Chapter 2 ~ Water, Soil, and Air Quality

This image shows distinct measures for testing water, soil, air quality.
This image shows three distinct examples of quality testing. (From left to right.) Water quality testing is conducted by Southeastern Louisiana University graduate students. Soil quality is accessed by a health and safety specialist in the 9th ward after Hurricane Katrina. Air quality is impacted by the oil refinery emissions in Meraux, Louisiana. “Water quality testing” by Adronisha Frazier is licensed under CC BY 4.0. “Industrial Health and Safety Specialist Shaune Gilbert takes a soil sample from the 9th ward levee break” by the EPA is licensed under CC0. “Oil refinery” by Wes Muller is licensed under CC BY-NC-ND 4.0.

Key Terms

Water pollution, eutrophication, toxins, stratosphere, troposphere, mesosphere, UV-radiation, hydrosphere, contaminants, chlorofluorocarbons, organic pollutants, inorganic pollutants, ozone depletion, acid rain

Learning Objectives

Upon completion of this chapter, students will be able to:

  • Explain the hydrologic cycle and its importance for living organisms.
  • Classify the different types of water and their availability for human consumption.
  • Explain the world’s environmental need for water management to prevent water scarcity.
  • Identify how water is being polluted.
  • Explain how burning fossil fuel contributes to pollutants in the environment.
  • Acknowledge how air quality management is important for a clean and healthy atmosphere.

Chapter Overview

  • Introduction
  • Global Water Distribution and Use
  • The Hydrologic Cycle
  • Water Scarcity and Shortage
  • Water Pollution
  • Soil
  • Air and Atmosphere
  • Ozone Depletion
  • Acid Rain
  • The Montreal Protocol
  • A Louisiana Perspective—Water Quality

Introduction

Water is a very important commodity for human life and survival. We need to consume it to stay alive and use it to clean our food, utensils, clothes, bodies, and surroundings to prevent disease. Unfortunately, this same water is responsible for about 80% of all diseases in developing countries and over three million deaths a year globally. Soil is essential and one of the crucial oikos (home) of living organisms. Its composition determines the distribution of plant and animal species while determining the physical and chemical nature of rocks, landforms, and rivers. The major natural water flows are controlled by soil type and also flow of water, and chemical components between the atmosphere and hydrosphere are solely determined by soil. It is also a source of many gases (such as oxygen and carbon dioxide). Soil not only has a profound effect on human civilization but also influences the economic and cultural heritage of that particular location. Soil holds the food prints of the past, and agriculture shapes the economic growth of land life (Mishra et al. 2012). Atmosphere refers to the layer of gases that surrounds Earth and is held in place by Earth’s gravitational attraction (gravity). The mix of gases in the atmosphere forms a complex system organized into layers that together support life on Earth. It is therefore very important that we understand why these important commodities can be vital and at the same time cause so much harm. This chapter is devoted to the availability and quality of water, soil, and air. Water, soil, and air quality will be defined as the physical, chemical, and biological properties of these vital components of the environment that impact its intended use. This definition recognizes that quality designations of any can vary depending on the purpose it is serving.

Global Water Distribution and Use

About 71% of the Earth’s surface is covered by water, most of which is in oceans and unavailable for human consumption due to its high salinity (Figure 2.1). Approximately 97% of all water is saline, and 2% is fresh water held in ice caps and glaciers. Therefore, at least 99% of all water is generally unsuitable for human use because of salinity (ocean water) and location (ice caps and glaciers), leaving less than 1% of total water as fresh water that is available for consumption. Of this available fresh water, approximately 97% is groundwater stored deep below the surface of the Earth, and only 1.4% is surface water in rivers and lakes.

Figure 2.1. Distribution of Earth’s water (USGS via Wikimedia in the public domain)

Three main sectors use water—industrial, agricultural, and domestic. When water is removed from its source, such as a river or lake, and returned to this source after use, this is referred to as non-consumptive use. An example is when water is used in industrial cooling, it may be temporarily placed in cooling ponds and later returned to the river or lake from which it came. Consumptive use is when water is taken out from a source and consumed by plants and animals or used in industrial processes. The water enters animal tissue or becomes part of industrial products or evaporates during use and is not returned to its source. Of the three sectors, the agricultural sector is by far the largest user of water that is never returned to its sources, consumptive use. The largest percentage of water withdrawn in the US goes to thermoelectric cooling (Figure 2.2).

Figure 2.2. Estimated 2015 water withdrawals in the US. Irrigation and thermoelectric power usage account for most water withdrawals (USGS in the public domain)

Water is being used at very high rates worldwide due to human population growth and industrialization. As more countries become affluent (increase in industrialization and standard of living), they consume more water than they did when they were less industrialized. To find out more about global water use, check out the world water use meter.

The Hydrologic Cycle

The major water reservoirs on Earth are oceans, ice caps and glaciers, groundwater, rivers, and lakes. Water spends different amounts of time in the various reservoirs. The main factors that control the amount of time water stays in a reservoir are the amount of water in the reservoir and how fast water moves in and out. The hydrologic cycle (water cycle) represents a continuous global cycling of water from one reservoir to another (Figure 2.3). This process is powered by two major forces—heat energy from the sun that causes liquid water to change to water vapor and the gravitational pull of the Earth that brings water to the surface.

 

This image shows the hydrologic cycle at the global scale.
Figure 2.3. This image shows the many different paths of Earth’s water cycle. For example, the sun heats up liquid water in the ocean, causing it to evaporate from Earth’s surface and rise into the atmosphere as water vapor. As the water vapor cools, it condenses into liquid water droplets to form clouds and falls again to the surface as precipitation. Precipitation is the scientific term for rain, snow, or hail. Source: Water Cycle Board Game | NESDIS (noaa.gov)

To gain a deeper appreciation of the water cycle, let us follow a water molecule through the water cycle. Starting in the ocean (an arbitrary starting point), the water molecule can become part of the water that is converted into vapor and enter the atmosphere. Evaporation is the process by which water changes from a liquid to a gas or vapor. Evaporation is the primary pathway that water takes from the liquid state back into the water cycle as atmospheric water vapor. Nearly 90% of moisture in the atmosphere comes from evaporation, with the remaining 10% coming from transpiration. Transpiration is the process by which moisture is carried through plants from roots to small pores (stoma) on the underside of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves. Rising air currents take the vapor up into the atmosphere, along with water from evapotranspiration, which is a combination of water transpired from plants and that evaporated from the soil. The vapor rises into the air where cooler temperatures cause it to condense into clouds. Condensation is the process by which water vapor is converted from a gaseous state back into a liquid state. Clouds might eventually grow bigger and moist enough to release the water molecule in the form of precipitation. Precipitation is water falling from the clouds in the atmosphere in the form of ice (snow, sleet, hail) or liquid (e.g., rain, drizzle). Precipitation that falls as snow can accumulate as ice caps and glaciers.

