a new engineer is leading the oven development. This engineer has a background in phsyics, making him especiually well suited for this application, but it has taken time to get him up to speed. Despite these difficulties, we are making progress (as described in achievements). We have been further modeling the reactor oven and are now building it, and have been working on the oxidation package. While the future of the COVID pandemic is difficult to predict, we expect the 1-year NCE provides the necessary time to successfully bring the product to a commercial stage. What opportunities for training and professional development has the project provided?Aerodyne has a new engineer that is dedicated to furthering the thermal design using computational fluid dynamics software. They have been training on how to use this software, and interface it with our existing CAD package. This new skill set will be useful for future R&D at Aerodyne. The engineer is already using it to model our Aerodyne Inertial Inlet. How have the results been disseminated to communities of interest?We have attended the 2019 AGU Fall Meeting, and the 2020 EGU meeting during this reporting period. At these events we have discussed many aspects of thisUSDA Project, including the instrument capabilities, the flux measurement details, and the ability to thermally convert nitrogen species to NO. We have multiple potential customers showing interest (asking when it will be available as a commerical product). What do you plan to do during the next reporting period to accomplish the goals?As described above, our next steps are to build and test the prototype oven (benchmarking against the CFD software), and modify the design as needed. Emphasis will be placed on safe operation, ensuring that there are no scenarios where the oven is in an unsafe state or too hot to touch. We will also be operating further exploring the CAPS-NOx system (CAPS NO2 coupled to the oxidation package) to further its commercialization. Finally, we will be deploying the instrument to a local farm, and likely Duke Forest (or other ecological site) for in-field testing. For commercialization, the Aerodyne engineering team is developing ways in which to reducing building costs, and we are continuing to attend scientific meetings (currently virtual) to disseminate the TRANC system capabilities. We expect to have a sales-ready system wihtin 18 months.

