Chapter 15: Soils and Pollution

Main Objectives: ► Gain a basic understanding on the issue of pollution. ► Learn terminology used in literature dealing with pollution.

Key Terms and Concepts:

Pollution (point source vs. non-point source) The principle of microbial infallibility Bioaccumulation Biomagnification Biological oxygen demand Chemical oxygen demand

1. Defining the concept of pollution A pollutant is any material that is harmful to lives and/or ecosystems once released into the environment (air, water or soil), and is the cause of pollution. (1) Human factor; (2) The "destructive" or "degrading" aspect; (3) It is an ethical definition. It is also an issue of balancing "production" with "decomposition." Important Factors: (1) Effect on humans (and other organisms) (2) "destructive" or "degrading" (3) Relevant to assumptions of value (such as staying alive) (4) negative unintended consequences, often in unintended places

1) Point source 2) Non-point source

Sources of Pollutants

- Direct - Single entry point

- Indirect - No single entry point, defused sources - Usually associated with runoff

What is nonpoint source pollution? Nonpoint source (NPS) pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water. These pollutants include:

• Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas;

• Oil, grease, and toxic chemicals from urban runoff and energy production; • Sediment from improperly managed construction sites, crop and forest lands, and

eroding streambanks; • Salt from irrigation practices and acid drainage from abandoned mines; • Bacteria and nutrients from livestock, pet wastes, and faulty septic systems;

Atmospheric deposition and hydromodification are also sources of nonpoint source pollution. In contrast, pollution from point sources comes in large amounts from a single source, such as an industrial operation or a wastewater treatment plant.

Bioaccumulation - accumulation of pollutants in an organism over its life span - can occur whenever the half-life of the pollutant is greater than the life span of the organism - seen at all levels of a food chain with continual exposure to a chemical Examples: atrazine in amphibians, most chemical exposure in humans

Biomagnification - accumulation of pesticides across trophic levels (up a food chain) - observed mostly in top predators Examples: lead in California Condors, mercury in billfish, rodent killer in coyotes and mountain lions

Biological Effects of Pollutants

Bioaccumulation of heavy metals in humans

Figure 15.11 Sources of heavy metals and their cycling in the soil–water–air–organism ecosystem. It should be noted that the content of metals in tissue generally builds up from left to right, indicating the vulnerability of humans to heavy metal toxicity.

The "fall" of the principle of microbial infallibility: Martin Alexander of Cornell University in1965, stated: “No natural organic compound is totally resistant to biodegradation provided that environmental conditions are favorable.” Self-evidenced from the fact that we do not observe any large-scale accumulations of natural organic substances, only one is fossil fuels. Why? Because: Biopolymerization was slow and gradual through evolutionary time, allowing parallel evolution of bio-decomposition. But human ingenuity outpaced microbial evolution, and the “fallibility” was proved. Because of: (1) unusual substitutions (chlorine and other halogens) (2) unusual bonds or bond sequences (in tertiary and quaternary carbon atoms) (3) highly condensed aromatic rings (4) excessive molecular size (plastics)

2. What will happen if pollutants are not degraded or mineralized to benign compounds: (1)toxic to organisms including human (2) bio-accumulation through the food-chain/webs (DDT, for example, Rachel Carson’s Silent Spring 1962) (3) deplete ozone layer (4) fill up landfills forever 3. What will happen if pollutant are degraded or mineralized: (1) intermediates may be harmful (2) some may be converted to other forms (3) every part is transformed into benign materials.

4. Issues of pollution: Let's make a list of them 4-1: Nutrient-related issues

Eutrophication--nutrients loss from soil Nitrate in ground water -- methemoglobinemia

From: US Department of Agriculture

PLATE 51 Slow-moving coastal plain stream choked with algal bloom caused by nitrogen and phosphorus from up-stream farmland.

Fish kill caused by hypoxic conditions

Biological Oxygen Demand (BOD): a measure of oxygen consumption required by the microbial oxidation of readily degradable organic substrates and ammonia in liquid wastes such as sewage. Chemical Oxygen Demand (COD): oxygen consumed by a total oxidation of the liquid waste by strong chemical oxidants. BOD < COD: since biological oxidation is often not complete, and there is production of microbial biomass, the difference is often due to the yield factor (Y). X(HCO) + X(HCO-NH2) + O2CO2 + H2O + NO3

- (chemical) X(HCO)+ X(HCO-NH2) +O2 cells + CO2+H2O+NO3

- +residues (microbial) Natural water has low O2 solubility, dissolved oxygen in natural water seldom exceeds 8 mg per liter. Because of heterotrophic microbial activities, O2 concentration in water is often lower than 8mg/L. So organic substances in sewage will often consume large amount of oxygen. Once oxygen is depleted, self-purification processes slow down drastically. Fermentation or anaerobic processes may begin to operate, which will produce fermentation products with noxious odors and colors, the system becomes anaerobic or septic.