Precipitation that falls as liquid usually ends up as surface flow and stream flow. Surface runoff is the portion of precipitation that travels over the soil surface to the nearest stream channel. Stream flow is the movement of water in a natural channel, such as a river. Most precipitation falls directly onto the ocean and returns the water molecule back to restart the journey. This is also true for surface runoff: most of the water eventually returns to the ocean via stream flow. This also returns the water molecule back to the ocean to start the journey again. A portion of the water that falls as precipitation can enter lakes where it can evaporate back into the atmosphere, condense into clouds, and fall back as precipitation again. Water in the lake can also be taken up by aquatic plants and transpired back into the atmosphere. Some of the water that falls as precipitation can infiltrate into the ground and become part of groundwater. Infiltration is the process by which water enters the subsurface by gravitational pull. Some of the water infiltrates into the ground and replenishes aquifers (saturated subsurface material), which store huge amounts of freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as groundwater discharge, while some groundwater finds openings in the land surface and emerges as freshwater springs. Water that stays in the soil closer to the surface can be absorbed through plant roots and transpire from the leaves. Over time, though, all this water keeps moving, and most of it ends up in the ocean.

Components of the Hydrologic Cycle

As demonstrated in Figure 2.3, the hydrologic (water) cycle has multiple components. This section defines the processes and terminology from Figure 2.3 and introduces additional terminology, such as floodplains and wetlands.

Precipitation is water released from clouds in the form of rain, freezing rain, sleet, snow, or hail. It is the primary connection in the water cycle that provides for the delivery of atmospheric water to the Earth. Rain forms as water vapor in a rising air mass condenses in the cloud and forms water drops. Condensation is the process in which water vapor in the air is changed into liquid water. Condensation is crucial to the water cycle because it is responsible for the formation of clouds. These clouds may produce precipitation, which is the primary route for water to return to the Earth’s surface within the water cycle. Condensation is the opposite of evaporation.

Most precipitation falls in the form of rain. There are three main kinds of rain: frontal, convective, and orographic. Frontal rainfall is precipitation formed when two air fronts of different temperatures and moisture content converge. Convective rainfall is formed when intense localized heating causes hot, moist air to raise and condense and form rain clouds. Intense rain would then fall as the clouds became supersaturated. Orographic rainfall is rain that forms over mountains. When a moist air mass encounters a mountain, it rises and cools. As it cools, water vapor condenses to form a rain cloud that produces rain on the windward side of the
mountain. Most of the rain ends up as surface water runoff. Surface water is a major component of the hydrological cycle and one that we interact with very regularly. It includes lakes, wetlands, stormwater runoff (overland flow), ponds, potholes, rivers and streams, and the ocean.

A river forms from water moving from higher to lower altitude (elevation) under the force of gravity. When rain falls on the land, it can seep into the ground, become runoff (water running on the surface), or evaporate. Water that moves as runoff on the land surface usually converges as it moves toward lower elevation. The converging runoff can concentrate into single channels of conveyance called creeks, streams, or rivers. Usually these start as small rills and rivulets that would join up downhill into larger creeks, which then become streams that later join up downstream to form even bigger channels referred to as rivers. The streams and small rivers that join up to form a larger river are called tributaries. The land area drained by a river and all its tributaries is called a watershed or catchment or river basin.

Map of the major river systems within the Mississippi River Basin.
Figure 2.4. The Mississippi River Watershed shows the connecting rivers and nearby land in the United States. A hypoxic zone is created in the Mississippi Delta due to water pollution from the drained rivers’ surface runoff.

The flat area adjacent to a river is called a floodplain. Floodplains are characterized by frequent flooding, a means by which rivers temporarily store excess water during storm events. Flooding delivers nutrients to the soil, making most floodplains very fertile areas. This has historically encouraged humans to move into floodplains and use them for agriculture and other land uses, resulting in a reduction in the capacity of the floodplain to act as temporary storage for excess water during storm events, increasing the intensity of floods in downstream locations. Human structures such as buildings and roads can reduce infiltration and water-storage capacity of floodplain soils, leading to increased flood frequency and intensity. Some agricultural practices, such as rice farming, are typically not associated with these negative impacts and are therefore not restricted in most floodplains. Properly functioning floodplains reduce the negative impacts of floods (by reducing severity of flood), and they assist in filtering stormwater and protecting the water quality of rivers. They also act as areas of recharge for groundwater.

The United States of America (US) has numerous rivers that run throughout the nation’s landscape. It is estimated that the US has over 200,000 rivers with the Mississippi River being the largest by volume despite it only being the second longest. The Missouri River is the longest river in the US. Most states have at least one important river. In Louisiana, the main rivers are the Atchafalaya, Calcasieu, Mississippi, Ouachita, Pearl, Red, and Sabine Rivers (Figure 2.5).

 

This image shows the rivers in Louisiana.
Figure 2.5. The rivers, streams, lakes, and reservoirs in Louisiana contribute to the watershed. Source: GISGeography

If water flows to a place that is surrounded by higher land on all sides, a lake will form (Figure 2.6). A lake, pond, or reservoir is a body of standing water on the land surface. When people build dams to stop rivers from flowing, the lakes that form are called reservoirs. It is estimated that over 300 million water bodies in the world are lakes, reservoirs, and ponds. Most of the Earth’s lakes (about 60%) are found in Canada. Even though lakes and rivers contain less than 1% of the Earth’s water, the US gets over two-thirds (70%) of its water (for drinking, industry, irrigation, and hydroelectric power generation) from lakes and reservoirs. Lakes are also the cornerstone of the US’s freshwater fishing industry and are the backbone of the nation’s state tourism industries and inland water recreational activities.

