8th Grade Lab Science (Cribb & Duane)
Home Up Lab Notebook Content Units Science Archives Site Map

 

Chapter 16

What’s Out There?  Mixtures, Compounds, & Elements Found in Nature

 

GREEK ELEMENTS

The ancient Greeks were always observing the natural world and proposing theories about nature.  They were the world’s first scientists – albeit without glitzy technology, lab coats, and ‘geeky-looking’ glasses.  Based on their observations of nature, they reasoned that all the matter on earth consisted of only four elements – fire, air, water and earth.  Different combinations of those four basic elements comprised all of the substances on earth.  The ancients didn’t have the benefits of using tools such as X-rays, particle accelerators, cathode ray tubes, electricity, or even the periodic table to fashion their views – not to mention about 2,500 years of accumulated scientific advancements.  What they did have was their powers of observations and an undying curiosity about nature.  The Greeks definitely had it wrong with regards to fire, as fire is not a substance.  It is a release of energy.  Otherwise, they weren’t that far off base.  Look out the window and describe what you see.  You probably see the remaining three of ancient’s elements – earth, water, and air.  The Greeks were simply a bit misguided in the sense that these aren’t elements as much as mixtures found in the natural world around us. 

 

MIXTURES IN NATURE

We are surrounded by mixtures.  Mixtures, combinations of substances that are not chemically combined, are everywhere.  In fact, rarely are the substances that you come across pure.  You can even think of yourself as a mixture.  You are comprised of combinations of water, organic compounds, inorganic minerals, and dissolved gases.  We depend upon this world of mixtures for our very existence.  We breathe the mixture air, drink liquids that consist of watery solutions, walk on the ground made up of mixtures of soil and rock, and eat other plants and animals that are mixtures in their own right.  From some of these mixtures, humanity may refine and purify substances for some industrial or commercial purpose.  More often than not, pure substances are refined, not naturally occurring.  It is rare to find pure substances in nature. 

 

LEVELS OF ORGANIZATION IN NATURE

Let’s review for a brief moment.  Mixtures consist of elements and compounds sharing the same space.  Generally, we call this matter.  As you know, matter at its most basic level consists of indivisible atoms.  Subatomic particles make up those atoms.  Atoms of separate elements bind together to form molecules, the basic unit of a compound.  Compounds become more complex as the number of atoms and number of chemical bonds increase.  The most complex of these compounds form long molecular chains that include the element carbon.  These complex compounds are the building blocks of living things.  Since they pertain to living things, these compounds are called organic compounds.  The following table describes the levels of organization in nature.  As you move along the chain, the system becomes more complex.

 

Figure 16.1 Levels of Organization in Nature

Subatomic particles --> atoms --> molecules --> complex organic molecules

 

This leads us to the questions: What are the compounds and elements that make up natural mixtures?  What compounds and elements do you experience in the natural world?  What atoms and molecules surround us?  To answer that, we are going to return to the elements of the ancients – earth, air, and water.

 

EARTH

The surface of the earth around us consists of soil and rock.  Weather, climatic events, and volcanic activity sculpt landforms out of soil and rock.  It reveals a dynamic landscape on which life thrives.  Soil and rocks are both types of mixtures.  They are rarely pure.  Because they are mixtures, they consist of pure substances such as elements and compounds.  The elements and compounds found in rock and soil depend upon the specific type of bedrock, and upon interactions with living things.  In geology, these elements and compounds are also called minerals.  We will start with compounds and elements found in the bedrock of the earth’s crust.

 

Bedrock

Bedrock is the solid layer of continuous rock that makes up the earth’s crust.  It is either exposed or covered by soil and sediment.  The elements found in the bedrock of the earth’s crust consist primarily oxygen, silicon, aluminum, and iron.  The table below lists other main elements found in the bedrock of the earth’s crust.  

