4 major classes of pollutants and bioavailability Flashcards
what are the major classes of pollutants?
-organic pollutants
-inorganic pollutants
-organo-metallics
-nutrients
-radionuclides
what are organic pollutants?
some organic pollutants (e.g. PCBs, dioxins, DDT) are resistant to biodegradation, they are called persistent pollutants (POPs)
-polycyclic aromatic hydrocarbons (PAHs) (ex: naphthalene)
-polychlorinated biphenyls (PCBs)
-chlorinated phenols, dioxins and dibenzofurans
-pesticides (e.g. organochlorine, organophosphate)
-aromatic herbicides
what are inorganic pollutants?
-metals and metalloids (e.g. Cd, Pb, Cu, Ni, Zn, Hg, As, Se)
-nonmetallic inorganics (e.g. chlorine, ammonia)
-inorganic gases (e.g. CO2, CO, SO2)
what are organo-metallics, nutrients and radionuclides?
-organo-metallics: (e.g. methyl mercury, tributyl tin)
-nutrients: (e.g. NO3, PO4)
-radionuclides (e.g. uranium, radium)
what is bioavailability?
defined as the extent to which a contaminant in a source is free for uptake
what is the graph of bioavailability and bioaccumulation?
both biotic and abiotic factors can modify bioaccumulation/toxicity of a contaminant=”toxicity modifying factor”
-abiotic factors=nonliving (physical chemistry factors, environment like temp and weather)
what is the putative fate and behavior of a model organic lipophilic pollutant?
-volatilization: it gaseous phase
-leaching: leach into groundwater
-sequestration (complexation): nature compounds, elements combine so can no longer be taken be taken
what is the determination of lipophilicity?
a major determinant of bioavailability of non-polar organic contaminants
-more in octanol= more lipophilic, less water-soluble
what is the octanol-water partition co-efficient and octanol-air partition coefficient (index of lipophilicity)?
Kow= conc in octanol phase/conc in aqueous phase
-typically expressed as log value, range froms from -3 to +7
Koa= conc in octanol phase/ conc in atmospheric phase
-typically expressed as log value, ranges from 0.3 to 12
what is the relationship between Koa and Kow?
-more linear relationship tells us when increased Kow, there is an increase in Kos
what is the graph of lipophilicity vs water solubility?
compounds that are more lipophilic are less-water-soluble (and vice versa)
what is the relationship between lipophilicity and bioaccumulation
increased Kow=increased bioaccumulation
-threshold, accumulation starts to decrease
increased BCF, increased Kow as long as molecules are around 10-15 nm
-threshold: when too big, doesn’t matter Kow because too big to cross membrane
how does temperature toxicity?
-every species has a thermal tolerance range
-higher temp, reach effects concentration faster (same effect at lower dose)
-increased temp=increased toxicity
what physiological processes does temperature influence?
-membrane permeability (increased temp, increased permeability)
-membrane transport rate (Q10)
Q10= rate at temp. C/rate at temp. C-10
-usually enzymes increases activity when increased temp
-Q10 increases by 2-5 fold for every 10 degree differences
what are the major abiotic factors influencing bioavailability and toxicity of organic contaminants in water/soil?
-natural organic matter (NOM): come from decomposition of living beings
-dissolved and particulate organic carbon content (mg C/L or mg C/Kg)
-complexation of pollutants: influenced by lipophilicity of the organic pollutants
what is the example of graph of NOM in waters?
which one is the most toxic?
dissolved/particulate organic C variability in natural waters
-complexation will increase (therefore less toxicity)=less availably for uptake in original form
-therefore, darkest is the least toxic
what is the graph of organic C (NOM) on the bioavailability of lipophilic organic pollutants?
what are the differences in NOM variability in soil?
