Posts Tagged ‘water quality


Air quality has an important impact on our community, and the Nine Mile Run Watershed Association is concerned about both the recent poor air quality events in the Monongahela River valley, and larger trends in Greater Pittsburgh on this issue.

In late December 2019, air quality in the Pittsburgh area took a nosedive. At the Liberty air quality monitor in the Mon Valley, not too far from the U.S. Steel Clairton Coke Works, levels of pollutants rose above regulatory limits for several consecutive days. At Pittsburgh International Airport in Moon Township, dozens of flights were canceled—at the peak of the holiday season, no less. PurpleAir’s air quality monitors showed poor air quality in the city, too. As Christine Brill of Lawrenceville Clean Air Now points out, residents were not immediately alerted about the situation, compounding the problem.

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December’s pollution event was the result of a temperature inversion—an event where air near ground level was warmer than air higher in the atmosphere, the inverse of the usual pattern. When this happens, pollution is unable to rise into the atmosphere with hot air in the way it usually does. Temperature inversions are likely becoming more common due to climate change, and the valleys of Western Pennsylvania are particularly susceptible to them. These events have plagued our region for generations—see the example of 1948’s Donora smog incident, a deadly pollution event that included a temperature inversion.

On January 10, 2020, a number of Pittsburgh-based environmental organizations held a Clean Air Rally (pictured above) at the Pittsburgh city-county building to protest this concerning holiday event. After the rally, dozens of people—including our Executive Director, Brenda Smith—spoke out during public comment at an Allegheny County Health Department (ACHD) meeting that afternoon.

A month later, the ACHD levied fines totaling $2.7 million, as well as additional penalties, on U.S. Steel for excessive pollution, settling a dispute dating back to 2019. The ACHD says it is developing further regulations on major polluters specifically focused on events similar to what happened in December.

We think it’s vital that the ACHD use their regulatory power in the case of another temperature inversion to require polluters to reduce their emissions during these sensitive events. Brill referenced a statute that could allow the ACHD to regulate pollution during temperature inversions without passing new legislation.

At the same time, the temperature inversion events and corresponding pollution have continued; the state Department of Environmental Protection placed 7 Western Pennsylvania counties, including Allegheny, under a poor air quality alert on January 23. (The same sort of alert had been issued during part of the holiday inversion about a month earlier, on December 24-25).

Air quality is vitally important to our region. There are a number of our nonprofit partners who work specifically on this issue. For more information on local air quality, we’d send you to our friends at GASP and Breathe Project, among other local organizations working on the issue. 

As a watershed association, we’re naturally concerned about air pollution’s effect on our watershed. In a process called atmospheric deposition, air pollutants make their way to the ground and into waterways, either falling on their own or being carried by precipitation.

Nitrogen is one important pollutant that travels into waterways by atmospheric deposition, and it can have a destructive effect on waterway wildlife. According to the Chesapeake Bay Program:

“Excess nitrogen can fuel the growth of algae blooms, which can block sunlight from reaching underwater grasses and create low-oxygen “dead zones” that suffocate marine life.”

University of Pittsburgh Ph.D. student Becky Forgrave has studied atmospheric deposition in Nine Mile Run. Forgrave summarized air pollution’s effect on pollution in NMR:

“…While there is definite evidence of atmospheric pollution in NMR, I think the major issues at this time are still mostly sewage and flooding related.” 

(Forgrave, personal communication)

In 2014, a lab colleague of Forgrave conducted a study on the sources of nitrogen in Nine Mile Run. During storms, they found that roughly one-third of nitrate pollution in NMR came from atmospheric deposition, compared to two-thirds from sewage. During dry times, nearly all nitrate inputs came from sewage.

While it may not be the most salient threat to our stream, atmospheric deposition is still an issue to pay close attention to in the Greater Pittsburgh area. Forgrave referenced a 2019 meta-analysis of studies on urban nitrogen deposition, which found that urban areas are “subject to higher rates of N deposition than nearby rural areas”. This finding implies that Greater Pittsburgh, like other urban areas, could be especially susceptible to nitrogen deposition concerns. 

Increases in precipitation brought on by climate change are making atmospheric deposition an even more important issue. A study from the Carnegie Institution for Science reviewed nitrogen deposition levels in comparison with climate data over time. The overpowering nature of climate’s effect on deposition is reflected in the study’s result in the Great Lakes, where “despite efforts to reduce the amount of nitrogen released by human activity, precipitation increased so much that nitrogen still overloaded the water system”, according to an article about the study (linked above). The additional risks for nitrogen deposition posed by climate change make it all the more imperative that we do what we can to reduce pollution levels. 

