The Swamp Stomp

Volume 16, Issue 17

A few months ago, I was observing one of the Swamp School’s wetland delineation training courses in the field.   I was interested in some of the techniques that the students were using to collect data.  I watched several of them taking measurements and then entering those values into the data form.  Those values were then used calculate the prevalence index and dominance test and to evaluate hydrology and soil indicators.     All these measurements were then used to determine if the assessed area was considered a wetland.  The Army Corp of engineers would review the area at a later time and determine if these measurements were done correctly and if the assessment was accurate.

The first student I observed was reviewing the vegetation section of the data form.  She was determining the absolute percent cover of three tree species that were recorded in the data form.  Here observations were: River Birch – 34%, Red Maple 12%, and Black Oak – 6%.  Her wetland partner had the same tree species identified but his absolute percent cover values were quite different:  River Birch – 54%, Red Maple – 33% and Black Oak – 18%.  Why were their values so different?  Who was closer to the true values of absolute percent cover?    This is course led me to wonder that if both students were assessing the same area would their wetland conclusions be different?

In statistics, the variability that I observed is called “measurement error” and is present in all wetland delineations, as well as any process where measurements are taken by individuals.   Measurement error has two components:  accuracy and precision.  Accuracy is the difference between the average measured values and the true value.  Precision is how close all the measured values are to each other.   The graph below visually demonstrates the difference between accuracy and precision. Source: (http://kaffee.50webs.com/)

Going back to our example of the percent cover, let’s assume that the true values were River Birch – 43%, Red Maple – 21% and Black Oak – 15%.  If we took the average of the percent covers for each person it would be Birch – 44%, Red Maple – 22% and Black Oak – 12%. So it would seem that the accuracy of all the assessors (average values) was good.  But the precision in the measurements (variability between assessors) was not very good.   If we had asked each person to measure the same percent covers multiple times (unknowingly of course) we could have also measured the variability within the assessors.

Why does this error in measurement exist?  The answer, in general terms, is that each operator has slightly different methods for calculating percent cover.  In order to correct measurement error, the wetland delineation team would have to improve the process of how the percent covers were estimated. For instance, they could have a written procedure that explains exactly how the process should work, including pictures that demonstrate different percent covers.

There are of course other measurements taken during a wetland delineation that have potential for measurement error.   Examples include measuring the soil depth and determining the color percentage for the soil section.  Or determination if hydrology indicators are present at the site, such as surface soil cracks or moss trim lines.

Error exists in all wetland delineation processes where measurements are taken.  You will not be able to eliminate all the error but you will need to take steps to ensure that the error is minimized.   Error in your measurements could lead you to making incorrect conclusions regarding the decision about a site being a wetland.   Sometimes these errors can cost your company thousands of dollars.

There are statistical methods available such as control charts, analysis of variance, and attribute assessments to quantify the amount of measurement error that exists in your processes. These techniques can be useful in assessing measurement error in any data collection process. Understanding the concepts of measurement error, the tools to measure it, and being able to improve your measurement processes will provide you with meaningful data which you can use to make fact-based decisions.

The Swamp Stomp

Volume 16, Issue 12

As we venture through the wetlands, forests, swamps and even our backyards this spring we need to be aware of spiders. These arachnids are nearly everywhere and are pretty hard to avoid. Since you’re likely to run into one of them sooner or later, you should be aware of the potential dangers. There are a variety of spiders whose bite that will result in swelling, itching, and moderate pain. There are also a few spiders whose bite can be quite dangerous, so it’s a good idea to learn something about these arachnids.

In the U.S., the most common spiders that can cause harm are the black widow and the brown recluse. Although it is not likely that you will die from a bite from one of these spiders, you need to be aware of the danger and how to prevent exposure to them.

The brown recluse and black widow spiders both have special markings on their bodies that can help identify them. Brown recluse spiders are typically brown with a violin shaped marking pointing towards the abdomen on their heads. Another defining characteristic of this species of spider is that they have six eyes instead of the usual eight. In terms of size, these spiders can be anyway from ¼ to ¾ inches across their bodies. Black widow spiders can be easily identified by their shiny, black bodies and red hourglass shaped marking on the underside of their abdomen. However, it is important to keep in mind that this marking can range in color and the shape can sometimes be closer to a dot. Black widows are typically ½ inch in size.

Brown recluse spiders are found throughout the United States, but predominantly in the South. These spiders like to build their webs in small, dry hideaway spots, but can also be found in piles of leaves or under logs and rocks. Black widow spiders are common throughout the entire United States, but are mostly likely to be found in the southern and western states. They often live underneath things like woodpiles, debris piles, stones, and sheds. However, black widows can be found inside in places like basements and crawl spaces. So be aware of them even inside your house.

If you’re working in an area where you’re likely to encounter these spiders, it is vital to protect yourself from potentially getting bitten. To ensure safety, take the following precautions:

• Be able to identify these spiders. Proper identification can be one the most effective strategies to avoid getting bitten.
• Shake out clothing that’s been outdoors.
• Inspect clothing and tools before use.
• Wear protective clothing, like long sleeved shirts, long pants, hats, gloves, and sturdy boots while working in proximity to these spiders’ habitats.
• Reduce empty space between stacked materials and clear debris, as these can provide excellent hiding spots for spiders.