This true color satellite image shows Lake Pontchartrain.
Figure 2.5. This true-color satellite image shows Lake Pontchartrain in the center with the St. Tammany and Tangipahoa Parishes to the North and St. John the Baptist, St. Charles, Jefferson, and Orleans Parishes. Lake Maurepas is pictured to the left.

A wetland is an area that is home to standing water for notable parts of the year, has saturated soils for a large part of the year, and has plants that are adapted to surviving under flooded conditions or in saturated soils. They are transitional areas between the terrestrial land and the aquatic environments such as rivers, lakes, and oceans. Some major wetland types include swamps (dominated by trees), marshes (dominated by non-woody plants), and bogs (dominated by moss). Wetlands are identified using three characteristics: soils (water-saturated soils are present), hydrology (shallow water table), and vegetation (wetland plants that are adapted to areas that are saturated with water for long periods of time). Wetlands are very important areas of biological diversity and productivity. These are also important areas where geochemical and biological cycles/processes are constantly taking place. For instance, wetlands are considered areas of significant carbon sequestration (storage), which impacts global climate change. They also act as filters for stormwater runoff before it enters rivers and lakes.

As you have probably already guessed, oceans are an important component of the hydrologic cycle because they store the majority of all water on Earth (about 97%). Approximately 90% of the water that is evaporated into the hydrologic cycle comes from the ocean. Oceans are an important and large part of the hydrologic cycle, with lots of biological diversity and many landforms. Most of the major rivers drain into them. The five oceans covering the surface of the Earth are the Atlantic, Indian, Pacific, Arctic, and Southern Ocean (Figure 2.6).

This image shows the world map of the oceans.
Figure 2.6. The five oceans found on Earth are pictured here. The Pacific Ocean is the largest ocean.

Water Scarcity and Shortage

Water scarcity and shortage have been identified as major environmental crises facing the world today. More than one billion people in the world lack access to clean drinking water. The water demand has grown at a very fast pace in response to the rate of global population growth. Figure 2.6 illustrates this change in water use over time in the United States of America (US). It is predicted that over the next two decades, the average supply of water per person will drop by a third. When looking at the trends in the figures below, you will notice some encouraging leveling off or slight drop in use in recent years.

Figure 2.6. Trends in fresh and saline water withdrawals in response to population growth (USGS in the public domain)

Can you think of reasons for these observations?

Both groundwater and surface water withdrawals had increased over time until 1980 when the withdrawals peaked and stabilized. Water withdrawals in the US show a major divide between the western and eastern parts of the country. The western part withdraws most of the water for agriculture, as these are the farm areas, while the eastern half withdraws most of its water for thermoelectric cooling and industry (Figure 2.7). California and Texas account for over 20% of all water withdrawn. California consumes more water than is available within the state and is therefore forced to get water from other states. Despite this deficiency, almost everyone in California has access to clean and safe drinking water. Contrast this to Lusaka, the capital city of Zambia, which has more water available than is withdrawn, but more than a third of its population has no access to safe drinking water.

Figure 2.5. Water withdrawal trends by usage (USGS in the public domain)

There is enough fresh water on Earth to supply every human being with enough drinking water. The main problem we face with regard to water is that it is unevenly distributed, polluted, mismanaged, and wasted. Tony Allan, the author of Virtual Water, asserts that water follows the money. This refers to the fact that rich countries and societies with more money and affluence have more access to safe drinking water even when they live in regions without much water. It also means that areas with large supplies of water can still have water scarcity if they lack the financial resources and infrastructure to supply people with clean and safe drinking water. Water scarcity is caused by the demand for water or a certain quality being greater than the supply. Scarcity can be defined as either physical scarcity or economic scarcity.

Physical water scarcity is a situation where there is an actual shortage of water, regardless of quality or infrastructure. It is estimated that about 1.2 million people around the world are experiencing physical water scarcity. Economic scarcity is a condition where countries lack the financial resources and/or infrastructure to supply their citizens with reliable safe drinking water. About 1.6 billion people are experiencing economic water shortage; most of them live in less industrialized countries. For a lot of places in the world, scarcity is a transient condition that can be reduced or eliminated by installing the right infrastructure. The major problem in less industrialized countries is the lack of political, financial, and physical structures to provide water to everyone. A few rich people in these countries get clean water while the majority of the people who cannot afford to pay for it are left out. Examples of such communities include many villages in Africa, Asia, and South America. Figure 2.6 shows communities in southeast Kenya that are experiencing severe water shortages primarily due to a lack of infrastructure coupled with physical scarcity. Women and children in these communities must walk long distances to get untreated and contaminated water for drinking and other household needs (Mutiti et al. 2010).

 

Figure 2.6. Communities in southeast Kenya without ready access to safe drinking water. (A) Groundwater in the area is too salty for consumption. (B) Maasai women in Amboseli National Park collect water from a wetland. (C) Women in Magwede Village in SE Kenya walking long distances to get water from a kiosk. (D) Children collecting water in Bungule Village from a water kiosk that is only open for about an hour every day. Photo credit: Jonathan Levy, Sam Mutiti, and Christine Mutiti via 8.5: Water Scarcity and Storage, licensed CC BY-NC-SA 4.0

Water Pollution

Water pollution is a major problem facing many of our surface and groundwater sources.

Contamination can both be natural due to geologic or meteorological events and anthropogenic (human causes). Human sources of contamination can be categorized as either point source or nonpoint source. Point-source pollution is water pollution coming from a single point, such as a sewage-outflow pipe. Non-point source (NPS) pollution is pollution discharged over a wide land area such as agricultural runoff and urban stormwater runoff, not from one specific location. Non-point source pollution contamination occurs when rainwater, snowmelt, or irrigation washes off plowed fields, city streets, or suburban backyards and carries pollutants into the water sources. As this runoff moves across the land surface, it picks up soil particles and pollutants, such as nutrients, toxins such as metals, and pesticides.

