Ryegrass enhancement of biodegradation in diesel-contaminated soil

Kaimi, Etsuko; Mukaidani, Tsukasa; Miyoshi, Shyoji; Tamaki, Masahiko

doi:10.1016/j.envexpbot.2004.10.005

Cited by 137 publications

(76 citation statements)

References 31 publications

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“…Thus planted mesocosms had an initially slower but more complete biodegradation of the petroleum compounds. These results are similar to the results reported in the literature by Kaimi et al (2006) andChanieau (2000). Also, similar results were observed in earlier laboratory studies with GRP diluent (Hoffman, 2003;Martin, 2003).…”

Section: Chapter 5 Discussionsupporting

confidence: 93%

“…A positive correlation between increased microbial activity and petroleum hydrocarbon remediation was found in a study by Kaimi et al (2006) with a time-course experiment with ryegrass grown on soil experimentally contaminated with diesel oil. The rhizosphere and rootfree soil degradation rates were nearly the same until the 90-day sampling, then from the 90-day sampling to the 152-day sampling the rhizosphere soil showed a statistically significant decrease in TPH.…”

Section: Root Exudatesmentioning

confidence: 78%

“…In the TRF results for Run 5 of the Day 57 sampling, the TRF patterns showed similarity between the two groups of mesocosms. In a different study of microbial communities in a phytoremediation experiment with planted versus soil-only microcosms, the microbial populations were the most similar at 90 days (Kaimi et al,., 2006). The differences between the microbial communities increased from then until the end of the study, with the planted microcosms having a larger and more active community (Kaimi et al, 2006).…”

Section: Chapter 5 Discussionmentioning

confidence: 99%

“…The biodegradation rate of diesel oil showed a correlation with soil dehydrogenase activity in both the rhizosphere and the root-free soil. Thus, results from Kaimi et al (2006) indicate that the growth of roots enhanced the microbial activity which in turn appeared to contribute to the biodegradation of diesel oil. This is the same biodegradation behavior observed in earlier EBI studies by Hoffman (2003) and Martin (2003) described below in Section 2.5.2.…”

Section: Root Exudatesmentioning

confidence: 97%

“…The mesocosms allowed for control of experimental parameters under conditions closely matched to field conditions. However, the willow trees during the earlier study were not healthy, which may have caused a lack of root growth which has been strongly correlated with phytoremediation (Huang et al, 2005;Kaimi et al, 2006;Kechavarzi et al, 2006). In the current study fertilizer was added to all the mesocosms, which greatly improved the health of the willow trees, resulting in robust growth.…”

Section: Acknowledgementsmentioning

confidence: 98%

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Phytoremediation of Weathered Petroleum in Groundwater by Arroyo Willows in Nutrient Amended On-Site Mesocosms

Bragg-Flavan¹

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A large-scale mesocosm study was conducted to determine if vegetation with willow trees enhances biodegradation and to evaluate the mechanisms of natural biodegradation of weathered petroleum compounds under field conditions. The mesocosms were designed to model conditions at a former oil field where mid-range petroleum distillates were used as a diluent for pumping crude oil contaminated the soil and groundwater at the site with petroleum compounds. Ten mesocosms were constructed at the field site using un-impacted soil and diluent-impacted groundwater from the site. Five of the mesocosms were planted with Arroyo Willow trees native to the field site and the other five served as controls without trees. Since these willow trees are phreatophytes, their roots are capable of consuming water from the water table. A previous study was conducted using these mesocosms, however the willow trees then were in poor condition.In this study, fertilizer was added to the mesocosms to promote healthy growth of the willows. Fertilizer was added equally to mesocosms with and without willow trees to avoid introducing bias. Groundwater was circulated through the mesocosms for two 109 to 126 days runs, while the total petroleum hydrocarbon (TPH) concentrations of the groundwater were measured periodically. Dissolved oxygen concentrations were also monitored in each of the mesocosms to determine if the willow trees had any impact on oxygen transfer to the subsurface.In the first run without nutrient amendments the trees did not enhance biodegradation.All the mesocosms started with an average TPH concentration of 6.3 mg/L and ended vi with a concentration of 1.0 mg/L. After this first run, nutrient amendments were added to all the mesocosms, resulting in healthy trees with robust growth. With healthy willow trees, the planted mesocosms resulted in a statistically significant increase in long-term biodegradation of dissolved-phase petroleum compounds. The planted mesocosms resulted in 29 percent more degradation. These results agree with prior lab studies using bench-scale microcosms with media from the former oil field which indicated that TPH concentrations after 100 days were lower in containers with willows or lupines compared to controls without plants. Microtox ® toxicity decreased for both planted and control mesocosms, showing no toxic root exudates or by-products.There are several potential mechanisms of the observed phytoremediation. Terminal restriction fragment analyses showed that the planted mesocosms had different microbial communities than the unplanted mesocosms. Thus, a possible mechanism of the phytoremediation is stimulation of a rhizobial microbial community that biodegrades petroleum compounds. The dissolved oxygen (DO) concentrations were actually lower in the planted mesocosms, possibly due to consumption of oxygen during biodegradation of root exudates. The reduced DO concentrations in the planted mesocosm discounts the possibility that the plants stimulated biodegradation by increasing oxygen transfer to the ...

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Section: Chapter 5 Discussionsupporting

confidence: 93%

Section: Root Exudatesmentioning

confidence: 78%