THE POTENTIAL FOR BORON PHYTOTOXICITY IN PRODUCED WATER CONTAMINATED TALLGRASS PRAIRIE SOILS

The primary objectives of current brine remediation techniques focus on the removal of salt. However, residual disturbance to the vegetation is a common characteristic of remediated sites. The purpose of this research is to identify potential brine-induced, elemental phytotoxins that could persist in the soil after a successful removal of the sodium chloride salt. Awareness of these phytotoxins could lead to more thorough remediation techniques capable of restoring an impacted area to a state closer to pristine.

The 24 samples analyzed consisted of 21 soil samples and 3 liquid brine samples all gathered at the Tallgrass Prairie Preserve in Osage Co., OK during July 2005 and June 2006. The soil samples were obtained through five-fold random sampling to a depth of 15 cm and represent a spectrum of brine contamination. The liquid brine samples were obtained from operating pump jacks at the preserve. Of the elements identified in brine-impacted soils using inductively-coupled plasma mass spectrometry, most appeared to follow the trend of the salt component of brine, i.e. higher concentrations were found in non-remediated sites relative to remediated sites. Historic brine scars typically contained the highest levels of both salt and identified elements, while pristine prairie soils had the lowest. One identified element, however, did not follow this trend. Boron levels remained elevated in all soils, with the exception of those derived from unimpacted prairie. For non-remediated sites, both historic and recent, B levels ranged from 0.3-6.3 ppm, for remediated sites, 0.2-2 ppm, and for unimpacted sites 0.3-0.8 ppm. Boron, then, does not respond to the remediation techniques employed and thereby persists in the soil after the removal of salt. This is significant because boron is a known phytotoxin. These numbers were derived from a preliminary procedure and are subject to change as results are acquired from boron-specific procedures currently in progress.