Types of Water Pollution

Contamination of water resources comes in the form of chemical, biological, and physical pollution. Chemical pollution includes things such as toxic metals, organic compounds, acidic waters from mining activities and industry, pharmaceuticals, and many other chemical compounds from industries and wastewater treatment plants. Another form of chemical pollution is radioactive waste, which has a significant potential to cause harm to living things. Most of the radioactive pollution comes from agricultural practices such as tobacco farming, where radioactive phosphate fertilizer is used. Physical pollution includes sediment pollution, trash thrown in the water bodies, thermal (temperature), and other suspended loads. High temperatures typically affect the metabolism of aquatic fauna negatively and can encourage eutrophication. Biological pollution usually refers to pathogenic bacteria, viruses, and parasitic protozoa. Common pathogenic microbes introduced into natural water bodies are pathogens from untreated sewage or surface runoff from intensive livestock grazing. Biological pollution is a common cause of illness and death in less industrialized countries where population density, water scarcity, and inadequate sewage treatment combine to cause widespread parasitic and bacterial diseases.

Sources of Surface Water Pollution

Surface water pollution can come from a variety of sources and includes an extensive list of chemical compounds, mixtures, and elements. Below is a short description of some of these sources and the impacts of a few pollutants.

Chemical Pollution

Most of the common inorganic pollutants in water are produced by non-point sources, mainly intensive agriculture, and activities from urban areas. Specific inorganic chemicals and their major sources are ammonium nitrate and a host of related phosphate and nitrogen compounds used in agricultural fertilizers and heavy metals (present in urban runoff and mine tailings area runoff). However, some inorganic contaminants such as chlorine and related derivatives are produced from point sources, ironically employed in water treatment facilities.  Moreover, some of the large dischargers of heavy metals to aquatic environments are fixed-point industrial plants.

High concentrations of nitrogen (N) and phosphorus (P) in water can cause eutrophication. You see this whenever you notice the greenish tint to the water in your local streams and rivers during low-flow times, or if you have ever seen a green farm pond. These nutrients are primarily coming from treated wastewater (laden with P and N) being dumped into main rivers from sewage plants. Another source of high nutrients is agricultural areas where farmers allow livestock direct access to streams and ponds. Urban and suburban areas could be toxic where there is intense fertilizer application for esthetics. Public and private landscapes (homes, gardens, golf courses) may be polluted with fertilizer runoff.

An increased supply of nutrients into an aquatic system leads to alterations of the primary production from low to high. Algal blooms are natural events, and all algae can bloom. Cyanobacteria (blue-green algae) are not always harmful but can produce toxins when conditions allow. The frequency at which conditions for toxic algal blooms’ occurrence have become common lately in coastal areas of the U.S. Harmful algal blooms are possible under prolonged sunlight in summer, high surface water temperatures, and when water stays static in the presence of fertilizer runoff from the surrounding areas. When a bloom occurs, it can be difficult to identify whether or not it is toxic.

The nitrogen and phosphorus act as fertilizers in the water and promote algae blooms. As the algae die, they are decomposed by aerobic bacteria in the water. These bacteria use up the oxygen in the water and the low dissolved oxygen (DO) levels can result in “fish kills” where large numbers of fish, and other aquatic life, die because of suffocation (Figure 2.7).

Figure 2.7. Lake Sinclair, Georgia. From top from left: (A) recreational area with expected accumulation of algae; (B) water clarity loss measured with a Secchi Disk due to an algal bloom. Bottom from left: (C and D) visible algal blooms leading to Fish Kills in some cases. Credits: (A), (B), (C) photo credit: Kalina Manoylov GCSU; (D) Jennifer L. Graham at USGS, as cited in Chapter 8–Water Quality licensed CC-BY-NC-SA 4.0

Improper storage and use of automotive fluids produce common organic pollutants causing water pollution. These chemicals include methanol and ethanol (present in wiper fluid) and gasoline and oil compounds such as octane and nonane (overfilling of gasoline tanks); most of these are considered non-point sources, since their pathway to watercourses is mainly overland flow. However, leaking underground and above-ground storage tanks can be considered point sources for some of these chemicals and even more toxic organic compounds such as perchloroethylene. Grease and fats (such as lubrication and restaurant effluent) can be either point or non-point sources depending upon whether the restaurant releases grease into the wastewater collection system (point source) or disposes of such organics on the exterior ground surface or transports to large landfills. Table 2.1 below shows a summary of some common chemical pollutants and their sources.

Table 2.1. Contaminants and Chemical Compounds in Common Sources

Contaminants / Chemical Compounds

Common Sources

Heavy Metals (lead, chromium, zinc, arsenic, cadmium, mercury, selenium, etc.)

Mines, industries, rocks, power plants

Cations (carbonates, nitrates, phosphates, fluorides, sulfates)

Sewage, wastewater treatment plants, agriculture, fertilizer use

Other Metals (sodium, calcium)

Industry

Pharmaceuticals (medicines, hormones)

Industrial activities, hormones, and hospitals

Pesticides (atrazine, chlordane, DDT)

Agriculture, golf courses, lawns

Organic compounds (benzene, xylene, phenols, trichloroethylene, dioxin, etc.)

Industry, power plants, transformers, gas stations

Radioactive isotopes

Nuclear power plants, Hospitals

Pathogens (bacteria, viruses, protozoan)

Animal farms, sewage, runoff

Physical Surface Water Pollution

The most significant physical pollutant is excess sediment in runoff from agricultural plots, clear-cut forests, improperly graded slopes, urban streets, and other poorly managed lands (especially when steep slopes or lands near streams are involved). Other physical pollutants include a variety of plastic refuse products such as packaging materials; the most pernicious of these items are ring-shaped objects that can trap or strangle fish and other aquatic fauna in our rivers, lakes, and oceans. Oceans house many forms of living things that are uniquely adapted to survive in these salty habitats. Unfortunately, humans have degraded oceans through pollution, overfishing, carbon dioxide acidification, and resource exploitation. Other common physical objects are timber slash debris, wastepaper, and cardboard.

Finally, power plants and other industrial facilities that use natural water bodies for cooling can cause thermal pollution in surface water. Thermal pollution can change the ecology of the water bodies and harm living things. The warm water discharged is usually only used for cooling in the plant and does not contain other contaminants.