Table 16.1: Abundant Elements in the Earth’s Crust

Element

Symbol

Percent by Weight

Oxygen

O

46.6 %

Silicon

Si

27.7 %

Aluminum

Al

8.1 %

Iron

Fe

5.0 %

Calcium

Ca

3.6%

Sodium

Na

2.8%

Potassium

K

2.6%

Magnesium

Mg

2.1%

 

The specific kind of bedrock varies from place to place on the planet, and can be igneous, a metamorphic, or a sedimentary in nature.  Igneous rocks form through the solidification of molten material from the earth’s interior.  They are born from cooling magma and lava.  Examples of igneous rocks include granite and basalt.  Sedimentary rocks form from the consolidation of layers of fragments and sediments that are deposited on the earth’s surface.  Some sedimentary rocks have particles that range greatly in size.  Sedimentary rocks include conglomerate, sandstone, limestone, and shale.  Limestone consists of the compound calcium carbonate (CaCO3).  The third group of rock, metamorphic, is formed form the two other rock groups.  Metamorphic rocks form when other rocks are transformed through great heat and pressure.  This usually occurs deep in the earth’s crust.  Examples of metamorphic bedrock are slate, marble, gneiss, and schist.  Marble is a limestone that is transformed under great heat and pressure.

The list of specific igneous, sedimentary, and metamorphic rocks that make up the earth’s crust are not pure substances.  In essence, rocks are mixtures made up of pure substances called minerals.  Minerals are the specific elements and compounds that make up the bedrock.  They are pure substances because they have their own characteristic properties.  Minerals are also referred to as the building blocks of rocks.  Quartz, feldspar, copper, talc, rhodonite, pyrite, limonite, garnet, and mica are all examples of minerals that compose different rocks.  Those minerals make up the igneous, metamorphic, and sedimentary rock formations that comprise the bedrock of the earth’s crust.  Most rocks are an aggregate of different minerals – a mixture. 

 

Soil

Sometimes bedrock is exposed to the effects of weather and climate.  More typical however, bedrock is usually covered by layers of soil, and deposits of clay, sand, and gravel.  The elements and compounds found in the soils and deposited material above the bedrock derive from the bedrock.  Identifying the compounds and elements in the bedrock indicates the type of substances found in the soil above.  The formation of the soil depends upon the bedrock, but it also depends upon interactions with living things.

Soil forms as pieces of bedrock weather and break into small pieces.  The smallest particles that break apart are the clays, the next largest are the silts, and the largest are sands.  Soils are mixtures of clays, silts, and sands.  Sand usually is made of the compound silicon dioxide (SiO2).  Spaces between these particles fill with air and water.  Plants, animals, and micro-organisms such as bacteria inhabit soil.  As living things die and decompose, their living tissue is transformed to humus, the rich organic matter that gives some soils its dark color.  Soil is a mixture of all these substances.  It consists of the sands, silts, and clays that derive from the bedrock and rich organic matter.  Filling the spaces are water and air, both other mixtures found in nature.

 

AIR

To some ancient Greeks, air is an element.  You know it better as a gaseous mixture of compounds and elements.  Our atmosphere consists of a mixture of air that sustains life on the planet.  The layer of air at the earth’s surface has an optimal temperature and pressure that allows life to exist and evolve.  In addition, air contains essential compounds and elements that living things need.  Without the mixture of air that shrouds our planet, we wouldn’t be here.

 

Composition of Air

Air does not have its own characteristic properties.  Instead, the compounds and elements that make up air retain their own characteristics.  The substance that we need directly from the air to stay alive is oxygen. We breathe air to acquire oxygen (O2), but that isn’t the primary component of air.  Nitrogen (N2) is actually the most abundant element in air.  However, nitrogen is not directly useful for us when we breathe.  We breathe it in, and breathe it out.  Nitrogen is important for all living things, but it needs to be transformed into another form.  Bacteria do most of the work in making nitrogen “useful” to other living things. 