If you have been bit by a spider, check your symptoms to make sure it is not a venomous black widow or brown recluse. Some symptoms of spider bites can include itching or rash, pain around the bite area, muscle pain or cramping, red/purple bite or blisters, increased sweating, difficulty breathing, headache, and fever or chills. If you are experiencing any of these symptoms, seek medical help. Although extremely rare, you can die from a venomous spider bite!

While brown recluse and black widow spiders can pose a threat in the work place and everyday life, with proper safety techniques they can be avoided. Just be mindful of when you are in one of their habitats or near a place where these little creatures prefer to reside.

The Swamp Stomp

Volume 16, Issue 9

The disaster in Flint, Michigan has raised awareness for rising levels of lead in drinking water. Some reports say that our very own Allegheny River may have near-toxic levels of lead in the water, which raises questions as to how much this can affect one’s health.

What makes the situation in Flint so perilous is the fact that the lead that is in the water is originating from the pipes. In 2014, the town’s water source was switched from Lake Huron to the Flint River. Pipes were used that were not properly treated against corrosion, so throughout the years, the pipes have worn down and leaked literal poison into the water. There are very legitimate fears that the high levels of lead in the children of Flint’s bloodstreams, may lead to permanent neurological damage. The state of Michigan, the Environmental Protection Agency, and the federal government are seeking toprosecute the officials responsible for the decisions that led to the water crisis.

Lead works as a poison in the body, mimicking the actions of important vitamins and minerals such as calcium, iron, and zinc. As a result, lead can cause severe mental alterations as the brain has decreased oxygenation and decreased muscle function, since calcium is vital for healthy muscle contractions. Lead is odorless, tasteless, colorless, and virtually undetectable until symptoms start to occur. The only way that lead can affect you is if it is ingested, which is why it is important to check one’s home for lead paint, especially if there are children in the home.

After reports indicated high levels of lead in Pittsburgh water sources, the Pittsburgh Water and Sewer Authority (PWSA) began testing our own pipes for corrosion and came up with a safeguard against the poisoning of our water supply, the decision to switch from caustic soda to soda ash, a chemical that will create a film over the pipes to prevent corrosion.

In a report by the Pittsburgh Post-Gazette2, John Jeffries, supervisor of the county health department’s Public Drinking Water & Waste Management Program, said, “I think this is a good opportunity for people to understand the water systems of Allegheny County have been using the same sources for a very long time, and they are comfortable treating those to meet rules and regulations… For what it’s worth, I drink the tap water.”

Symptoms of lead poisoning in children include developmental delays, irritability, hearing loss, nausea, vomiting, abdominal pain, loss of appetite, and weight loss. In adults, symptoms include high blood pressure, muscle pain, joint pain, decline in mental functioning, miscarriages, and constipation. If you present with the symptoms above, it is important to get help right away.  Treatment for lead poisoning is Chelation Therapy, a process of ingesting a chemical and excreting the lead through the urine. In severe cases, EDTA therapy is used, where an even harsher chemical is used to excrete the lead.

It is important for people to understand the true danger of lead, especially lead in the drinking water, and be vigilant for signs and symptoms of possible toxicity. Hopefully, as the investigation in Flint continues, proper actions may be taken to resolve this very critical issue.

Bridget Seelinger is the editor-in-chief of The Scope, a publication of the Duquesne University Student Nurses Association. 

Article originally published at: https://duquesnescope.wordpress.com/2016/02/24/lead-a-threat-to-children-and-adults-alike/

References

Lead Poisoning, FAQ. (2015, January). Retrieved February 27, 2016, from http://dhss.delaware.gov/dhss/dph/files/leadpoisonfaq.pdf

The Swamp Stomp

Volume 16, Issue 6

President Obama vetoed a bill that would have blocked the Clean Water Rule on January 19, reported USA Today. The bill, which was proposed by Republicans last year, would have repealed EPA definitions of what constitutes federally regulated waters.

“Because this resolution seeks to block the progress represented by this rule and deny businesses and communities the regulatory certainty and clarity needed to invest in projects that rely on clean water, I cannot support it,” Obama said in a message to Congress.

The sponsor of the bill, Sen. Joni Ernst, a Republican from Iowa, said that bill was a necessary step against a “blatant power grab by the EPA,” reported the Washington Times. Many Republicans shared Ernst’s sentiment that the definitions put forth by the EPA were too broad.

Supporters of the rule argued that these definitions allowed for the government to oversee waters that people may not ordinarily think could lead to drinking water. Obama addressed this in his message to Congress, stating, “Too many of our waters have been left vulnerable. Pollution from upstream sources ends up in the rivers, lakes, reservoirs, and coastal waters near which most Americans live and on which they depend for their drinking water, recreation, and economic development.”

Republicans used a seldom used law, known as the Congressional Review Act, to propose the bill, according to USA Today. The Congressional Review Act allows for Congress to overturn laws made by federal agencies if they can pass a bill in both houses. The bill achieved this when it passed in the House of Representatives last month, receiving votes from every Republican member and three Democrats.

The veto, however, is likely to kill the bill entirely, as Republicans lack the two-thirds majority required to override a presidential veto. Congressional Republican remain determined to repeal the rule. According to USA Today, Ernst said she would continue to look for ways to undo the rule.