Sunday, March 31, 2024

Cicadas are Coming

This spring (late April and early May) the 17-year Brood XIII Cicadas will emerge in Northern Illinois, while the 13-year Brood XIX Cicadas will emerge in parts of Southeastern United States including parts of Virginia, but probably not more than a few stragglers in Northern Virginia.   Many people know periodical cicadas by the name "17-year locusts," but they are not the locusts of the bible. Those were a type of migrating grasshopper. However, if you live in the area of this year’s emergences , it may indeed feel like a plague for a few weeks. This is a big one, it is expected that this combined emergence will bring a trillion or more Cicadas.

However, counts of Cicadas are only estimates based on a very old data point.  The oft-quoted figure of densities that can exceed a million per acre comes from a census taken during the 1956 emergence of Brood XIII in Raccoon Grove, IL (Dybas and Davis 1962). Ironically, Brood XIII appears to have gone extinct in Raccoon Grove in the years since 1956 (Cooley et al. 2016). If the estimate of a million cicadas per acre is valid, then more than a trillions of cicadas will emerge in 2024 when Cicadas will emerge from Maryland to Oklahoma, Illinois to Alabama. It is not common to have a dual emergence between Broods XIII and XIX. They occur once every 221 years and the last time these two broods emerged together was in 1803 when Thomas Jefferson was President of the United States.

When they emerge in mass, you can report periodical cicadas using the Cicada Safari App, available on the Google Play Store or the Apple Store.  This will help scientists map the full extent of Brood XIII and XIX then we can really know the full extent of the Broods. If it does not feel like you are being inundated and you only see a few cicadas, they are probably stragglers from other broods and should not be reported. Otherwise, users can submit video and photos of periodical cicadas to the app. Once verified, they will be added to an online map. The app greatly assists in Cicada research.

from University of Conn

In late April and early May, Cicadas, probably both Magicicada septendecim and Magicicada cassinii will emerge from the soil and climb onto nearby vegetation and other vertical surfaces. They then molt to the winged adult stage. The emergence is tightly synchronized, with most adults appearing within a few nights. Adult cicadas live for only two to four weeks. When the 17-year periodical cicadas emerge the density can be shocking and noisy. It is common to have tens to hundreds of thousands of periodical cicadas per acre, but there are records of up to a million and a half periodical cicadas in an acre. This is far beyond the density of most other Cicada species and half of the Cicadas are “singing.” Male cicadas sing quite loudly by vibrating membranes on the sides of their abdominal segment. Male songs and choruses are a courtship ritual to attract females for mating. 

The males’ choruses have been known to drive people to distraction-stay inside with the windows closed if needed. However, for most people, the droning song of the cicada is nothing more than a slight annoyance. To me the “song” sounds like wind on a cell phone connection, but you can listen to the actual chorus on this U-Tube video from Storyful Viral. Most people are more familiar with the dogday cicada that is prevalent annually in mid-summer. Their song is later in the summer and not as persistent.

The 17 year or 13-year periodical cicada is black, with red eyes and orange legs. “Adults have clear wings with distinctive orange veins. When viewed from the front the wings form an inverted "V" and meet at the top like a roof.” After mating, females lay their eggs in narrow young twigs slicing into the wood and depositing up to 400 eggs in total for each female in 40 to 50 locations each. It is the egg laying that does most of the damage associated with periodical cicadas. Cicada eggs remain in the twigs for six to ten weeks before hatching. The nymphs do not feed on the twigs and all but the youngest trees will recover.


Wednesday, March 27, 2024

Flooding in Massachusetts

Excerpted from U.Mass and Massachusetts press release.

Our climate is changing, and that is impacting water. Though much has been made of the reduction in precipitation in the Southwest and water shortages, in truth, on average, total annual precipitation has increased over land areas in the United States and worldwide. Since 1901, global precipitation has increased at an average rate of 0.04 inches per decade, while precipitation in the contiguous 48 states has increased at a rate of 0.20 inches per decade.

Massachusetts has one of the most robust records of hydrological variables, such as precipitation and groundwater levels that goes back many decades. Studies this century suggest that climate will change the timing and nature of precipitation- alteration in thy hydrologic cycle.

Although few observational studies on ground water and climate have been done, in 2010 a group from the University of Massachusetts used the state’s wealth of data to examine the response of the water table to the last 60 years of climate in New England. That work by Boutt and Weider at the University of Massachusetts - Amherst found that since 1970, precipitation has increased in New England by 15–20%. Due to the geology in New England , this increase in precipitation is leading to a rapid rise in groundwater levels. In some parts of Massachusetts are seeing the water table rise by a few centimeters every year. While this value may seem small, the cumulative rise over decades can begin to affect sub-surface infrastructure.

