The salinity of motorway soils. III. Simulation of the effects of salt usage and rainfall on sodium and chloride concentrations in the soil of central reserves.
Transfer to the central reserve of salt applied to motorway carriageways and the leaching of sodium and chloride ions from the soil of the reserve are described by a mathematical model. newline˜Given daily rainfall and monthly totals of salt application and potential evaporation, the model calculates the change of sodium and chloride concentrations with time and depth in soil. Values of the transfer and leaching coefficients giving best fit to long runs of data varied from site to site, but for each coefficient extreme values were within ± 50% of the mean. Mean values of these coefficients were used in calculations and expected concentrations of sodium and chloride in soil 0-250 mm deep on 31 March at twelve sites distributed through the motorway system and over 3 years. There were significant relations between observed and calculated concentrations at these sites. Standard deviations of observed values from calculated values were about ± 250 μg g-1 for sodium ± 100 μg g-1 for chloride.