Repeated inoculation as a strategy for the remediation of low concentrations of phenanthrene in soil

Phenanthrene, a polycyclic aromatic hydrocarbon, becomes increasingly unavailable to microorganisms for degradation as it ages in soil. Consequently, many bioaugmentation efforts to remediate polycyclic aromatic hydrocarbons in soil have failed. We studied theeffect of repeatedly inoculating a soil with a phenanthrene-degrading Arthrobacter sp. on the mineralization kinetics of low concentrations of phenanthrene. After the first inoculation, the initial mineralization rate of 50 ng/g phenanthrene declined in a biphasicexponential pattern. By three hundred hours after inoculation, there was no difference in mineralization rates between the inoculated and uninoculated treatments even though a large fraction of the phenanthrene had not yet been mineralized. A second and third inoculation significantly increased the mineralization rate, suggesting that, though themineralization rate declined, phenanthrene remained bioavailable. Restirring the soil, without inoculation, did not produce similar increases in mineralization rates, suggesting absence of contact between cells and phenanthrene on a larger spatial scale (>mm) is not the cause of the mineralization decline. Bacteria inoculated into soil 280 hours beforethe phenanthrene was added could not maintain phenanthrene degradation activity. We suggest sorption lowered bioavailability of phenanthrene below an induction threshold concentration for metabolic activity of phenanthrene-degrading bacteria.     

Determination of rat oral bioavailability of soy-derived phytoestrogens using an automated on-column extraction procedure and electrospray tandem mass spectrometry

In recent years, consumption of herbal supplements as an alternative to pharmaceutical drug therapy has increased. For example, with the health claims labeling which describes the link between soy-protein and a reduced risk of coronary heart disease (CHD), the consumption of soy and soy-derived phytoestrogens has increased dramatically. That being said, the oral bioavailability of only a few soy phytoestrogens such as Daidzein and Genestein have been previously estimated. In this paper, we present the calculated percent of rat oral bioavailability of five soy-derived phytoestrogens (Genistein, Daidzein, Biochanin A, Coumestrol, and Zearalenone) in male Sprague-Dawley rats. The plasma quantitation required for the bioavailability calculation is performed by using a rapid on-line plasma extraction procedure for the quantitative analysis. To further speed up the analysis the rats were dosed using the 'n-in-one' (cassette) protocol. The rapid on-line extraction/quantitation methodology coupled to the cassette dosing analysis of phytoestrogens is the key point of this paper. The limit of quantitation (LOQ) for each compound was 1-1000 ng/ml with each plasma sample analysis taking less than 2 min. In general the percent oral bioavailability was determined to be between 11 and 28%.     

Prepared Bed Land Treatment of Soils Containing Diesel and Crude Oil Hydrocarbons

An ex situ, field-scale, prepared bed land treatment unit (LTU) was used to bio-remediate soils containing petroleum hydrocarbons. Two soils were treated in side-by-side units to compare performance: (1) a clayey silt containing crude oil hydrocarbons from releases 30 to 40 years ago and (2) a silty sand containing diesel fuel hydrocarbons from a leak about three years prior to the bioremediation. The effectiveness of the bioremediation in the LTU was evaluated over a period of 18 months. The results indicated that: (1) prepared bed bioremediation reduced the hydrocarbon concentration, mobility, and relative toxicity in the soil with the diesel fuel, and (2) chemical bioavailability appeared to limit bioremediation of the soil containing the crude oil hydrocarbons. Although the soils containing the crude oil hydrocarbons contained an average of 10,000?mg TPH/kg dry soil, these soils had limited hydrocarbon availability, nontoxic conditions, and low potential for chemical migration. For the soils containing the diesel fuel, active prepared bed bioremediation of about 15 weeks was adequate to reach an environmentally acceptable endpoint. At that time, there was little further TPH loss, no Microtox^TM toxicity, and limited hydrocarbon mobility.     

Arsenic in Agricultural Soils of a Historically Mined and Industrial Region of Southern Serbia and Northern Kosovo: Bioavailability and Uptake by Plants Species Zea mays L. and Solanum tuberosum L.