Dr. David Bout head of the Hydrogeology Group at University of Massachusetts- Amherst and a professor of Earth, Geographic and Climate Sciences (EGCS) has been studying the impact of our changing climate on groundwater since 2005. Recently, the work being done by his group caught the eye of the state’s Executive Office of Energy and Environmental Affairs and Department of Conservation and Recreation, both of which asked Boutt and his colleagues to build a new model that could assess flooding risk from groundwater rise to improve that model with data from an ongoing statewide survey and to file a final report, which the group is in the process of completing.

To date their conclusions are that shallow groundwater in Massachusetts will rise by an average of 0.14-0.8 ft in the coming  years. The Groundwater Rise Risk Zones will increase groundwater flooding by 8-16%, groundwater emergence will increase by 7-14% and groundwater shoaling will increase by 4-8%. University of Massachusetts- Amherst expects the greatest groundwater risks to occur in Western Massachusetts.


Types of Groundwater Flooding
  • Groundwater rise: Movement upward of the water table due to short or long-term fluctuations in rainfall recharge and/or river, ocean or tidal levels.
  • Groundwater shoaling: Water table rise in the subsurface closer to, but not reaching, the land surface.
  • Groundwater emergence: Discharge/outflow of groundwater at the surface from the subsurface due to the rise of the water table at a point (spring) or diffuse locations.
  • Groundwater flooding: Temporary process of the rise of the water table resulting in a groundwater emergence where the water level surface intersects or goes above the land surface due to a changing condition.
From U.Mass presentation and quoting Bosserelle et al., 2021, Earth’s Future

Sunday, March 24, 2024

Groundwater- the Basics

Groundwater is the subsurface water that fills the spaces, pores or cracks in soils and rocks.   Aquifers are the name given to any body of rock or sand that contains a usable supply of water. The upper surface of this water-filled area, or "zone of saturation", is called the water table. The saturated area beneath the water table is called an aquifer, and aquifers are huge storehouses of water for mankind and the planet itself. A good aquifer must be both porous enough to hold water and permeable enough to allow the water to flow and the continuous recharge of water to a well.

Most of the void spaces in the rocks below the water table are filled with water. Depending on type, soils and rocks have different porosity and permeability characteristics, which means that water does not move around the same way in all rocks below ground. Combined together geology and rainfall determine the character of and the quantity of the groundwater.

Groundwater is replenished by the seepage of precipitation that falls on the land and infiltrates into the water table and the aquifer, and sometimes by surface water. Mankind can artificially deplete or replenished groundwater. There are many geologic, meteorologic, topographic, and human factors that determine the extent and rate to which aquifers are refilled with water or used up.

As the US Geological Survey points out: “Nearly all surface-water features (streams, lakes, reservoirs, wetlands, and estuaries) interact with ground water. These interactions take many forms. In many situations, surface-water bodies gain water and solutes from ground-water systems and in others the surface-water body is a source of ground-water recharge and causes changes in ground-water quality. As a result, withdrawal of water from streams can deplete ground water or conversely, pumpage of ground water can deplete water in streams, lakes, or wetlands.”

Though the type of rock will determine the water capacity of the aquifer. There is variability in at what depth rocks are found. A relationship does not necessarily exist between the water-bearing capacity of rocks and the depth at which they are found, it varies tremendously by region and continent. A very dense granite that will yield little or no water to a well may be exposed at the land surface. Conversely, a porous sandstone may lie hundreds or thousands of feet below the land surface and may yield hundreds of gallons per minute of water. On the average, however, the porosity and permeability of rocks decrease as their depth below land surface increases because the weight of the overlying rocks compresses pores and cracks in rocks at great depths.

Geologic conditions also control the distribution of what are called structural belts of the earth’s surface that were formed with the mountains. These belts influence groundwater flow, recharge and discharge. Both geomorphology and geology determine the volumes of surface runoff and amounts and rates of infiltration. Depending on geologic conditions, ground water can be directly connected to surface water or not connected with surface water. The connection with surface water affects the ability of an aquifer to be recharged. Groundwater that has lost it’s connection to surface water

Like water on the earth’s surface, groundwater tends to flow downhill under the influence of gravity and eventually discharges, or flows out of the ground, into streams or other surface water-dependent areas, such as wetlands in the geology of New England and the mid-Atlantic states.

