Flashcards: Inorganic Carbon & pH
(17 cards)
What are the major sources of dissolved inorganic carbon (DIC) in aquatic systems?
Major source of carbon for photosynthesis
Buffers against pH changes
Pathway for carbon and mineral removal
Major carbon pool (greater than organic carbon in lakes)
What is the definition of a nutrient in the context of aquatic ecosystems?
A nutrient is an element that an organism must acquire to live, grow, and reproduce. It provides energy for metabolism.
What are the “Big Six” macronutrients essential for life?
Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen (O), Phosphorus (P), and Sulfur (S).
What is a biogeochemical cycle?
A biogeochemical cycle is the pathway by which a substance moves through biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) realms.
How do photosynthesis and respiration influence DIC equilibria in water?
Photosynthesis consumes CO2, lowering DIC levels.
Respiration releases CO2, increasing DIC levels.
What is the chemical equation for the dissolved inorganic carbon (DIC) pool?
ΣCO2 (DIC) = CO2 + HCO3- + CO32-
What happened during the Lake Nyos disaster in 1986?
2 million tons of CO2 were released from the lake.
Lake water level dropped by 1 meter.
A ground-hugging death cloud of CO2 spread, killing around 1,750 people.
How does carbonic acid affect pH when CO2 is dissolved in water?
When CO2 dissolves in water, it forms carbonic acid (H2CO3), which dissociates and releases hydrogen ions (H+), lowering the pH (making water more acidic).
What is the relationship between [H+] and pH?
pH = -log[H+].
A higher concentration of hydrogen ions ([H+]) results in a lower pH (more acidic).
A lower [H+] results in a higher pH (less acidic or more basic).
What are typical pH values for “undisturbed” lakes?
The pH of undisturbed lakes is generally between 6 and 8, though it can range from 2 to 12.
What factors influence the solubility of CO2 in water?
Temperature (inversely related)
Salinity (inversely related)
Pressure (directly related)
Ionic carbon complexes
What is alkalinity in the context of water chemistry?
Alkalinity refers to the amount and types of compounds in water that can raise the pH or neutralize acids, which indicates the water’s acid neutralizing capacity (ANC).
How does photosynthesis affect the DIC equilibrium in water?
Photosynthesis acts as a carbon sink, consuming CO2 and shifting the DIC equilibrium towards lower concentrations of CO2 and higher levels of bicarbonate (HCO3-).
How does respiration affect the DIC equilibrium in water?
Respiration releases CO2 into the water, acting as a source of CO2 and shifting the DIC equilibrium towards higher concentrations of CO2.
What is the buffering capacity of water?
Buffering capacity refers to the water’s ability to resist changes in pH, primarily through equilibrium reactions involving DIC (CO2, HCO3-, CO32-).
What is “lake whiting” and how is it related to DIC?
Lake whiting is the production of CaCO3 (calcium carbonate, or marl) that occurs in lakes during the summer, when increased photosynthesis and temperature lead to significant loss of CO2, shifting the DIC equilibrium.
What is the effect of weathering on inorganic carbon in water?
Weathering of rocks and soils releases minerals into the water, which can influence the concentration and types of dissolved inorganic carbon species like HCO3- and CO32-.
