Aquifers brimming with poison
israel may soon become a place where there is not a drop of freshwater to drink. It is well established that seawater seeps into coastal aquifers and contaminates them with salts. Now Brian Berkowitz and his colleagues from Israel-based Weizmann Institute of Science claim that their country's aquifers are even polluted by toxic organic pollutants that are often found in seawater. To date, it was thought that the toxic compounds are not very soluble. But Berkowitz's team shows that the salinity difference between the waters of the sea and the aquifer creates a force that dissolves the pollutants.
The researchers mimicked the interface of an aquifer and seawater by using two vessels -- one filled with salty water and the other with freshwater. A layer of porous sand connected the vessels. Two toxic solvents -- benzene and trichloroethylene -- were added to the salty water. To their utter horror, the researchers saw that dissolved salt made these compounds soluble. According to the researchers, waves, tides and other stirring processes can enhance the adverse phenomenon, which also plagues other parts of the world. Unlike the salts, separating the toxicants from water involves an expensive task.
The phenomenon may be a reason why there is an acute shortage of water in the region -- a major cause of Arab-Israeli tension. Israel's scant water resources are in a parlous state. It has only two small main aquifers, from which water is being drawn faster than it can be renewed because of irrigation, non-indigenous crops and the country's burgeoning number of swimming pools, gardens and golf courses. Moreover, effluents and other deleterious substances are frequently dumped in the waterbodies of the country, thanks to lax pollution regulations. The extensive contamination is responsible for high incidences of dysentery and kidney diseases.
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