11.3 Microplastics: Sources, Distribution, and Ecological Impacts

Microplastics are tiny plastic particles under 5 mm that pollute our environment. They come from various sources like industrial processes, consumer products, and transportation. These particles are everywhere, from oceans to soil to air.

The spread of microplastics in ecosystems is influenced by factors like particle size and water currents. They impact wildlife through ingestion, bioaccumulation, and toxicity. This pollution affects individual organisms and entire ecosystems, altering biodiversity and nutrient cycles.

Understanding Microplastics

Definition and classification of microplastics

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  Frontiers | Secondary Microplastics Generation in the Sea Swash Zone With Coarse Bottom ... View original

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  Microplastic and its impact on marine wildlife | OER Commons View original

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  Frontiers | Secondary Microplastics Generation in the Sea Swash Zone With Coarse Bottom ... View original

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• Microplastics consist of small plastic particles less than 5 mm in size pervasive in environment
• Size classification categorizes particles based on dimensions
  • Nanoplastics measure < 1 μm often undetectable by conventional methods
  • Microplastics range from 1 μm - 5 mm visible under microscope
• Origin classification differentiates based on production method
  • Primary microplastics manufactured intentionally at microscopic size (microbeads in cosmetics)
  • Secondary microplastics form from degradation of larger plastic items (fragments from bottles, fibers from clothing)

Sources of microplastics

• Industrial sources release particles during manufacturing and processing
  • Plastic production facilities emit pellets and powders
  • Wastewater treatment plants discharge microfibers and fragments
• Consumer products shed microplastics during use and disposal
  • Personal care items release microbeads (exfoliating scrubs, toothpaste)
  • Synthetic textiles shed fibers during washing (polyester clothing, nylon carpets)
• Agricultural practices introduce plastics to soil and water
  • Plastic mulch films degrade over time releasing fragments
  • Seed coatings break down during germination
• Transportation contributes to microplastic pollution
  • Tire wear particles accumulate on roads and wash into waterways
  • Road markings degrade and release plastic particles
• Fishing and maritime activities generate marine microplastics
  • Lost or discarded fishing gear (nets, lines) breaks down in oceans
  • Boat paint chips flake off during maintenance and use

Environmental Distribution and Impacts

Distribution in ecosystems

• Aquatic ecosystems harbor microplastics throughout water column
  • Oceans accumulate particles in surface waters, water column, and sediments
  • Freshwater systems transport microplastics through rivers and deposit in lakes
• Terrestrial ecosystems retain microplastics in soil and air
  • Soil acts as sink for particles from various sources
  • Air currents transport lightweight microplastics over long distances
• Factors affecting distribution influence particle movement
  • Particle size and density determine buoyancy and settling rates
  • Water currents and wind patterns transport particles globally
  • Precipitation and runoff wash microplastics from land to water bodies
• Accumulation hotspots concentrate microplastics in specific areas
  • Coastal areas receive input from land and sea
  • Ocean gyres trap floating particles in circular currents
  • River mouths collect microplastics from entire watersheds
  • Urban areas generate high concentrations due to human activities

Ecological impacts on biota

• Ingestion occurs when organisms mistake microplastics for food
  • Physical effects include gut blockage and false sense of fullness
• Bioaccumulation results in trophic transfer through food chains
  • Biomagnification concentrates particles in higher trophic levels
• Toxicity arises from chemical interactions with microplastics
  • Leaching of additives releases harmful compounds (plasticizers, flame retardants)
  • Sorption and transport of environmental contaminants increases exposure
• Impacts on different organisms vary based on feeding habits and habitat
  • Plankton and filter feeders ingest particles directly from water
  • Fish and marine mammals accumulate microplastics through prey consumption
  • Seabirds ingest floating particles mistaken for food
  • Soil organisms encounter microplastics in terrestrial environments
• Ecosystem-level effects alter ecological processes
  • Community structure changes due to differential impacts on species
  • Nutrient cycling disrupted by microplastic interference
  • Biodiversity potentially affected by long-term exposure and accumulation