Environmental Data Analysis EESC
BC 3017
Major anions in precipitation, surface waters, and the ocean
- water is constantly being recycled in the hydrologic cycle (Fig)
- it is an excellent solvent
- it is vital in Earth's geochemical cycles
- water contains dissolved gases, ions, inorganic and organic
molecules, organisms,....
- Ion: an atom or a group of atoms that has either an excess or a
deficiency of electrons
- major ions in water, positive charge (cations), negative charge
(anions)
- H+, Na+, K+, Ca2+,
Mg2+, NH4+,
F-, Cl-, SO42-, NO3-,
HCO3-, CO32-, PO43-
- we will focus here on F-, Cl-, NO3-,
and
SO42-
- we typically express concentrations in mmol/L or mg/L
- Mole: unit of amount
of
substance.
- By definition, the mole is the amount of substance of a
system
that
contains as many elementary entities as there are atoms in 0.012
kilogram (12g) of carbon-12. The elementary entities, which must
be specified, may be atoms, molecules, ions, electrons, other
particles, or even specified groups of such particles.
- 1 mole = 6.022*1023 molecules or atoms (or other
units)
- conversion from mg/L to mmol/L
- On-line periodic table
- Equivalent: another
unit of amount of
substance. An equivalent or Eq is the number of moles divided by the
number of electrons lost or gained by each molecule in a reaction
Rainwater chemistry
- atmospheric moisture makes it into the atmosphere by evaporation
and transpiration, shouldn't it be distilled water?
- there is lot's of stuff in the atmosphere (gases, particles) that
dissolve in cloud droplets and increase the anion concentrations
- these substances are eventually removed from the atmosphere by
wet and dry deposition
Particles in atmosphere
- sea salts from the ocean surface (35%)
- soil and mineral dust from the continents (27%)
- forest fires (6%)
- volcanic ash (3%)
- particles from direct anthropogenic emissions (3%)
- particles from gaseous emissions
- sulfate from H2S
- sulfate from SO2
- nitrate from NOx
- hydrocarbons, biogenic
- hydrocarbons, fossil fuel
Sources of major anions in precipitation (marine; terrestrial; pollution)
- Cl-: sea salt; industrial HCl, roadsalt
- SO42-:
sea salt, marine gases (DMS,
Dimethylsulfide); H2S from biological decay, volcanoes,
soil dust; burning of
fossil fuels to SO2, forest burning
- NO3-:
N2 plus lightning; NO2 from biological decay and N2 from lightning; combustion of fossil fuels, forest
burning, nitrogen fertilizers
- PO43-:
soil dust, biogenic aerosols
absobed on sea salt; burning
vegetation,
fertilizer
- HCO3-:
CO2 in air; CO2 in air, soil dust
- (NH4+
(cation!):: biological
activity, bacterial decay, fertilizers,
human, annimal waste decomposition)
rainwater can be considered as being dilute, total dissolved salt (TDS)
content equals a few mg/L
interactions between rainwater and plants can already change the
dissolved ion concentratyions significantly (Fig)
- dry deposition
- evaporation
Rivers
- precipitation will eventually hit the surface and may take up
substances that have deposited by dry deposition on surfaces, such as
leaves
- rainwater interacts with soils & rocks => weathering; e.g.
- H2CO3 + CaCO3 => Ca2++2HCO3-
- Mg2SiO4 + 4H2CO3
=> 2Mg2++ 4HCO3-+H4SiO4
- weathering releases other compounds (e.g. Cl-, SO42-)
- concentrations of most anions higher than in precip due to
dissolution of dry deposition particles and weathering, some are
lower (e.g. nutrients, which may be taken up by plants)
- anion concentrations may increase due to
- leakage from sewers and septic systems (NO3-,
NH4+, PO43-)
- roadsalt use in the winter time (Cl-)
- Anions in average US
river,
mmol/L
Groundwater
- groundwater anion concentrations increase further due to
additional weathering
Sea water
- rivers eventually flow into the ocean
- oceanwater is fairly concentrated solution, affected by tectonic
and biological activity
- Anions in oceans, mmol/L
Drinking water
- drinking water in the NYC area comes from
- reservoirs north of the city (mostly Croton, Delaware, and
Catskill systems)
- groundwater (northern NJ, Long Island, parts of Queens,
Rockland Country)
- the NYC drinking water is currently unfiltered surface water,
chlorine and fluoride and a few other substances are being added
Our samples
- inductive method
- the samples we have measured in the past are from
- we measured measure major anion concentrations of these samples
and
will try to interpret the results;
- what would you expect to
see
in terms concentrations in a relative sense?
Resources
- Berner, E.K., and Berner, R.A. (1987) The global water cycle.
Prentice-Hall, Englewood, NJ, 397pp.
- Berner, E.K., and Berner, R.A. (1996) Global Environment.
Prentice-Hall, Englewood, NJ, 376pp.
- Drever, J.I. (1988) The geochemistry of natural waters.
Prentice-Hall, Englewood Cliffs, NJ, 437pp.
- National Atmospheric
deposition program
- NYC
Drinking Water Supply and Quality Report