EPA Grant Number: R83-0633-010
Title: Continuation of Remediation of Brine Spills with Hay
Investigators: Laura P. Ford and Kerry L. Sublette
Institution: University of Tulsa
EPA Project Officer: Bala Krishnan
Project Period: To be announced
Project Amount: $35,314
Research Category: Soil Remediation
This project is a continuation of the IPEC project Remediation of Brine Spills with Hay. In the first year of this project, we set up a field demonstration to treat two produced fluids spill sites and a control site with four different soil amendments to determine the effectiveness of hay as a soil amendment for brine spills. Our four soil treatments are tilling, tilling with hay, tilling with fertilizer, and tilling with hay and fertilizer. Eight microcosms were built to treat contaminated soil with the same soil amendments and provide controlled watering and aeration. The field sites and microcosms have been sampled regularly to track changes in concentrations of brine components, soil properties, and microbial populations to determine the mechanism(s) by which remediation occurs.
We have proposed three mechanisms by which organic matter (hay) may aid the removal of salt. (1) The hay may provide pores for water to enter the soil and leach salt components away. (2) Compounds formed during the decay of the hay can exchange cations with the clay, releasing sodium from the clay. (3) Products formed during the decay of hay can bind the clay particles into water-stable aggregates. All mechanisms improve the permeability of the soil, allowing water to flush salt from the soil. The first mechanism should dominate early in a remediation project. The second and third mechanisms should become more important as the hay decays. Microbial action is important to all three mechanisms: biodegradation of the hay will decrease the rate of the first and increase the rates of the other two proposed mechanisms.
First year results indicate that the first mechanism is probably active: permeability appeared to increase in the sites and microcosms with hay. The second and third mechanisms did not appear to be active. Microorganisms in sites and microcosms with hay were different from those without hay. Salt components decreased more in microcosms with hay than those without. Over the first year, salt components decreased most in the sites with tilling and fertilizer, interestingly.
This project continues the field demonstration component of the first year, since the sites received little rain to wash the salt away in the first year. We will sample the field sites monthly during wet, warm months and quarterly otherwise. We will continue to analyze the samples for cation and anion concentrations, nutrient concentrations, cation exchange capacity, hydraulic conductivity, wet aggregate stability, and microbial population and diversity. A dual ring infiltrometer will be used to measure hydraulic conductivity/permeability in situ instead of the unreliable, ex situ technique used in the first year. We will also perform denaturing gradient gel electrophoresis at the end of the second year to identify important species in the field sites, for comparison with results from the microcosms. To better see where the microorganisims are (soil versus hay), we will do plate counting of microorganisms cultured from the soil and from the hay. If rainfall is low in the hot summer months, we will water the sites to ensure that changes are seen over the second year of the project.