Air mostly consists of nitrogen and oxygen but there are other important substances found in air.  The most important of these in regards to living things is carbon dioxide (CO2).  Plants need carbon dioxide to carry out photosynthesis.  Photosynthesis is the process by which plants convert the energy of sunlight into sugar.  In other words, plants carry out photosynthesis to make food from sunlight.  Carbon dioxide is a necessary component for this reaction.   Carbon dioxide is also a “greenhouse gas” – a substance that absorbs heat, and keeps the surface of planet earth warmer than it should be given our position in outer space.  The increased level of carbon dioxide levels in our atmosphere over the last century is a contributing factor to global warming and is becoming a major concern.  Our atmosphere also provides a major reservoir for water.  Although the atmosphere is a useful source of water for living things, water vapor that we “feel” as humidity and see as clouds in the sky makes up small proportion of our air.  Air also consists of the compound methane, which is another “greenhouse” gas, and the element, argon.  A relative comparison of the quantities of each of the components of air are listed in the table below.

 

Table 16.2: Composition of Air

Substance

Symbol

Percent of Air

Nitrogen

N2

78 %

Oxygen

O2

21%

Carbon dioxide

CO2

< 1%

Methane

CH4

< 1%

Water Vapor

H2O

< 1%

Argon

Ar

< 1%

 

There are other substances found in the air we breathe.  Unfortunately, many of these substances can be harmful for living things.  They result from the industrial and economic activities of humans.  We generally call these substances, pollution.

 

Air Pollution

Human activities such as the burning of coal to generate electricity, the driving of an automobile, the manufacturing of chemicals and products, all spew pollutants into our atmosphere.  In the atmosphere, those particles become a part of the mixture of air.  Sometimes, those pollutants remain in the air for a very long period of time.  Pollutants are defined as substances that are man-made and cause some harm to living things.  They are not natural.  Air pollution consists of particulate matter that can be very small or relatively very large in size.  Regardless, pollutants are pure substances that retain their own characteristic properties.  They include both elements and compounds.  When these substances are released by factories and machines, they become a part of the gaseous mixture of air that fills the atmosphere.

In New England, a good deal of the pollutants in the air blow in from the area of the Midwest, but this immediate area also produces a substantial amount of air pollution.  The automobile is a source of pollution that is spread out over our entire area.  Recent technology has lessened, but not eliminated the amount of pollution that cars release into the atmosphere.  Carbon monoxide (CO) and ozone (O3) are two pollutants that result from a gasoline powered internal combustion engine.  The excess carbon dioxide that cars produce is also considered a pollutant since it changes the balance of substances in the atmosphere.  Ozone is a byproduct of a photochemical reaction.  “Photochemical” means that the reaction involves light.  At the upper reaches of our atmosphere, ozone is a good thing, since the earth’s ozone layer blocks harmful ultra-violet rays from reaching the earth’s surface.  At the surface of the earth however, ozone is harmful to living things.  It can be especially damaging to lung tissue.  On especially bad days, we can see ozone as a haze or smog that fills the lower atmosphere. 

Other pollutant substances found in the air we breathe include sulfur dioxide (SO2) and nitrogen dioxide (NO2).  Sulfur dioxide is a pollutant that results from the burning of coal.  Much of the sulfur dioxide in the air of New England is a result of the burning of coal for electricity generation in the Midwest.  Sulfur dioxide arrives with the prevailing winds.  In our atmosphere, sulfur dioxide undergoes a chemical reaction with water whose product is sulfuric acid (H2SO4), which is one of the causes of acid rain.  

The manufacturing process also releases pollutants into the air.  Lead (Pb) and mercury (Hg) are both byproducts of the manufacture of such things as paint, paper, and chemicals. Hydrogen fluoride (HF) is a substance that is created by the process of creating petroleum-based fertilizers.