Biological Pollution

Common biological pollutants include pathogenic microbes such as bacteria, viruses, protozoa, and helminths. The most frequently encountered bacteria are E. coli, Shigella, Vibrio cholerae, Campylobacter, and species of the genus Salmonella (which variously cause typhoid fever and food-borne illnesses). Common viral pollutants include the Norwalk virus, Enteroviruses, Adenovirus, and Hepatitis A/E, while protozoans are dominated by G. lamblia and species in the genus Cryptosporidium. All these are fecal-oral route parasites often transmitted as water pollutants and are associated with inadequate sanitation. They originate from various sources that include sewage treatment facilities, animal fecal waste, leaky septic tanks, and recreational areas such as swimming pools. In addition, we also have parasitic worms (helminth) and amoeba (protist E. histolytica) that live inside faunal digestive systems for part of their life cycle and are partially spread as water pollutants, with an estimated three billion people currently affected globally.

Groundwater Pollution

Surface water is not the only water source that can get contaminated by the pollutants discussed under surface water. Groundwater can also become contaminated by both natural and anthropogenic sources of pollution. Naturally occurring contaminants are present in the rocks and sediments. As groundwater flows through sediments, metals such as iron and manganese are dissolved and may later be found in high concentrations in the water. Industrial discharges, urban activities, agriculture, groundwater withdrawal, and disposal of waste all can affect groundwater quality. Contaminants from leaking fuel tanks or fuel or toxic chemical spills may enter the groundwater and contaminate the aquifer. Pesticides and fertilizers applied to lawns and crops can accumulate and migrate to the water table.

A Louisiana Perspective – Water Quality

 The Clean Water Act (CWA) establishes regulations for water pollution in the United States (U.S.).  Its goal is to mitigate pollution in the nation’s water to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters”, as described in CWA section 101(a).  However, the assessment of CWA’s legislative limits is enforced by the U.S. Environmental Protection Agency.  Non-point source (NPS) pollution is globally problematic and remains a serious problem in our nation.  Discharges of agricultural fertilizers, pesticides, runoff from construction and dredging activities, and urban infrastructure containing toxic chemicals are all contributors to NPS pollution.  As NPS pollutants flow, they blend into a hazardous concoction, spreading across residential floodplains and reaching numerous river locations. During flooding, the widespread presence of NPS contaminants endangers the well-being of residents, community infrastructure, natural resources, and wildlife habitats.

The NPS pollution has had a significant impact on the estuaries, which are home to a diverse range of wildlife habitats.  The uniqueness of estuaries is seen where the freshwater from rivers and streams mingles with the saltwater from the ocean. These unique areas are teeming with diverse ecosystems and play a crucial role in supporting marine life. Estuaries serve as nurseries for oysters and other shellfish as well as provide natural protection against coastal erosion and storm surges. The Atchafalaya Basin estuary is a vital part of Louisiana’s culture and economy and spans across nearly 1 million acres of lush, wooded wetlands, serving as the focal point of Louisiana’s flourishing seafood industry and rich Cajun heritage.  

Agricultural runoff is a major contributor to water pollution in the U. S.  and introduces nitrogen and phosphorus into water systems, leading to eutrophication?  Eutrophication occurs when an excessive and harmful influx of nitrogen and phosphorus occurs in a water system. This leads to the proliferation of green algae, which consumes oxygen from the water, causing the death of fish and other marine life, and the creation of a dead zone.  In Louisiana, the source of the threat is NPS pollution caused by domestic sewage systems and runoff from farmlands.

In 2017, the Dead Zone in the Gulf of Mexico, resulting from NPS pollution from the Mississippi River, was as large as New Jersey, making it the largest one on record.  In 2020, a shocking revelation was made that over 90% of Louisiana’s waterways were unsuitable for recreational activities and wildlife habitats. This finding is alarming and highlights the urgent need for action to protect our natural resources. The safety and sustainability of Louisiana’s waterways are at stake, and immediate measures must be taken to ensure their protection for future generations.   

Learn More:  Most of Louisiana’s waterways are polluted. Biggest reasons? Fertilizer and sewage | WRKF

 

Soil

The word “soil” has been defined differently by different scientific disciplines. In agriculture and horticulture, soil generally refers to the medium for plant growth, typically material within the upper meter or two (Figure 2.8). We will use this definition in this chapter. Soil consists predominantly of mineral matter but also contains organic matter (humus) and living organisms. The pore spaces between mineral grains are filled with varying proportions of water and air. In common usage, the term soil is sometimes restricted to only the dark topsoil in which we plant our seeds or vegetables. In a broader definition, civil engineers use the term soil for any unconsolidated (soft when wet) material that is not considered bedrock. Under this definition, soil can be as much as several hundred feet thick! Ancient soils, sometimes buried and preserved in the subsurface, are referred to as paleosols and reflect past climatic and environmental conditions.

Figure 2.8. Soil Profile. The photograph shows a soil profile from South Dakota with A, E, and Bt horizons. The yellow arrows symbolize the translocation of fine clays to the Bt horizon. The scale is in feet. Source: University of Idaho and modified by D. Grimley. From 11. Soils from The Ecosphere and Environmental Issues by Sarah Sojka, licensed CC-BY-NC-SA 4.0

How Soil Pollution Affects Plants

Several elements obtained from soil are considered essential for plant growth. Macronutrients, including C, H, O, N, P, K, Ca, Mg, and S, are needed by plants in significant quantities. C, H, and O are mainly obtained from the atmosphere or rainwater. These three elements are the main components of most organic compounds, such as proteins, lipids, carbohydrates, and nucleic acids. The other six elements (N, P, K, Ca, Mg, and S) are obtained by plant roots from the soil and are variously used for protein synthesis, chlorophyll synthesis, energy transfer, cell division, enzyme reactions, and homeostasis (the process regulating the conditions within an organism). Micronutrients are essential elements that are needed only in small quantities but can still be limiting to plant growth, since these nutrients are not so abundant in nature. Micronutrients include iron (Fe), manganese (Mn), boron (B), molybdenum (Mo), chlorine (Cl), zinc (Zn), and copper (Cu). Some other elements tend to aid plant growth but are not essential. Micronutrients and macronutrients are desirable in particular concentrations and can be detrimental to plant growth when concentrations in soil solution are either too low (limiting) or too high (toxicity). Mineral nutrients are useful to plants only if they are in an extractable form in soil solutions, such as a dissolved ion rather than in solid minerals. Many nutrients move through the soil and into the root system as a result of concentration gradients, moving by diffusion from high to low concentrations. However, some nutrients are selectively absorbed by the root membranes, enabling concentrations to become higher inside the plant than in the soil.