This article reports the results of a study focused on the presence and bioavailability of arsenic in agricultural soil in the mining and industrial regions of northern Kosovo and southern Serbia, as well as uptake and bioaccumulation of arsenic in two commonly cultivated plant species (Zea mays L. and Solanum tuberosum L.). This area was one of the most important mining districts in Europe. The collected soil samples were subjected to a modified BCR three-step sequential extraction procedure in order to investigate the chemical partitioning of arsenic in the soils. The general distribution of arsenic in various fractions was: exchangeable < reducible < oxidizable fractions. Highest concentrations of total arsenic in soil were found close to industrial facilities and tailing ponds. In addition, fluvisols were significantly more enriched with arsenic than soils at a distance from the river flows. The edible parts of the plant specimen showed different As contents, suggesting that these plant species have different propensities for the uptake and bioaccumulation of arsenic from soil.     

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.     

Quantification of total and bioavailable lysine in feed protein sources by a whole-cell green fluorescent protein growth-based <Emphasis Type="Italic">Escherichia coli</Emphasis> biosensor

Using a fluorescent whole-cell Escherichia coli biosensor previously developed in our laboratory, we determined total and bioavailable lysine in four feed ingredients (soybean, cottonseed, meat and bone meal, and sorghum) and three complete feeds (chick starter and finisher, and swine starter). The same feed sources were analyzed for total lysine by high performance liquid chromatography (HPLC) and bioavailable lysine by chick bioassay. No significant differences were found between bioavailable lysine estimates for soybean, cottonseed, meat and bone meal, chick starter and finisher, and swine starter obtained by the fluorescent E. coli biosensor and chick bioassay. Except for sorghum, the E. coli biosensor estimates for total lysine were highly comparable to those obtained by HPLC. Comparisons were also conducted between conventionally performed optical density-based and the newly developed fluorescence-based lysine assay. The lack of significant differences in data obtained for total and bioavailable lysine by both detection modes indicated reliance and accuracy of the fluorescent E. coli biosensor. Overall results suggest that the microbial assay based on green fluorescent protein fluorescence represents a promising alternative method for lysine quantification.     

An Overview of the Development,Status, and Application of Equilibrium Partitioning Sediment Benchmarks for PAH Mixtures

This article provides an overview of the development, theoretical basis, regulatory status, and application of the U.S. Environmental Protection Agency's (USEPA's) Equilibrium Partitioning Sediment Benchmarks (ESBs) for PAH mixtures. ESBs are compared to other sediment quality guidelines (SQGs) for PAHs. Data that examine the ability of the ESB approach to predict toxic effects to invertebrates are discussed. A USEPA draft methodology for the development of site-specific ESBs that takes into account the limited bioavailability of PAHs at certain sites is discussed. Research is presented that compares the ability of ESBs and site-specific ESBs to predict the toxicity of sediments collected from manufactured gas plants (MGPs). Site-specific ESBs that accounted for adsorption of PAHs onto black carbon were better predictors of the toxicity of sediments from MGP sites than ESBs that did not account for adsorption to black carbon.     

Microbe-aliphatic hydrocarbon interactions in soil: implications for biodegradation and bioremediation

Aliphatic hydrocarbons make up a substantial portion of organic contamination in the terrestrial environment. However, most studies have focussed on the fate and behaviour of aromatic contaminants in soil. Despite structural differences between aromatic and aliphatic hydrocarbons, both classes of contaminants are subject to physicochemical processes, which can affect the degree of loss, sequestration and interaction with soil microflora. Given the nature of hydrocarbon contamination of soils and the importance of bioremediation strategies, understanding the fate and behaviour of aliphatic hydrocarbons is imperative, particularly microbe-contaminant interactions. Biodegradation by microbes is the key removal process of hydrocarbons in soils, which is controlled by hydrocarbon physicochemistry, environmental conditions, bioavailability and the presence of catabolically active microbes. Therefore, the aims of this review are (i) to consider the physicochemical properties of aliphatic hydrocarbons and highlight mechanisms controlling their fate and behaviour in soil; (ii) to discuss the bioavailability and bioaccessibility of aliphatic hydrocarbons in soil, with particular attention being paid to biodegradation, and (iii) to briefly consider bioremediation techniques that may be applied to remove aliphatic hydrocarbons from soil.     

