by Shannon D. Phelps, M.S.
Dr. James W. Bauder, Professor
Linzy S. Browning, Research Assistant

Link to Project Photos

This page illustrates the process and results of a greenhouse phytoremediation experiment conducted at the Montana State University Plant Growth Center in Bozeman (shown left) during 2001 and 2002.

Coal bed methane (CBM) exploration and development has increased substantially over the past ten years. The Powder River Basin in Wyoming and Montana has emerged as one of the most active new locations for exploration. Today, almost 6% of the total United States production occurs in this area.

Methane extraction in the Powder River Basin co-produces an excess of saline-sodic water. This water has the potential to elevate saline-sodic conditions within the soil-water interface causing decreases in land productivity. It is hypothesized that specific species of plants can function to uptake excess salts and remediate the saline-sodic conditions associated with CBM discharge water. Halophytic species are defined as "salt tolerant accumulators." These species have the potential to accumulate high levels of sodium and other salts within their above ground tissue and, in some cases, excrete these salts onto leaf surfaces. It is also hypothesized that these halophytic species have the ability to provide substantial volumes of high quality forage. Literature suggests that some halophytic species can provide adequate crude protein and nutrients comparable to common cultivated crop and forage species.

Column experiments were conducted using maritime barley, Wytana saltbush, and Big saltbush to determine soil water response over a 32 week period with no column drainage and species' abilities to uptake and remove salt from the soil profile. Species were exposed to one of two water chemistries and one of three water table positions. Based on experimental data, selected plant species are well adapted to CBM quality water and appear to perform best within a shallow water table.

Above ground biomass was harvested a total of four times and analyzed for total biomass production, nutrient content, and salt concentrations. Preliminary results indicate that there is potential for significant biomass production and salt uptake by these species.

Objectives:

Experimental Design:

Table 1. Selected Species

Species	Common	Scientific
1	Wytana saltbush	Atriplex wytana
2	Big saltbush	Atriplex lentiformis
3	Maritime barely	Hordeum marinum

Table 2. Depth to Water Table

Position	Depth
A	45" (114 cm)
B	30" ( 76 cm)
C	15" (38 cm)

Table 3. Water Quality Treatments

Water Type	EC (mmhos/cm)	SAR	pH
Powder River water	1.9	3.5	8
CBM product water	3.5	10.5	8

72 columns were constructed of 8-inch diameter x 4 feet length PVC pipe. A monometer located on the side of each column regulated water table position by manipulating hydraulic head. Three water table positions simulated a range of conditions from dry to saturated, such as might be found in and around outflow and impound sites associated with CBM extraction.

Monometer on sides of columns.	Sampling port at 38 cm water table position.

The columns were constructed with three sampling ports at 15, 30, and 45 inches (38, 76, and 114 cm) from the base. These ports allowed three separate sampling sites and were intended to report differences in water level-root interactions for the different irrigation/impounding strategies.

Completed columns in greenhouse.	Sampling port.

Each column was planted to one of three species: 1) Maritime barley (Hordeum marinum), 2) Big saltbush (Atriplex lentiformis), or 3) Wytana Saltbush (Atriplex wytana). Each species was seeded directly into the growth medium (0.05-2.0 mm sand) and watered regularly with tap water to promote germination.

Emerging saltbush and maritime barley.

Results:

Emergence: Maritime barley-100%, Big saltbush-85%, Wytana saltbush-10%. The Wytana variety had limited success in germination and needed a second seeding to fill the columns. The other two species germinated and grew rapidly. After germintation, all species filled their columns and created a thin root network that increased with further species establishment.

Columns during 8-week establishment period.	Well established plants.

Stage III: Changes to Shallow Groundwater Chemistry During Irrigation with CBM Product Water

After an 8-week establishment period, a baseline harvest was conducted, followed by commencement of irrigation with treatment water chemistries. The two treatment water chemistries simulated common CBM chemistry in the Powder River Basin and a common Powder River chemistry.

After the first week of treatment, 100 mL water samples were taken from each of the columns at the appropriate sampling position and analyzed for electrical conductivity (salinity), SAR (sodium adsorption ration), base cations (Na⁺, Ca²⁺, and Mg²⁺), and pH. These samples were taken once per week for 20 weeks, then once every two weeks for 4 weeks, and finally once per month for the final 8 weeks of the 32 week study period. No drainage was allowed throughout the study. These data were used to determine species effectiveness at remediating effects of saline/sodic water. All water samples were analyzed by Agvise Laboratories-Northwood, ND.

Results:

Harvested biomass was dried and weighed to determine total above ground biomass, then analyzed for crude protein content and forage potential. This component of the research spanned the initial untreated baseline harvest and three continuous harvests during the imposed 32-week irrigation period, each conducted based on maturity of maritime barley. Biomass and forage potential from the baseline harvest were compared to post treatment harvest to provide a baseline scale.

Results:

Table 4. Cumulative Biomass Production

Table 5. Crude Protein Production

Stage V: Determine Selected Species' Abilities to Uptake and Remove Salt from Growth Media

All harvested above ground biomass was analyzed for salt concentrations. Na⁺, Ca²⁺, and Mg²⁺ concentrations were computed and cumulative salt uptake was calculated. Analysis was completed by Midwest Laboratories-Omaha, Nebraska.

Results:

Summary: