Heavy Metals Flashcards
What are the primary sources of Pb?
- Historically: pipes, paints, and gasoline
- Today: batteries and traces in coal combustion
- batteries, pigments, ammunition
*can substitute Ca2+
What is a Class A metal?
- Affinity to bond w O
- Mainly alkali and alkaline earth metals
EX: Al, Mg, Ti
What is a Class B metal?
- Affinity to bond w S or N
EX: Cu, Hg, Ag, Pb - Highest toxicity
- Bond w organic molecules (organometallic)
- Implications for impairing metabolic roles and diffusion across membranes
What are the primary sources of Cu?
- Biocides (antifouling paint)
- electrical equipment
- pesticides
What are the primary sources of Zn?
- used in marine sacrificial anodes
- biocide (antifouling paint)
- galvanizing
What are the primary sources of Cd?
- Used in anticorrosive coatings and rechargeable batteries (Ni-Cd)
- Pigments and stabilizers for plastics
- Zn mining byproduct
- galvanizing
- more toxic to inverts w parts that include Ca
What are the primary sources of Hg?
- Historically: amalgam (dissolves other metals), pesticide, and antiseptic
- Chlor-Alkali production
- Methylmercury
- lights
- batteries
- electrolysis
- accumulates in larger bodied organisms
What is the common ion effect?
refers to the decrease in solubility of an ionic precipitate by the addition to the solution of a soluble compound with an ion in common with the precipitate
What is adsorption?
a process where molecules, ions, or atoms stick to the surface of a solid or liquid
What is desorption?
the process where adsorbed atoms or molecules are released from a surface into the surrounding vacuum or fluid
What is flocculation?
a process where small particles in a liquid aggregate or clump together to form larger, visible clusters called flocs, which can then be more easily separated from the liquid through sedimentation or filtration
What are some essential metals?
Cu, Fe, and Zn
How are heavy metals bioregulated?
- dissolved metals are commonly taken up through the gills
- filter feeders usually have the highest concentrations
- free ions cannot diffuse across membranes
- can pass through ion channels
- ions of similar charge and size can be substituted or taken by the same gateways
What is a heavy metal?
- density of >5 g/cm^3 (Al is an exception)
Ex: Al, Mg, Ti
What is a trace metal?
- naturally abundant
- <1000 ppm (Ex: Cr, V, Ni, Cu, Co, Pb, Sn)
- <1 ppm (Ex: Cd, Hg)
What are some trace metal sources?
Rivers - adsorbed to clay minerals, desorption at seawater salinities
Atmospheric input - important source of Pb to open ocean
Sediment remobilization
Hydrothermal vents - hot solution leaches metals from basalt, most metals are precipitated as sulfides immediately
Anthropogenic inputs - sewage, antifouling paint, oil, pesticides, gas
What are some trace metal sinks?
adsorption and incorporation into biogenic material
What are some examples of heavy metals being used as tracers?
Pb: tracer of pollution, it used to be in gasoline, decreases with time at the surface, can also be used in looking at corals, they sometimes mistake PbCO3 as CaCO3
Mg: use it in corals to indicate temperature, Mg/Ca is a good indicator of temp with forams
Cd: use CdPO4 correlation as a tool to determine paleo PO4 concentrations
Mn: trace HVT fluids, used in redox chemistry to understand suboxic zones; in suboxic conditions particulate forms (MnO2 or some form of Fe and O)
What is a ppm?
1 mg/L
10^-6 mol/L
Ex: Nutrients
What is a ppb?
1 microgram/L
10^-9 mol/L
Trace metals (can be as low as 10^-12 mol/L)
What does a conservative or accumulated profile look like? Concentration? Controls? Examples?
- straight line
- depth distributions are linearly related to salinity
- Controlled by physical processes (advection, turbulent mixing)
- Biounlimited
- Normalized to salinity
- Long residence time (10^6 yrs)
- Concentration = 10^-1 to 10^-8
Ex: Rb, Cs, Mo, U
What does a recycled or nutrient-type profile look like? Concentration? Controls? Examples?
- log curve starting with a log concentration and ending with a higher concentration
- biological control
- surface depletion and deep enrichment
- mid depth maximum (recycled soft parts)
- correlated with nutrients
- short residence time (10^3 - 10^5 yrs)
- higher Pacific concentrations (thermohaline circulation, accumulation)
- good way to look at nutrient concentrations (Zn trying to replace Si)
Ex: Cd, Zn, Cu, Ni, Cr
What does a reactive or scavenged profile look like? Concentration? Controls? Examples?
- peak in the shallow waters (river inputs!!!)
- large metal supplies to the mixed layer
- high crustal abundance (rivers, aeolian dust)
- short residence times (50-100 yrs)
- Rapidly precipitated and/or adsorbed
- Higher concentration in the ATL
- Sediment remobilization
Ex: Al, Pb, Mn