Evaluating the effects of gross nitrogen mineralization,immobilization, and nitrification on nitrogen fertilizer availability in soil experimentally contaminated with diesel

Sandy clay loam soil was contaminated with 5000 mg kg⁻¹ diesel, and amended with nitrogen (15.98 atom% ¹⁵N) at 0, 250, 500, and 1000 mg kg⁻¹ to determine gross rates of nitrogen transformations during diesel biodegradation at varying soil water potentials. The observed water potential values were −0.20, −0.47, −0.85, and −1.50 MPa in the 0, 250, 500, and 1000 mg kg⁻¹ nitrogen treatments respectively. Highest microbial respiration occurred in the lowest nitrogen treatment suggesting an inhibitory osmotic effect from higher rates of nitrogen application. Microbial respiration rates of 185, 169, 131, and 116 mg O₂ kg⁻¹ soil day⁻¹ were observed in the 250, 500, control and 1000 mg kg⁻¹ nitrogen treatments, respectively. Gross nitrification was inversely related to water potential with rates of 0.2, 0.04, and 0.004 mg N kg⁻¹ soil day⁻¹ in the 250, 500, and 1000 mg kg⁻¹ nitrogen treatments, respectively. Reduction in water potential did not inhibit gross nitrogen immobilization or mineralization, with respective immobilization rates of 2.2, 1.8, and 1.8 mg N kg⁻¹ soil day⁻¹, and mineralization rates of 0.5, 0.3, and 0.3 mg N kg⁻¹ soil day⁻¹ in the 1000, 500, and 250 mg kg⁻¹ nitrogen treatments, respectively. Based on nitrogen transformation rates, the duration of fertilizer contribution to the inorganic nitrogen pool was estimated at 0.9, 1.9, and 3.2 years in the 250, 500, and 1000 mg kg⁻¹ nitrogen treatments, respectively. The estimation was conservative as ammonium fixation, gross nitrogen immobilization, and nitrification were considered losses of fertilizer with only gross mineralization of organic nitrogen contributing to the most active portion of the nitrogen pool.     

不同有机肥对土壤镉锌生物有效性的影响

在南方典型稻田设置连续4年施用猪粪、鸡粪、稻草的定位试验,监测施用不同有机肥条件下土壤及水稻植株镉(Cd)、锌(Zn)含量的变化,研究有机肥对土壤Cd、Zn活性及其交互作用的影响.结果表明: 施用有机肥(猪粪、鸡粪、稻草)对土壤全Cd、有效态Cd含量及Cd活性皆无显著影响,但有增加土壤Cd全量的趋势,且显著增加土壤全Zn、有效态Zn含量及Zn活性.施用猪粪、鸡粪、稻草皆可降低稻米Cd含量,降Cd效果为猪粪>鸡粪>稻草,猪粪处理水稻稻米、茎、叶Cd含量分别比对照下降37.5%、44.0%、36.4%;鸡粪处理水稻米、茎、叶Cd含量分别比对照下降22.5%、33.8%、22.7%;而稻草处理水稻米Cd含量比对照下降7.5%,但茎、叶Cd含量比对照分别增加8.2%、22.7%;施用猪粪、鸡粪降低稻米Cd含量主要是降低了水稻植株对土壤Cd的富集,而施用稻草则主要是降低了水稻茎Cd向稻米的转运.施用有机肥还增加了水稻茎Zn含量,施用猪粪、鸡粪、稻草的水稻茎Zn含量比单施化肥分别增加53.4%、41.2%、13.9%,但对水稻稻米、叶Zn含量无显著影响.Zn、Cd在土壤、植株茎中皆表现出显著的拮抗作用,土壤及水稻茎Zn含量的增加显著抑制了水稻米、茎、叶对Cd的吸收积累,且随土壤有效态Zn/Cd含量比值的增加,Zn、Cd竞争土壤吸附不是抑制水稻吸收积累Cd的主控因子,而Zn、Cd竞争吸收才是影响水稻吸收积累Cd的主控因子.