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.