 

Table 16.3: Sources of Major Air Pollutants

Pollutant

Symbol

Source

Sulfur dioxide

SO2

Burning of coal and other sulfur-containing fuels mainly for electricity

Nitrogen dioxide

NO2

High temperature combustion

Ozone

O3

Photochemical reaction from automobiles

Large particulate matter

----

Fuel combustion

Carbon monoxide

CO

Gasoline engines

Hydrogen fluoride

HF

Manufacturing of fertilizers

Lead

Pb

Manufacturing of paint; smelting operations

Mercury

Hg

Manufacturing of paper, chemicals, and paint

Sulfuric acid

H2SO4

Chemical reaction in atmosphere between water and SO2

 

The hidden message is that as representatives of the developed world, the lifestyle we enjoy, and the products we use, come at a cost.  That cost includes the unwanted particles that are released.  Left unchecked, those pollutants have the potential to do much damage to all living things.

 

WATER

Water is another essential substance for living things.  A good deal of the water on earth however, is salty, and a useless source for most terrestrial living things.  Water is found in its liquid state in the natural environment at the earth’s surface in the form of rivers, streams, lakes, and oceans.  Salt water of the ocean accounts for 97% of the planet’s water.  Beneath the earth’s surface, there is a vast aquifer the stores ground water.  There is also a large amount of water stored as ice on the earth’s surface.  This solid reservoir of water that is held in the world’s glaciers makes up the largest store of freshwater on the planet.  Water on earth is mixed with many other substances.   Those substances depend upon the location of the water resource.

Water Resources

Water and land interact to form wetlands.  Wetlands can be vernal pools, marshes, bogs, and swamps.  In a broader sense, they include ponds and lakes.  Certain species of bacteria thrive in oxygen-deprived marshes, and produce smelly hydrogen sulfide (H2S) and methane.  Wetlands also are mixed with the similar organic matter that is found in the soil.

As you know, water consists of hydrogen and oxygen.  Also as you know, there are spaces between the individual water molecules.  In those spaces, other substances dissolve.  In water sources, those other substances usually include the gases oxygen and carbon dioxide.  Water resources also dissolve whatever soluble minerals are found in the bedrock.  The action of fast moving rivers and streams erode and carry these minerals great distances.  Excess minerals can give water sources different tints of color.  In the fall and spring, there is a natural mixing of the substances dissolved in the water.  This is because of the fall and spring overturn that circulates the water via convection currents as the temperature changes.

 

Water Pollution

Like the air, the water mixtures of the planet are threatened by pollution.  In many ways, water resources are at a greater risk to pollution than the air since it serves as a natural sink for most substances.  Although the list of possible pollutants in the water is similar to that of air, there are some additions to the list of pollutant substances.  These include the element arsenic, as well as chlorinate-containing compounds PCB’s and DDT.   Those substances are found in some pesticides insecticides.  In this country, DDT was banned in the 1970’s but it is still used for mosquito eradication programs in developing countries.  Water resources also contain the nitrates and phosphates that come from fertilizers and are released by sewage treatment plants.

To protect a water resource, we must consider the entire watershed.  The watershed for a water resource encompasses the entire land area that drains into the water source.  Any substance found on the land in the area of the watershed, eventually makes its way into the surface water.  Rainfall over an entire area watershed runs off into the rivers, lakes, and streams, carrying substances with it.  Because of this dynamic, the effects of acid rain caused by sulfuric acid pollutants in the atmosphere, is potentially lethal to living things in water supplies.  Acid rain has lowered the pH of many bodies of water in the US and Canada.  Because New England is downwind of many large utility plants in the Midwest, our local waters are particularly vulnerable to acid rain.  If rain and substances don’t flow into the surface water supply, they are leeched into the vast ground water supply. 

 

LIVING THINGS

You can think of yourself as a mixture.  You, like all living things, are comprised of combinations of water, organic compounds, inorganic minerals, and dissolved gases.  The ‘mixture’ that you are, is highly organized and structured – that’s the magic of being living thing, but in its essence, you’re just a mixture.   Someone once calculated the total market value of the substances that make us up to be $0.49!

