📚 Water & Air Pollution Overview

Brief Overview

This note covering water and air pollution was created from a 34-page PDF presentation on water and air pollution. It walks through the main drivers and indicators of pollution, from Persistent Organic Pollutants (POPs) and bioaccumulation in aquatic systems to ozone formation, acid rain chemistry, and photochemical smog.

Key Points

• Persistent Organic Pollutants (POPs) and their bioaccumulation/biomagnification pathways in fish.

• Dissolved oxygen dynamics, BOD, and turbidity effects on aquatic communities.

• Ozone chemistry, sources, and health impacts in the troposphere.

• Acid rain formation and regulatory frameworks like the Clean Water Act and Clean Air Act.

Water Pollution 🌊

Persistent Organic Pollutants (POPs)

• Do not break down – remain intact for years to decades.

• Mobile – transported by wind, water currents, and migratory birds (e.g., plastic debris).

• Fat‑soluble – dissolve in animal fat and are poorly eliminated by kidneys.

• Toxic – can mutate DNA, cause cancer, and lead to birth defects.

Bioaccumulation & Biomagnification

• Fish model (age 3 mo → 12 mo):

  • Rate of absorption =

  • Rate of excretion =

  • Net gain = → concentration rises as the fish grows.

• As small fish accumulate POPs, predators that eat many fish inherit a higher total dose, leading to unsafe levels in top‑level consumers.

Source Types of Water Pollution

Policies Protecting Water

• Clean Water Act – sets standards for pollutant discharges into U.S. waters.

• Safe Drinking Water Act – regulates contaminants in public drinking water supplies.

Dissolved Oxygen (DO) & Temperature

• High DO → High water quality; Low DO → Poor water quality.

• Inverse relationship with temperature: As water warms, gas solubility drops; colder water holds more O₂.

Thermal Pollution

• Causes:

  • Discharge of warm cooling water from power plants (e.g., nuclear).

  • Storm‑water runoff from heated urban surfaces.

  • Removal of riparian shade trees.

  • Soil erosion increasing suspended solids → turbidity → greater heat absorption.

Biological Oxygen Demand (BOD) & Oxygen Sag Curve

• Organic wastes (food, leaves, feces, etc.) enter water via sewage, agricultural runoff, food‑processing plants, etc.

• Microbial respiration reduces DO, creating an oxygen sag downstream of the discharge point.

Oxygen Sag Curve: Plots DO decline along a river segment after pollutant input; the “sag” shows the zone of low oxygen.

• Low DO shifts aquatic communities:

  • Pollution‑intolerant taxa (e.g., mayfly nymphs, caddisfly larvae) decline.

  • Pollution‑tolerant taxa (e.g., worms, fly larvae) become dominant.

Turbidity & Aquatic Community Structure

• Consequences of high turbidity:

  • Reduced light penetration → lower photosynthesis.

  • Increased heat absorption → warmer water, further lowering DO.

  • Lower biodiversity; tolerant species prevail.

Macroinvertebrate Indicators (by tolerance)

Counting these groups provides a rapid bioassessment of water quality.

Air Pollution 🌬

Primary, Secondary, & Fugitive Emissions

Major Criteria Pollutants (Clean Air Act)

Ozone

• Stratospheric ozone shields Earth from harmful UV radiation.

• Tropospheric (ground‑level) ozone is a pollutant formed by UV‑driven reactions of VOCs and .

Montreal Protocol (1987)

• Phased out chlorofluorocarbons (CFCs); substituted with HCFCs that release less chlorine.

• Result: CFC emissions cut by ~95 % since 1988; atmospheric levels projected to return to pre‑industrial values by 2049, also aiding greenhouse‑gas reduction.

Acid Rain Chemistry

• (sulfuric acid)

• (nitric acid)

These acids precipitate as rain, snow, or fog, acidifying soils and water bodies.

Photochemical Smog

Formation Reactions

3. VOCs + → peroxy radicals → regenerate → sustain ozone production

Contributing Factors

• Hot summer temperatures

• High VOC emissions (vehicles, factories)

• Urban heat islands

• Early‑morning traffic peaks

Mitigation Strategies

• Reduce vehicle miles traveled (promote public transit, carpooling).

• Shift to renewable energy sources to lower VOC and outputs.

• Implement stricter emission standards for industry and gasoline formulations.

How Toxins & Pollutants Enter an Organism’s Body

POP’s and other pollutants can enter the body of a living organism and cause disease or death

• Neurotoxin - Pollutant that causes brain related disease or death

• Carcinogen - Pollutant that causes cancer

• Teratogens - Pollutant that causes birth defects

• Endocrine Disruptors - Pollutants that interferes with hormones

Why is LD50 Important?

-Lethal Dose or Toxic Dose - Dose of a pollutant that kills 50% of the organisms in a study

• Environmental Protection Agency: Use LD50 to decide exposure limits for chemicals in consumer products, agriculture, and industry.

• Wildlife and Ecosystems: Pesticides with known LD50 leak into lakes, predictions can be made on fish and amphibian impacts

• Food Webs: When a predator consumes prey that has ingested a chemical, the predator faces higher toxic loads over time.

🧭 Overview Table for legislation

🌫 What is Smog?

Smog is a type of air pollution that reduces visibility and harms health. It is often a mixture of smoke, fog, and chemical pollutants. There are two main types:

1. Industrial smog – caused by burning coal or fossil fuels, common in the early 20th century.

2. Photochemical smog – caused by chemical reactions in sunlight, very common in modern cities (like Los Angeles).

⚗ How VOCs Contribute

1. Emission: VOCs are released into the air from cars, factories, paints, etc.

2. Reaction with NOₓ: In sunlight, VOCs react with nitrogen oxides (NOₓ) from vehicle exhaust.

3. Ozone formation: This reaction creates ground-level ozone (O₃), a main component of photochemical smog.

4. Secondary pollutants: Other chemicals, like peroxyacetyl nitrates (PANs), are also formed, which irritate eyes and lungs.

🫁 Health and Environmental Effects

• Human health: Coughing, throat irritation, asthma attacks, lung damage

• Environment: Damages crops, trees, and reduces visibility

• Climate: Some smog components can contribute to global warming

💡 Summary Diagram (Step-by-Step)

VOCs + NOₓ + Sunlight → Ground-level Ozone (O₃) → Smog

Think of it as sunlight “activating” VOCs and NOₓ to produce the visible and harmful haze in polluted cities.