Source of Nitrate and Hydrologic Origin of an Unusual Cave Niter Dripstone; Israel

Abstract

An unusual form of niter–monomineralic potassium nitrate stalactites (up to 90 cm long) and stalagmites–was discovered in a limestone cave in the Lower Galilee, Israel. Chemical and nitrogen isotope analysis of the deposit and potential source materials, together with hydrologic evidence, suggest the following special circumstances for its formation. Very high precipitation during the winter of 1991/92 resulted in rapid transmission of rain water, with low dissolved ion concentrations, through wide fissures in the limestone; this led to the saturation of excreta‐rich cave floor sediments that are normally dry. Resulting solutions rich in potassium nitrate dripped into an underlying cave close to its large entrance, where the cave humidity is largely influenced by the humidity of the outside air. For most of the time the humidity was sufficiently low to cause evaporative oversaturation and deposition of niter from the dripping solutions. When dripping decreased, however, occasional periods of high humidity subsequently led to the progressive deliquescence and disappearance of the niter. The potential for groundwater pollution is assessed.