All living things – plants, animals, micro-organisms, can all be thought of as mixtures that are comprised of simple and complex compounds, and elements.  Look across the landscape and you see living things populating every nook and cranny.  Our landscape is dominated by trees in the woods, grasses in the fields and marshes, fish in the rivers, birds in the sky, micro-organisms in the soil, and animals hiding everywhere.  The mixture of substances that make up living things is the site for energy transformations and chemical reactions.  When living things no longer convert energy and carry out chemical reactions, they are dead!  The leftover substances are then mixed with the surrounding soil and water of the environment – ashes to ashes!

Because of the chemical reactions and energy transformations, living things are distinct from non-living things.  We are not going to detail the differences between “living” and “non-living” in this space.  Instead, we are going to detail the compounds and elements that make up living things.  Those substances can be either organic – pertaining to living matter, or inorganic – substances not created by living things, but used by living things.

 

Inorganic Substances

To carry out a complex array of reactions and energy transformations, living things need inorganic minerals that include both elements and compounds.  Below is a list of major and minor elements found in living things.  Some of these substances exist as part of more complex compounds.  Some are simply materials needed for chemical reactions within living things.

 

Table 16.4: Elements in living things

Major Elements (> 1% dry weight)

Trace Elements (< 1% dry weight)

H    Hydrogen

Ca     Calcium

C     Carbon

Cl      Chlorine

O    Oxygen

Cu     Copper

N    Nitrogen

Fe     Iron

P     Phosphorous

Mg    Magnesium

 

K       Potassium

 

Na    Sodium

 

S      Sulfur

 

I       Iodine

 

Inorganic minerals in living things are simple structured compounds and single atoms.  Different living things have different concentrations of these substances, but as a whole, the list of substances across the spectrum of living things remains consistent.  For example, iron (Fe) is an important component of human blood.  In horseshoe crabs, copper (Cu) is an important element found in their blood.  Horseshoe crabs and humans have essentially the same elements, but different quantities of those elements.  In a side note, because of the copper, horseshoe crabs have blue blood.  I guess all the blue bloods don’t live on Beacon Hill!

The essential inorganic compounds that living things need include carbon dioxide and water.  In fact, living things consist mostly of water – 90% of all living things are water!  Plants need both substances in order to carry out photosynthesis.

The inorganic compounds and elements in living things are all, molecularly speaking, simple.  They are simple atoms and molecules.  Yet, living things also consist of much more complex compounds that are arranged in a way that makes life possible.  These complex compounds are types of organic compounds.

 

Organic Substances: Biological Compounds

Organic compounds are the building blocks of living things.  As individual molecules, these compounds are not “living”.  Together however, these compounds are arranged into living cells, which are the smallest unit of a living thing that is technically “alive”.  Organic compounds consist of complex molecules that are very large by molecular standards.  Because of their size and their complexity, life is able to evolve out of these inanimate substances.  The level of complexity of these substances stems from the unique qualities of the element, carbon.  All organic compounds contain carbon atoms.

“Organic” means pertaining to living things.  Therefore, organic compounds are compounds that are produced by living things.  All organic compounds contain the elements carbon (C) and hydrogen (H), and most also contain oxygen (O).  Some organic compounds also contain the elements nitrogen, (N), phosphorous (P) and sulfur (S).  These elements make up the compounds that constitute living things.  One main group of organic compounds include the biological compounds: carbohydrates, proteins, lipids, and nucleic acids.

Carbohydrates include sugars and starches.  The basic unit of a carbohydrate is a glucose molecule (C6H12O6).  Glucose is the simplest sugar.  Names of other sugars include fructose, galactose, maltose, sucrose, and lactose.  As you can tell, the ending “ose” means sugar.  If you deconstruct the word “carbohydrate” it becomes easy to remember the names of the elements in the molecule – “carbo” (carbon) “hydr” (hydrogen) “ate” (oxygen).  Remember, the ending “ate” means oxygen. 

