Friday, November 10, 2017

Acid Rain Harmful to Animals?

Acid rain is precipitation containing nitric and sulfuric acids. While some natural occurrences like volcanoes and rotting vegetation contribute to these acids, it is the human activity of burning fossil fuels that causes a majority of acid rain. When acid rain reaches the surface of the Earth, it can devastate ecological systems by killing populations, eliminating food sources and reducing biodiversity.

Acid Rain and Water Sources

The U.S. Environmental Protection Agency says the effects of acid rain are most obvious in aquatic ecosystems. Water runoff from forests and roads often flows into streams, lakes and marshes, and acid rain also falls directly into these water sources. While some water sources are naturally more acidic, most lakes and streams have a pH between 6 and 8. As of 2012, acid rain caused 75 percent of acidic lakes and 50 percent of acidic streams, the National Surface Water Survey reports. Some water sources now have a pH of less than 5.

Aquatic Life

Acid rain creates conditions that threaten the survival of aquatic life. Arthropods and fish die in water that has a pH of less than 5. The sensitivity of amphibian eggs to acidity contributes to their decline. While normal lakes might be home to nine to 16 species of zooplankton, acidic lakes retain only one to seven species, reports State University of New York professor Thomas Wolosz. Water with low pH also causes gill damage in fish and death to fish embryos. Reproductive failure is the primary way acid rain causes animal extinction in aquatic systems, says Wolosz. Some affected fish have low calcium levels, which affects reproductive physiology, and some females do not even release ova during mating season in acidic lakes. Also, since the level of carbon dioxide rises in acidic water, the level of carbon dioxide in the blood also increases; thus, oxygen consumption goes up and the rate of growth decreases in animal species. Additionally, bones decalcify due to increased carbon dioxide, which causes deformity in animals.

Bird Life

One less obvious effect of acid rain involves bird life. According to a study by Miyoko Chu and Stefan Hames of the Cornell Lab of Ornithology, acid rain is linked to population decline of the wood thrush. Because female birds require more calcium to solidify their eggs, they rely on calcium-rich foods like snails. In areas of acid rain, snail populations disappear, leading to egg defects for the birds. Both the Cornell Lab and Wolosz cited similar occurrences in the Netherlands, and eggshell defects triggered by acid rain might be the No. 1 cause of loss of bird biodiversity in certain regions.

Other Animals

Acid rain indirectly affects other animals, such as mammals, which depend on animals like fish for food sources. The EPA reports that acid rain causes a reduction of population numbers and sometimes eliminates species entirely, which in turn decreases biodiversity. When one part of the food chain is disturbed, it affects the rest of the chain. The loss of biodiversity affects other species that rely on those animals for food sources. For example, when fish populations are depleted in certain lakes, mammals like bears or even humans who eat those fish need to find alternate sources of food; they can no longer survive in their current environment. More directly, according to, breathing acid particles causes respiratory problems like asthma, bronchitis and pneumonia in humans.

Acid Rain: Scourge of the Past or Trend of the Present?

Acid rain. It was a problem that largely affected U.S. eastern states. It began in the 1950s when Midwest coal plants spewed sulfur dioxide and nitrogen oxides into the air, turning clouds--and rainfall--acidic.

As acid rain fell, it affected everything it touched, leaching calcium from soils and robbing plants of important nutrients. New England's sugar maples were among the trees left high and dry.
Acid rain also poisoned lakes in places like New York's Adirondack Mountains, turning them into a witches' brew of low pH waters that killed fish and brought numbers of fish-eating birds like loons to the brink.

Then in 1970, the U.S. Congress imposed acid emission regulations through the Clean Air Act, strengthened two decades later in 1990. By the 2000s, sulfate and nitrate in precipitation had decreased by some 40 percent.

Has acid rain now blown over? Or is there a new dark cloud on the horizon?

In findings recently published in the journal Water Resources Research, Charles Driscoll of Syracuse University and the National Science Foundation's (NSF) Hubbard Brook Long Term Ecological Research (LTER) site in New Hampshire reports that the reign of acid rain is far from over.
It's simply "shape-shifted" into a different form.

