Estimating Spatial and Temporal Variability of Nitrate Contamination in the United States
Dalton Everhardt
Author
07/26/2021
Added
25
Plays
Description
This is a video poster presentation of the work we have been doing over the summer where we have calculated a value called the Net Anthropogenic Nitrogen Input for every county in the continental United States. The resulting data was then visualized and analyzed.
Searchable Transcript
Toggle between list and paragraph view.
- [00:00:00.540]Hello! My name is Dalton Everhart
- [00:00:02.910]and this summer I have been working with my graduate advisor, Chuyang Liu,
- [00:00:06.960]and my faculty advisor, Dr.
- [00:00:08.730]Yusong Li on a project titled "Estimating Spatial and Temporal
- [00:00:13.260]Variability of Nitrate Contamination in the United States."
- [00:00:17.040]This short video poster presentation will give an overview of the work that
- [00:00:20.400]we've been doing and the results that we have obtained. But before that,
- [00:00:24.930]I would like to give a little information about the project that I think is
- [00:00:28.200]necessary for you to know. Nitrate is a naturally occurring inorganic
- [00:00:32.910]compound and is often created through a process called nitrification
- [00:00:37.230]where ammonia, which is created by natural sources of nitrogen,
- [00:00:41.370]is oxidized to nitrite and nitrate.
- [00:00:44.730]The United States Environmental Protection Agency has a Maximum Contaminant
- [00:00:48.990]Level or MCL for nitrate in drinking water as 10 milligrams
- [00:00:53.790]per liter as nitrogen. This 10 milligrams per liter
- [00:00:57.690]as nitrogen MCL is put in place to help protect people from the negative impacts
- [00:01:02.370]that exposure to too much nitrate in drinking water can have. Short-term
- [00:01:07.350]exposure can result in methemoglobinemia or blue
- [00:01:12.300]baby syndrome in infants,
- [00:01:13.770]as well as indigestion and anybody above six months or older.
- [00:01:18.360]Long-term exposure to nitrate levels above the MCL have been linked to a
- [00:01:22.920]variety of conditions, including sudden infant death syndrome,
- [00:01:27.030]depression and various cancers. Unfortunately,
- [00:01:30.690]a study conducted by the United States Geological Survey in 2006,
- [00:01:34.950]found that over 1 million private well owners live in areas with the risk of
- [00:01:39.330]exceeding the EPA's MCL for nitrate.
- [00:01:43.570]I also think it's notable to mention that while nitrate is naturally occurring,
- [00:01:47.340]levels above one milligram per liter
- [00:01:49.440]as nitrogen in groundwater is known to suggest human activity in the area
- [00:01:54.630]and that has helped shape our project to only look at sources of nitrogen that
- [00:01:58.260]only exists because of humanity. In this study,
- [00:02:02.130]our aim was to implement the most updated version of a toolbox developed by Hong
- [00:02:06.880]at all.
- [00:02:07.440]In their 2011 paper titled a toolbox for calculating net anthropogenic
- [00:02:12.420]nitrogen inputs, or NANI, to the continental United States at
- [00:02:17.340]the county level, as
- [00:02:19.410]NANI is known to be a predictor of nitrate pollution and, then to visualize and
- [00:02:24.120]analyze the resulting data to find anything of interest or worthy of note.
- [00:02:31.360]Basically, the NANI is a single value reported in kilograms of
- [00:02:35.920]nitrogen per square kilometers per year,
- [00:02:38.500]that takes into account all sources and sinks of anthropogenic nitrogen for a
- [00:02:42.610]particular area, or in our case, a county,
- [00:02:46.240]and is known to be linked with nitrate pollution.
- [00:02:49.060]The NANI is made up of four components:
- [00:02:52.510]Atmospheric Nitrogen Deposition, Fertilizer Nitrogen Application,
- [00:02:56.740]Agricultural Nitrogen Fixation,
- [00:02:58.990]and Net Food and Feed Imports with Net Food and Feed Imports being
- [00:03:03.880]further made up of four more components: Crop Nitrogen Production,
- [00:03:07.900]Animal Nitrogen Production, Animal Nitrogen Consumption,
- [00:03:11.410]and Human Nitrogen Consumption.
- [00:03:13.690]Riverine Nitrogen Export is not used to calculate the NANI,
- [00:03:17.500]but it's included in the diagram because there is a known empirical relationship
- [00:03:21.730]between the two with Riverine Nitrogen Export being equal to
- [00:03:26.110]approximately 30% of the NANI.
- [00:03:29.260]It's also important to note that it's entirely possible for the NANI to
- [00:03:33.190]be negative.
- [00:03:35.520]Moving on to our methodology, since this study is using a standardized toolbox
- [00:03:39.900]developed by another party,
- [00:03:41.520]the calculation of the NANI is a simple process.
- [00:03:45.030]The only input needed from us was an ArcGIS shapefile of the continental
- [00:03:49.140]United States that contains all county boundaries.
- [00:03:52.350]The input is then cross-referenced with the shapefile provided in the toolbox
- [00:03:56.190]so that locations outside of our area of interest or areas not included in the
- [00:04:00.930]toolbox scope were removed.
- [00:04:03.150]The NANI extraction tools are then used to
- [00:04:07.850]attribute publicly available data to each county
- [00:04:11.070]and then the extraction tools process the data.