Like carbohydrates, lipids contain only the elements carbon, hydrogen, and oxygen.  These molecules are very large and complex arrangements of those elements.  Fats and oils are types of lipids.

Proteins also contain carbon, hydrogen and oxygen.  In addition, all proteins also contain the element nitrogen.  Some proteins also contain phosphorous and / or sulfur.  Those elements join to form amino acids.  There are twenty different kinds of amino acids in nature.  Amino acids combine to form the seemingly infinite variety of proteins that are found in all living things. 

A fourth group of organic compounds is nucleic acids.  One nucleic acid is called deoxyribose nucleic acid.  You probably know it better as DNA!  DNA molecules are found in all living things.  It is a very complex molecule that contains a sugar (deoxyribose) linked to a phosphate (P & O) connected by nitrogenous bases (contain N).  The structurally, DNA is shaped like a ladder that wraps around itself.  Science names this shape a “double helix”.

The organic compounds that make up living things are identical to our nutritional needs.  In other words, they are what we eat.  Biological compounds are also called the nutrients of those foods.  Food consists of varying quantities of carbohydrates (sugars and starches), lipids (fats and oils), and proteins.  Together, these substances provide energy and raw materials for living things.

At this point, it’s okay to compare living things to mixtures that are made up of combinations of organic compounds and inorganic minerals.  The truth of the matter is that life is much more than complex than that. Being considered simply a "mixture", does not do justice to the complex interactions of materials and energy that is life. 

 

WHAT’S OUT THERE?  COMPOUNDS & ELEMENTS OF CONCORD!

The compounds and elements that are outside your door make up the living things, the earth, air, and water that you observe daily.  When you look at a living thing, you see organic compounds made up of combinations of C, H, O, N, and P & S.  Looking at rocks, you see Si and O, at the air, N, O, and CO2.  Water is H20, and full of nitrates and phosphates as well.  Up to this point, we have been speaking in generalities.  There are however unique qualities about the place where you live that will make the list of compounds and elements found in the immediate natural world more specific.  Let’s start with the earth and soil.

 

LOCAL GEOLOGY (EARTH)

New England is a “mineral poor” region.  “Mineral poor” means that there is little economic incentive to mine and extract minerals from the earth.  In other words, the minerals around here are not worth much money.  But what minerals are there in this area?

Southeastern New England rests on a layer of bedrock that consists of slate, schist, gneiss, marble, granite, and conglomerate.  The Concord River watershed sits on a formation of bedrock that is called Dedham granite.  Granite is an igneous rock made up of the minerals mica, feldspar, and quartz.  Chemical notation for quartz is SiO2.

Most of the area’s bedrock is hidden by glacial clay, sand, and gravel.  Those materials were deposited at the end of the last ice age more than 10,000 years ago.  The melting ice pack resulted in two large glacial lakes - Glacial Lake Assabet and Glacial Lake Sudbury.  Both lakes filled with sediment that compressed the clay and sand.  Actions of the glaciers during the last ice age sculpted the landscape that you see today.  Large boulders carried by glaciers and deposited as the glacier retreated are called glacial erratics.  The compounds of these boulders traveled a great distance, and may not be endemic to the local area.

Local soils are a mix of clay, sand, and silt and organic matter called humus.  The substances that make up the soil derive from the underlying bedrock.  In general, the local soil contains a good amount of nutrients that can support agriculture and forests.  However, due to a good number of rocks imbedded in the soil, farming in New England has always been a challenge.  Seasonal cycles of freezing and thawing break up underlying layers of bedrock that reaps an annual harvest of rocks.  Many of these harvested rocks make up the ubiquitous stone walls that dot our landscape.

