Assessing Prussian yellow-assisted remediation of salt and produced water contaminated soils using native grass seed...

On-shore produced water (PW) spills can impair soil quality. To provide a practical tool for evaluating efficacy of PW-contaminated soil remediation, a seed germination test was developed. This research included three experimental phases. In the first phase, seed germination of two native grasses, Brewster sideoats grama (BSG) and Santiago silver bluestem, were investigated in 10-day tests with uncontaminated soils. Based on performance, BSG was selected for subsequent phases. In Phase 2, seed germination tests were performed on field soil spiked with dilutions of PW. A parallel sodium chloride (NaCl) solution prepared at the same chloride concentration as the PW, was tested for comparison. Soil electrical conductivity (EC) was used to characterize salt stress. Results indicated similar seed germination inhibition in PW and NaCl treatments. In Phase 3, exposure to PW and NaCl solutions spiked to field soil was repeated at lower dilutions. Soil exposures to dilutions of a 10 mM solution of a remediation agent, Prussian yellow (PY), alone and combined with PW and NaCl were also tested. In addition to soil EC, free cyanide concentrations were determined to assess potential PY photo-dissociation. Results indicated that PY alone did not inhibit seed germination. Further, addition of PY to PW or NaCl did not increase toxicity with low and variable levels of free cyanide reported in soil. These findings support PY use in soil remedial applications. Despite the wide range of potential contaminants in PW, the primary determinant of toxicity was attributed to salinity under the tested conditions. Further work is needed to assess whether native grass seed germination tests are predictive of revegetation success in the field.