Though air quality isn’t the most important issue facing Nine Mile Run, it’s an issue that any environmentalist in Greater Pittsburgh should pay attention to—particularly considering the industrial pollution that has shaped our region. You may have heard about the Google engineer who told Public Source he plans to leave Pittsburgh due to air pollution. In response to that article, Carnegie Mellon professor Noah Theriault penned an opposing op-ed—saying that, yes, Pittsburgh is imperfect, but rather than leave at the first sign of difficulty, we can work together to make it better. The Nine Mile Run Watershed Association isn’t going anywhere, and we plan to be part of that work.

If you want to check local air quality levels and get directly involved, Purple Air has sensors across the region, Smell Pittsburgh features user-reported smell information, and AirNow.gov offers official government data.

By John Lavaccare, Communications Intern

Josie on a monitoring visit with Girty’s Run Watershed Association and the Pitt Water Collaboratory

Hello, my name is Josie and I recently graduated from Duquesne University with a Master of Science in Environmental Science & Management with a concentration in Conservation Biology. This summer, I am working with water quality monitoring data at the Nine Mile Run Watershed Association (NMRWA). Specifically, I am developing an aquatic macroinvertebrate sampling protocol for NMRWA. I am also collecting macroinvertebrate community data at Girty’s Run and Montour Run to compare Nine Mile Run with other urban watersheds. When I am not collecting data, I am updating and analyzing water quality data from previous years to help assess the progress of restoration at Nine Mile Run.

I grew up in the Laurel Mountains of Southwestern Pennsylvania, and started appreciating wildlife and the environment as a child. My backyard was a forested area with a small creek, and I remember playing there and collecting and identifying small organisms using encyclopedias and field guides local bookstores. At a young age, I realized that I had a passion for conservation and learning about wildlife. This opportunity at NMRWA allows me to explore my passion and apply the knowledge I have learned from my six years of education on environmental science.

In my stream field biology course, I helped collect and identify macroinvertebrates at Raccoon Creek with the Allegheny County Conservation District to see the impact of erosion on macroinvertebrate communities. Working on this project taught me how macroinvertebrate community structures can indicate the quality of a watershed, since there are specific organisms that are sensitive to pollution and environmental stress. While I was at Duquesne University, I collected water samples for 3 Rivers QUEST and I learned about water chemistry and sources of water pollution. These experiences allowed me to learn about monitoring watersheds by observing water chemistry and aquatic organisms in the field, and I am eager to learn more about watershed monitoring at NMRWA.

I thoroughly enjoy working at NMRWA because they are committed to restoring and protecting the environment and community. This organization has welcomed me onto their team and has allowed me to learn about the environmental efforts in Pittsburgh. I am learning that successful restoration requires consistent monitoring and commitment to improve water quality.


Now is a fantastic time to visit Nine Mile Run! We’ve been getting a few general safety questions from the public, and have a few things to keep in mind during your visit.

  1. While it’s tempting to let your kids splash around or let your dogs take a drink in the stream during a hot day, the water is not safe.

Due to our region’s combined sewer system, as little as 1/10th of an inch of rain causes sewage-contained stormwater to enter Nine Mile Run, in addition to other streams and rivers. NMRWA is doing our part by installing green stormwater infrastructure around the watershed to hold back some of the stormwater and keep it from overflowing, but there is more to be done. Stay safe, and keep yourself and your pets out of the stream, especially after it rains.


  1. Be sure to leash your dogs.

Not only is it an Allegheny County ordinance, but it is also a great way to protect the wildlife that call the Nine Mile Run ecosystem home.

Off leash dogs attack the possums, foxes, and raccoons that live in the forest; which is unsafe for both the wildlife and your pet. Off leash dogs wandering off of the trail are also detrimental to the plant restoration that our Urban Ecostewards are working so hard to foster.


  1. Be mindful of harmful plants that are native to the restoration area.

Poison Ivy


Poison Ivy is prevalent throughout the restoration area. Oils from their distinctive “leaves of three” can cause an itchy rash and blisters. Pets can also carry oils from poison ivy on their fur and pass it along to unsuspecting humans, which is another reason to keep dogs leashed and be aware of the plants around them.


Cow Parsnip

Cow Parsnip stems and leaves contain furocoumarins, a photosensitive chemical that causes rashes and blisters after exposure to ultraviolet light. Cow parsnip can grow up to 7 feet tall with rounded white flower clusters like an Alice in Wonderland Queen Anne’s lace.


  1. Watch out for ticks.

Pennsylvania has the unfortunate distinction of having the most cases of tick-borne disease of any state in the country, according to the CDC. In 2016 11,000 of the 36,500 reported Lyme disease cases nationwide were in Pennsylvania.