Hubbard Brook is one of 26 NSF LTER sites across the nation and around the world in ecosystems from deserts to coral reefs to coastal estuaries.

Co-authors of the paper are Afshin Pourmokhtarian of Syracuse University, John Campbell of the U.S. Forest Service in Durham, N.H., and Katharine Hayhoe of Texas Tech University. Pourmokhtarian is the lead author.

Acid rain was first identified in North America at Hubbard Brook in the mid-1960s, and later shown to result from long-range transport of sulfur dioxide and nitrogen oxides from power plants.
Hubbard Brook research influenced national and international acid rain policies, including the 1990 Clean Air Act amendments.

Researchers at Hubbard Brook have continued to study the effects of acid rain on forest growth and on soil and stream chemistry.

Long-term biogeochemical measurements, for example, have documented a decline in calcium levels in soils and plants over the past 40 years. Calcium is leaching from soils that nourish trees such as maples. The loss is primarily related to the effects of acid rain (and acid snow).

Now, Hubbard Brook LTER scientists have discovered that a combination of today's higher atmospheric carbon dioxide (CO2) level and its atmospheric fallout is altering the hydrology and water quality of forested watersheds--in much the same way as acid rain.

"It's taken years for New England forests, lakes and streams to recover from the acidification caused by atmospheric pollution," says Saran Twombly, NSF program director for long-term ecological research.

"It appears that these forests and streams are under threat again. Climate change will likely return them to an acidified state. The implications for these environments, and for humans depending on them, are severe."

Climate projections indicate that over the 21st century, average air temperature will increase at the Hubbard Brook site by 1.7 to 6.5 degrees Celsius, with increases in annual precipitation ranging from 4 to 32 centimeters above the average from 1970-2000.

Hubbard Brook scientists turned to a biogeochemical model known as PnET-BGC to look at the effects of changes in temperature, precipitation, solar radiation and atmospheric CO2 on major elements such as nitrogen in forests.

The model is used to evaluate the effects of climate change, atmospheric deposition and land disturbance on soil and surface waters in northern forest ecosystems.

It was created by linking the forest-soil-water model PnET-CN with a biogeochemical sub-model, enabling the incorporation of major elements like calcium, nitrogen, potassium and others.
The results show that under a scenario of future climate change, snowfall at Hubbard Brook will begin later in winter, snowmelt will happen earlier in spring, and soil and stream waters will become acidified, altering the quality of water draining from forested watersheds.
"The combination of all these factors makes it difficult to assess the effects of climate change on forest ecosystems," says Driscoll.

"The issue is especially challenging in small mountain watersheds because they're strongly influenced by local weather patterns."

The Hubbard Brook LTER site has short, cool summers and long, cold winters. Its forests are made up of northern hardwood trees like sugar maples, American beeches and yellow birches. Conifers--mostly balsam firs and red spruces--are more abundant at higher elevations.

The model was run for Watershed 6 at Hubbard Brook. "This area has one of the longest continuous records of meteorology, hydrology and biogeochemistry research in the U.S.," says Pourmokhtarian.
The watershed was logged extensively from 1910 to 1917; it survived a hurricane in 1938 and an ice storm in 1998.

It may have more to weather in the decades ahead.
The model showed that in forest watersheds, the legacy of an accumulation of nitrogen, a result of acid rain, could have long-term effects on soil and on surface waters like streams.
Changes in climate may also alter the composition of forests, says Driscoll. "That might be very pronounced in places like Hubbard Brook. They're in a transition forest zone between northern hardwoods and coniferous red spruces and balsam firs."

The model is sensitive to climate that is changing now--and climate changes expected to occur in the future. 