4. Issues of pollution: Let's make a list of them 4-1: Nutrients pollution 4-2: Organic wastes (1) Waste waters and sewage sludge: Contents: organics, odor, toxic chemicals, fecal contamination, pathogens (e.g., cholera, typhoid fever) nutrients such as N, P, S, etc. It may cause the problems of eutrophication (too much nutrients, too much oxygen consumption).

From: Brady & Weil 12th edition. FIGURE 18.16 Historical and predicted trends in municipal solid-waste management in the United States. Soils play a central role in the composting and landfilling options (shown in dark green). [Data from U.S. EPA (1997)]

4. Issues of pollution: Let's make a list of them 4-2: Organic wastes (1) Waste waters and sewage sludge: (2) Animal manures: Our nation (USA) produces more than one billion Mg of solid manure annually, or 4.5 Mg per capita. "Modern" manure often contains higher salts (~10%), antibiotics, and metals. Manure has been one of the major sources of nutrient pollution for many water systems, especially near feedlots.

Agricultural and Human runoff (example of non-point source pollution) - Excessive nutrients - loss from the soil - eutrophication downstream - health hazards - nitrate in groundwater = 1000x risk of methemoglobinemia (a blood disorder)

- Toxic and chemicals - particularly heavy metals and salts

- pesticides, herbicides, etc

- pathogens (cholera, typhoid, etc)

- hormones, antibiotics “Xenobiotic” – a compound that shows up where it biologically shouldn't - human hormones in fish downstream; dioxins

4-3. Heavy metals (Hg, Pb, Cd, Cr,Ni, etc.) Sources: industrial wastes, mines, agricultural inputs (P fertilizers, sludge, etc), the use of coal and other mined materials. They can be toxic to plants and animals. Many of them bioaccumulate as they move around in ecosystems. They are very immobile in soils, therefore, difficult to remove.

Figure 15.15 The effect of pH on the adsorption of six heavy metals. The metals were adsorbed by clay-sized goethite (an iron oxide mineral) that forms coatings on many soil particles. Maintaining the soil pH near 7 (neutral) is expected to maximize the sorption and thereby minimize the solution concentration of most heavy metals, especially of copper and lead. [Modified from Basta et al. (2005)]

The article is titled: The bad earth--The most neglected threat to public health in China is toxic soil, and fixing it will be hard and costly.

Source: The webpage of The Economist

The New York Times: After ‘Cadmium Rice,’ now ‘Lead’ and ‘Arsenic Rice’ By Didi Kirsten Tatlow April 25, 2014 7:48 am

China’s Ministry of Environmental Protection said: 16% of China's Soil Is Polluted

4-4. Man-made chemicals (1) Halocarbon (CFCs): Such as: spray cans of paint, cosmetics, insecticides (DDT, 2,4 -D etc.), and freons. These things damage the ozone layer.

4-4. Man-made chemicals (1) Halocarbon (CFCs): (2) Hydrocarbons The infamous case: Oil spills of Exxon Valdez On March 24, 1989, the oil supertanker Exxon Valdez ran aground on a reef in the northern part of Prince William Sound, Alaska, discharging 260,000 barrels (11 million gallons) of crude oil that quickly covered thousands of square kilometers. The spill proved to be one of the most devastating to wildlife, especially sea otters. Killing birds, fish, shellfish, etc. Some estimation indicates that approximately three million metric tons of oil per year spills to the ocean globally.

Deepwater Horizon (BP) – Gulf of Mexico

When was the last time you heard about this on the news? (or Fukushima for that matter...)

1 million+ gallons of an untested dispersant applied near well head "Many people speculated that subsurface oil droplets were being easily biodegraded. Well, we didn’t find that. We found it was still there" - Woods Hole scientist Estimated 75% of oil left in ecosystem "The root causes are systemic and, absent significant reform in both industry practices and government policies, might well recur" White House Commission Report

4-4. Man-made chemicals (1) Halocarbon (CFCs): (2) Hydrocarbons: (3) Pesticides: By 1975, there are 1,170 pesticides in the US, 425 herbicides, 410 fungicides, and 335 insecticides. Annual production of the same year was 725 million kg. Currently there are about 600 types used in significant quantity and 1500 types for sale. The chemical structure of a particular pesticide may determine its rate and fate of degradation.

From: Tilman et al. Science 2001

EPA Pesticides use in the US (Active Ingredients)

4-5: Acid Mine Drainage

Iron Mountain Mine – near Redding, California - in operation from 1860s through 1963 - Iron, silver, gold - zinc, copper, cadmium - very high levels of FeS = Iron Sulfide - oxidation of sulfide produces acid + Iron - evaporation concentrates the acid solutes and lowers the pH)

Runoff pH = - 0.36 - most acidic water ever recorded - 10000x stronger than battery acid Flows into the Sacramento River...

Similar phenomenon could happen if some one drains a wetland with a high content of iron sulfide (FeS) in the wetland soil.

Key Terms and Concepts:

Pollution (point source vs. non-point source) The principle of microbial infallibility Bioaccumulation Biomagnification Biological oxygen demand Chemical oxygen demand

In sum, we have covered several key issues of pollution and some key terms and concepts.