Ground water flow and storage, often viewed as static reservoirs, are dynamic and continually changing in response to human and climatic stress [Alley et al., 2002Gleeson et al., 2010]. Increase or decrease in precipitation patterns impacts available surface and groundwater. Man’s hand in changing the surface also impacts water resources. Land use changes that increase impervious cover more than 5-10% from roads, pavement and buildings does two things. It reduces the open area for rain and snow to seep into the ground and percolate into the groundwater and the impervious surfaces cause stormwater velocity to increase preventing water from having enough time to percolate into the earth, increasing storm flooding and preventing recharge of groundwater from occurring. 

Slowly, this can reduce water supply over time. Increasing population density increases water use. Significant increases in groundwater use and reduction in aquifer recharge can result in the slowly falling water levels over time showing that the water is being used up. Unless there is an earthquake or other geological event groundwater changes are not abrupt and problems with water supply tend to happen very slowly as demand increases with construction and recharge is impacted by adding paved roads, driveways, houses and other impervious surfaces. 

The changing land use impacts regional hydrology and groundwater recharge so the quantity of available groundwater and streamflow may decrease with the same amount of precipitation. Groundwater serves as a savings account for rivers and streams. Sustainability of groundwater is hyper-local. Little is known about the sustainability of our groundwater basins, but that is changing. Groundwater models and data from more monitoring wells can help develop a picture of the volume of the water within the groundwater basin and at what rate it is being used and at what rate it is being recharged. This can help manage water resources during drought years and wet years.

Wednesday, March 20, 2024

Nano Plastics found in Bottled Water

The blog is excerpted from the Columbia University researchnews and the recently published article in the journal Proceedings of the National Academy of Sciences. The study was coauthored by Xin Gao and Xiaoqi Lang of the Columbia Chemistry Department; Huipeng Deng and Teodora Maria Bratu of Lamont-Doherty; Qixuan Chen of Columbia’s Mailman School of Public Health; and Phoebe Stapleton of Rutgers University.

Plastics, a creation of mankind have become ubiquitous in our lives and on our planet. Plastic is a wonder, but is also one of the most commonly littered items in the world. Scientists have found that virtually all the plastic we ever made is non-degradable and is still with us. Much of the plastic ends up in landfills, or worn into smaller particles in the soil, in the ocean, or in our rivers, streams, lakes and estuaries, even in the air we breath. The existence of microplastics (1 µm to 5 mm in length) and the smaller nano plastics (<1 μm) has in recent years has raised health concerns.

Micro and nano plastics originating from the use and improper disposal of plastics worldwide have increasingly raised concerns because they have been found to have a negative impacts on the endocrine components in mammals- hypothalamus, pituitary, thyroid, adrenal, testes, and ovaries. Micro and nano plastics absorb and act as a transport medium for harmful chemicals such as bisphenols, phthalates, polybrominated diphenyl ether, polychlorinated biphenyl ether, organotin, perfluorinated compounds, dioxins, polycyclic aromatic hydrocarbons, organic contaminants, and the heavy metals, which are commonly used as additives in plastic production.

Nano plastics are so tiny that, unlike microplastics, they can pass through the intestines and lungs directly into the bloodstream and travel from there to organs including the heart and brain. Nano plastics can invade individual cells, and cross through the placenta to the bodies of unborn babies. Medical researchers are studying the impact of nano plastics on a wide variety of biological systems- and they indeed  appear to be endocrine disrupting.

However, there has remained a fundamental knowledge gap in nano plastics because of the lack of effective analytical techniques. The Columbia University study linked above  developed a powerful optical imaging technique for rapid analysis of nano plastics with never before seen sensitivity and specificity. As a demonstration, micro-nano plastics in bottled water were analyzed with profiling of individual plastic particles.

The researchers searched for seven specific plastics in three “popular brands” of bottled water (they declined to name which ones), analyzing plastic particles down to just 100 nanometers in size. They spotted 110,000 to 370,000 particles in each liter, 90% of which were nano plastics; the rest were microplastics. They were also able to determine  which of the seven specific plastics they identified.

One common nano plastic founde was polyethylene terephthalate or PET. This is what many water bottles are made of so finding it was not suprising. (It is also used for bottled sodas, sports drinks and condiments such as ketchup and mayonnaise.) It probably gets into the water as bits slough off when the bottle is squeezed or gets exposed to heat. One recent study suggests that many particles enter the water when you repeatedly open or close the cap, and tiny bits abrade.

However, the number of particles of PET was outnumbered by polyamide, a type of nylon. Ironically, the scientists believe, that probably comes from plastic filters used to purify the water before it is bottled. Other common plastics the researchers found: polystyrene, polyvinyl chloride and polymethyl methacrylate, all used in various industrial processes.