Acid Rain Effects on Humans and Plant Life

Acid rain has no direct effect on humans, but the pollutants in the rain do damage human health.  Acid rain has the ability to harm us by being in our atmosphere, as well as the soil where we grow our food.  These gases form fine sulfate and nitrate particles by interacting in our atmosphere. These particles can be transported very long distances by winds, and inhaled deep into people’s lungs. When inhaled, they cause damage to the respiratory organs by attacking the membranes in them, which increases the chances of respiratory diseases.  In areas of elevated levels of fine particles there has been an increase in illness and premature death do to heart and lung disorders, such as asthma and bronchitis.  Acid rain results in toxic metals breaking loose from the chemical compounds they occur in naturally.  These toxic metals are then able to get into the drinking water, and the animals or crops that we humans use as sources of food.  This contaminated food can damage the nerves in children, or result in severe brain damage, or even death.

Acid rain affects plant life in two different ways.  One way it affects plants is by seeping into the earth and dissolving toxic substances in the soil which gets absorbed by the roots of plants and trees, poisoning them.  Acid rain also dissolves beneficial minerals and nutrients in the soil, which are then washed away before the plants and trees have a chance of using them in order to grow.  When there is frequent acid rain, it corrodes the waxy protective coating on the leaves, making the plant susceptible to disease.  When the leaves are damaged, the plant loses its ability to produce enough amounts of nutrition to stay healthy. Once the plant has become weak, it becomes vulnerable to cold weather, insects, and disease, which can lead to its death.

Thursday, August 24, 2017

What Is Ocean Acidification?

The oceans have reduced the effects of global warming for thousands of years by absorbing carbon dioxide. Now the basic chemistry of the oceans is changing because of our activities, with devastating consequences for marine life.

What Causes Ocean Acidification?

It's no secret that global warming is a major issue. A main cause of global warming is our release of carbon dioxide, primarily through the burning of fossil fuels and the burning of vegetation.

Over time, the oceans have helped this problem by absorbing excess carbon dioxide. According to NOAA, the oceans have absorbed nearly half of the fossil fuel emissions we've generated over the past 200 years.

As the carbon dioxide is absorbed, it reacts with the ocean water to form carbonic acid. This process is called ocean acidification. Over time, this acid causes the pH of the oceans to decrease, making ocean water more acidic. This can have drastic consequences on corals and other marine life, with cascading impacts on the fishing and tourism industries.

More About pH and Ocean Acidification

The term pH is a measure of acidity. If you've ever had an aquarium, you know that pH is important, and pH needs to be adjusted to optimal levels for your fish to thrive. The ocean has an optimal pH, too. As the ocean becomes more acidic, it becomes more difficult for corals and organisms to build skeletons and shells using calcium carbonate.

In addition, the process of acidosis, or buildup of carbonic acid in body fluids, may affect fish and other marine life by compromising their ability to reproduce, breathe and fight diseases.
How Bad is the Ocean Acidification Problem?

On a pH scale, 7 is neutral, with 0 the most acidic and 14 the most basic.

The historical pH of sea water is about 8.16, leaning on the basic side of the scale.The pH of our oceans has fallen to 8.05 since the beginning of the Industrial Revolution. While this may not seem like a big deal, this is a change greater in magnitude than any time in the 650,000 years before the Industrial Revolution. The pH scale is also logarithmic, so that slight change in pH results in a 30 percent increase in acidity.

Another problem is that once the oceans get their "fill" of carbon dioxide, scientists think the oceans could become a carbon dioxide source, rather than a sink. This means the ocean will contribute to the global warming problem by adding more carbon dioxide to the atmosphere.
Effects of Ocean Acidification on Marine Life

The effects of ocean acidification can be dramatic and far-reaching, and will affect animals such as fish, shellfish, corals, and plankton. Animals such as clams, oysters, scallops, urchins and corals that rely on calcium carbonate to build shells will have a difficult time building them, and protecting themselves as the shells will be weaker.

In addition to having weaker shells, mussels will also have a reduced ability to grip as the increased acid weakens their byssal threads.

Fish will also need to adapt to the changing pH and work harder to remove acid out of its blood, which can impact other behaviors, such as reproduction, growth and food digestion.

