Charles M. Reynolds

Influence of organic and inorganic soil amendments on plant growth in crude oil-contaminated soil

Abstract Phytoremediation can be a viable alternative to traditional, more costly remediation techniques. Three greenhouse studies were conducted to evaluate plant growth with different soil amendments in crude oil‐contaminated soil. Growth of alfalfa (Medicago sativa L., cultivar: Riley), bermudagrass (Cynodon dactylon L., cultivar: Common), crabgrass (Digitaria sanguinalis cultivar: Large), fescue (Lolium arundinaceum Schreb., cultivar: Kentucky 31), and ryegrass (Lolium multiflorum Lam., cultivar: Marshall) was determined in crude oil‐contaminated soil amended with either inorganic fertilizer, hardwood sawdust, papermill sludge, broiler litter or unamended (control). In the first study, the addition of broiler litter reduced seed germination for ryegrass, fescue, and alfalfa. In the second study, bermudagrass grown in broiler litteramended soil produced the most shoot biomass, bermudagrass produced the most root biomass, and crabgrass and bermudagrass produced the most root length. In the third study, soil amended with broiler litter resulted in the greatest reduction in gravimetric total petroleum hydrocarbon (TPH) levels across the six plant treatments following the 14‐wk study. Ryegrass produced more root biomass than any other species when grown in inorganic fertilizer‐ or hardwood sawdust + inorganic fertilizer‐amended soil. The studies demonstrated that soil amendments and plant species selection were important considerations for phytoremediation of crude oil‐contaminated soil.

Selecting Plants and Nitrogen Rates to Vegetate Crude-Oil–Contaminated Soil

Phytoremediation can be effective for remediating contaminated soils in situ and generally requires the addition of nitrogen (N) to increase plant growth. Our research objectives were to evaluate seedling emergence and survival of plant species and to determine the effects of N additions on plant growth in crude-oil–contaminated soil. From a preliminary survival study, three warm-season grasses—pearlmillet (Pennisetum glaucum [L.] R. Br.), sudangrass (Sorghum sudanense [Piper] Stapf [Piper]), and browntop millet (Brachiaria ramosa L.)—and one warm-season legume—jointvetch (Aeschynomene americana L.)—were chosen to determine the influence of the N application rate on plant growth in soil contaminated with weathered crude oil. Nitrogen was added based on total petroleum hydrocarbon-C:added N ratios (TPH-C:TN) ranging from 44:1 to 11:1. Plant species were grown for 7 wk. Root and shoot biomass were determined and root length and surface area were analyzed. Pearlmillet and sudangrass had higher shoot and root biomass when grown at a TPH-C:TN (inorganic) ratio of 11:1 and pearlmillet had higher root length and surface area when grown at 11:1 compared with the other species. By selecting appropriate plant species and determining optimum N application rates, increased plant root growth and an extended rhizosphere influence should lead to enhanced phytoremediation of crude-oil–contaminated soil.

Long-term changes in soil and plant metal concentrations in an acidic dredge disposal site receiving sewage sludge

A long-term experiment was conducted to determine the distribution of sludge-borne metals applied to a revegetated acidic dredge spoil disposal site. The initial soil was infertile and highly acidic (pH 2.4). Sewage sludge and lime were applied in 1974 at the rates of 100 and 23 mt ha−1, respectively, and tilled into the soil to a depth of 20 cm. In 1974 an adjacent site was also revegetated with topsoil and lime but without sludge. Soil and plants were sampled 2, 4 and 16 yr following seeding. After 16 yr the total and DTPA-extractable Cu, Zn, Cr, Pb, Ni and Cd decreased in soils to nearly the levels of the control soils. Concentrations of metals in plants also decreased. Decreases in tissue concentrations ranged from 40 to 70% for Cu, Cr, Pb, Ni and Cd and up to 90% for Zn. The results showed that a single 100 mt ha−1 application of sewage sludge containing high concentrations of metals was a cost-effective method for improving plant growing conditions on highly acidic soils.

Steady-state and frequency-domain lifetime measurements of an activated molecular imprinted polymer imprinted to dipicolinic acid.

We recently demonstrated the synthesis and fluorescence activity associated with an optical detector incorporating a molecular imprinted polymer (MIP). Steady-state and time-resolved (lifetime) fluorescence measurements were used to characterize the binding activity associated with MIP microparticles imprinted to dipicolinic acid (DPA). DPA is a unique biomarker associated with the sporulation phase of endospore-forming bacteria. Vinylic monomers were polymerized in a dimethylformamide solution containing DPA as a template. The resulting MIP was then pulverized and sorted into small microscale particles. Tests were conducted on replicate samples of biologically active cultures representing both vegetative stationary phase and sporulation phase of Bacillus subtilis in standard media. Samplers were adapted incorporating the MIP particles within a dialyzer cartridge (500 MW). The permeability of the dialyzer membrane permitted diffusion of lighter molecular weight constituents from microbial media effluents to enter the dialyzer chamber and come in contact with the MIP. Results showed dramatic (10-fold over background) steady-state fluorescence changes (as a function of excitation, emission and intensity) for samples associated with high endospore biomass (DPA), and a frequency-domain lifetime of 5.3 ns for the MIP–DPA complex.