The seven plastic types the scientists searched for accounted for only about 10% of all the nanoparticles they found in samples; they have no idea (yet) what the rest are. If they are all nano plastics, that would mean that nano plastic particles could number in the tens of millions per liter.

The scientists plan to continue their work, with plans to look at tap water, which also has been shown to contain microplastics, though far less than bottled water according to a meta study by Isabella Gambino et al cited below  The researchers are now studying micro plastics and nano plastics generated when people do laundry, which end up in wastewater—so far, by a count of millions per 10-pound load, coming off synthetic materials that comprise many items of clothing.

The team will also identify particles in snow that British collaborators trekking by foot across western Antarctica  are currently collecting. They also are collaborating with environmental health experts to measure nano plastics in various human tissues and examine their developmental and neurologic effects. What we have done to our planet.


Gambino I, Bagordo F, Grassi T, Panico A, De Donno A. Occurrence of Microplastics in Tap and Bottled Water: Current Knowledge. Int J Environ Res Public Health. 2022 Apr 26;19(9):5283. doi: 10.3390/ijerph19095283. PMID: 35564678; PMCID: PMC9103198.

Sunday, March 17, 2024

Prince William needs to Protect the Occoquan Watershed

With assistance from the PWCA ORPA workgroup.

The Occoquan Reservoir is a vital drinking water source for 800,000 residents in Northern Virginia including residents on the eastern end of Prince William County. The Occoquan Reservoir watershed spans less than 600 square miles and Prince William County has the largest portion of land area within the Occoquan Watershed in its jurisdiction (40%). Other jurisdictions comprising the watershed include Fauquier County (36%), Fairfax County (17%), and Loudoun County (5%). The City of Manassas and the City of Manassas Park comprise a total of about 2%.

As of the 2020 Census, there were approximately 574,000 people residing within the watershed. About 43% of the population in the Occoquan Watershed resides in Prince William County. As the most populous jurisdiction in the Occoquan watershed and the one with the largest land area, substantial changes in land use patterns in areas of Prince William County will impact water quality in the watershed which will impact the groundwater, the streams and rivers and the Occoquan Reservoir.

To protect the Occoquan Watershed, Fairfax County downzone 41,000 acres of land and protected another 5,000 along the Occoquan Reservoir during the 1980’s. Prince William County adopted a rural area called the Rural Crescent with the adoption of the 1998 Comprehensive Plan which served to protect the headwaters in the fragile Bull Run watershed and Occoquan Watershed by alleviating development pressure in the already heavily urbanized drinking water watershed.

When Prince William County approved their Comprehensive Plan pathway to 2040, the “Rural Area” designation was eliminated. It was replaced it with an "Agricultural Estate" designation covering 55,310 acres and with an "Agricultural and Forestal" designation covering 75,647 acres. These new designations allow for more development in the rural area. Recent rezonings have allowed even more intense development in what was once the rural area. The Comprehensive Plan update also established an Occoquan Reservoir Protection Area (ORPA), to protect the Occoquan Reservoir as a public water supply and meet the requirements of the Chesapeake Bay Watershed Implementation Plan that Virginia is using to meet the US EPA enforced Pollution Reductions mandates.

Protecting the Occoquan Reservoir requires protecting all the water resource in a region because all water on earth is connected. Precipitation moves into the water table (the hyporheic zone) down to groundwater or into rivers and streams. Disrupting the balance of water flow can have dire consequences. The available supply of fresh water is continually renewed by the hydrologic cycle and in the case of the Occoquan Reservoir the actions of mankind. The need for water is constant and grows with population and wealth and business activity. There is also a seasonality to water- we use more in summer.

Many activities of mankind interfere with the hydrologic cycle. Through land change we interrupt the recharge of groundwater which impacts stream flow. Changing the use of the land, covering it with buildings, driveways, roads, walkway and other impervious surfaces will change the hydrology of the site reducing groundwater recharge in the surrounding area increasing stormwater runoff velocity and quantity and reducing streamflow which is feed by groundwater.

As groundwater levels fall, perennial steams that feed the rivers become ephemeral. The groundwater becomes disconnected from the surface water network. Once the hydrology is destroyed by development, it cannot be easily restored, if at all.

The Occoquan Reservoir is fed by the Occoquan River which receives up to 40 million gallons a day of the treated discharge of the Upper Occoquan Sewage Authority treatment plant which discharges to the river upstream of the Occoquan Reservoir so, a significant portion of the flow (especially during dry periods) into the reservoir is recycled sewage. This treated wastewater is from areas supplied by the Corbalis plant or lake Manassas so you do not end up with constantly recycling and concentrating the same impurities into the Occoquan.

In addition, the reservoir receives stormwater runoff, precipitation from the Occoquan Watershed and feeds the streams and creeks that feed Bull Run and the Occoquan River. When generally open rural area is developed, stormwater runoff increases in quantity and velocity washing away stream banks, flooding roads and buildings carrying fertilizers, oil and grease, and road salt to the Occoquan Reservoir. The faster flow of storm water gouges the riverbeds picks up pollutants from impervious surfaces. The cumulative impact of these steps leads to flash floods, unstable banks, heavy pollution and waning life. This is why it is essential to have an ORPA, to ensure both public and private water users continue to have water to drink and use.

Geology, climate, weather, land use and many other factors determine the quality of the groundwater and in turn streamflow. Within Prince William County Virginia there are four distinct geologic provinces: (1) the Blue Ridge, (2) the Culpeper Basin, (3) the Piedmont, and (4) the Coastal Plain. The U.S. Geological Survey divides the four geologic provinces of the county into seven hydrogeologic groups based on the presence and movement of the ground water calling them groups: A, B, B1, C, D, E and F.

The quantity and quality of ground water in Prince William County varies across the county depending on the geologic and hydrogeologic group you are in. The rocks in the Blue Ridge, Piedmont, and Coastal Plain contain minerals that are resistant to weathering, and the ground water tends to be acidic having low concentrations of dissolved constituents. Generally speaking, the groundwater in the county is recharged in elevated areas between stream valleys and channels and discharges to streams and estuaries. However, the paths and duration of groundwater flow are different between consolidated rocks and unconsolidated material. Groundwater in the consolidated rocks flows through the system of fractures following a circuitous path before discharging to a stream or estuary. In unconsolidated material, ground water generally follows a direct path from the recharge area to the discharge area.

In the area of the proposed ORPA is beyond the Culpeper Basin in the Piedmont region. This area of the ORPA is primarily hydrogeologic group D composed of igneous rock formations with limited lenses of hydrogeologic group E that transition at the bounds of the ORPA to group E and then to the Coastal Plain.

Hydrogeologic group D is located within the Piedmont formation and consists of three igneous plutons in the eastern part of Prince William County: the Goldvein, Lake Jackson, and Occoquan Plutons. Rocks within hydrogeologic group D tend to have moderate water-bearing potential and ground-water storage tends to be predominantly in the overburden, which is the soils above the bedrock. Wells in this area are most susceptible to drought and tend to be slightly acidic. The igneous rocks have subhorizontal sheeting and near vertical joints overlain by thick overburden. Groundwater wells in the area tend to have yields range from 1.2 to 100 gal/min which has resulted in the development of homes with wells in the area due to the thickness of the water storing overburden.

Hydrogeologic group E is also in the Piedmont formation in the eastern part of the county, and consists of metasedimentary, metavolcanic, and other metamorphic rocks. Rocks within hydrogeologic group E tend to have poor water-bearing potential, and thin- to thick cover of overburden. Similar to the rocks of hydrogeologic group D, ground-water storage tends to be predominantly in the overburden. Some of the poorest yielding wells in Prince William County are located in this hydrogeologic group and can be as low a 0.25 gallons per minute upto 70 gallons per minute-, but tending towards the low end because of the thinness of the overburden beyond the limits of what is the proposed ORPA. Homes and businesses in this area have depended on public water supply due to the limitations on well development and that water comes from the Occoquan Reservoir.

Protecting groundwater serves to protect all of the water resources in the watershed. Today, the Occoquan watershed is often described as the most urbanized watershed in the nation. Certainly there are far more urbanized areas in the United States, but they do not have functioning watersheds. We need to effectively protect ours.

Wednesday, March 13, 2024

Death Valley Ephemeral Lake

Death Valley is the driest place in North America, with some areas receiving less than two inches of rain per year, and is the location of the highest temperature (134 °F on July 10, 1913) ever recorded in the United States. The valley is not dead, it is a below-sea-level basin, surrounded by towering peaks that are often frosted with winter snow. Rare rainstorms bring vast fields of wildflowers. Lush oases harbor tiny fish and serve as a refuge for wildlife and human life.

Usually Death Valley visitors see a vast salt flat at Badwater Basin. However heavy rain from Hurricane Hillary in August 2023 brought 2.2 inches if rain that filled the valley floor with a vast, shallow lake. At its largest, it was about 7 miles long, 4 miles wide, and two feet deep. Imagine only 2.2 inches of rain doing that!

By late January it had shrunk to about half that size, and was inches deep. Then an atmospheric river brought another 1.5 inches in early February, 2024 and after the atmospheric river moved through, the lake continue to expand as water drained into the basin from the Amargosa River, which feeds the basin from the south.  The Amargosa is usually an intermittent river was observed to be flowing by park rangers.