On the other hand, some animals such as lobsters and crabs may adapt well as their shells become stronger in more acidic water. Many of the possible effects of ocean acidification are unknown or still being studied.

What Can We Do About Ocean Acidification?

Lowering our emissions will help the ocean acidification problem, even if that just slows the impacts long enough to give species time to adapt. Read the Top 10 Things You Can Do to Reduce Global Warming for ideas on how you can help.

Scientists have acted swiftly on this issue. The response has included the Monaco Declaration, in which 155 scientists from 26 countries declared in January 2009 that:

    Ocean acidification is accelerating and severe damages are imminent;
    Ocean acidification will have broad socioeconomic impacts, affecting marine food webs, causing substantial changes in commercial fish stocks and threatening food security for millions of people;
    Ocean acidification is rapid, but recovery is slow;
    Ocean acidification can be controlled only by limiting future atmospheric carbon dioxide levels.

The scientists called for intense efforts to research the problem, evaluate its impacts and cut emissions drastically to help curb the problem.

The Causes and Impact of Acid Rain

Examining the Impact of Acid Rain Forests and Wildlife Worldwide

Acid rain is a very real phenomenon worldwide, and it's been documented since the 1800s, as the Industrial Revolution caused the burning of fossil fuels like coal, gas, and oil. When these fuels or any other organic material like wood or paper are burned, they release compounds like sulfur dioxide (SO2) and nitrous oxides (NOx) into the air.
The Causes of Acid Rain

Are SO2 and NOx the causes of acid rain?

Indirectly, yes. When SO2 and NOx enter the atmosphere, they react with water vapor, oxygen, and other compounds to form sulfuric acid and nitric acid. This process may take place locally, or -- when winds blow emissions hundreds of miles away -- across international or state boundaries. These acids lower the pH of water condensation in the atmosphere, and when that condensation falls as rain, fog or snow, the resulting acids can wreak havoc on plant and animal life.

(Note: The more acids found in rain, the lower the pH. The pH scale goes from 0 to 14. Values from 0 to 6 are considered acid, 7 is considered neutral, and values from 8 to 14 are considered alkaline. A pH of 1, for example, is far more acidic than a pH of 6.)

The Effects of Acid Rain on Wildlife

The effects of acid rain can vary depending on where it falls and what the local rock and soil are composed of. An alkaline soil can help buffer the effects of acid rain and reduce its impact on local lakes.

However, when acid rain falls on some soils, the acids can wipe out important microbes and insects that live in soil and leaf litter. When acids from rain and snow enter rivers and lakes, it can kill fish and their eggs -- many fish eggs can't survive at pH lower than 5.

This has caused the disappearance of some fish like brook trout from streams in the eastern U.S., where acid rain is more prevalent than in western states.

Crayfish, clams, amphibians and other aquatic wildlife are also killed off by acid rain.

The Effects of Acid Rain on Forests

Trees are among the most visible victims of acid rain. When acid rain or snow falls on forest floors, it leaches out valuable nutrients that are found in the soil, leaving behind aluminum and other elements that can be toxic to plant life. Thus, the trees slowly die from lack of food and from soil toxins -- eventually, an entire forest can be killed off by acid rain.

Trees are especially vulnerable at higher altitude, since they receive more rain and snow, and are often surrounded by acid fog and clouds. The effects of acid rain and snow have been widely seen throughout the Appalachian Mountains, including the Great Smoky Mountains, the Adirondack Mountains and the Catskills in New York. Many forests in Europe, including Germany's famous Black Forest and the high-altitude forests throughout Scandinavia, are also in peril due to acid rain and snow.

The Effects of Acid Rain on Human Health

The amount of acid in rain is too small to have a serious impact on human health, and agricultural land is now amended with lime and other fertilizers to buffer the effect of acid rain.

However, the acid in rain and snow is strong enough to erode rock -- centuries-old buildings, monuments, and statues made of marble, limestone or other rock are slowly eroding away due to the effects of acid rain.

