Describe the harmful effects of: (a) water pollution by untreated sewage and nitrogen-containing fertilisers leading to eutrophication, limited to: (i) increased availability of nitrate and other ions (ii) increased growth of producers (iii) increased decomposition after death of producers (iv) increased aerobic respiration by decomposers (v) reduction in dissolved oxygen (vi) death of organisms requiring dissolved oxygen in water (b) air pollution by greenhouse gases (carbon dioxide and methane), contributing to global warming and its likely effects (c) pollution due to insecticides and herbicides (d) non-biodegradable plastics in the environment, in both aquatic and terrestrial ecosystems

The harmful effects of various types of pollution are significant and multifaceted, impacting ecosystems, human health, and the environment. Below is a detailed description of the impacts of water pollution from untreated sewage and nitrogen-containing fertilizers, air pollution from greenhouse gases, pollution from insecticides and herbicides, and the effects of non-biodegradable plastics in both aquatic and terrestrial ecosystems.

(a) Water Pollution by Untreated Sewage and Nitrogen-Containing Fertilizers Leading to Eutrophication

(i) Increased Availability of Nitrate and Other Ions

The discharge of untreated sewage and agricultural runoff containing nitrogen-based fertilizers significantly increases the concentration of nitrates and other ions in water bodies. This nutrient enrichment can lead to eutrophication, where excessive nutrients stimulate algal blooms, altering the natural balance of aquatic ecosystems.

(ii) Increased Growth of Producers

The availability of nitrates promotes the rapid growth of phytoplankton and other aquatic plants. This phenomenon results in dense algal blooms that can cover water surfaces, blocking sunlight from reaching submerged plants and disrupting photosynthesis.

(iii) Increased Decomposition After Death of Producers

When these algal blooms die off, they sink to the bottom where they are decomposed by bacteria. This process significantly increases organic matter in the water, leading to heightened decomposition rates.

(iv) Increased Aerobic Respiration by Decomposers

The decomposition process requires oxygen, leading to increased aerobic respiration by decomposers. As bacteria break down the organic material, they consume large amounts of dissolved oxygen in the water.

(v) Reduction in Dissolved Oxygen

As a result of increased decomposition, the levels of dissolved oxygen in the water drop dramatically. This condition can create hypoxic or anoxic zones where oxygen levels are insufficient to support most aquatic life.

(vi) Death of Organisms Requiring Dissolved Oxygen

The reduction in dissolved oxygen leads to the death of fish and other organisms that depend on it for survival. This can result in significant declines in fish populations and overall biodiversity within affected ecosystems.

(b) Air Pollution by Greenhouse Gases (Carbon Dioxide and Methane)

Air pollution from greenhouse gases such as carbon dioxide (CO2) and methane (CH4) contributes significantly to global warming. These gases trap heat in the atmosphere, leading to an increase in global temperatures.

Likely Effects:

1. Climate Change: Rising temperatures disrupt weather patterns, leading to more frequent and severe weather events such as hurricanes, droughts, and floods.
2. Melting Ice Caps: Increased temperatures cause polar ice caps and glaciers to melt, contributing to rising sea levels that threaten coastal communities.
3. Impact on Ecosystems: Changes in temperature and precipitation patterns affect habitats, leading to shifts in species distributions and increased extinction rates for vulnerable species.
4. Ocean Acidification: Increased CO2 levels lead to higher concentrations of carbonic acid in oceans, affecting marine life such as coral reefs which are sensitive to pH changes.

(c) Pollution Due to Insecticides and Herbicides

The use of insecticides and herbicides in agriculture leads to significant environmental pollution.

Impacts:

1. Toxicity to Non-Target Species: These chemicals can harm beneficial insects like pollinators as well as aquatic organisms when they run off into waterways.
2. Bioaccumulation: Persistent chemicals accumulate in the food chain, affecting predators at higher trophic levels including birds and mammals.
3. Soil Health Degradation: Continuous use can degrade soil health by killing beneficial microorganisms essential for nutrient cycling.
4. Resistance Development: Over time, pests may develop resistance to these chemicals, leading to increased application rates or more toxic alternatives being used.

(d) Non-Biodegradable Plastics in the Environment

Non-biodegradable plastics pose severe threats to both aquatic and terrestrial ecosystems.

Impacts:

1. Ingestion by Wildlife: Animals often mistake plastic debris for food, leading to ingestion that can cause internal injuries or death.
2. Microplastics Formation: Larger plastic items break down into microplastics that contaminate soil and water systems, entering food chains with unknown long-term effects on health.
3. Habitat Disruption: Plastics can alter habitats; for instance, plastic waste can smother coral reefs or disrupt soil structure in terrestrial environments.
4. Chemical Leaching: Plastics may leach harmful chemicals into soils or waterways, posing risks to wildlife and human health through contaminated food sources.