Here are several steps that you can take to make it less likely that you will be bitten by a tick while hiking this summer:

Stay on the trail when hiking through the park. Ticks are more prevalent off trail in Frick Park.  Frick Park is vastly overpopulated with deer, and the deer tick carries Lyme disease.

To prevent ticks from attaching to you wear long sleeved shirts and log pants, tuck the bottom of your pants into your boots, and apply repellants with DEET.

Check your body and clothes for ticks after returning home from your hike. Shower promptly after being in an area where ticks are prevalent.

Be aware of the symptoms of Lyme disease, and seek medical attention if they occur. According to the CDC early signs include fever, headaches, fatigue. Muscle and joint aches. A rash occurs in 70 percent of infected persons that expands gradually to be up to 12 inches across, and sometimes resembles a bull’s eye.


  1. Stay safe by the stream.


Nine Mile Run stream is beautiful. If a downpour starts, you may be tempted to stay near the stream and take photos or enjoy the sights. Remember that during heavy rain events stormwater from watershed neighborhoods enters the stream.

The water rises surprisingly quickly and that flooding can be dangerous.  If you get caught in a summer storm leave the stream and head to a safer part of the park.


Sh**t, scat, poo-poo, dookie, feces, crap, dog logs or my personal Pittsburgh favorite “Caca”,….whatever you want to call it, everyone agrees it’s disgusting and no one likes to have to handle it. But what’s even more disgusting, and I think you’ll agree, is poop in our streams, rivers, and drinking water. Consider these poop facts:

  • America’s 83 million pet dogs produce 10.6 tons of poop every year. (That’s a lot of doo doo.)
  • Only 60% of dog owners pick up after their pets!
  • A single gram of poop contains an estimated 23 million bacteria.

Pet waste contributes to poor water quality by adding harmful bacteria and nutrients to local waters. These bacteria lead to pathogens that pose public health risks. Fecal coliform bacteria, aka poop, can spread serious diseases like Giardia, Salmonella, e coli, Campylobacteriosis. For example, a Campylobacteriosis outbreak in 17 states this year affected 113 people. The bacterial infections proved to be resistant to seven different antibiotics!


Nutrients from poo-poo, mainly nitrogen and phosphorus, contribute to excessive algae growth which in turn robs water of dissolved oxygen, creating low water quality and unhealthy habitats for wildlife. Our fish friends won’t be able to survive!

So what’s “tragic” about improperly disposed waste? In 1968, scientist Garret Hardin coined the term tragedy of the commons to determine what happens in groups when individuals act in self-interest. Here’s the scenario: There is a communal pasture shared by a number of herders. Some realized that they could add an animal to the pasture and reap great rewards for themselves. The tragedy is that the pasture is eventually ruined by overuse and the entire group and their herds are affected. Many environmental issues fit this notion because they are shared resources, provided by Earth. When one person neglects to clean up after their dog, we all suffer from poor water quality, compromised ecological systems, and public health risks. So the next time you pick up your dogs smelly dookie, remember that you are doing your part to avert the tragedy of the commons! That’s something the entire Nine Mile Run community can be thankful for.




This guest post was written by Rob Rossi, a graduate student in the department of Geology and Environmental Science at the University of Pittsburgh. He was a graduate summer intern of NMRWA in 2015.

Road salt is a common part of winter for many Pittsburgh residents.  In Pennsylvania, more than 840,000 tons of road salt (sodium chloride, or table salt) were applied to roadways between 2009 and 2014.  Although it helps keep our roads and sidewalks ice and snow free, road salt has unintended consequences.  Many people are familiar with the ever annoying winter problems of salt stained clothing or shoes/boots, but the environmental effects of road salt are less obvious.  Road salt can have numerous negative effects on the environment, such as increased fresh water and soil salinity, and less obvious effects, such as increased time necessary for rain to soak into the soil.  Additionally, when road salt dissolves in highway runoff, these waters have high total dissolved solids (TDS), which can flush roadside soil metals from clay particles  (see animated Figure 1).  Metals flushed by these reactions can include plant nutrients (e.g., potassium, calcium, magnesium) or toxic trace metals (e.g., arsenic, lead, cadmium).

Road salt exchange gif

Figure 1. Animation of a cation exchange reaction. Potassium (K), calcium (Ca), and magnesium (Mg) ions bound to soil clay particles are exchanged by sodium (Na) ions in solution. Mobilized metals are then released into the soil water, and ultimately the ground or surface water.

Road Salt Study in Nine Mile Run

Lysimeter Working

Figure 2. Lysimeters are plastic tubes with a ceramic cup. To collect a soil water sample, a scientist applies a vacuum (arrow) and the lysimeter sucks up soil water (dashed lines) like a straw.