What Can Be Done About Acid Rain?

Though much has been done to reduce the impact of acid rain, much more needs to be accomplished. Smokestack scrubbers that reduce emissions from coal-generated power plants have helped, but with millions of sources like auto tailpipe emissions, sources of acid rain are difficult to manage.

And though international treaties have been signed and implemented throughout Europe and North America, their benefits have been limited, especially as rapidly developing countries in Asia and South America rely heavily on coal and oil for energy. Since the single largest source of acid rain and snow is coal-powered electrical plants, developing alternative sources of energy becomes more important than ever.

Until that time, however, acid rain will continue to destroy trees, forests, wildlife and historical buildings and monuments.

People who are concerned about acid rain can start by saving electricity in their homes, improving their gas mileage and taking other steps to save energy and reduce our dependence on the fossil fuels that cause acid rain.

Acid Rain Intensifies Threat To Marine Life

Human-generated carbon dioxide in the atmosphere is slowly acidifying the ocean, threatening a catastrophic impact on marine life. And just as scientists are starting to grasp the magnitude of the problem, researchers have delivered more bad news: Acid rain is making things worse.

Scientists estimate that one-third of the world’s acid rain falls near the coasts, carrying some 100 million tons of nitrogen oxide, ammonia, and sulfur dioxide into the ocean each year. Using direct measurements and computer models, oceanographer Scott Doney of Woods Hole Oceanographic Institution and his colleagues calculated that acid rain causes as much as 50 percent of the acidification of coastal waters, where the pH can be as low as 7.6. (The open ocean’s pH is 8.1.)

The findings increase the urgency of confronting the crisis of ocean acidity, says Richard Feely, a collaborator at the National Oceanic and Atmospheric Administration. In the laboratory, researchers have seen some effect on just about every ocean creature that forms a calcium carbonate shell, says Feely, including algae—the tiny creatures at the crucial bottom of the deepwater food chain—and coral, whose skeletons grow more slowly in water with a pH even slightly lower than normal. Soon-to-be-released field experiment findings “seem to be showing the same kind of thing,” Feely says. That’s bad news, he adds, since a third of the world’s fish species depend in part on coral reefs for their ecosystems.

Monday, May 15, 2017

Scientists Hunt for Acid Rain and Methane in Wetlands


Depending on how you look at it, something good can always come out of something bad. That's actually the case in a new study on greenhouse gases by NASA scientists and others. The researchers discovered that acid rain inhibits a swampland bacteria from producing methane, a greenhouse gas. 

Animation above: This movie from the U.S. Environmental Protection Agency highlights the science of acid rain, and its effects. Click arrow on bottom right to move to next image. Credit: U.S. EPA

Methane, a gas that contributes to warming our planet, is produced by natural processes and human activities. Increased amounts of methane and other greenhouse gases in our atmosphere are warming the Earth beyond its average temperature. 

Carbon, heat and moisture are known to influence methane production by members of the Archaea, single-celled creatures. Under normal conditions, these microbes consume organic carbon in the soil for energy and release methane as a byproduct. Wetlands provide an ideal environment for these microbes. When acid rain drops sulfate onto wetlands, another type of bacteria, ones that reduce sulfate are able to outcompete the Archea, limiting the total production of methane. 

Wetlands may produce as much as 320 million tons of methane annually but only about half of that, or 160 million tons, is ultimately released to the atmosphere. The other 160 million tons never makes it to the atmosphere because it is destroyed via oxidation as it moves from wet soils below the water table through dry soil to the surface. Despite substantial oxidation, natural wetlands remain the single largest source of methane emission accounting for about one third of the global annual total methane.