Impacts
What was accomplished under these goals? Measurement capabilities that can directly quantify nitrogen deposition (and its components) without estimation would greatly improve the accuracy of these efforts. The overall goal of this research program is to develop the ability to simultaneously quantify Nrusing a total reactive atmospheric nitrogen converter (TRANC), NH3using an Aerodyne Inertial Inlet, and NOxusing a novel oxidation package, with high precision and time response, for use in studying the impacts of nitrogen deposition on ecological health and soil fertility. The system integrates two novel sampling schemes with a precise, fast response laser instrument capable of simultaneously measuring fluxes of ammonia, NOx, and total reactive nitrogen. The possible utility of such a system is profound: quantification of atmospheric nitrogen deposition with attribution of its source based upon its chemical constituents could significantly inform soil management decisions and environmental policy. Overall, the COVID outbreak, along with changes in engineering staffing, have slowed progress. However, as Aerodyne (and Massachusetts) slowly reopens, we are aggressively continuing development. Nonetheless, we have requested (and been approved for) a 1-year no-cost extension of this project. This extension allows us to continue this development, with plans for field deployments in the Spring/Summer 2021. Task 1. Develop a Field-Ready Oven Package During this reporting period we have continued to develop the reactor oven design, and are now in the process of building the prototype. Briefly, the inlet sample passes through an inlet screen and into the tip of the oven. The oven tube coils around the center inlet core, and is maintained at >900 C. The samples then passes through a heat shedding zone, and is then passed into the second stage, where it reacts with CO over an Au catalyst for final conversion of Nrto NO. This development has been aided greatly by computational fluid dynamics simulations that allow us to achieve the optimal reaction temperature while ensuring safe operation for a user and environment. The latest design, which is being built, uses combinations of insulation and air flow to isolate the >900 C oven from the rest from the secondary Au reactor and the exhaust. Using current simulations, the insulation maintains the outer surface of the oven enclosure to be <50 C, which ensures no risk of burning of catching fire. A central concern with these ovens is not just the thermal constraint when in operation, but also making sure the oven temperature stays safe in the event of a power outage, when cooling fans stop. Based upon CFD simulations, a complete shutdown of the oven and air circulation will result in a <100 C surface temperature that will rapidly cool off. To further mitigate this, we are including screen around the oven such that even during shutdown the outer surface (screen) is <<100 C. In addition to these safety measures, we will be attaching mechanical thermal interlock switches (e.g. klaxon) in multiple places on the surface of the oven that will shut off the oven if the temperature exceeds a pre-set value. Over the next two months, these components and safety measures will be strenuously tested in the laboratory and Aerodyne parking lot. Task 2. Develop a Field-Ready Oxidation Package The oxidation package is designed around the idea that a small, very clean ozone generator could be placed at the inlet of a variety of Aerodyne instruments (including the TILDAS that is being used for this project), and allow for observation of oxidation products. Of importance here is the O3+NOàNO2 reaction, and the fact that the subsequent NO2+O3àNO3 reaction is extremely slow. Based upon this, a few-second reaction time between NO and 2-5 parts per million O3 will convert >98% of the NO to NO2. Because the subsequent reaction is slow, the measurement of NO2 from a real-world sample that contains NO and NO2 will reflect total NOx, which is of relevance for understanding the impact of agriculture upon air quality. This NO2 measurement can be achieved using a TILDAS instrument, or using a CAPS NO2 (cavity-attenuated phase shift spectroscopy) The ozone package prototype that we have developed is a 1U rack-mounted box, with precise flow control of the ozone, which is injected into the inlet line at high concentrations, and diluted to 2-5 ppm. The generator itself is an ozone lamp at 254 and 193 nm. We are currently monitoring the O3 using a 2BTech monitor, but are considering building our own low-cost UV photometer. The combination of the CAPS and oxidation package has been tested in the laboratory on a smog chamber, with other traceable NO and NO2 instruments, revealing excellent agreement. It is currently being tested in a mobile platform (the Aerodyne Mobile Laboratory) in urban settings. Task 3. Integrate Dual-Inlet System with Compact Dual-TILDAS The Compact Dual-TILDAS is still having final design details worked out by the Aerodyne engineering team, but we expect to be building within the next few months. One of the important aspects of this design is a reduced-volume absorption cell design. In addition to minimizing dead space, we have developed a 3-D printed insert that closely surrounds the multipass beam pattern. We estimate that we can reduce the volume of the cell by ~40% using this insert. This will allow us to operate the instrument at a lower flow, while ensuring fast response time, as critical requirement of the intended eddy covariance application. Computing power During this reporting period we have extensively tested the Intel NUC computing package for both TILDAS control, as well as analysis. It has been deployed aboard a N2O flux instrument in a high-temperature environment (40 C) without issue. We have found dramatic improvements in temporal response by going to the higher-speed NUC platform. In addition, we have been extensively working on an eddy flux software that will be integral to the TILDAS instrument, allowing a customer to quickly, and converts the observed mixing ratios of Nr, NOx, and NH3 to fluxes on-the-fly. This code is developed and will be run in the Igor (WaveMetrics), allowing for it to interface cleanly with other Igor-based TILDAS routines that Aerodyne has developed recently. This code performs all standard eddy covariance calculations, including water corrections, anemometer tilt corrections, and time lag determination. Task 4. Laboratory Testing of Integrated Measurement System We have now extensively tested the LabJack™ A/D acquisition card, and find it to be sufficient for logging anemometer data, thermocouple readout, and any flow meters that are in line. We have also started using the CFD software to simulate the Aerodyne Inertial Inlet particle separator, which is central to NH3 flux measurements. The inlet is based upon a virtual impactor, where a fast, low-pressure (~100 Torr) flow is required to turn 180 degrees to go toward the TILDAS. Particles >300 nm are generally unable to turn with enough clearance due to inertia, and instead are drawn out of the flow. The CFD simulations currently being run are successfully demonstrating the ability to simulate the physics behind this inertial separation. We will capitalize upon this ability to improve the inertial inlet design to for lower inlet flows (<10 SLPM), and smaller size. Task 5. Field Deployment of Integrated Measurement System We are planning to deploy the reactive nitrogen system to two locations in spring and summer 2021. We are in discussions with a local organic farm near the Boston area to ideally deploy during spring fertilization, when reactive nitrogen emissions could be greatest. Second, we are looking to collaborate with Dr. John Walker (EPA) for deployment of the system to Duke Forest, where we will explore the interface between urban outflow (from the east) and an agricultural production (to the west).

