Distribution of Chemicals in the Environment

Distribution of Chemicals in the Environment

3.1 Introduction of Chemicals to the Environment

  • Pollution:
  • Defined as any change in the environment that produces a condition harmful to living organisms.
  • Caused by pollutants.

How Can Chemicals Be Introduced Into the Environment?

1) Agriculture Wastes

  • Fertilizers:

  • Enrich the soil to promote plant growth.

  • Typically contain nutrients such as:

    • Nitrogen (N)
    • Phosphorus (P)
    • Potassium (K)
    • Some formulations may also include sulfur (S).

  • Pesticides:

  • Used to control pests in agriculture.

    • Herbicides: Target weeds.
    • Insecticides: Target insects.
    • Fungicides: Target fungi.

2) Wastes

  • Solid Waste Management:

    • Incineration: Burning waste at high temperatures, contributing to air pollution.
    • Dump: An open hole where trash is deposited; chemicals can leach into the soil.
    • Landfill: Trash is contained to prevent environmental exposure. Liners can be used to reduce leaching.
    • Features a cross-section:
    • Garbage Layer
    • Gravel/Sand Layer
    • Leachate Collection Pipe
    • Plastic and Clay Liners

  • Wastewater:

  • Storm Sewers: Untreated water discharges directly into rivers/lakes.

  • Sewage Treatment Plants:

    • Multi-step processes to treat wastewater:
    • Physical Filtration: Screening to remove solids.
    • Biological Treatment: Introducing microbes to digest organic materials.
    • Chemical Treatment: Use of chemicals to eliminate microorganisms.

  • Released treated wastewater (effluent) may still contain some unfiltered substances.

3) Fuel Combustion

  • Combustion of fossil fuels emits CO2 and other pollutants.

3.2 Transport of Chemicals in the Environment

  • Air Transport:

  • Pollution can disperse from industrial areas to locations hundreds of kilometers away.

  • Influenced by weather patterns and wind.

  • Water Transport:

  • Water from precipitation can carry diluted toxins.

  • Liquid wastes often discharged into water bodies.

  • Soil Transport:

  • More porous soils allow flow, while less porous materials can create barriers.

3.3 Effects of Chemicals in the Environment

Acid Rain

  • Caused by industrial processes emitting gases like SO2 and NO that react with moisture.
  • Normal rain is slightly acidic (pH ≈ 5.6).
  • Acid rain has a pH < 5.6, negatively affecting water sources.
  • Acid Shock: Sudden increases of acid into water bodies, especially during spring thaw.

Eutrophication

  • Nutrients from fertilizers entering water bodies result in:
  1. Increased nutrient concentrations leading to algal blooms.
  2. Decomposition of algae by bacteria, depleting oxygen levels.
  • High concentrations of nitrogen and phosphorus cause rapid phytoplankton growth.

Global Warming and Climate Change

  • Results from increased greenhouse gases (e.g., CO2) trapping heat in the atmosphere, leading to rising global temperatures.

Bioaccumulation and Biomagnification

  • Bioaccumulation: Increased concentration of chemicals in an organism over time.

  • Biomagnification: Increased concentration of toxins as they move up the food chain.

  • Example: DDT pesticide, initially used extensively but led to severe environmental effects, including the decline of certain species due to its persistence and accumulation in the food web.

  • Real-Life Case of DDT and Ecosystem Impact:

  • Insecticide application led to loss of natural predators which caused population imbalances in pest species, resulting in broader ecological consequences.