Lecture 19 NR

Overview of Water Quality Lectures

  • The lecture is divided into two parts:

    • General water quality.

    • Focused discussion on dissolved oxygen.

Types of Stressors on Water Quality

  • Physical Stressors:

    • Examples include sediment.

    • Sediment plays a crucial role in stream restoration initiatives, addressing sedimentation rather than directly focusing on nutrients, algae, pathogens, or heavy metals.

  • Biogeochemical Stressors:

    • Discussion on nutrients, particularly nitrogen and phosphorus, which contribute to algal blooms.

    • Nutrient levels are significant in determining water quality and ecological health.

  • Biological Stressors:

    • Focuses on pathogens, heavy metals, and emerging contaminants.

Pathogens in Water

  • Definition of Pathogens:

    • Any organism that produces a disease.

    • Includes various types of organisms like viruses, bacteria, fungi, and protozoa.

  • Examples of Pathogens:

    • E. Coli:

    • Commonly associated with unsanitary conditions and consumption of undercooked food.

    • Can thrive in water sources, making consumption unsafe.

    • Cholera:

    • A waterborne disease that can lead to severe illness.

    • Giardia:

    • A protozoan parasite found in natural water bodies that requires filtration or treatment before consumption.

  • Health Implications:

    • Pathogens can cause significant health issues in humans; animals may have more resistant digestive systems.

    • Sewage contamination typically indicates the presence of pathogens (detectable by odor).

Heavy Metals

  • Definition:

    • Toxic elements that pose health risks when found at high levels in water.

  • Prominent Heavy Metals:

    • Lead:

    • Entrapment from old piping, urban runoff, and historical contamination.

    • Particularly harmful to children, causing developmental issues.

    • Mercury:

    • Ubiquitous in the environment due to industrial emissions.

    • Bioaccumulates in the food chain, especially in fish, leading to higher concentrations in larger fish such as tuna.

  • Health Risks:

    • Mercury exposure can result in neurological impairments and is especially dangerous for pregnant women.

    • Guidelines suggest limiting tuna consumption to reduce exposure risk.

Emerging Contaminants

  • Definition:

    • Potentially harmful pollutants not historically recognized but now identified as environmental concerns.

    • Characterized as unregulated pollutants with uncertain chronic effects.

  • Examples Include:

    • Microplastics:

    • Small plastic particles that can enter water systems and ecosystems.

    • Pharmaceuticals:

    • Medications flushed into the wastewater system, often not adequately filtered out during treatment.

    • PFAS (Per- and Polyfluoroalkyl Substances):

    • Commonly referred to as “forever chemicals” due to their persistence in the environment.

    • Found in various products and detected in water supplies.

    • Associated chronic health impacts are still being investigated.

Pollution Sources in Water Bodies

  • Point Sources of Pollution:

    • Defined as specific, identifiable sources of pollution, such as discharge pipes from factories or sewage treatment plants.

    • Regulated through the National Pollutant Discharge Elimination System (NPDES), enabling direct measurement of impacts.

  • Nonpoint Sources of Pollution:

    • Diffuse sources that cannot be pinpointed to a single location, including agricultural runoff, urban development, roads, and cities.

    • Regulated through the Total Maximum Daily Load (TMDL) program, which establishes pollution limits based on watershed health rather than the individual source.

  • Management Practices:

    • TMDL establishes pollution limits for streams based on their overall condition, rather than targeting specific offenders.

    • Impaired water bodies are listed under section 303(d) of the Clean Water Act and require development of watershed management plans.

Observations on Water Quality Scenarios

  • Scenario A:

    • After heavy rain, the stream turns brown, indicating sediment runoff.

    • Fish experience stress but do not die, and the water clears up within a week.

  • Scenario B:

    • A stream downstream from agricultural sources begins clear but develops an algal bloom over weeks, resulting in fish kills.

  • Discussion Points:

    • Identify harmful pollutants and their impacts on ecosystems for both scenarios.

    • Determine effective management strategies for mitigating the described pollution effects.

Summary of Key Themes

  • Water quality issues are multifaceted, often arising from a combination of physical, biogeochemical, and biological stressors.

  • The relationship between pollutants and ecological conditions is crucial; understanding how pollutants interact with ecosystems is essential for effective management and remediation strategies.

  • Continuous monitoring and regulation changes are necessary to adapt to new understanding and emerging contaminants impacting water quality.