CONCLUSIONS
Evaporation modelling of saline feedwater sources showed that
evaporation using the PHRQPITZ model started to precipitate minerals
earlier than the widely used B-dot activity coefficient model. In
addition, the higher salinity of feedwater, e.g., coastal shallow
groundwater, contributed to rapid precipitation of larger amounts and
variety of mineral mass. Furthermore, for seawater, the difference in
total mineral precipitation prediction was minimal between the two
activity coefficient models.
A 1-D continuous-flow simulation was performed under surficial
evaporation conditions in the different coastal soils of Abu Dhabi. The
results demonstrated the following: (1) An inverse correlation between
seawater loading and agricultural return water salinity; (2) soil type
did not have a significant influence on the salinity of agricultural
return water, except for strongly gypsic soils for which the B-dot model
predicted a 5-6% higher salinity than PHRQPITZ; (3) mineral
precipitation modelled under seawater application was highly influenced
by the original coastal soil type and the solid phase mineral content in
its different layers - for calcite-rich soils, the influence of shallow
water evaporation proved to be a strong catalyst for deposition, while
gypsum-rich soils showed a dissolution-reprecipitation phenomena; and,
(4) porosity loss occurred in all cells, with mineral deposition zones
generally correlating with zones of maximum porosity loss. The study
demonstrated geochemical modelling to be a vital tool for testing saline
water irrigation scenarios in support of sustainable halophyte farming
thereby preventing potential future land degradation.