Publications

Progress 09/01/18 to 08/31/19

Outputs
Target Audience:During this period our efforts successfully reached a target audience of scientists and researchers in the soil and atmospheric research community. We have two presentations, one at the American Geophysical Union Fall Meeting 2018, and one at the European Geophysical Union Meeting in April 2019. In both cases there was intense interest. In fact, we have already received multiple inquiries reagrding when the system will be on the market. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project thus far has provided the affiliated research scientists with new experience in thermal design and flow dynamics. This new skill set will be useful for future R&D at Aerodyne. How have the results been disseminated to communities of interest?The results have been disseminated via conference proceedings (see Products section), and personal interactions with relevant scientists. What do you plan to do during the next reporting period to accomplish the goals?Next steps Over the next several months, we will focus efforts in two places. First, we will focus on building the TRANC oven prototype in the lab and iteratively designing with the aid of the computational fluid dynamics calculations. We expect this activity to accelerate over the next two months and have the first prototype in 3 months. Second, we will continue efforts to finalize the compact dual TILDAS configuration and build the instrument over the next 6 months. In the intervening time, we will also be testing the oxidation package to assess its applicability for the CAPS instrument and develop a second enclosure design for the package. We will also be laboratory testing the oxidation package with the TILDAS to reproduce the Phase I success and have the system prepared for eventual integration in Task 4.

