Microbial Degradation of Gasoline in Soil: Effect of Season of Sampling

In cases where fire debris contains soil, microorganisms can rapidly and irreversibly alter the chemical composition of any ignitable liquid residue that may be present. In this study, differences in microbial degradation due to the season in which the sample is collected was examined. Soil samples were collected from the same site during Fall, Winter, Spring and Summer and the degradation of gasoline was monitored over 30 days. Predominant viable bacterial populations enumerated using real-time PCR and reverse transcriptase polymerase chain reaction (RT-PCR) enumeration revealed the predominant viable bacterial genera to be Alcaligenes, Bacillus, and Flavobacterium. Overall, the compounds most vulnerable to microbial degradation are the n-alkanes, followed by the mono-substituted alkylbenzenes (e.g., toluene, ethylbenzene, propylbenzene and isopropylbenzene). Benzaldehyde (a degradation product of toluene) was also identified as a marker for the extent of biodegradation. Ultimately, it was determined that soil collected during an unusually hot and dry summer exhibited the least degradation with little to no change in gasoline for up to 4 days, readily detectable n-alkanes for up to 7 days and relatively high levels of resilient compounds such as o-xylene, p-xylene and 1,3,5-trimethylbenzene. These results demonstrate, however, that prompt preservation and/or analysis of soil evidence is required in order to properly classify an ignitable liquid residue

RRx-001, A novel dinitroazetidine radiosensitizer

The ‘holy grail’ in radiation oncology is to improve the outcome of radiation therapy (RT) with a radiosensitizer—a systemic chemical/biochemical agent that additively or synergistically sensitizes tumor cells to radiation in the absence of significant toxicity. Similar to the oxygen effect, in which DNA bases modified by reactive oxygen species prevent repair of the cellular radiation damage, these compounds in general magnify free radical formation, leading to the permanent “fixation” of the resultant chemical change in the DNA structure. The purpose of this review is to present the origin story of the radiosensitizer, RRx-001, which emerged from the aerospace industry. The activity of RRx-001 as a chemosensitizer in multiple tumor types and disease states including malaria, hemorrhagic shock and sickle cell anemia, are the subject of future reviews

Phytoremediation of nitroglycerin in smokeless powders

The reported study evaluated the feasibility of rhizosphereenhanced phytoremediation in the removal of nitroglycerin (NG), as applied in commercial smokeless powder (SP), from soil. Double base smokeless powder was applied to soil mesocosms at rates of 0, 1, 5 and 10% (w/w). The mesocosms were seeded with oats (Avena sativa) or planted with live sedge plants (Carex vulpinoidea). Composted biosolids (20% w/w) were used as a soil treatment. Mesocosms were sampled at 7, 14, 30, and 60 days after initial planting. Determination of residual soil NG was performed using gas chromatography with an electron capture detector. Both plant species were capable of modest NG uptake (146.0 and 87.5mg·kg-1 for sedge and oat, respectively at the 10% SP rate). Only modest quantities of NG removal were accounted for by abiotic processes such as soil sorption. Soil bacterial numbers remained relatively constant regardless of rate of SP application. Microbial activity in the plant rhizosphere was concluded to be the major contributor to NG solubilization and decomposition. Addition of composted biosolids to soil imparted a positive effect in NG decomposition and/or removal from soil. Additional study is needed to determine long-term decomposition of smokeless powder and subsequent NG reactions in soil

Treatment of simulated oil and gas production wastewater using Typha latifolia in a pilot-scale constructed Welland

During hydraulic fracturing (‘fracking’), large volumes of highpressure, chemically-treated water are pumped into subsurface strata to free trapped petroleum and natural gas. Chemicallyenriched water, along with brine and groundwater, collectively termed oil and gas production water (PW), are eventually recovered from the well. PW poses environmental and health risks; however, it can be reused if potentially hazardous constituents are removed. A two-stage pilot-scale constructed wetland containing cattail (Typha latifolia) was tested for treatment of synthetic PW. After 49 days, PW pH increased from 4.2 to 7.0, and electrical conductivity decreased from 22,100 to 3,300µS•cm-1. Typha shoots had bioconcentration factors for Pb ranging from 2.8 (Stage 1 of constructed wetland) to 8.0 (Stage 2). Transfer factors for Pb were 0.67 (Stage 1) and 1.37 (Stage 2). These results indicate that Typha may be effective for Pb removal from PWs. The present study may be of practical value to oil and gas production companies that plan to recycle or properly dispose of large quantities of oil and gas production wastewater

Treatment of simulated oil and gas production wastewater using Typha latifolia in a pilot-scale constructed wetland

During hydraulic fracturing (‘fracking’), large volumes of highpressure, chemically-treated water are pumped into subsurface strata to free trapped petroleum and natural gas. Chemicallyenriched water, along with brine and groundwater, collectively termed oil and gas production water (PW), are eventually recovered from the well. PW poses environmental and health risks; however, it can be reused if potentially hazardous constituents are removed. A two-stage pilot-scale constructed wetland containing cattail (Typha latifolia) was tested for treatment of synthetic PW. After 49 days, PW pH increased from 4.2 to 7.0, and electrical conductivity decreased from 22,100 to 3,300µS•cm-1. Typha shoots had bioconcentration factors for Pb ranging from 2.8 (Stage 1 of constructed wetland) to 8.0 (Stage 2). Transfer factors for Pb were 0.67 (Stage 1) and 1.37 (Stage 2). These results indicate that Typha may be effective for Pb removal from PWs. The present study may be of practical value to oil and gas production companies that plan to recycle or properly dispose of large quantities of oil and gas production wastewater

Plants and soil amendments for remediation of soil affected by synthetic oil and gas production wastewater

Oil and gas production water (PW) is brought to the surface when hydrocarbon reservoirs deep within geologic strata are extracted. Large volumes of PW present environmental challenges when released to the land surface due to high levels of salinity and potentially toxic elements. The effects of PW on soil chemical properties and plant response were investigated in both growth chamber and field studies. In the growth chamber, wheat (Triticum aestivum) and red clover (Trifolium repens) were grown in soil which was flooded with synthetic PW. The PW was enriched with several metals (Na, Cu, Cr, Pb) and had an acidic pH (2.5) and EC of 33,650 dSm-1. Soil amendments included food waste compost, composted biosolids, gypsum (CaSO4) and NPK 10-10-10 fertilizer. Metal concentrations in soil and plants were determined using flame atomic absorption spectrophotometry. The food waste compost provided for maximal uptake by clover of Cu, Cr and Pb compared to all other amendments. In several soil treatments both wheat and clover behaved as metal hyperaccumulators having high bioconcentration factors (BCF, ratio of metal concentrations of plant tissue to soil). Clover was the most efficient in accumulating Cu and Cr in shoots (BCF = 22.2 and 30.6, respectively). Greatest metal uptake in both plant species occurred in either the biosolids or compost treatment. In a field study, plots were flooded with synthetic PW and grown to corn (Zea mays) and a turf mixture (Kentucky bluegrass, Poa pratensis and perennial ryegrass, Lolium perenne). Both corn and turf accumulated substantial soil Cu and Pb. Corn experienced significant die-off; however, turf survived the PW application. Turf mixtures, clover and/or wheat may be suitable for phytoremediation of PW-affected soil. Addition of organic amendments to soil may enhance metal uptake by plants