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Chemical Analyses: Solids: Sodium Absorption Ratio
Plants are detrimentally affected, both physically and chemically,
by excess salts in some soils and by high levels of exchangeable
sodium in others. Soils with an accumulation of exchangeable sodium
are often characterized by poor tilth
and low permeability
making them unfavorable for plant growth. Plant growth is important
for mine reclamation for several reasons: (i) it provides an erosion
control measure for hillslope
erosion and streambank
erosion, (ii) it allows for revegetation
of reclaimed areas, and (iii) it can possibly aid in metals uptake
by phytoremediation.
Sodium adsorption ratio (SAR), along with pH, characterize salt-affected
soils. It is an easily measured property that gives information
on the comparative concentrations of Na+, Ca2+, and Mg2+ in soil
solutions. The equation used to calculate SAR is given as follows:
where [Na+], [Ca2+], and [Mg2+] are the concentrations in mmol/L
of sodium, calcium, and magnesium ions in the soil solution. Concentrations
of sodium, calcium, and magnesium are determined by first extracting
the ions from the soil into solution. The solution is then analyzed
to determine concentrations of the selected ions. Na+, Ca2+, and
Mg2+ concentrations are commonly determined using atomic absorption
spectrometry (AA). For more info on AA, click
here. The SAR of a soil extract takes into consideration that
the adverse effect of sodium is moderated by the presence of calcium
and magnesium ions. When the SAR rises above 12 to 15, serious physical
soil problems arise and plants have difficulty absorbing water (Munshower,
1994)
Chemical
Analysis | Physical
Properties |