Rob Rossi, a graduate student in the Department of Geology and Environmental Science at the University of Pittsburgh, has been researching the effects of road salt on roadside soils in Nine Mile Run.  Specifically, Rob has been analyzing soil and soil water chemistry in samples collected from three roadside soil water sampler “nests”.  Each nest is a group of four lysimeters which behave much like giant straws, sucking up soil water samples when a vacuum is applied to the end of the soil water sampler (see Figure 2).  The lysimeters collect soil water at roughly 6, 12, 24, and 36 inch depths along a hill slope perpendicular to I-376.

In the soil samples, soil sodium concentrations are highest in soils collected from near the road.  Soil sodium concentrations decrease with distance from the roadway, approaching values observed in the local bedrock (see Figure 3).  One theory is that high sodium concentrations can be attributed to the minerals breaking down in the bedrock but because sodium concentrations in roadside soils are much higher than sodium concentrations found in the bedrock, minerals in the bedrock breaking down is likely not what inputs sodium to these soils.  Instead, the application of road salt to I-376 is likely causing high sodium concentrations in roadside soils.

Sodium concentration chart

Figure 3. Sodium concentrations in the sampled top (black), mid (red), and bottom (grey) hillslope soils. The vertical dashed line indicates the average sodium concentration in local bedrock. Parts per million (ppm) is a measurement scientists use to describe the concentration of an element. In other words, if a bucket holding a total of 1 million marbles contained 100 ppm of blue marbles, 100 of those 1 million marbles would be blue marbles.

Sodium concentrations in sampled soil waters peak at different times throughout the year relative to the location along the hillslope (see Figure 4).  In particular, the earliest peaks in soil water sodium concentrations occur in the top hillslope soil waters in late February/early March in the intermediate depth (39 and 61 cm depth) soil waters.  Additionally, soil water samples from the deepest top hillslope nest have, in general, the highest sodium concentration.  While sodium concentrations spike in soil waters collected from all depths of the top hillslope nest station, soil water sodium concentrations peak only in deeper soil waters of the mid hillslope nest.  Moreover, the peak in soil water sodium concentrations at the mid hillslope nest do not peak at the same time as when soil water sodium concentrations peak at the top hillslope nest.


Figure 4. Sodium concentrations in top (a), mid (b), and bottom (c) hillslope soil waters collected between October 2013 and November 2014. The light blue box indicates the time of the year when road salt is not applied to roadways.

These patterns in soil water sodium concentrations suggest that the way soil water flows in roadside soils influences the movement of sodium through these soils.  Specifically, because the deeper top hillslope lysimeters (i.e., 12, 24, and 36 inch) peak before the shallowest (i.e., 6 inch) lysimeter, high TDS waters likely interact with deeper soils first.  High TDS runoff from the highway is often observed to enter the soil column via infiltration (i.e., water percolating downwards through the soil), which produces a peak in sodium concentrations in the shallowest soil waters first.  However, because this pattern in soil water sodium concentrations is not observed in samples collected from the Nine Mile Run transect, sodium is potentially transported to deeper soils via lateral flow originating from leaking highway drains and water flow between bedrock layers.

Previous scientific studies have observed that sodium loadings to soils persist beyond the period when road salt is applied to roadways, and this relationship is also apparent at this study site.  Specifically, sodium persists as slow moving wave, where peaks in top hillslope soil water sodium concentrations occur within a month of when road salting ends, and peaks in soil water sodium concentrations at the mid and bottom hillslope stations occur later in the year.  Thus, the distance from the roadside affects when soil water sodium concentrations will peak, suggesting that sodium is relatively slowly released from roadside soils throughout the spring and summer.

How does road salt affect the water quality of Nine Mile Run?

The results of this study suggest that sodium and metals are continually flushed to stream waters throughout the year. When sodium levels are high, the ecosystem cannot physiologically maintain a salt balance, which affects aquatic organisms living in the stream – particularly plants and animals that are not adapted to high concentrations of ions, and therefore cannot regulate the water and salt content within their cells. This stress can change the diversity of species within the ecosystem. The increased metal loading could impair the stream ecosystem, negatively impacting aquatic life such as fish.  Some metals may be either beneficial or toxic, depending on their concentration. The primary mechanism for toxicity to organisms that live in streams is by absorption or uptake across the gills. The metals that are most toxic to aquatic organisms are Copper, Iron, Cadmium, Zinc, Mercury, and Lead.

I-376 Sodium runoff model

Figure 5. A conceptual model of how sodium travels through the hill slope soils next to I-376. The color of the arrows indicates the relative timing of when sodium is transported via this flowpath. Blue occurs in mid to late February, dark grey in early March, orange in early May, and red in early August.

Thus, it is likely that road salt application impacts soils down the hillside of I-376, and that the negative impacts of road salt application are not limited to the winter and early spring.

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