Soils are classified according to their structure and composition.  The two soil types indigenous to this area include alfisols and spodosols.  Alfilsols are soils of deciduous forests.  They are relatively fertile, medium brown, and rich in iron and aluminum.  Spodosols are young, acidic soils of cool, moist coniferous forests.  Both soil types are found in the local area.  Iron in the soil reacts with oxygen to form a compound known as iron oxide (FeO).  Iron oxide has a reddish brown color.  You probably know iron oxide as a common substance, rust.  Streams that run through iron-rich soils tend to adopt a reddish brown color.  This brings us to a discussion of the water resources of the local area.

 

THE SUDBURY, ASSABET, & CONCORD (SuAsCo) WATERSHED (WATER)

The Concord River begins at the confluence of the Sudbury and Assabet Rivers.  Both rivers’ sources are in the town of Westborough.  The entire watershed of the three rivers is known as the SuAsCo (an acronym for Sudbury – Assabet – Concord), and eventually flows into the Atlantic Ocean via the Merrimack River.  The basin was originally populated by the Nipmuck Indians who used the river system as a highway and a source of fish.  The subsistent Woodland culture that the Nipmucks developed eventually succumbed to epidemics of disease and an influx of English settlers. 

The English colonists took advantage of the waterpower of the flowing rivers and established mills along the banks.  The first mills were constructed to grist grain into flour.  Later, saw mills and fulling (finishing handwoven cloth) mills were established.  The wastes from these economic activities flowed downstream throughout the river system.  In addition to industrial wastes, the communities that developed adjacent to mill complexes utilized the rivers as a sewer.  Those communities include the present day towns of Northborough, Hudson, Stowe, Maynard, West Concord, Saxonville (Framingham), Billerica, and Lowell.  Today, sewage treatment plants from Hopkinton, Shrewsbury, Westborough, Marlborough, Hudson, Maynard, and Concord empty effluent into the Assabet River.  In addition, twelve licensed industries, ranging from the Raytheon Corporation to MCI Concord, and the Billerica House of Corrections discharge wastewater into the Sudbury, Assabet, and Concord Rivers.

Key plants have been upgraded, and effluent from plants must meet national clean water standards.  Treatment does not eliminate surplus nutrients – compounds containing nitrogen and phosphorous, that support abundant vegetative growth.  Such pollutants also wash into the rivers from area lawns and farms.

The Division of Water Pollution Control of the Massachusetts Department of Environmental Protection monitors the current water quality of the SuAsCo watershed.  The state designates each of the rivers in the watershed as a class B inland water.  A rank of class B means that you can swim, fish, and boat in the water.  The rank is based on bacteria levels, oxygen content, and temperature.  

A class B designation allows fishing, but there can be toxins found in the fish of the watershed.  This stems from minute levels of some toxins that are found in the sediment and consumed by micro-organisms.  These toxic chemicals become concentrated in organisms higher up in the food chain.  As a result, there are high levels of mercury measured in fish caught in the Sudbury River.  The acceptable safe level for mercury is 1 part per million.  Some Sudbury River fish have mercury levels twelve times greater.  As a result, there are signs warning people against eating fish caught in the Sudbury River.  The source of mercury contamination is a toxic waste dump in Ashland that was created by a series of dye manufacturers. 

Water quality throughout the watershed has improved in recent years due to the actions of local governments, conservation organizations, and cooperating industries.  The watershed is significantly cleaner toady than it was a century ago.

 

THE AIR WE BREATHE (AIR)

As already mentioned, air consists mostly of oxygen and nitrogen.  In addition, there are higher concentrations of some pollutants in the air we breathe to due the geographic fact that we are downwind to major industrial centers and metropolitan areas. 

Sulfur dioxide, produced by coal burning electricity plants travels great distances through the atmosphere.  In New England, sulfur dioxide arrives from the Midwest with the prevailing westerly winds.  In the atmosphere, sulfur dioxide reacts with water to form the acid rain that falls locally and collects in lakes and ponds that have no outlets.  Acid rain has significantly lowered the pH of lakes in streams in New England and eastern Canada. 