Image of a seasonal wetland in Spring
Image to right: Inland wetlands are most common on floodplains along rivers and streams. Scientists have discovered that acid rain actually inhibits a bacteria found in swamplands from producing methane, a greenhouse gas. Inland wetlands include marshes and wet meadows dominated by herbaceous plants, swamps dominated by shrubs, and wooded swamps dominated by trees. Credit: U.S. EPA Region 1/Leo Kenney

"It's a complicated process because multiple factors at microscopic to global scales interact in these processes," said Elaine Matthews, a scientist at NASA's Goddard Institute for Space Studies (GISS), New York. Matthews is co-author of the study on acid rain and methane in wetlands. "The maximum emission of methane from wetlands occurs when conditions are warm and wet, while the biggest reduction in methane emissions is achieved when the location of wetlands, sulfates contained in acid rain, high temperatures and substantial precipitation all come together, to reduce optimal methane emissions from wetlands." These factors vary over time and space. 

According to Matthews, by 1960 these counteracting processes probably reduced methane emission from wetlands to pre-industrial levels. However, methane emission is predicted to rise in response to 21st century climate change faster than sulfate suppression increases, meaning that wetland emissions of methane will begin to rise above those occurring before industrial sulfate pollution began.

In order to determine how the acid rain interacts with methane in wetlands, lead author of the study, Dr. Vincent Gauci of Open University, United Kingdom and his colleagues took to the field. In the U.S., Britain and Sweden they attempted to determine if low levels of sulfate, like those in acid rain, affected methane emissions in wetlands. They applied several quantities of sulfate, similar to the amounts found in acid rain, to the wetlands they were studying. The results, acquired over several years, showed that these low doses of sulfate suppressed methane emissions between 30-40 percent. 

Image of a Riparian wetland
Image to left: Coastal wetlands in the United States, as their name suggests, are found along the Atlantic, Pacific, Alaskan, and Gulf coasts. They are closely linked to our nation's estuaries, where sea water mixes with fresh water to form an environment of varying salinities. The salt water and the fluctuating water levels (due to tidal action) combine to create a rather difficult environment for most plants. Credit: U.S. EPA Region 8/Paul McIver

Matthews and climate experts expect methane emissions to increase over the 21st century in response to climate change. They also predict that sulfate levels in rainfall will increase, especially in Asia. The authors have attempted to predict how this ecological balancing act will turn out for the 21st century. 

"When we used all the field data with the NASA computer models and applied it to a global scale, it shows that the effect of acid rain from 1960 to 2030 actually reduces methane emissions to below pre-industrial levels," said Gauci. The effect more than compensates for the increase in methane emission that would be expected as wetlands become warmer. In this way, acid rain acts like a temporary lid on the largest methane source. 

Gauci is cautious about the image presented by acid rain. "We wouldn't want to give the impression that acid rain is a good thing - it has long been known that acid rain damages natural ecosystems such as forests, grasslands, rivers and lakes. But our findings suggest that small amounts of pollution may also have a positive effect in suppressing this important greenhouse gas. Moreover, they point to how complex the Earth system is," he noted.

Graphic image of a wetland food web
Image to right: Wetlands are among the most productive ecosystems in the world, comparable to rain forests and coral reefs. An immense variety of species of microbes, plants, insects, amphibians, reptiles, birds, fish, and mammals can be part of a wetland ecosystem. Physical and chemical features such as climate, landscape shape (topology), geology, and the movement and abundance of water help to determine the plants and animals that inhabit each wetland. The complex, dynamic relationships among the organisms inhabiting the wetland environment are referred to as food webs. Credit: U.S. EPA/ Mark Sharp

Most attention has been given to the negative aspects of pollution but if scientists want to understand all of Earth's complexities and make better predictions of future climate we need to understand interactions among a suite of processes that are not always well understood. "That's not to say that acid rain is a good thing. Rather this study illuminates really well how we have to work to understand relationships among microscopic-to-global processes, at the same time that we attempt to represent them in relatively simple ways," Matthews said. 

While sulfate deposition results almost exclusively from human activities, it may serve to delay impacts from the increase of at least one greenhouse gas, methane, in the short term. The study recently appeared in the Proceedings of the National Academy of Sciences.

NASA's Science Directorate works to improve the lives of all humans through the exploration and study of Earth's system, the solar system and the Universe.