Figure 2.8. Soil and plant Nutrient Cycle. The figure illustrates the uptake of nutrients by plants by plants in the forest soil ecosystem. Source: US Geological Survey, in the public domain

Soil Pollution

Accumulation of a higher number of toxic substances, acids, alkaline components, salts, radioactive heavy metals, and generation/increasing number of pathogenic organisms in soil are the leading causes of soil pollution. These accumulations lead to adverse effects on natural water resources, growth and development of vegetation, and negative influence on the health of animals and humans (Cachada et al. 2018). Soil pollutants are grouped into two categories—the organic pollutants (OPs) and the inorganic (IPs) pollutants. Soil pollution is considered as pollution due to human activities and is undertaken as land degradation due to the addition of chemical compounds from various industrial and anthropogenic sources. When the normal presence of these chemicals is increased in environmental soil – as petroleum hydrocarbons and polynuclear aromatic hydrocarbons, pesticides, heavy metals, or other sources such as industrial waste, agricultural, and improper disposal of municipal household waste. A number of new emerging concerns of increasing amounts of synthetic chemicals are constantly being added, and that can change the natural microbial especially pathogenic bacterial population penetration in their system and can cause acquired systemic resistance to commonly used antibiotics to treat pathogenic bacteria. These pharmaceuticals may disrupt the endocrine system and hormones, and can result in toxicity to bacteria, viruses, and small animals (Cai et al. 2021). Another pollutant of concern is nanoplastics; these submicron-sized plastics are ubiquitous in the environment, primarily accumulating through runoff water and depositing in soil; 

Air and Atmosphere

Earth’s atmosphere is divided into four distinct layers based on thermal characteristics (temperature changes), chemical composition, movement, and density (Figure 5.1). The troposphere is the lowest layer extending from the surface up to roughly 18 km above the surface depending on location (varies from as low as 6 km to as high as 20 km). The stratosphere is the layer that extends from the tropopause up to about 50 km to 53 km above the Earth’s surface depending on location. The proportions of most gases in this layer are similar to that of the troposphere with two main exceptions: (1) there is almost no water vapor in the stratosphere and (2) the stratosphere has nearly 1,000 times more ozone (O3) than the troposphere. Above the stratosphere is the mesosphere, which extends to about 85 km above the Earth’s surface. The mesosphere has no ozone molecules, and the other gases such as oxygen and nitrogen continue to become less dense with height. As a result, not much ultraviolet and x-ray radiation from the sun is absorbed by molecules in this layer, so the temperature decreases with altitude. Both the stratosphere and the mesosphere are considered the middle atmosphere. Between about the range of 85 km and 600 km lies the thermosphere. This layer is known as the upper atmosphere. Unlike the mesosphere, the gases in this layer readily absorb incoming high-energy ultraviolet and x-ray radiation from the sun.

Ozone makes up a very small proportion of the gases in our atmosphere, and most of it is concentrated in a portion of the stratosphere roughly 17–30 km above the surface. This region, called the ozone layer, acts as a protective shield that protects life on the surface of the Earth by absorbing most of the harmful portions of the high-energy UV radiation coming from the sun. UV is subdivided into three types, namely UV-A, UV-B, and UV-C (Figure 5.3). Of these three types, UV-A is the least energetic and least harmful but can cause some damage to living cells, resulting in sunburns and skin damage. UV-A is also not absorbed by ozone in the stratosphere and is therefore transmitted through the atmosphere to the surface of the Earth. UV-C is the most harmful and most energetic of all UV but is strongly absorbed in both the thermosphere and the stratosphere and does not make it to the Earth’s surface. UV-C is the one responsible for the splitting of oxygen molecules in the stratosphere, which leads to the formation of ozone. When ozone absorbs UV, it regenerates oxygen atoms and releases heat, which warms the upper part of the stratosphere. Since UV-C does not make it to the Earth’s surface, the most harmful form of UV radiation that reaches the surface is UV-B. However, the amount of UV-B that reaches Earth’s surface is significantly reduced because most of it is absorbed by ozone in the stratosphere. Ozone is the only known gas that absorbs UV-B.

Ozone Depletion

Global ozone concentrations change periodically with regular natural cycles such as changing seasons, winds, and long-timescale sun variations. Concentrations of ozone in the atmosphere are measured in parts per billion (ppb). Scientists have been measuring ozone since the 1920s using ground-based instruments that look skyward. Satellite measurements of concentrations of atmospheric ozone began in 1970 and continue today.

Chlorofluorocarbons (CFCs) are man-made compounds made up of chlorine, fluorine, and carbon. These compounds were commonly used as propellants in everyday products such as shaving cream, hair spray, deodorants, paints, and insecticides and as coolants in refrigerators and air conditioners. CFCs are extremely stable molecules and do not react with other chemicals in the lower atmosphere, which is part of the reason why they were considered a safe choice. Their stability means that they tend to remain in the atmosphere for a very long time. With the constant movement of air in the lower atmosphere, CFCs eventually make their way into the stratosphere. Exposure to ultraviolet radiation in the stratosphere breaks them apart, releasing chlorine atoms. Free chlorine (Cl) atoms then react with ozone molecules, taking one oxygen atom to form chlorine monoxide (ClO) and leaving an oxygen molecule (O2) (Figure 2.9). The ClO reacts with other atoms, freeing up the Cl and making it available to react with another ozone molecule, repeating the cycle over and over resulting in ozone depletion.

Figure 2.9. Ozone destruction. UV radiation frees a chlorine (Cl) atom from a CFC molecule. This atom reacts with ozone and produces an oxygen gas molecule and chlorine monoxide (ClO). ClO reacts with another oxygen atom; it frees up the Cl atom, which then proceeds to destroy another ozone molecule. Source: Brien Sparling via Wikimedia Commons, in the public domain

If each chlorine atom released from a CFC molecule destroyed only one ozone molecule, CFCs would pose very little threat to the ozone layer. However, when a chlorine monoxide molecule encounters a free atom of oxygen, the oxygen atom breaks up the chlorine monoxide, stealing the oxygen atom and releasing the chlorine atom back into the stratosphere to destroy another ozone molecule. These two reactions happen over and over again so that a single atom of chlorine, acting as a catalyst, destroys many molecules (about 100,000) of ozone. The consequence of stratospheric ozone depletion is increased levels of UV-B radiation reaching the Earth’s surface, posing a threat to human health and the environment. Figure 2.10 shows a lower-than-average amount of stratospheric ozone over North America in 1997 when it was abnormally cold compared to 1984, which was warmer than average, showing that ozone depletion does not exclusively affect just the South Pole (Antarctic).