Petroleum-Degrading Microbial Numbers in Rhizosphere and Non-Rhizosphere Crude Oil-Contaminated Soil

Phytoremediation can be a cost-effective and environmentally acceptable method to clean up crude oil-contaminated soils in situ. Our research objective was to determine the effects of nitrogen (N) additions and plant growth on the number of total hydrocarbon (TH)-, alkane-, and polycyclic aromatic hydrocarbon (PAH)-degrading microorganisms in weathered crude oil-contaminated soil. A warm-season grass, sudangrass (Sorghum sudanense (Piper) Stapf), was grown for 7 wk in soil with a total petroleum hydrocarbon (TPH) level of 16.6 g TPH/kg soil. Nitrogen was added based upon TPH-C:added total N (TPH-C:TN) ratios ranging from 44:1 to 11:1. Unvegetated and unamended controls were also evaluated. The TH-, alkane-, and PAH-degrading microbial numbers per gram of dry soil were enumerated from rhizosphere and non-rhizosphere soil for vegetated pots and non-rhizosphere soil populations were enumerated from non-vegetated pots. Total petroleum-degrading microbial numbers were also calculated for each pot. The TH-, alkane-, and PAH-degrading microbial numbers per gram of dry soil in the sudangrass rhizosphere were 3.4, 2.6, and 4.8 times larger, respectively, than those in non-rhizosphere soil across all N rates. The presence of sudangrass resulted in significantly more TH-degrading microorganisms per pot when grown in soil with a TPH-C:TN ratio of 11:1 as compared to the control. Increased plant root growth in a crude oil-contaminated soil and a concomitant increase in petroleum-degrading microbial numbers in the rhizosphere have the potential to enhance phytoremediation.

The Attenuation of Retroreflective Signatures on Surface Soils

Abstract Soil parameters such as water potential, temperature, organic matter ( om ), and particle size distribution influence biological activity and collectively define the state of soils, yet these properties are typically described through time-intensive, ground-based sampling efforts. To improve our understanding of soils through stand-off sensing techniques, Light Detection and Ranging was used to monitor the signature of retroreflective beads embedded in polymeric agents on four soils. Our goal was to generate probability density functions (PDFs) for stochastic predictions of the persistence of this signature through time. Our findings showed that the PDFs of the reflected signal between target and background soils became nearly indistinguishable after five months and that OM, nitrogen content, cation exchange capacity, and pH related to signature decline. This approach, while developed using polymer-bound retroreflectors, will serve as a framework where a signature-emitter is left in or on soil and differentially influenced by terrain, weather, and soil processes.

Removal of Exogenous Materials from the Outer Portion of Frozen Cores to Investigate the Ancient Biological Communities Harbored Inside

The cryosphere offers access to preserved organisms that persisted under past environmental conditions. In fact, these frozen materials could reflect conditions over vast time periods and investigation of biological materials harbored inside could provide insight of ancient environments. To appropriately analyze these ecosystems and extract meaningful biological information from frozen soils and ice, proper collection and processing of the frozen samples is necessary. This is especially critical for microbial and DNA analyses since the communities present may be so uniquely different from modern ones. Here, a protocol is presented to successfully collect and decontaminate frozen cores. Both the absence of the colonies used to dope the outer surface and exogenous DNA suggest that we successfully decontaminated the frozen cores and that the microorganisms detected were from the material, rather than contamination from drilling or processing the cores.

Benefits of Root-Microbial Processes for Treating Recalcitrant Organics: Field Studies in Korea

Options for treating organics-contaminated soils at U.S. overseas installations can be limited by cost, lack of supporting infrastructure, and availability of labor. Rhizosphere enhanced remediation can be an option for these sites. We conducted two replicated field demonstrations in the Republic of Korea. Factors evaluated were fertilizer and plants, each at two levels, in a factorial experiment. Vegetation was annual ryegrass (Lolium multiflorum) and fertilizer was 12-9-9, both were locally available. Spatial heterogeneity of initial TPH concentrations varied widely. After one season, using GCFID-measured TPH concentrations or using hopane-normalized TPH depletions to mental conditions. In this study, the purification-capability characteristics of a potted plant and its soil were examined using an experimental chamber of 300 liters. The plant was installed in the chamber and formaldehyde as a pollutant was injected into it. The characteristics were measured using a tin oxide gas sensor. The sensor is on the market and is widely used as a gas-leak detector. Its resistivity becomes lower as the concentration of atmospheric reducing gas becomes higher, and the output, which is the voltage of both ends of a load resistance, increases. The experiments were carried out using this chamber, which was placed in a room. The room was controlled by an air conditioner. Therefore, experimental conditioning parameters, for example climate and sunshine, could be kept at a constant. Golden pothos was adopted as the subject. Purification capability (Pa) was derived using the peak value and the fullwidth at half maximum of the sensor output characteristic. As for the results, it became obvious that Pa became larger when porous soil, for example ceramics and Japanese charcoal, were used in the pot. It is thought that the types of microorganisms inhabiting the soil influence the characteristics. And there was a tendency that Pa decreased when the plant was exposed intermittently to atmospheric formaldehyde. Pa also changes by the room temperature. It had a maximum value at about 22°C and increased slightly when the light intensity became higher. It is thought that the conditions of the soil and plant are very important to remove an atmospheric pollutant, especially in an indoor environment.