- [00:04:15.150]After that, the NANI accounting tool is used to calculate the components of
- [00:04:19.810]NANI, and then the NANI itself. In its current iteration,
- [00:04:24.750]the toolbox creates a table of values where a NANI is reported for each
- [00:04:29.490]area. And for the following years:
- [00:04:32.310]1987, 1992, 1997,
- [00:04:36.540]2002,
- [00:04:37.920]2007 and 2012. From there,
- [00:04:41.760]it was up to us to visualize and analyze the data and the best way to
- [00:04:46.710]visualize most spatial data as a map,
- [00:04:49.560]but since our results also have a time component to them,
- [00:04:52.800]we decided that for a virtual poster,
- [00:04:54.780]that a GIF of our maps was an interesting format to visualize our data.
- [00:04:59.580]By watching the GIF as it loops,
- [00:05:01.680]there are a ton of interesting things that can be seen,
- [00:05:04.020]and it's a really useful tool to help see what is going on with the NANI
- [00:05:08.760]over time in particular places.
- [00:05:11.640]Unfortunately due to the large scope of our data and the limited space available
- [00:05:16.470]on our poster, only a few tidbits from our data analysis can be shown.
- [00:05:21.660]The first thing that we thought was interesting to look at was just the national
- [00:05:24.840]average of the NANI over our timeframe.
- [00:05:28.380]As you can see in figure four, from 1987 to 2012
- [00:05:32.190]the national average at the, NANI increased by 25% from
- [00:05:36.870]2849.49 kilograms of nitrogen per square
- [00:05:41.280]kilometers per year to 3569.29 kilograms of
- [00:05:46.110]nitrogen per square kilometers per year,
- [00:05:48.830]which is an extremely concerning statistic
- [00:05:50.850]when you think of the negative health effects of nitrate in our drinking water
- [00:05:54.900]that I listed before. Table one shows the top five
- [00:05:59.780]counties with the highest NANI for 2012
- [00:06:04.210]and an unexpected result from this is that all five of these counties are cities
- [00:06:08.990]two which being a part of New York city and three having quite small areas.
- [00:06:14.150]Further analysis needs to occur.
- [00:06:16.160]But considering that area is a factor of calculating the NANI,
- [00:06:20.540]extremely small areas may artificially increase the NANI.
- [00:06:26.010]The last thing that we wanted to cover in this presentation is to give a few
- [00:06:29.520]specifics about a particular hotspot that can be seen from our GIF of our series
- [00:06:34.320]of maps. Over time we see a general increase of the NANI,
- [00:06:39.120]and a series of seven counties that make up the San Joaquin valley in
- [00:06:43.020]California.
- [00:06:45.600]The San Joaquin Valley is well known for its booming agricultural industry,
- [00:06:49.500]as well as its issues with nitrate and its groundwater. In fact,
- [00:06:54.210]in 2007,
- [00:06:55.230]74% of all California's nitrate violations could be found
- [00:06:59.880]in the San Joaquin Valley. In that same year,
- [00:07:02.670]four of the valley seven counties could be found in a list of the top 100
- [00:07:07.620]counties with the highest NANI
- [00:07:09.750]in the continental United States with Merced county placing the highest from
- [00:07:14.160]the four San Joaquin valley counties at 36th.
- [00:07:20.810]To summarize, the NANI is already known to be a predictor of how much
- [00:07:24.650]nitrate pollution occurs in a particular area and a 25%
- [00:07:29.900]increase in the national average has incurred from 1987 to
- [00:07:34.430]2009 and is a point of concern.
- [00:07:37.700]We have also seen that while cities with small areas or high populations,
- [00:07:42.590]dominate our top five of the NANI
- [00:07:46.010]we have also observed that areas with high amounts of agriculture can also
- [00:07:49.730]place very highly in the NANI scores,
- [00:07:54.260]such as the San Joaquin valley. Unfortunately,
- [00:07:58.010]while I discussed in the introduction
- [00:07:59.810]what happens when nitrate gets into our drinking water and how private well
- [00:08:04.070]owners are at risk,
- [00:08:06.050]a limitation of this study is that the NANI does not give an estimate of how much
- [00:08:10.460]nitrate infiltrates into groundwater.
- [00:08:13.040]It's only known to be an estimation of nitrate in a watershed and have that
- [00:08:17.210]empirical relationship with the Riverine Nitrogen Exports that I mentioned before.
- [00:08:22.940]Going forward future work with this dataset not only includes further analysis
- [00:08:27.590]of all of this vast amount of data,
- [00:08:30.170]but this data is currently planned on being used by my graduate advisor,
- [00:08:33.410]Chuyang Liu,
- [00:08:34.640]as a small part of his work in developing a method to accurately
- [00:08:39.140]predict groundwater nitrate.
- [00:08:41.480]Thank you for listening to our presentation and I hope you enjoy the rest of
- [00:08:44.420]your day.
The screen size you are trying to search captions on is too small!
You can always jump over to MediaHub and check it out there.
Log in to post comments
Embed
Copy the following code into your page
HTML
<!-- To force a 16x9 aspect ratio use 'padding-top: 56.25%;' instead of 'padding-top: 75%;' -->
<div style="padding-top: 75%; overflow: hidden; position:relative; -webkit-box-flex: 1; flex-grow: 1;">
<iframe
style="bottom: 0; left: 0; position: absolute; right: 0; top: 0; border: 0; height: 100%; width: 100%;"
src="https://mediahub.unl.edu/media/17379?format=iframe&autoplay=0"
title="Video Player: Estimating Spatial and Temporal Variability of Nitrate Contamination in the United States"
allowfullscreen
></iframe>
</div>
Comments
0 Comments