This image shows the largest ozone hole ever detected over Antarctica. This image was captured September 6, 2000.
Figure 2.10 shows the ozone hole over Antarctica on September 6, 2000. It is the largest ozone hole detected since the first detection in 1985. Source: NASA in the public domain

Air Pollution

Air pollution occurs in many forms but can generally be thought of as gaseous and particulate contaminants that are present in the earth’s atmosphere. Chemicals discharged into the air that have a direct impact on the environment are called primary pollutants. These primary pollutants sometimes react with other chemicals in the air to produce secondary pollutants.

Air pollution is typically separated into two categories: outdoor air pollution and indoor air pollution. Outdoor air pollution involves exposures that take place outside of the built environment. Examples include fine particles produced by the burning of coal; noxious gases such as sulfur dioxide, nitrogen oxides, and carbon monoxide; ground-level ozone; and tobacco smoke. Indoor air pollution involves exposure to particulates, carbon oxides, and other pollutants carried by indoor air or dust. Examples include household products and chemicals, out-gassing of building materials, allergens (cockroach and mouse droppings, mold, and pollen), and tobacco smoke.

Sources of Air Pollution

A stationary source of air pollution refers to an emission source that does not move, also known as a point source. Stationary sources include factories, power plants, and dry cleaners. The term area source is used to describe many small sources of air pollution located together whose individual emissions may be below thresholds of concern but whose collective emissions can be significant. Residential wood burners are a good example of a small source, but when combined with many other small sources, they can contribute to local and regional air pollution levels. Area sources can also be thought of as non-point sources, such as the construction of housing developments, dry lake beds, and landfills.

A mobile source of air pollution refers to a source that is capable of moving under its power. In general, mobile sources imply “on-road” transportation, which includes vehicles such as cars, sport utility vehicles, and buses. In addition, there is also a “non-road” or “off-road” category that includes gas-powered lawn tools and mowers, farm and construction equipment, recreational vehicles, boats, planes, and trains.

Agricultural sources arise from operations that raise animals and grow crops, which can generate emissions of gases and particulate matter. For example, animals confined to a barn or restricted area produce large amounts of manure. Manure emits various gases, particularly ammonia into the air. This ammonia can be emitted from the animal houses, manure storage areas, or from the land after the manure is applied. In crop production, the misapplication of fertilizers, herbicides, and pesticides can potentially result in aerial drift of these materials, and harm may be caused.

Unlike the above-mentioned sources of air pollution, air pollution caused by natural sources is not caused by people or their activities. An erupting volcano emits particulate matter and gases, forest and prairie fires can emit large quantities of “pollutants,” dust storms can create large amounts of particulate matter, and plants and trees naturally emit volatile organic compounds that can form aerosols, causing natural blue haze. Wild animals in their natural habitat are also considered natural sources of “pollution.”

Six Common Air Pollutants

The most commonly found air pollutants are particulate matter, ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead. These pollutants can harm health and the environment and cause property damage. Of the six pollutants, particle pollution and ground-level ozone are the most widespread health threats. The U.S. Environmental Protection Agency (EPA) regulates them by developing criteria based on considerations of human and environmental health.

Ground-level ozone is not emitted directly into the air but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOC. Breathing ozone can trigger a variety of health problems, particularly for children, the elderly, and people of all ages who have lung diseases such as asthma. Ground-level ozone can also have harmful effects on sensitive vegetation and ecosystems. (Ground-level ozone should not be confused with the ozone layer, which is high in the atmosphere and protects Earth from ultraviolet light; ground-level ozone provides no such protection.)

Particulate matter, also known as particle pollution, is a complex mixture of extremely small particles and liquid droplets. Particle pollution is made up of several components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles. The size of particles is directly linked to their potential for causing health problems. EPA is concerned about particles that are 10 micrometers in diameter or smaller because those are the particles that generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects.

Carbon monoxide (CO) is a colorless, odorless gas emitted from combustion processes.  Nationally and, particularly in urban areas, the majority of CO emissions to ambient air come from mobile sources.  CO can cause harmful health effects by reducing oxygen delivery to the body’s organs (like the heart and brain) and tissues. At extremely high levels, CO can cause death.

Nitrogen dioxide (NO2) is one of a group of highly reactive gasses known as “oxides of nitrogen,” or nitrogen oxides (NOx). Other nitrogen oxides include nitrous acid and nitric acid. EPA’s National Ambient Air Quality Standard uses NO2 as the indicator for the larger group of nitrogen oxides. NO2 forms quickly from emissions from cars, trucks and buses, power plants, and off-road equipment. In addition to contributing to the formation of ground-level ozone, and fine particle pollution, NO2 is linked with some adverse effects on the respiratory system.

Sulfur dioxide (SO2) is one of a group of highly reactive gasses known as “oxides of sulfur.”  The largest sources of SO2 emissions are from fossil fuel combustion at power plants (73%) and other industrial facilities (20%).  Smaller sources of SO2 emissions include industrial processes, such as extracting metal from ore, and the burning of high sulfur-containing fuels by locomotives, large ships, and non-road equipment. SO2 is linked with many adverse effects on the respiratory system.

Lead is a metal found naturally in the environment as well as in manufactured products. The major sources of lead emissions have historically been from fuels in on-road motor vehicles (such as cars and trucks) and industrial sources.  As a result of regulatory efforts in the US to remove lead from on-road motor vehicle gasoline, emissions of lead from the transportation sector dramatically declined by 95% between 1980 and 1999, and levels of lead in the air decreased by 94% between 1980 and 1999. Today, the highest levels of lead in the air are usually found near lead smelters. The major sources of lead emissions to the air today are ore and metals processing and piston-engine aircraft operating on leaded aviation gasoline.