Low elevation ozone is another concern for this area.  The major metropolitan areas of the east coast have high concentrations of automobiles that produce ozone via a chemical reaction in the atmosphere.  This problem is particularly acute during the hot days.  Ozone produced from the Washington – New York City metropolitan area, combines with locally produced ozone to hamper air quality in the greater Boston area.  Local authorities monitor ozone levels and warn citizens of air alert days. 

 

LOCAL FLORA & FAUNA: THE SOUTHERN NEW ENGLAND FOREST ECOSYSTEM

The living things indigenous to the local environment inhabit this place due to a myriad of factors.  The factors of latitude and geography combine to form a temperate climate that mixes species from the mid-Atlantic region with northern species from Canada and the sub-Arctic.  In other words, New England is a crossroads – the tip of the northern range for southern species of flora and fauna, and the tip of the southern range for northern species.  As a result, New England forests provide a great diversity of living things.  The main types of forests in New England include coniferous forests that are characteristic of the boreal ecosystem; the northern broadleaf forest; mixed pine and oak forests found to our south; and the forests that encompass qualities of all these.

Massachusetts lies within the Southern New England forest.  These woods are a mixture of deciduous and coniferous trees that form a patchwork of northern and southern species.   The Concord River basin specifically lies in a transitional forest belt.  This transitional forest is the dominant forest type in central New England.  The transitional forest blends the northern broadleaf forest to our immediate north and oak, hickory, and pine forests characteristic of Connecticut and southeastern Massachusetts. 

Maple, birch, and beech forests, white pine woods, hemlock woods, oak – hickory forests, and pine and oak woods all mix within this transitional forest.  The types of trees found in a specific area are determined by topography, as subtle difference between sun, moisture, and soil interact to influence the species found in a specific locale.

Deciduous woodlands of maple, birch, and beech species hold a dark fertile soil rich in minerals and humus.  The leaf-littered understory is coated with shrubs, wildflowers, and seedlings.   White pine woods grow on drier, sandier soils.  Litters of pine needles that carpet the forest floor suppress other plant growth.  This is because pine needles are acidic, and low in phosphorous, calcium, and potassium – elements essential to plant growth.  Hemlock woods occupy cooler, moist areas found in ravines and shady hillsides.  Pines and oaks grow in impoverished sandy soil.  Pine-oak woodlands are characteristic of Cape Cod and Southeastern Massachusetts, but they make inroads into the Concord River basin.  Dry woods that once were open fields are occupied by hickory – oak forests.  These forests have re-claimed the expanse of agricultural land that once blanketed eastern Massachusetts.  Ground cover of these forests include ferns, wild flowers, and shrubs.

Local forests sustain a population of animals that include white-tailed deer, common raccoons, and eastern gray squirrels.  The eastern coyote has returned to the area along with wild turkeys and beavers.  In addition, there are reports of moose and cougars frequenting our region.

All of the living things that inhabit our region – plants, fungi, animals, and micro-organisms, consist of the same organic compounds.  Those compounds include, carbohydrates, proteins, lipids, and nucleic acids.  The fact that all living things consist of similar compounds is one of the characteristics that distinguishes life from non-life.

 

 

horizontal rule

BIBLIOGRAPHY

Alden and Cassie, National Audubon Society Field Guide to New England.  Alfred A. Knopf Inc. New York, NY, 1998.

Cunningham and Saigo, Enviornmental Science: A Global Concern.  Wm. C. Brown Publishers, Boston, MA, 1995.

Kupchella and Hyland, Environmental Science: Living Within the System of Nature.  Prentice Hall, Englewood Cliffs, NJ, 1986.

McAdow, The Concord, Sudbury, and Assabet Rivers: A Guide to Canoeing, wildlife, and History.  Bliss Publishing Company, Inc. Marlborough, MA.  1990.

Wessels, Reading the Forested Landscape. The New England Press, Keene, NH, 2001