DOI: http://dx.doi.org/10.1065/lca2002.06.084
--- Salinity is an increasing environmental problem in agricultural
ecosystems and is not adequately represented in conventional
life cycle assessment (LCA) impact categories. It is
often not the total quantity of salts emitted or the proportion of
salt accumulated in the soil profile that is the primary mechanism
for deteriorating soil conditions for irrigated salinity, rather
the ratio of major cations in the soil matrix and the potential
for colloid dispersion and reduced permeability. A soil salinisation
potential (SP) is proposed as an indicator for irrigated
salinity and potential soil degradation from poor irrigation practices.
The indicator uses the threshold electrolyte concentration
concept that predicts the adjusted sodium adsorption ratio (SAR)/
Electrical conductivity (EC) ratio that soil will no longer
flocculate, but potentially disperse. The SAR is converted to a
threshold EC and compared to the measured EC in order to
develop a site-specific irrigation equivalence factor (EF). This
site/region/process specific EF is then used to weight the sodium
load to soil and repeated for each stage throughout the entire
life cycle to determine the overall Salinisation Potential (SP).
The data required for calculating the SP is generally readily available
either on site or from the water chemistry of the local watercourses.
Preliminary calculations simply require the volume,
pH, electrical conductivity (EC), alkalinity and the concentrations
of Na, Ca, and Mg of the irrigation water. The site/process/
region specific nature of the indicator ensures a quantitative
measure to enable comparisons between different systems and
is useful for identifying stages in the life cycle of a product (particularly
food products), where the potential for soil salinisation
and soil degradation is most severe. |