Indoor Air Pollution (Major Concerns in Developed Countries)

Most people spend approximately 90% of their time indoors. However, the indoor air we breathe in homes and other buildings can be more polluted than outdoor air and can increase the risk of illness. There are many sources of indoor air pollution in homes. They include biological contaminants such as bacteria, molds, and pollen, burning of fuels and environmental tobacco smoke, building materials and furnishings, household products, central heating and cooling systems, and outdoor sources. Outdoor air pollution can enter buildings and become a source of indoor air pollution.

Sick building syndrome is a term used to describe situations in which building occupants have health symptoms that are associated only with spending time in that building. Causes of sick building syndrome are believed to include inadequate ventilation, indoor air pollution, and biological contaminants. Usually indoor air quality problems only cause discomfort. Most people feel better as soon as they remove the source of the pollution. Making sure that your building is well-ventilated and getting rid of pollutants can improve the quality of your indoor air.

Secondhand Smoke (Environmental Tobacco Smoke)

Secondhand smoke is the combination of smoke that comes from a cigarette and smoke breathed out by a smoker. When a non-smoker is around someone smoking, they breathe in secondhand smoke.

Secondhand smoke is dangerous to anyone who breathes it in. There is no safe amount of secondhand smoke. It contains over 7,000 harmful chemicals, at least 250 of which are known to damage human health. It can also stay in the air for several hours after somebody smokes. Even breathing secondhand smoke for a short amount of time can hurt your body.

Over time, secondhand smoke can cause serious health issues in non-smokers. The only way to fully protect non-smokers from the dangers of secondhand smoke is to not allow smoking indoors. Separating smokers from non-smokers (like “no smoking” sections in restaurants)‚ cleaning the air‚ and airing out buildings do not completely get rid of secondhand smoke.

Acid Rain

Pure rainfall is slightly acidic with a pH of 5.6 because water reacts with atmospheric carbon dioxide to produce weak carbonic acid. When higher-than-normal amounts of nitric and sulfuric acid occur in the atmosphere, the result is precipitation with a pH below 5.6, which is referred to as acid rain. Acid rain includes both wet deposition (rainfall, snow, fog) and dry deposition (particulates). Acid rain formation results from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, primarily emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) resulting from fossil fuel combustion. In the United States, roughly 2/3 of all SO2 and ¼ of all NOx come from electric power generation that relies on burning fossil fuels, like coal. Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds (Figure 2.11). The result is a mild solution of sulfuric acid and nitric acid. When sulfur dioxide and nitrogen oxides are released from power plants and other sources, prevailing winds blow these compounds across state and national borders, sometimes over hundreds of miles. Regions of greatest acidification tend to be downwind from heavily industrialized source areas of pollution.

Figure 2.11: Formation of acid rain from both natural and anthropogenic pollutants. Source: US EPA, public domain

The Montreal Protocol

International policy efforts to restrict the production of ozone-depleting CFCs culminated in the 1987 treaty known as the Montreal Protocol in which signing nations agreed to cut CFC production in half by 1998. At least five follow-up agreements since then helped to deepen the cuts, advanced timetables for compliance, and addressed additional ozone-depleting substances such as halons, methyl chloroform, carbon tetrachloride, and hydrochlorofluorocarbons (HCFCs). Most countries around the world have phased out production of the substances covered by the agreements, and industry has been able to shift to safer alternative chemicals. As a result, there’s evidence that the Antarctic ozone hole has stopped growing worse, although recovery is not expected anytime soon. Phasing out CFCs and HCFCs is also beneficial in protecting the earth’s climate, as these substances are also very damaging greenhouse gases.

As part of the United States’ commitment to implementing the Montreal Protocol, the US Congress amended the Clean Air Act (section 5.7), adding provisions for the protection of the ozone layer. Most importantly, the amended act required a gradual end to the production of chemicals that deplete the ozone layer. The Clean Air Act amendments passed by Congress require the Environmental Protection Agency (EPA) to develop and implement regulations for the responsible management of ozone-depleting substances in the United States.

Review Questions

  1. Compare and contrast consumptive and non-consumptive water usage.
  2. Explain the following processes within the hydrologic cycle: precipitation, surface runoff, infiltration, and groundwater flow.
  3. Figure 2.6 shows trends in groundwater and surface along with a plot of the human population. What are your observations from this graph? What can you infer from your observations?
  4. What are two examples of economic scarcity?
  5. How is pollution connected to eutrophication?
  6. What are the forms of UV radiation? Which form is most harmful to humans? Which is least harmful to humans?
  7. What are the impacts of the six common air pollutants in Louisiana?

Critical Thinking / Questions for Discussion

  1. What is the significance of the Montreal Protocol?
  2. Explain the different types of pollution.
  3. How do soil erosion and pollution impact the environment and human health?

Key Terms

  • Acid rain – The wet and dry deposition of acidifying substances from the atmosphere.
  • Chlorofluorocarbons – Man-made compounds containing carbon, hydrogen, chlorine, and fluorine that cause ozone layer depletion.
  • Contaminants – An addition of a substance from an external source that makes something impure.
  • Eutrophication – Increased primary productivity of an aquatic ecosystem, resulting from nutrient inputs.
  • Hydrosphere – The parts of the planet that contain water, including the oceans, atmosphere, land, surface waterbodies, underground, and organisms.
  • Inorganic pollutants – Pollutants derived from non-carbon-based sources.
  • Mesosphere – The layer of the atmosphere extending beyond the stratosphere to about 75 km above the surface of the Earth.
  • Organic pollutants – Pollutants derived from carbon-based sources.
  • Ozone depletion – Decline in the concentration of ozone molecules in the atmosphere.
  • Stratosphere – The upper atmosphere, extending above from 8–17 km to as high as about 50 km.
  • Toxins – Substances that cause harmful impacts upon exposure to animals, humans, and the environment.
  • Troposphere – The lower atmosphere, extending to 8–17 km.
  • UV-radiation – A physical agent that is associated with photons and capable of causing negative impacts on animals, humans, and the environment.
  • Water pollution – An introduction of harmful agents in water bodies that can be detrimental to animals, humans, and the environment.

References Cited and Further Reading

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