Badwater Basin is endorheic, meaning that water flows into but not out of it. Typically, evaporation far outpaces inputs from rain and the Amargosa, rendering the lake ephemeral. But in the past six months, the unusual atmospheric rivers have changed the equation. As of mid February, the lake is 1 foot deep in places, and it is uncertain how long it will last. Past appearances of the lake are rare- appearing in 2005 and 2015 and none on record have lasted as long as this one.

The satellite image below is from NASA Earth Observatory images by Wanmei Liang, using Landsat data from the U.S. Geological Survey. Photo by K. Skilling/National Park Service.


Sunday, March 10, 2024

Total Eclipse of the Sun


On Monday, April 8, 2024 a total solar eclipse will cross North America, passing over Mexico, the United States, and Canada. Weather permitting the total solar eclipse will begin over the South Pacific Ocean and hit Mexico’s Pacific coast at around 11:07 a.m. PDT. This is probably the last solar eclipse to cross North America in my lifetime. The last eclipse I saw was in July 1963, and this is my last shot to see another. I live under 200 miles from the path of totality and should be able to see much of the eclipse from home, but we are in a solar maximum and a few hours drive could yield quite a show! You can watch along with NASA.

The path of this eclipse will move from Mexico, entering the United States in Texas, and traveling through Oklahoma, Arkansas, Missouri, Illinois, Kentucky, Indiana, Ohio, Pennsylvania, New York, Vermont, New Hampshire, and Maine. Small parts of Tennessee and Michigan will also experience the total solar eclipse. The eclipse will enter Canada in Southern Ontario, and continue through Quebec, New Brunswick, Prince Edward Island, and Cape Breton. The eclipse will exit continental North America on the Atlantic coast of Newfoundland, Canada, at 5:16 p.m. NDT. We are close enough to drive to see it full on, but the eclipse will be visible all along the northeast corridor. 


The path of totality is where the moon will completely cover the sun making the sun’s corona visible. Viewing of partial eclipse will be possible from a much wider geographic area. This area is about 115 miles wide, In this area looking directly at the sun is unsafe except during the brief total phase of a solar eclipse (“totality”), when the moon entirely blocks the sun’s bright face, which will happen only within the narrow path of totality and only during the window of complete coverage which is about 4 and a half minutes. Otherwise you must protect your eyes and vision. The only safe way to look directly at a partially eclipsed sun is through special-purpose solar filters, such as “eclipse glasses or hand-held solar viewers.

Homemade filters or ordinary sunglasses, even  dark ones, are NOT SAFE for looking at the sun; they transmit thousands of times too much sunlight. Eclipse glasses and handheld solar viewers must be verified to be compliant with the ISO 12312-2 international safety standard for such products. Make sure you have real solar glasses. It's not enough today to just look for the ISO 12312-2  certification, because in 2017 many unscrupulous vendors on Amazon were printing fake glasses with ISO 12312-2  certifications. Only buy glasses made in the United States from a vendor on the approved list of the American Academy of Ophthalmology.  You can also view the eclipse on NASA’s web site or through a pinhole projector as we did when we were kids. NASA’s has a diagram on how to make a pinhole projector.

Most of the ‘beauty shot’ photographs you will see of the eclipse will be taken with professional digital cameras on tripods, or shot through a telescope, but the most common photos you will probably see will be taken by the millions of smartphones used by ordinary people to capture this event. Read NASA’s tips and precautions and remember to protect your eyes.

Do NOT use eclipse glasses or handheld viewers with cameras, binoculars, or telescopes. Those require different types of solar filters. When viewing the partial phases of the eclipse through cameras, binoculars, or telescopes equipped with proper solar filters, you do not need to wear eclipse glasses. (The solar filters do the same job as the eclipse glasses to protect your eyes.)

Wednesday, March 6, 2024

Looking for PFAS Sources in the Occoquan Watershed

 On March 14, 2023, EPA announced the proposed National Primary Drinking Water Regulation (NPDWR) for six Per- and Polyfluoroalkyl Substances (PFAS) including perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX Chemicals), perfluorohexane sulfonic acid (PFHxS), and perfluorobutane sulfonic acid (PFBS). When finalized, the proposed regulation will require public water systems to monitor for these chemicals.