Impacts
What was accomplished under these goals? The need to quantify reactive nitrogen compounds in the atmosphere is becoming increasingly important. Reactive nitrogen compounds (Nr), here defined as all nitrogen compounds other than N2and N2O, have risen dramatically in the past 100 years. Nrcreation in the late 1800's was 20 Tg N/yr. With increased burning of fossil fuels and the development of the Haber-Bosch process for ammonia production in the early 1900s, Nrproduction has increased to over 150 Tg N/yr. Emissions of Nrcan return to the soil or water within hours to days, contributing nitrogen to local ecosystems. The impact of Nrairborne emissions can be felt not only at the source location, but at considerable distances away. As a case in point, nitrogen deposition in Rocky Mountain National Park is estimated to be a factor of 20 greater than "natural" levels, leading to ecological imbalances in plant life. Concentrated animal feeding operations (CAFOs) and farming are implicated as major contributors to this enhancement, as is urban outflow from east of the Colorado Front Range, during atmospheric "upslope" events (wind from the east). Quantifying this Nrexchange between the atmosphere and ecosystem is crucial to our understanding of the impact of anthropogenic Nrupon the biosphere, and to maintaining nitrogen balance for future crop productivity. Measurement capabilities that can directly quantify nitrogen deposition (and its components) without estimation would greatly improve the accuracy of these efforts. The overall goal of this research program is to develop the ability to simultaneously quantify Nrusing a total reactive atmospheric nitrogen converter (TRANC), NH3using an Aerodyne Inertial Inlet, and NOxusing a novel oxidation package, with high precision and time response, for use in studying the impacts of nitrogen deposition on ecological health and soil fertility. The system integrates two novel sampling schemes with a precise, fast response laser instrument capable of simultaneously measuring fluxes of ammonia, NOx, and total reactive nitrogen. The possible utility of such a system is profound: quantification of atmospheric nitrogen deposition with attribution of its source based upon its chemical constituents could significantly inform soil management decisions and environmental policy. Task 1. Develop a Field-Ready Oven Package During this reporting period, we have developed a design for a field-ready, safe TRANC oven. Briefly, the inlet sample passes through an inlet screen and into the tip of the oven. The oven tube coils around the center inlet core, and is maintained at >900 C. The samples then passes through a heat shedding zone, and is then passed into the second stage, where it reacts with CO over an Au catalyst for final conversion of Nrto NO. It is important to isolate that oven to avoid contacting any external bulk materials. A screen will allow a high flow of gas to pass into the inlet tip area (for fast time response), while stopping flying debris such as leaves. The flow of sample into the inlet area will be maintained by a fan or pump. The inlet area flow will maintain the temperature of the second stage of the reactor, controlled by a valve that will divert flow either into the space around second stage or bypass it. The heat that is remaining will be exhausted away from the inlet. The length of the warm-but-not-hot region in the at reactor tip will be minimized by loading the tip with a dedicated heater coil that will keep the tip temperature at >900 C. Because of the importance of understanding the heat and gas flow in this design, we have dedicated significant effort this first year to developing the ability to use computational fluid dynamics software (in this case, the CFD package associated with AutoDesk) prior to building the oven. Task 2. Develop a Field-Ready Oxidation Package We have built an ozone oxidation package that produces 10's of ppm O3using air as its source. It uses an ozone lamp at 254 and 193 nm in an enclosure through which air is passed at 10-1000 sccm. The lamp is controlled by a ballast that is adjustable, allowing modulation of the O3concentration. The generator output is monitored using an OEM ozone monitor from 2BTech. We tested the generator output over a 2-month period. After an initial fall over the first two weeks, the output was stable. The ozone concentrations (4-10 ppm) needed for the NO oxidation reactor are readily achievable. Although during tests to date we have used dry air as the source flow for the reactor, we have identified a miniature pump to drive the flow of this reactor in field applications. We will test the ability of the system to operate using humidified air. During Phase II we want to extend this to the Aerodyne CAPS NO2instrument. The CAPS instrument is designed for operation at 455 nm. At this wavelength 5 ppm of ozone would appear on the CAPS as ~2.5 ppb of NO2 due to spectral cross-talk. We have modified the CAPS NO2instrument to operate at 405 nm where 5 ppm of ozone would only yield 0.12 ppb of crosstalk. Task 3. Integrate Dual-Inlet System with Compact Dual-TILDAS The goal of these efforts is to improve performance and manufacturability while reducing cost. The electronics are having the SPI protocol integrated throughout the instrument. Most of this integration work is completed and we have hardware in hand which will be tested over the course of the next few months. The dual laser current driver assembly has also been designed. The sample cell and the laser combining optics are complete, and a basic table and cover system is designed, while work is needed on the laser collection optics and the beam shaping and steering optics. The shaping and steering optics need to be hardened in a similar manner to the laser combining optics and interfaced to the table. The collection optics design needs to be revisited for manufacturability. We are also modifying the design of the multipass cell in order to improve time response. To achieve this, we have 3-D printed a cell body that can maintain the needed vacuum levels for this application. As the testing and final design decisions are being made for this version of the compact dual instrument, it will be available for laboratory and field testing of the sampling components of the overall system (oxidation package and TRANC reactor). Computing power For operation at 10 Hz, we are testing other computing platforms, specifically the Intel Next Unit of Computing (NUC). The NUC's have more memory and a faster processor in a similar form factor. We have tested a NUC on an instrument that has been operating continuously for >9 months without a problem. Because of this success, we will be using this model for the compact dual instrument. Task 4. Laboratory Testing of Integrated Measurement System As the integrated measurement system is still being assembled, we have not tested the system. We have started testing schemes to monitor carbon monoxide, temperatures and flows throughout the system.We have purchased and tested small Honeywell flow meters. Initial tests show that the the meter can run continuously for at least 1 month without data dropouts. We have also tested analog to digital recording systems, and found that the LabJack™ is an excellent platform to record dozens of analog inputs. Finally, the computational fluid dynamics package discussed in the Task 1 results has shown to be able to also model particulate flow, which is especially important to the Aerodyne Inertial Inlet. CFD simulations are currently being started for this product. Task 5. Field Deployment of Integrated Measurement System We are now beginning discussions with a local farm to deploy the compiled system in late spring 2020. We will use the Miniature Aerodyne Mobile Laboratory (minAML) for this deployment. In addition, we are starting discussions with Dr. John Walker regarding a deployment of the system in summer 2020 to Duke Forest, in Chapel Hill, NC.

Publications

• Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: An Eddy Covariance System For Simultaneous Flux Measurements Of Total Reactive Nitrogen, Ammonia, And Nitrogen Oxides. JH Shorter, JR Roscioli. AGU Fall Meeting Abstracts, 2018
• Type: Conference Papers and Presentations Status: Other Year Published: 2019 Citation: An Eddy Covariance System For Simultaneous Flux Measurements Of Total Reactive Nitrogen, Ammonia, And Nitrogen Oxides. JH Shorter, JR Roscioli. EGU Abstracts, 2019
• Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: An eddy covariance system for simultaneous flux measurements of total reactive nitrogen, ammonia, and nitrogen oxides (NOx). Shorter Joanne, Integrated Carbon Observation System Science Conference, Sept. 2018