In anticipation of the regulations, Fairfax Water hired an independent lab to test their water using current EPA-approved methods that can detect PFAS at much lower concentrations than previous methods. Fairfax Water also participated in the Virginia Department of Health (VDH) Occurrence Study that was completed in 2021. However, the practical quantitative limit was 4 ppt just at the proposed regulatory limit. Fairfax Water found that some of the results for the Occoquan Reservoir for PFOS and PFAS were above the MRL and the regulatory limit. Since that time the Occoquan Watershed Laboratory has upgraded their analytical equipment.

PFAS dissolves in water and combined with their chemical properties means that traditional drinking water treatment technologies used at water treatment plants are not designed to remove them, it is believed though, that carbon filtration does remove some. Activated carbon adsorption, ion exchange resins, and high-pressure membranes have been found to remove PFAS from drinking water, especially PFOA and PFOS, which have been the most studied of these chemicals and the PFAS substances with the lowest promulgated drinking water limit . Testing these technologies at the new regulatory limits is underway, but even if effective it could cost millions up to a billion dollars to remove PFAS from the Occoquan Reservoir, then the problem is how to dispose of the PFAS removed from the water. This would bring a whole new liability to the water utility.

The best strategy is to look for the sources of PFAS in the Occoquan watershed and prevent those from reaching the reservoir rather than removal by Fairfax Water. Source water protection  is the best solution if it can be done. With that in mind both Fairfax Water and the EPA have developed an analytic framework which provides information about PFAS across the environment. Now Fairfax Water has begun testing in the watershed to identify the sources of PFAS. 

Armed with $750,000 in new equipment for the purpose, the Occoquan Watershed Laboratory has begun to test samples from throughout the Occoquan watershed to determine where the PFAS in the reservoir is coming from. To start with there are several potential known sources: the reclaimed water from UOSA, accidental releases from Manassas airport,  and the old Vint Hill army base where the Fauquier Times reported that for the past several years, the U.S. Department of Defense has been monitoring PFAS contamination at Vint Hill that is believed to be tied to a former burn pit where soldiers practiced putting out fires with firefighting foam containing PFAS chemicals, which then leached into the soil and the groundwater.

There is no longer enough water in the rivers in the Occoquan watershed to consistently meet the demand during dry periods, so the Upper Occoquan Service Authority, UOSA, the waste water treatment plant also delivers 40 million/day of recycled water that originated in the Potomac River to the Occoquan Reservoir. Supplementing the supply. According to Fairfax Water diet is responsible for 66%-72% of exposures to PFOA and PFOS (the two chemicals that have been most widely studied). In some cases, they have also leached into both surface and groundwater. Water is responsible for 22%-25% of exposures. Keeping PFAS out of the source water the real challenge when PFAS is in our diet and wastewater is reused in our drinking water supplies. To stay within the regulatory limit, Fairfax Water will have to identify the PFAS content in the various source of water and can mix them to minimize exposure or remove them.

Another way PFAS could have reached the Occoquan Reservoir was from accidental release from Manassas Airport. The Manassas Airport is upstream from the Occoquan Reservoir along Cannon Branch which flows into Long Branch, and accidents do happen.  In February 2020, a malfunction released a large spill of PFAS-based firefighting foam from a hangar at Manassas Regional Airport, in the Occoquan River basin. Aqueous film-forming foam, which is known as AFFF, is a firefighting foam widely used in the aviation industry because it quickly extinguishes fuel fires by spreading across the surface, depriving the fire of oxygen. This also makes a spill hard to control. The spill was not entirely contained. The foam contains chemicals known as per- and polyfluoroalkyl substances (PFAS). There are likely to have been other spills over the years. So, soils and groundwater in that part of the watershed may be contaminated.

The Fauquier Times has reported that the area near Vint Hill army base gets its drinking water from Buckland Water and Sanitation, a private company, and that the water is  distributed by the Fauquier County Water and Sanitation Authority. Buckland apparently has been  testing Vint Hill wells for PFAS for years but failed to disclose it since it was not covered under the safe drinking water act. The level of contamination at the site was reported by the Fauquier Times and the Prince William Times was hundreds of times higher than the proposed drinking water standard.

There are other potential sites in the Occoquan Watershed to be studied and tested for PFAS. The old Atlantic Richfield superfund site recently acquired by Microsoft was never tested for PFAS though the groundwater has been monitored for solvents for years. There are likely to be other sites to test.

Related Reading and sources:,when%20the%20substances%20were%20detected.

Testing begins to find sources of 'forever chemicals' in the Occoquan Reservoir | News |

Sunday, March 3, 2024

We’re Sinking and Sea Level is Rising

This article is excerpted from the article cited below,  the Virginia Tech news release, the NOAA 2022 update to the Sea Level Rise Technical Report and a previous blog post. 

Leonard O Ohenhen, Manoochehr Shirzaei, Patrick L Barnard, Slowly but surely: Exposure of communities and infrastructure to subsidence on the US east coast, PNAS Nexus, Volume 3, Issue 1, January 2024, pgad426,

In 2022 NOAA Released an update to the Sea Level Rise Technical Report. The report project sea level along the U.S. coastline to rise, on average, 10 - 12 inches (0.25 - 0.30 meters) in the next 30 years (2020 - 2050), matching the rise measured over the last 100 years (1920 - 2020). Sea level rise will vary along U.S. coasts because of changes in both land and ocean height.

The east coast is expected to be the relative sea level hot spot over the next three decades projected to rise on average: 10 - 14 inches (0.25 - 0.35 meters). This hot spot along the east coast extends from Cape Hatteras, North Carolina to Boston, Massachusetts with the Southern Chesapeake Bay region will experiencing the most significant rise.

In the last century this area experienced the highest rate of sea level rise in the nation and is forecast to continue to have the highest sea level rise in the next 30 years due to glacial rebound, land subsidence and the rising sea levels. In the most recent study Ohenhen et al, looked at the contribution of land subsidence on the relative sea level rise. They found that the major cities on the U.S. Atlantic coast are sinking, in some cases as much as 5 millimeters per year – a decline at the ocean’s edge that well outpaces global sea level rise. The land subsidence is due to compaction from groundwater pumping. When you withdraw the groundwater from fine-grained compressible confining beds of sediments which are typical of the coastal regions (and other areas)  and do not replace it, the land subsides. 

To examine the phenomena the scientist used space-based radar satellites to build digital terrain maps that show exactly where sinking landscapes present risks to the health of vital infrastructure within 62 miles of the coastline. Using the publicly available satellite imagery, Ohenhen et al measured millions of occurrences of land subsidence spanning multiple years. They then created some of the world's first high resolution depictions of the land subsidence.

The scientists found that New York City, Long Island, Baltimore, Virginia Beach and Norfolk are seeing areas of rapid “subsidence,” or sinking land, alongside more slowly sinking or relatively stable ground. This differential subsidence  increase the risk of damage and failure to roadways, bridges runways, building foundations, rail lines, and pipelines,

In Virginia our local land subsidence is due to glacial rebound after the Laurentide ice sheet melted, excessive groundwater extraction from the coastal aquifers, as well as the effects of the meteor impact near Cape Charles, Virginia (about 35.5 million years ago). Combined, they are all causing the relative sea level rise that is the highest along the coastline. The Aquifer-system compaction from non-sustainable groundwater extraction accounts for more than 50% of the land subsidence observed in the coastal region. 

Land subsidence barely registers as an issue of concern in public policy. However, this slow, gradual, and unapparent land sinking motion magnifies the exposure of coastal residents to the increases in sea levels due to climate change.  Subsidence increases the threat to coastal communities from sea level rise and may even triple estimates of potential flooding areas over the next few decades. Even if current climate measures successfully curb rising sea levels, continuous land subsidence may result in irreversible inundation, more frequent flooding and damage to infrastructure in these coastal regions.

Subsidence of more than a few millimeters per year are a cause for concern, particularly in densely populated areas because subsidence can undermine building foundations; damage roads, gas, and water lines; cause building and bridge collapse. Differential subsidence is most damaging especially in areas with essential facilities like hospitals, schools, or transportation hubs.

These groundbreaking new maps generated by Ohenhen et al show that a large area of the East Coast is sinking at least 2 mm per year, with several areas along the mid-Atlantic coast (Virginia) of up to 1,400 square miles, sinking more than 5 mm per year. This is more than the current 4 mm per year global rate of sea level rise. These coastal regions, where most large cities are located  are on the front lines of climate change impacts and associated uncertainties due to the combined effect of subsidence and sea level rise.  

Over the past century population migrated to the low-elevation coastal areas.  Continued accelerating sea-level rise and land subsidence will increase the future vulnerability of coastal communities worldwide. The impact of sea level rise-amplified hazards on coastal communities, such as flooding and erosion, dominates discussion and planning  in global climate change discussions, with land subsidence (due to unstainable groundwater use) relegated to the background. Land subsidence, however, is a pernicious and growing problem on a global scale with more immediate hazards to coastal areas and often presents more pressing and localized challenges. Policy changes to better manage groundwater withdrawal could slow relative sea level rise.

The lead author of this study is Leonard Ohenhen, a graduate student working with Associate Professor Manoochehr Shirzaei at Virginia Tech’s Earth Observation and Innovation Lab. This work provides important quantitative data for coastal disaster resilience planning.


Leonard Ohenhen

Manoochehr Shirzaei